-n [master]

[thirdparty/dhcp.git] / server / dhcpv6.c

/*
 * Copyright (C) 2006-2013 by Internet Systems Consortium, Inc. ("ISC")
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
 * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
 * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
 * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
 * OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
 * PERFORMANCE OF THIS SOFTWARE.
 */

#include "dhcpd.h"

#ifdef DHCPv6

/*
 * We use print_hex_1() to output DUID values. We could actually output 
 * the DUID with more information... MAC address if using type 1 or 3, 
 * and so on. However, RFC 3315 contains Grave Warnings against actually 
 * attempting to understand a DUID.
 */

/* 
 * TODO: gettext() or other method of localization for the messages
 *       for status codes (and probably for log formats eventually)
 * TODO: refactoring (simplify, simplify, simplify)
 * TODO: support multiple shared_networks on each interface (this 
 *       will allow the server to issue multiple IPv6 addresses to 
 *       a single interface)
 */

/*
 * DHCPv6 Reply workflow assist.  A Reply packet is built by various
 * different functions; this gives us one location where we keep state
 * regarding a reply.
 */
struct reply_state {
        /* root level persistent state */
        struct shared_network *shared;
        struct host_decl *host;
        struct subnet *subnet; /* Used to match fixed-addrs to subnet scopes. */
        struct option_state *opt_state;
        struct packet *packet;
        struct data_string client_id;

        /* IA level persistent state */
        unsigned ia_count;
        unsigned pd_count;
        unsigned client_resources;
        isc_boolean_t resources_included;
        isc_boolean_t static_lease;
        unsigned static_prefixes;
        struct ia_xx *ia;
        struct ia_xx *old_ia;
        struct option_state *reply_ia;
        struct data_string fixed;

        /* IAADDR/PREFIX level persistent state */
        struct iasubopt *lease;

        /*
         * "t1", "t2", preferred, and valid lifetimes records for calculating
         * t1 and t2 (min/max).
         */
        u_int32_t renew, rebind, prefer, valid;

        /* Client-requested valid and preferred lifetimes. */
        u_int32_t client_valid, client_prefer;

        /* Chosen values to transmit for valid and preferred lifetimes. */
        u_int32_t send_valid, send_prefer;

        /* Preferred prefix length (-1 is any). */
        int preflen;

        /* Index into the data field that has been consumed. */
        unsigned cursor;

        /* Space for the on commit statements for a fixed host */
        struct on_star on_star;

        union reply_buffer {
                unsigned char data[65536];
                struct dhcpv6_packet reply;
        } buf;
};

/* 
 * Prototypes local to this file.
 */
static int get_encapsulated_IA_state(struct option_state **enc_opt_state,
                                     struct data_string *enc_opt_data,
                                     struct packet *packet,
                                     struct option_cache *oc,
                                     int offset);
static void build_dhcpv6_reply(struct data_string *, struct packet *);
static isc_result_t shared_network_from_packet6(struct shared_network **shared,
                                                struct packet *packet);
static void seek_shared_host(struct host_decl **hp,
                             struct shared_network *shared);
static isc_boolean_t fixed_matches_shared(struct host_decl *host,
                                          struct shared_network *shared);
static isc_result_t reply_process_ia_na(struct reply_state *reply,
                                        struct option_cache *ia);
static isc_result_t reply_process_ia_ta(struct reply_state *reply,
                                        struct option_cache *ia);
static isc_result_t reply_process_addr(struct reply_state *reply,
                                       struct option_cache *addr);
static isc_boolean_t address_is_owned(struct reply_state *reply,
                                      struct iaddr *addr);
static isc_boolean_t temporary_is_available(struct reply_state *reply,
                                            struct iaddr *addr);
static isc_result_t find_client_temporaries(struct reply_state *reply);
static isc_result_t reply_process_try_addr(struct reply_state *reply,
                                           struct iaddr *addr);
static isc_result_t find_client_address(struct reply_state *reply);
static isc_result_t reply_process_is_addressed(struct reply_state *reply,
                                               struct binding_scope **scope,
                                               struct group *group);
static isc_result_t reply_process_send_addr(struct reply_state *reply,
                                            struct iaddr *addr);
static struct iasubopt *lease_compare(struct iasubopt *alpha,
                                      struct iasubopt *beta);
static isc_result_t reply_process_ia_pd(struct reply_state *reply,
                                        struct option_cache *ia_pd);
static isc_result_t reply_process_prefix(struct reply_state *reply,
                                         struct option_cache *pref);
static isc_boolean_t prefix_is_owned(struct reply_state *reply,
                                     struct iaddrcidrnet *pref);
static isc_result_t find_client_prefix(struct reply_state *reply);
static isc_result_t reply_process_try_prefix(struct reply_state *reply,
                                             struct iaddrcidrnet *pref);
static isc_result_t reply_process_is_prefixed(struct reply_state *reply,
                                              struct binding_scope **scope,
                                              struct group *group);
static isc_result_t reply_process_send_prefix(struct reply_state *reply,
                                              struct iaddrcidrnet *pref);
static struct iasubopt *prefix_compare(struct reply_state *reply,
                                       struct iasubopt *alpha,
                                       struct iasubopt *beta);
static int find_hosts_by_duid_chaddr(struct host_decl **host,
                                     const struct data_string *client_id);
/*
 * This function returns the time since DUID time start for the
 * given time_t value.
 */
static u_int32_t
duid_time(time_t when) {
        /*
         * This time is modulo 2^32.
         */
        while ((when - DUID_TIME_EPOCH) > 4294967295u) {
                /* use 2^31 to avoid spurious compiler warnings */
                when -= 2147483648u;
                when -= 2147483648u;
        }

        return when - DUID_TIME_EPOCH;
}


/* 
 * Server DUID.
 *
 * This must remain the same for the lifetime of this server, because
 * clients return the server DUID that we sent them in Request packets.
 *
 * We pick the server DUID like this:
 *
 * 1. Check dhcpd.conf - any value the administrator has configured 
 *    overrides any possible values.
 * 2. Check the leases.txt - we want to use the previous value if 
 *    possible.
 * 3. Check if dhcpd.conf specifies a type of server DUID to use,
 *    and generate that type.
 * 4. Generate a type 1 (time + hardware address) DUID.
 */
static struct data_string server_duid;

/*
 * Check if the server_duid has been set.
 */
isc_boolean_t
server_duid_isset(void) {
        return (server_duid.data != NULL);
}

/*
 * Return the server_duid.
 */
void
copy_server_duid(struct data_string *ds, const char *file, int line) {
        data_string_copy(ds, &server_duid, file, line);
}

/*
 * Set the server DUID to a specified value. This is used when
 * the server DUID is stored in persistent memory (basically the
 * leases.txt file).
 */
void
set_server_duid(struct data_string *new_duid) {
        /* INSIST(new_duid != NULL); */
        /* INSIST(new_duid->data != NULL); */

        if (server_duid_isset()) {
                data_string_forget(&server_duid, MDL);
        }
        data_string_copy(&server_duid, new_duid, MDL);
}


/*
 * Set the server DUID based on the D6O_SERVERID option. This handles
 * the case where the administrator explicitly put it in the dhcpd.conf 
 * file.
 */
isc_result_t
set_server_duid_from_option(void) {
        struct option_state *opt_state;
        struct option_cache *oc;
        struct data_string option_duid;
        isc_result_t ret_val;

        opt_state = NULL;
        if (!option_state_allocate(&opt_state, MDL)) {
                log_fatal("No memory for server DUID.");
        }

        execute_statements_in_scope(NULL, NULL, NULL, NULL, NULL,
                                    opt_state, &global_scope, root_group,
                                    NULL, NULL);

        oc = lookup_option(&dhcpv6_universe, opt_state, D6O_SERVERID);
        if (oc == NULL) {
                ret_val = ISC_R_NOTFOUND;
        } else {
                memset(&option_duid, 0, sizeof(option_duid));
                if (!evaluate_option_cache(&option_duid, NULL, NULL, NULL,
                                           opt_state, NULL, &global_scope,
                                           oc, MDL)) {
                        ret_val = ISC_R_UNEXPECTED;
                } else {
                        set_server_duid(&option_duid);
                        data_string_forget(&option_duid, MDL);
                        ret_val = ISC_R_SUCCESS;
                }
        }

        option_state_dereference(&opt_state, MDL);

        return ret_val;
}

/*
 * DUID layout, as defined in RFC 3315, section 9.
 * 
 * We support type 1 (hardware address plus time) and type 3 (hardware
 * address).
 *
 * We can support type 2 for specific vendors in the future, if they 
 * publish the specification. And of course there may be additional
 * types later.
 */
static int server_duid_type = DUID_LLT;

/* 
 * Set the DUID type.
 */
void
set_server_duid_type(int type) {
        server_duid_type = type;
}

/*
 * Generate a new server DUID. This is done if there was no DUID in 
 * the leases.txt or in the dhcpd.conf file.
 */
isc_result_t
generate_new_server_duid(void) {
        struct interface_info *p;
        u_int32_t time_val;
        struct data_string generated_duid;

        /*
         * Verify we have a type that we support.
         */
        if ((server_duid_type != DUID_LL) && (server_duid_type != DUID_LLT)) {
                log_error("Invalid DUID type %d specified, "
                          "only LL and LLT types supported", server_duid_type);
                return DHCP_R_INVALIDARG;
        }

        /*
         * Find an interface with a hardware address.
         * Any will do. :)
         */
        for (p = interfaces; p != NULL; p = p->next) {
                if (p->hw_address.hlen > 0) {
                        break;
                }
        }
        if (p == NULL) {
                return ISC_R_UNEXPECTED;
        }

        /*
         * Build our DUID.
         */
        memset(&generated_duid, 0, sizeof(generated_duid));
        if (server_duid_type == DUID_LLT) {
                time_val = duid_time(time(NULL));
                generated_duid.len = 8 + p->hw_address.hlen - 1;
                if (!buffer_allocate(&generated_duid.buffer,
                                     generated_duid.len, MDL)) {
                        log_fatal("No memory for server DUID.");
                }
                generated_duid.data = generated_duid.buffer->data;
                putUShort(generated_duid.buffer->data, DUID_LLT);
                putUShort(generated_duid.buffer->data + 2,
                          p->hw_address.hbuf[0]);
                putULong(generated_duid.buffer->data + 4, time_val);
                memcpy(generated_duid.buffer->data + 8,
                       p->hw_address.hbuf+1, p->hw_address.hlen-1);
        } else if (server_duid_type == DUID_LL) {
                generated_duid.len = 4 + p->hw_address.hlen - 1;
                if (!buffer_allocate(&generated_duid.buffer,
                                     generated_duid.len, MDL)) {
                        log_fatal("No memory for server DUID.");
                }
                generated_duid.data = generated_duid.buffer->data;
                putUShort(generated_duid.buffer->data, DUID_LL);
                putUShort(generated_duid.buffer->data + 2,
                          p->hw_address.hbuf[0]);
                memcpy(generated_duid.buffer->data + 4,
                       p->hw_address.hbuf+1, p->hw_address.hlen-1);
        } else {
                log_fatal("Unsupported server DUID type %d.", server_duid_type);
        }

        set_server_duid(&generated_duid);
        data_string_forget(&generated_duid, MDL);

        return ISC_R_SUCCESS;
}

/*
 * Get the client identifier from the packet.
 */
isc_result_t
get_client_id(struct packet *packet, struct data_string *client_id) {
        struct option_cache *oc;

        /*
         * Verify our client_id structure is empty.
         */
        if ((client_id->data != NULL) || (client_id->len != 0)) {
                return DHCP_R_INVALIDARG;
        }

        oc = lookup_option(&dhcpv6_universe, packet->options, D6O_CLIENTID);
        if (oc == NULL) {
                return ISC_R_NOTFOUND;
        }

        if (!evaluate_option_cache(client_id, packet, NULL, NULL,
                                   packet->options, NULL,
                                   &global_scope, oc, MDL)) {
                return ISC_R_FAILURE;
        }

        return ISC_R_SUCCESS;
}

/*
 * Message validation, defined in RFC 3315, sections 15.2, 15.5, 15.7:
 *
 *    Servers MUST discard any Solicit messages that do not include a
 *    Client Identifier option or that do include a Server Identifier
 *    option.
 */
int
valid_client_msg(struct packet *packet, struct data_string *client_id) {
        int ret_val;
        struct option_cache *oc;
        struct data_string data;

        ret_val = 0;
        memset(client_id, 0, sizeof(*client_id));
        memset(&data, 0, sizeof(data));

        switch (get_client_id(packet, client_id)) {
                case ISC_R_SUCCESS:
                        break;
                case ISC_R_NOTFOUND:
                        log_debug("Discarding %s from %s; "
                                  "client identifier missing",
                                  dhcpv6_type_names[packet->dhcpv6_msg_type],
                                  piaddr(packet->client_addr));
                        goto exit;
                default:
                        log_error("Error processing %s from %s; "
                                  "unable to evaluate Client Identifier",
                                  dhcpv6_type_names[packet->dhcpv6_msg_type],
                                  piaddr(packet->client_addr));
                        goto exit;
        }

        /*
         * Required by RFC 3315, section 15.
         */
        if (packet->unicast) {
                log_debug("Discarding %s from %s; packet sent unicast "
                          "(CLIENTID %s)",
                          dhcpv6_type_names[packet->dhcpv6_msg_type],
                          piaddr(packet->client_addr),
                          print_hex_1(client_id->len, client_id->data, 60));
                goto exit;
        }


        oc = lookup_option(&dhcpv6_universe, packet->options, D6O_SERVERID);
        if (oc != NULL) {
                if (evaluate_option_cache(&data, packet, NULL, NULL,
                                          packet->options, NULL,
                                          &global_scope, oc, MDL)) {
                        log_debug("Discarding %s from %s; "
                                  "server identifier found "
                                  "(CLIENTID %s, SERVERID %s)",
                                  dhcpv6_type_names[packet->dhcpv6_msg_type],
                                  piaddr(packet->client_addr),
                                  print_hex_1(client_id->len,
                                              client_id->data, 60),
                                  print_hex_2(data.len,
                                              data.data, 60));
                } else {
                        log_debug("Discarding %s from %s; "
                                  "server identifier found "
                                  "(CLIENTID %s)",
                                  dhcpv6_type_names[packet->dhcpv6_msg_type],
                                  print_hex_1(client_id->len,
                                              client_id->data, 60),
                                  piaddr(packet->client_addr));
                }
                goto exit;
        }

        /* looks good */
        ret_val = 1;

exit:
        if (data.len > 0) {
                data_string_forget(&data, MDL);
        }
        if (!ret_val) {
                if (client_id->len > 0) {
                        data_string_forget(client_id, MDL);
                }
        }
        return ret_val;
}

/*
 * Response validation, defined in RFC 3315, sections 15.4, 15.6, 15.8, 
 * 15.9 (slightly different wording, but same meaning):
 *
 *   Servers MUST discard any received Request message that meet any of
 *   the following conditions:
 *
 *   -  the message does not include a Server Identifier option.
 *   -  the contents of the Server Identifier option do not match the
 *      server's DUID.
 *   -  the message does not include a Client Identifier option.
 */
int
valid_client_resp(struct packet *packet,
                  struct data_string *client_id,
                  struct data_string *server_id)
{
        int ret_val;
        struct option_cache *oc;

        /* INSIST((duid.data != NULL) && (duid.len > 0)); */

        ret_val = 0;
        memset(client_id, 0, sizeof(*client_id));
        memset(server_id, 0, sizeof(*server_id));

        switch (get_client_id(packet, client_id)) {
                case ISC_R_SUCCESS:
                        break;
                case ISC_R_NOTFOUND:
                        log_debug("Discarding %s from %s; "
                                  "client identifier missing",
                                  dhcpv6_type_names[packet->dhcpv6_msg_type],
                                  piaddr(packet->client_addr));
                        goto exit;
                default:
                        log_error("Error processing %s from %s; "
                                  "unable to evaluate Client Identifier",
                                  dhcpv6_type_names[packet->dhcpv6_msg_type],
                                  piaddr(packet->client_addr));
                        goto exit;
        }

        oc = lookup_option(&dhcpv6_universe, packet->options, D6O_SERVERID);
        if (oc == NULL) {
                log_debug("Discarding %s from %s: "
                          "server identifier missing (CLIENTID %s)",
                          dhcpv6_type_names[packet->dhcpv6_msg_type],
                          piaddr(packet->client_addr),
                          print_hex_1(client_id->len, client_id->data, 60));
                goto exit;
        }
        if (!evaluate_option_cache(server_id, packet, NULL, NULL,
                                   packet->options, NULL,
                                   &global_scope, oc, MDL)) {
                log_error("Error processing %s from %s; "
                          "unable to evaluate Server Identifier (CLIENTID %s)",
                          dhcpv6_type_names[packet->dhcpv6_msg_type],
                          piaddr(packet->client_addr),
                          print_hex_1(client_id->len, client_id->data, 60));
                goto exit;
        }
        if ((server_duid.len != server_id->len) ||
            (memcmp(server_duid.data, server_id->data, server_duid.len) != 0)) {
                log_debug("Discarding %s from %s; "
                          "not our server identifier "
                          "(CLIENTID %s, SERVERID %s, server DUID %s)",
                          dhcpv6_type_names[packet->dhcpv6_msg_type],
                          piaddr(packet->client_addr),
                          print_hex_1(client_id->len, client_id->data, 60),
                          print_hex_2(server_id->len, server_id->data, 60),
                          print_hex_3(server_duid.len, server_duid.data, 60));
                goto exit;
        }

        /* looks good */
        ret_val = 1;

exit:
        if (!ret_val) {
                if (server_id->len > 0) {
                        data_string_forget(server_id, MDL);
                }
                if (client_id->len > 0) {
                        data_string_forget(client_id, MDL);
                }
        }
        return ret_val;
}

/*
 * Information request validation, defined in RFC 3315, section 15.12:
 *
 *   Servers MUST discard any received Information-request message that
 *   meets any of the following conditions:
 *
 *   -  The message includes a Server Identifier option and the DUID in
 *      the option does not match the server's DUID.
 *
 *   -  The message includes an IA option.
 */
int
valid_client_info_req(struct packet *packet, struct data_string *server_id) {
        int ret_val;
        struct option_cache *oc;
        struct data_string client_id;
        char client_id_str[80]; /* print_hex_1() uses maximum 60 characters,
                                   plus a few more for extra information */

        ret_val = 0;
        memset(server_id, 0, sizeof(*server_id));
        memset(&client_id, 0, sizeof(client_id));

        /*
         * Make a string that we can print out to give more 
         * information about the client if we need to.
         *
         * By RFC 3315, Section 18.1.5 clients SHOULD have a 
         * client-id on an Information-request packet, but it 
         * is not strictly necessary.
         */
        if (get_client_id(packet, &client_id) == ISC_R_SUCCESS) {
                snprintf(client_id_str, sizeof(client_id_str), " (CLIENTID %s)",
                         print_hex_1(client_id.len, client_id.data, 60));
                data_string_forget(&client_id, MDL);
        } else {
                client_id_str[0] = '\0';
        }

        /*
         * Required by RFC 3315, section 15.
         */
        if (packet->unicast) {
                log_debug("Discarding %s from %s; packet sent unicast%s",
                          dhcpv6_type_names[packet->dhcpv6_msg_type],
                          piaddr(packet->client_addr), client_id_str);
                goto exit;
        }

        oc = lookup_option(&dhcpv6_universe, packet->options, D6O_IA_NA);
        if (oc != NULL) {
                log_debug("Discarding %s from %s; "
                          "IA_NA option present%s",
                          dhcpv6_type_names[packet->dhcpv6_msg_type],
                          piaddr(packet->client_addr), client_id_str);
                goto exit;
        }
        oc = lookup_option(&dhcpv6_universe, packet->options, D6O_IA_TA);
        if (oc != NULL) {
                log_debug("Discarding %s from %s; "
                          "IA_TA option present%s",
                          dhcpv6_type_names[packet->dhcpv6_msg_type],
                          piaddr(packet->client_addr), client_id_str);
                goto exit;
        }
        oc = lookup_option(&dhcpv6_universe, packet->options, D6O_IA_PD);
        if (oc != NULL) {
                log_debug("Discarding %s from %s; "
                          "IA_PD option present%s",
                          dhcpv6_type_names[packet->dhcpv6_msg_type],
                          piaddr(packet->client_addr), client_id_str);
                goto exit;
        }

        oc = lookup_option(&dhcpv6_universe, packet->options, D6O_SERVERID);
        if (oc != NULL) {
                if (!evaluate_option_cache(server_id, packet, NULL, NULL,
                                           packet->options, NULL,
                                           &global_scope, oc, MDL)) {
                        log_error("Error processing %s from %s; "
                                  "unable to evaluate Server Identifier%s",
                                  dhcpv6_type_names[packet->dhcpv6_msg_type],
                                  piaddr(packet->client_addr), client_id_str);
                        goto exit;
                }
                if ((server_duid.len != server_id->len) ||
                    (memcmp(server_duid.data, server_id->data,
                            server_duid.len) != 0)) {
                        log_debug("Discarding %s from %s; "
                                  "not our server identifier "
                                  "(SERVERID %s, server DUID %s)%s",
                                  dhcpv6_type_names[packet->dhcpv6_msg_type],
                                  piaddr(packet->client_addr),
                                  print_hex_1(server_id->len,
                                              server_id->data, 60),
                                  print_hex_2(server_duid.len,
                                              server_duid.data, 60),
                                  client_id_str);
                        goto exit;
                }
        }

        /* looks good */
        ret_val = 1;

exit:
        if (!ret_val) {
                if (server_id->len > 0) {
                        data_string_forget(server_id, MDL);
                }
        }
        return ret_val;
}

/* 
 * Options that we want to send, in addition to what was requested
 * via the ORO.
 */
static const int required_opts[] = {
        D6O_CLIENTID,
        D6O_SERVERID,
        D6O_STATUS_CODE,
        D6O_PREFERENCE,
        0
};
static const int required_opts_NAA[] = {
        D6O_CLIENTID,
        D6O_SERVERID,
        D6O_STATUS_CODE,
        0
};
static const int required_opts_solicit[] = {
        D6O_CLIENTID,
        D6O_SERVERID,
        D6O_IA_NA,
        D6O_IA_TA,
        D6O_IA_PD,
        D6O_RAPID_COMMIT,
        D6O_STATUS_CODE,
        D6O_RECONF_ACCEPT,
        D6O_PREFERENCE,
        0
};
static const int required_opts_agent[] = {
        D6O_INTERFACE_ID,
        D6O_RELAY_MSG,
        0
};
static const int required_opts_IA[] = {
        D6O_IAADDR,
        D6O_STATUS_CODE,
        0
};
static const int required_opts_IA_PD[] = {
        D6O_IAPREFIX,
        D6O_STATUS_CODE,
        0
};
static const int required_opts_STATUS_CODE[] = {
        D6O_STATUS_CODE,
        0
};

/*
 * Extracts from packet contents an IA_* option, storing the IA structure
 * in its entirety in enc_opt_data, and storing any decoded DHCPv6 options
 * in enc_opt_state for later lookup and evaluation.  The 'offset' indicates
 * where in the IA_* the DHCPv6 options commence.
 */
static int
get_encapsulated_IA_state(struct option_state **enc_opt_state,
                          struct data_string *enc_opt_data,
                          struct packet *packet,
                          struct option_cache *oc,
                          int offset)
{
        /* 
         * Get the raw data for the encapsulated options.
         */
        memset(enc_opt_data, 0, sizeof(*enc_opt_data));
        if (!evaluate_option_cache(enc_opt_data, packet,
                                   NULL, NULL, packet->options, NULL,
                                   &global_scope, oc, MDL)) {
                log_error("get_encapsulated_IA_state: "
                          "error evaluating raw option.");
                return 0;
        }
        if (enc_opt_data->len < offset) {
                log_error("get_encapsulated_IA_state: raw option too small.");
                data_string_forget(enc_opt_data, MDL);
                return 0;
        }

        /*
         * Now create the option state structure, and pass it to the 
         * function that parses options.
         */
        *enc_opt_state = NULL;
        if (!option_state_allocate(enc_opt_state, MDL)) {
                log_error("get_encapsulated_IA_state: no memory for options.");
                data_string_forget(enc_opt_data, MDL);
                return 0;
        }
        if (!parse_option_buffer(*enc_opt_state,
                                 enc_opt_data->data + offset, 
                                 enc_opt_data->len - offset,
                                 &dhcpv6_universe)) {
                log_error("get_encapsulated_IA_state: error parsing options.");
                option_state_dereference(enc_opt_state, MDL);
                data_string_forget(enc_opt_data, MDL);
                return 0;
        }

        return 1;
}

static int
set_status_code(u_int16_t status_code, const char *status_message,
                struct option_state *opt_state)
{
        struct data_string d;
        int ret_val;

        memset(&d, 0, sizeof(d));
        d.len = sizeof(status_code) + strlen(status_message);
        if (!buffer_allocate(&d.buffer, d.len, MDL)) {
                log_fatal("set_status_code: no memory for status code.");
        }
        d.data = d.buffer->data;
        putUShort(d.buffer->data, status_code);
        memcpy(d.buffer->data + sizeof(status_code), 
               status_message, d.len - sizeof(status_code));
        if (!save_option_buffer(&dhcpv6_universe, opt_state, 
                                d.buffer, (unsigned char *)d.data, d.len, 
                                D6O_STATUS_CODE, 0)) {
                log_error("set_status_code: error saving status code.");
                ret_val = 0;
        } else {
                ret_val = 1;
        }
        data_string_forget(&d, MDL);
        return ret_val;
}

/*
 * We have a set of operations we do to set up the reply packet, which
 * is the same for many message types.
 */
static int
start_reply(struct packet *packet,
            const struct data_string *client_id, 
            const struct data_string *server_id,
            struct option_state **opt_state,
            struct dhcpv6_packet *reply)
{
        struct option_cache *oc;
        const unsigned char *server_id_data;
        int server_id_len;

        /*
         * Build our option state for reply.
         */
        *opt_state = NULL;
        if (!option_state_allocate(opt_state, MDL)) {
                log_error("start_reply: no memory for option_state.");
                return 0;
        }
        execute_statements_in_scope(NULL, packet, NULL, NULL,
                                    packet->options, *opt_state,
                                    &global_scope, root_group, NULL, NULL);

        /*
         * A small bit of special handling for Solicit messages.
         *
         * We could move the logic into a flag, but for now just check
         * explicitly.
         */
        if (packet->dhcpv6_msg_type == DHCPV6_SOLICIT) {
                reply->msg_type = DHCPV6_ADVERTISE;

                /*
                 * If:
                 * - this message type supports rapid commit (Solicit), and
                 * - the server is configured to supply a rapid commit, and
                 * - the client requests a rapid commit,
                 * Then we add a rapid commit option, and send Reply (instead
                 * of an Advertise).
                 */
                oc = lookup_option(&dhcpv6_universe,
                                   *opt_state, D6O_RAPID_COMMIT);
                if (oc != NULL) {
                        oc = lookup_option(&dhcpv6_universe,
                                           packet->options, D6O_RAPID_COMMIT);
                        if (oc != NULL) {
                                /* Rapid-commit in action. */
                                reply->msg_type = DHCPV6_REPLY;
                        } else {
                                /* Don't want a rapid-commit in advertise. */
                                delete_option(&dhcpv6_universe,
                                              *opt_state, D6O_RAPID_COMMIT);
                        }
                }
        } else {
                reply->msg_type = DHCPV6_REPLY;
                /* Delete the rapid-commit from the sent options. */
                oc = lookup_option(&dhcpv6_universe,
                                   *opt_state, D6O_RAPID_COMMIT);
                if (oc != NULL) {
                        delete_option(&dhcpv6_universe,
                                      *opt_state, D6O_RAPID_COMMIT);
                }
        }

        /* 
         * Use the client's transaction identifier for the reply.
         */
        memcpy(reply->transaction_id, packet->dhcpv6_transaction_id, 
               sizeof(reply->transaction_id));

        /* 
         * RFC 3315, section 18.2 says we need server identifier and
         * client identifier.
         *
         * If the server ID is defined via the configuration file, then
         * it will already be present in the option state at this point, 
         * so we don't need to set it.
         *
         * If we have a server ID passed in from the caller, 
         * use that, otherwise use the global DUID.
         */
        oc = lookup_option(&dhcpv6_universe, *opt_state, D6O_SERVERID);
        if (oc == NULL) {
                if (server_id == NULL) {
                        server_id_data = server_duid.data;
                        server_id_len = server_duid.len;
                } else {
                        server_id_data = server_id->data;
                        server_id_len = server_id->len;
                }
                if (!save_option_buffer(&dhcpv6_universe, *opt_state, 
                                        NULL, (unsigned char *)server_id_data,
                                        server_id_len, D6O_SERVERID, 0)) {
                                log_error("start_reply: "
                                          "error saving server identifier.");
                                return 0;
                }
        }

        if (client_id->buffer != NULL) {
                if (!save_option_buffer(&dhcpv6_universe, *opt_state, 
                                        client_id->buffer, 
                                        (unsigned char *)client_id->data, 
                                        client_id->len, 
                                        D6O_CLIENTID, 0)) {
                        log_error("start_reply: error saving "
                                  "client identifier.");
                        return 0;
                }
        }

        /*
         * If the client accepts reconfiguration, let it know that we
         * will send them.
         *
         * Note: we don't actually do this yet, but DOCSIS requires we
         *       claim to.
         */
        oc = lookup_option(&dhcpv6_universe, packet->options,
                           D6O_RECONF_ACCEPT);
        if (oc != NULL) {
                if (!save_option_buffer(&dhcpv6_universe, *opt_state,
                                        NULL, (unsigned char *)"", 0, 
                                        D6O_RECONF_ACCEPT, 0)) {
                        log_error("start_reply: "
                                  "error saving RECONF_ACCEPT option.");
                        option_state_dereference(opt_state, MDL);
                        return 0;
                }
        }

        return 1;
}

/*
 * Try to get the IPv6 address the client asked for from the
 * pool.
 *
 * addr is the result (should be a pointer to NULL on entry)
 * pool is the pool to search in
 * requested_addr is the address the client wants
 */
static isc_result_t
try_client_v6_address(struct iasubopt **addr,
                      struct ipv6_pool *pool,
                      const struct data_string *requested_addr)
{
        struct in6_addr tmp_addr;
        isc_result_t result;

        if (requested_addr->len < sizeof(tmp_addr)) {
                return DHCP_R_INVALIDARG;
        }
        memcpy(&tmp_addr, requested_addr->data, sizeof(tmp_addr));
        if (IN6_IS_ADDR_UNSPECIFIED(&tmp_addr)) {
                return ISC_R_FAILURE;
        }

        /*
         * The address is not covered by this (or possibly any) dynamic
         * range.
         */
        if (!ipv6_in_pool(&tmp_addr, pool)) {
                return ISC_R_ADDRNOTAVAIL;
        }

        if (lease6_exists(pool, &tmp_addr)) {
                return ISC_R_ADDRINUSE;
        }

        result = iasubopt_allocate(addr, MDL);
        if (result != ISC_R_SUCCESS) {
                return result;
        }
        (*addr)->addr = tmp_addr;
        (*addr)->plen = 0;

        /* Default is soft binding for 2 minutes. */
        result = add_lease6(pool, *addr, cur_time + 120);
        if (result != ISC_R_SUCCESS) {
                iasubopt_dereference(addr, MDL);
        }
        return result;
}

/*
 * Get an IPv6 address for the client.
 *
 * addr is the result (should be a pointer to NULL on entry)
 * packet is the information about the packet from the client
 * requested_iaaddr is a hint from the client
 * client_id is the DUID for the client
 */
static isc_result_t 
pick_v6_address(struct iasubopt **addr, struct shared_network *shared_network,
                const struct data_string *client_id)
{
        struct ipv6_pool *p;
        int i;
        int start_pool;
        unsigned int attempts;
        char tmp_buf[INET6_ADDRSTRLEN];

        /*
         * No address pools, we're done.
         */
        if (shared_network->ipv6_pools == NULL) {
                log_debug("Unable to pick client address: "
                          "no IPv6 pools on this shared network");
                return ISC_R_NORESOURCES;
        }
        for (i = 0;; i++) {
                p = shared_network->ipv6_pools[i];
                if (p == NULL) {
                        log_debug("Unable to pick client address: "
                                  "no IPv6 address pools "
                                  "on this shared network");
                        return ISC_R_NORESOURCES;
                }
                if (p->pool_type == D6O_IA_NA) {
                        break;
                }
        }

        /*
         * Otherwise try to get a lease from the first subnet possible.
         *
         * We start looking at the last pool we allocated from, unless
         * it had a collision trying to allocate an address. This will
         * tend to move us into less-filled pools.
         */
        start_pool = shared_network->last_ipv6_pool;
        i = start_pool;
        do {

                p = shared_network->ipv6_pools[i];
                if ((p->pool_type == D6O_IA_NA) &&
                    (create_lease6(p, addr, &attempts, client_id,
                                   cur_time + 120) == ISC_R_SUCCESS)) {
                        /*
                         * Record the pool used (or next one if there 
                         * was a collision).
                         */
                        if (attempts > 1) {
                                i++;
                                if (shared_network->ipv6_pools[i] == NULL) {
                                        i = 0;
                                }
                        }
                        shared_network->last_ipv6_pool = i;

                        log_debug("Picking pool address %s",
                                  inet_ntop(AF_INET6, &((*addr)->addr),
                                            tmp_buf, sizeof(tmp_buf)));
                        return ISC_R_SUCCESS;
                }

                i++;
                if (shared_network->ipv6_pools[i] == NULL) {
                        i = 0;
                }
        } while (i != start_pool);

        /*
         * If we failed to pick an IPv6 address from any of the subnets.
         * Presumably that means we have no addresses for the client.
         */
        log_debug("Unable to pick client address: no addresses available");
        return ISC_R_NORESOURCES;
}

/*
 * Try to get the IPv6 prefix the client asked for from the
 * prefix pool.
 *
 * pref is the result (should be a pointer to NULL on entry)
 * pool is the prefix pool to search in
 * requested_pref is the address the client wants
 */
static isc_result_t
try_client_v6_prefix(struct iasubopt **pref,
                     struct ipv6_pool *pool,
                     const struct data_string *requested_pref)
{
        u_int8_t tmp_plen;
        struct in6_addr tmp_pref;
        struct iaddr ia;
        isc_result_t result;

        if (requested_pref->len < sizeof(tmp_plen) + sizeof(tmp_pref)) {
                return DHCP_R_INVALIDARG;
        }
        tmp_plen = (int) requested_pref->data[0];
        if ((tmp_plen < 3) || (tmp_plen > 128) ||
            ((int)tmp_plen != pool->units)) {
                return ISC_R_FAILURE;
        }
        memcpy(&tmp_pref, requested_pref->data + 1, sizeof(tmp_pref));
        if (IN6_IS_ADDR_UNSPECIFIED(&tmp_pref)) {
                return ISC_R_FAILURE;
        }
        ia.len = 16;
        memcpy(&ia.iabuf, &tmp_pref, 16);
        if (!is_cidr_mask_valid(&ia, (int) tmp_plen)) {
                return ISC_R_FAILURE;
        }

        if (!ipv6_in_pool(&tmp_pref, pool)) {
                return ISC_R_ADDRNOTAVAIL;
        }

        if (prefix6_exists(pool, &tmp_pref, tmp_plen)) {
                return ISC_R_ADDRINUSE;
        }

        result = iasubopt_allocate(pref, MDL);
        if (result != ISC_R_SUCCESS) {
                return result;
        }
        (*pref)->addr = tmp_pref;
        (*pref)->plen = tmp_plen;

        /* Default is soft binding for 2 minutes. */
        result = add_lease6(pool, *pref, cur_time + 120);
        if (result != ISC_R_SUCCESS) {
                iasubopt_dereference(pref, MDL);
        }
        return result;
}

/*
 * Get an IPv6 prefix for the client.
 *
 * pref is the result (should be a pointer to NULL on entry)
 * packet is the information about the packet from the client
 * requested_iaprefix is a hint from the client
 * plen is -1 or the requested prefix length
 * client_id is the DUID for the client
 */
static isc_result_t 
pick_v6_prefix(struct iasubopt **pref, int plen,
               struct shared_network *shared_network,
               const struct data_string *client_id)
{
        struct ipv6_pool *p;
        int i;
        unsigned int attempts;
        char tmp_buf[INET6_ADDRSTRLEN];

        /*
         * No prefix pools, we're done.
         */
        if (shared_network->ipv6_pools == NULL) {
                log_debug("Unable to pick client prefix: "
                          "no IPv6 pools on this shared network");
                return ISC_R_NORESOURCES;
        }
        for (i = 0;; i++) {
                p = shared_network->ipv6_pools[i];
                if (p == NULL) {
                        log_debug("Unable to pick client prefix: "
                                  "no IPv6 prefix pools "
                                  "on this shared network");
                        return ISC_R_NORESOURCES;
                }
                if (p->pool_type == D6O_IA_PD) {
                        break;
                }
        }

        /*
         * Otherwise try to get a prefix.
         */
        for (i = 0;; i++) {
                p = shared_network->ipv6_pools[i];
                if (p == NULL) {
                        break;
                }
                if (p->pool_type != D6O_IA_PD) {
                        continue;
                }

                /*
                 * Try only pools with the requested prefix length if any.
                 */
                if ((plen >= 0) && (p->units != plen)) {
                        continue;
                }

                if (create_prefix6(p, pref, &attempts, client_id,
                                   cur_time + 120) == ISC_R_SUCCESS) {
                        log_debug("Picking pool prefix %s/%u",
                                  inet_ntop(AF_INET6, &((*pref)->addr),
                                            tmp_buf, sizeof(tmp_buf)),
                                  (unsigned) (*pref)->plen);
                        return ISC_R_SUCCESS;
                }
        }

        /*
         * If we failed to pick an IPv6 prefix
         * Presumably that means we have no prefixes for the client.
         */
        log_debug("Unable to pick client prefix: no prefixes available");
        return ISC_R_NORESOURCES;
}

/*
 *! \file server/dhcpv6.c
 *
 * \brief construct a reply containing information about a client's lease
 *
 * lease_to_client() is called from several messages to construct a
 * reply that contains all that we know about the client's correct lease
 * (or projected lease).
 *
 * Solicit - "Soft" binding, ignore unknown addresses or bindings, just
 *           send what we "may" give them on a request.
 *
 * Request - "Hard" binding, but ignore supplied addresses (just provide what
 *           the client should really use).
 *
 * Renew   - "Hard" binding, but client-supplied addresses are 'real'.  Error
 * Rebind    out any "wrong" addresses the client sends.  This means we send
 *           an empty IA_NA with a status code of NoBinding or NotOnLink or
 *           possibly send the address with zeroed lifetimes.
 *
 * Information-Request - No binding.
 *
 * The basic structure is to traverse the client-supplied data first, and
 * validate and echo back any contents that can be.  If the client-supplied
 * data does not error out (on renew/rebind as above), but we did not send
 * any addresses, attempt to allocate one.
 *
 * At the end of the this function we call commit_leases_timed() to
 * fsync and rotate the file as necessary.  commit_leases_timed() will
 * check that we have written at least one lease to the file and that
 * some time has passed before doing any fsync or file rewrite so we
 * don't bother tracking if we did a write_ia during this function.
 */
/* TODO: look at client hints for lease times */

static void
lease_to_client(struct data_string *reply_ret,
                struct packet *packet, 
                const struct data_string *client_id,
                const struct data_string *server_id)
{
        static struct reply_state reply;
        struct option_cache *oc;
        struct data_string packet_oro;
#if defined (RFC3315_PRE_ERRATA_2010_08)
        isc_boolean_t no_resources_avail = ISC_FALSE;
#endif

        memset(&packet_oro, 0, sizeof(packet_oro));

        /* Locate the client.  */
        if (shared_network_from_packet6(&reply.shared,
                                        packet) != ISC_R_SUCCESS)
                goto exit;

        /* 
         * Initialize the reply.
         */
        packet_reference(&reply.packet, packet, MDL);
        data_string_copy(&reply.client_id, client_id, MDL);

        if (!start_reply(packet, client_id, server_id, &reply.opt_state,
                         &reply.buf.reply))
                goto exit;

        /* Set the write cursor to just past the reply header. */
        reply.cursor = REPLY_OPTIONS_INDEX;

        /*
         * Get the ORO from the packet, if any.
         */
        oc = lookup_option(&dhcpv6_universe, packet->options, D6O_ORO);
        if (oc != NULL) {
                if (!evaluate_option_cache(&packet_oro, packet, 
                                           NULL, NULL, 
                                           packet->options, NULL,
                                           &global_scope, oc, MDL)) {
                        log_error("lease_to_client: error evaluating ORO.");
                        goto exit;
                }
        }

        /* 
         * Find a host record that matches from the packet, if any, and is
         * valid for the shared network the client is on.
         */
        if (find_hosts_by_uid(&reply.host, client_id->data, client_id->len,
                              MDL))
                seek_shared_host(&reply.host, reply.shared);

        if ((reply.host == NULL) &&
            find_hosts_by_option(&reply.host, packet, packet->options, MDL))
                seek_shared_host(&reply.host, reply.shared);

        /*
         * Check for 'hardware' matches last, as some of the synthesis methods
         * are not considered to be as reliable.
         */
        if ((reply.host == NULL) &&
            find_hosts_by_duid_chaddr(&reply.host, client_id))
                seek_shared_host(&reply.host, reply.shared);

        /* Process the client supplied IA's onto the reply buffer. */
        reply.ia_count = 0;
        oc = lookup_option(&dhcpv6_universe, packet->options, D6O_IA_NA);

        for (; oc != NULL ; oc = oc->next) {
                isc_result_t status;

                /* Start counting resources (addresses) offered. */
                reply.client_resources = 0;
                reply.resources_included = ISC_FALSE;

                status = reply_process_ia_na(&reply, oc);

                /*
                 * We continue to try other IA's whether we can address
                 * this one or not.  Any other result is an immediate fail.
                 */
                if ((status != ISC_R_SUCCESS) &&
                    (status != ISC_R_NORESOURCES))
                        goto exit;

#if defined (RFC3315_PRE_ERRATA_2010_08)
                /*
                 * If any address cannot be given to any IA, then set the
                 * NoAddrsAvail status code.
                 */
                if (reply.client_resources == 0)
                        no_resources_avail = ISC_TRUE;
#endif
        }
        oc = lookup_option(&dhcpv6_universe, packet->options, D6O_IA_TA);
        for (; oc != NULL ; oc = oc->next) {
                isc_result_t status;

                /* Start counting resources (addresses) offered. */
                reply.client_resources = 0;
                reply.resources_included = ISC_FALSE;

                status = reply_process_ia_ta(&reply, oc);

                /*
                 * We continue to try other IA's whether we can address
                 * this one or not.  Any other result is an immediate fail.
                 */
                if ((status != ISC_R_SUCCESS) &&
                    (status != ISC_R_NORESOURCES))
                        goto exit;

#if defined (RFC3315_PRE_ERRATA_2010_08)
                /*
                 * If any address cannot be given to any IA, then set the
                 * NoAddrsAvail status code.
                 */
                if (reply.client_resources == 0)
                        no_resources_avail = ISC_TRUE;
#endif
        }

        /* Same for IA_PD's. */
        reply.pd_count = 0;
        oc = lookup_option(&dhcpv6_universe, packet->options, D6O_IA_PD);
        for (; oc != NULL ; oc = oc->next) {
                isc_result_t status;

                /* Start counting resources (prefixes) offered. */
                reply.client_resources = 0;
                reply.resources_included = ISC_FALSE;

                status = reply_process_ia_pd(&reply, oc);

                /*
                 * We continue to try other IA_PD's whether we can address
                 * this one or not.  Any other result is an immediate fail.
                 */
                if ((status != ISC_R_SUCCESS) &&
                    (status != ISC_R_NORESOURCES))
                        goto exit;
        }

        /*
         * Make no reply if we gave no resources and is not
         * for Information-Request.
         */
        if ((reply.ia_count == 0) && (reply.pd_count == 0)) {
                if (reply.packet->dhcpv6_msg_type !=
                                            DHCPV6_INFORMATION_REQUEST)
                        goto exit;

                /*
                 * Because we only execute statements on a per-IA basis,
                 * we need to execute statements in any non-IA reply to
                 * source configuration.
                 */
                execute_statements_in_scope(NULL, reply.packet, NULL, NULL,
                                            reply.packet->options,
                                            reply.opt_state, &global_scope,
                                            reply.shared->group, root_group,
                                            NULL);

                /* Bring in any configuration from a host record. */
                if (reply.host != NULL)
                        execute_statements_in_scope(NULL, reply.packet,
                                                    NULL, NULL,
                                                    reply.packet->options,
                                                    reply.opt_state,
                                                    &global_scope,
                                                    reply.host->group,
                                                    reply.shared->group, NULL);
        }

        /*
         * RFC3315 section 17.2.2 (Solicit):
         *
         * If the server will not assign any addresses to any IAs in a
         * subsequent Request from the client, the server MUST send an
         * Advertise message to the client that includes only a Status
         * Code option with code NoAddrsAvail and a status message for
         * the user, a Server Identifier option with the server's DUID,
         * and a Client Identifier option with the client's DUID.
         *
         * Section 18.2.1 (Request):
         *
         * If the server cannot assign any addresses to an IA in the
         * message from the client, the server MUST include the IA in
         * the Reply message with no addresses in the IA and a Status
         * Code option in the IA containing status code NoAddrsAvail.
         *
         * Section 18.1.8 (Client Behavior):
         *
         * Leave unchanged any information about addresses the client has
         * recorded in the IA but that were not included in the IA from
         * the server.
         * Sends a Renew/Rebind if the IA is not in the Reply message.
         */
#if defined (RFC3315_PRE_ERRATA_2010_08)
        if (no_resources_avail && (reply.ia_count != 0) &&
            (reply.packet->dhcpv6_msg_type == DHCPV6_SOLICIT))
        {
                /* Set the NoAddrsAvail status code. */
                if (!set_status_code(STATUS_NoAddrsAvail,
                                     "No addresses available for this "
                                     "interface.", reply.opt_state)) {
                        log_error("lease_to_client: Unable to set "
                                  "NoAddrsAvail status code.");
                        goto exit;
                }

                /* Rewind the cursor to the start. */
                reply.cursor = REPLY_OPTIONS_INDEX;

                /*
                 * Produce an advertise that includes only:
                 *
                 * Status code.
                 * Server DUID.
                 * Client DUID.
                 */
                reply.buf.reply.msg_type = DHCPV6_ADVERTISE;
                reply.cursor += store_options6((char *)reply.buf.data +
                                                        reply.cursor,
                                               sizeof(reply.buf) -
                                                        reply.cursor,
                                               reply.opt_state, reply.packet,
                                               required_opts_NAA,
                                               NULL);
        } else {
                /*
                 * Having stored the client's IA's, store any options that
                 * will fit in the remaining space.
                 */
                reply.cursor += store_options6((char *)reply.buf.data +
                                                        reply.cursor,
                                               sizeof(reply.buf) -
                                                        reply.cursor,
                                               reply.opt_state, reply.packet,
                                               required_opts_solicit,
                                               &packet_oro);
        }
#else /* defined (RFC3315_PRE_ERRATA_2010_08) */
        /*
         * Having stored the client's IA's, store any options that
         * will fit in the remaining space.
         */
        reply.cursor += store_options6((char *)reply.buf.data + reply.cursor,
                                       sizeof(reply.buf) - reply.cursor,
                                       reply.opt_state, reply.packet,
                                       required_opts_solicit,
                                       &packet_oro);
#endif /* defined (RFC3315_PRE_ERRATA_2010_08) */

        /* Return our reply to the caller. */
        reply_ret->len = reply.cursor;
        reply_ret->buffer = NULL;
        if (!buffer_allocate(&reply_ret->buffer, reply.cursor, MDL)) {
                log_fatal("No memory to store Reply.");
        }
        memcpy(reply_ret->buffer->data, reply.buf.data, reply.cursor);
        reply_ret->data = reply_ret->buffer->data;

        /* If appropriate commit and rotate the lease file */
        (void) commit_leases_timed();

      exit:
        /* Cleanup. */
        if (reply.shared != NULL)
                shared_network_dereference(&reply.shared, MDL);
        if (reply.host != NULL)
                host_dereference(&reply.host, MDL);
        if (reply.opt_state != NULL)
                option_state_dereference(&reply.opt_state, MDL);
        if (reply.packet != NULL)
                packet_dereference(&reply.packet, MDL);
        if (reply.client_id.data != NULL)
                data_string_forget(&reply.client_id, MDL);
        if (packet_oro.buffer != NULL)
                data_string_forget(&packet_oro, MDL);
        reply.renew = reply.rebind = reply.prefer = reply.valid = 0;
        reply.cursor = 0;
}

/* Process a client-supplied IA_NA.  This may append options to the tail of
 * the reply packet being built in the reply_state structure.
 */
static isc_result_t
reply_process_ia_na(struct reply_state *reply, struct option_cache *ia) {
        isc_result_t status = ISC_R_SUCCESS;
        u_int32_t iaid;
        unsigned ia_cursor;
        struct option_state *packet_ia;
        struct option_cache *oc;
        struct data_string ia_data, data;

        /* Initialize values that will get cleaned up on return. */
        packet_ia = NULL;
        memset(&ia_data, 0, sizeof(ia_data));
        memset(&data, 0, sizeof(data));
        /* 
         * Note that find_client_address() may set reply->lease. 
         */

        /* Make sure there is at least room for the header. */
        if ((reply->cursor + IA_NA_OFFSET + 4) > sizeof(reply->buf)) {
                log_error("reply_process_ia_na: Reply too long for IA.");
                return ISC_R_NOSPACE;
        }


        /* Fetch the IA_NA contents. */
        if (!get_encapsulated_IA_state(&packet_ia, &ia_data, reply->packet,
                                       ia, IA_NA_OFFSET)) {
                log_error("reply_process_ia_na: error evaluating ia");
                status = ISC_R_FAILURE;
                goto cleanup;
        }

        /* Extract IA_NA header contents. */
        iaid = getULong(ia_data.data);
        reply->renew = getULong(ia_data.data + 4);
        reply->rebind = getULong(ia_data.data + 8);

        /* Create an IA_NA structure. */
        if (ia_allocate(&reply->ia, iaid, (char *)reply->client_id.data, 
                        reply->client_id.len, MDL) != ISC_R_SUCCESS) {
                log_error("reply_process_ia_na: no memory for ia.");
                status = ISC_R_NOMEMORY;
                goto cleanup;
        }
        reply->ia->ia_type = D6O_IA_NA;

        /* Cache pre-existing IA, if any. */
        ia_hash_lookup(&reply->old_ia, ia_na_active,
                       (unsigned char *)reply->ia->iaid_duid.data,
                       reply->ia->iaid_duid.len, MDL);

        /*
         * Create an option cache to carry the IA_NA option contents, and
         * execute any user-supplied values into it.
         */
        if (!option_state_allocate(&reply->reply_ia, MDL)) {
                status = ISC_R_NOMEMORY;
                goto cleanup;
        }

        /* Check & cache the fixed host record. */
        if ((reply->host != NULL) && (reply->host->fixed_addr != NULL)) {
                struct iaddr tmp_addr;

                if (!evaluate_option_cache(&reply->fixed, NULL, NULL, NULL,
                                           NULL, NULL, &global_scope,
                                           reply->host->fixed_addr, MDL)) {
                        log_error("reply_process_ia_na: unable to evaluate "
                                  "fixed address.");
                        status = ISC_R_FAILURE;
                        goto cleanup;
                }

                if (reply->fixed.len < 16) {
                        log_error("reply_process_ia_na: invalid fixed address.");
                        status = DHCP_R_INVALIDARG;
                        goto cleanup;
                }

                /* Find the static lease's subnet. */
                tmp_addr.len = 16;
                memcpy(tmp_addr.iabuf, reply->fixed.data, 16);

                if (find_grouped_subnet(&reply->subnet, reply->shared,
                                        tmp_addr, MDL) == 0)
                        log_fatal("Impossible condition at %s:%d.", MDL);

                reply->static_lease = ISC_TRUE;
        } else
                reply->static_lease = ISC_FALSE;

        /*
         * Save the cursor position at the start of the IA, so we can
         * set length and adjust t1/t2 values later.  We write a temporary
         * header out now just in case we decide to adjust the packet
         * within sub-process functions.
         */
        ia_cursor = reply->cursor;

        /* Initialize the IA_NA header.  First the code. */
        putUShort(reply->buf.data + reply->cursor, (unsigned)D6O_IA_NA);
        reply->cursor += 2;

        /* Then option length. */
        putUShort(reply->buf.data + reply->cursor, 0x0Cu);
        reply->cursor += 2;

        /* Then IA_NA header contents; IAID. */
        putULong(reply->buf.data + reply->cursor, iaid);
        reply->cursor += 4;

        /* We store the client's t1 for now, and may over-ride it later. */
        putULong(reply->buf.data + reply->cursor, reply->renew);
        reply->cursor += 4;

        /* We store the client's t2 for now, and may over-ride it later. */
        putULong(reply->buf.data + reply->cursor, reply->rebind);
        reply->cursor += 4;

        /* 
         * For each address in this IA_NA, decide what to do about it.
         *
         * Guidelines:
         *
         * The client leaves unchanged any information about addresses
         * it has recorded but are not included ("cancel/break" below).
         * A not included IA ("cleanup" below) could give a Renew/Rebind.
         */
        oc = lookup_option(&dhcpv6_universe, packet_ia, D6O_IAADDR);
        reply->valid = reply->prefer = 0xffffffff;
        reply->client_valid = reply->client_prefer = 0;
        for (; oc != NULL ; oc = oc->next) {
                status = reply_process_addr(reply, oc);

                /*
                 * Canceled means we did not allocate addresses to the
                 * client, but we're "done" with this IA - we set a status
                 * code.  So transmit this reply, e.g., move on to the next
                 * IA.
                 */
                if (status == ISC_R_CANCELED)
                        break;

                if ((status != ISC_R_SUCCESS) &&
                    (status != ISC_R_ADDRINUSE) &&
                    (status != ISC_R_ADDRNOTAVAIL))
                        goto cleanup;
        }

        reply->ia_count++;

        /*
         * If we fell through the above and never gave the client
         * an address, give it one now.
         */
        if ((status != ISC_R_CANCELED) && (reply->client_resources == 0)) {
                status = find_client_address(reply);

                if (status == ISC_R_NORESOURCES) {
                        switch (reply->packet->dhcpv6_msg_type) {
                              case DHCPV6_SOLICIT:
                                /*
                                 * No address for any IA is handled
                                 * by the caller.
                                 */
                                /* FALL THROUGH */

                              case DHCPV6_REQUEST:
                                /* Section 18.2.1 (Request):
                                 *
                                 * If the server cannot assign any addresses to
                                 * an IA in the message from the client, the
                                 * server MUST include the IA in the Reply
                                 * message with no addresses in the IA and a
                                 * Status Code option in the IA containing
                                 * status code NoAddrsAvail.
                                 */
                                option_state_dereference(&reply->reply_ia, MDL);
                                if (!option_state_allocate(&reply->reply_ia,
                                                           MDL))
                                {
                                        log_error("reply_process_ia_na: No "
                                                  "memory for option state "
                                                  "wipe.");
                                        status = ISC_R_NOMEMORY;
                                        goto cleanup;
                                }

                                if (!set_status_code(STATUS_NoAddrsAvail,
                                                     "No addresses available "
                                                     "for this interface.",
                                                      reply->reply_ia)) {
                                        log_error("reply_process_ia_na: Unable "
                                                  "to set NoAddrsAvail status "
                                                  "code.");
                                        status = ISC_R_FAILURE;
                                        goto cleanup;
                                }

                                status = ISC_R_SUCCESS;
                                break;

                              default:
                                /*
                                 * RFC 3315 does not tell us to emit a status
                                 * code in this condition, or anything else.
                                 *
                                 * If we included non-allocated addresses
                                 * (zeroed lifetimes) in an IA, then the client
                                 * will deconfigure them.
                                 *
                                 * So we want to include the IA even if we
                                 * can't give it a new address if it includes
                                 * zeroed lifetime addresses.
                                 *
                                 * We don't want to include the IA if we
                                 * provide zero addresses including zeroed
                                 * lifetimes.
                                 */
                                if (reply->resources_included)
                                        status = ISC_R_SUCCESS;
                                else
                                        goto cleanup;
                                break;
                        }
                }

                if (status != ISC_R_SUCCESS)
                        goto cleanup;
        }

        reply->cursor += store_options6((char *)reply->buf.data + reply->cursor,
                                        sizeof(reply->buf) - reply->cursor,
                                        reply->reply_ia, reply->packet,
                                        required_opts_IA, NULL);

        /* Reset the length of this IA to match what was just written. */
        putUShort(reply->buf.data + ia_cursor + 2,
                  reply->cursor - (ia_cursor + 4));

        /*
         * T1/T2 time selection is kind of weird.  We actually use DHCP
         * (v4) scoped options as handy existing places where these might
         * be configured by an administrator.  A value of zero tells the
         * client it may choose its own renewal time.
         */
        reply->renew = 0;
        oc = lookup_option(&dhcp_universe, reply->opt_state,
                           DHO_DHCP_RENEWAL_TIME);
        if (oc != NULL) {
                if (!evaluate_option_cache(&data, reply->packet, NULL, NULL,
                                           reply->packet->options,
                                           reply->opt_state, &global_scope,
                                           oc, MDL) ||
                    (data.len != 4)) {
                        log_error("Invalid renewal time.");
                } else {
                        reply->renew = getULong(data.data);
                }

                if (data.data != NULL)
                        data_string_forget(&data, MDL);
        }
        putULong(reply->buf.data + ia_cursor + 8, reply->renew);

        /* Now T2. */
        reply->rebind = 0;
        oc = lookup_option(&dhcp_universe, reply->opt_state,
                           DHO_DHCP_REBINDING_TIME);
        if (oc != NULL) {
                if (!evaluate_option_cache(&data, reply->packet, NULL, NULL,
                                           reply->packet->options,
                                           reply->opt_state, &global_scope,
                                           oc, MDL) ||
                    (data.len != 4)) {
                        log_error("Invalid rebinding time.");
                } else {
                        reply->rebind = getULong(data.data);
                }

                if (data.data != NULL)
                        data_string_forget(&data, MDL);
        }
        putULong(reply->buf.data + ia_cursor + 12, reply->rebind);

        /*
         * If this is not a 'soft' binding, consume the new changes into
         * the database (if any have been attached to the ia_na).
         *
         * Loop through the assigned dynamic addresses, referencing the
         * leases onto this IA_NA rather than any old ones, and updating
         * pool timers for each (if any).
         */
        if ((status != ISC_R_CANCELED) && !reply->static_lease &&
            (reply->buf.reply.msg_type == DHCPV6_REPLY) &&
            (reply->ia->num_iasubopt != 0)) {
                struct iasubopt *tmp;
                struct data_string *ia_id;
                int i;

                for (i = 0 ; i < reply->ia->num_iasubopt ; i++) {
                        tmp = reply->ia->iasubopt[i];

                        if (tmp->ia != NULL)
                                ia_dereference(&tmp->ia, MDL);
                        ia_reference(&tmp->ia, reply->ia, MDL);

                        /* Commit 'hard' bindings. */
                        renew_lease6(tmp->ipv6_pool, tmp);
                        schedule_lease_timeout(tmp->ipv6_pool);

                        /* If we have anything to do on commit do it now */
                        if (tmp->on_star.on_commit != NULL) {
                                execute_statements(NULL, reply->packet,
                                                   NULL, NULL, 
                                                   reply->packet->options,
                                                   reply->opt_state,
                                                   &reply->lease->scope,
                                                   tmp->on_star.on_commit,
                                                   &tmp->on_star);
                                executable_statement_dereference
                                        (&tmp->on_star.on_commit, MDL);
                        }

#if defined (NSUPDATE)
                        /*
                         * Perform ddns updates.
                         */
                        oc = lookup_option(&server_universe, reply->opt_state,
                                           SV_DDNS_UPDATES);
                        if ((oc == NULL) ||
                            evaluate_boolean_option_cache(NULL, reply->packet,
                                                          NULL, NULL,
                                                        reply->packet->options,
                                                          reply->opt_state,
                                                          &tmp->scope,
                                                          oc, MDL)) {
                                ddns_updates(reply->packet, NULL, NULL,
                                             tmp, NULL, reply->opt_state);
                        }
#endif
                }

                /* Remove any old ia from the hash. */
                if (reply->old_ia != NULL) {
                        ia_id = &reply->old_ia->iaid_duid;
                        ia_hash_delete(ia_na_active,
                                       (unsigned char *)ia_id->data,
                                       ia_id->len, MDL);
                        ia_dereference(&reply->old_ia, MDL);
                }

                /* Put new ia into the hash. */
                reply->ia->cltt = cur_time;
                ia_id = &reply->ia->iaid_duid;
                ia_hash_add(ia_na_active, (unsigned char *)ia_id->data,
                            ia_id->len, reply->ia, MDL);

                write_ia(reply->ia);
        }

        /*
         * If this would be a hard binding for a static lease
         * run any commit statements that we have
         */
        if ((status != ISC_R_CANCELED) && reply->static_lease &&
            (reply->buf.reply.msg_type == DHCPV6_REPLY) &&
            (reply->on_star.on_commit != NULL)) {
                execute_statements(NULL, reply->packet, NULL, NULL, 
                                   reply->packet->options, reply->opt_state,
                                   NULL, reply->on_star.on_commit, NULL);
                executable_statement_dereference
                        (&reply->on_star.on_commit, MDL);
        }

      cleanup:
        if (packet_ia != NULL)
                option_state_dereference(&packet_ia, MDL);
        if (reply->reply_ia != NULL)
                option_state_dereference(&reply->reply_ia, MDL);
        if (ia_data.data != NULL)
                data_string_forget(&ia_data, MDL);
        if (data.data != NULL)
                data_string_forget(&data, MDL);
        if (reply->ia != NULL)
                ia_dereference(&reply->ia, MDL);
        if (reply->old_ia != NULL)
                ia_dereference(&reply->old_ia, MDL);
        if (reply->lease != NULL)
                iasubopt_dereference(&reply->lease, MDL);
        if (reply->fixed.data != NULL)
                data_string_forget(&reply->fixed, MDL);
        if (reply->subnet != NULL)
                subnet_dereference(&reply->subnet, MDL);
        if (reply->on_star.on_expiry != NULL)
                executable_statement_dereference
                        (&reply->on_star.on_expiry, MDL);
        if (reply->on_star.on_release != NULL)
                executable_statement_dereference
                        (&reply->on_star.on_release, MDL);

        /*
         * ISC_R_CANCELED is a status code used by the addr processing to
         * indicate we're replying with a status code.  This is still a
         * success at higher layers.
         */
        return((status == ISC_R_CANCELED) ? ISC_R_SUCCESS : status);
}

/*
 * Process an IAADDR within a given IA_xA, storing any IAADDR reply contents
 * into the reply's current ia-scoped option cache.  Returns ISC_R_CANCELED
 * in the event we are replying with a status code and do not wish to process
 * more IAADDRs within this IA.
 */
static isc_result_t
reply_process_addr(struct reply_state *reply, struct option_cache *addr) {
        u_int32_t pref_life, valid_life;
        struct binding_scope **scope;
        struct group *group;
        struct subnet *subnet;
        struct iaddr tmp_addr;
        struct option_cache *oc;
        struct data_string iaaddr, data;
        isc_result_t status = ISC_R_SUCCESS;

        /* Initializes values that will be cleaned up. */
        memset(&iaaddr, 0, sizeof(iaaddr));
        memset(&data, 0, sizeof(data));
        /* Note that reply->lease may be set by address_is_owned() */

        /*
         * There is no point trying to process an incoming address if there
         * is no room for an outgoing address.
         */
        if ((reply->cursor + 28) > sizeof(reply->buf)) {
                log_error("reply_process_addr: Out of room for address.");
                return ISC_R_NOSPACE;
        }

        /* Extract this IAADDR option. */
        if (!evaluate_option_cache(&iaaddr, reply->packet, NULL, NULL, 
                                   reply->packet->options, NULL, &global_scope,
                                   addr, MDL) ||
            (iaaddr.len < IAADDR_OFFSET)) {
                log_error("reply_process_addr: error evaluating IAADDR.");
                status = ISC_R_FAILURE;
                goto cleanup;
        }

        /* The first 16 bytes are the IPv6 address. */
        pref_life = getULong(iaaddr.data + 16);
        valid_life = getULong(iaaddr.data + 20);

        if ((reply->client_valid == 0) ||
            (reply->client_valid > valid_life))
                reply->client_valid = valid_life;

        if ((reply->client_prefer == 0) ||
            (reply->client_prefer > pref_life))
                reply->client_prefer = pref_life;

        /* 
         * Clients may choose to send :: as an address, with the idea to give
         * hints about preferred-lifetime or valid-lifetime.
         */
        tmp_addr.len = 16;
        memset(tmp_addr.iabuf, 0, 16);
        if (!memcmp(iaaddr.data, tmp_addr.iabuf, 16)) {
                /* Status remains success; we just ignore this one. */
                goto cleanup;
        }

        /* tmp_addr len remains 16 */
        memcpy(tmp_addr.iabuf, iaaddr.data, 16);

        /*
         * Verify that this address is on the client's network.
         */
        for (subnet = reply->shared->subnets ; subnet != NULL ;
             subnet = subnet->next_sibling) {
                if (addr_eq(subnet_number(tmp_addr, subnet->netmask),
                            subnet->net))
                        break;
        }

        /* Address not found on shared network. */
        if (subnet == NULL) {
                /* Ignore this address on 'soft' bindings. */
                if (reply->packet->dhcpv6_msg_type == DHCPV6_SOLICIT) {
                        /* disable rapid commit */
                        reply->buf.reply.msg_type = DHCPV6_ADVERTISE;
                        delete_option(&dhcpv6_universe,
                                      reply->opt_state,
                                      D6O_RAPID_COMMIT);
                        /* status remains success */
                        goto cleanup;
                }

                /*
                 * RFC3315 section 18.2.1:
                 *
                 * If the server finds that the prefix on one or more IP
                 * addresses in any IA in the message from the client is not
                 * appropriate for the link to which the client is connected,
                 * the server MUST return the IA to the client with a Status
                 * Code option with the value NotOnLink.
                 */
                if (reply->packet->dhcpv6_msg_type == DHCPV6_REQUEST) {
                        /* Rewind the IA_NA to empty. */
                        option_state_dereference(&reply->reply_ia, MDL);
                        if (!option_state_allocate(&reply->reply_ia, MDL)) {
                                log_error("reply_process_addr: No memory for "
                                          "option state wipe.");
                                status = ISC_R_NOMEMORY;
                                goto cleanup;
                        }

                        /* Append a NotOnLink status code. */
                        if (!set_status_code(STATUS_NotOnLink,
                                             "Address not for use on this "
                                             "link.", reply->reply_ia)) {
                                log_error("reply_process_addr: Failure "
                                          "setting status code.");
                                status = ISC_R_FAILURE;
                                goto cleanup;
                        }

                        /* Fin (no more IAADDRs). */
                        status = ISC_R_CANCELED;
                        goto cleanup;
                }

                /*
                 * RFC3315 sections 18.2.3 and 18.2.4 have identical language:
                 *
                 * If the server finds that any of the addresses are not
                 * appropriate for the link to which the client is attached,
                 * the server returns the address to the client with lifetimes
                 * of 0.
                 */
                if ((reply->packet->dhcpv6_msg_type != DHCPV6_RENEW) &&
                    (reply->packet->dhcpv6_msg_type != DHCPV6_REBIND)) {
                        log_error("It is impossible to lease a client that is "
                                  "not sending a solicit, request, renew, or "
                                  "rebind.");
                        status = ISC_R_FAILURE;
                        goto cleanup;
                }

                reply->send_prefer = reply->send_valid = 0;
                goto send_addr;
        }

        /* Verify the address belongs to the client. */
        if (!address_is_owned(reply, &tmp_addr)) {
                /*
                 * For solicit and request, any addresses included are
                 * 'requested' addresses.  For rebind, we actually have
                 * no direction on what to do from 3315 section 18.2.4!
                 * So I think the best bet is to try and give it out, and if
                 * we can't, zero lifetimes.
                 */
                if ((reply->packet->dhcpv6_msg_type == DHCPV6_SOLICIT) ||
                    (reply->packet->dhcpv6_msg_type == DHCPV6_REQUEST) ||
                    (reply->packet->dhcpv6_msg_type == DHCPV6_REBIND)) {
                        status = reply_process_try_addr(reply, &tmp_addr);

                        /*
                         * If the address is in use, or isn't in any dynamic
                         * range, continue as normal.  If any other error was
                         * found, error out.
                         */
                        if ((status != ISC_R_SUCCESS) && 
                            (status != ISC_R_ADDRINUSE) &&
                            (status != ISC_R_ADDRNOTAVAIL))
                                goto cleanup;

                        /*
                         * If we didn't honor this lease, for solicit and
                         * request we simply omit it from our answer.  For
                         * rebind, we send it with zeroed lifetimes.
                         */
                        if (reply->lease == NULL) {
                                if (reply->packet->dhcpv6_msg_type ==
                                                        DHCPV6_REBIND) {
                                        reply->send_prefer = 0;
                                        reply->send_valid = 0;
                                        goto send_addr;
                                }

                                /* status remains success - ignore */
                                goto cleanup;
                        }
                /*
                 * RFC3315 section 18.2.3:
                 *
                 * If the server cannot find a client entry for the IA the
                 * server returns the IA containing no addresses with a Status
                 * Code option set to NoBinding in the Reply message.
                 *
                 * On mismatch we (ab)use this pretending we have not the IA
                 * as soon as we have not an address.
                 */
                } else if (reply->packet->dhcpv6_msg_type == DHCPV6_RENEW) {
                        /* Rewind the IA_NA to empty. */
                        option_state_dereference(&reply->reply_ia, MDL);
                        if (!option_state_allocate(&reply->reply_ia, MDL)) {
                                log_error("reply_process_addr: No memory for "
                                          "option state wipe.");
                                status = ISC_R_NOMEMORY;
                                goto cleanup;
                        }

                        /* Append a NoBinding status code.  */
                        if (!set_status_code(STATUS_NoBinding,
                                             "Address not bound to this "
                                             "interface.", reply->reply_ia)) {
                                log_error("reply_process_addr: Unable to "
                                          "attach status code.");
                                status = ISC_R_FAILURE;
                                goto cleanup;
                        }

                        /* Fin (no more IAADDRs). */
                        status = ISC_R_CANCELED;
                        goto cleanup;
                } else {
                        log_error("It is impossible to lease a client that is "
                                  "not sending a solicit, request, renew, or "
                                  "rebind message.");
                        status = ISC_R_FAILURE;
                        goto cleanup;
                }
        }

        if (reply->static_lease) {
                if (reply->host == NULL)
                        log_fatal("Impossible condition at %s:%d.", MDL);

                scope = &global_scope;
                group = reply->subnet->group;
        } else {
                if (reply->lease == NULL)
                        log_fatal("Impossible condition at %s:%d.", MDL);

                scope = &reply->lease->scope;
                group = reply->lease->ipv6_pool->subnet->group;
        }

        /*
         * If client_resources is nonzero, then the reply_process_is_addressed
         * function has executed configuration state into the reply option
         * cache.  We will use that valid cache to derive configuration for
         * whether or not to engage in additional addresses, and similar.
         */
        if (reply->client_resources != 0) {
                unsigned limit = 1;

                /*
                 * Does this client have "enough" addresses already?  Default
                 * to one.  Everybody gets one, and one should be enough for
                 * anybody.
                 */
                oc = lookup_option(&server_universe, reply->opt_state,
                                   SV_LIMIT_ADDRS_PER_IA);
                if (oc != NULL) {
                        if (!evaluate_option_cache(&data, reply->packet,
                                                   NULL, NULL,
                                                   reply->packet->options,
                                                   reply->opt_state,
                                                   scope, oc, MDL) ||
                            (data.len != 4)) {
                                log_error("reply_process_addr: unable to "
                                          "evaluate addrs-per-ia value.");
                                status = ISC_R_FAILURE;
                                goto cleanup;
                        }

                        limit = getULong(data.data);
                        data_string_forget(&data, MDL);
                }

                /*
                 * If we wish to limit the client to a certain number of
                 * addresses, then omit the address from the reply.
                 */
                if (reply->client_resources >= limit)
                        goto cleanup;
        }

        status = reply_process_is_addressed(reply, scope, group);
        if (status != ISC_R_SUCCESS)
                goto cleanup;

      send_addr:
        status = reply_process_send_addr(reply, &tmp_addr);

      cleanup:
        if (iaaddr.data != NULL)
                data_string_forget(&iaaddr, MDL);
        if (data.data != NULL)
                data_string_forget(&data, MDL);
        if (reply->lease != NULL)
                iasubopt_dereference(&reply->lease, MDL);

        return status;
}

/*
 * Verify the address belongs to the client.  If we've got a host
 * record with a fixed address, it has to be the assigned address
 * (fault out all else).  Otherwise it's a dynamic address, so lookup
 * that address and make sure it belongs to this DUID:IAID pair.
 */
static isc_boolean_t
address_is_owned(struct reply_state *reply, struct iaddr *addr) {
        int i;

        /*
         * This faults out addresses that don't match fixed addresses.
         */
        if (reply->static_lease) {
                if (reply->fixed.data == NULL)
                        log_fatal("Impossible condition at %s:%d.", MDL);

                if (memcmp(addr->iabuf, reply->fixed.data, 16) == 0)
                        return (ISC_TRUE);

                return (ISC_FALSE);
        }

        if ((reply->old_ia == NULL) || (reply->old_ia->num_iasubopt == 0))
                return (ISC_FALSE);

        for (i = 0 ; i < reply->old_ia->num_iasubopt ; i++) {
                struct iasubopt *tmp;

                tmp = reply->old_ia->iasubopt[i];

                if (memcmp(addr->iabuf, &tmp->addr, 16) == 0) {
                        if (lease6_usable(tmp) == ISC_FALSE) {
                                return (ISC_FALSE);
                        }
                        iasubopt_reference(&reply->lease, tmp, MDL);
                        return (ISC_TRUE);
                }
        }

        return (ISC_FALSE);
}

/* Process a client-supplied IA_TA.  This may append options to the tail of
 * the reply packet being built in the reply_state structure.
 */
static isc_result_t
reply_process_ia_ta(struct reply_state *reply, struct option_cache *ia) {
        isc_result_t status = ISC_R_SUCCESS;
        u_int32_t iaid;
        unsigned ia_cursor;
        struct option_state *packet_ia;
        struct option_cache *oc;
        struct data_string ia_data, data;
        struct data_string iaaddr;
        u_int32_t pref_life, valid_life;
        struct iaddr tmp_addr;

        /* Initialize values that will get cleaned up on return. */
        packet_ia = NULL;
        memset(&ia_data, 0, sizeof(ia_data));
        memset(&data, 0, sizeof(data));
        memset(&iaaddr, 0, sizeof(iaaddr));

        /* Make sure there is at least room for the header. */
        if ((reply->cursor + IA_TA_OFFSET + 4) > sizeof(reply->buf)) {
                log_error("reply_process_ia_ta: Reply too long for IA.");
                return ISC_R_NOSPACE;
        }


        /* Fetch the IA_TA contents. */
        if (!get_encapsulated_IA_state(&packet_ia, &ia_data, reply->packet,
                                       ia, IA_TA_OFFSET)) {
                log_error("reply_process_ia_ta: error evaluating ia");
                status = ISC_R_FAILURE;
                goto cleanup;
        }

        /* Extract IA_TA header contents. */
        iaid = getULong(ia_data.data);

        /* Create an IA_TA structure. */
        if (ia_allocate(&reply->ia, iaid, (char *)reply->client_id.data,
                        reply->client_id.len, MDL) != ISC_R_SUCCESS) {
                log_error("reply_process_ia_ta: no memory for ia.");
                status = ISC_R_NOMEMORY;
                goto cleanup;
        }
        reply->ia->ia_type = D6O_IA_TA;

        /* Cache pre-existing IA, if any. */
        ia_hash_lookup(&reply->old_ia, ia_ta_active,
                       (unsigned char *)reply->ia->iaid_duid.data,
                       reply->ia->iaid_duid.len, MDL);

        /*
         * Create an option cache to carry the IA_TA option contents, and
         * execute any user-supplied values into it.
         */
        if (!option_state_allocate(&reply->reply_ia, MDL)) {
                status = ISC_R_NOMEMORY;
                goto cleanup;
        }

        /*
         * Temporary leases are dynamic by definition.
         */
        reply->static_lease = ISC_FALSE;

        /*
         * Save the cursor position at the start of the IA, so we can
         * set length later.  We write a temporary
         * header out now just in case we decide to adjust the packet
         * within sub-process functions.
         */
        ia_cursor = reply->cursor;

        /* Initialize the IA_TA header.  First the code. */
        putUShort(reply->buf.data + reply->cursor, (unsigned)D6O_IA_TA);
        reply->cursor += 2;

        /* Then option length. */
        putUShort(reply->buf.data + reply->cursor, 0x04u);
        reply->cursor += 2;

        /* Then IA_TA header contents; IAID. */
        putULong(reply->buf.data + reply->cursor, iaid);
        reply->cursor += 4;

        /* 
         * Deal with an IAADDR for lifetimes.
         * For all or none, process IAADDRs as hints.
         */
        reply->valid = reply->prefer = 0xffffffff;
        reply->client_valid = reply->client_prefer = 0;
        oc = lookup_option(&dhcpv6_universe, packet_ia, D6O_IAADDR);
        for (; oc != NULL; oc = oc->next) {
                memset(&iaaddr, 0, sizeof(iaaddr));
                if (!evaluate_option_cache(&iaaddr, reply->packet,
                                           NULL, NULL,
                                           reply->packet->options, NULL,
                                           &global_scope, oc, MDL) ||
                    (iaaddr.len < IAADDR_OFFSET)) {
                        log_error("reply_process_ia_ta: error "
                                  "evaluating IAADDR.");
                        status = ISC_R_FAILURE;
                        goto cleanup;
                }
                /* The first 16 bytes are the IPv6 address. */
                pref_life = getULong(iaaddr.data + 16);
                valid_life = getULong(iaaddr.data + 20);

                if ((reply->client_valid == 0) ||
                    (reply->client_valid > valid_life))
                        reply->client_valid = valid_life;

                if ((reply->client_prefer == 0) ||
                    (reply->client_prefer > pref_life))
                        reply->client_prefer = pref_life;

                /* Nothing more if something has failed. */
                if (status == ISC_R_CANCELED)
                        continue;

                tmp_addr.len = 16;
                memcpy(tmp_addr.iabuf, iaaddr.data, 16);
                if (!temporary_is_available(reply, &tmp_addr))
                        goto bad_temp;
                status = reply_process_is_addressed(reply,
                                                    &reply->lease->scope,
                                                    reply->shared->group);
                if (status != ISC_R_SUCCESS)
                        goto bad_temp;
                status = reply_process_send_addr(reply, &tmp_addr);
                if (status != ISC_R_SUCCESS)
                        goto bad_temp;
                if (reply->lease != NULL)
                        iasubopt_dereference(&reply->lease, MDL);
                continue;

        bad_temp:
                /* Rewind the IA_TA to empty. */
                option_state_dereference(&reply->reply_ia, MDL);
                if (!option_state_allocate(&reply->reply_ia, MDL)) {
                        status = ISC_R_NOMEMORY;
                        goto cleanup;
                }
                status = ISC_R_CANCELED;
                reply->client_resources = 0;
                reply->resources_included = ISC_FALSE;
                if (reply->lease != NULL)
                        iasubopt_dereference(&reply->lease, MDL);
        }
        reply->ia_count++;

        /*
         * Give the client temporary addresses.
         */
        if (reply->client_resources != 0)
                goto store;
        status = find_client_temporaries(reply);
        if (status == ISC_R_NORESOURCES) {
                switch (reply->packet->dhcpv6_msg_type) {
                      case DHCPV6_SOLICIT:
                        /*
                         * No address for any IA is handled
                         * by the caller.
                         */
                        /* FALL THROUGH */

                      case DHCPV6_REQUEST:
                        /* Section 18.2.1 (Request):
                         *
                         * If the server cannot assign any addresses to
                         * an IA in the message from the client, the
                         * server MUST include the IA in the Reply
                         * message with no addresses in the IA and a
                         * Status Code option in the IA containing
                         * status code NoAddrsAvail.
                         */
                        option_state_dereference(&reply->reply_ia, MDL);
                        if (!option_state_allocate(&reply->reply_ia,  MDL)) {
                                log_error("reply_process_ia_ta: No "
                                          "memory for option state wipe.");
                                status = ISC_R_NOMEMORY;
                                goto cleanup;
                        }

                        if (!set_status_code(STATUS_NoAddrsAvail,
                                             "No addresses available "
                                             "for this interface.",
                                              reply->reply_ia)) {
                                log_error("reply_process_ia_ta: Unable "
                                          "to set NoAddrsAvail status code.");
                                status = ISC_R_FAILURE;
                                goto cleanup;
                        }

                        status = ISC_R_SUCCESS;
                        break;

                      default:
                        /*
                         * We don't want to include the IA if we
                         * provide zero addresses including zeroed
                         * lifetimes.
                         */
                        if (reply->resources_included)
                                status = ISC_R_SUCCESS;
                        else
                                goto cleanup;
                        break;
                }
        } else if (status != ISC_R_SUCCESS)
                goto cleanup;

      store:
        reply->cursor += store_options6((char *)reply->buf.data + reply->cursor,
                                        sizeof(reply->buf) - reply->cursor,
                                        reply->reply_ia, reply->packet,
                                        required_opts_IA, NULL);

        /* Reset the length of this IA to match what was just written. */
        putUShort(reply->buf.data + ia_cursor + 2,
                  reply->cursor - (ia_cursor + 4));

        /*
         * Consume the new changes into the database (if any have been
         * attached to the ia_ta).
         *
         * Loop through the assigned dynamic addresses, referencing the
         * leases onto this IA_TA rather than any old ones, and updating
         * pool timers for each (if any).
         */
        if ((status != ISC_R_CANCELED) &&
            (reply->buf.reply.msg_type == DHCPV6_REPLY) &&
            (reply->ia->num_iasubopt != 0)) {
                struct iasubopt *tmp;
                struct data_string *ia_id;
                int i;

                for (i = 0 ; i < reply->ia->num_iasubopt ; i++) {
                        tmp = reply->ia->iasubopt[i];

                        if (tmp->ia != NULL)
                                ia_dereference(&tmp->ia, MDL);
                        ia_reference(&tmp->ia, reply->ia, MDL);

                        /* Commit 'hard' bindings. */
                        renew_lease6(tmp->ipv6_pool, tmp);
                        schedule_lease_timeout(tmp->ipv6_pool);

                        /* If we have anything to do on commit do it now */
                        if (tmp->on_star.on_commit != NULL) {
                                execute_statements(NULL, reply->packet,
                                                   NULL, NULL, 
                                                   reply->packet->options,
                                                   reply->opt_state,
                                                   &reply->lease->scope,
                                                   tmp->on_star.on_commit,
                                                   &tmp->on_star);
                                executable_statement_dereference
                                        (&tmp->on_star.on_commit, MDL);
                        }

#if defined (NSUPDATE)
                        /*
                         * Perform ddns updates.
                         */
                        oc = lookup_option(&server_universe, reply->opt_state,
                                           SV_DDNS_UPDATES);
                        if ((oc == NULL) ||
                            evaluate_boolean_option_cache(NULL, reply->packet,
                                                          NULL, NULL,
                                                        reply->packet->options,
                                                          reply->opt_state,
                                                          &tmp->scope,
                                                          oc, MDL)) {
                                ddns_updates(reply->packet, NULL, NULL,
                                             tmp, NULL, reply->opt_state);
                        }
#endif
                }

                /* Remove any old ia from the hash. */
                if (reply->old_ia != NULL) {
                        ia_id = &reply->old_ia->iaid_duid;
                        ia_hash_delete(ia_ta_active,
                                       (unsigned char *)ia_id->data,
                                       ia_id->len, MDL);
                        ia_dereference(&reply->old_ia, MDL);
                }

                /* Put new ia into the hash. */
                reply->ia->cltt = cur_time;
                ia_id = &reply->ia->iaid_duid;
                ia_hash_add(ia_ta_active, (unsigned char *)ia_id->data,
                            ia_id->len, reply->ia, MDL);

                write_ia(reply->ia);
        }

      cleanup:
        if (packet_ia != NULL)
                option_state_dereference(&packet_ia, MDL);
        if (iaaddr.data != NULL)
                data_string_forget(&iaaddr, MDL);
        if (reply->reply_ia != NULL)
                option_state_dereference(&reply->reply_ia, MDL);
        if (ia_data.data != NULL)
                data_string_forget(&ia_data, MDL);
        if (data.data != NULL)
                data_string_forget(&data, MDL);
        if (reply->ia != NULL)
                ia_dereference(&reply->ia, MDL);
        if (reply->old_ia != NULL)
                ia_dereference(&reply->old_ia, MDL);
        if (reply->lease != NULL)
                iasubopt_dereference(&reply->lease, MDL);

        /*
         * ISC_R_CANCELED is a status code used by the addr processing to
         * indicate we're replying with other addresses.  This is still a
         * success at higher layers.
         */
        return((status == ISC_R_CANCELED) ? ISC_R_SUCCESS : status);
}

/*
 * Verify the temporary address is available.
 */
static isc_boolean_t
temporary_is_available(struct reply_state *reply, struct iaddr *addr) {
        struct in6_addr tmp_addr;
        struct subnet *subnet;
        struct ipv6_pool *pool;
        int i;

        memcpy(&tmp_addr, addr->iabuf, sizeof(tmp_addr));
        /*
         * Clients may choose to send :: as an address, with the idea to give
         * hints about preferred-lifetime or valid-lifetime.
         * So this is not a request for this address.
         */
        if (IN6_IS_ADDR_UNSPECIFIED(&tmp_addr))
                return ISC_FALSE;

        /*
         * Verify that this address is on the client's network.
         */
        for (subnet = reply->shared->subnets ; subnet != NULL ;
             subnet = subnet->next_sibling) {
                if (addr_eq(subnet_number(*addr, subnet->netmask),
                            subnet->net))
                        break;
        }

        /* Address not found on shared network. */
        if (subnet == NULL)
                return ISC_FALSE;

        /*
         * Check if this address is owned (must be before next step).
         */
        if (address_is_owned(reply, addr))
                return ISC_TRUE;

        /*
         * Verify that this address is in a temporary pool and try to get it.
         */
        if (reply->shared->ipv6_pools == NULL)
                return ISC_FALSE;
        for (i = 0 ; (pool = reply->shared->ipv6_pools[i]) != NULL ; i++) {
                if (pool->pool_type != D6O_IA_TA)
                        continue;
                if (ipv6_in_pool(&tmp_addr, pool))
                        break;
        }
        if (pool == NULL)
                return ISC_FALSE;
        if (lease6_exists(pool, &tmp_addr))
                return ISC_FALSE;
        if (iasubopt_allocate(&reply->lease, MDL) != ISC_R_SUCCESS)
                return ISC_FALSE;
        reply->lease->addr = tmp_addr;
        reply->lease->plen = 0;
        /* Default is soft binding for 2 minutes. */
        if (add_lease6(pool, reply->lease, cur_time + 120) != ISC_R_SUCCESS)
                return ISC_FALSE;

        return ISC_TRUE;
}

/*
 * Get a temporary address per prefix.
 */
static isc_result_t
find_client_temporaries(struct reply_state *reply) {
        struct shared_network *shared;
        int i;
        struct ipv6_pool *p;
        isc_result_t status;
        unsigned int attempts;
        struct iaddr send_addr;

        /*
         * No pools, we're done.
         */
        shared = reply->shared;
        if (shared->ipv6_pools == NULL) {
                log_debug("Unable to get client addresses: "
                          "no IPv6 pools on this shared network");
                return ISC_R_NORESOURCES;
        }

        status = ISC_R_NORESOURCES;
        for (i = 0;; i++) {
                p = shared->ipv6_pools[i];
                if (p == NULL) {
                        break;
                }
                if (p->pool_type != D6O_IA_TA) {
                        continue;
                }

                /*
                 * Get an address in this temporary pool.
                 */
                status = create_lease6(p, &reply->lease, &attempts,
                                       &reply->client_id, cur_time + 120);
                if (status != ISC_R_SUCCESS) {
                        log_debug("Unable to get a temporary address.");
                        goto cleanup;
                }

                status = reply_process_is_addressed(reply,
                                                    &reply->lease->scope,
                                      reply->lease->ipv6_pool->subnet->group);
                if (status != ISC_R_SUCCESS) {
                        goto cleanup;
                }
                send_addr.len = 16;
                memcpy(send_addr.iabuf, &reply->lease->addr, 16);
                status = reply_process_send_addr(reply, &send_addr);
                if (status != ISC_R_SUCCESS) {
                        goto cleanup;
                }
                /*
                 * reply->lease can't be null as we use it above
                 * add check if that changes
                 */
                iasubopt_dereference(&reply->lease, MDL);
        }

      cleanup:
        if (reply->lease != NULL) {
                iasubopt_dereference(&reply->lease, MDL);
        }
        return status;
}

/*
 * This function only returns failure on 'hard' failures.  If it succeeds,
 * it will leave a lease structure behind.
 */
static isc_result_t
reply_process_try_addr(struct reply_state *reply, struct iaddr *addr) {
        isc_result_t status = ISC_R_ADDRNOTAVAIL;
        struct ipv6_pool *pool;
        int i;
        struct data_string data_addr;

        if ((reply == NULL) || (reply->shared == NULL) ||
            (addr == NULL) || (reply->lease != NULL))
                return (DHCP_R_INVALIDARG);

        if  (reply->shared->ipv6_pools == NULL)
                return (ISC_R_ADDRNOTAVAIL);

        memset(&data_addr, 0, sizeof(data_addr));
        data_addr.len = addr->len;
        data_addr.data = addr->iabuf;

        for (i = 0 ; (pool = reply->shared->ipv6_pools[i]) != NULL ; i++) {
                if (pool->pool_type != D6O_IA_NA)
                        continue;
                status = try_client_v6_address(&reply->lease, pool,
                                               &data_addr);
                if (status == ISC_R_SUCCESS)
                        break;
        }

        /* Note that this is just pedantry.  There is no allocation to free. */
        data_string_forget(&data_addr, MDL);
        /* Return just the most recent status... */
        return (status);
}

/* Look around for an address to give the client.  First, look through the
 * old IA for addresses we can extend.  Second, try to allocate a new address.
 * Finally, actually add that address into the current reply IA.
 */
static isc_result_t
find_client_address(struct reply_state *reply) {
        struct iaddr send_addr;
        isc_result_t status = ISC_R_NORESOURCES;
        struct iasubopt *lease, *best_lease = NULL;
        struct binding_scope **scope;
        struct group *group;
        int i;

        if (reply->static_lease) {
                if (reply->host == NULL)
                        return DHCP_R_INVALIDARG;

                send_addr.len = 16;
                memcpy(send_addr.iabuf, reply->fixed.data, 16);

                scope = &global_scope;
                group = reply->subnet->group;
                goto send_addr;
        }

        if (reply->old_ia != NULL)  {
                for (i = 0 ; i < reply->old_ia->num_iasubopt ; i++) {
                        struct shared_network *candidate_shared;

                        lease = reply->old_ia->iasubopt[i];
                        candidate_shared = lease->ipv6_pool->shared_network;

                        /*
                         * Look for the best lease on the client's shared
                         * network.
                         */
                        if ((candidate_shared == reply->shared) && 
                            (lease6_usable(lease) == ISC_TRUE)) {
                                best_lease = lease_compare(lease, best_lease);
                        }
                }
        }

        /* Try to pick a new address if we didn't find one, or if we found an
         * abandoned lease.
         */
        if ((best_lease == NULL) || (best_lease->state == FTS_ABANDONED)) {
                status = pick_v6_address(&reply->lease, reply->shared,
                                         &reply->ia->iaid_duid);
        } else if (best_lease != NULL) {
                iasubopt_reference(&reply->lease, best_lease, MDL);
                status = ISC_R_SUCCESS;
        }

        /* Pick the abandoned lease as a last resort. */
        if ((status == ISC_R_NORESOURCES) && (best_lease != NULL)) {
                /* I don't see how this is supposed to be done right now. */
                log_error("Reclaiming abandoned addresses is not yet "
                          "supported.  Treating this as an out of space "
                          "condition.");
                /* iasubopt_reference(&reply->lease, best_lease, MDL); */
        }

        /* Give up now if we didn't find a lease. */
        if (status != ISC_R_SUCCESS)
                return status;

        if (reply->lease == NULL)
                log_fatal("Impossible condition at %s:%d.", MDL);

        /* Draw binding scopes from the lease's binding scope, and config
         * from the lease's containing subnet and higher.  Note that it may
         * be desirable to place the group attachment directly in the pool.
         */
        scope = &reply->lease->scope;
        group = reply->lease->ipv6_pool->subnet->group;

        send_addr.len = 16;
        memcpy(send_addr.iabuf, &reply->lease->addr, 16);

      send_addr:
        status = reply_process_is_addressed(reply, scope, group);
        if (status != ISC_R_SUCCESS)
                return status;

        status = reply_process_send_addr(reply, &send_addr);
        return status;
}

/* Once an address is found for a client, perform several common functions;
 * Calculate and store valid and preferred lease times, draw client options
 * into the option state.
 */
static isc_result_t
reply_process_is_addressed(struct reply_state *reply,
                           struct binding_scope **scope, struct group *group)
{
        isc_result_t status = ISC_R_SUCCESS;
        struct data_string data;
        struct option_cache *oc;
        struct option_state *tmp_options = NULL;
        struct on_star *on_star;

        /* Initialize values we will cleanup. */
        memset(&data, 0, sizeof(data));

        /*
         * Find the proper on_star block to use.  We use the
         * one in the lease if we have a lease or the one in
         * the reply if we don't have a lease because this is
         * a static instance
         */
        if (reply->lease) {
                on_star = &reply->lease->on_star;
        } else {
                on_star = &reply->on_star;
        }

        /*
         * Bring in the root configuration.  We only do this to bring
         * in the on * statements, as we didn't have the lease available
         * we did it the first time.
         */
        option_state_allocate(&tmp_options, MDL);
        execute_statements_in_scope(NULL, reply->packet, NULL, NULL,
                                    reply->packet->options, tmp_options,
                                    &global_scope, root_group, NULL,
                                    on_star);
        if (tmp_options != NULL) {
                option_state_dereference(&tmp_options, MDL);
        }

        /*
         * Bring configured options into the root packet level cache - start
         * with the lease's closest enclosing group (passed in by the caller
         * as 'group').
         */
        execute_statements_in_scope(NULL, reply->packet, NULL, NULL,
                                    reply->packet->options, reply->opt_state,
                                    scope, group, root_group, on_star);

        /*
         * If there is a host record, over-ride with values configured there,
         * without re-evaluating configuration from the previously executed
         * group or its common enclosers.
         */
        if (reply->host != NULL)
                execute_statements_in_scope(NULL, reply->packet, NULL, NULL,
                                            reply->packet->options,
                                            reply->opt_state, scope,
                                            reply->host->group, group,
                                            on_star);

        /* Determine valid lifetime. */
        if (reply->client_valid == 0)
                reply->send_valid = DEFAULT_DEFAULT_LEASE_TIME;
        else
                reply->send_valid = reply->client_valid;

        oc = lookup_option(&server_universe, reply->opt_state,
                           SV_DEFAULT_LEASE_TIME);
        if (oc != NULL) {
                if (!evaluate_option_cache(&data, reply->packet, NULL, NULL,
                                           reply->packet->options,
                                           reply->opt_state,
                                           scope, oc, MDL) ||
                    (data.len != 4)) {
                        log_error("reply_process_is_addressed: unable to "
                                  "evaluate default lease time");
                        status = ISC_R_FAILURE;
                        goto cleanup;
                }

                reply->send_valid = getULong(data.data);
                data_string_forget(&data, MDL);
        }

        if (reply->client_prefer == 0)
                reply->send_prefer = reply->send_valid;
        else
                reply->send_prefer = reply->client_prefer;

        if (reply->send_prefer >= reply->send_valid)
                reply->send_prefer = (reply->send_valid / 2) +
                                     (reply->send_valid / 8);

        oc = lookup_option(&server_universe, reply->opt_state,
                           SV_PREFER_LIFETIME);
        if (oc != NULL) {
                if (!evaluate_option_cache(&data, reply->packet, NULL, NULL,
                                           reply->packet->options,
                                           reply->opt_state,
                                           scope, oc, MDL) ||
                    (data.len != 4)) {
                        log_error("reply_process_is_addressed: unable to "
                                  "evaluate preferred lease time");
                        status = ISC_R_FAILURE;
                        goto cleanup;
                }

                reply->send_prefer = getULong(data.data);
                data_string_forget(&data, MDL);
        }

        /* Note lowest values for later calculation of renew/rebind times. */
        if (reply->prefer > reply->send_prefer)
                reply->prefer = reply->send_prefer;

        if (reply->valid > reply->send_valid)
                reply->valid = reply->send_valid;

#if 0
        /*
         * XXX: Old 4.0.0 alpha code would change the host {} record
         * XXX: uid upon lease assignment.  This was intended to cover the
         * XXX: case where a client first identifies itself using vendor
         * XXX: options in a solicit, or request, but later neglects to include
         * XXX: these options in a Renew or Rebind.  It is not clear that this
         * XXX: is required, and has some startling ramifications (such as
         * XXX: how to recover this dynamic host {} state across restarts).
         */
        if (reply->host != NULL)
                change_host_uid(host, reply->client_id->data,
                                reply->client_id->len);
#endif /* 0 */

        /* Perform dynamic lease related update work. */
        if (reply->lease != NULL) {
                /* Cached lifetimes */
                reply->lease->prefer = reply->send_prefer;
                reply->lease->valid = reply->send_valid;

                /* Advance (or rewind) the valid lifetime. */
                if (reply->buf.reply.msg_type == DHCPV6_REPLY) {
                        reply->lease->soft_lifetime_end_time =
                                cur_time + reply->send_valid;
                        /* Wait before renew! */
                }

                status = ia_add_iasubopt(reply->ia, reply->lease, MDL);
                if (status != ISC_R_SUCCESS) {
                        log_fatal("reply_process_is_addressed: Unable to "
                                  "attach lease to new IA: %s",
                                  isc_result_totext(status));
                }

                /*
                 * If this is a new lease, make sure it is attached somewhere.
                 */
                if (reply->lease->ia == NULL) {
                        ia_reference(&reply->lease->ia, reply->ia, MDL);
                }
        }

        /* Bring a copy of the relevant options into the IA scope. */
        execute_statements_in_scope(NULL, reply->packet, NULL, NULL,
                                    reply->packet->options, reply->reply_ia,
                                    scope, group, root_group, NULL);

        /*
         * And bring in host record configuration, if any, but not to overlap
         * the previous group or its common enclosers.
         */
        if (reply->host != NULL)
                execute_statements_in_scope(NULL, reply->packet, NULL, NULL,
                                            reply->packet->options,
                                            reply->reply_ia, scope,
                                            reply->host->group, group, NULL);

      cleanup:
        if (data.data != NULL)
                data_string_forget(&data, MDL);

        if (status == ISC_R_SUCCESS)
                reply->client_resources++;

        return status;
}

/* Simply send an IAADDR within the IA scope as described. */
static isc_result_t
reply_process_send_addr(struct reply_state *reply, struct iaddr *addr) {
        isc_result_t status = ISC_R_SUCCESS;
        struct data_string data;

        memset(&data, 0, sizeof(data));

        /* Now append the lease. */
        data.len = IAADDR_OFFSET;
        if (!buffer_allocate(&data.buffer, data.len, MDL)) {
                log_error("reply_process_send_addr: out of memory"
                          "allocating new IAADDR buffer.");
                status = ISC_R_NOMEMORY;
                goto cleanup;
        }
        data.data = data.buffer->data;

        memcpy(data.buffer->data, addr->iabuf, 16);
        putULong(data.buffer->data + 16, reply->send_prefer);
        putULong(data.buffer->data + 20, reply->send_valid);

        if (!append_option_buffer(&dhcpv6_universe, reply->reply_ia,
                                  data.buffer, data.buffer->data,
                                  data.len, D6O_IAADDR, 0)) {
                log_error("reply_process_send_addr: unable "
                          "to save IAADDR option");
                status = ISC_R_FAILURE;
                goto cleanup;
        }

        reply->resources_included = ISC_TRUE;

      cleanup:
        if (data.data != NULL)
                data_string_forget(&data, MDL);

        return status;
}

/* Choose the better of two leases. */
static struct iasubopt *
lease_compare(struct iasubopt *alpha, struct iasubopt *beta) {
        if (alpha == NULL)
                return beta;
        if (beta == NULL)
                return alpha;

        switch(alpha->state) {
              case FTS_ACTIVE:
                switch(beta->state) {
                      case FTS_ACTIVE:
                        /* Choose the lease with the longest lifetime (most
                         * likely the most recently allocated).
                         */
                        if (alpha->hard_lifetime_end_time < 
                            beta->hard_lifetime_end_time)
                                return beta;
                        else
                                return alpha;

                      case FTS_EXPIRED:
                      case FTS_ABANDONED:
                        return alpha;

                      default:
                        log_fatal("Impossible condition at %s:%d.", MDL);
                }
                break;

              case FTS_EXPIRED:
                switch (beta->state) {
                      case FTS_ACTIVE:
                        return beta;

                      case FTS_EXPIRED:
                        /* Choose the most recently expired lease. */
                        if (alpha->hard_lifetime_end_time <
                            beta->hard_lifetime_end_time)
                                return beta;
                        else if ((alpha->hard_lifetime_end_time ==
                                  beta->hard_lifetime_end_time) &&
                                 (alpha->soft_lifetime_end_time <
                                  beta->soft_lifetime_end_time))
                                return beta;
                        else
                                return alpha;

                      case FTS_ABANDONED:
                        return alpha;

                      default:
                        log_fatal("Impossible condition at %s:%d.", MDL);
                }
                break;

              case FTS_ABANDONED:
                switch (beta->state) {
                      case FTS_ACTIVE:
                      case FTS_EXPIRED:
                        return alpha;

                      case FTS_ABANDONED:
                        /* Choose the lease that was abandoned longest ago. */
                        if (alpha->hard_lifetime_end_time <
                            beta->hard_lifetime_end_time)
                                return alpha;

                      default:
                        log_fatal("Impossible condition at %s:%d.", MDL);
                }
                break;

              default:
                log_fatal("Impossible condition at %s:%d.", MDL);
        }

        log_fatal("Triple impossible condition at %s:%d.", MDL);
        return NULL;
}

/* Process a client-supplied IA_PD.  This may append options to the tail of
 * the reply packet being built in the reply_state structure.
 */
static isc_result_t
reply_process_ia_pd(struct reply_state *reply, struct option_cache *ia) {
        isc_result_t status = ISC_R_SUCCESS;
        u_int32_t iaid;
        unsigned ia_cursor;
        struct option_state *packet_ia;
        struct option_cache *oc;
        struct data_string ia_data, data;

        /* Initialize values that will get cleaned up on return. */
        packet_ia = NULL;
        memset(&ia_data, 0, sizeof(ia_data));
        memset(&data, 0, sizeof(data));
        /* 
         * Note that find_client_prefix() may set reply->lease.
         */

        /* Make sure there is at least room for the header. */
        if ((reply->cursor + IA_PD_OFFSET + 4) > sizeof(reply->buf)) {
                log_error("reply_process_ia_pd: Reply too long for IA.");
                return ISC_R_NOSPACE;
        }


        /* Fetch the IA_PD contents. */
        if (!get_encapsulated_IA_state(&packet_ia, &ia_data, reply->packet,
                                       ia, IA_PD_OFFSET)) {
                log_error("reply_process_ia_pd: error evaluating ia");
                status = ISC_R_FAILURE;
                goto cleanup;
        }

        /* Extract IA_PD header contents. */
        iaid = getULong(ia_data.data);
        reply->renew = getULong(ia_data.data + 4);
        reply->rebind = getULong(ia_data.data + 8);

        /* Create an IA_PD structure. */
        if (ia_allocate(&reply->ia, iaid, (char *)reply->client_id.data, 
                        reply->client_id.len, MDL) != ISC_R_SUCCESS) {
                log_error("reply_process_ia_pd: no memory for ia.");
                status = ISC_R_NOMEMORY;
                goto cleanup;
        }
        reply->ia->ia_type = D6O_IA_PD;

        /* Cache pre-existing IA_PD, if any. */
        ia_hash_lookup(&reply->old_ia, ia_pd_active,
                       (unsigned char *)reply->ia->iaid_duid.data,
                       reply->ia->iaid_duid.len, MDL);

        /*
         * Create an option cache to carry the IA_PD option contents, and
         * execute any user-supplied values into it.
         */
        if (!option_state_allocate(&reply->reply_ia, MDL)) {
                status = ISC_R_NOMEMORY;
                goto cleanup;
        }

        /* Check & count the fixed prefix host records. */
        reply->static_prefixes = 0;
        if ((reply->host != NULL) && (reply->host->fixed_prefix != NULL)) {
                struct iaddrcidrnetlist *fp;

                for (fp = reply->host->fixed_prefix; fp != NULL;
                     fp = fp->next) {
                        reply->static_prefixes += 1;
                }
        }

        /*
         * Save the cursor position at the start of the IA_PD, so we can
         * set length and adjust t1/t2 values later.  We write a temporary
         * header out now just in case we decide to adjust the packet
         * within sub-process functions.
         */
        ia_cursor = reply->cursor;

        /* Initialize the IA_PD header.  First the code. */
        putUShort(reply->buf.data + reply->cursor, (unsigned)D6O_IA_PD);
        reply->cursor += 2;

        /* Then option length. */
        putUShort(reply->buf.data + reply->cursor, 0x0Cu);
        reply->cursor += 2;

        /* Then IA_PD header contents; IAID. */
        putULong(reply->buf.data + reply->cursor, iaid);
        reply->cursor += 4;

        /* We store the client's t1 for now, and may over-ride it later. */
        putULong(reply->buf.data + reply->cursor, reply->renew);
        reply->cursor += 4;

        /* We store the client's t2 for now, and may over-ride it later. */
        putULong(reply->buf.data + reply->cursor, reply->rebind);
        reply->cursor += 4;

        /* 
         * For each prefix in this IA_PD, decide what to do about it.
         */
        oc = lookup_option(&dhcpv6_universe, packet_ia, D6O_IAPREFIX);
        reply->valid = reply->prefer = 0xffffffff;
        reply->client_valid = reply->client_prefer = 0;
        reply->preflen = -1;
        for (; oc != NULL ; oc = oc->next) {
                status = reply_process_prefix(reply, oc);

                /*
                 * Canceled means we did not allocate prefixes to the
                 * client, but we're "done" with this IA - we set a status
                 * code.  So transmit this reply, e.g., move on to the next
                 * IA.
                 */
                if (status == ISC_R_CANCELED)
                        break;

                if ((status != ISC_R_SUCCESS) &&
                    (status != ISC_R_ADDRINUSE) &&
                    (status != ISC_R_ADDRNOTAVAIL))
                        goto cleanup;
        }

        reply->pd_count++;

        /*
         * If we fell through the above and never gave the client
         * a prefix, give it one now.
         */
        if ((status != ISC_R_CANCELED) && (reply->client_resources == 0)) {
                status = find_client_prefix(reply);

                if (status == ISC_R_NORESOURCES) {
                        switch (reply->packet->dhcpv6_msg_type) {
                              case DHCPV6_SOLICIT:
                                /*
                                 * No prefix for any IA is handled
                                 * by the caller.
                                 */
                                /* FALL THROUGH */

                              case DHCPV6_REQUEST:
                                /* Same than for addresses. */
                                option_state_dereference(&reply->reply_ia, MDL);
                                if (!option_state_allocate(&reply->reply_ia,
                                                           MDL))
                                {
                                        log_error("reply_process_ia_pd: No "
                                                  "memory for option state "
                                                  "wipe.");
                                        status = ISC_R_NOMEMORY;
                                        goto cleanup;
                                }

                                if (!set_status_code(STATUS_NoPrefixAvail,
                                                     "No prefixes available "
                                                     "for this interface.",
                                                      reply->reply_ia)) {
                                        log_error("reply_process_ia_pd: "
                                                  "Unable to set "
                                                  "NoPrefixAvail status "
                                                  "code.");
                                        status = ISC_R_FAILURE;
                                        goto cleanup;
                                }

                                status = ISC_R_SUCCESS;
                                break;

                              default:
                                if (reply->resources_included)
                                        status = ISC_R_SUCCESS;
                                else
                                        goto cleanup;
                                break;
                        }
                }

                if (status != ISC_R_SUCCESS)
                        goto cleanup;
        }

        reply->cursor += store_options6((char *)reply->buf.data + reply->cursor,
                                        sizeof(reply->buf) - reply->cursor,
                                        reply->reply_ia, reply->packet,
                                        required_opts_IA_PD, NULL);

        /* Reset the length of this IA_PD to match what was just written. */
        putUShort(reply->buf.data + ia_cursor + 2,
                  reply->cursor - (ia_cursor + 4));

        /*
         * T1/T2 time selection is kind of weird.  We actually use DHCP
         * (v4) scoped options as handy existing places where these might
         * be configured by an administrator.  A value of zero tells the
         * client it may choose its own renewal time.
         */
        reply->renew = 0;
        oc = lookup_option(&dhcp_universe, reply->opt_state,
                           DHO_DHCP_RENEWAL_TIME);
        if (oc != NULL) {
                if (!evaluate_option_cache(&data, reply->packet, NULL, NULL,
                                           reply->packet->options,
                                           reply->opt_state, &global_scope,
                                           oc, MDL) ||
                    (data.len != 4)) {
                        log_error("Invalid renewal time.");
                } else {
                        reply->renew = getULong(data.data);
                }

                if (data.data != NULL)
                        data_string_forget(&data, MDL);
        }
        putULong(reply->buf.data + ia_cursor + 8, reply->renew);

        /* Now T2. */
        reply->rebind = 0;
        oc = lookup_option(&dhcp_universe, reply->opt_state,
                           DHO_DHCP_REBINDING_TIME);
        if (oc != NULL) {
                if (!evaluate_option_cache(&data, reply->packet, NULL, NULL,
                                           reply->packet->options,
                                           reply->opt_state, &global_scope,
                                           oc, MDL) ||
                    (data.len != 4)) {
                        log_error("Invalid rebinding time.");
                } else {
                        reply->rebind = getULong(data.data);
                }

                if (data.data != NULL)
                        data_string_forget(&data, MDL);
        }
        putULong(reply->buf.data + ia_cursor + 12, reply->rebind);

        /*
         * If this is not a 'soft' binding, consume the new changes into
         * the database (if any have been attached to the ia_pd).
         *
         * Loop through the assigned dynamic prefixes, referencing the
         * prefixes onto this IA_PD rather than any old ones, and updating
         * prefix pool timers for each (if any).
         */
        if ((status != ISC_R_CANCELED) && (reply->static_prefixes == 0) &&
            (reply->buf.reply.msg_type == DHCPV6_REPLY) &&
            (reply->ia->num_iasubopt != 0)) {
                struct iasubopt *tmp;
                struct data_string *ia_id;
                int i;

                for (i = 0 ; i < reply->ia->num_iasubopt ; i++) {
                        tmp = reply->ia->iasubopt[i];

                        if (tmp->ia != NULL)
                                ia_dereference(&tmp->ia, MDL);
                        ia_reference(&tmp->ia, reply->ia, MDL);

                        /* Commit 'hard' bindings. */
                        renew_lease6(tmp->ipv6_pool, tmp);
                        schedule_lease_timeout(tmp->ipv6_pool);

                        /* If we have anything to do on commit do it now */
                        if (tmp->on_star.on_commit != NULL) {
                                execute_statements(NULL, reply->packet,
                                                   NULL, NULL, 
                                                   reply->packet->options,
                                                   reply->opt_state,
                                                   &reply->lease->scope,
                                                   tmp->on_star.on_commit,
                                                   &tmp->on_star);
                                executable_statement_dereference
                                        (&tmp->on_star.on_commit, MDL);
                        }
                }

                /* Remove any old ia from the hash. */
                if (reply->old_ia != NULL) {
                        ia_id = &reply->old_ia->iaid_duid;
                        ia_hash_delete(ia_pd_active,
                                       (unsigned char *)ia_id->data,
                                       ia_id->len, MDL);
                        ia_dereference(&reply->old_ia, MDL);
                }

                /* Put new ia into the hash. */
                reply->ia->cltt = cur_time;
                ia_id = &reply->ia->iaid_duid;
                ia_hash_add(ia_pd_active, (unsigned char *)ia_id->data,
                            ia_id->len, reply->ia, MDL);

                write_ia(reply->ia);
        }

        /*
         * If this would be a hard binding for a static lease
         * run any commit statements that we have
         */
        if ((status != ISC_R_CANCELED) && reply->static_prefixes != 0 &&
            (reply->buf.reply.msg_type == DHCPV6_REPLY) &&
            (reply->on_star.on_commit != NULL)) {
                execute_statements(NULL, reply->packet, NULL, NULL, 
                                   reply->packet->options, reply->opt_state,
                                   NULL, reply->on_star.on_commit, NULL);
                executable_statement_dereference
                        (&reply->on_star.on_commit, MDL);
        }

      cleanup:
        if (packet_ia != NULL)
                option_state_dereference(&packet_ia, MDL);
        if (reply->reply_ia != NULL)
                option_state_dereference(&reply->reply_ia, MDL);
        if (ia_data.data != NULL)
                data_string_forget(&ia_data, MDL);
        if (data.data != NULL)
                data_string_forget(&data, MDL);
        if (reply->ia != NULL)
                ia_dereference(&reply->ia, MDL);
        if (reply->old_ia != NULL)
                ia_dereference(&reply->old_ia, MDL);
        if (reply->lease != NULL)
                iasubopt_dereference(&reply->lease, MDL);
        if (reply->on_star.on_expiry != NULL)
                executable_statement_dereference
                        (&reply->on_star.on_expiry, MDL);
        if (reply->on_star.on_release != NULL)
                executable_statement_dereference
                        (&reply->on_star.on_release, MDL);

        /*
         * ISC_R_CANCELED is a status code used by the prefix processing to
         * indicate we're replying with a status code.  This is still a
         * success at higher layers.
         */
        return((status == ISC_R_CANCELED) ? ISC_R_SUCCESS : status);
}

/*
 * Process an IAPREFIX within a given IA_PD, storing any IAPREFIX reply
 * contents into the reply's current ia_pd-scoped option cache.  Returns
 * ISC_R_CANCELED in the event we are replying with a status code and do
 * not wish to process more IAPREFIXes within this IA_PD.
 */
static isc_result_t
reply_process_prefix(struct reply_state *reply, struct option_cache *pref) {
        u_int32_t pref_life, valid_life;
        struct binding_scope **scope;
        struct iaddrcidrnet tmp_pref;
        struct option_cache *oc;
        struct data_string iapref, data;
        isc_result_t status = ISC_R_SUCCESS;

        /* Initializes values that will be cleaned up. */
        memset(&iapref, 0, sizeof(iapref));
        memset(&data, 0, sizeof(data));
        /* Note that reply->lease may be set by prefix_is_owned() */

        /*
         * There is no point trying to process an incoming prefix if there
         * is no room for an outgoing prefix.
         */
        if ((reply->cursor + 29) > sizeof(reply->buf)) {
                log_error("reply_process_prefix: Out of room for prefix.");
                return ISC_R_NOSPACE;
        }

        /* Extract this IAPREFIX option. */
        if (!evaluate_option_cache(&iapref, reply->packet, NULL, NULL, 
                                   reply->packet->options, NULL, &global_scope,
                                   pref, MDL) ||
            (iapref.len < IAPREFIX_OFFSET)) {
                log_error("reply_process_prefix: error evaluating IAPREFIX.");
                status = ISC_R_FAILURE;
                goto cleanup;
        }

        /*
         * Layout: preferred and valid lifetimes followed by the prefix
         * length and the IPv6 address.
         */
        pref_life = getULong(iapref.data);
        valid_life = getULong(iapref.data + 4);

        if ((reply->client_valid == 0) ||
            (reply->client_valid > valid_life))
                reply->client_valid = valid_life;

        if ((reply->client_prefer == 0) ||
            (reply->client_prefer > pref_life))
                reply->client_prefer = pref_life;

        /* 
         * Clients may choose to send ::/0 as a prefix, with the idea to give
         * hints about preferred-lifetime or valid-lifetime.
         */
        tmp_pref.lo_addr.len = 16;
        memset(tmp_pref.lo_addr.iabuf, 0, 16);
        if ((iapref.data[8] == 0) &&
            (memcmp(iapref.data + 9, tmp_pref.lo_addr.iabuf, 16) == 0)) {
                /* Status remains success; we just ignore this one. */
                goto cleanup;
        }

        /*
         * Clients may choose to send ::/X as a prefix to specify a
         * preferred/requested prefix length. Note X is never zero here.
         */
        tmp_pref.bits = (int) iapref.data[8];
        if (reply->preflen < 0) {
                /* Cache the first preferred prefix length. */
                reply->preflen = tmp_pref.bits;
        }
        if (memcmp(iapref.data + 9, tmp_pref.lo_addr.iabuf, 16) == 0) {
                goto cleanup;
        }

        memcpy(tmp_pref.lo_addr.iabuf, iapref.data + 9, 16);

        /* Verify the prefix belongs to the client. */
        if (!prefix_is_owned(reply, &tmp_pref)) {
                /* Same than for addresses. */
                if ((reply->packet->dhcpv6_msg_type == DHCPV6_SOLICIT) ||
                    (reply->packet->dhcpv6_msg_type == DHCPV6_REQUEST) ||
                    (reply->packet->dhcpv6_msg_type == DHCPV6_REBIND)) {
                        status = reply_process_try_prefix(reply, &tmp_pref);

                        /* Either error out or skip this prefix. */
                        if ((status != ISC_R_SUCCESS) &&
                            (status != ISC_R_ADDRINUSE) &&
                            (status != ISC_R_ADDRNOTAVAIL))
                                goto cleanup;

                        if (reply->lease == NULL) {
                                if (reply->packet->dhcpv6_msg_type ==
                                                        DHCPV6_REBIND) {
                                        reply->send_prefer = 0;
                                        reply->send_valid = 0;
                                        goto send_pref;
                                }

                                /* status remains success - ignore */
                                goto cleanup;
                        }
                /*
                 * RFC3633 section 18.2.3:
                 *
                 * If the delegating router cannot find a binding
                 * for the requesting router's IA_PD the delegating
                 * router returns the IA_PD containing no prefixes
                 * with a Status Code option set to NoBinding in the
                 * Reply message.
                 *
                 * On mismatch we (ab)use this pretending we have not the IA
                 * as soon as we have not a prefix.
                 */
                } else if (reply->packet->dhcpv6_msg_type == DHCPV6_RENEW) {
                        /* Rewind the IA_PD to empty. */
                        option_state_dereference(&reply->reply_ia, MDL);
                        if (!option_state_allocate(&reply->reply_ia, MDL)) {
                                log_error("reply_process_prefix: No memory "
                                          "for option state wipe.");
                                status = ISC_R_NOMEMORY;
                                goto cleanup;
                        }

                        /* Append a NoBinding status code.  */
                        if (!set_status_code(STATUS_NoBinding,
                                             "Prefix not bound to this "
                                             "interface.", reply->reply_ia)) {
                                log_error("reply_process_prefix: Unable to "
                                          "attach status code.");
                                status = ISC_R_FAILURE;
                                goto cleanup;
                        }

                        /* Fin (no more IAPREFIXes). */
                        status = ISC_R_CANCELED;
                        goto cleanup;
                } else {
                        log_error("It is impossible to lease a client that is "
                                  "not sending a solicit, request, renew, or "
                                  "rebind message.");
                        status = ISC_R_FAILURE;
                        goto cleanup;
                }
        }

        if (reply->static_prefixes > 0) {
                if (reply->host == NULL)
                        log_fatal("Impossible condition at %s:%d.", MDL);

                scope = &global_scope;
        } else {
                if (reply->lease == NULL)
                        log_fatal("Impossible condition at %s:%d.", MDL);

                scope = &reply->lease->scope;
        }

        /*
         * If client_resources is nonzero, then the reply_process_is_prefixed
         * function has executed configuration state into the reply option
         * cache.  We will use that valid cache to derive configuration for
         * whether or not to engage in additional prefixes, and similar.
         */
        if (reply->client_resources != 0) {
                unsigned limit = 1;

                /*
                 * Does this client have "enough" prefixes already?  Default
                 * to one.  Everybody gets one, and one should be enough for
                 * anybody.
                 */
                oc = lookup_option(&server_universe, reply->opt_state,
                                   SV_LIMIT_PREFS_PER_IA);
                if (oc != NULL) {
                        if (!evaluate_option_cache(&data, reply->packet,
                                                   NULL, NULL,
                                                   reply->packet->options,
                                                   reply->opt_state,
                                                   scope, oc, MDL) ||
                            (data.len != 4)) {
                                log_error("reply_process_prefix: unable to "
                                          "evaluate prefs-per-ia value.");
                                status = ISC_R_FAILURE;
                                goto cleanup;
                        }

                        limit = getULong(data.data);
                        data_string_forget(&data, MDL);
                }

                /*
                 * If we wish to limit the client to a certain number of
                 * prefixes, then omit the prefix from the reply.
                 */
                if (reply->client_resources >= limit)
                        goto cleanup;
        }

        status = reply_process_is_prefixed(reply, scope, reply->shared->group);
        if (status != ISC_R_SUCCESS)
                goto cleanup;

      send_pref:
        status = reply_process_send_prefix(reply, &tmp_pref);

      cleanup:
        if (iapref.data != NULL)
                data_string_forget(&iapref, MDL);
        if (data.data != NULL)
                data_string_forget(&data, MDL);
        if (reply->lease != NULL)
                iasubopt_dereference(&reply->lease, MDL);

        return status;
}

/*
 * Verify the prefix belongs to the client.  If we've got a host
 * record with fixed prefixes, it has to be an assigned prefix
 * (fault out all else).  Otherwise it's a dynamic prefix, so lookup
 * that prefix and make sure it belongs to this DUID:IAID pair.
 */
static isc_boolean_t
prefix_is_owned(struct reply_state *reply, struct iaddrcidrnet *pref) {
        struct iaddrcidrnetlist *l;
        int i;

        /*
         * This faults out prefixes that don't match fixed prefixes.
         */
        if (reply->static_prefixes > 0) {
                for (l = reply->host->fixed_prefix; l != NULL; l = l->next) {
                        if ((pref->bits == l->cidrnet.bits) &&
                            (memcmp(pref->lo_addr.iabuf,
                                    l->cidrnet.lo_addr.iabuf, 16) == 0))
                                return (ISC_TRUE);
                }
                return (ISC_FALSE);
        }

        if ((reply->old_ia == NULL) ||
            (reply->old_ia->num_iasubopt == 0))
                return (ISC_FALSE);

        for (i = 0 ; i < reply->old_ia->num_iasubopt ; i++) {
                struct iasubopt *tmp;

                tmp = reply->old_ia->iasubopt[i];

                if ((pref->bits == (int) tmp->plen) &&
                    (memcmp(pref->lo_addr.iabuf, &tmp->addr, 16) == 0)) {
                        if (lease6_usable(tmp) == ISC_FALSE) {
                                return (ISC_FALSE);
                        }
                        iasubopt_reference(&reply->lease, tmp, MDL);
                        return (ISC_TRUE);
                }
        }

        return (ISC_FALSE);
}

/*
 * This function only returns failure on 'hard' failures.  If it succeeds,
 * it will leave a prefix structure behind.
 */
static isc_result_t
reply_process_try_prefix(struct reply_state *reply,
                         struct iaddrcidrnet *pref) {
        isc_result_t status = ISC_R_ADDRNOTAVAIL;
        struct ipv6_pool *pool;
        int i;
        struct data_string data_pref;

        if ((reply == NULL) || (reply->shared == NULL) ||
            (pref == NULL) || (reply->lease != NULL))
                return (DHCP_R_INVALIDARG);

        if (reply->shared->ipv6_pools == NULL)
                return (ISC_R_ADDRNOTAVAIL);

        memset(&data_pref, 0, sizeof(data_pref));
        data_pref.len = 17;
        if (!buffer_allocate(&data_pref.buffer, data_pref.len, MDL)) {
                log_error("reply_process_try_prefix: out of memory.");
                return (ISC_R_NOMEMORY);
        }
        data_pref.data = data_pref.buffer->data;
        data_pref.buffer->data[0] = (u_int8_t) pref->bits;
        memcpy(data_pref.buffer->data + 1, pref->lo_addr.iabuf, 16);

        for (i = 0 ; (pool = reply->shared->ipv6_pools[i]) != NULL ; i++) {
                if (pool->pool_type != D6O_IA_PD)
                        continue;
                status = try_client_v6_prefix(&reply->lease, pool,
                                              &data_pref);
                /* If we found it in this pool (either in use or available), 
                   there is no need to look further. */
                if ( (status == ISC_R_SUCCESS) || (status == ISC_R_ADDRINUSE) )
                        break;
        }

        data_string_forget(&data_pref, MDL);
        /* Return just the most recent status... */
        return (status);
}

/* Look around for a prefix to give the client.  First, look through the old
 * IA_PD for prefixes we can extend.  Second, try to allocate a new prefix.
 * Finally, actually add that prefix into the current reply IA_PD.
 */
static isc_result_t
find_client_prefix(struct reply_state *reply) {
        struct iaddrcidrnet send_pref;
        isc_result_t status = ISC_R_NORESOURCES;
        struct iasubopt *prefix, *best_prefix = NULL;
        struct binding_scope **scope;
        int i;

        if (reply->static_prefixes > 0) {
                struct iaddrcidrnetlist *l;

                if (reply->host == NULL)
                        return DHCP_R_INVALIDARG;

                for (l = reply->host->fixed_prefix; l != NULL; l = l->next) {
                        if (l->cidrnet.bits == reply->preflen)
                                break;
                }
                if (l == NULL) {
                        /*
                         * If no fixed prefix has the preferred length,
                         * get the first one.
                         */
                        l = reply->host->fixed_prefix;
                }
                memcpy(&send_pref, &l->cidrnet, sizeof(send_pref));

                scope = &global_scope;
                goto send_pref;
        }

        if (reply->old_ia != NULL)  {
                for (i = 0 ; i < reply->old_ia->num_iasubopt ; i++) {
                        struct shared_network *candidate_shared;

                        prefix = reply->old_ia->iasubopt[i];
                        candidate_shared = prefix->ipv6_pool->shared_network;

                        /*
                         * Consider this prefix if it is in a global pool or
                         * if it is scoped in a pool under the client's shared
                         * network.
                         */
                        if (((candidate_shared == NULL) ||
                             (candidate_shared == reply->shared)) &&
                            (lease6_usable(prefix) == ISC_TRUE)) {
                                best_prefix = prefix_compare(reply, prefix,
                                                             best_prefix);
                        }
                }
        }

        /* Try to pick a new prefix if we didn't find one, or if we found an
         * abandoned prefix.
         */
        if ((best_prefix == NULL) || (best_prefix->state == FTS_ABANDONED)) {
                status = pick_v6_prefix(&reply->lease, reply->preflen,
                                        reply->shared, &reply->client_id);
        } else if (best_prefix != NULL) {
                iasubopt_reference(&reply->lease, best_prefix, MDL);
                status = ISC_R_SUCCESS;
        }

        /* Pick the abandoned prefix as a last resort. */
        if ((status == ISC_R_NORESOURCES) && (best_prefix != NULL)) {
                /* I don't see how this is supposed to be done right now. */
                log_error("Reclaiming abandoned prefixes is not yet "
                          "supported.  Treating this as an out of space "
                          "condition.");
                /* iasubopt_reference(&reply->lease, best_prefix, MDL); */
        }

        /* Give up now if we didn't find a prefix. */
        if (status != ISC_R_SUCCESS)
                return status;

        if (reply->lease == NULL)
                log_fatal("Impossible condition at %s:%d.", MDL);

        scope = &reply->lease->scope;

        send_pref.lo_addr.len = 16;
        memcpy(send_pref.lo_addr.iabuf, &reply->lease->addr, 16);
        send_pref.bits = (int) reply->lease->plen;

      send_pref:
        status = reply_process_is_prefixed(reply, scope, reply->shared->group);
        if (status != ISC_R_SUCCESS)
                return status;

        status = reply_process_send_prefix(reply, &send_pref);
        return status;
}

/* Once a prefix is found for a client, perform several common functions;
 * Calculate and store valid and preferred prefix times, draw client options
 * into the option state.
 */
static isc_result_t
reply_process_is_prefixed(struct reply_state *reply,
                          struct binding_scope **scope, struct group *group)
{
        isc_result_t status = ISC_R_SUCCESS;
        struct data_string data;
        struct option_cache *oc;
        struct option_state *tmp_options = NULL;
        struct on_star *on_star;

        /* Initialize values we will cleanup. */
        memset(&data, 0, sizeof(data));

        /*
         * Find the proper on_star block to use.  We use the
         * one in the lease if we have a lease or the one in
         * the reply if we don't have a lease because this is
         * a static instance
         */
        if (reply->lease) {
                on_star = &reply->lease->on_star;
        } else {
                on_star = &reply->on_star;
        }

        /*
         * Bring in the root configuration.  We only do this to bring
         * in the on * statements, as we didn't have the lease available
         * we we did it the first time.
         */
        option_state_allocate(&tmp_options, MDL);
        execute_statements_in_scope(NULL, reply->packet, NULL, NULL,
                                    reply->packet->options, tmp_options,
                                    &global_scope, root_group, NULL,
                                    on_star);
        if (tmp_options != NULL) {
                option_state_dereference(&tmp_options, MDL);
        }

        /*
         * Bring configured options into the root packet level cache - start
         * with the lease's closest enclosing group (passed in by the caller
         * as 'group').
         */
        execute_statements_in_scope(NULL, reply->packet, NULL, NULL,
                                    reply->packet->options, reply->opt_state,
                                    scope, group, root_group, on_star);

        /*
         * If there is a host record, over-ride with values configured there,
         * without re-evaluating configuration from the previously executed
         * group or its common enclosers.
         */
        if (reply->host != NULL)
                execute_statements_in_scope(NULL, reply->packet, NULL, NULL,
                                            reply->packet->options,
                                            reply->opt_state, scope,
                                            reply->host->group, group,
                                            on_star);

        /* Determine valid lifetime. */
        if (reply->client_valid == 0)
                reply->send_valid = DEFAULT_DEFAULT_LEASE_TIME;
        else
                reply->send_valid = reply->client_valid;

        oc = lookup_option(&server_universe, reply->opt_state,
                           SV_DEFAULT_LEASE_TIME);
        if (oc != NULL) {
                if (!evaluate_option_cache(&data, reply->packet, NULL, NULL,
                                           reply->packet->options,
                                           reply->opt_state,
                                           scope, oc, MDL) ||
                    (data.len != 4)) {
                        log_error("reply_process_is_prefixed: unable to "
                                  "evaluate default prefix time");
                        status = ISC_R_FAILURE;
                        goto cleanup;
                }

                reply->send_valid = getULong(data.data);
                data_string_forget(&data, MDL);
        }

        if (reply->client_prefer == 0)
                reply->send_prefer = reply->send_valid;
        else
                reply->send_prefer = reply->client_prefer;

        if (reply->send_prefer >= reply->send_valid)
                reply->send_prefer = (reply->send_valid / 2) +
                                     (reply->send_valid / 8);

        oc = lookup_option(&server_universe, reply->opt_state,
                           SV_PREFER_LIFETIME);
        if (oc != NULL) {
                if (!evaluate_option_cache(&data, reply->packet, NULL, NULL,
                                           reply->packet->options,
                                           reply->opt_state,
                                           scope, oc, MDL) ||
                    (data.len != 4)) {
                        log_error("reply_process_is_prefixed: unable to "
                                  "evaluate preferred prefix time");
                        status = ISC_R_FAILURE;
                        goto cleanup;
                }

                reply->send_prefer = getULong(data.data);
                data_string_forget(&data, MDL);
        }

        /* Note lowest values for later calculation of renew/rebind times. */
        if (reply->prefer > reply->send_prefer)
                reply->prefer = reply->send_prefer;

        if (reply->valid > reply->send_valid)
                reply->valid = reply->send_valid;

        /* Perform dynamic prefix related update work. */
        if (reply->lease != NULL) {
                /* Cached lifetimes */
                reply->lease->prefer = reply->send_prefer;
                reply->lease->valid = reply->send_valid;

                /* Advance (or rewind) the valid lifetime. */
                if (reply->buf.reply.msg_type == DHCPV6_REPLY) {
                        reply->lease->soft_lifetime_end_time =
                                cur_time + reply->send_valid;
                        /* Wait before renew! */
                }

                status = ia_add_iasubopt(reply->ia, reply->lease, MDL);
                if (status != ISC_R_SUCCESS) {
                        log_fatal("reply_process_is_prefixed: Unable to "
                                  "attach prefix to new IA_PD: %s",
                                  isc_result_totext(status));
                }

                /*
                 * If this is a new prefix, make sure it is attached somewhere.
                 */
                if (reply->lease->ia == NULL) {
                        ia_reference(&reply->lease->ia, reply->ia, MDL);
                }
        }

        /* Bring a copy of the relevant options into the IA_PD scope. */
        execute_statements_in_scope(NULL, reply->packet, NULL, NULL,
                                    reply->packet->options, reply->reply_ia,
                                    scope, group, root_group, NULL);

        /*
         * And bring in host record configuration, if any, but not to overlap
         * the previous group or its common enclosers.
         */
        if (reply->host != NULL)
                execute_statements_in_scope(NULL, reply->packet, NULL, NULL,
                                            reply->packet->options,
                                            reply->reply_ia, scope,
                                            reply->host->group, group, NULL);

      cleanup:
        if (data.data != NULL)
                data_string_forget(&data, MDL);

        if (status == ISC_R_SUCCESS)
                reply->client_resources++;

        return status;
}

/* Simply send an IAPREFIX within the IA_PD scope as described. */
static isc_result_t
reply_process_send_prefix(struct reply_state *reply,
                          struct iaddrcidrnet *pref) {
        isc_result_t status = ISC_R_SUCCESS;
        struct data_string data;

        memset(&data, 0, sizeof(data));

        /* Now append the prefix. */
        data.len = IAPREFIX_OFFSET;
        if (!buffer_allocate(&data.buffer, data.len, MDL)) {
                log_error("reply_process_send_prefix: out of memory"
                          "allocating new IAPREFIX buffer.");
                status = ISC_R_NOMEMORY;
                goto cleanup;
        }
        data.data = data.buffer->data;

        putULong(data.buffer->data, reply->send_prefer);
        putULong(data.buffer->data + 4, reply->send_valid);
        data.buffer->data[8] = pref->bits;
        memcpy(data.buffer->data + 9, pref->lo_addr.iabuf, 16);

        if (!append_option_buffer(&dhcpv6_universe, reply->reply_ia,
                                  data.buffer, data.buffer->data,
                                  data.len, D6O_IAPREFIX, 0)) {
                log_error("reply_process_send_prefix: unable "
                          "to save IAPREFIX option");
                status = ISC_R_FAILURE;
                goto cleanup;
        }

        reply->resources_included = ISC_TRUE;

      cleanup:
        if (data.data != NULL)
                data_string_forget(&data, MDL);

        return status;
}

/* Choose the better of two prefixes. */
static struct iasubopt *
prefix_compare(struct reply_state *reply,
               struct iasubopt *alpha, struct iasubopt *beta) {
        if (alpha == NULL)
                return beta;
        if (beta == NULL)
                return alpha;

        if (reply->preflen >= 0) {
                if ((alpha->plen == reply->preflen) &&
                    (beta->plen != reply->preflen))
                        return alpha;
                if ((beta->plen == reply->preflen) &&
                    (alpha->plen != reply->preflen))
                        return beta;
        }

        switch(alpha->state) {
              case FTS_ACTIVE:
                switch(beta->state) {
                      case FTS_ACTIVE:
                        /* Choose the prefix with the longest lifetime (most
                         * likely the most recently allocated).
                         */
                        if (alpha->hard_lifetime_end_time < 
                            beta->hard_lifetime_end_time)
                                return beta;
                        else
                                return alpha;

                      case FTS_EXPIRED:
                      case FTS_ABANDONED:
                        return alpha;

                      default:
                        log_fatal("Impossible condition at %s:%d.", MDL);
                }
                break;

              case FTS_EXPIRED:
                switch (beta->state) {
                      case FTS_ACTIVE:
                        return beta;

                      case FTS_EXPIRED:
                        /* Choose the most recently expired prefix. */
                        if (alpha->hard_lifetime_end_time <
                            beta->hard_lifetime_end_time)
                                return beta;
                        else if ((alpha->hard_lifetime_end_time ==
                                  beta->hard_lifetime_end_time) &&
                                 (alpha->soft_lifetime_end_time <
                                  beta->soft_lifetime_end_time))
                                return beta;
                        else
                                return alpha;

                      case FTS_ABANDONED:
                        return alpha;

                      default:
                        log_fatal("Impossible condition at %s:%d.", MDL);
                }
                break;

              case FTS_ABANDONED:
                switch (beta->state) {
                      case FTS_ACTIVE:
                      case FTS_EXPIRED:
                        return alpha;

                      case FTS_ABANDONED:
                        /* Choose the prefix that was abandoned longest ago. */
                        if (alpha->hard_lifetime_end_time <
                            beta->hard_lifetime_end_time)
                                return alpha;

                      default:
                        log_fatal("Impossible condition at %s:%d.", MDL);
                }
                break;

              default:
                log_fatal("Impossible condition at %s:%d.", MDL);
        }

        log_fatal("Triple impossible condition at %s:%d.", MDL);
        return NULL;
}

/*
 * Solicit is how a client starts requesting addresses.
 *
 * If the client asks for rapid commit, and we support it, we will 
 * allocate the addresses and reply.
 *
 * Otherwise we will send an advertise message.
 */

static void
dhcpv6_solicit(struct data_string *reply_ret, struct packet *packet) {
        struct data_string client_id;

        /* 
         * Validate our input.
         */
        if (!valid_client_msg(packet, &client_id)) {
                return;
        }

        lease_to_client(reply_ret, packet, &client_id, NULL);

        /*
         * Clean up.
         */
        data_string_forget(&client_id, MDL);
}

/*
 * Request is how a client actually requests addresses.
 *
 * Very similar to Solicit handling, except the server DUID is required.
 */

/* TODO: reject unicast messages, unless we set unicast option */
static void
dhcpv6_request(struct data_string *reply_ret, struct packet *packet) {
        struct data_string client_id;
        struct data_string server_id;

        /*
         * Validate our input.
         */
        if (!valid_client_resp(packet, &client_id, &server_id)) {
                return;
        }

        /*
         * Issue our lease.
         */
        lease_to_client(reply_ret, packet, &client_id, &server_id);

        /*
         * Cleanup.
         */
        data_string_forget(&client_id, MDL);
        data_string_forget(&server_id, MDL);
}

/* Find a DHCPv6 packet's shared network from hints in the packet.
 */
static isc_result_t
shared_network_from_packet6(struct shared_network **shared,
                            struct packet *packet)
{
        const struct packet *chk_packet;
        const struct in6_addr *link_addr, *first_link_addr;
        struct iaddr tmp_addr;
        struct subnet *subnet;
        isc_result_t status;

        if ((shared == NULL) || (*shared != NULL) || (packet == NULL))
                return DHCP_R_INVALIDARG;

        /*
         * First, find the link address where the packet from the client
         * first appeared (if this packet was relayed).
         */
        first_link_addr = NULL;
        chk_packet = packet->dhcpv6_container_packet;
        while (chk_packet != NULL) {
                link_addr = &chk_packet->dhcpv6_link_address;
                if (!IN6_IS_ADDR_UNSPECIFIED(link_addr) &&
                    !IN6_IS_ADDR_LINKLOCAL(link_addr)) {
                        first_link_addr = link_addr;
                        break;
                }
                chk_packet = chk_packet->dhcpv6_container_packet;
        }

        /*
         * If there is a relayed link address, find the subnet associated
         * with that, and use that to get the appropriate
         * shared_network.
         */
        if (first_link_addr != NULL) {
                tmp_addr.len = sizeof(*first_link_addr);
                memcpy(tmp_addr.iabuf,
                       first_link_addr, sizeof(*first_link_addr));
                subnet = NULL;
                if (!find_subnet(&subnet, tmp_addr, MDL)) {
                        log_debug("No subnet found for link-address %s.",
                                  piaddr(tmp_addr));
                        return ISC_R_NOTFOUND;
                }
                status = shared_network_reference(shared,
                                                  subnet->shared_network, MDL);
                subnet_dereference(&subnet, MDL);

        /*
         * If there is no link address, we will use the interface
         * that this packet came in on to pick the shared_network.
         */
        } else if (packet->interface != NULL) {
                status = shared_network_reference(shared,
                                         packet->interface->shared_network,
                                         MDL);
                if (packet->dhcpv6_container_packet != NULL) {
                        log_info("[L2 Relay] No link address in relay packet "
                                 "assuming L2 relay and using receiving "
                                 "interface");
                }

        } else {
                /*
                 * We shouldn't be able to get here but if there is no link
                 * address and no interface we don't know where to get the
                 * pool from log an error and return an error.
                 */
                log_error("No interface and no link address " 
                          "can't determine pool");
                status = DHCP_R_INVALIDARG;
        }

        return status;
}

/*
 * When a client thinks it might be on a new link, it sends a 
 * Confirm message.
 *
 * From RFC3315 section 18.2.2:
 *
 *   When the server receives a Confirm message, the server determines
 *   whether the addresses in the Confirm message are appropriate for the
 *   link to which the client is attached.  If all of the addresses in the
 *   Confirm message pass this test, the server returns a status of
 *   Success.  If any of the addresses do not pass this test, the server
 *   returns a status of NotOnLink.  If the server is unable to perform
 *   this test (for example, the server does not have information about
 *   prefixes on the link to which the client is connected), or there were
 *   no addresses in any of the IAs sent by the client, the server MUST
 *   NOT send a reply to the client.
 */

static void
dhcpv6_confirm(struct data_string *reply_ret, struct packet *packet) {
        struct shared_network *shared;
        struct subnet *subnet;
        struct option_cache *ia, *ta, *oc;
        struct data_string cli_enc_opt_data, iaaddr, client_id, packet_oro;
        struct option_state *cli_enc_opt_state, *opt_state;
        struct iaddr cli_addr;
        int pass;
        isc_boolean_t inappropriate, has_addrs;
        char reply_data[65536];
        struct dhcpv6_packet *reply = (struct dhcpv6_packet *)reply_data;
        int reply_ofs = (int)(offsetof(struct dhcpv6_packet, options));

        /* 
         * Basic client message validation.
         */
        memset(&client_id, 0, sizeof(client_id));
        if (!valid_client_msg(packet, &client_id)) {
                return;
        }

        /*
         * Do not process Confirms that do not have IA's we do not recognize.
         */
        ia = lookup_option(&dhcpv6_universe, packet->options, D6O_IA_NA);
        ta = lookup_option(&dhcpv6_universe, packet->options, D6O_IA_TA);
        if ((ia == NULL) && (ta == NULL))
                return;

        /*
         * IA_PD's are simply ignored.
         */
        delete_option(&dhcpv6_universe, packet->options, D6O_IA_PD);

        /* 
         * Bit of variable initialization.
         */
        opt_state = cli_enc_opt_state = NULL;
        memset(&cli_enc_opt_data, 0, sizeof(cli_enc_opt_data));
        memset(&iaaddr, 0, sizeof(iaaddr));
        memset(&packet_oro, 0, sizeof(packet_oro));

        /* Determine what shared network the client is connected to.  We
         * must not respond if we don't have any information about the
         * network the client is on.
         */
        shared = NULL;
        if ((shared_network_from_packet6(&shared, packet) != ISC_R_SUCCESS) ||
            (shared == NULL))
                goto exit;

        /* If there are no recorded subnets, then we have no
         * information about this subnet - ignore Confirms.
         */
        subnet = shared->subnets;
        if (subnet == NULL)
                goto exit;

        /* Are the addresses in all the IA's appropriate for that link? */
        has_addrs = inappropriate = ISC_FALSE;
        pass = D6O_IA_NA;
        while(!inappropriate) {
                /* If we've reached the end of the IA_NA pass, move to the
                 * IA_TA pass.
                 */
                if ((pass == D6O_IA_NA) && (ia == NULL)) {
                        pass = D6O_IA_TA;
                        ia = ta;
                }

                /* If we've reached the end of all passes, we're done. */
                if (ia == NULL)
                        break;

                if (((pass == D6O_IA_NA) &&
                     !get_encapsulated_IA_state(&cli_enc_opt_state,
                                                &cli_enc_opt_data,
                                                packet, ia, IA_NA_OFFSET)) ||
                    ((pass == D6O_IA_TA) &&
                     !get_encapsulated_IA_state(&cli_enc_opt_state,
                                                &cli_enc_opt_data,
                                                packet, ia, IA_TA_OFFSET))) {
                        goto exit;
                }

                oc = lookup_option(&dhcpv6_universe, cli_enc_opt_state,
                                   D6O_IAADDR);

                for ( ; oc != NULL ; oc = oc->next) {
                        if (!evaluate_option_cache(&iaaddr, packet, NULL, NULL,
                                                   packet->options, NULL,
                                                   &global_scope, oc, MDL) ||
                            (iaaddr.len < IAADDR_OFFSET)) {
                                log_error("dhcpv6_confirm: "
                                          "error evaluating IAADDR.");
                                goto exit;
                        }

                        /* Copy out the IPv6 address for processing. */
                        cli_addr.len = 16;
                        memcpy(cli_addr.iabuf, iaaddr.data, 16);

                        data_string_forget(&iaaddr, MDL);

                        /* Record that we've processed at least one address. */
                        has_addrs = ISC_TRUE;

                        /* Find out if any subnets cover this address. */
                        for (subnet = shared->subnets ; subnet != NULL ;
                             subnet = subnet->next_sibling) {
                                if (addr_eq(subnet_number(cli_addr,
                                                          subnet->netmask),
                                            subnet->net))
                                        break;
                        }

                        /* If we reach the end of the subnet list, and no
                         * subnet matches the client address, then it must
                         * be inappropriate to the link (so far as our
                         * configuration says).  Once we've found one
                         * inappropriate address, there is no reason to
                         * continue searching.
                         */
                        if (subnet == NULL) {
                                inappropriate = ISC_TRUE;
                                break;
                        }
                }

                option_state_dereference(&cli_enc_opt_state, MDL);
                data_string_forget(&cli_enc_opt_data, MDL);

                /* Advance to the next IA_*. */
                ia = ia->next;
        }

        /* If the client supplied no addresses, do not reply. */
        if (!has_addrs)
                goto exit;

        /* 
         * Set up reply.
         */
        if (!start_reply(packet, &client_id, NULL, &opt_state, reply)) {
                goto exit;
        }

        /* 
         * Set our status.
         */
        if (inappropriate) {
                if (!set_status_code(STATUS_NotOnLink, 
                                     "Some of the addresses are not on link.",
                                     opt_state)) {
                        goto exit;
                }
        } else {
                if (!set_status_code(STATUS_Success, 
                                     "All addresses still on link.",
                                     opt_state)) {
                        goto exit;
                }
        }

        /* 
         * Only one option: add it.
         */
        reply_ofs += store_options6(reply_data+reply_ofs,
                                    sizeof(reply_data)-reply_ofs, 
                                    opt_state, packet,
                                    required_opts, &packet_oro);

        /* 
         * Return our reply to the caller.
         */
        reply_ret->len = reply_ofs;
        reply_ret->buffer = NULL;
        if (!buffer_allocate(&reply_ret->buffer, reply_ofs, MDL)) {
                log_fatal("No memory to store reply.");
        }
        reply_ret->data = reply_ret->buffer->data;
        memcpy(reply_ret->buffer->data, reply, reply_ofs);

exit:
        /* Cleanup any stale data strings. */
        if (cli_enc_opt_data.buffer != NULL)
                data_string_forget(&cli_enc_opt_data, MDL);
        if (iaaddr.buffer != NULL)
                data_string_forget(&iaaddr, MDL);
        if (client_id.buffer != NULL)
                data_string_forget(&client_id, MDL);
        if (packet_oro.buffer != NULL)
                data_string_forget(&packet_oro, MDL);

        /* Release any stale option states. */
        if (cli_enc_opt_state != NULL)
                option_state_dereference(&cli_enc_opt_state, MDL);
        if (opt_state != NULL)
                option_state_dereference(&opt_state, MDL);
}

/*
 * Renew is when a client wants to extend its lease/prefix, at time T1.
 *
 * We handle this the same as if the client wants a new lease/prefix,
 * except for the error code of when addresses don't match.
 */

/* TODO: reject unicast messages, unless we set unicast option */
static void
dhcpv6_renew(struct data_string *reply, struct packet *packet) {
        struct data_string client_id;
        struct data_string server_id;

        /* 
         * Validate the request.
         */
        if (!valid_client_resp(packet, &client_id, &server_id)) {
                return;
        }

        /*
         * Renew our lease.
         */
        lease_to_client(reply, packet, &client_id, &server_id);

        /*
         * Cleanup.
         */
        data_string_forget(&server_id, MDL);
        data_string_forget(&client_id, MDL);
}

/*
 * Rebind is when a client wants to extend its lease, at time T2.
 *
 * We handle this the same as if the client wants a new lease, except
 * for the error code of when addresses don't match.
 */

static void
dhcpv6_rebind(struct data_string *reply, struct packet *packet) {
        struct data_string client_id;

        if (!valid_client_msg(packet, &client_id)) {
                return;
        }

        lease_to_client(reply, packet, &client_id, NULL);

        data_string_forget(&client_id, MDL);
}

static void
ia_na_match_decline(const struct data_string *client_id,
                    const struct data_string *iaaddr,
                    struct iasubopt *lease)
{
        char tmp_addr[INET6_ADDRSTRLEN];

        log_error("Client %s reports address %s is "
                  "already in use by another host!",
                  print_hex_1(client_id->len, client_id->data, 60),
                  inet_ntop(AF_INET6, iaaddr->data, 
                            tmp_addr, sizeof(tmp_addr)));
        if (lease != NULL) {
                decline_lease6(lease->ipv6_pool, lease);
                lease->ia->cltt = cur_time;
                write_ia(lease->ia);
        }
}

static void
ia_na_nomatch_decline(const struct data_string *client_id,
                      const struct data_string *iaaddr,
                      u_int32_t *ia_na_id,
                      struct packet *packet,
                      char *reply_data,
                      int *reply_ofs,
                      int reply_len)
{
        char tmp_addr[INET6_ADDRSTRLEN];
        struct option_state *host_opt_state;
        int len;

        log_info("Client %s declines address %s, which is not offered to it.",
                 print_hex_1(client_id->len, client_id->data, 60),
                 inet_ntop(AF_INET6, iaaddr->data, tmp_addr, sizeof(tmp_addr)));

        /*
         * Create state for this IA_NA.
         */
        host_opt_state = NULL;
        if (!option_state_allocate(&host_opt_state, MDL)) {
                log_error("ia_na_nomatch_decline: out of memory "
                          "allocating option_state.");
                goto exit;
        }

        if (!set_status_code(STATUS_NoBinding, "Decline for unknown address.",
                             host_opt_state)) {
                goto exit;
        }

        /*
         * Insure we have enough space
         */
        if (reply_len < (*reply_ofs + 16)) {
                log_error("ia_na_nomatch_decline: "
                          "out of space for reply packet.");
                goto exit;
        }

        /*
         * Put our status code into the reply packet.
         */
        len = store_options6(reply_data+(*reply_ofs)+16,
                             reply_len-(*reply_ofs)-16,
                             host_opt_state, packet,
                             required_opts_STATUS_CODE, NULL);

        /*
         * Store the non-encapsulated option data for this 
         * IA_NA into our reply packet. Defined in RFC 3315, 
         * section 22.4.  
         */
        /* option number */
        putUShort((unsigned char *)reply_data+(*reply_ofs), D6O_IA_NA);
        /* option length */
        putUShort((unsigned char *)reply_data+(*reply_ofs)+2, len + 12);
        /* IA_NA, copied from the client */
        memcpy(reply_data+(*reply_ofs)+4, ia_na_id, 4);
        /* t1 and t2, odd that we need them, but here it is */
        putULong((unsigned char *)reply_data+(*reply_ofs)+8, 0);
        putULong((unsigned char *)reply_data+(*reply_ofs)+12, 0);

        /*
         * Get ready for next IA_NA.
         */
        *reply_ofs += (len + 16);

exit:
        option_state_dereference(&host_opt_state, MDL);
}

static void
iterate_over_ia_na(struct data_string *reply_ret, 
                   struct packet *packet,
                   const struct data_string *client_id,
                   const struct data_string *server_id,
                   const char *packet_type,
                   void (*ia_na_match)(),
                   void (*ia_na_nomatch)())
{
        struct option_state *opt_state;
        struct host_decl *packet_host;
        struct option_cache *ia;
        struct option_cache *oc;
        /* cli_enc_... variables come from the IA_NA/IA_TA options */
        struct data_string cli_enc_opt_data;
        struct option_state *cli_enc_opt_state;
        struct host_decl *host;
        struct option_state *host_opt_state;
        struct data_string iaaddr;
        struct data_string fixed_addr;
        char reply_data[65536];
        struct dhcpv6_packet *reply = (struct dhcpv6_packet *)reply_data;
        int reply_ofs = (int)(offsetof(struct dhcpv6_packet, options));
        char status_msg[32];
        struct iasubopt *lease;
        struct ia_xx *existing_ia_na;
        int i;
        struct data_string key;
        u_int32_t iaid;

        /*
         * Initialize to empty values, in case we have to exit early.
         */
        opt_state = NULL;
        memset(&cli_enc_opt_data, 0, sizeof(cli_enc_opt_data));
        cli_enc_opt_state = NULL;
        memset(&iaaddr, 0, sizeof(iaaddr));
        memset(&fixed_addr, 0, sizeof(fixed_addr));
        host_opt_state = NULL;
        lease = NULL;

        /* 
         * Find the host record that matches from the packet, if any.
         */
        packet_host = NULL;
        if (!find_hosts_by_uid(&packet_host, 
                               client_id->data, client_id->len, MDL)) {
                packet_host = NULL;
                /* 
                 * Note: In general, we don't expect a client to provide
                 *       enough information to match by option for these
                 *       types of messages, but if we don't have a UID
                 *       match we can check anyway.
                 */
                if (!find_hosts_by_option(&packet_host, 
                                          packet, packet->options, MDL)) {
                        packet_host = NULL;

                        if (!find_hosts_by_duid_chaddr(&packet_host,
                                                       client_id))
                                packet_host = NULL;
                }
        }

        /* 
         * Set our reply information.
         */
        reply->msg_type = DHCPV6_REPLY;
        memcpy(reply->transaction_id, packet->dhcpv6_transaction_id, 
               sizeof(reply->transaction_id));

        /*
         * Build our option state for reply.
         */
        opt_state = NULL;
        if (!option_state_allocate(&opt_state, MDL)) {
                log_error("iterate_over_ia_na: no memory for option_state.");
                goto exit;
        }
        execute_statements_in_scope(NULL, packet, NULL, NULL, 
                                    packet->options, opt_state, 
                                    &global_scope, root_group, NULL, NULL);

        /* 
         * RFC 3315, section 18.2.7 tells us which options to include.
         */
        oc = lookup_option(&dhcpv6_universe, opt_state, D6O_SERVERID);
        if (oc == NULL) {
                if (!save_option_buffer(&dhcpv6_universe, opt_state, NULL, 
                                        (unsigned char *)server_duid.data, 
                                        server_duid.len, D6O_SERVERID, 0)) {
                        log_error("iterate_over_ia_na: "
                                  "error saving server identifier.");
                        goto exit;
                }
        }

        if (!save_option_buffer(&dhcpv6_universe, opt_state, 
                                client_id->buffer, 
                                (unsigned char *)client_id->data,
                                client_id->len, 
                                D6O_CLIENTID, 0)) {
                log_error("iterate_over_ia_na: "
                          "error saving client identifier.");
                goto exit;
        }

        snprintf(status_msg, sizeof(status_msg), "%s received.", packet_type);
        if (!set_status_code(STATUS_Success, status_msg, opt_state)) {
                goto exit;
        }

        /* 
         * Add our options that are not associated with any IA_NA or IA_TA. 
         */
        reply_ofs += store_options6(reply_data+reply_ofs,
                                    sizeof(reply_data)-reply_ofs, 
                                    opt_state, packet,
                                    required_opts, NULL);

        /*
         * Loop through the IA_NA reported by the client, and deal with
         * addresses reported as already in use.
         */
        for (ia = lookup_option(&dhcpv6_universe, packet->options, D6O_IA_NA);
             ia != NULL; ia = ia->next) {

                if (!get_encapsulated_IA_state(&cli_enc_opt_state,
                                               &cli_enc_opt_data,
                                               packet, ia, IA_NA_OFFSET)) {
                        goto exit;
                }

                iaid = getULong(cli_enc_opt_data.data);

                /* 
                 * XXX: It is possible that we can get multiple addresses
                 *      sent by the client. We don't send multiple 
                 *      addresses, so this indicates a client error. 
                 *      We should check for multiple IAADDR options, log
                 *      if found, and set as an error.
                 */
                oc = lookup_option(&dhcpv6_universe, cli_enc_opt_state, 
                                   D6O_IAADDR);
                if (oc == NULL) {
                        /* no address given for this IA, ignore */
                        option_state_dereference(&cli_enc_opt_state, MDL);
                        data_string_forget(&cli_enc_opt_data, MDL);
                        continue;
                }

                memset(&iaaddr, 0, sizeof(iaaddr));
                if (!evaluate_option_cache(&iaaddr, packet, NULL, NULL, 
                                           packet->options, NULL,
                                           &global_scope, oc, MDL)) {
                        log_error("iterate_over_ia_na: "
                                  "error evaluating IAADDR.");
                        goto exit;
                }

                /* 
                 * Now we need to figure out which host record matches
                 * this IA_NA and IAADDR (encapsulated option contents
                 * matching a host record by option).
                 *
                 * XXX: We don't currently track IA_NA separately, but
                 *      we will need to do this!
                 */
                host = NULL;
                if (!find_hosts_by_option(&host, packet, 
                                          cli_enc_opt_state, MDL)) { 
                        if (packet_host != NULL) {
                                host = packet_host;
                        } else {
                                host = NULL;
                        }
                }
                while (host != NULL) {
                        if (host->fixed_addr != NULL) {
                                if (!evaluate_option_cache(&fixed_addr, NULL, 
                                                           NULL, NULL, NULL, 
                                                           NULL, &global_scope,
                                                           host->fixed_addr, 
                                                           MDL)) {
                                        log_error("iterate_over_ia_na: error "
                                                  "evaluating host address.");
                                        goto exit;
                                }
                                if ((iaaddr.len >= 16) &&
                                    !memcmp(fixed_addr.data, iaaddr.data, 16)) {
                                        data_string_forget(&fixed_addr, MDL);
                                        break;
                                }
                                data_string_forget(&fixed_addr, MDL);
                        }
                        host = host->n_ipaddr;
                }

                if ((host == NULL) && (iaaddr.len >= IAADDR_OFFSET)) {
                        /*
                         * Find existing IA_NA.
                         */
                        if (ia_make_key(&key, iaid, 
                                        (char *)client_id->data,
                                        client_id->len, 
                                        MDL) != ISC_R_SUCCESS) {
                                log_fatal("iterate_over_ia_na: no memory for "
                                          "key.");
                        }

                        existing_ia_na = NULL;
                        if (ia_hash_lookup(&existing_ia_na, ia_na_active, 
                                           (unsigned char *)key.data, 
                                           key.len, MDL)) {
                                /* 
                                 * Make sure this address is in the IA_NA.
                                 */
                                for (i=0; i<existing_ia_na->num_iasubopt; i++) {
                                        struct iasubopt *tmp;
                                        struct in6_addr *in6_addr;

                                        tmp = existing_ia_na->iasubopt[i];
                                        in6_addr = &tmp->addr;
                                        if (memcmp(in6_addr, 
                                                   iaaddr.data, 16) == 0) {
                                                iasubopt_reference(&lease,
                                                                   tmp, MDL);
                                                break;
                                        }
                                }
                        }

                        data_string_forget(&key, MDL);
                }

                if ((host != NULL) || (lease != NULL)) {
                        ia_na_match(client_id, &iaaddr, lease);
                } else {
                        ia_na_nomatch(client_id, &iaaddr, 
                                      (u_int32_t *)cli_enc_opt_data.data, 
                                      packet, reply_data, &reply_ofs, 
                                      sizeof(reply_data));
                }

                if (lease != NULL) {
                        iasubopt_dereference(&lease, MDL);
                }

                data_string_forget(&iaaddr, MDL);
                option_state_dereference(&cli_enc_opt_state, MDL);
                data_string_forget(&cli_enc_opt_data, MDL);
        }

        /* 
         * Return our reply to the caller.
         */
        reply_ret->len = reply_ofs;
        reply_ret->buffer = NULL;
        if (!buffer_allocate(&reply_ret->buffer, reply_ofs, MDL)) {
                log_fatal("No memory to store reply.");
        }
        reply_ret->data = reply_ret->buffer->data;
        memcpy(reply_ret->buffer->data, reply, reply_ofs);

exit:
        if (lease != NULL) {
                iasubopt_dereference(&lease, MDL);
        }
        if (host_opt_state != NULL) {
                option_state_dereference(&host_opt_state, MDL);
        }
        if (fixed_addr.buffer != NULL) {
                data_string_forget(&fixed_addr, MDL);
        }
        if (iaaddr.buffer != NULL) {
                data_string_forget(&iaaddr, MDL);
        }
        if (cli_enc_opt_state != NULL) {
                option_state_dereference(&cli_enc_opt_state, MDL);
        }
        if (cli_enc_opt_data.buffer != NULL) {
                data_string_forget(&cli_enc_opt_data, MDL);
        }
        if (opt_state != NULL) {
                option_state_dereference(&opt_state, MDL);
        }
}

/*
 * Decline means a client has detected that something else is using an
 * address we gave it.
 *
 * Since we're only dealing with fixed leases for now, there's not
 * much we can do, other that log the occurrence.
 * 
 * When we start issuing addresses from pools, then we will have to
 * record our declined addresses and issue another. In general with
 * IPv6 there is no worry about DoS by clients exhausting space, but
 * we still need to be aware of this possibility.
 */

/* TODO: reject unicast messages, unless we set unicast option */
/* TODO: IA_TA */
static void
dhcpv6_decline(struct data_string *reply, struct packet *packet) {
        struct data_string client_id;
        struct data_string server_id;

        /* 
         * Validate our input.
         */
        if (!valid_client_resp(packet, &client_id, &server_id)) {
                return;
        }

        /*
         * Undefined for IA_PD.
         */
        delete_option(&dhcpv6_universe, packet->options, D6O_IA_PD);

        /*
         * And operate on each IA_NA in this packet.
         */
        iterate_over_ia_na(reply, packet, &client_id, &server_id, "Decline", 
                           ia_na_match_decline, ia_na_nomatch_decline);

        data_string_forget(&server_id, MDL);
        data_string_forget(&client_id, MDL);
}

static void
ia_na_match_release(const struct data_string *client_id,
                    const struct data_string *iaaddr,
                    struct iasubopt *lease)
{
        char tmp_addr[INET6_ADDRSTRLEN];

        log_info("Client %s releases address %s",
                 print_hex_1(client_id->len, client_id->data, 60),
                 inet_ntop(AF_INET6, iaaddr->data, tmp_addr, sizeof(tmp_addr)));
        if (lease != NULL) {
                release_lease6(lease->ipv6_pool, lease);
                lease->ia->cltt = cur_time;
                write_ia(lease->ia);
        }
}

static void
ia_na_nomatch_release(const struct data_string *client_id,
                      const struct data_string *iaaddr,
                      u_int32_t *ia_na_id,
                      struct packet *packet,
                      char *reply_data,
                      int *reply_ofs,
                      int reply_len)
{
        char tmp_addr[INET6_ADDRSTRLEN];
        struct option_state *host_opt_state;
        int len;

        log_info("Client %s releases address %s, which is not leased to it.",
                 print_hex_1(client_id->len, client_id->data, 60),
                 inet_ntop(AF_INET6, iaaddr->data, tmp_addr, sizeof(tmp_addr)));

        /*
         * Create state for this IA_NA.
         */
        host_opt_state = NULL;
        if (!option_state_allocate(&host_opt_state, MDL)) {
                log_error("ia_na_nomatch_release: out of memory "
                          "allocating option_state.");
                goto exit;
        }

        if (!set_status_code(STATUS_NoBinding, 
                             "Release for non-leased address.",
                             host_opt_state)) {
                goto exit;
        }

        /*
         * Insure we have enough space
         */
        if (reply_len < (*reply_ofs + 16)) {
                log_error("ia_na_nomatch_release: "
                          "out of space for reply packet.");
                goto exit;
        }

        /*
         * Put our status code into the reply packet.
         */
        len = store_options6(reply_data+(*reply_ofs)+16,
                             reply_len-(*reply_ofs)-16,
                             host_opt_state, packet,
                             required_opts_STATUS_CODE, NULL);

        /*
         * Store the non-encapsulated option data for this 
         * IA_NA into our reply packet. Defined in RFC 3315, 
         * section 22.4.  
         */
        /* option number */
        putUShort((unsigned char *)reply_data+(*reply_ofs), D6O_IA_NA);
        /* option length */
        putUShort((unsigned char *)reply_data+(*reply_ofs)+2, len + 12);
        /* IA_NA, copied from the client */
        memcpy(reply_data+(*reply_ofs)+4, ia_na_id, 4);
        /* t1 and t2, odd that we need them, but here it is */
        putULong((unsigned char *)reply_data+(*reply_ofs)+8, 0);
        putULong((unsigned char *)reply_data+(*reply_ofs)+12, 0);

        /*
         * Get ready for next IA_NA.
         */
        *reply_ofs += (len + 16);

exit:
        option_state_dereference(&host_opt_state, MDL);
}

static void
ia_pd_match_release(const struct data_string *client_id,
                    const struct data_string *iapref,
                    struct iasubopt *prefix)
{
        char tmp_addr[INET6_ADDRSTRLEN];

        log_info("Client %s releases prefix %s/%u",
                 print_hex_1(client_id->len, client_id->data, 60),
                 inet_ntop(AF_INET6, iapref->data + 9,
                           tmp_addr, sizeof(tmp_addr)),
                 (unsigned) getUChar(iapref->data + 8));
        if (prefix != NULL) {
                release_lease6(prefix->ipv6_pool, prefix);
                prefix->ia->cltt = cur_time;
                write_ia(prefix->ia);
        }
}

static void
ia_pd_nomatch_release(const struct data_string *client_id,
                      const struct data_string *iapref,
                      u_int32_t *ia_pd_id,
                      struct packet *packet,
                      char *reply_data,
                      int *reply_ofs,
                      int reply_len)
{
        char tmp_addr[INET6_ADDRSTRLEN];
        struct option_state *host_opt_state;
        int len;

        log_info("Client %s releases prefix %s/%u, which is not leased to it.",
                 print_hex_1(client_id->len, client_id->data, 60),
                 inet_ntop(AF_INET6, iapref->data + 9,
                           tmp_addr, sizeof(tmp_addr)),
                 (unsigned) getUChar(iapref->data + 8));

        /*
         * Create state for this IA_PD.
         */
        host_opt_state = NULL;
        if (!option_state_allocate(&host_opt_state, MDL)) {
                log_error("ia_pd_nomatch_release: out of memory "
                          "allocating option_state.");
                goto exit;
        }

        if (!set_status_code(STATUS_NoBinding, 
                             "Release for non-leased prefix.",
                             host_opt_state)) {
                goto exit;
        }

        /*
         * Insure we have enough space
         */
        if (reply_len < (*reply_ofs + 16)) {
                log_error("ia_pd_nomatch_release: "
                          "out of space for reply packet.");
                goto exit;
        }

        /*
         * Put our status code into the reply packet.
         */
        len = store_options6(reply_data+(*reply_ofs)+16,
                             reply_len-(*reply_ofs)-16,
                             host_opt_state, packet,
                             required_opts_STATUS_CODE, NULL);

        /*
         * Store the non-encapsulated option data for this 
         * IA_PD into our reply packet. Defined in RFC 3315, 
         * section 22.4.  
         */
        /* option number */
        putUShort((unsigned char *)reply_data+(*reply_ofs), D6O_IA_PD);
        /* option length */
        putUShort((unsigned char *)reply_data+(*reply_ofs)+2, len + 12);
        /* IA_PD, copied from the client */
        memcpy(reply_data+(*reply_ofs)+4, ia_pd_id, 4);
        /* t1 and t2, odd that we need them, but here it is */
        putULong((unsigned char *)reply_data+(*reply_ofs)+8, 0);
        putULong((unsigned char *)reply_data+(*reply_ofs)+12, 0);

        /*
         * Get ready for next IA_PD.
         */
        *reply_ofs += (len + 16);

exit:
        option_state_dereference(&host_opt_state, MDL);
}

static void
iterate_over_ia_pd(struct data_string *reply_ret, 
                   struct packet *packet,
                   const struct data_string *client_id,
                   const struct data_string *server_id,
                   const char *packet_type,
                   void (*ia_pd_match)(),
                   void (*ia_pd_nomatch)())
{
        struct data_string reply_new;
        int reply_len;
        struct option_state *opt_state;
        struct host_decl *packet_host;
        struct option_cache *ia;
        struct option_cache *oc;
        /* cli_enc_... variables come from the IA_PD options */
        struct data_string cli_enc_opt_data;
        struct option_state *cli_enc_opt_state;
        struct host_decl *host;
        struct option_state *host_opt_state;
        struct data_string iaprefix;
        char reply_data[65536];
        int reply_ofs;
        struct iasubopt *prefix;
        struct ia_xx *existing_ia_pd;
        int i;
        struct data_string key;
        u_int32_t iaid;

        /*
         * Initialize to empty values, in case we have to exit early.
         */
        memset(&reply_new, 0, sizeof(reply_new));
        opt_state = NULL;
        memset(&cli_enc_opt_data, 0, sizeof(cli_enc_opt_data));
        cli_enc_opt_state = NULL;
        memset(&iaprefix, 0, sizeof(iaprefix));
        host_opt_state = NULL;
        prefix = NULL;

        /*
         * Compute the available length for the reply.
         */
        reply_len = sizeof(reply_data) - reply_ret->len;
        reply_ofs = 0;

        /* 
         * Find the host record that matches from the packet, if any.
         */
        packet_host = NULL;
        if (!find_hosts_by_uid(&packet_host, 
                               client_id->data, client_id->len, MDL)) {
                packet_host = NULL;
                /* 
                 * Note: In general, we don't expect a client to provide
                 *       enough information to match by option for these
                 *       types of messages, but if we don't have a UID
                 *       match we can check anyway.
                 */
                if (!find_hosts_by_option(&packet_host, 
                                          packet, packet->options, MDL)) {
                        packet_host = NULL;

                        if (!find_hosts_by_duid_chaddr(&packet_host,
                                                       client_id))
                                packet_host = NULL;
                }
        }

        /*
         * Build our option state for reply.
         */
        opt_state = NULL;
        if (!option_state_allocate(&opt_state, MDL)) {
                log_error("iterate_over_ia_pd: no memory for option_state.");
                goto exit;
        }
        execute_statements_in_scope(NULL, packet, NULL, NULL, 
                                    packet->options, opt_state, 
                                    &global_scope, root_group, NULL, NULL);

        /*
         * Loop through the IA_PD reported by the client, and deal with
         * prefixes reported as already in use.
         */
        for (ia = lookup_option(&dhcpv6_universe, packet->options, D6O_IA_PD);
             ia != NULL; ia = ia->next) {

            if (!get_encapsulated_IA_state(&cli_enc_opt_state,
                                           &cli_enc_opt_data,
                                           packet, ia, IA_PD_OFFSET)) {
                goto exit;
            }

            iaid = getULong(cli_enc_opt_data.data);

            oc = lookup_option(&dhcpv6_universe, cli_enc_opt_state, 
                               D6O_IAPREFIX);
            if (oc == NULL) {
                /* no prefix given for this IA_PD, ignore */
                option_state_dereference(&cli_enc_opt_state, MDL);
                data_string_forget(&cli_enc_opt_data, MDL);
                continue;
            }

            for (; oc != NULL; oc = oc->next) {
                memset(&iaprefix, 0, sizeof(iaprefix));
                if (!evaluate_option_cache(&iaprefix, packet, NULL, NULL, 
                                           packet->options, NULL,
                                           &global_scope, oc, MDL)) {
                        log_error("iterate_over_ia_pd: "
                                  "error evaluating IAPREFIX.");
                        goto exit;
                }

                /* 
                 * Now we need to figure out which host record matches
                 * this IA_PD and IAPREFIX (encapsulated option contents
                 * matching a host record by option).
                 *
                 * XXX: We don't currently track IA_PD separately, but
                 *      we will need to do this!
                 */
                host = NULL;
                if (!find_hosts_by_option(&host, packet, 
                                          cli_enc_opt_state, MDL)) { 
                        if (packet_host != NULL) {
                                host = packet_host;
                        } else {
                                host = NULL;
                        }
                }
                while (host != NULL) {
                        if (host->fixed_prefix != NULL) {
                                struct iaddrcidrnetlist *l;
                                int plen = (int) getUChar(iaprefix.data + 8);

                                for (l = host->fixed_prefix; l != NULL;
                                     l = l->next) {
                                        if (plen != l->cidrnet.bits)
                                                continue;
                                        if (memcmp(iaprefix.data + 9,
                                                   l->cidrnet.lo_addr.iabuf,
                                                   16) == 0)
                                                break;
                                }
                                if ((l != NULL) && (iaprefix.len >= 17))
                                        break;
                        }
                        host = host->n_ipaddr;
                }

                if ((host == NULL) && (iaprefix.len >= IAPREFIX_OFFSET)) {
                        /*
                         * Find existing IA_PD.
                         */
                        if (ia_make_key(&key, iaid, 
                                        (char *)client_id->data,
                                        client_id->len, 
                                        MDL) != ISC_R_SUCCESS) {
                                log_fatal("iterate_over_ia_pd: no memory for "
                                          "key.");
                        }

                        existing_ia_pd = NULL;
                        if (ia_hash_lookup(&existing_ia_pd, ia_pd_active, 
                                           (unsigned char *)key.data, 
                                           key.len, MDL)) {
                                /* 
                                 * Make sure this prefix is in the IA_PD.
                                 */
                                for (i = 0;
                                     i < existing_ia_pd->num_iasubopt;
                                     i++) {
                                        struct iasubopt *tmp;
                                        u_int8_t plen;

                                        plen = getUChar(iaprefix.data + 8);
                                        tmp = existing_ia_pd->iasubopt[i];
                                        if ((tmp->plen == plen) &&
                                            (memcmp(&tmp->addr,
                                                    iaprefix.data + 9,
                                                    16) == 0)) {
                                                iasubopt_reference(&prefix,
                                                                   tmp, MDL);
                                                break;
                                        }
                                }
                        }

                        data_string_forget(&key, MDL);
                }

                if ((host != NULL) || (prefix != NULL)) {
                        ia_pd_match(client_id, &iaprefix, prefix);
                } else {
                        ia_pd_nomatch(client_id, &iaprefix, 
                                      (u_int32_t *)cli_enc_opt_data.data, 
                                      packet, reply_data, &reply_ofs, 
                                      reply_len - reply_ofs);
                }

                if (prefix != NULL) {
                        iasubopt_dereference(&prefix, MDL);
                }

                data_string_forget(&iaprefix, MDL);
            }

            option_state_dereference(&cli_enc_opt_state, MDL);
            data_string_forget(&cli_enc_opt_data, MDL);
        }

        /* 
         * Return our reply to the caller.
         * The IA_NA routine has already filled at least the header.
         */
        reply_new.len = reply_ret->len + reply_ofs;
        if (!buffer_allocate(&reply_new.buffer, reply_new.len, MDL)) {
                log_fatal("No memory to store reply.");
        }
        reply_new.data = reply_new.buffer->data;
        memcpy(reply_new.buffer->data,
               reply_ret->buffer->data, reply_ret->len);
        memcpy(reply_new.buffer->data + reply_ret->len,
               reply_data, reply_ofs);
        data_string_forget(reply_ret, MDL);
        data_string_copy(reply_ret, &reply_new, MDL);
        data_string_forget(&reply_new, MDL);

exit:
        if (prefix != NULL) {
                iasubopt_dereference(&prefix, MDL);
        }
        if (host_opt_state != NULL) {
                option_state_dereference(&host_opt_state, MDL);
        }
        if (iaprefix.buffer != NULL) {
                data_string_forget(&iaprefix, MDL);
        }
        if (cli_enc_opt_state != NULL) {
                option_state_dereference(&cli_enc_opt_state, MDL);
        }
        if (cli_enc_opt_data.buffer != NULL) {
                data_string_forget(&cli_enc_opt_data, MDL);
        }
        if (opt_state != NULL) {
                option_state_dereference(&opt_state, MDL);
        }
}

/*
 * Release means a client is done with the leases.
 */

/* TODO: reject unicast messages, unless we set unicast option */
static void
dhcpv6_release(struct data_string *reply, struct packet *packet) {
        struct data_string client_id;
        struct data_string server_id;

        /* 
         * Validate our input.
         */
        if (!valid_client_resp(packet, &client_id, &server_id)) {
                return;
        }

        /*
         * And operate on each IA_NA in this packet.
         */
        iterate_over_ia_na(reply, packet, &client_id, &server_id, "Release", 
                           ia_na_match_release, ia_na_nomatch_release);

        /*
         * And operate on each IA_PD in this packet.
         */
        iterate_over_ia_pd(reply, packet, &client_id, &server_id, "Release",
                           ia_pd_match_release, ia_pd_nomatch_release);

        data_string_forget(&server_id, MDL);
        data_string_forget(&client_id, MDL);
}

/*
 * Information-Request is used by clients who have obtained an address
 * from other means, but want configuration information from the server.
 */

static void
dhcpv6_information_request(struct data_string *reply, struct packet *packet) {
        struct data_string client_id;
        struct data_string server_id;

        /*
         * Validate our input.
         */
        if (!valid_client_info_req(packet, &server_id)) {
                return;
        }

        /*
         * Get our client ID, if there is one.
         */
        memset(&client_id, 0, sizeof(client_id));
        if (get_client_id(packet, &client_id) != ISC_R_SUCCESS) {
                data_string_forget(&client_id, MDL);
        }

        /*
         * Use the lease_to_client() function. This will work fine, 
         * because the valid_client_info_req() insures that we 
         * don't have any IA that would cause us to allocate
         * resources to the client.
         */
        lease_to_client(reply, packet, &client_id,
                        server_id.data != NULL ? &server_id : NULL);

        /*
         * Cleanup.
         */
        if (client_id.data != NULL) {
                data_string_forget(&client_id, MDL);
        }
        data_string_forget(&server_id, MDL);
}

/* 
 * The Relay-forw message is sent by relays. It typically contains a
 * single option, which encapsulates an entire packet.
 *
 * We need to build an encapsulated reply.
 */

/* XXX: this is very, very similar to do_packet6(), and should probably
        be combined in a clever way */
static void
dhcpv6_relay_forw(struct data_string *reply_ret, struct packet *packet) {
        struct option_cache *oc;
        struct data_string enc_opt_data;
        struct packet *enc_packet;
        unsigned char msg_type;
        const struct dhcpv6_packet *msg;
        const struct dhcpv6_relay_packet *relay;
        struct data_string enc_reply;
        char link_addr[sizeof("ffff:ffff:ffff:ffff:ffff:ffff:255.255.255.255")];
        char peer_addr[sizeof("ffff:ffff:ffff:ffff:ffff:ffff:255.255.255.255")];
        struct data_string a_opt, packet_ero;
        struct option_state *opt_state;
        static char reply_data[65536];
        struct dhcpv6_relay_packet *reply;
        int reply_ofs;

        /* 
         * Initialize variables for early exit.
         */
        opt_state = NULL;
        memset(&a_opt, 0, sizeof(a_opt));
        memset(&packet_ero, 0, sizeof(packet_ero));
        memset(&enc_reply, 0, sizeof(enc_reply));
        memset(&enc_opt_data, 0, sizeof(enc_opt_data));
        enc_packet = NULL;

        /*
         * Get our encapsulated relay message.
         */
        oc = lookup_option(&dhcpv6_universe, packet->options, D6O_RELAY_MSG);
        if (oc == NULL) {
                inet_ntop(AF_INET6, &packet->dhcpv6_link_address,
                          link_addr, sizeof(link_addr));
                inet_ntop(AF_INET6, &packet->dhcpv6_peer_address,
                          peer_addr, sizeof(peer_addr));
                log_info("Relay-forward from %s with link address=%s and "
                         "peer address=%s missing Relay Message option.",
                          piaddr(packet->client_addr), link_addr, peer_addr);
                goto exit;
        }

        if (!evaluate_option_cache(&enc_opt_data, NULL, NULL, NULL, 
                                   NULL, NULL, &global_scope, oc, MDL)) {
                log_error("dhcpv6_forw_relay: error evaluating "
                          "relayed message.");
                goto exit;
        }

        if (!packet6_len_okay((char *)enc_opt_data.data, enc_opt_data.len)) {
                log_error("dhcpv6_forw_relay: encapsulated packet too short.");
                goto exit;
        }

        /*
         * Build a packet structure from this encapsulated packet.
         */
        enc_packet = NULL;
        if (!packet_allocate(&enc_packet, MDL)) {
                log_error("dhcpv6_forw_relay: "
                          "no memory for encapsulated packet.");
                goto exit;
        }

        if (!option_state_allocate(&enc_packet->options, MDL)) {
                log_error("dhcpv6_forw_relay: "
                          "no memory for encapsulated packet's options.");
                goto exit;
        }

        enc_packet->client_port = packet->client_port;
        enc_packet->client_addr = packet->client_addr;
        interface_reference(&enc_packet->interface, packet->interface, MDL);
        enc_packet->dhcpv6_container_packet = packet;

        msg_type = enc_opt_data.data[0];
        if ((msg_type == DHCPV6_RELAY_FORW) ||
            (msg_type == DHCPV6_RELAY_REPL)) {
                int relaylen = (int)(offsetof(struct dhcpv6_relay_packet, options));
                relay = (struct dhcpv6_relay_packet *)enc_opt_data.data;
                enc_packet->dhcpv6_msg_type = relay->msg_type;

                /* relay-specific data */
                enc_packet->dhcpv6_hop_count = relay->hop_count;
                memcpy(&enc_packet->dhcpv6_link_address,
                       relay->link_address, sizeof(relay->link_address));
                memcpy(&enc_packet->dhcpv6_peer_address,
                       relay->peer_address, sizeof(relay->peer_address));

                if (!parse_option_buffer(enc_packet->options,
                                         relay->options, 
                                         enc_opt_data.len - relaylen,
                                         &dhcpv6_universe)) {
                        /* no logging here, as parse_option_buffer() logs all
                           cases where it fails */
                        goto exit;
                }
        } else {
                int msglen = (int)(offsetof(struct dhcpv6_packet, options));
                msg = (struct dhcpv6_packet *)enc_opt_data.data;
                enc_packet->dhcpv6_msg_type = msg->msg_type;

                /* message-specific data */
                memcpy(enc_packet->dhcpv6_transaction_id,
                       msg->transaction_id,
                       sizeof(enc_packet->dhcpv6_transaction_id));

                if (!parse_option_buffer(enc_packet->options,
                                         msg->options, 
                                         enc_opt_data.len - msglen,
                                         &dhcpv6_universe)) {
                        /* no logging here, as parse_option_buffer() logs all
                           cases where it fails */
                        goto exit;
                }
        }

        /*
         * This is recursive. It is possible to exceed maximum packet size.
         * XXX: This will cause the packet send to fail.
         */
        build_dhcpv6_reply(&enc_reply, enc_packet);

        /*
         * If we got no encapsulated data, then it is discarded, and
         * our reply-forw is also discarded.
         */
        if (enc_reply.data == NULL) {
                goto exit;
        }

        /*
         * Now we can use the reply_data buffer.
         * Packet header stuff all comes from the forward message.
         */
        reply = (struct dhcpv6_relay_packet *)reply_data;
        reply->msg_type = DHCPV6_RELAY_REPL;
        reply->hop_count = packet->dhcpv6_hop_count;
        memcpy(reply->link_address, &packet->dhcpv6_link_address,
               sizeof(reply->link_address));
        memcpy(reply->peer_address, &packet->dhcpv6_peer_address,
               sizeof(reply->peer_address));
        reply_ofs = (int)(offsetof(struct dhcpv6_relay_packet, options));

        /*
         * Get the reply option state.
         */
        opt_state = NULL;
        if (!option_state_allocate(&opt_state, MDL)) {
                log_error("dhcpv6_relay_forw: no memory for option state.");
                goto exit;
        }

        /*
         * Append the interface-id if present.
         */
        oc = lookup_option(&dhcpv6_universe, packet->options,
                           D6O_INTERFACE_ID);
        if (oc != NULL) {
                if (!evaluate_option_cache(&a_opt, packet,
                                           NULL, NULL, 
                                           packet->options, NULL,
                                           &global_scope, oc, MDL)) {
                        log_error("dhcpv6_relay_forw: error evaluating "
                                  "Interface ID.");
                        goto exit;
                }
                if (!save_option_buffer(&dhcpv6_universe, opt_state, NULL,
                                        (unsigned char *)a_opt.data,
                                        a_opt.len,
                                        D6O_INTERFACE_ID, 0)) {
                        log_error("dhcpv6_relay_forw: error saving "
                                  "Interface ID.");
                        goto exit;
                }
                data_string_forget(&a_opt, MDL);
        }

        /* 
         * Append our encapsulated stuff for caller.
         */
        if (!save_option_buffer(&dhcpv6_universe, opt_state, NULL,
                                (unsigned char *)enc_reply.data,
                                enc_reply.len,
                                D6O_RELAY_MSG, 0)) {
                log_error("dhcpv6_relay_forw: error saving Relay MSG.");
                goto exit;
        }

        /*
         * Get the ERO if any.
         */
        oc = lookup_option(&dhcpv6_universe, packet->options, D6O_ERO);
        if (oc != NULL) {
                unsigned req;
                int i;

                if (!evaluate_option_cache(&packet_ero, packet,
                                           NULL, NULL,
                                           packet->options, NULL,
                                           &global_scope, oc, MDL) ||
                        (packet_ero.len & 1)) {
                        log_error("dhcpv6_relay_forw: error evaluating ERO.");
                        goto exit;
                }

                /* Decode and apply the ERO. */
                for (i = 0; i < packet_ero.len; i += 2) {
                        req = getUShort(packet_ero.data + i);
                        /* Already in the reply? */
                        oc = lookup_option(&dhcpv6_universe, opt_state, req);
                        if (oc != NULL)
                                continue;
                        /* Get it from the packet if present. */
                        oc = lookup_option(&dhcpv6_universe,
                                           packet->options,
                                           req);
                        if (oc == NULL)
                                continue;
                        if (!evaluate_option_cache(&a_opt, packet,
                                                   NULL, NULL,
                                                   packet->options, NULL,
                                                   &global_scope, oc, MDL)) {
                                log_error("dhcpv6_relay_forw: error "
                                          "evaluating option %u.", req);
                                goto exit;
                        }
                        if (!save_option_buffer(&dhcpv6_universe,
                                                opt_state,
                                                NULL,
                                                (unsigned char *)a_opt.data,
                                                a_opt.len,
                                                req,
                                                0)) {
                                log_error("dhcpv6_relay_forw: error saving "
                                          "option %u.", req);
                                goto exit;
                        }
                        data_string_forget(&a_opt, MDL);
                }
        }

        reply_ofs += store_options6(reply_data + reply_ofs,
                                    sizeof(reply_data) - reply_ofs,
                                    opt_state, packet,
                                    required_opts_agent, &packet_ero);

        /*
         * Return our reply to the caller.
         */
        reply_ret->len = reply_ofs;
        reply_ret->buffer = NULL;
        if (!buffer_allocate(&reply_ret->buffer, reply_ret->len, MDL)) {
                log_fatal("No memory to store reply.");
        }
        reply_ret->data = reply_ret->buffer->data;
        memcpy(reply_ret->buffer->data, reply_data, reply_ofs);

exit:
        if (opt_state != NULL)
                option_state_dereference(&opt_state, MDL);
        if (a_opt.data != NULL) {
                data_string_forget(&a_opt, MDL);
        }
        if (packet_ero.data != NULL) {
                data_string_forget(&packet_ero, MDL);
        }
        if (enc_reply.data != NULL) {
                data_string_forget(&enc_reply, MDL);
        }
        if (enc_opt_data.data != NULL) {
                data_string_forget(&enc_opt_data, MDL);
        }
        if (enc_packet != NULL) {
                packet_dereference(&enc_packet, MDL);
        }
}

static void
dhcpv6_discard(struct packet *packet) {
        /* INSIST(packet->msg_type > 0); */
        /* INSIST(packet->msg_type < dhcpv6_type_name_max); */

        log_debug("Discarding %s from %s; message type not handled by server", 
                  dhcpv6_type_names[packet->dhcpv6_msg_type],
                  piaddr(packet->client_addr));
}

static void 
build_dhcpv6_reply(struct data_string *reply, struct packet *packet) {
        memset(reply, 0, sizeof(*reply));
        switch (packet->dhcpv6_msg_type) {
                case DHCPV6_SOLICIT:
                        dhcpv6_solicit(reply, packet);
                        break;
                case DHCPV6_ADVERTISE:
                        dhcpv6_discard(packet);
                        break;
                case DHCPV6_REQUEST:
                        dhcpv6_request(reply, packet);
                        break;
                case DHCPV6_CONFIRM:
                        dhcpv6_confirm(reply, packet);
                        break;
                case DHCPV6_RENEW:
                        dhcpv6_renew(reply, packet);
                        break;
                case DHCPV6_REBIND:
                        dhcpv6_rebind(reply, packet);
                        break;
                case DHCPV6_REPLY:
                        dhcpv6_discard(packet);
                        break;
                case DHCPV6_RELEASE:
                        dhcpv6_release(reply, packet);
                        break;
                case DHCPV6_DECLINE:
                        dhcpv6_decline(reply, packet);
                        break;
                case DHCPV6_RECONFIGURE:
                        dhcpv6_discard(packet);
                        break;
                case DHCPV6_INFORMATION_REQUEST:
                        dhcpv6_information_request(reply, packet);
                        break;
                case DHCPV6_RELAY_FORW:
                        dhcpv6_relay_forw(reply, packet);
                        break;
                case DHCPV6_RELAY_REPL:
                        dhcpv6_discard(packet);
                        break;
                case DHCPV6_LEASEQUERY:
                        dhcpv6_leasequery(reply, packet);
                        break;
                case DHCPV6_LEASEQUERY_REPLY:
                        dhcpv6_discard(packet);
                        break;
                default:
                        /* XXX: would be nice if we had "notice" level, 
                                as syslog, for this */
                        log_info("Discarding unknown DHCPv6 message type %d "
                                 "from %s", packet->dhcpv6_msg_type, 
                                 piaddr(packet->client_addr));
        }
}

static void
log_packet_in(const struct packet *packet) {
        struct data_string s;
        u_int32_t tid;
        char tmp_addr[INET6_ADDRSTRLEN];
        const void *addr;

        memset(&s, 0, sizeof(s));

        if (packet->dhcpv6_msg_type < dhcpv6_type_name_max) {
                data_string_sprintfa(&s, "%s message from %s port %d",
                                     dhcpv6_type_names[packet->dhcpv6_msg_type],
                                     piaddr(packet->client_addr),
                                     ntohs(packet->client_port));
        } else {
                data_string_sprintfa(&s, 
                                     "Unknown message type %d from %s port %d",
                                     packet->dhcpv6_msg_type,
                                     piaddr(packet->client_addr),
                                     ntohs(packet->client_port));
        }
        if ((packet->dhcpv6_msg_type == DHCPV6_RELAY_FORW) || 
            (packet->dhcpv6_msg_type == DHCPV6_RELAY_REPL)) {
                addr = &packet->dhcpv6_link_address;
                data_string_sprintfa(&s, ", link address %s", 
                                     inet_ntop(AF_INET6, addr, 
                                               tmp_addr, sizeof(tmp_addr)));
                addr = &packet->dhcpv6_peer_address;
                data_string_sprintfa(&s, ", peer address %s", 
                                     inet_ntop(AF_INET6, addr, 
                                               tmp_addr, sizeof(tmp_addr)));
        } else {
                tid = 0;
                memcpy(((char *)&tid)+1, packet->dhcpv6_transaction_id, 3);
                data_string_sprintfa(&s, ", transaction ID 0x%06X", tid);

/*
                oc = lookup_option(&dhcpv6_universe, packet->options, 
                                   D6O_CLIENTID);
                if (oc != NULL) {
                        memset(&tmp_ds, 0, sizeof(tmp_ds_));
                        if (!evaluate_option_cache(&tmp_ds, packet, NULL, NULL, 
                                                   packet->options, NULL,
                                                   &global_scope, oc, MDL)) {
                                log_error("Error evaluating Client Identifier");
                        } else {
                                data_strint_sprintf(&s, ", client ID %s",

                                data_string_forget(&tmp_ds, MDL);
                        }
                }
*/

        }
        log_info("%s", s.data);

        data_string_forget(&s, MDL);
}

void 
dhcpv6(struct packet *packet) {
        struct data_string reply;
        struct sockaddr_in6 to_addr;
        int send_ret;

        /* 
         * Log a message that we received this packet.
         */
        log_packet_in(packet); 

        /*
         * Build our reply packet.
         */
        build_dhcpv6_reply(&reply, packet);

        if (reply.data != NULL) {
                /* 
                 * Send our reply, if we have one.
                 */
                memset(&to_addr, 0, sizeof(to_addr));
                to_addr.sin6_family = AF_INET6;
                if ((packet->dhcpv6_msg_type == DHCPV6_RELAY_FORW) || 
                    (packet->dhcpv6_msg_type == DHCPV6_RELAY_REPL)) {
                        to_addr.sin6_port = local_port;
                } else {
                        to_addr.sin6_port = remote_port;
                }

#if defined (REPLY_TO_SOURCE_PORT)
                /*
                 * This appears to have been included for testing so we would
                 * not need a root client, but was accidently left in the
                 * final code.  We continue to include it in case
                 * some users have come to rely upon it, but leave
                 * it off by default as it's a bad idea.
                 */
                to_addr.sin6_port = packet->client_port;
#endif

                memcpy(&to_addr.sin6_addr, packet->client_addr.iabuf, 
                       sizeof(to_addr.sin6_addr));

                log_info("Sending %s to %s port %d", 
                         dhcpv6_type_names[reply.data[0]],
                         piaddr(packet->client_addr),
                         ntohs(to_addr.sin6_port));

                send_ret = send_packet6(packet->interface, 
                                        reply.data, reply.len, &to_addr);
                if (send_ret != reply.len) {
                        log_error("dhcpv6: send_packet6() sent %d of %d bytes",
                                  send_ret, reply.len);
                }
                data_string_forget(&reply, MDL);
        }
}

static void
seek_shared_host(struct host_decl **hp, struct shared_network *shared) {
        struct host_decl *nofixed = NULL;
        struct host_decl *seek, *hold = NULL;

        /*
         * Seek forward through fixed addresses for the right link.
         *
         * Note: how to do this for fixed prefixes???
         */
        host_reference(&hold, *hp, MDL);
        host_dereference(hp, MDL);
        seek = hold;
        while (seek != NULL) {
                if (seek->fixed_addr == NULL)
                        nofixed = seek;
                else if (fixed_matches_shared(seek, shared))
                        break;

                seek = seek->n_ipaddr;
        }

        if ((seek == NULL) && (nofixed != NULL))
                seek = nofixed;

        if (seek != NULL)
                host_reference(hp, seek, MDL);
}

static isc_boolean_t
fixed_matches_shared(struct host_decl *host, struct shared_network *shared) {
        struct subnet *subnet;
        struct data_string addr;
        isc_boolean_t matched;
        struct iaddr fixed;

        if (host->fixed_addr == NULL)
                return ISC_FALSE;

        memset(&addr, 0, sizeof(addr));
        if (!evaluate_option_cache(&addr, NULL, NULL, NULL, NULL, NULL,
                                   &global_scope, host->fixed_addr, MDL))
                return ISC_FALSE;

        if (addr.len < 16) {
                data_string_forget(&addr, MDL);
                return ISC_FALSE;
        }

        fixed.len = 16;
        memcpy(fixed.iabuf, addr.data, 16);

        matched = ISC_FALSE;
        for (subnet = shared->subnets ; subnet != NULL ;
             subnet = subnet->next_sibling) {
                if (addr_eq(subnet_number(fixed, subnet->netmask),
                            subnet->net)) {
                        matched = ISC_TRUE;
                        break;
                }
        }

        data_string_forget(&addr, MDL);
        return matched;
}

/*
 * find_host_by_duid_chaddr() synthesizes a DHCPv4-like 'hardware'
 * parameter from a DHCPv6 supplied DUID (client-identifier option),
 * and may seek to use client or relay supplied hardware addresses.
 */
static int
find_hosts_by_duid_chaddr(struct host_decl **host,
                          const struct data_string *client_id) {
        static int once_htype;
        int htype, hlen;
        const unsigned char *chaddr;

        /*
         * The DUID-LL and DUID-LLT must have a 2-byte DUID type and 2-byte
         * htype.
         */
        if (client_id->len < 4)
                return 0;

        /*
         * The third and fourth octets of the DUID-LL and DUID-LLT
         * is the hardware type, but in 16 bits.
         */
        htype = getUShort(client_id->data + 2);
        hlen = 0;
        chaddr = NULL;

        /* The first two octets of the DUID identify the type. */
        switch(getUShort(client_id->data)) {
              case DUID_LLT:
                if (client_id->len > 8) {
                        hlen = client_id->len - 8;
                        chaddr = client_id->data + 8;
                }
                break;

              case DUID_LL:
                /*
                 * Note that client_id->len must be greater than or equal
                 * to four to get to this point in the function.
                 */
                hlen = client_id->len - 4;
                chaddr = client_id->data + 4;
                break;

              default:
                break;
        }

        if ((hlen == 0) || (hlen > HARDWARE_ADDR_LEN)) 
                return 0;

        /*
         * XXX: DHCPv6 gives a 16-bit field for the htype.  DHCPv4 gives an
         * 8-bit field.  To change the semantics of the generic 'hardware'
         * structure, we would have to adjust many DHCPv4 sources (from
         * interface to DHCPv4 lease code), and we would have to update the
         * 'hardware' config directive (probably being reverse compatible and
         * providing a new upgrade/replacement primitive).  This is a little
         * too much to change for now.  Hopefully we will revisit this before
         * hardware types exceeding 8 bits are assigned.
         */
        if ((htype & 0xFF00) && !once_htype) {
                once_htype = 1;
                log_error("Attention: At least one client advertises a "
                          "hardware type of %d, which exceeds the software "
                          "limitation of 255.", htype);
        }

        return find_hosts_by_haddr(host, htype, chaddr, hlen, MDL);
}

#endif /* DHCPv6 */