Merge branch 'ikev1-rekeying'

[thirdparty/strongswan.git] / src / libcharon / sa / ike_sa_manager.c

/*
 * Copyright (C) 2005-2011 Martin Willi
 * Copyright (C) 2011 revosec AG
 * Copyright (C) 2008-2012 Tobias Brunner
 * Copyright (C) 2005 Jan Hutter
 * Hochschule fuer Technik Rapperswil
 *
 * 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.  See <http://www.fsf.org/copyleft/gpl.txt>.
 *
 * 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.
 */

#include <string.h>

#include "ike_sa_manager.h"

#include <daemon.h>
#include <sa/ike_sa_id.h>
#include <bus/bus.h>
#include <threading/condvar.h>
#include <threading/mutex.h>
#include <threading/rwlock.h>
#include <collections/linked_list.h>
#include <crypto/hashers/hasher.h>

/* the default size of the hash table (MUST be a power of 2) */
#define DEFAULT_HASHTABLE_SIZE 1

/* the maximum size of the hash table (MUST be a power of 2) */
#define MAX_HASHTABLE_SIZE (1 << 30)

/* the default number of segments (MUST be a power of 2) */
#define DEFAULT_SEGMENT_COUNT 1

typedef struct entry_t entry_t;

/**
 * An entry in the linked list, contains IKE_SA, locking and lookup data.
 */
struct entry_t {

        /**
         * Number of threads waiting for this ike_sa_t object.
         */
        int waiting_threads;

        /**
         * Condvar where threads can wait until ike_sa_t object is free for use again.
         */
        condvar_t *condvar;

        /**
         * Is this ike_sa currently checked out?
         */
        bool checked_out;

        /**
         * Does this SA drives out new threads?
         */
        bool driveout_new_threads;

        /**
         * Does this SA drives out waiting threads?
         */
        bool driveout_waiting_threads;

        /**
         * Identification of an IKE_SA (SPIs).
         */
        ike_sa_id_t *ike_sa_id;

        /**
         * The contained ike_sa_t object.
         */
        ike_sa_t *ike_sa;

        /**
         * hash of the IKE_SA_INIT message, used to detect retransmissions
         */
        chunk_t init_hash;

        /**
         * remote host address, required for DoS detection and duplicate
         * checking (host with same my_id and other_id is *not* considered
         * a duplicate if the address family differs)
         */
        host_t *other;

        /**
         * As responder: Is this SA half-open?
         */
        bool half_open;

        /**
         * own identity, required for duplicate checking
         */
        identification_t *my_id;

        /**
         * remote identity, required for duplicate checking
         */
        identification_t *other_id;

        /**
         * message ID or hash of currently processing message, -1 if none
         */
        u_int32_t processing;
};

/**
 * Implementation of entry_t.destroy.
 */
static status_t entry_destroy(entry_t *this)
{
        /* also destroy IKE SA */
        this->ike_sa->destroy(this->ike_sa);
        this->ike_sa_id->destroy(this->ike_sa_id);
        chunk_free(&this->init_hash);
        DESTROY_IF(this->other);
        DESTROY_IF(this->my_id);
        DESTROY_IF(this->other_id);
        this->condvar->destroy(this->condvar);
        free(this);
        return SUCCESS;
}

/**
 * Creates a new entry for the ike_sa_t list.
 */
static entry_t *entry_create()
{
        entry_t *this;

        INIT(this,
                .condvar = condvar_create(CONDVAR_TYPE_DEFAULT),
                .processing = -1,
        );

        return this;
}

/**
 * Function that matches entry_t objects by ike_sa_id_t.
 */
static bool entry_match_by_id(entry_t *entry, ike_sa_id_t *id)
{
        if (id->equals(id, entry->ike_sa_id))
        {
                return TRUE;
        }
        if ((id->get_responder_spi(id) == 0 ||
                 entry->ike_sa_id->get_responder_spi(entry->ike_sa_id) == 0) &&
                id->get_initiator_spi(id) == entry->ike_sa_id->get_initiator_spi(entry->ike_sa_id))
        {
                /* this is TRUE for IKE_SAs that we initiated but have not yet received a response */
                return TRUE;
        }
        return FALSE;
}

/**
 * Function that matches entry_t objects by ike_sa_t pointers.
 */
static bool entry_match_by_sa(entry_t *entry, ike_sa_t *ike_sa)
{
        return entry->ike_sa == ike_sa;
}

/**
 * Hash function for ike_sa_id_t objects.
 */
static u_int ike_sa_id_hash(ike_sa_id_t *ike_sa_id)
{
        /* IKEv2 does not mandate random SPIs (RFC 5996, 2.6), they just have to be
         * locally unique, so we use our randomly allocated SPI whether we are
         * initiator or responder to ensure a good distribution.  The latter is not
         * possible for IKEv1 as we don't know whether we are original initiator or
         * not (based on the IKE header).  But as RFC 2408, section 2.5.3 proposes
         * SPIs (Cookies) to be allocated near random (we allocate them randomly
         * anyway) it seems safe to always use the initiator SPI. */
        if (ike_sa_id->get_ike_version(ike_sa_id) == IKEV1_MAJOR_VERSION ||
                ike_sa_id->is_initiator(ike_sa_id))
        {
                return ike_sa_id->get_initiator_spi(ike_sa_id);
        }
        return ike_sa_id->get_responder_spi(ike_sa_id);
}

typedef struct half_open_t half_open_t;

/**
 * Struct to manage half-open IKE_SAs per peer.
 */
struct half_open_t {
        /** chunk of remote host address */
        chunk_t other;

        /** the number of half-open IKE_SAs with that host */
        u_int count;
};

/**
 * Destroys a half_open_t object.
 */
static void half_open_destroy(half_open_t *this)
{
        chunk_free(&this->other);
        free(this);
}

typedef struct connected_peers_t connected_peers_t;

struct connected_peers_t {
        /** own identity */
        identification_t *my_id;

        /** remote identity */
        identification_t *other_id;

        /** ip address family of peer */
        int family;

        /** list of ike_sa_id_t objects of IKE_SAs between the two identities */
        linked_list_t *sas;
};

static void connected_peers_destroy(connected_peers_t *this)
{
        this->my_id->destroy(this->my_id);
        this->other_id->destroy(this->other_id);
        this->sas->destroy(this->sas);
        free(this);
}

/**
 * Function that matches connected_peers_t objects by the given ids.
 */
static inline bool connected_peers_match(connected_peers_t *connected_peers,
                                                        identification_t *my_id, identification_t *other_id,
                                                        int family)
{
        return my_id->equals(my_id, connected_peers->my_id) &&
                   other_id->equals(other_id, connected_peers->other_id) &&
                   (!family || family == connected_peers->family);
}

typedef struct init_hash_t init_hash_t;

struct init_hash_t {
        /** hash of IKE_SA_INIT or initial phase1 message (data is not cloned) */
        chunk_t hash;

        /** our SPI allocated for the IKE_SA based on this message */
        u_int64_t our_spi;
};

typedef struct segment_t segment_t;

/**
 * Struct to manage segments of the hash table.
 */
struct segment_t {
        /** mutex to access a segment exclusively */
        mutex_t *mutex;

        /** the number of entries in this segment */
        u_int count;
};

typedef struct shareable_segment_t shareable_segment_t;

/**
 * Struct to manage segments of the "half-open" and "connected peers" hash tables.
 */
struct shareable_segment_t {
        /** rwlock to access a segment non-/exclusively */
        rwlock_t *lock;

        /** the number of entries in this segment - in case of the "half-open table"
         * it's the sum of all half_open_t.count in a segment. */
        u_int count;
};

typedef struct table_item_t table_item_t;

/**
 * Instead of using linked_list_t for each bucket we store the data in our own
 * list to save memory.
 */
struct table_item_t {
        /** data of this item */
        void *value;

        /** next item in the overflow list */
        table_item_t *next;
};

typedef struct private_ike_sa_manager_t private_ike_sa_manager_t;

/**
 * Additional private members of ike_sa_manager_t.
 */
struct private_ike_sa_manager_t {
        /**
         * Public interface of ike_sa_manager_t.
         */
        ike_sa_manager_t public;

        /**
         * Hash table with entries for the ike_sa_t objects.
         */
        table_item_t **ike_sa_table;

        /**
         * The size of the hash table.
         */
        u_int table_size;

        /**
         * Mask to map the hashes to table rows.
         */
        u_int table_mask;

        /**
         * Segments of the hash table.
         */
        segment_t *segments;

        /**
         * The number of segments.
         */
        u_int segment_count;

        /**
         * Mask to map a table row to a segment.
         */
        u_int segment_mask;

        /**
         * Hash table with half_open_t objects.
         */
        table_item_t **half_open_table;

        /**
          * Segments of the "half-open" hash table.
         */
        shareable_segment_t *half_open_segments;

        /**
         * Hash table with connected_peers_t objects.
         */
        table_item_t **connected_peers_table;

        /**
         * Segments of the "connected peers" hash table.
         */
        shareable_segment_t *connected_peers_segments;

        /**
         * Hash table with init_hash_t objects.
         */
        table_item_t **init_hashes_table;

        /**
          * Segments of the "hashes" hash table.
         */
        segment_t *init_hashes_segments;

        /**
         * RNG to get random SPIs for our side
         */
        rng_t *rng;

        /**
         * SHA1 hasher for IKE_SA_INIT retransmit detection
         */
        hasher_t *hasher;

        /**
         * reuse existing IKE_SAs in checkout_by_config
         */
        bool reuse_ikesa;

        /**
         * Configured IKE_SA limit, if any
         */
        u_int ikesa_limit;
};

/**
 * Acquire a lock to access the segment of the table row with the given index.
 * It also works with the segment index directly.
 */
static inline void lock_single_segment(private_ike_sa_manager_t *this,
                                                                           u_int index)
{
        mutex_t *lock = this->segments[index & this->segment_mask].mutex;
        lock->lock(lock);
}

/**
 * Release the lock required to access the segment of the table row with the given index.
 * It also works with the segment index directly.
 */
static inline void unlock_single_segment(private_ike_sa_manager_t *this,
                                                                                 u_int index)
{
        mutex_t *lock = this->segments[index & this->segment_mask].mutex;
        lock->unlock(lock);
}

/**
 * Lock all segments
 */
static void lock_all_segments(private_ike_sa_manager_t *this)
{
        u_int i;

        for (i = 0; i < this->segment_count; i++)
        {
                this->segments[i].mutex->lock(this->segments[i].mutex);
        }
}

/**
 * Unlock all segments
 */
static void unlock_all_segments(private_ike_sa_manager_t *this)
{
        u_int i;

        for (i = 0; i < this->segment_count; i++)
        {
                this->segments[i].mutex->unlock(this->segments[i].mutex);
        }
}

typedef struct private_enumerator_t private_enumerator_t;

/**
 * hash table enumerator implementation
 */
struct private_enumerator_t {

        /**
         * implements enumerator interface
         */
        enumerator_t enumerator;

        /**
         * associated ike_sa_manager_t
         */
        private_ike_sa_manager_t *manager;

        /**
         * current segment index
         */
        u_int segment;

        /**
         * currently enumerating entry
         */
        entry_t *entry;

        /**
         * current table row index
         */
        u_int row;

        /**
         * current table item
         */
        table_item_t *current;

        /**
         * previous table item
         */
        table_item_t *prev;
};

METHOD(enumerator_t, enumerate, bool,
        private_enumerator_t *this, entry_t **entry, u_int *segment)
{
        if (this->entry)
        {
                this->entry->condvar->signal(this->entry->condvar);
                this->entry = NULL;
        }
        while (this->segment < this->manager->segment_count)
        {
                while (this->row < this->manager->table_size)
                {
                        this->prev = this->current;
                        if (this->current)
                        {
                                this->current = this->current->next;
                        }
                        else
                        {
                                lock_single_segment(this->manager, this->segment);
                                this->current = this->manager->ike_sa_table[this->row];
                        }
                        if (this->current)
                        {
                                *entry = this->entry = this->current->value;
                                *segment = this->segment;
                                return TRUE;
                        }
                        unlock_single_segment(this->manager, this->segment);
                        this->row += this->manager->segment_count;
                }
                this->segment++;
                this->row = this->segment;
        }
        return FALSE;
}

METHOD(enumerator_t, enumerator_destroy, void,
        private_enumerator_t *this)
{
        if (this->entry)
        {
                this->entry->condvar->signal(this->entry->condvar);
        }
        if (this->current)
        {
                unlock_single_segment(this->manager, this->segment);
        }
        free(this);
}

/**
 * Creates an enumerator to enumerate the entries in the hash table.
 */
static enumerator_t* create_table_enumerator(private_ike_sa_manager_t *this)
{
        private_enumerator_t *enumerator;

        INIT(enumerator,
                .enumerator = {
                        .enumerate = (void*)_enumerate,
                        .destroy = _enumerator_destroy,
                },
                .manager = this,
        );
        return &enumerator->enumerator;
}

/**
 * Put an entry into the hash table.
 * Note: The caller has to unlock the returned segment.
 */
static u_int put_entry(private_ike_sa_manager_t *this, entry_t *entry)
{
        table_item_t *current, *item;
        u_int row, segment;

        INIT(item,
                .value = entry,
        );

        row = ike_sa_id_hash(entry->ike_sa_id) & this->table_mask;
        segment = row & this->segment_mask;

        lock_single_segment(this, segment);
        current = this->ike_sa_table[row];
        if (current)
        {       /* insert at the front of current bucket */
                item->next = current;
        }
        this->ike_sa_table[row] = item;
        this->segments[segment].count++;
        return segment;
}

/**
 * Remove an entry from the hash table.
 * Note: The caller MUST have a lock on the segment of this entry.
 */
static void remove_entry(private_ike_sa_manager_t *this, entry_t *entry)
{
        table_item_t *item, *prev = NULL;
        u_int row, segment;

        row = ike_sa_id_hash(entry->ike_sa_id) & this->table_mask;
        segment = row & this->segment_mask;
        item = this->ike_sa_table[row];
        while (item)
        {
                if (item->value == entry)
                {
                        if (prev)
                        {
                                prev->next = item->next;
                        }
                        else
                        {
                                this->ike_sa_table[row] = item->next;
                        }
                        this->segments[segment].count--;
                        free(item);
                        break;
                }
                prev = item;
                item = item->next;
        }
}

/**
 * Remove the entry at the current enumerator position.
 */
static void remove_entry_at(private_enumerator_t *this)
{
        this->entry = NULL;
        if (this->current)
        {
                table_item_t *current = this->current;

                this->manager->segments[this->segment].count--;
                this->current = this->prev;

                if (this->prev)
                {
                        this->prev->next = current->next;
                }
                else
                {
                        this->manager->ike_sa_table[this->row] = current->next;
                        unlock_single_segment(this->manager, this->segment);
                }
                free(current);
        }
}

/**
 * Find an entry using the provided match function to compare the entries for
 * equality.
 */
static status_t get_entry_by_match_function(private_ike_sa_manager_t *this,
                                        ike_sa_id_t *ike_sa_id, entry_t **entry, u_int *segment,
                                        linked_list_match_t match, void *param)
{
        table_item_t *item;
        u_int row, seg;

        row = ike_sa_id_hash(ike_sa_id) & this->table_mask;
        seg = row & this->segment_mask;

        lock_single_segment(this, seg);
        item = this->ike_sa_table[row];
        while (item)
        {
                if (match(item->value, param))
                {
                        *entry = item->value;
                        *segment = seg;
                        /* the locked segment has to be unlocked by the caller */
                        return SUCCESS;
                }
                item = item->next;
        }
        unlock_single_segment(this, seg);
        return NOT_FOUND;
}

/**
 * Find an entry by ike_sa_id_t.
 * Note: On SUCCESS, the caller has to unlock the segment.
 */
static status_t get_entry_by_id(private_ike_sa_manager_t *this,
                                                ike_sa_id_t *ike_sa_id, entry_t **entry, u_int *segment)
{
        return get_entry_by_match_function(this, ike_sa_id, entry, segment,
                                (linked_list_match_t)entry_match_by_id, ike_sa_id);
}

/**
 * Find an entry by IKE_SA pointer.
 * Note: On SUCCESS, the caller has to unlock the segment.
 */
static status_t get_entry_by_sa(private_ike_sa_manager_t *this,
                        ike_sa_id_t *ike_sa_id, ike_sa_t *ike_sa, entry_t **entry, u_int *segment)
{
        return get_entry_by_match_function(this, ike_sa_id, entry, segment,
                                (linked_list_match_t)entry_match_by_sa, ike_sa);
}

/**
 * Wait until no other thread is using an IKE_SA, return FALSE if entry not
 * acquirable.
 */
static bool wait_for_entry(private_ike_sa_manager_t *this, entry_t *entry,
                                                   u_int segment)
{
        if (entry->driveout_new_threads)
        {
                /* we are not allowed to get this */
                return FALSE;
        }
        while (entry->checked_out && !entry->driveout_waiting_threads)
        {
                /* so wait until we can get it for us.
                 * we register us as waiting. */
                entry->waiting_threads++;
                entry->condvar->wait(entry->condvar, this->segments[segment].mutex);
                entry->waiting_threads--;
        }
        /* hm, a deletion request forbids us to get this SA, get next one */
        if (entry->driveout_waiting_threads)
        {
                /* we must signal here, others may be waiting on it, too */
                entry->condvar->signal(entry->condvar);
                return FALSE;
        }
        return TRUE;
}

/**
 * Put a half-open SA into the hash table.
 */
static void put_half_open(private_ike_sa_manager_t *this, entry_t *entry)
{
        table_item_t *item;
        u_int row, segment;
        rwlock_t *lock;
        half_open_t *half_open;
        chunk_t addr;

        addr = entry->other->get_address(entry->other);
        row = chunk_hash(addr) & this->table_mask;
        segment = row & this->segment_mask;
        lock = this->half_open_segments[segment].lock;
        lock->write_lock(lock);
        item = this->half_open_table[row];
        while (item)
        {
                half_open = item->value;

                if (chunk_equals(addr, half_open->other))
                {
                        half_open->count++;
                        break;
                }
                item = item->next;
        }

        if (!item)
        {
                INIT(half_open,
                        .other = chunk_clone(addr),
                        .count = 1,
                );
                INIT(item,
                        .value = half_open,
                        .next = this->half_open_table[row],
                );
                this->half_open_table[row] = item;
        }
        this->half_open_segments[segment].count++;
        lock->unlock(lock);
}

/**
 * Remove a half-open SA from the hash table.
 */
static void remove_half_open(private_ike_sa_manager_t *this, entry_t *entry)
{
        table_item_t *item, *prev = NULL;
        u_int row, segment;
        rwlock_t *lock;
        chunk_t addr;

        addr = entry->other->get_address(entry->other);
        row = chunk_hash(addr) & this->table_mask;
        segment = row & this->segment_mask;
        lock = this->half_open_segments[segment].lock;
        lock->write_lock(lock);
        item = this->half_open_table[row];
        while (item)
        {
                half_open_t *half_open = item->value;

                if (chunk_equals(addr, half_open->other))
                {
                        if (--half_open->count == 0)
                        {
                                if (prev)
                                {
                                        prev->next = item->next;
                                }
                                else
                                {
                                        this->half_open_table[row] = item->next;
                                }
                                half_open_destroy(half_open);
                                free(item);
                        }
                        this->half_open_segments[segment].count--;
                        break;
                }
                prev = item;
                item = item->next;
        }
        lock->unlock(lock);
}

/**
 * Put an SA between two peers into the hash table.
 */
static void put_connected_peers(private_ike_sa_manager_t *this, entry_t *entry)
{
        table_item_t *item;
        u_int row, segment;
        rwlock_t *lock;
        connected_peers_t *connected_peers;
        chunk_t my_id, other_id;
        int family;

        my_id = entry->my_id->get_encoding(entry->my_id);
        other_id = entry->other_id->get_encoding(entry->other_id);
        family = entry->other->get_family(entry->other);
        row = chunk_hash_inc(other_id, chunk_hash(my_id)) & this->table_mask;
        segment = row & this->segment_mask;
        lock = this->connected_peers_segments[segment].lock;
        lock->write_lock(lock);
        item = this->connected_peers_table[row];
        while (item)
        {
                connected_peers = item->value;

                if (connected_peers_match(connected_peers, entry->my_id,
                                                                  entry->other_id, family))
                {
                        if (connected_peers->sas->find_first(connected_peers->sas,
                                        (linked_list_match_t)entry->ike_sa_id->equals,
                                        NULL, entry->ike_sa_id) == SUCCESS)
                        {
                                lock->unlock(lock);
                                return;
                        }
                        break;
                }
                item = item->next;
        }

        if (!item)
        {
                INIT(connected_peers,
                        .my_id = entry->my_id->clone(entry->my_id),
                        .other_id = entry->other_id->clone(entry->other_id),
                        .family = family,
                        .sas = linked_list_create(),
                );
                INIT(item,
                        .value = connected_peers,
                        .next = this->connected_peers_table[row],
                );
                this->connected_peers_table[row] = item;
        }
        connected_peers->sas->insert_last(connected_peers->sas,
                                                                          entry->ike_sa_id->clone(entry->ike_sa_id));
        this->connected_peers_segments[segment].count++;
        lock->unlock(lock);
}

/**
 * Remove an SA between two peers from the hash table.
 */
static void remove_connected_peers(private_ike_sa_manager_t *this, entry_t *entry)
{
        table_item_t *item, *prev = NULL;
        u_int row, segment;
        rwlock_t *lock;
        chunk_t my_id, other_id;
        int family;

        my_id = entry->my_id->get_encoding(entry->my_id);
        other_id = entry->other_id->get_encoding(entry->other_id);
        family = entry->other->get_family(entry->other);

        row = chunk_hash_inc(other_id, chunk_hash(my_id)) & this->table_mask;
        segment = row & this->segment_mask;

        lock = this->connected_peers_segments[segment].lock;
        lock->write_lock(lock);
        item = this->connected_peers_table[row];
        while (item)
        {
                connected_peers_t *current = item->value;

                if (connected_peers_match(current, entry->my_id, entry->other_id,
                                                                  family))
                {
                        enumerator_t *enumerator;
                        ike_sa_id_t *ike_sa_id;

                        enumerator = current->sas->create_enumerator(current->sas);
                        while (enumerator->enumerate(enumerator, &ike_sa_id))
                        {
                                if (ike_sa_id->equals(ike_sa_id, entry->ike_sa_id))
                                {
                                        current->sas->remove_at(current->sas, enumerator);
                                        ike_sa_id->destroy(ike_sa_id);
                                        this->connected_peers_segments[segment].count--;
                                        break;
                                }
                        }
                        enumerator->destroy(enumerator);
                        if (current->sas->get_count(current->sas) == 0)
                        {
                                if (prev)
                                {
                                        prev->next = item->next;
                                }
                                else
                                {
                                        this->connected_peers_table[row] = item->next;
                                }
                                connected_peers_destroy(current);
                                free(item);
                        }
                        break;
                }
                prev = item;
                item = item->next;
        }
        lock->unlock(lock);
}

/**
 * Get a random SPI for new IKE_SAs
 */
static u_int64_t get_spi(private_ike_sa_manager_t *this)
{
        u_int64_t spi;

        if (this->rng &&
                this->rng->get_bytes(this->rng, sizeof(spi), (u_int8_t*)&spi))
        {
                return spi;
        }
        return 0;
}

/**
 * Calculate the hash of the initial IKE message.  Memory for the hash is
 * allocated on success.
 *
 * @returns TRUE on success
 */
static bool get_init_hash(private_ike_sa_manager_t *this, message_t *message,
                                                  chunk_t *hash)
{
        host_t *src;

        if (!this->hasher)
        {       /* this might be the case when flush() has been called */
                return FALSE;
        }
        if (message->get_first_payload_type(message) == FRAGMENT_V1)
        {       /* only hash the source IP, port and SPI for fragmented init messages */
                u_int16_t port;
                u_int64_t spi;

                src = message->get_source(message);
                if (!this->hasher->allocate_hash(this->hasher,
                                                                                 src->get_address(src), NULL))
                {
                        return FALSE;
                }
                port = src->get_port(src);
                if (!this->hasher->allocate_hash(this->hasher,
                                                                                 chunk_from_thing(port), NULL))
                {
                        return FALSE;
                }
                spi = message->get_initiator_spi(message);
                return this->hasher->allocate_hash(this->hasher,
                                                                                   chunk_from_thing(spi), hash);
        }
        if (message->get_exchange_type(message) == ID_PROT)
        {       /* include the source for Main Mode as the hash will be the same if
                 * SPIs are reused by two initiators that use the same proposal */
                src = message->get_source(message);

                if (!this->hasher->allocate_hash(this->hasher,
                                                                                 src->get_address(src), NULL))
                {
                        return FALSE;
                }
        }
        return this->hasher->allocate_hash(this->hasher,
                                                                           message->get_packet_data(message), hash);
}

/**
 * Check if we already have created an IKE_SA based on the initial IKE message
 * with the given hash.
 * If not the hash is stored, the hash data is not(!) cloned.
 *
 * Also, the local SPI is returned.  In case of a retransmit this is already
 * stored together with the hash, otherwise it is newly allocated and should
 * be used to create the IKE_SA.
 *
 * @returns ALREADY_DONE if the message with the given hash has been seen before
 *                      NOT_FOUND if the message hash was not found
 *                      FAILED if the SPI allocation failed
 */
static status_t check_and_put_init_hash(private_ike_sa_manager_t *this,
                                                                                chunk_t init_hash, u_int64_t *our_spi)
{
        table_item_t *item;
        u_int row, segment;
        mutex_t *mutex;
        init_hash_t *init;
        u_int64_t spi;

        row = chunk_hash(init_hash) & this->table_mask;
        segment = row & this->segment_mask;
        mutex = this->init_hashes_segments[segment].mutex;
        mutex->lock(mutex);
        item = this->init_hashes_table[row];
        while (item)
        {
                init_hash_t *current = item->value;

                if (chunk_equals(init_hash, current->hash))
                {
                        *our_spi = current->our_spi;
                        mutex->unlock(mutex);
                        return ALREADY_DONE;
                }
                item = item->next;
        }

        spi = get_spi(this);
        if (!spi)
        {
                return FAILED;
        }

        INIT(init,
                .hash = {
                        .len = init_hash.len,
                        .ptr = init_hash.ptr,
                },
                .our_spi = spi,
        );
        INIT(item,
                .value = init,
                .next = this->init_hashes_table[row],
        );
        this->init_hashes_table[row] = item;
        *our_spi = init->our_spi;
        mutex->unlock(mutex);
        return NOT_FOUND;
}

/**
 * Remove the hash of an initial IKE message from the cache.
 */
static void remove_init_hash(private_ike_sa_manager_t *this, chunk_t init_hash)
{
        table_item_t *item, *prev = NULL;
        u_int row, segment;
        mutex_t *mutex;

        row = chunk_hash(init_hash) & this->table_mask;
        segment = row & this->segment_mask;
        mutex = this->init_hashes_segments[segment].mutex;
        mutex->lock(mutex);
        item = this->init_hashes_table[row];
        while (item)
        {
                init_hash_t *current = item->value;

                if (chunk_equals(init_hash, current->hash))
                {
                        if (prev)
                        {
                                prev->next = item->next;
                        }
                        else
                        {
                                this->init_hashes_table[row] = item->next;
                        }
                        free(current);
                        free(item);
                        break;
                }
                prev = item;
                item = item->next;
        }
        mutex->unlock(mutex);
}

METHOD(ike_sa_manager_t, checkout, ike_sa_t*,
        private_ike_sa_manager_t *this, ike_sa_id_t *ike_sa_id)
{
        ike_sa_t *ike_sa = NULL;
        entry_t *entry;
        u_int segment;

        DBG2(DBG_MGR, "checkout IKE_SA");

        if (get_entry_by_id(this, ike_sa_id, &entry, &segment) == SUCCESS)
        {
                if (wait_for_entry(this, entry, segment))
                {
                        entry->checked_out = TRUE;
                        ike_sa = entry->ike_sa;
                        DBG2(DBG_MGR, "IKE_SA %s[%u] successfully checked out",
                                        ike_sa->get_name(ike_sa), ike_sa->get_unique_id(ike_sa));
                }
                unlock_single_segment(this, segment);
        }
        charon->bus->set_sa(charon->bus, ike_sa);
        return ike_sa;
}

METHOD(ike_sa_manager_t, checkout_new, ike_sa_t*,
        private_ike_sa_manager_t* this, ike_version_t version, bool initiator)
{
        ike_sa_id_t *ike_sa_id;
        ike_sa_t *ike_sa;
        u_int8_t ike_version;
        u_int64_t spi;

        ike_version = version == IKEV1 ? IKEV1_MAJOR_VERSION : IKEV2_MAJOR_VERSION;

        spi = get_spi(this);
        if (!spi)
        {
                DBG1(DBG_MGR, "failed to allocate SPI for new IKE_SA");
                return NULL;
        }

        if (initiator)
        {
                ike_sa_id = ike_sa_id_create(ike_version, spi, 0, TRUE);
        }
        else
        {
                ike_sa_id = ike_sa_id_create(ike_version, 0, spi, FALSE);
        }
        ike_sa = ike_sa_create(ike_sa_id, initiator, version);
        ike_sa_id->destroy(ike_sa_id);

        if (ike_sa)
        {
                DBG2(DBG_MGR, "created IKE_SA %s[%u]", ike_sa->get_name(ike_sa),
                         ike_sa->get_unique_id(ike_sa));
        }
        return ike_sa;
}

/**
 * Get the message ID or message hash to detect early retransmissions
 */
static u_int32_t get_message_id_or_hash(message_t *message)
{
        /* Use the message ID, or the message hash in IKEv1 Main/Aggressive mode */
        if (message->get_major_version(message) == IKEV1_MAJOR_VERSION &&
                message->get_message_id(message) == 0)
        {
                return chunk_hash(message->get_packet_data(message));
        }
        return message->get_message_id(message);
}

METHOD(ike_sa_manager_t, checkout_by_message, ike_sa_t*,
        private_ike_sa_manager_t* this, message_t *message)
{
        u_int segment;
        entry_t *entry;
        ike_sa_t *ike_sa = NULL;
        ike_sa_id_t *id;
        ike_version_t ike_version;
        bool is_init = FALSE;

        id = message->get_ike_sa_id(message);
        /* clone the IKE_SA ID so we can modify the initiator flag */
        id = id->clone(id);
        id->switch_initiator(id);

        DBG2(DBG_MGR, "checkout IKE_SA by message");

        if (id->get_responder_spi(id) == 0)
        {
                if (message->get_major_version(message) == IKEV2_MAJOR_VERSION)
                {
                        if (message->get_exchange_type(message) == IKE_SA_INIT &&
                                message->get_request(message))
                        {
                                ike_version = IKEV2;
                                is_init = TRUE;
                        }
                }
                else
                {
                        if (message->get_exchange_type(message) == ID_PROT ||
                                message->get_exchange_type(message) == AGGRESSIVE)
                        {
                                ike_version = IKEV1;
                                is_init = TRUE;
                                if (id->is_initiator(id))
                                {       /* not set in IKEv1, switch back before applying to new SA */
                                        id->switch_initiator(id);
                                }
                        }
                }
        }

        if (is_init)
        {
                u_int64_t our_spi;
                chunk_t hash;

                if (!get_init_hash(this, message, &hash))
                {
                        DBG1(DBG_MGR, "ignoring message, failed to hash message");
                        id->destroy(id);
                        return NULL;
                }

                /* ensure this is not a retransmit of an already handled init message */
                switch (check_and_put_init_hash(this, hash, &our_spi))
                {
                        case NOT_FOUND:
                        {       /* we've not seen this packet yet, create a new IKE_SA */
                                if (!this->ikesa_limit ||
                                        this->public.get_count(&this->public) < this->ikesa_limit)
                                {
                                        id->set_responder_spi(id, our_spi);
                                        ike_sa = ike_sa_create(id, FALSE, ike_version);
                                        if (ike_sa)
                                        {
                                                entry = entry_create();
                                                entry->ike_sa = ike_sa;
                                                entry->ike_sa_id = id;

                                                segment = put_entry(this, entry);
                                                entry->checked_out = TRUE;
                                                unlock_single_segment(this, segment);

                                                entry->processing = get_message_id_or_hash(message);
                                                entry->init_hash = hash;

                                                DBG2(DBG_MGR, "created IKE_SA %s[%u]",
                                                         ike_sa->get_name(ike_sa),
                                                         ike_sa->get_unique_id(ike_sa));

                                                charon->bus->set_sa(charon->bus, ike_sa);
                                                return ike_sa;
                                        }
                                        else
                                        {
                                                DBG1(DBG_MGR, "creating IKE_SA failed, ignoring message");
                                        }
                                }
                                else
                                {
                                        DBG1(DBG_MGR, "ignoring %N, hitting IKE_SA limit (%u)",
                                                 exchange_type_names, message->get_exchange_type(message),
                                                 this->ikesa_limit);
                                }
                                remove_init_hash(this, hash);
                                chunk_free(&hash);
                                id->destroy(id);
                                return NULL;
                        }
                        case FAILED:
                        {       /* we failed to allocate an SPI */
                                chunk_free(&hash);
                                id->destroy(id);
                                DBG1(DBG_MGR, "ignoring message, failed to allocate SPI");
                                return NULL;
                        }
                        case ALREADY_DONE:
                        default:
                                break;
                }
                /* it looks like we already handled this init message to some degree */
                id->set_responder_spi(id, our_spi);
                chunk_free(&hash);
        }

        if (get_entry_by_id(this, id, &entry, &segment) == SUCCESS)
        {
                /* only check out if we are not already processing it. */
                if (entry->processing == get_message_id_or_hash(message))
                {
                        DBG1(DBG_MGR, "ignoring request with ID %u, already processing",
                                 entry->processing);
                }
                else if (wait_for_entry(this, entry, segment))
                {
                        ike_sa_id_t *ike_id;

                        ike_id = entry->ike_sa->get_id(entry->ike_sa);
                        entry->checked_out = TRUE;
                        if (message->get_first_payload_type(message) != FRAGMENT_V1)
                        {
                                entry->processing = get_message_id_or_hash(message);
                        }
                        if (ike_id->get_responder_spi(ike_id) == 0)
                        {
                                ike_id->set_responder_spi(ike_id, id->get_responder_spi(id));
                        }
                        ike_sa = entry->ike_sa;
                        DBG2(DBG_MGR, "IKE_SA %s[%u] successfully checked out",
                                        ike_sa->get_name(ike_sa), ike_sa->get_unique_id(ike_sa));
                }
                unlock_single_segment(this, segment);
        }
        else
        {
                charon->bus->alert(charon->bus, ALERT_INVALID_IKE_SPI, message);
        }
        id->destroy(id);
        charon->bus->set_sa(charon->bus, ike_sa);
        return ike_sa;
}

METHOD(ike_sa_manager_t, checkout_by_config, ike_sa_t*,
        private_ike_sa_manager_t *this, peer_cfg_t *peer_cfg)
{
        enumerator_t *enumerator;
        entry_t *entry;
        ike_sa_t *ike_sa = NULL;
        peer_cfg_t *current_peer;
        ike_cfg_t *current_ike;
        u_int segment;

        DBG2(DBG_MGR, "checkout IKE_SA by config");

        if (!this->reuse_ikesa)
        {       /* IKE_SA reuse disable by config */
                ike_sa = checkout_new(this, peer_cfg->get_ike_version(peer_cfg), TRUE);
                charon->bus->set_sa(charon->bus, ike_sa);
                return ike_sa;
        }

        enumerator = create_table_enumerator(this);
        while (enumerator->enumerate(enumerator, &entry, &segment))
        {
                if (!wait_for_entry(this, entry, segment))
                {
                        continue;
                }
                if (entry->ike_sa->get_state(entry->ike_sa) == IKE_DELETING)
                {       /* skip IKE_SAs which are not usable */
                        continue;
                }

                current_peer = entry->ike_sa->get_peer_cfg(entry->ike_sa);
                if (current_peer && current_peer->equals(current_peer, peer_cfg))
                {
                        current_ike = current_peer->get_ike_cfg(current_peer);
                        if (current_ike->equals(current_ike, peer_cfg->get_ike_cfg(peer_cfg)))
                        {
                                entry->checked_out = TRUE;
                                ike_sa = entry->ike_sa;
                                DBG2(DBG_MGR, "found existing IKE_SA %u with a '%s' config",
                                                ike_sa->get_unique_id(ike_sa),
                                                current_peer->get_name(current_peer));
                                break;
                        }
                }
        }
        enumerator->destroy(enumerator);

        if (!ike_sa)
        {       /* no IKE_SA using such a config, hand out a new */
                ike_sa = checkout_new(this, peer_cfg->get_ike_version(peer_cfg), TRUE);
        }
        charon->bus->set_sa(charon->bus, ike_sa);
        return ike_sa;
}

METHOD(ike_sa_manager_t, checkout_by_id, ike_sa_t*,
        private_ike_sa_manager_t *this, u_int32_t id, bool child)
{
        enumerator_t *enumerator, *children;
        entry_t *entry;
        ike_sa_t *ike_sa = NULL;
        child_sa_t *child_sa;
        u_int segment;

        DBG2(DBG_MGR, "checkout IKE_SA by ID");

        enumerator = create_table_enumerator(this);
        while (enumerator->enumerate(enumerator, &entry, &segment))
        {
                if (wait_for_entry(this, entry, segment))
                {
                        /* look for a child with such a reqid ... */
                        if (child)
                        {
                                children = entry->ike_sa->create_child_sa_enumerator(entry->ike_sa);
                                while (children->enumerate(children, (void**)&child_sa))
                                {
                                        if (child_sa->get_reqid(child_sa) == id)
                                        {
                                                ike_sa = entry->ike_sa;
                                                break;
                                        }
                                }
                                children->destroy(children);
                        }
                        else /* ... or for a IKE_SA with such a unique id */
                        {
                                if (entry->ike_sa->get_unique_id(entry->ike_sa) == id)
                                {
                                        ike_sa = entry->ike_sa;
                                }
                        }
                        /* got one, return */
                        if (ike_sa)
                        {
                                entry->checked_out = TRUE;
                                DBG2(DBG_MGR, "IKE_SA %s[%u] successfully checked out",
                                                ike_sa->get_name(ike_sa), ike_sa->get_unique_id(ike_sa));
                                break;
                        }
                }
        }
        enumerator->destroy(enumerator);

        charon->bus->set_sa(charon->bus, ike_sa);
        return ike_sa;
}

METHOD(ike_sa_manager_t, checkout_by_name, ike_sa_t*,
        private_ike_sa_manager_t *this, char *name, bool child)
{
        enumerator_t *enumerator, *children;
        entry_t *entry;
        ike_sa_t *ike_sa = NULL;
        child_sa_t *child_sa;
        u_int segment;

        enumerator = create_table_enumerator(this);
        while (enumerator->enumerate(enumerator, &entry, &segment))
        {
                if (wait_for_entry(this, entry, segment))
                {
                        /* look for a child with such a policy name ... */
                        if (child)
                        {
                                children = entry->ike_sa->create_child_sa_enumerator(entry->ike_sa);
                                while (children->enumerate(children, (void**)&child_sa))
                                {
                                        if (streq(child_sa->get_name(child_sa), name))
                                        {
                                                ike_sa = entry->ike_sa;
                                                break;
                                        }
                                }
                                children->destroy(children);
                        }
                        else /* ... or for a IKE_SA with such a connection name */
                        {
                                if (streq(entry->ike_sa->get_name(entry->ike_sa), name))
                                {
                                        ike_sa = entry->ike_sa;
                                }
                        }
                        /* got one, return */
                        if (ike_sa)
                        {
                                entry->checked_out = TRUE;
                                DBG2(DBG_MGR, "IKE_SA %s[%u] successfully checked out",
                                                ike_sa->get_name(ike_sa), ike_sa->get_unique_id(ike_sa));
                                break;
                        }
                }
        }
        enumerator->destroy(enumerator);

        charon->bus->set_sa(charon->bus, ike_sa);
        return ike_sa;
}

/**
 * enumerator filter function, waiting variant
 */
static bool enumerator_filter_wait(private_ike_sa_manager_t *this,
                                                                   entry_t **in, ike_sa_t **out, u_int *segment)
{
        if (wait_for_entry(this, *in, *segment))
        {
                *out = (*in)->ike_sa;
                charon->bus->set_sa(charon->bus, *out);
                return TRUE;
        }
        return FALSE;
}

/**
 * enumerator filter function, skipping variant
 */
static bool enumerator_filter_skip(private_ike_sa_manager_t *this,
                                                                   entry_t **in, ike_sa_t **out, u_int *segment)
{
        if (!(*in)->driveout_new_threads &&
                !(*in)->driveout_waiting_threads &&
                !(*in)->checked_out)
        {
                *out = (*in)->ike_sa;
                charon->bus->set_sa(charon->bus, *out);
                return TRUE;
        }
        return FALSE;
}

/**
 * Reset threads SA after enumeration
 */
static void reset_sa(void *data)
{
        charon->bus->set_sa(charon->bus, NULL);
}

METHOD(ike_sa_manager_t, create_enumerator, enumerator_t*,
        private_ike_sa_manager_t* this, bool wait)
{
        return enumerator_create_filter(create_table_enumerator(this),
                        wait ? (void*)enumerator_filter_wait : (void*)enumerator_filter_skip,
                        this, reset_sa);
}

METHOD(ike_sa_manager_t, checkin, void,
        private_ike_sa_manager_t *this, ike_sa_t *ike_sa)
{
        /* to check the SA back in, we look for the pointer of the ike_sa
         * in all entries.
         * The lookup is done by initiator SPI, so even if the SPI has changed (e.g.
         * on reception of a IKE_SA_INIT response) the lookup will work but
         * updating of the SPI MAY be necessary...
         */
        entry_t *entry;
        ike_sa_id_t *ike_sa_id;
        host_t *other;
        identification_t *my_id, *other_id;
        u_int segment;

        ike_sa_id = ike_sa->get_id(ike_sa);
        my_id = ike_sa->get_my_id(ike_sa);
        other_id = ike_sa->get_other_eap_id(ike_sa);
        other = ike_sa->get_other_host(ike_sa);

        DBG2(DBG_MGR, "checkin IKE_SA %s[%u]", ike_sa->get_name(ike_sa),
                        ike_sa->get_unique_id(ike_sa));

        /* look for the entry */
        if (get_entry_by_sa(this, ike_sa_id, ike_sa, &entry, &segment) == SUCCESS)
        {
                /* ike_sa_id must be updated */
                entry->ike_sa_id->replace_values(entry->ike_sa_id, ike_sa->get_id(ike_sa));
                /* signal waiting threads */
                entry->checked_out = FALSE;
                entry->processing = -1;
                /* check if this SA is half-open */
                if (entry->half_open && ike_sa->get_state(ike_sa) != IKE_CONNECTING)
                {
                        /* not half open anymore */
                        entry->half_open = FALSE;
                        remove_half_open(this, entry);
                }
                else if (entry->half_open && !other->ip_equals(other, entry->other))
                {
                        /* the other host's IP has changed, we must update the hash table */
                        remove_half_open(this, entry);
                        DESTROY_IF(entry->other);
                        entry->other = other->clone(other);
                        put_half_open(this, entry);
                }
                else if (!entry->half_open &&
                                 !entry->ike_sa_id->is_initiator(entry->ike_sa_id) &&
                                 ike_sa->get_state(ike_sa) == IKE_CONNECTING)
                {
                        /* this is a new half-open SA */
                        entry->half_open = TRUE;
                        entry->other = other->clone(other);
                        put_half_open(this, entry);
                }
                DBG2(DBG_MGR, "check-in of IKE_SA successful.");
                entry->condvar->signal(entry->condvar);
        }
        else
        {
                entry = entry_create();
                entry->ike_sa_id = ike_sa_id->clone(ike_sa_id);
                entry->ike_sa = ike_sa;
                segment = put_entry(this, entry);
        }

        /* apply identities for duplicate test */
        if ((ike_sa->get_state(ike_sa) == IKE_ESTABLISHED ||
                 ike_sa->get_state(ike_sa) == IKE_PASSIVE) &&
                entry->my_id == NULL && entry->other_id == NULL)
        {
                if (ike_sa->get_version(ike_sa) == IKEV1)
                {
                        /* If authenticated and received INITIAL_CONTACT,
                         * delete any existing IKE_SAs with that peer. */
                        if (ike_sa->has_condition(ike_sa, COND_INIT_CONTACT_SEEN))
                        {
                                this->public.check_uniqueness(&this->public, ike_sa, TRUE);
                                ike_sa->set_condition(ike_sa, COND_INIT_CONTACT_SEEN, FALSE);
                        }
                }

                entry->my_id = my_id->clone(my_id);
                entry->other_id = other_id->clone(other_id);
                if (!entry->other)
                {
                        entry->other = other->clone(other);
                }
                put_connected_peers(this, entry);
        }

        unlock_single_segment(this, segment);

        charon->bus->set_sa(charon->bus, NULL);
}

METHOD(ike_sa_manager_t, checkin_and_destroy, void,
        private_ike_sa_manager_t *this, ike_sa_t *ike_sa)
{
        /* deletion is a bit complex, we must ensure that no thread is waiting for
         * this SA.
         * We take this SA from the table, and start signaling while threads
         * are in the condvar.
         */
        entry_t *entry;
        ike_sa_id_t *ike_sa_id;
        u_int segment;

        ike_sa_id = ike_sa->get_id(ike_sa);

        DBG2(DBG_MGR, "checkin and destroy IKE_SA %s[%u]", ike_sa->get_name(ike_sa),
                        ike_sa->get_unique_id(ike_sa));

        if (get_entry_by_sa(this, ike_sa_id, ike_sa, &entry, &segment) == SUCCESS)
        {
                if (entry->driveout_waiting_threads && entry->driveout_new_threads)
                {       /* it looks like flush() has been called and the SA is being deleted
                         * anyway, just check it in */
                        DBG2(DBG_MGR, "ignored check-in and destroy of IKE_SA during shutdown");
                        entry->checked_out = FALSE;
                        entry->condvar->broadcast(entry->condvar);
                        unlock_single_segment(this, segment);
                        return;
                }

                /* drive out waiting threads, as we are in hurry */
                entry->driveout_waiting_threads = TRUE;
                /* mark it, so no new threads can get this entry */
                entry->driveout_new_threads = TRUE;
                /* wait until all workers have done their work */
                while (entry->waiting_threads)
                {
                        /* wake up all */
                        entry->condvar->broadcast(entry->condvar);
                        /* they will wake us again when their work is done */
                        entry->condvar->wait(entry->condvar, this->segments[segment].mutex);
                }
                remove_entry(this, entry);
                unlock_single_segment(this, segment);

                if (entry->half_open)
                {
                        remove_half_open(this, entry);
                }
                if (entry->my_id && entry->other_id)
                {
                        remove_connected_peers(this, entry);
                }
                if (entry->init_hash.ptr)
                {
                        remove_init_hash(this, entry->init_hash);
                }

                entry_destroy(entry);

                DBG2(DBG_MGR, "check-in and destroy of IKE_SA successful");
        }
        else
        {
                DBG1(DBG_MGR, "tried to check-in and delete nonexisting IKE_SA");
                ike_sa->destroy(ike_sa);
        }
        charon->bus->set_sa(charon->bus, NULL);
}

/**
 * Cleanup function for create_id_enumerator
 */
static void id_enumerator_cleanup(linked_list_t *ids)
{
        ids->destroy_offset(ids, offsetof(ike_sa_id_t, destroy));
}

METHOD(ike_sa_manager_t, create_id_enumerator, enumerator_t*,
        private_ike_sa_manager_t *this, identification_t *me,
        identification_t *other, int family)
{
        table_item_t *item;
        u_int row, segment;
        rwlock_t *lock;
        linked_list_t *ids = NULL;

        row = chunk_hash_inc(other->get_encoding(other),
                                                 chunk_hash(me->get_encoding(me))) & this->table_mask;
        segment = row & this->segment_mask;

        lock = this->connected_peers_segments[segment].lock;
        lock->read_lock(lock);
        item = this->connected_peers_table[row];
        while (item)
        {
                connected_peers_t *current = item->value;

                if (connected_peers_match(current, me, other, family))
                {
                        ids = current->sas->clone_offset(current->sas,
                                                                                         offsetof(ike_sa_id_t, clone));
                        break;
                }
                item = item->next;
        }
        lock->unlock(lock);

        if (!ids)
        {
                return enumerator_create_empty();
        }
        return enumerator_create_cleaner(ids->create_enumerator(ids),
                                                                         (void*)id_enumerator_cleanup, ids);
}

/**
 * Move all CHILD_SAs from old to new
 */
static void adopt_children(ike_sa_t *old, ike_sa_t *new)
{
        enumerator_t *enumerator;
        child_sa_t *child_sa;

        enumerator = old->create_child_sa_enumerator(old);
        while (enumerator->enumerate(enumerator, &child_sa))
        {
                old->remove_child_sa(old, enumerator);
                new->add_child_sa(new, child_sa);
        }
        enumerator->destroy(enumerator);
}

METHOD(ike_sa_manager_t, check_uniqueness, bool,
        private_ike_sa_manager_t *this, ike_sa_t *ike_sa, bool force_replace)
{
        bool cancel = FALSE;
        peer_cfg_t *peer_cfg;
        unique_policy_t policy;
        enumerator_t *enumerator;
        ike_sa_id_t *id = NULL;
        identification_t *me, *other;
        host_t *other_host;

        peer_cfg = ike_sa->get_peer_cfg(ike_sa);
        policy = peer_cfg->get_unique_policy(peer_cfg);
        if (policy == UNIQUE_NEVER || (policy == UNIQUE_NO && !force_replace))
        {
                return FALSE;
        }
        me = ike_sa->get_my_id(ike_sa);
        other = ike_sa->get_other_eap_id(ike_sa);
        other_host = ike_sa->get_other_host(ike_sa);

        enumerator = create_id_enumerator(this, me, other,
                                                                          other_host->get_family(other_host));
        while (enumerator->enumerate(enumerator, &id))
        {
                status_t status = SUCCESS;
                ike_sa_t *duplicate;

                duplicate = checkout(this, id);
                if (!duplicate)
                {
                        continue;
                }
                if (force_replace)
                {
                        DBG1(DBG_IKE, "destroying duplicate IKE_SA for peer '%Y', "
                                 "received INITIAL_CONTACT", other);
                        charon->bus->ike_updown(charon->bus, duplicate, FALSE);
                        checkin_and_destroy(this, duplicate);
                        continue;
                }
                peer_cfg = duplicate->get_peer_cfg(duplicate);
                if (peer_cfg && peer_cfg->equals(peer_cfg, ike_sa->get_peer_cfg(ike_sa)))
                {
                        switch (duplicate->get_state(duplicate))
                        {
                                case IKE_ESTABLISHED:
                                case IKE_REKEYING:
                                        switch (policy)
                                        {
                                                case UNIQUE_REPLACE:
                                                        charon->bus->alert(charon->bus, ALERT_UNIQUE_REPLACE);
                                                        if (duplicate->get_version(duplicate) == IKEV1)
                                                        {
                                                                adopt_children(duplicate, ike_sa);
                                                        }
                                                        DBG1(DBG_IKE, "deleting duplicate IKE_SA for peer "
                                                                        "'%Y' due to uniqueness policy", other);
                                                        status = duplicate->delete(duplicate);
                                                        break;
                                                case UNIQUE_KEEP:
                                                        cancel = TRUE;
                                                        /* we keep the first IKE_SA and delete all
                                                         * other duplicates that might exist */
                                                        policy = UNIQUE_REPLACE;
                                                        break;
                                                default:
                                                        break;
                                        }
                                        break;
                                default:
                                        break;
                        }
                }
                if (status == DESTROY_ME)
                {
                        checkin_and_destroy(this, duplicate);
                }
                else
                {
                        checkin(this, duplicate);
                }
        }
        enumerator->destroy(enumerator);
        /* reset thread's current IKE_SA after checkin */
        charon->bus->set_sa(charon->bus, ike_sa);
        return cancel;
}

METHOD(ike_sa_manager_t, has_contact, bool,
        private_ike_sa_manager_t *this, identification_t *me,
        identification_t *other, int family)
{
        table_item_t *item;
        u_int row, segment;
        rwlock_t *lock;
        bool found = FALSE;

        row = chunk_hash_inc(other->get_encoding(other),
                                                 chunk_hash(me->get_encoding(me))) & this->table_mask;
        segment = row & this->segment_mask;
        lock = this->connected_peers_segments[segment].lock;
        lock->read_lock(lock);
        item = this->connected_peers_table[row];
        while (item)
        {
                if (connected_peers_match(item->value, me, other, family))
                {
                        found = TRUE;
                        break;
                }
                item = item->next;
        }
        lock->unlock(lock);

        return found;
}

METHOD(ike_sa_manager_t, get_count, u_int,
        private_ike_sa_manager_t *this)
{
        u_int segment, count = 0;
        mutex_t *mutex;

        for (segment = 0; segment < this->segment_count; segment++)
        {
                mutex = this->segments[segment & this->segment_mask].mutex;
                mutex->lock(mutex);
                count += this->segments[segment].count;
                mutex->unlock(mutex);
        }
        return count;
}

METHOD(ike_sa_manager_t, get_half_open_count, u_int,
        private_ike_sa_manager_t *this, host_t *ip)
{
        table_item_t *item;
        u_int row, segment;
        rwlock_t *lock;
        chunk_t addr;
        u_int count = 0;

        if (ip)
        {
                addr = ip->get_address(ip);
                row = chunk_hash(addr) & this->table_mask;
                segment = row & this->segment_mask;
                lock = this->half_open_segments[segment].lock;
                lock->read_lock(lock);
                item = this->half_open_table[row];
                while (item)
                {
                        half_open_t *half_open = item->value;

                        if (chunk_equals(addr, half_open->other))
                        {
                                count = half_open->count;
                                break;
                        }
                        item = item->next;
                }
                lock->unlock(lock);
        }
        else
        {
                for (segment = 0; segment < this->segment_count; segment++)
                {
                        lock = this->half_open_segments[segment].lock;
                        lock->read_lock(lock);
                        count += this->half_open_segments[segment].count;
                        lock->unlock(lock);
                }
        }
        return count;
}

METHOD(ike_sa_manager_t, flush, void,
        private_ike_sa_manager_t *this)
{
        /* destroy all list entries */
        enumerator_t *enumerator;
        entry_t *entry;
        u_int segment;

        lock_all_segments(this);
        DBG2(DBG_MGR, "going to destroy IKE_SA manager and all managed IKE_SA's");
        /* Step 1: drive out all waiting threads  */
        DBG2(DBG_MGR, "set driveout flags for all stored IKE_SA's");
        enumerator = create_table_enumerator(this);
        while (enumerator->enumerate(enumerator, &entry, &segment))
        {
                /* do not accept new threads, drive out waiting threads */
                entry->driveout_new_threads = TRUE;
                entry->driveout_waiting_threads = TRUE;
        }
        enumerator->destroy(enumerator);
        DBG2(DBG_MGR, "wait for all threads to leave IKE_SA's");
        /* Step 2: wait until all are gone */
        enumerator = create_table_enumerator(this);
        while (enumerator->enumerate(enumerator, &entry, &segment))
        {
                while (entry->waiting_threads || entry->checked_out)
                {
                        /* wake up all */
                        entry->condvar->broadcast(entry->condvar);
                        /* go sleeping until they are gone */
                        entry->condvar->wait(entry->condvar, this->segments[segment].mutex);
                }
        }
        enumerator->destroy(enumerator);
        DBG2(DBG_MGR, "delete all IKE_SA's");
        /* Step 3: initiate deletion of all IKE_SAs */
        enumerator = create_table_enumerator(this);
        while (enumerator->enumerate(enumerator, &entry, &segment))
        {
                charon->bus->set_sa(charon->bus, entry->ike_sa);
                if (entry->ike_sa->get_version(entry->ike_sa) == IKEV2)
                {       /* as the delete never gets processed, fire down events */
                        switch (entry->ike_sa->get_state(entry->ike_sa))
                        {
                                case IKE_ESTABLISHED:
                                case IKE_REKEYING:
                                case IKE_DELETING:
                                        charon->bus->ike_updown(charon->bus, entry->ike_sa, FALSE);
                                        break;
                                default:
                                        break;
                        }
                }
                entry->ike_sa->delete(entry->ike_sa);
        }
        enumerator->destroy(enumerator);

        DBG2(DBG_MGR, "destroy all entries");
        /* Step 4: destroy all entries */
        enumerator = create_table_enumerator(this);
        while (enumerator->enumerate(enumerator, &entry, &segment))
        {
                charon->bus->set_sa(charon->bus, entry->ike_sa);
                if (entry->half_open)
                {
                        remove_half_open(this, entry);
                }
                if (entry->my_id && entry->other_id)
                {
                        remove_connected_peers(this, entry);
                }
                if (entry->init_hash.ptr)
                {
                        remove_init_hash(this, entry->init_hash);
                }
                remove_entry_at((private_enumerator_t*)enumerator);
                entry_destroy(entry);
        }
        enumerator->destroy(enumerator);
        charon->bus->set_sa(charon->bus, NULL);
        unlock_all_segments(this);

        this->rng->destroy(this->rng);
        this->rng = NULL;
        this->hasher->destroy(this->hasher);
        this->hasher = NULL;
}

METHOD(ike_sa_manager_t, destroy, void,
        private_ike_sa_manager_t *this)
{
        u_int i;

        /* these are already cleared in flush() above */
        free(this->ike_sa_table);
        free(this->half_open_table);
        free(this->connected_peers_table);
        free(this->init_hashes_table);
        for (i = 0; i < this->segment_count; i++)
        {
                this->segments[i].mutex->destroy(this->segments[i].mutex);
                this->half_open_segments[i].lock->destroy(this->half_open_segments[i].lock);
                this->connected_peers_segments[i].lock->destroy(this->connected_peers_segments[i].lock);
                this->init_hashes_segments[i].mutex->destroy(this->init_hashes_segments[i].mutex);
        }
        free(this->segments);
        free(this->half_open_segments);
        free(this->connected_peers_segments);
        free(this->init_hashes_segments);

        free(this);
}

/**
 * This function returns the next-highest power of two for the given number.
 * The algorithm works by setting all bits on the right-hand side of the most
 * significant 1 to 1 and then increments the whole number so it rolls over
 * to the nearest power of two. Note: returns 0 for n == 0
 */
static u_int get_nearest_powerof2(u_int n)
{
        u_int i;

        --n;
        for (i = 1; i < sizeof(u_int) * 8; i <<= 1)
        {
                n |= n >> i;
        }
        return ++n;
}

/*
 * Described in header.
 */
ike_sa_manager_t *ike_sa_manager_create()
{
        private_ike_sa_manager_t *this;
        u_int i;

        INIT(this,
                .public = {
                        .checkout = _checkout,
                        .checkout_new = _checkout_new,
                        .checkout_by_message = _checkout_by_message,
                        .checkout_by_config = _checkout_by_config,
                        .checkout_by_id = _checkout_by_id,
                        .checkout_by_name = _checkout_by_name,
                        .check_uniqueness = _check_uniqueness,
                        .has_contact = _has_contact,
                        .create_enumerator = _create_enumerator,
                        .create_id_enumerator = _create_id_enumerator,
                        .checkin = _checkin,
                        .checkin_and_destroy = _checkin_and_destroy,
                        .get_count = _get_count,
                        .get_half_open_count = _get_half_open_count,
                        .flush = _flush,
                        .destroy = _destroy,
                },
        );

        this->hasher = lib->crypto->create_hasher(lib->crypto, HASH_PREFERRED);
        if (this->hasher == NULL)
        {
                DBG1(DBG_MGR, "manager initialization failed, no hasher supported");
                free(this);
                return NULL;
        }
        this->rng = lib->crypto->create_rng(lib->crypto, RNG_WEAK);
        if (this->rng == NULL)
        {
                DBG1(DBG_MGR, "manager initialization failed, no RNG supported");
                this->hasher->destroy(this->hasher);
                free(this);
                return NULL;
        }

        this->ikesa_limit = lib->settings->get_int(lib->settings,
                                                                        "%s.ikesa_limit", 0, charon->name);

        this->table_size = get_nearest_powerof2(lib->settings->get_int(
                                                                        lib->settings, "%s.ikesa_table_size",
                                                                        DEFAULT_HASHTABLE_SIZE, charon->name));
        this->table_size = max(1, min(this->table_size, MAX_HASHTABLE_SIZE));
        this->table_mask = this->table_size - 1;

        this->segment_count = get_nearest_powerof2(lib->settings->get_int(
                                                                        lib->settings, "%s.ikesa_table_segments",
                                                                        DEFAULT_SEGMENT_COUNT, charon->name));
        this->segment_count = max(1, min(this->segment_count, this->table_size));
        this->segment_mask = this->segment_count - 1;

        this->ike_sa_table = calloc(this->table_size, sizeof(table_item_t*));
        this->segments = (segment_t*)calloc(this->segment_count, sizeof(segment_t));
        for (i = 0; i < this->segment_count; i++)
        {
                this->segments[i].mutex = mutex_create(MUTEX_TYPE_RECURSIVE);
                this->segments[i].count = 0;
        }

        /* we use the same table parameters for the table to track half-open SAs */
        this->half_open_table = calloc(this->table_size, sizeof(table_item_t*));
        this->half_open_segments = calloc(this->segment_count, sizeof(shareable_segment_t));
        for (i = 0; i < this->segment_count; i++)
        {
                this->half_open_segments[i].lock = rwlock_create(RWLOCK_TYPE_DEFAULT);
                this->half_open_segments[i].count = 0;
        }

        /* also for the hash table used for duplicate tests */
        this->connected_peers_table = calloc(this->table_size, sizeof(table_item_t*));
        this->connected_peers_segments = calloc(this->segment_count, sizeof(shareable_segment_t));
        for (i = 0; i < this->segment_count; i++)
        {
                this->connected_peers_segments[i].lock = rwlock_create(RWLOCK_TYPE_DEFAULT);
                this->connected_peers_segments[i].count = 0;
        }

        /* and again for the table of hashes of seen initial IKE messages */
        this->init_hashes_table = calloc(this->table_size, sizeof(table_item_t*));
        this->init_hashes_segments = calloc(this->segment_count, sizeof(segment_t));
        for (i = 0; i < this->segment_count; i++)
        {
                this->init_hashes_segments[i].mutex = mutex_create(MUTEX_TYPE_RECURSIVE);
                this->init_hashes_segments[i].count = 0;
        }

        this->reuse_ikesa = lib->settings->get_bool(lib->settings,
                                                                                "%s.reuse_ikesa", TRUE, charon->name);
        return &this->public;
}