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[thirdparty/squid.git] / src / htcp.cc

/*
 * $Id: htcp.cc,v 1.81 2008/02/26 21:49:34 amosjeffries Exp $
 *
 * DEBUG: section 31    Hypertext Caching Protocol
 * AUTHOR: Duane Wesssels
 *
 * SQUID Web Proxy Cache          http://www.squid-cache.org/
 * ----------------------------------------------------------
 *
 *  Squid is the result of efforts by numerous individuals from
 *  the Internet community; see the CONTRIBUTORS file for full
 *  details.   Many organizations have provided support for Squid's
 *  development; see the SPONSORS file for full details.  Squid is
 *  Copyrighted (C) 2001 by the Regents of the University of
 *  California; see the COPYRIGHT file for full details.  Squid
 *  incorporates software developed and/or copyrighted by other
 *  sources; see the CREDITS file for full details.
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *  
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *  
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111, USA.
 *
 */

#include "squid.h"
#include "htcp.h"
#include "ACLChecklist.h"
#include "ACL.h"
#include "SquidTime.h"
#include "Store.h"
#include "StoreClient.h"
#include "HttpRequest.h"
#include "comm.h"
#include "MemBuf.h"
#include "http.h"

typedef struct _Countstr Countstr;

typedef struct _htcpHeader htcpHeader;

typedef struct _htcpDataHeader htcpDataHeader;

typedef struct _htcpDataHeaderSquid htcpDataHeaderSquid;

typedef struct _htcpAuthHeader htcpAuthHeader;

typedef struct _htcpStuff htcpStuff;

typedef struct _htcpDetail htcpDetail;

struct _Countstr
{
    u_int16_t length;
    char *text;
};

struct _htcpHeader
{
    u_int16_t length;
    u_char major;
    u_char minor;
};

struct _htcpDataHeaderSquid
{
    u_int16_t length;

#if !WORDS_BIGENDIAN
    unsigned int opcode:4;
    unsigned int response:4;
#else
    unsigned int response:4;
    unsigned int opcode:4;
#endif

#if !WORDS_BIGENDIAN
    unsigned int reserved:6;
    unsigned int F1:1;
    unsigned int RR:1;
#else
    unsigned int RR:1;
    unsigned int F1:1;
    unsigned int reserved:6;
#endif

    u_int32_t msg_id;
};

struct _htcpDataHeader
{
    u_int16_t length;

#if WORDS_BIGENDIAN
    u_int8_t opcode:4;
    u_int8_t response:4;
#else
    u_int8_t response:4;
    u_int8_t opcode:4;
#endif

#if WORDS_BIGENDIAN
    u_int8_t reserved:6;
    u_int8_t F1:1;
    u_int8_t RR:1;
#else
    u_int8_t RR:1;
    u_int8_t F1:1;
    u_int8_t reserved:6;
#endif

    u_int32_t msg_id;
};

/* RR == 0 --> F1 = RESPONSE DESIRED FLAG */
/* RR == 1 --> F1 = MESSAGE OVERALL FLAG */
/* RR == 0 --> REQUEST */
/* RR == 1 --> RESPONSE */

struct _htcpAuthHeader
{
    u_int16_t length;
    time_t sig_time;
    time_t sig_expire;
    Countstr key_name;
    Countstr signature;
};

class htcpSpecifier : public StoreClient
{

public:
    MEMPROXY_CLASS(htcpSpecifier);

    void created (StoreEntry *newEntry);
    void checkHit();
    void checkedHit(StoreEntry *e);

    void setFrom (IPAddress &from);
    void setDataHeader (htcpDataHeader *);
    char *method;
    char *uri;
    char *version;
    char *req_hdrs;
    HttpRequest *request;

private:
    HttpRequest *checkHitRequest;

    IPAddress from; // was a ptr. return to such IFF needed. otherwise copy should do.
    htcpDataHeader *dhdr;
};

MEMPROXY_CLASS_INLINE(htcpSpecifier)		/**DOCS_NOSEMI*/

struct _htcpDetail
{
    char *resp_hdrs;
    char *entity_hdrs;
    char *cache_hdrs;
};

struct _htcpStuff
{
    int op;
    int rr;
    int f1;
    int response;
    int reason;
    u_int32_t msg_id;
    htcpSpecifier S;
    htcpDetail D;
};

enum {
    HTCP_NOP,
    HTCP_TST,
    HTCP_MON,
    HTCP_SET,
    HTCP_CLR,
    HTCP_END
};

static const char *const htcpOpcodeStr[] =
    {
        "HTCP_NOP",
        "HTCP_TST",
        "HTCP_MON",
        "HTCP_SET",
        "HTCP_CLR",
        "HTCP_END"
    };

/*
 * values for htcpDataHeader->response
 */
enum {
    AUTH_REQUIRED,
    AUTH_FAILURE,
    OPCODE_UNIMPLEMENTED,
    MAJOR_VERSION_UNSUPPORTED,
    MINOR_VERSION_UNSUPPORTED,
    INVALID_OPCODE
};

/*
 * values for htcpDataHeader->RR
 */
enum {
    RR_REQUEST,
    RR_RESPONSE
};

static u_int32_t msg_id_counter = 0;
static int htcpInSocket = -1;
static int htcpOutSocket = -1;
#define N_QUERIED_KEYS 8192
static u_int32_t queried_id[N_QUERIED_KEYS];
static cache_key queried_keys[N_QUERIED_KEYS][SQUID_MD5_DIGEST_LENGTH];

static IPAddress queried_addr[N_QUERIED_KEYS];
static MemAllocator *htcpDetailPool = NULL;

static int old_squid_format = 0;


static ssize_t htcpBuildPacket(char *buf, size_t buflen, htcpStuff * stuff);
static htcpSpecifier *htcpUnpackSpecifier(char *buf, int sz);
static htcpDetail *htcpUnpackDetail(char *buf, int sz);
static ssize_t htcpBuildAuth(char *buf, size_t buflen);
static ssize_t htcpBuildCountstr(char *buf, size_t buflen, const char *s);
static ssize_t htcpBuildData(char *buf, size_t buflen, htcpStuff * stuff);
static ssize_t htcpBuildDetail(char *buf, size_t buflen, htcpStuff * stuff);
static ssize_t htcpBuildOpData(char *buf, size_t buflen, htcpStuff * stuff);
static ssize_t htcpBuildSpecifier(char *buf, size_t buflen, htcpStuff * stuff);
static ssize_t htcpBuildTstOpData(char *buf, size_t buflen, htcpStuff * stuff);
static void htcpFreeSpecifier(htcpSpecifier * s);
static void htcpFreeDetail(htcpDetail * s);

static void htcpHandle(char *buf, int sz, IPAddress &from);

static void htcpHandleMon(htcpDataHeader *, char *buf, int sz, IPAddress &from);

static void htcpHandleNop(htcpDataHeader *, char *buf, int sz, IPAddress &from);

static void htcpHandleSet(htcpDataHeader *, char *buf, int sz, IPAddress &from);

static void htcpHandleTst(htcpDataHeader *, char *buf, int sz, IPAddress &from);
static void htcpRecv(int fd, void *data);

static void htcpSend(const char *buf, int len, IPAddress &to);

static void htcpTstReply(htcpDataHeader *, StoreEntry *, htcpSpecifier *, IPAddress &);

static void htcpHandleTstRequest(htcpDataHeader *, char *buf, int sz, IPAddress &from);

static void htcpHandleTstResponse(htcpDataHeader *, char *, int, IPAddress &);

static void
htcpHexdump(const char *tag, const char *s, int sz)
{
#if USE_HEXDUMP
    int i;
    int k;
    char hex[80];
    debugs(31, 3, "htcpHexdump " << tag);
    memset(hex, '\0', 80);

    for (i = 0; i < sz; i++) {
        k = i % 16;
        snprintf(&hex[k * 3], 4, " %02x", (int) *(s + i));

        if (k < 15 && i < (sz - 1))
            continue;

        debugs(31, 3, "\t" << hex);

        memset(hex, '\0', 80);
    }

#endif
}

/*
 * STUFF FOR SENDING HTCP MESSAGES
 */

static ssize_t
htcpBuildAuth(char *buf, size_t buflen)
{
    htcpAuthHeader auth;
    size_t copy_sz = 0;
    assert(2 == sizeof(u_int16_t));
    auth.length = htons(2);
    copy_sz += 2;
    if (buflen < copy_sz)
	return -1;
    xmemcpy(buf, &auth, copy_sz);
    return copy_sz;
}

static ssize_t
htcpBuildCountstr(char *buf, size_t buflen, const char *s)
{
    u_int16_t length;
    size_t len;
    int off = 0;

    if (buflen - off < 2)
        return -1;

    if (s)
        len = strlen(s);
    else
        len = 0;

    debugs(31, 3, "htcpBuildCountstr: LENGTH = " << len);

    debugs(31, 3, "htcpBuildCountstr: TEXT = {" << (s ? s : "<NULL>") << "}");

    length = htons((u_int16_t) len);

    xmemcpy(buf + off, &length, 2);

    off += 2;

    if (buflen - off < len)
        return -1;

    if (len)
        xmemcpy(buf + off, s, len);

    off += len;

    return off;
}

static ssize_t
htcpBuildSpecifier(char *buf, size_t buflen, htcpStuff * stuff)
{
    ssize_t off = 0;
    ssize_t s;
    s = htcpBuildCountstr(buf + off, buflen - off, stuff->S.method);

    if (s < 0)
        return s;

    off += s;

    s = htcpBuildCountstr(buf + off, buflen - off, stuff->S.uri);

    if (s < 0)
        return s;

    off += s;

    s = htcpBuildCountstr(buf + off, buflen - off, stuff->S.version);

    if (s < 0)
        return s;

    off += s;

    s = htcpBuildCountstr(buf + off, buflen - off, stuff->S.req_hdrs);

    if (s < 0)
        return s;

    off += s;

    debugs(31, 3, "htcpBuildSpecifier: size " << off);

    return off;
}

static ssize_t
htcpBuildDetail(char *buf, size_t buflen, htcpStuff * stuff)
{
    ssize_t off = 0;
    ssize_t s;
    s = htcpBuildCountstr(buf + off, buflen - off, stuff->D.resp_hdrs);

    if (s < 0)
        return s;

    off += s;

    s = htcpBuildCountstr(buf + off, buflen - off, stuff->D.entity_hdrs);

    if (s < 0)
        return s;

    off += s;

    s = htcpBuildCountstr(buf + off, buflen - off, stuff->D.cache_hdrs);

    if (s < 0)
        return s;

    off += s;

    return off;
}

static ssize_t
htcpBuildTstOpData(char *buf, size_t buflen, htcpStuff * stuff)
{
    switch (stuff->rr) {

    case RR_REQUEST:
        debugs(31, 3, "htcpBuildTstOpData: RR_REQUEST");
        return htcpBuildSpecifier(buf, buflen, stuff);

    case RR_RESPONSE:
        debugs(31, 3, "htcpBuildTstOpData: RR_RESPONSE");
        debugs(31, 3, "htcpBuildTstOpData: F1 = " << stuff->f1);

        if (stuff->f1)		/* cache miss */
            return 0;
        else			/* cache hit */
            return htcpBuildDetail(buf, buflen, stuff);

    default:
        fatal_dump("htcpBuildTstOpData: bad RR value");
    }

    return 0;
}

static ssize_t
htcpBuildClrOpData(char *buf, size_t buflen, htcpStuff * stuff)
{
    u_short reason;
    
    switch (stuff->rr) {
    case RR_REQUEST:
        debugs(31, 3, "htcpBuildClrOpData: RR_REQUEST");
        reason = htons((u_short)stuff->reason);
        xmemcpy(buf, &reason, 2);
        return htcpBuildSpecifier(buf + 2, buflen - 2, stuff) + 2;
    case RR_RESPONSE:
        break;
    default:
        fatal_dump("htcpBuildClrOpData: bad RR value");
    }
    
    return 0;
}

static ssize_t
htcpBuildOpData(char *buf, size_t buflen, htcpStuff * stuff)
{
    ssize_t off = 0;
    debugs(31, 3, "htcpBuildOpData: opcode " << htcpOpcodeStr[stuff->op]);

    switch (stuff->op) {

    case HTCP_TST:
        off = htcpBuildTstOpData(buf + off, buflen, stuff);
        break;

    case HTCP_CLR:
        off = htcpBuildClrOpData(buf + off, buflen, stuff);
        break;

    default:
        assert(0);
        break;
    }

    return off;
}

static ssize_t
htcpBuildData(char *buf, size_t buflen, htcpStuff * stuff)
{
    ssize_t off = 0;
    ssize_t op_data_sz;
    size_t hdr_sz = sizeof(htcpDataHeader);
    htcpDataHeader hdr;

    if (buflen < hdr_sz)
        return -1;

    off += hdr_sz;		/* skip! */

    op_data_sz = htcpBuildOpData(buf + off, buflen - off, stuff);

    if (op_data_sz < 0)
        return op_data_sz;

    off += op_data_sz;

    debugs(31, 3, "htcpBuildData: hdr.length = " << off);

    hdr.length = (u_int16_t) off;

    hdr.opcode = stuff->op;

    hdr.response = stuff->response;

    hdr.RR = stuff->rr;

    hdr.F1 = stuff->f1;

    hdr.msg_id = stuff->msg_id;

    /* convert multi-byte fields */
    hdr.length = htons(hdr.length);

    hdr.msg_id = htonl(hdr.msg_id);

    if (!old_squid_format) {
        xmemcpy(buf, &hdr, hdr_sz);
    } else {
        htcpDataHeaderSquid hdrSquid;
        memset(&hdrSquid, 0, sizeof(hdrSquid));
        hdrSquid.length = hdr.length;
        hdrSquid.opcode = hdr.opcode;
        hdrSquid.response = hdr.response;
        hdrSquid.F1 = hdr.F1;
        hdrSquid.RR = hdr.RR;
        xmemcpy(buf, &hdrSquid, hdr_sz);
    }

    debugs(31, 3, "htcpBuildData: size " << off);

    return off;
}

/*
 * Build an HTCP packet into buf, maximum length buflen.
 * Returns the packet length, or zero on failure.
 */
static ssize_t
htcpBuildPacket(char *buf, size_t buflen, htcpStuff * stuff)
{
    ssize_t s;
    ssize_t off = 0;
    size_t hdr_sz = sizeof(htcpHeader);
    htcpHeader hdr;
    /* skip the header -- we don't know the overall length */

    if (buflen < hdr_sz) {
        return 0;
    }

    off += hdr_sz;
    s = htcpBuildData(buf + off, buflen - off, stuff);

    if (s < 0) {
        return 0;
    }

    off += s;
    s = htcpBuildAuth(buf + off, buflen - off);

    if (s < 0) {
        return 0;
    }

    off += s;
    hdr.length = htons((u_int16_t) off);
    hdr.major = 0;

    if (old_squid_format)
        hdr.minor = 0;
    else
        hdr.minor = 1;

    xmemcpy(buf, &hdr, hdr_sz);

    debugs(31, 3, "htcpBuildPacket: size " << off);

    return off;
}

static void

htcpSend(const char *buf, int len, IPAddress &to)
{
    int x;

    debugs(31, 3, "htcpSend: " << to );
    htcpHexdump("htcpSend", buf, len);

    x = comm_udp_sendto(htcpOutSocket,
                        to,
                        buf,
                        len);

    if (x < 0)
        debugs(31, 1, "htcpSend: FD " << htcpOutSocket << " sendto: " << xstrerror());
    else
        statCounter.htcp.pkts_sent++;
}

/*
 * STUFF FOR RECEIVING HTCP MESSAGES
 */

void

htcpSpecifier::setFrom (IPAddress &aSocket)
{
    from = aSocket;
}

void
htcpSpecifier::setDataHeader (htcpDataHeader *aDataHeader)
{
    dhdr = aDataHeader;
}

static void
htcpFreeSpecifier(htcpSpecifier * s)
{
    HTTPMSGUNLOCK(s->request);

    delete s;
}

static void
htcpFreeDetail(htcpDetail * d)
{
    htcpDetailPool->free(d);
}

/*
 * Unpack an HTCP SPECIFIER in place
 * This will overwrite any following AUTH block
 */
static htcpSpecifier *
htcpUnpackSpecifier(char *buf, int sz)
{
    htcpSpecifier *s = new htcpSpecifier;
    HttpRequestMethod method;

    /* Find length of METHOD */
    u_int16_t l = ntohs(*(u_int16_t *) buf);
    sz -= 2;
    buf += 2;

    if (l > sz) {
        debugs(31, 1, "htcpUnpackSpecifier: failed to unpack METHOD");
        htcpFreeSpecifier(s);
        return NULL;
    }

    /* Set METHOD */
    s->method = buf;

    buf += l;

    sz -= l;

    /* Find length of URI */
    l = ntohs(*(u_int16_t *) buf);

    sz -= 2;

    if (l > sz) {
        debugs(31, 1, "htcpUnpackSpecifier: failed to unpack URI");
        htcpFreeSpecifier(s);
        return NULL;
    }

    /* Add terminating null to METHOD */
    *buf = '\0';

    /* Set URI */
    buf += 2;

    s->uri = buf;

    buf += l;

    sz -= l;

    /* Find length of VERSION */
    l = ntohs(*(u_int16_t *) buf);

    sz -= 2;

    if (l > sz) {
        debugs(31, 1, "htcpUnpackSpecifier: failed to unpack VERSION");
        htcpFreeSpecifier(s);
        return NULL;
    }

    /* Add terminating null to URI */
    *buf = '\0';

    /* Set VERSION */
    buf += 2;

    s->version = buf;

    buf += l;

    sz -= l;

    /* Find length of REQ-HDRS */
    l = ntohs(*(u_int16_t *) buf);

    sz -= 2;

    if (l > sz) {
        debugs(31, 1, "htcpUnpackSpecifier: failed to unpack REQ-HDRS");
        htcpFreeSpecifier(s);
        return NULL;
    }

    /* Add terminating null to URI */
    *buf = '\0';

    /* Set REQ-HDRS */
    buf += 2;

    s->req_hdrs = buf;

    buf += l;

    sz -= l;

    debugs(31, 3, "htcpUnpackSpecifier: " << sz << " bytes left");

    /*
     * Add terminating null to REQ-HDRS. This is possible because we allocated 
     * an extra byte when we received the packet. This will overwrite any following
     * AUTH block.
     */
    *buf = '\0';

    /*
     * Parse the request
     */
    method = HttpRequestMethod(s->method, NULL);

    s->request = HttpRequest::CreateFromUrlAndMethod(s->uri, method == METHOD_NONE ? HttpRequestMethod(METHOD_GET) : method);

    if (s->request)
       HTTPMSGLOCK(s->request);

    return s;
}

/*
 * Unpack an HTCP DETAIL in place
 * This will overwrite any following AUTH block
 */
static htcpDetail *
htcpUnpackDetail(char *buf, int sz)
{
    htcpDetail *d = static_cast<htcpDetail *>(htcpDetailPool->alloc());

    /* Find length of RESP-HDRS */
    u_int16_t l = ntohs(*(u_int16_t *) buf);
    sz -= 2;
    buf += 2;

    if (l > sz) {
        debugs(31, 1, "htcpUnpackDetail: failed to unpack RESP_HDRS");
        htcpFreeDetail(d);
        return NULL;
    }

    /* Set RESP-HDRS */
    d->resp_hdrs = buf;

    buf += l;

    sz -= l;

    /* Find length of ENTITY-HDRS */
    l = ntohs(*(u_int16_t *) buf);

    sz -= 2;

    if (l > sz) {
        debugs(31, 1, "htcpUnpackDetail: failed to unpack ENTITY_HDRS");
        htcpFreeDetail(d);
        return NULL;
    }

    /* Add terminating null to RESP-HDRS */
    *buf = '\0';

    /* Set ENTITY-HDRS */
    buf += 2;

    d->entity_hdrs = buf;

    buf += l;

    sz -= l;

    /* Find length of CACHE-HDRS */
    l = ntohs(*(u_int16_t *) buf);

    sz -= 2;

    if (l > sz) {
        debugs(31, 1, "htcpUnpackDetail: failed to unpack CACHE_HDRS");
        htcpFreeDetail(d);
        return NULL;
    }

    /* Add terminating null to ENTITY-HDRS */
    *buf = '\0';

    /* Set CACHE-HDRS */
    buf += 2;

    d->cache_hdrs = buf;

    buf += l;

    sz -= l;

    debugs(31, 3, "htcpUnpackDetail: " << sz << " bytes left");

    /*
     * Add terminating null to CACHE-HDRS. This is possible because we allocated 
     * an extra byte when we received the packet. This will overwrite any following
     * AUTH block.
     */
    *buf = '\0';

    return d;
}

static int

htcpAccessCheck(acl_access * acl, htcpSpecifier * s, IPAddress &from)
{
    ACLChecklist checklist;
    checklist.src_addr = from;
    checklist.my_addr.SetNoAddr();
    checklist.request = HTTPMSGLOCK(s->request);
    checklist.accessList = cbdataReference(acl);
    /* cbdataReferenceDone() happens in either fastCheck() or ~ACLCheckList */
    int result = checklist.fastCheck();
    return result;
}

static void

htcpTstReply(htcpDataHeader * dhdr, StoreEntry * e, htcpSpecifier * spec, IPAddress &from)
{
    htcpStuff stuff;
    static char pkt[8192];
    HttpHeader hdr(hoHtcpReply);
    MemBuf mb;
    Packer p;
    ssize_t pktlen;
    char *host;
    int rtt = 0;
    int hops = 0;
    int samp = 0;
    char cto_buf[128];
    memset(&stuff, '\0', sizeof(stuff));
    stuff.op = HTCP_TST;
    stuff.rr = RR_RESPONSE;
    stuff.f1 = 0;
    stuff.response = e ? 0 : 1;
    debugs(31, 3, "htcpTstReply: response = " << stuff.response);
    stuff.msg_id = dhdr->msg_id;

    if (spec)
    {
        mb.init();
        packerToMemInit(&p, &mb);
        stuff.S.method = spec->method;
        stuff.S.uri = spec->uri;
        stuff.S.version = spec->version;
        stuff.S.req_hdrs = spec->req_hdrs;
        hdr.putInt(HDR_AGE,
                   e->timestamp <= squid_curtime ?
                   squid_curtime - e->timestamp : 0);
        hdr.packInto(&p);
        stuff.D.resp_hdrs = xstrdup(mb.buf);
        debugs(31, 3, "htcpTstReply: resp_hdrs = {" << stuff.D.resp_hdrs << "}");
        mb.reset();
        hdr.reset();

        if (e->expires > -1)
            hdr.putTime(HDR_EXPIRES, e->expires);

        if (e->lastmod > -1)
            hdr.putTime(HDR_LAST_MODIFIED, e->lastmod);

        hdr.packInto(&p);

        stuff.D.entity_hdrs = xstrdup(mb.buf);

        debugs(31, 3, "htcpTstReply: entity_hdrs = {" << stuff.D.entity_hdrs << "}");

        mb.reset();

        hdr.reset();

        if ((host = urlHostname(spec->uri))) {
            netdbHostData(host, &samp, &rtt, &hops);

            if (rtt || hops) {
                snprintf(cto_buf, 128, "%s %d %f %d",
                         host, samp, 0.001 * rtt, hops);
                hdr.putExt("Cache-to-Origin", cto_buf);
            }
        }

        hdr.packInto(&p);
        stuff.D.cache_hdrs = xstrdup(mb.buf);
        debugs(31, 3, "htcpTstReply: cache_hdrs = {" << stuff.D.cache_hdrs << "}");
        mb.clean();
        hdr.clean();
        packerClean(&p);
    }

    pktlen = htcpBuildPacket(pkt, sizeof(pkt), &stuff);

    safe_free(stuff.D.resp_hdrs);
    safe_free(stuff.D.entity_hdrs);
    safe_free(stuff.D.cache_hdrs);

    if (!pktlen)
    {
        debugs(31, 1, "htcpTstReply: htcpBuildPacket() failed");
        return;
    }

    htcpSend(pkt, (int) pktlen, from);
}

static void

htcpClrReply(htcpDataHeader * dhdr, int purgeSucceeded, IPAddress &from)
{
    htcpStuff stuff;
    static char pkt[8192];
    ssize_t pktlen;

    /* If dhdr->F1 == 0, no response desired */

    if (dhdr->F1 == 0)
        return;

    memset(&stuff, '\0', sizeof(stuff));

    stuff.op = HTCP_CLR;

    stuff.rr = RR_RESPONSE;

    stuff.f1 = 0;

    stuff.response = purgeSucceeded ? 0 : 2;

    debugs(31, 3, "htcpClrReply: response = " << stuff.response);

    stuff.msg_id = dhdr->msg_id;

    pktlen = htcpBuildPacket(pkt, sizeof(pkt), &stuff);

    if (pktlen == 0)
    {
        debugs(31, 1, "htcpClrReply: htcpBuildPacket() failed");
        return;
    }

    htcpSend(pkt, (int) pktlen, from);
}

static void

htcpHandleNop(htcpDataHeader * hdr, char *buf, int sz, IPAddress &from)
{
    debugs(31, 3, "htcpHandleNop: Unimplemented");
}

void
htcpSpecifier::checkHit()
{
    char *blk_end;
    checkHitRequest = request;

    if (NULL == checkHitRequest) {
        debugs(31, 3, "htcpCheckHit: NO; failed to parse URL");
        checkedHit(NullStoreEntry::getInstance());
        return;
    }

    blk_end = req_hdrs + strlen(req_hdrs);

    if (!checkHitRequest->header.parse(req_hdrs, blk_end)) {
        debugs(31, 3, "htcpCheckHit: NO; failed to parse request headers");
        delete checkHitRequest;
        checkHitRequest = NULL;
        checkedHit(NullStoreEntry::getInstance());
        return;
    }

    StoreEntry::getPublicByRequest(this, checkHitRequest);
}

void
htcpSpecifier::created (StoreEntry *e)
{
    StoreEntry *hit=NULL;
    assert (e);

    if (e->isNull()) {
        debugs(31, 3, "htcpCheckHit: NO; public object not found");
    }
    else if (!e->validToSend()) {
        debugs(31, 3, "htcpCheckHit: NO; entry not valid to send" );
    }
    else if (refreshCheckHTCP(e, checkHitRequest)) {
        debugs(31, 3, "htcpCheckHit: NO; cached response is stale");
    }
    else {
        debugs(31, 3, "htcpCheckHit: YES!?");
        hit = e;
    }

    checkedHit (hit);
}

static void
htcpClrStoreEntry(StoreEntry * e)
{
    debugs(31, 4, "htcpClrStoreEntry: Clearing store for entry: " << e->url()  );
    e->releaseRequest();
}

static int
htcpClrStore(const htcpSpecifier * s)
{
    HttpRequest *request = s->request;
    char *blk_end;
    StoreEntry *e = NULL;
    int released = 0;

    if (request == NULL) {
        debugs(31, 3, "htcpClrStore: failed to parse URL");
        return -1;
    }

    /* Parse request headers */
    blk_end = s->req_hdrs + strlen(s->req_hdrs);

    if (!request->header.parse(s->req_hdrs, blk_end)) {
        debugs(31, 2, "htcpClrStore: failed to parse request headers");
        return -1;
    }

    /* Lookup matching entries. This matches both GET and HEAD */
    while ((e = storeGetPublicByRequest(request)) != NULL) {
        if (e != NULL) {
            htcpClrStoreEntry(e);
            released++;
        }
    }

    if (released) {
        debugs(31, 4, "htcpClrStore: Cleared " << released << " matching entries");
        return 1;
    } else {
        debugs(31, 4, "htcpClrStore: No matching entry found");
        return 0;
    }
}

static void

htcpHandleTst(htcpDataHeader * hdr, char *buf, int sz, IPAddress &from)
{
    debugs(31, 3, "htcpHandleTst: sz = " << sz);

    if (hdr->RR == RR_REQUEST)
        htcpHandleTstRequest(hdr, buf, sz, from);
    else
        htcpHandleTstResponse(hdr, buf, sz, from);
}

HtcpReplyData::HtcpReplyData() : hdr(hoHtcpReply)
{}

static void

htcpHandleTstResponse(htcpDataHeader * hdr, char *buf, int sz, IPAddress &from)
{
    htcpReplyData htcpReply;
    cache_key *key = NULL;

    IPAddress *peer;
    htcpDetail *d = NULL;
    char *t;

    if (queried_id[hdr->msg_id % N_QUERIED_KEYS] != hdr->msg_id)
    {
        debugs(31, 2, "htcpHandleTstResponse: No matching query id '" <<
               hdr->msg_id << "' (expected " <<
               queried_id[hdr->msg_id % N_QUERIED_KEYS] << ") from '" <<
               from << "'");

        return;
    }

    key = queried_keys[hdr->msg_id % N_QUERIED_KEYS];

    if (!key)
    {
        debugs(31, 1, "htcpHandleTstResponse: No query key for response id '" << hdr->msg_id << "' from '" << from << "'");
        return;
    }

    peer = &queried_addr[hdr->msg_id % N_QUERIED_KEYS];

    if ( *peer != from || peer->GetPort() != from.GetPort() )
    {
        debugs(31, 1, "htcpHandleTstResponse: Unexpected response source " << from );
        return;
    }

    if (hdr->F1 == 1)
    {
        debugs(31, 2, "htcpHandleTstResponse: error condition, F1/MO == 1");
        return;
    }

    htcpReply.msg_id = hdr->msg_id;
    debugs(31, 3, "htcpHandleTstResponse: msg_id = " << htcpReply.msg_id);
    htcpReply.hit = hdr->response ? 0 : 1;

    if (hdr->F1)
    {
        debugs(31, 3, "htcpHandleTstResponse: MISS");
    } else
    {
        debugs(31, 3, "htcpHandleTstResponse: HIT");
        d = htcpUnpackDetail(buf, sz);

        if (d == NULL) {
            debugs(31, 1, "htcpHandleTstResponse: bad DETAIL");
            return;
        }

        if ((t = d->resp_hdrs))
            htcpReply.hdr.parse(t, t + strlen(t));

        if ((t = d->entity_hdrs))
            htcpReply.hdr.parse(t, t + strlen(t));

        if ((t = d->cache_hdrs))
            htcpReply.hdr.parse(t, t + strlen(t));
    }

    debugs(31, 3, "htcpHandleTstResponse: key (" << key << ") " << storeKeyText(key));
    neighborsHtcpReply(key, &htcpReply, from);
    htcpReply.hdr.clean();

    if (d)
        htcpFreeDetail(d);
}

static void

htcpHandleTstRequest(htcpDataHeader * dhdr, char *buf, int sz, IPAddress &from)
{
    /* buf should be a SPECIFIER */
    htcpSpecifier *s;

    if (sz == 0)
    {
        debugs(31, 3, "htcpHandleTst: nothing to do");
        return;
    }

    if (dhdr->F1 == 0)
        return;

    /* s is a new object */
    s = htcpUnpackSpecifier(buf, sz);

    s->setFrom (from);

    s->setDataHeader (dhdr);

    if (NULL == s)
    {
        debugs(31, 2, "htcpHandleTstRequest: htcpUnpackSpecifier failed");
        return;
    }

    if (!s->request)
    {
        debugs(31, 2, "htcpHandleTstRequest: failed to parse request");
        htcpFreeSpecifier(s);
        return;
    }

    if (!htcpAccessCheck(Config.accessList.htcp, s, from))
    {
        debugs(31, 2, "htcpHandleTstRequest: Access denied");
        htcpFreeSpecifier(s);
        return;
    }

    debugs(31, 3, "htcpHandleTstRequest: " << s->method << " " << s->uri << " " << s->version);
    debugs(31, 3, "htcpHandleTstRequest: " << s->req_hdrs);
    s->checkHit();
}

void
htcpSpecifier::checkedHit(StoreEntry *e)
{
    if (e)
        htcpTstReply(dhdr, e, this, from);		/* hit */
    else
        htcpTstReply(dhdr, NULL, NULL, from);	/* cache miss */

    htcpFreeSpecifier(this);
}

static void

htcpHandleMon(htcpDataHeader * hdr, char *buf, int sz, IPAddress &from)
{
    debugs(31, 3, "htcpHandleMon: Unimplemented");
}

static void

htcpHandleSet(htcpDataHeader * hdr, char *buf, int sz, IPAddress &from)
{
    debugs(31, 3, "htcpHandleSet: Unimplemented");
}

static void

htcpHandleClr(htcpDataHeader * hdr, char *buf, int sz, IPAddress &from)
{
    htcpSpecifier *s;
    /* buf[0/1] is reserved and reason */
    int reason = buf[1] << 4;
    debugs(31, 3, "htcpHandleClr: reason=" << reason);
    buf += 2;
    sz -= 2;

    /* buf should be a SPECIFIER */

    if (sz == 0)
    {
        debugs(31, 4, "htcpHandleClr: nothing to do");
        return;
    }

    s = htcpUnpackSpecifier(buf, sz);

    if (NULL == s)
    {
        debugs(31, 3, "htcpHandleClr: htcpUnpackSpecifier failed");
        return;
    }

    if (!htcpAccessCheck(Config.accessList.htcp_clr, s, from))
    {
        debugs(31, 2, "htcpHandleClr: Access denied");
        htcpFreeSpecifier(s);
        return;
    }

    debugs(31, 5, "htcpHandleClr: " << s->method << " " << s->uri << " " << s->version);
    debugs(31, 5, "htcpHandleClr: request headers: " << s->req_hdrs);

    /* Release objects from cache
     * analog to clientPurgeRequest in client_side.c
     */

    switch (htcpClrStore(s))
    {

    case 1:
        htcpClrReply(hdr, 1, from);	/* hit */
        break;

    case 0:
        htcpClrReply(hdr, 0, from);	/* miss */
        break;

    default:
        break;
    }

    htcpFreeSpecifier(s);
}

static void
htcpForwardClr(char *buf, int sz)
{
    peer *p;
    
    for (p = Config.peers; p; p = p->next) {
        if (!p->options.htcp) {
            continue;
        }
        if (!p->options.htcp_forward_clr) {
            continue;
        }
        
        htcpSend(buf, sz, p->in_addr);
    }
}

static void
htcpHandle(char *buf, int sz, IPAddress &from)
{
    htcpHeader htcpHdr;
    htcpDataHeader hdr;
    char *hbuf;
    int hsz;
    assert (sz >= 0);

    if ((size_t)sz < sizeof(htcpHeader))
    {
        debugs(31, 1, "htcpHandle: msg size less than htcpHeader size");
        return;
    }

    htcpHexdump("htcpHandle", buf, sz);
    xmemcpy(&htcpHdr, buf, sizeof(htcpHeader));
    htcpHdr.length = ntohs(htcpHdr.length);

    if (htcpHdr.minor == 0)
        old_squid_format = 1;
    else
        old_squid_format = 0;

    debugs(31, 3, "htcpHandle: htcpHdr.length = " << htcpHdr.length);
    debugs(31, 3, "htcpHandle: htcpHdr.major = " << htcpHdr.major);
    debugs(31, 3, "htcpHandle: htcpHdr.minor = " << htcpHdr.minor);

    if (sz != htcpHdr.length)
    {
        debugs(31, 1, "htcpHandle: sz/" << sz << " != htcpHdr.length/" <<
               htcpHdr.length << " from " << from );

        return;
    }

    if (htcpHdr.major != 0)
    {
        debugs(31, 1, "htcpHandle: Unknown major version " << htcpHdr.major << " from " << from );

        return;
    }

    hbuf = buf + sizeof(htcpHeader);
    hsz = sz - sizeof(htcpHeader);

    if ((size_t)hsz < sizeof(htcpDataHeader))
    {
        debugs(31, 1, "htcpHandleData: msg size less than htcpDataHeader size");
        return;
    }

    if (!old_squid_format)
    {
        xmemcpy(&hdr, hbuf, sizeof(hdr));
    } else {
        htcpDataHeaderSquid hdrSquid;
        xmemcpy(&hdrSquid, hbuf, sizeof(hdrSquid));
        hdr.length = hdrSquid.length;
        hdr.opcode = hdrSquid.opcode;
        hdr.response = hdrSquid.response;
        hdr.F1 = hdrSquid.F1;
        hdr.RR = hdrSquid.RR;
        hdr.reserved = 0;
        hdr.msg_id = hdrSquid.msg_id;
    }

    hdr.length = ntohs(hdr.length);
    hdr.msg_id = ntohl(hdr.msg_id);
    debugs(31, 3, "htcpHandleData: hsz = " << hsz);
    debugs(31, 3, "htcpHandleData: length = " << hdr.length);

    if (hdr.opcode >= HTCP_END) {
        debugs(31, 1, "htcpHandleData: client " << from << ", opcode " << hdr.opcode << " out of range");
        return;
    }

    debugs(31, 3, "htcpHandleData: opcode = " << hdr.opcode << " " << htcpOpcodeStr[hdr.opcode]);
    debugs(31, 3, "htcpHandleData: response = " << hdr.response);
    debugs(31, 3, "htcpHandleData: F1 = " << hdr.F1);
    debugs(31, 3, "htcpHandleData: RR = " << hdr.RR);
    debugs(31, 3, "htcpHandleData: msg_id = " << hdr.msg_id);

    if (hsz < hdr.length) {
        debugs(31, 1, "htcpHandleData: sz < hdr.length");
        return;
    }

    /*
     * set sz = hdr.length so we ignore any AUTH fields following
     * the DATA.
     */
    hsz = (int) hdr.length;
    hbuf += sizeof(htcpDataHeader);
    hsz -= sizeof(htcpDataHeader);
    debugs(31, 3, "htcpHandleData: hsz = " << hsz);

    htcpHexdump("htcpHandleData", hbuf, hsz);

    switch (hdr.opcode) {
    case HTCP_NOP:
        htcpHandleNop(&hdr, hbuf, hsz, from);
        break;
    case HTCP_TST:
        htcpHandleTst(&hdr, hbuf, hsz, from);
        break;
    case HTCP_MON:
        htcpHandleMon(&hdr, hbuf, hsz, from);
        break;
    case HTCP_SET:
        htcpHandleSet(&hdr, hbuf, hsz, from);
        break;
    case HTCP_CLR:
        htcpHandleClr(&hdr, hbuf, hsz, from);
        htcpForwardClr(buf, sz);
        break;
    default:
        break;
    }
}

static void
htcpRecv(int fd, void *data)
{
    static char buf[8192];
    int len;
    static IPAddress from;

    /* Receive up to 8191 bytes, leaving room for a null */

    len = comm_udp_recvfrom(fd, buf, sizeof(buf) - 1, 0, from);

    debugs(31, 3, "htcpRecv: FD " << fd << ", " << len << " bytes from " << from );

    if (len)
        statCounter.htcp.pkts_recv++;

    htcpHandle(buf, len, from);

    commSetSelect(fd, COMM_SELECT_READ, htcpRecv, NULL, 0);
}

/*
 * ======================================================================
 * PUBLIC FUNCTIONS
 * ======================================================================
 */

void
htcpInit(void)
{
    IPAddress sendOn;

    if (Config.Port.htcp <= 0) {
        debugs(31, 1, "HTCP Disabled.");
        return;
    }
    sendOn = Config.Addrs.udp_outgoing;
    sendOn.SetPort(Config.Port.htcp);

    enter_suid();
    htcpInSocket = comm_open(SOCK_DGRAM,
                             IPPROTO_UDP,
                             sendOn,
                             COMM_NONBLOCKING,
                             "HTCP Socket");
    leave_suid();

    if (htcpInSocket < 0)
        fatal("Cannot open HTCP Socket");

    commSetSelect(htcpInSocket, COMM_SELECT_READ, htcpRecv, NULL, 0);

    debugs(31, 1, "Accepting HTCP messages on port " << Config.Port.htcp << ", FD " << htcpInSocket << ".");

    if (!Config.Addrs.udp_outgoing.IsNoAddr()) {
        enter_suid();
        htcpOutSocket = comm_open(SOCK_DGRAM,
                                  IPPROTO_UDP,
                                  sendOn,
                                  COMM_NONBLOCKING,
                                  "Outgoing HTCP Socket");
        leave_suid();

        if (htcpOutSocket < 0)
            fatal("Cannot open Outgoing HTCP Socket");

        commSetSelect(htcpOutSocket, COMM_SELECT_READ, htcpRecv, NULL, 0);

        debugs(31, 1, "Outgoing HTCP messages on port " << Config.Port.htcp << ", FD " << htcpOutSocket << ".");

        fd_note(htcpInSocket, "Incoming HTCP socket");
    } else {
        htcpOutSocket = htcpInSocket;
    }

    if (!htcpDetailPool) {
        htcpDetailPool = memPoolCreate("htcpDetail", sizeof(htcpDetail));
    }
}

void
htcpQuery(StoreEntry * e, HttpRequest * req, peer * p)
{
    cache_key *save_key;
    static char pkt[8192];
    ssize_t pktlen;
    char vbuf[32];
    htcpStuff stuff;
    HttpHeader hdr(hoRequest);
    Packer pa;
    MemBuf mb;
    http_state_flags flags;

    if (htcpInSocket < 0)
        return;

    old_squid_format = p->options.htcp_oldsquid;
    memset(&flags, '\0', sizeof(flags));
    snprintf(vbuf, sizeof(vbuf), "%d/%d",
             req->http_ver.major, req->http_ver.minor);
    stuff.op = HTCP_TST;
    stuff.rr = RR_REQUEST;
    stuff.f1 = 1;
    stuff.response = 0;
    stuff.msg_id = ++msg_id_counter;
    stuff.S.method = (char *) RequestMethodStr(req->method);
    stuff.S.uri = (char *) e->url();
    stuff.S.version = vbuf;
    HttpStateData::httpBuildRequestHeader(req, req, e, &hdr, flags);
    mb.init();
    packerToMemInit(&pa, &mb);
    hdr.packInto(&pa);
    hdr.clean();
    packerClean(&pa);
    stuff.S.req_hdrs = mb.buf;
    pktlen = htcpBuildPacket(pkt, sizeof(pkt), &stuff);
    mb.clean();
    if (!pktlen) {
        debugs(31, 1, "htcpQuery: htcpBuildPacket() failed");
        return;
    }
    
    htcpSend(pkt, (int) pktlen, p->in_addr);

    queried_id[stuff.msg_id % N_QUERIED_KEYS] = stuff.msg_id;
    save_key = queried_keys[stuff.msg_id % N_QUERIED_KEYS];
    storeKeyCopy(save_key, (const cache_key *)e->key);
    queried_addr[stuff.msg_id % N_QUERIED_KEYS] = p->in_addr;
    debugs(31, 3, "htcpQuery: key (" << save_key << ") " << storeKeyText(save_key));
}

void
htcpClear(StoreEntry * e, const char *uri, HttpRequest * req, HttpRequestMethod * method, peer * p, htcp_clr_reason reason)
{
    static char pkt[8192];
    ssize_t pktlen;
    char vbuf[32];
    htcpStuff stuff;
    HttpHeader hdr;
    Packer pa;
    MemBuf mb;
    http_state_flags flags;

    if (htcpInSocket < 0)
    	return;

    old_squid_format = p->options.htcp_oldsquid;
    memset(&flags, '\0', sizeof(flags));
    snprintf(vbuf, sizeof(vbuf), "%d/%d",
	req->http_ver.major, req->http_ver.minor);
    stuff.op = HTCP_CLR;
    stuff.rr = RR_REQUEST;
    stuff.f1 = 0;
    stuff.response = 0;
    stuff.msg_id = ++msg_id_counter;
    switch (reason) {
    case HTCP_CLR_INVALIDATION:
    	stuff.reason = 1;
    	break;
    default:
    	stuff.reason = 0;
    	break;
    }
    stuff.S.method = (char *) RequestMethodStr(req->method);
    if (e == NULL || e->mem_obj == NULL) {
    	if (uri == NULL) {
            return;
    	}
    	stuff.S.uri = xstrdup(uri);
    } else {
    	stuff.S.uri = (char *) e->url();
    }
    stuff.S.version = vbuf;
    if (reason != HTCP_CLR_INVALIDATION) {
        HttpStateData::httpBuildRequestHeader(req, req, e, &hdr, flags);
        mb.init();
        packerToMemInit(&pa, &mb);
        hdr.packInto(&pa);
        hdr.clean();
        packerClean(&pa);
    	stuff.S.req_hdrs = mb.buf;
    }
    pktlen = htcpBuildPacket(pkt, sizeof(pkt), &stuff);
    if (reason != HTCP_CLR_INVALIDATION) {
        mb.clean();
    }
    if (e == NULL) {
    	xfree(stuff.S.uri);
    }
    if (!pktlen) {
    	debug(31, 1) ("htcpQuery: htcpBuildPacket() failed\n");
    	return;
    }
    
    htcpSend(pkt, (int) pktlen, p->in_addr);
}

/*
 * htcpSocketShutdown only closes the 'in' socket if it is
 * different than the 'out' socket.
 */
void
htcpSocketShutdown(void)
{
    if (htcpInSocket < 0)
        return;

    if (htcpInSocket != htcpOutSocket) {
        debugs(12, 1, "FD " << htcpInSocket << " Closing HTCP socket");
        comm_close(htcpInSocket);
    }

    /*
     * Here we set 'htcpInSocket' to -1 even though the HTCP 'in'
     * and 'out' sockets might be just one FD.  This prevents this
     * function from executing repeatedly.  When we are really ready to
     * exit or restart, main will comm_close the 'out' descriptor.
     */
    htcpInSocket = -1;

    /*
     * Normally we only write to the outgoing HTCP socket, but
     * we also have a read handler there to catch messages sent
     * to that specific interface.  During shutdown, we must
     * disable reading on the outgoing socket.
     */
    /* XXX Don't we need this handler to read replies while shutting down?
     * I think there should be a separate hander for reading replies..
     */
    assert(htcpOutSocket > -1);

    commSetSelect(htcpOutSocket, COMM_SELECT_READ, NULL, NULL, 0);
}

void
htcpSocketClose(void)
{
    htcpSocketShutdown();

    if (htcpOutSocket > -1) {
        debugs(12, 1, "FD " << htcpOutSocket << " Closing HTCP socket");
        comm_close(htcpOutSocket);
        htcpOutSocket = -1;
    }
}