/* 
 * Copyright (C) 2008-2011 Teluu Inc. (http://www.teluu.com)
 * Copyright (C) 2003-2008 Benny Prijono <benny@prijono.org>
 *
 * 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  02111-1307  USA 
 */
#include <pjnath/turn_session.h>
#include <pjnath/errno.h>
#include <pjlib-util/srv_resolver.h>
#include <pj/addr_resolv.h>
#include <pj/assert.h>
#include <pj/errno.h>
#include <pj/hash.h>
#include <pj/lock.h>
#include <pj/log.h>
#include <pj/os.h>
#include <pj/pool.h>
#include <pj/rand.h>
#include <pj/sock.h>

#define PJ_TURN_CHANNEL_MIN         0x4000
#define PJ_TURN_CHANNEL_MAX         0x7FFF  /* inclusive */
#define PJ_TURN_CHANNEL_HTABLE_SIZE 8
#define PJ_TURN_PERM_HTABLE_SIZE    8

static const char *state_names[] = 
{
    "Null",
    "Resolving",
    "Resolved",
    "Allocating",
    "Ready",
    "Deallocating",
    "Deallocated",
    "Destroying"
};

enum timer_id_t
{
    TIMER_NONE,
    TIMER_KEEP_ALIVE,
    TIMER_DESTROY
};

/* This structure describes a channel binding. A channel binding is index by
 * the channel number or IP address and port number of the peer.
 */
struct ch_t
{
    /* The channel number */
    pj_uint16_t     num;

    /* PJ_TRUE if we've received successful response to ChannelBind request
     * for this channel.
     */
    pj_bool_t       bound;

    /* The peer IP address and port */
    pj_sockaddr     addr;

    /* The channel binding expiration */
    pj_time_val     expiry;
};


/* This structure describes a permission. A permission is identified by the
 * IP address only.
 */
struct perm_t
{
    /* Cache of hash value to speed-up lookup */
    pj_uint32_t     hval;

    /* The permission IP address. The port number MUST be zero */
    pj_sockaddr     addr;

    /* Number of peers that uses this permission. */
    unsigned        peer_cnt;

    /* Automatically renew this permission once it expires? */
    pj_bool_t       renew;

    /* The permission expiration */
    pj_time_val     expiry;

    /* Arbitrary/random pointer value (token) to map this perm with the 
     * request to create it. It is used to invalidate this perm when the 
     * request fails.
     */
    void           *req_token;
};

struct conn_bind_t
{
    pj_uint32_t      id;                /* Connection ID.       */
    pj_sockaddr      peer_addr;         /* Peer address.        */
    unsigned         peer_addr_len;
};

/* The TURN client session structure */
struct pj_turn_session
{
    pj_pool_t           *pool;
    const char          *obj_name;
    pj_turn_session_cb   cb;
    void                *user_data;
    pj_stun_config       stun_cfg;
    pj_bool_t            is_destroying;

    pj_grp_lock_t       *grp_lock;
    int                  busy;

    pj_turn_state_t      state;
    pj_status_t          last_status;
    pj_bool_t            pending_destroy;

    pj_stun_session     *stun;

    unsigned             lifetime;
    int                  ka_interval;
    pj_time_val          expiry;

    pj_timer_heap_t     *timer_heap;
    pj_timer_entry       timer;

    pj_uint16_t          default_port;

    pj_uint16_t          af;
    pj_turn_tp_type      conn_type;
    pj_uint16_t          srv_addr_cnt;
    pj_sockaddr         *srv_addr_list;
    pj_sockaddr         *srv_addr;

    pj_bool_t            pending_alloc;
    pj_turn_alloc_param  alloc_param;

    pj_sockaddr          mapped_addr;
    pj_sockaddr          relay_addr;

    pj_hash_table_t     *ch_table;
    pj_hash_table_t     *perm_table;

    pj_uint32_t          send_ind_tsx_id[3];
    /* tx_pkt must be 16bit aligned */
    pj_uint8_t           tx_pkt[PJ_TURN_MAX_PKT_LEN];

    pj_uint16_t          next_ch;
};


/*
 * Prototypes.
 */
static void sess_shutdown(pj_turn_session *sess,
                          pj_status_t status);
static void turn_sess_on_destroy(void *comp);
static void do_destroy(pj_turn_session *sess);
static void send_refresh(pj_turn_session *sess, int lifetime);
static pj_status_t stun_on_send_msg(pj_stun_session *sess,
                                    void *token,
                                    const void *pkt,
                                    pj_size_t pkt_size,
                                    const pj_sockaddr_t *dst_addr,
                                    unsigned addr_len);
static void stun_on_request_complete(pj_stun_session *sess,
                                     pj_status_t status,
                                     void *token,
                                     pj_stun_tx_data *tdata,
                                     const pj_stun_msg *response,
                                     const pj_sockaddr_t *src_addr,
                                     unsigned src_addr_len);
static pj_status_t stun_on_rx_indication(pj_stun_session *sess,
                                         const pj_uint8_t *pkt,
                                         unsigned pkt_len,
                                         const pj_stun_msg *msg,
                                         void *token,
                                         const pj_sockaddr_t *src_addr,
                                         unsigned src_addr_len);
static void dns_srv_resolver_cb(void *user_data,
                                pj_status_t status,
                                const pj_dns_srv_record *rec);
static struct ch_t *lookup_ch_by_addr(pj_turn_session *sess,
                                      const pj_sockaddr_t *addr,
                                      unsigned addr_len,
                                      pj_bool_t update,
                                      pj_bool_t bind_channel);
static struct ch_t *lookup_ch_by_chnum(pj_turn_session *sess,
                                       pj_uint16_t chnum);
static struct perm_t *lookup_perm(pj_turn_session *sess,
                                  const pj_sockaddr_t *addr,
                                  unsigned addr_len,
                                  pj_bool_t update);
static void invalidate_perm(pj_turn_session *sess,
                            struct perm_t *perm);
static void on_timer_event(pj_timer_heap_t *th, pj_timer_entry *e);


/*
 * Create default pj_turn_alloc_param.
 */
PJ_DEF(void) pj_turn_alloc_param_default(pj_turn_alloc_param *prm)
{
    pj_bzero(prm, sizeof(*prm));
    prm->peer_conn_type = PJ_TURN_TP_UDP;
}

/*
 * Duplicate pj_turn_alloc_param.
 */
PJ_DEF(void) pj_turn_alloc_param_copy( pj_pool_t *pool, 
                                       pj_turn_alloc_param *dst,
                                       const pj_turn_alloc_param *src)
{
    PJ_UNUSED_ARG(pool);
    pj_memcpy(dst, src, sizeof(*dst));
}

/*
 * Get TURN state name.
 */
PJ_DEF(const char*) pj_turn_state_name(pj_turn_state_t state)
{
    return state_names[state];
}

/*
 * Create TURN client session.
 */
PJ_DEF(pj_status_t) pj_turn_session_create( const pj_stun_config *cfg,
                                            const char *name,
                                            int af,
                                            pj_turn_tp_type conn_type,
                                            pj_grp_lock_t *grp_lock,
                                            const pj_turn_session_cb *cb,
                                            unsigned options,
                                            void *user_data,
                                            pj_turn_session **p_sess)
{
    pj_pool_t *pool;
    pj_turn_session *sess;
    pj_stun_session_cb stun_cb;
    pj_status_t status;

    PJ_ASSERT_RETURN(cfg && cfg->pf && cb && p_sess, PJ_EINVAL);
    PJ_ASSERT_RETURN(cb->on_send_pkt, PJ_EINVAL);

    PJ_UNUSED_ARG(options);

    if (name == NULL)
        name = "turn%p";

    /* Allocate and create TURN session */
    pool = pj_pool_create(cfg->pf, name, PJNATH_POOL_LEN_TURN_SESS,
                          PJNATH_POOL_INC_TURN_SESS, NULL);
    sess = PJ_POOL_ZALLOC_T(pool, pj_turn_session);
    sess->pool = pool;
    sess->obj_name = pool->obj_name;
    sess->timer_heap = cfg->timer_heap;
    sess->af = (pj_uint16_t)af;
    sess->conn_type = conn_type;
    sess->ka_interval = PJ_TURN_KEEP_ALIVE_SEC;
    sess->user_data = user_data;
    sess->next_ch = PJ_TURN_CHANNEL_MIN;
    pj_turn_alloc_param_default(&sess->alloc_param);

    /* Copy STUN session */
    pj_memcpy(&sess->stun_cfg, cfg, sizeof(pj_stun_config));

    /* Copy callback */
    pj_memcpy(&sess->cb, cb, sizeof(*cb));

    /* Peer hash table */
    sess->ch_table = pj_hash_create(pool, PJ_TURN_CHANNEL_HTABLE_SIZE);

    /* Permission hash table */
    sess->perm_table = pj_hash_create(pool, PJ_TURN_PERM_HTABLE_SIZE);

    /* Session lock */
    if (grp_lock) {
        sess->grp_lock = grp_lock;
    } else {
        status = pj_grp_lock_create(pool, NULL, &sess->grp_lock);
        if (status != PJ_SUCCESS) {
            pj_pool_release(pool);
            return status;
        }
    }

    pj_grp_lock_add_ref(sess->grp_lock);
    pj_grp_lock_add_handler(sess->grp_lock, pool, sess,
                            &turn_sess_on_destroy);

    /* Timer */
    pj_timer_entry_init(&sess->timer, TIMER_NONE, sess, &on_timer_event);

    /* Create STUN session */
    pj_bzero(&stun_cb, sizeof(stun_cb));
    stun_cb.on_send_msg = &stun_on_send_msg;
    stun_cb.on_request_complete = &stun_on_request_complete;
    stun_cb.on_rx_indication = &stun_on_rx_indication;
    status = pj_stun_session_create(&sess->stun_cfg, sess->obj_name, &stun_cb,
                                    PJ_FALSE, sess->grp_lock, &sess->stun);
    if (status != PJ_SUCCESS) {
        do_destroy(sess);
        return status;
    }

    /* Attach ourself to STUN session */
    pj_stun_session_set_user_data(sess->stun, sess);

    /* Done */

    PJ_LOG(4,(sess->obj_name, "TURN client session created"));

    *p_sess = sess;
    return PJ_SUCCESS;
}


static void turn_sess_on_destroy(void *comp)
{
    pj_turn_session *sess = (pj_turn_session*) comp;

    /* Destroy pool */
    if (sess->pool) {
        PJ_LOG(4,(sess->obj_name, "TURN client session destroyed"));
        pj_pool_safe_release(&sess->pool);
    }
}

/* Destroy */
static void do_destroy(pj_turn_session *sess)
{
    PJ_LOG(4,(sess->obj_name, "TURN session destroy request, ref_cnt=%d",
              pj_grp_lock_get_ref(sess->grp_lock)));

    pj_grp_lock_acquire(sess->grp_lock);
    if (sess->is_destroying) {
        pj_grp_lock_release(sess->grp_lock);
        return;
    }

    sess->is_destroying = PJ_TRUE;
    pj_timer_heap_cancel_if_active(sess->timer_heap, &sess->timer, TIMER_NONE);
    pj_stun_session_destroy(sess->stun);

    pj_grp_lock_dec_ref(sess->grp_lock);
    pj_grp_lock_release(sess->grp_lock);
}


/* Set session state */
static void set_state(pj_turn_session *sess, enum pj_turn_state_t state)
{
    pj_turn_state_t old_state = sess->state;

    if (state==sess->state)
        return;

    PJ_LOG(4,(sess->obj_name, "State changed %s --> %s",
              state_names[old_state], state_names[state]));
    sess->state = state;

    if (sess->cb.on_state) {
        (*sess->cb.on_state)(sess, old_state, state);
    }
}

/*
 * Notify application and shutdown the TURN session.
 */
static void sess_shutdown(pj_turn_session *sess,
                          pj_status_t status)
{
    pj_bool_t can_destroy = PJ_TRUE;

    PJ_LOG(4,(sess->obj_name, "Request to shutdown in state %s, cause:%d",
              state_names[sess->state], status));

    if (sess->last_status == PJ_SUCCESS && status != PJ_SUCCESS)
        sess->last_status = status;

    switch (sess->state) {
    case PJ_TURN_STATE_NULL:
        break;
    case PJ_TURN_STATE_RESOLVING:
        /* Wait for DNS callback invoked, it will call the this function
         * again. If the callback happens to get pending_destroy==FALSE,
         * the TURN allocation will call this function again.
         */
        sess->pending_destroy = PJ_TRUE;
        can_destroy = PJ_FALSE;
        break;
    case PJ_TURN_STATE_RESOLVED:
        break;
    case PJ_TURN_STATE_ALLOCATING:
        /* We need to wait until allocation complete */
        sess->pending_destroy = PJ_TRUE;
        can_destroy = PJ_FALSE;
        break;
    case PJ_TURN_STATE_READY:
        /* Send REFRESH with LIFETIME=0 */
        can_destroy = PJ_FALSE;
        send_refresh(sess, 0);
        break;
    case PJ_TURN_STATE_DEALLOCATING:
        can_destroy = PJ_FALSE;
        /* This may recursively call this function again with
         * state==PJ_TURN_STATE_DEALLOCATED.
         */
        /* No need to deallocate as we're already deallocating!
         * See https://github.com/pjsip/pjproject/issues/1551
        send_refresh(sess, 0);
        */
        break;
    case PJ_TURN_STATE_DEALLOCATED:
    case PJ_TURN_STATE_DESTROYING:
        break;
    }

    if (can_destroy) {
        /* Schedule destroy */
        pj_time_val delay = {0, 0};

        set_state(sess, PJ_TURN_STATE_DESTROYING);

        pj_timer_heap_cancel_if_active(sess->timer_heap, &sess->timer,
                                       TIMER_NONE);
        pj_timer_heap_schedule_w_grp_lock(sess->timer_heap, &sess->timer,
                                          &delay, TIMER_DESTROY,
                                          sess->grp_lock);
    }
}


/*
 * Public API to destroy TURN client session.
 */
PJ_DEF(pj_status_t) pj_turn_session_shutdown(pj_turn_session *sess)
{
    return pj_turn_session_shutdown2(sess, PJ_SUCCESS);
}

PJ_DEF(pj_status_t) pj_turn_session_shutdown2(pj_turn_session *sess,
					      pj_status_t last_err)
{
    PJ_ASSERT_RETURN(sess, PJ_EINVAL);

    pj_grp_lock_acquire(sess->grp_lock);

    if (last_err != PJ_SUCCESS && sess->last_status == PJ_SUCCESS)
        sess->last_status = last_err;

    sess_shutdown(sess, PJ_SUCCESS);

    pj_grp_lock_release(sess->grp_lock);

    return PJ_SUCCESS;
}


/**
 * Forcefully destroy the TURN session.
 */
PJ_DEF(pj_status_t) pj_turn_session_destroy( pj_turn_session *sess,
                                             pj_status_t last_err)
{
    PJ_ASSERT_RETURN(sess, PJ_EINVAL);

    if (last_err != PJ_SUCCESS && sess->last_status == PJ_SUCCESS)
        sess->last_status = last_err;
    set_state(sess, PJ_TURN_STATE_DEALLOCATED);
    sess_shutdown(sess, PJ_SUCCESS);
    return PJ_SUCCESS;
}


/*
 * Get TURN session info.
 */
PJ_DEF(pj_status_t) pj_turn_session_get_info( pj_turn_session *sess,
                                              pj_turn_session_info *info)
{
    pj_time_val now;

    PJ_ASSERT_RETURN(sess && info, PJ_EINVAL);

    pj_gettimeofday(&now);

    info->state = sess->state;
    info->conn_type = sess->conn_type;
    info->lifetime = sess->expiry.sec - now.sec;
    info->last_status = sess->last_status;

    if (sess->srv_addr)
        pj_memcpy(&info->server, sess->srv_addr, sizeof(info->server));
    else
        pj_bzero(&info->server, sizeof(info->server));

    pj_memcpy(&info->mapped_addr, &sess->mapped_addr, 
              sizeof(sess->mapped_addr));
    pj_memcpy(&info->relay_addr, &sess->relay_addr, 
              sizeof(sess->relay_addr));

    return PJ_SUCCESS;
}


/*
 * Re-assign user data.
 */
PJ_DEF(pj_status_t) pj_turn_session_set_user_data( pj_turn_session *sess,
                                                   void *user_data)
{
    sess->user_data = user_data;
    return PJ_SUCCESS;
}


/**
 * Retrieve user data.
 */
PJ_DEF(void*) pj_turn_session_get_user_data(pj_turn_session *sess)
{
    return sess->user_data;
}

/**
 * Get group lock.
 */
PJ_DEF(pj_grp_lock_t *) pj_turn_session_get_grp_lock(pj_turn_session *sess)
{
    PJ_ASSERT_RETURN(sess, NULL);
    return sess->grp_lock;
}

/*
 * Configure message logging. By default all flags are enabled.
 *
 * @param sess          The TURN client session.
 * @param flags         Bitmask combination of #pj_stun_sess_msg_log_flag
 */
PJ_DEF(void) pj_turn_session_set_log( pj_turn_session *sess,
                                      unsigned flags)
{
    pj_stun_session_set_log(sess->stun, flags);
}


/*
 * Set software name
 */
PJ_DEF(pj_status_t) pj_turn_session_set_software_name( pj_turn_session *sess,
                                                       const pj_str_t *sw)
{
    pj_status_t status;

    pj_grp_lock_acquire(sess->grp_lock);
    status = pj_stun_session_set_software_name(sess->stun, sw);
    pj_grp_lock_release(sess->grp_lock);

    return status;
}


/**
 * Set the server or domain name of the server.
 */
PJ_DEF(pj_status_t) pj_turn_session_set_server( pj_turn_session *sess,
                                                const pj_str_t *domain,
                                                int default_port,
                                                pj_dns_resolver *resolver)
{
    pj_sockaddr tmp_addr;
    pj_bool_t is_ip_addr;
    pj_status_t status;

    PJ_ASSERT_RETURN(sess && domain, PJ_EINVAL);
    PJ_ASSERT_RETURN(sess->state == PJ_TURN_STATE_NULL, PJ_EINVALIDOP);

    pj_grp_lock_acquire(sess->grp_lock);

    /* See if "domain" contains just IP address */
    tmp_addr.addr.sa_family = sess->af;
    status = pj_inet_pton(sess->af, domain, 
                          pj_sockaddr_get_addr(&tmp_addr));
    is_ip_addr = (status == PJ_SUCCESS);

    if (!is_ip_addr && resolver) {
        /* Resolve with DNS SRV resolution, and fallback to DNS A resolution
         * if default_port is specified.
         */
        unsigned opt = 0;
        pj_str_t res_name;

        switch (sess->conn_type) {
        case PJ_TURN_TP_UDP:
            res_name = pj_str("_turn._udp.");
            break;
        case PJ_TURN_TP_TCP:
            res_name = pj_str("_turn._tcp.");
            break;
        case PJ_TURN_TP_TLS:
            res_name = pj_str("_turns._tcp.");
            break;
        default:
            status = PJNATH_ETURNINTP;
            goto on_return;
        }

        /* Init DNS resolution option for IPv6 */
        if (sess->af == pj_AF_INET6())
            opt |= PJ_DNS_SRV_RESOLVE_AAAA_ONLY;

        /* Fallback to DNS A only if default port is specified */
        if (default_port>0 && default_port<65536) {
            if (sess->af == pj_AF_INET6())
                opt |= PJ_DNS_SRV_FALLBACK_AAAA;
            else
                opt |= PJ_DNS_SRV_FALLBACK_A;
            sess->default_port = (pj_uint16_t)default_port;
        }

        PJ_LOG(5,(sess->obj_name, "Resolving %.*s%.*s with DNS SRV",
                  (int)res_name.slen, res_name.ptr,
                  (int)domain->slen, domain->ptr));
        set_state(sess, PJ_TURN_STATE_RESOLVING);

        /* User may have destroyed us in the callback */
        if (sess->state != PJ_TURN_STATE_RESOLVING) {
            status = PJ_ECANCELLED;
            goto on_return;
        }

        /* Add reference before async DNS resolution */
        pj_grp_lock_add_ref(sess->grp_lock);

        status = pj_dns_srv_resolve(domain, &res_name, default_port, 
                                    sess->pool, resolver, opt, sess, 
                                    &dns_srv_resolver_cb, NULL);
        if (status != PJ_SUCCESS) {
            set_state(sess, PJ_TURN_STATE_NULL);
            pj_grp_lock_dec_ref(sess->grp_lock);
            goto on_return;
        }

    } else {
        /* Resolver is not specified, resolve with standard gethostbyname().
         * The default_port MUST be specified in this case.
         */
        pj_addrinfo *ai;
        unsigned i, cnt;

        /* Default port must be specified */
        PJ_ASSERT_RETURN(default_port>0 && default_port<65536, PJ_EINVAL);
        sess->default_port = (pj_uint16_t)default_port;

        cnt = PJ_TURN_MAX_DNS_SRV_CNT;
        ai = (pj_addrinfo*)
             pj_pool_calloc(sess->pool, cnt, sizeof(pj_addrinfo));

        PJ_LOG(5,(sess->obj_name, "Resolving %.*s with DNS A",
                  (int)domain->slen, domain->ptr));
        set_state(sess, PJ_TURN_STATE_RESOLVING);

        /* User may have destroyed us in the callback */
        if (sess->state != PJ_TURN_STATE_RESOLVING) {
            status = PJ_ECANCELLED;
            goto on_return;
        }

        status = pj_getaddrinfo(sess->af, domain, &cnt, ai);
        if (status != PJ_SUCCESS)
            goto on_return;

        sess->srv_addr_cnt = (pj_uint16_t)cnt;
        sess->srv_addr_list = (pj_sockaddr*)
                              pj_pool_calloc(sess->pool, cnt, 
                                             sizeof(pj_sockaddr));
        for (i=0; i<cnt; ++i) {
            pj_sockaddr *addr = &sess->srv_addr_list[i];
            pj_memcpy(addr, &ai[i].ai_addr, sizeof(pj_sockaddr));
            addr->addr.sa_family = sess->af;
            pj_sockaddr_set_port(addr, sess->default_port);
        }

        sess->srv_addr = &sess->srv_addr_list[0];
        set_state(sess, PJ_TURN_STATE_RESOLVED);
    }

on_return:
    pj_grp_lock_release(sess->grp_lock);
    return status;
}


/**
 * Set credential to be used by the session.
 */
PJ_DEF(pj_status_t) pj_turn_session_set_credential(pj_turn_session *sess,
                                             const pj_stun_auth_cred *cred)
{
    PJ_ASSERT_RETURN(sess && cred, PJ_EINVAL);
    PJ_ASSERT_RETURN(sess->stun, PJ_EINVALIDOP);

    pj_grp_lock_acquire(sess->grp_lock);

    pj_stun_session_set_credential(sess->stun, PJ_STUN_AUTH_LONG_TERM, cred);

    pj_grp_lock_release(sess->grp_lock);

    return PJ_SUCCESS;
}


/**
 * Create TURN allocation.
 */
PJ_DEF(pj_status_t) pj_turn_session_alloc(pj_turn_session *sess,
                                          const pj_turn_alloc_param *param)
{
    pj_stun_tx_data *tdata;
    pj_bool_t retransmit;
    pj_status_t status;

    PJ_ASSERT_RETURN(sess, PJ_EINVAL);
    PJ_ASSERT_RETURN(sess->state>PJ_TURN_STATE_NULL && 
                     sess->state<=PJ_TURN_STATE_RESOLVED, 
                     PJ_EINVALIDOP);
    PJ_ASSERT_RETURN(!param || param->peer_conn_type == PJ_TURN_TP_UDP ||
                     param->peer_conn_type == PJ_TURN_TP_TCP,
                     PJ_EINVAL);

    /* Verify address family in allocation param */
    if (param && param->af) {
        PJ_ASSERT_RETURN(param->af==pj_AF_INET() || param->af==pj_AF_INET6(),
                         PJ_EINVAL);
    }

    pj_grp_lock_acquire(sess->grp_lock);

    if (param && param != &sess->alloc_param) 
        pj_turn_alloc_param_copy(sess->pool, &sess->alloc_param, param);

    if (sess->state < PJ_TURN_STATE_RESOLVED) {
        sess->pending_alloc = PJ_TRUE;

        PJ_LOG(4,(sess->obj_name, "Pending ALLOCATE in state %s",
                  state_names[sess->state]));

        pj_grp_lock_release(sess->grp_lock);
        return PJ_SUCCESS;

    }

    /* Ready to allocate */
    pj_assert(sess->state == PJ_TURN_STATE_RESOLVED);
    
    /* Create a bare request */
    status = pj_stun_session_create_req(sess->stun, PJ_STUN_ALLOCATE_REQUEST,
                                        PJ_STUN_MAGIC, NULL, &tdata);
    if (status != PJ_SUCCESS) {
        pj_grp_lock_release(sess->grp_lock);
        return status;
    }

    /* MUST include REQUESTED-TRANSPORT attribute */
    pj_stun_msg_add_uint_attr(tdata->pool, tdata->msg,
        PJ_STUN_ATTR_REQ_TRANSPORT,
        PJ_STUN_SET_RT_PROTO(sess->alloc_param.peer_conn_type));

    /* Include BANDWIDTH if requested */
    if (sess->alloc_param.bandwidth > 0) {
        pj_stun_msg_add_uint_attr(tdata->pool, tdata->msg,
                                  PJ_STUN_ATTR_BANDWIDTH,
                                  sess->alloc_param.bandwidth);
    }

    /* Include LIFETIME if requested */
    if (sess->alloc_param.lifetime > 0) {
        pj_stun_msg_add_uint_attr(tdata->pool, tdata->msg,
                                  PJ_STUN_ATTR_LIFETIME,
                                  sess->alloc_param.lifetime);
    }

    /* Include ADDRESS-FAMILY if requested */
    if (sess->alloc_param.af || sess->af == pj_AF_INET6()) {
        enum  { IPV4_AF_TYPE = 0x01 << 24,
                IPV6_AF_TYPE = 0x02 << 24 };

        if (sess->alloc_param.af == pj_AF_INET6() ||
            (sess->alloc_param.af == 0 && sess->af == pj_AF_INET6()))
        {
            pj_stun_msg_add_uint_attr(tdata->pool, tdata->msg,
                                      PJ_STUN_ATTR_REQ_ADDR_TYPE, IPV6_AF_TYPE);
        } else if (sess->alloc_param.af == pj_AF_INET()) {
            /* For IPv4, only add the attribute when explicitly requested */
            pj_stun_msg_add_uint_attr(tdata->pool, tdata->msg,
                                      PJ_STUN_ATTR_REQ_ADDR_TYPE, IPV4_AF_TYPE);
        }
    }

    /* Server address must be set */
    pj_assert(sess->srv_addr != NULL);

    /* Send request */
    set_state(sess, PJ_TURN_STATE_ALLOCATING);
    retransmit = (sess->conn_type == PJ_TURN_TP_UDP);
    status = pj_stun_session_send_msg(sess->stun, NULL, PJ_FALSE, 
                                      retransmit, sess->srv_addr,
                                      pj_sockaddr_get_len(sess->srv_addr), 
                                      tdata);
    if (status != PJ_SUCCESS) {
        /* Set state back to RESOLVED. We don't want to destroy session now,
         * let the application do it if it wants to.
         */
        /* Set state back to RESOLVED may cause infinite loop (see #1942). */
        //set_state(sess, PJ_TURN_STATE_RESOLVED);
    }

    pj_grp_lock_release(sess->grp_lock);
    return status;
}


/*
 * Install or renew permissions
 */
PJ_DEF(pj_status_t) pj_turn_session_set_perm( pj_turn_session *sess,
                                              unsigned addr_cnt,
                                              const pj_sockaddr addr[],
                                              unsigned options)
{
    pj_stun_tx_data *tdata;
    pj_hash_iterator_t it_buf, *it;
    void *req_token;
    unsigned i, attr_added=0;
    pj_status_t status;

    PJ_ASSERT_RETURN(sess && addr_cnt && addr, PJ_EINVAL);

    pj_grp_lock_acquire(sess->grp_lock);

    /* Create a bare CreatePermission request */
    status = pj_stun_session_create_req(sess->stun, 
                                        PJ_STUN_CREATE_PERM_REQUEST,
                                        PJ_STUN_MAGIC, NULL, &tdata);
    if (status != PJ_SUCCESS) {
        pj_grp_lock_release(sess->grp_lock);
        return status;
    }

    /* Create request token to map the request to the perm structures
     * which the request belongs.
     */
    req_token = (void*)(pj_ssize_t)pj_rand();

    /* Process the addresses */
    for (i=0; i<addr_cnt; ++i) {
        struct perm_t *perm;

        /* Lookup the perm structure and create if it doesn't exist */
        perm = lookup_perm(sess, &addr[i], pj_sockaddr_get_len(&addr[i]),
                           PJ_TRUE);
        perm->renew = (options & 0x01);

        /* Only add to the request if the request doesn't contain this
         * address yet.
         */
        if (perm->req_token != req_token) {
            perm->req_token = req_token;

            /* Add XOR-PEER-ADDRESS */
            status = pj_stun_msg_add_sockaddr_attr(tdata->pool, tdata->msg,
                                                   PJ_STUN_ATTR_XOR_PEER_ADDR,
                                                   PJ_TRUE,
                                                   &addr[i],
                                                   sizeof(addr[i]));
            if (status != PJ_SUCCESS)
                goto on_error;

            ++attr_added;
        }
    }

    /* No address to set */
    if (attr_added == 0) {
        pj_stun_msg_destroy_tdata(sess->stun, tdata);
        pj_grp_lock_release(sess->grp_lock);
        return PJ_SUCCESS;
    }

    /* Send the request */
    status = pj_stun_session_send_msg(sess->stun, req_token, PJ_FALSE, 
                                      (sess->conn_type==PJ_TURN_TP_UDP),
                                      sess->srv_addr,
                                      pj_sockaddr_get_len(sess->srv_addr), 
                                      tdata);
    if (status != PJ_SUCCESS) {
        /* tdata is already destroyed */
        tdata = NULL;
        goto on_error;
    }

    pj_grp_lock_release(sess->grp_lock);
    return PJ_SUCCESS;

on_error:
    /* destroy tdata */
    if (tdata) {
        pj_stun_msg_destroy_tdata(sess->stun, tdata);
    }
    /* invalidate perm structures associated with this request */
    it = pj_hash_first(sess->perm_table, &it_buf);
    while (it) {
        struct perm_t *perm = (struct perm_t*)
                              pj_hash_this(sess->perm_table, it);
        it = pj_hash_next(sess->perm_table, it);
        if (perm->req_token == req_token)
            invalidate_perm(sess, perm);
    }
    pj_grp_lock_release(sess->grp_lock);
    return status;
}

/*
 * Send REFRESH
 */
static void send_refresh(pj_turn_session *sess, int lifetime)
{
    pj_stun_tx_data *tdata;
    pj_status_t status;

    PJ_ASSERT_ON_FAIL(sess->state==PJ_TURN_STATE_READY, return);

    /* Create a bare REFRESH request */
    status = pj_stun_session_create_req(sess->stun, PJ_STUN_REFRESH_REQUEST,
                                        PJ_STUN_MAGIC, NULL, &tdata);
    if (status != PJ_SUCCESS)
        goto on_error;

    /* Add LIFETIME */
    if (lifetime >= 0) {
        pj_stun_msg_add_uint_attr(tdata->pool, tdata->msg,
                                  PJ_STUN_ATTR_LIFETIME, lifetime);
    }

    /* Send request */
    if (lifetime == 0) {
        set_state(sess, PJ_TURN_STATE_DEALLOCATING);
    }

    status = pj_stun_session_send_msg(sess->stun, NULL, PJ_FALSE, 
                                      (sess->conn_type==PJ_TURN_TP_UDP),
                                      sess->srv_addr,
                                      pj_sockaddr_get_len(sess->srv_addr), 
                                      tdata);
    if (status != PJ_SUCCESS)
        goto on_error;

    return;

on_error:
    if (lifetime == 0) {
        set_state(sess, PJ_TURN_STATE_DEALLOCATED);
        sess_shutdown(sess, status);
    }
}


/**
 * Relay data to the specified peer through the session.
 */
PJ_DEF(pj_status_t) pj_turn_session_sendto( pj_turn_session *sess,
                                            const pj_uint8_t *pkt,
                                            unsigned pkt_len,
                                            const pj_sockaddr_t *addr,
                                            unsigned addr_len)
{
    struct ch_t *ch;
    struct perm_t *perm;
    pj_status_t status;

    PJ_ASSERT_RETURN(sess && pkt && pkt_len && addr && addr_len, 
                     PJ_EINVAL);

    /* Return error if we're not ready */
    if (sess->state != PJ_TURN_STATE_READY) {
        return PJ_EIGNORED;
    }

    /* Lock session now */
    pj_grp_lock_acquire(sess->grp_lock);

    /* Lookup permission first */
    perm = lookup_perm(sess, addr, pj_sockaddr_get_len(addr), PJ_FALSE);
    if (perm == NULL) {
        /* Permission doesn't exist, install it first */
        char ipstr[PJ_INET6_ADDRSTRLEN+2];

        PJ_LOG(4,(sess->obj_name, 
                  "sendto(): IP %s has no permission, requesting it first..",
                  pj_sockaddr_print(addr, ipstr, sizeof(ipstr), 2)));

        status = pj_turn_session_set_perm(sess, 1, (const pj_sockaddr*)addr, 
                                          0);
        if (status != PJ_SUCCESS) {
            pj_grp_lock_release(sess->grp_lock);
            return status;
        }
    }

    /* If peer connection is TCP (RFC 6062), send it directly */
    if (sess->alloc_param.peer_conn_type == PJ_TURN_TP_TCP) {
        status = sess->cb.on_send_pkt(sess, pkt, pkt_len, addr, addr_len);
        goto on_return;
    }

    /* See if the peer is bound to a channel number */
    ch = lookup_ch_by_addr(sess, addr, pj_sockaddr_get_len(addr), 
                           PJ_FALSE, PJ_FALSE);
    if (ch && ch->num != PJ_TURN_INVALID_CHANNEL && ch->bound) {
        unsigned total_len;

        /* Peer is assigned a channel number, we can use ChannelData */
        pj_turn_channel_data *cd = (pj_turn_channel_data*)sess->tx_pkt;
        
        pj_assert(sizeof(*cd)==4);

        /* Calculate total length, including paddings */
        total_len = (pkt_len + sizeof(*cd) + 3) & (~3);
        if (total_len > sizeof(sess->tx_pkt)) {
            status = PJ_ETOOBIG;
            goto on_return;
        }

        cd->ch_number = pj_htons((pj_uint16_t)ch->num);
        cd->length = pj_htons((pj_uint16_t)pkt_len);
        pj_memcpy(cd+1, pkt, pkt_len);

        pj_assert(sess->srv_addr != NULL);

        status = sess->cb.on_send_pkt(sess, sess->tx_pkt, total_len,
                                      sess->srv_addr,
                                      pj_sockaddr_get_len(sess->srv_addr));

    } else {
        /* Use Send Indication. */
        pj_stun_sockaddr_attr peer_attr;
        pj_stun_binary_attr data_attr;
        pj_stun_msg send_ind;
        pj_size_t send_ind_len;

        /* Increment counter */
        ++sess->send_ind_tsx_id[2];

        /* Create blank SEND-INDICATION */
        status = pj_stun_msg_init(&send_ind, PJ_STUN_SEND_INDICATION,
                                  PJ_STUN_MAGIC, 
                                  (const pj_uint8_t*)sess->send_ind_tsx_id);
        if (status != PJ_SUCCESS)
            goto on_return;

        /* Add XOR-PEER-ADDRESS */
        pj_stun_sockaddr_attr_init(&peer_attr, PJ_STUN_ATTR_XOR_PEER_ADDR,
                                   PJ_TRUE, addr, addr_len);
        pj_stun_msg_add_attr(&send_ind, (pj_stun_attr_hdr*)&peer_attr);

        /* Add DATA attribute */
        pj_stun_binary_attr_init(&data_attr, NULL, PJ_STUN_ATTR_DATA, NULL, 0);
        data_attr.data = (pj_uint8_t*)pkt;
        data_attr.length = pkt_len;
        pj_stun_msg_add_attr(&send_ind, (pj_stun_attr_hdr*)&data_attr);

        /* Encode the message */
        status = pj_stun_msg_encode(&send_ind, sess->tx_pkt, 
                                    sizeof(sess->tx_pkt), 0,
                                    NULL, &send_ind_len);
        if (status != PJ_SUCCESS)
            goto on_return;

        /* Send the Send Indication */
        status = sess->cb.on_send_pkt(sess, sess->tx_pkt, 
                                      (unsigned)send_ind_len,
                                      sess->srv_addr,
                                      pj_sockaddr_get_len(sess->srv_addr));
    }

on_return:
    pj_grp_lock_release(sess->grp_lock);
    return status;
}


/**
 * Bind a peer address to a channel number.
 */
PJ_DEF(pj_status_t) pj_turn_session_bind_channel(pj_turn_session *sess,
                                                 const pj_sockaddr_t *peer_adr,
                                                 unsigned addr_len)
{
    struct ch_t *ch;
    pj_stun_tx_data *tdata;
    pj_uint16_t ch_num;
    pj_status_t status;

    PJ_ASSERT_RETURN(sess && peer_adr && addr_len, PJ_EINVAL);
    PJ_ASSERT_RETURN(sess->state == PJ_TURN_STATE_READY, PJ_EINVALIDOP);

    pj_grp_lock_acquire(sess->grp_lock);

    /* Create blank ChannelBind request */
    status = pj_stun_session_create_req(sess->stun, 
                                        PJ_STUN_CHANNEL_BIND_REQUEST,
                                        PJ_STUN_MAGIC, NULL, &tdata);
    if (status != PJ_SUCCESS)
        goto on_return;

    /* Lookup if this peer has already been assigned a number */
    ch = lookup_ch_by_addr(sess, peer_adr, pj_sockaddr_get_len(peer_adr),
                           PJ_TRUE, PJ_FALSE);
    pj_assert(ch);

    if (ch->num != PJ_TURN_INVALID_CHANNEL) {
        /* Channel is already bound. This is a refresh request. */
        ch_num = ch->num;
    } else {
        PJ_ASSERT_ON_FAIL(sess->next_ch <= PJ_TURN_CHANNEL_MAX, 
                            {status=PJ_ETOOMANY; goto on_return;});
        ch->num = ch_num = sess->next_ch++;
    }

    /* Add CHANNEL-NUMBER attribute */
    pj_stun_msg_add_uint_attr(tdata->pool, tdata->msg,
                              PJ_STUN_ATTR_CHANNEL_NUMBER,
                              PJ_STUN_SET_CH_NB(ch_num));

    /* Add XOR-PEER-ADDRESS attribute */
    pj_stun_msg_add_sockaddr_attr(tdata->pool, tdata->msg,
                                  PJ_STUN_ATTR_XOR_PEER_ADDR, PJ_TRUE,
                                  peer_adr, addr_len);

    /* Send the request, associate peer data structure with tdata 
     * for future reference when we receive the ChannelBind response.
     */
    status = pj_stun_session_send_msg(sess->stun, ch, PJ_FALSE, 
                                      (sess->conn_type==PJ_TURN_TP_UDP),
                                      sess->srv_addr,
                                      pj_sockaddr_get_len(sess->srv_addr),
                                      tdata);

on_return:
    pj_grp_lock_release(sess->grp_lock);
    return status;
}


/**
 * Send ConnectionBind request.
 */
PJ_DEF(pj_status_t) pj_turn_session_connection_bind(
                                            pj_turn_session *sess,
                                            pj_pool_t *pool,
                                            pj_uint32_t conn_id,
                                            const pj_sockaddr_t *peer_addr,
                                            unsigned addr_len)
{
    pj_stun_tx_data *tdata;
    struct conn_bind_t *conn_bind;
    pj_status_t status;

    PJ_ASSERT_RETURN(sess && pool && conn_id && peer_addr && addr_len,
                     PJ_EINVAL);
    PJ_ASSERT_RETURN(sess->state == PJ_TURN_STATE_READY, PJ_EINVALIDOP);

    pj_grp_lock_acquire(sess->grp_lock);

    /* Create blank ConnectionBind request */
    status = pj_stun_session_create_req(sess->stun, 
                                        PJ_STUN_CONNECTION_BIND_REQUEST,
                                        PJ_STUN_MAGIC, NULL, &tdata);
    if (status != PJ_SUCCESS)
        goto on_return;

    /* Add CONNECTION_ID attribute */
    pj_stun_msg_add_uint_attr(tdata->pool, tdata->msg,
                              PJ_STUN_ATTR_CONNECTION_ID,
                              conn_id);

    conn_bind = PJ_POOL_ZALLOC_T(pool, struct conn_bind_t);
    conn_bind->id = conn_id;
    pj_sockaddr_cp(&conn_bind->peer_addr, peer_addr);
    conn_bind->peer_addr_len = addr_len;

    /* Send the request, associate connection data structure with tdata 
     * for future reference when we receive the ConnectionBind response.
     */
    status = pj_stun_session_send_msg(sess->stun, conn_bind, PJ_FALSE,
                                      PJ_FALSE, peer_addr, addr_len, tdata);

on_return:
    pj_grp_lock_release(sess->grp_lock);
    return status;
}

/**
 * Send Connect request.
 */
PJ_DEF(pj_status_t) pj_turn_session_connect(pj_turn_session *sess,
                                            const pj_sockaddr_t *peer_addr,
                                            unsigned addr_len)
{
    pj_stun_tx_data *tdata;
    pj_status_t status;

    PJ_ASSERT_RETURN(sess && peer_addr && addr_len, PJ_EINVAL);
    PJ_ASSERT_RETURN(sess->state == PJ_TURN_STATE_READY, PJ_EINVALIDOP);

    pj_grp_lock_acquire(sess->grp_lock);

    /* Create blank Connect request */
    status = pj_stun_session_create_req(sess->stun, PJ_STUN_CONNECT_REQUEST,
                                        PJ_STUN_MAGIC, NULL, &tdata);
    if (status != PJ_SUCCESS)
        goto on_return;

    status = pj_stun_msg_add_sockaddr_attr(tdata->pool, tdata->msg,
                                           PJ_STUN_ATTR_XOR_PEER_ADDR,
                                           PJ_TRUE, peer_addr, addr_len);
    if (status != PJ_SUCCESS) goto on_return;
    status = pj_stun_session_send_msg(sess->stun, (void *)peer_addr, PJ_FALSE,
                                      PJ_FALSE, sess->srv_addr,
                                      pj_sockaddr_get_len(sess->srv_addr),
                                      tdata);

on_return:
    pj_grp_lock_release(sess->grp_lock);
    return status;
}

PJ_DEF(pj_status_t) pj_turn_session_on_rx_pkt(pj_turn_session *sess,
                                              void *pkt,
                                              pj_size_t pkt_len,
                                              pj_size_t *parsed_len)
{
    pj_turn_session_on_rx_pkt_param prm;
    pj_status_t status;
    
    pj_bzero(&prm, sizeof(prm));
    prm.pkt = pkt;
    prm.pkt_len = pkt_len;
    status = pj_turn_session_on_rx_pkt2(sess, &prm);
    if (status == PJ_SUCCESS && parsed_len)
        *parsed_len = prm.parsed_len;
    return status;
}

/**
 * Notify TURN client session upon receiving a packet from server.
 * The packet maybe a STUN packet or ChannelData packet.
 */
PJ_DEF(pj_status_t) pj_turn_session_on_rx_pkt2(
                                pj_turn_session *sess,
                                pj_turn_session_on_rx_pkt_param *prm)
{
    pj_bool_t is_stun;
    pj_status_t status;
    pj_bool_t is_datagram;

    /* Packet could be ChannelData or STUN message (response or
     * indication).
     */

    /* Start locking the session */
    pj_grp_lock_acquire(sess->grp_lock);

    is_datagram = (sess->conn_type==PJ_TURN_TP_UDP);

    /* Quickly check if this is STUN message */
    is_stun = ((((pj_uint8_t*)prm->pkt)[0] & 0xC0) == 0);

    if (is_stun) {
        /* This looks like STUN, give it to the STUN session */
        unsigned options;
        const pj_sockaddr_t *src_addr = prm->src_addr?
                                        prm->src_addr:sess->srv_addr;
        unsigned src_addr_len = prm->src_addr_len? prm->src_addr_len:
                                pj_sockaddr_get_len(sess->srv_addr);

        options = PJ_STUN_CHECK_PACKET | PJ_STUN_NO_FINGERPRINT_CHECK;
        if (is_datagram)
            options |= PJ_STUN_IS_DATAGRAM;
        status=pj_stun_session_on_rx_pkt(sess->stun, prm->pkt, prm->pkt_len,
                                         options, NULL, &prm->parsed_len,
                                         src_addr, src_addr_len);

    } else {
        /* This must be ChannelData. */
        pj_turn_channel_data cd;
        struct ch_t *ch;

        if (prm->pkt_len < 4) {
            prm->parsed_len = 0;
            status = PJ_ETOOSMALL;
            goto on_return;
        }

        /* Decode ChannelData packet */
        pj_memcpy(&cd, prm->pkt, sizeof(pj_turn_channel_data));
        cd.ch_number = pj_ntohs(cd.ch_number);
        cd.length = pj_ntohs(cd.length);

        /* Check that size is sane */
        if (prm->pkt_len < cd.length+sizeof(cd)) {
            if (is_datagram) {
                /* Discard the datagram */
                prm->parsed_len = prm->pkt_len;
            } else {
                /* Insufficient fragment */
                prm->parsed_len = 0;
            }
            status = PJ_ETOOSMALL;
            goto on_return;
        } else {
            /* Apply padding too */
            prm->parsed_len = ((cd.length + 3) & (~3)) + sizeof(cd);
        }

        /* Lookup channel */
        ch = lookup_ch_by_chnum(sess, cd.ch_number);
        if (!ch || !ch->bound) {
            status = PJ_ENOTFOUND;
            goto on_return;
        }

        /* Notify application */
        if (sess->cb.on_rx_data) {
            (*sess->cb.on_rx_data)(sess, ((pj_uint8_t*)prm->pkt)+sizeof(cd), 
                                   cd.length, &ch->addr,
                                   pj_sockaddr_get_len(&ch->addr));
        }

        status = PJ_SUCCESS;
    }

on_return:
    pj_grp_lock_release(sess->grp_lock);
    return status;
}


/*
 * This is a callback from STUN session to send outgoing packet.
 */
static pj_status_t stun_on_send_msg(pj_stun_session *stun,
                                    void *token,
                                    const void *pkt,
                                    pj_size_t pkt_size,
                                    const pj_sockaddr_t *dst_addr,
                                    unsigned addr_len)
{
    pj_turn_session *sess;

    PJ_UNUSED_ARG(token);

    sess = (pj_turn_session*) pj_stun_session_get_user_data(stun);
    if (sess->cb.on_stun_send_pkt) {
        return (*sess->cb.on_stun_send_pkt)(sess, (const pj_uint8_t*)pkt,
                                            (unsigned)pkt_size,
                                            dst_addr, addr_len);
    } else {
        return (*sess->cb.on_send_pkt)(sess, (const pj_uint8_t*)pkt,
                                       (unsigned)pkt_size,
                                       dst_addr, addr_len);
    }
}


/*
 * Handle failed ALLOCATE or REFRESH request. This may switch to alternate
 * server if we have one.
 */
static void on_session_fail( pj_turn_session *sess, 
                             enum pj_stun_method_e method,
                             pj_status_t status,
                             const pj_str_t *reason)
{
    sess->last_status = status;

    do {
        pj_str_t reason1;
        char err_msg[PJ_ERR_MSG_SIZE];

        if (reason == NULL) {
            pj_strerror(status, err_msg, sizeof(err_msg));
            reason1 = pj_str(err_msg);
            reason = &reason1;
        }

        PJ_LOG(4,(sess->obj_name, "%s error: %.*s",
                  pj_stun_get_method_name(method),
                  (int)reason->slen, reason->ptr));

        /* If this is ALLOCATE response and we don't have more server 
         * addresses to try, notify application and destroy the TURN
         * session.
         */
        if (method==PJ_STUN_ALLOCATE_METHOD &&
            sess->srv_addr == &sess->srv_addr_list[sess->srv_addr_cnt-1]) 
        {

            set_state(sess, PJ_TURN_STATE_DEALLOCATED);
            sess_shutdown(sess, status);
            return;
        }

        /* Otherwise if this is not ALLOCATE response, notify application
         * that session has been TERMINATED.
         */
        if (method!=PJ_STUN_ALLOCATE_METHOD) {
            set_state(sess, PJ_TURN_STATE_DEALLOCATED);
            sess_shutdown(sess, status);
            return;
        }

        /* Try next server */
        ++sess->srv_addr;
        reason = NULL;

        PJ_LOG(4,(sess->obj_name, "Trying next server"));
        set_state(sess, PJ_TURN_STATE_RESOLVED);

    } while (0);
}


/*
 * Handle successful response to ALLOCATE or REFRESH request.
 */
static void on_allocate_success(pj_turn_session *sess, 
                                enum pj_stun_method_e method,
                                const pj_stun_msg *msg)
{
    const pj_stun_lifetime_attr *lf_attr;
    const pj_stun_xor_relayed_addr_attr *raddr_attr;
    const pj_stun_sockaddr_attr *mapped_attr;
    pj_str_t s;

    /* Must have LIFETIME attribute */
    lf_attr = (const pj_stun_lifetime_attr*)
              pj_stun_msg_find_attr(msg, PJ_STUN_ATTR_LIFETIME, 0);
    if (lf_attr == NULL) {
        on_session_fail(sess, method, PJNATH_EINSTUNMSG,
                        pj_cstr(&s, "Error: Missing LIFETIME attribute"));
        return;
    }

    /* If LIFETIME is zero, this is a deallocation */
    if (lf_attr->value == 0) {
        set_state(sess, PJ_TURN_STATE_DEALLOCATED);
        sess_shutdown(sess, PJ_SUCCESS);
        return;
    }

    /* Update lifetime and keep-alive interval */
    sess->lifetime = lf_attr->value;
    pj_gettimeofday(&sess->expiry);

    if (sess->lifetime < PJ_TURN_KEEP_ALIVE_SEC) {
        if (sess->lifetime <= 2) {
            on_session_fail(sess, method, PJ_ETOOSMALL,
                             pj_cstr(&s, "Error: LIFETIME too small"));
            return;
        }
        sess->ka_interval = sess->lifetime - 2;
        sess->expiry.sec += (sess->ka_interval-1);
    } else {
        int timeout;

        sess->ka_interval = PJ_TURN_KEEP_ALIVE_SEC;

        timeout = sess->lifetime - PJ_TURN_REFRESH_SEC_BEFORE;
        if (timeout < sess->ka_interval)
            timeout = sess->ka_interval - 1;

        sess->expiry.sec += timeout;
    }

    /* Check that relayed transport address contains correct
     * address family.
     */
    raddr_attr = (const pj_stun_xor_relayed_addr_attr*)
                 pj_stun_msg_find_attr(msg, PJ_STUN_ATTR_XOR_RELAYED_ADDR, 0);
    if (raddr_attr == NULL && method==PJ_STUN_ALLOCATE_METHOD) {
        on_session_fail(sess, method, PJNATH_EINSTUNMSG,
                        pj_cstr(&s, "Error: Received ALLOCATE without "
                                    "RELAY-ADDRESS attribute"));
        return;
    }
    if (raddr_attr &&
        ((sess->alloc_param.af != 0 &&
          raddr_attr->sockaddr.addr.sa_family != sess->alloc_param.af) ||
         (sess->alloc_param.af == 0 &&
          raddr_attr->sockaddr.addr.sa_family != sess->af)))
    {
        on_session_fail(sess, method, PJNATH_EINSTUNMSG,
                        pj_cstr(&s, "Error: Mismatched RELAY-ADDRESS "
                                    "address family"));
        return;
    }
    if (raddr_attr && !pj_sockaddr_has_addr(&raddr_attr->sockaddr)) {
        on_session_fail(sess, method, PJNATH_EINSTUNMSG,
                        pj_cstr(&s, "Error: Invalid IP address in "
                                    "RELAY-ADDRESS attribute"));
        return;
    }
    
    /* Save relayed address */
    if (raddr_attr) {
        /* If we already have relay address, check if the relay address 
         * in the response matches our relay address.
         */
        if (pj_sockaddr_has_addr(&sess->relay_addr)) {
            if (pj_sockaddr_cmp(&sess->relay_addr, &raddr_attr->sockaddr)) {
                on_session_fail(sess, method, PJNATH_EINSTUNMSG,
                                pj_cstr(&s, "Error: different RELAY-ADDRESS is"
                                            "returned by server"));
                return;
            }
        } else {
            /* Otherwise save the relayed address */
            pj_memcpy(&sess->relay_addr, &raddr_attr->sockaddr, 
                      sizeof(pj_sockaddr));
        }
    }

    /* Get mapped address */
    mapped_attr = (const pj_stun_sockaddr_attr*)
                  pj_stun_msg_find_attr(msg, PJ_STUN_ATTR_XOR_MAPPED_ADDR, 0);
    if (mapped_attr) {
        pj_memcpy(&sess->mapped_addr, &mapped_attr->sockaddr,
                  sizeof(mapped_attr->sockaddr));
    }

    /* Success */

    /* Cancel existing keep-alive timer, if any */
    pj_assert(sess->timer.id != TIMER_DESTROY);
    if (sess->timer.id == TIMER_KEEP_ALIVE) {
        pj_timer_heap_cancel_if_active(sess->timer_heap, &sess->timer,
                                       TIMER_NONE);
    }

    /* Start keep-alive timer once allocation succeeds */
    if (sess->state < PJ_TURN_STATE_DEALLOCATING) {
        pj_time_val timeout;
        timeout.sec = sess->ka_interval;
        timeout.msec = 0;

        pj_timer_heap_schedule_w_grp_lock(sess->timer_heap, &sess->timer,
                                          &timeout, TIMER_KEEP_ALIVE,
                                          sess->grp_lock);

        set_state(sess, PJ_TURN_STATE_READY);
    }
}

/*
 * Notification from STUN session on request completion.
 */
static void stun_on_request_complete(pj_stun_session *stun,
                                     pj_status_t status,
                                     void *token,
                                     pj_stun_tx_data *tdata,
                                     const pj_stun_msg *response,
                                     const pj_sockaddr_t *src_addr,
                                     unsigned src_addr_len)
{
    pj_turn_session *sess;
    enum pj_stun_method_e method = (enum pj_stun_method_e) 
                                   PJ_STUN_GET_METHOD(tdata->msg->hdr.type);

    PJ_UNUSED_ARG(src_addr);
    PJ_UNUSED_ARG(src_addr_len);

    sess = (pj_turn_session*)pj_stun_session_get_user_data(stun);

    if (method == PJ_STUN_ALLOCATE_METHOD) {

        /* Destroy if we have pending destroy request */
        if (sess->pending_destroy) {
            if (status == PJ_SUCCESS)
                sess->state = PJ_TURN_STATE_READY;
            else
                sess->state = PJ_TURN_STATE_DEALLOCATED;
            sess_shutdown(sess, PJ_SUCCESS);
            return;
        }

        /* Handle ALLOCATE response */
        if (status==PJ_SUCCESS && 
            PJ_STUN_IS_SUCCESS_RESPONSE(response->hdr.type)) 
        {

            /* Successful Allocate response */
            on_allocate_success(sess, method, response);

        } else {
            /* Failed Allocate request */
            const pj_str_t *err_msg = NULL;

            if (status == PJ_SUCCESS) {
                const pj_stun_errcode_attr *err_attr;
                err_attr = (const pj_stun_errcode_attr*)
                           pj_stun_msg_find_attr(response,
                                                 PJ_STUN_ATTR_ERROR_CODE, 0);
                if (err_attr) {
                    status = PJ_STATUS_FROM_STUN_CODE(err_attr->err_code);
                    err_msg = &err_attr->reason;
                } else {
                    status = PJNATH_EINSTUNMSG;
                }
            }

            on_session_fail(sess, method, status, err_msg);
        }

    } else if (method == PJ_STUN_REFRESH_METHOD) {
        /* Handle Refresh response */
        if (status==PJ_SUCCESS && 
            PJ_STUN_IS_SUCCESS_RESPONSE(response->hdr.type)) 
        {
            /* Success, schedule next refresh. */
            on_allocate_success(sess, method, response);

        } else {
            /* Failed Refresh request */
            const pj_str_t *err_msg = NULL;

            pj_assert(status != PJ_SUCCESS);

            if (response) {
                const pj_stun_errcode_attr *err_attr;
                err_attr = (const pj_stun_errcode_attr*)
                           pj_stun_msg_find_attr(response,
                                                 PJ_STUN_ATTR_ERROR_CODE, 0);
                if (err_attr) {
                    status = PJ_STATUS_FROM_STUN_CODE(err_attr->err_code);
                    err_msg = &err_attr->reason;
                }
            }

            /* Notify and destroy */
            on_session_fail(sess, method, status, err_msg);
        }

    } else if (method == PJ_STUN_CHANNEL_BIND_METHOD) {
        /* Handle ChannelBind response */
        if (status==PJ_SUCCESS && 
            PJ_STUN_IS_SUCCESS_RESPONSE(response->hdr.type)) 
        {
            /* Successful ChannelBind response */
            struct ch_t *ch = (struct ch_t*)token;

            pj_assert(ch->num != PJ_TURN_INVALID_CHANNEL);
            ch->bound = PJ_TRUE;

            /* Update hash table */
            lookup_ch_by_addr(sess, &ch->addr,
                              pj_sockaddr_get_len(&ch->addr),
                              PJ_TRUE, PJ_TRUE);

        } else {
            /* Failed ChannelBind response */
            pj_str_t reason = {"", 0};
            int err_code = 0;
            char errbuf[PJ_ERR_MSG_SIZE];

            pj_assert(status != PJ_SUCCESS);

            if (response) {
                const pj_stun_errcode_attr *err_attr;
                err_attr = (const pj_stun_errcode_attr*)
                           pj_stun_msg_find_attr(response,
                                                 PJ_STUN_ATTR_ERROR_CODE, 0);
                if (err_attr) {
                    err_code = err_attr->err_code;
                    status = PJ_STATUS_FROM_STUN_CODE(err_attr->err_code);
                    reason = err_attr->reason;
                }
            } else {
                err_code = status;
                reason = pj_strerror(status, errbuf, sizeof(errbuf));
            }

            PJ_LOG(1,(sess->obj_name, "ChannelBind failed: %d/%.*s",
                      err_code, (int)reason.slen, reason.ptr));

            if (err_code == PJ_STUN_SC_ALLOCATION_MISMATCH) {
                /* Allocation mismatch means allocation no longer exists */
                on_session_fail(sess, PJ_STUN_CHANNEL_BIND_METHOD,
                                status, &reason);
                return;
            }
        }

    } else if (method == PJ_STUN_CREATE_PERM_METHOD) {
        /* Handle CreatePermission response */
        if (status==PJ_SUCCESS && 
            PJ_STUN_IS_SUCCESS_RESPONSE(response->hdr.type)) 
        {
            /* No special handling when the request is successful. */
        } else {
            /* Iterate the permission table and invalidate all permissions
             * that are related to this request.
             */
            pj_hash_iterator_t it_buf, *it;
            char ipstr[PJ_INET6_ADDRSTRLEN+10];
            int err_code;
            char errbuf[PJ_ERR_MSG_SIZE];
            pj_str_t reason;

            pj_assert(status != PJ_SUCCESS);

            if (response) {
                const pj_stun_errcode_attr *eattr;

                eattr = (const pj_stun_errcode_attr*)
                        pj_stun_msg_find_attr(response, 
                                              PJ_STUN_ATTR_ERROR_CODE, 0);
                if (eattr) {
                    err_code = eattr->err_code;
                    reason = eattr->reason;
                } else {
                    err_code = -1;
                    reason = pj_str("?");
                }
            } else {
                err_code = status;
                reason = pj_strerror(status, errbuf, sizeof(errbuf));
            }

            it = pj_hash_first(sess->perm_table, &it_buf);
            while (it) {
                struct perm_t *perm = (struct perm_t*)
                                      pj_hash_this(sess->perm_table, it);
                it = pj_hash_next(sess->perm_table, it);

                if (perm->req_token == token) {
                    PJ_LOG(1,(sess->obj_name, 
                              "CreatePermission failed for IP %s: %d/%.*s",
                              pj_sockaddr_print(&perm->addr, ipstr, 
                                                sizeof(ipstr), 2),
                              err_code, (int)reason.slen, reason.ptr));

                    invalidate_perm(sess, perm);
                }
            }

            if (err_code == PJ_STUN_SC_ALLOCATION_MISMATCH) {
                /* Allocation mismatch means allocation no longer exists */
                on_session_fail(sess, PJ_STUN_CREATE_PERM_METHOD,
                                status, &reason);
                return;
            }
        }

    } else if (method == PJ_STUN_CONNECTION_BIND_METHOD) {
        /* Handle ConnectionBind response */
        struct conn_bind_t *conn_bind = (struct conn_bind_t*)token;

        if (status != PJ_SUCCESS ||
            !PJ_STUN_IS_SUCCESS_RESPONSE(response->hdr.type)) 
        {
            pj_str_t reason = {0};
            if (status == PJ_SUCCESS) {
                const pj_stun_errcode_attr *err_attr;
                err_attr = (const pj_stun_errcode_attr*)
                           pj_stun_msg_find_attr(response,
                                                 PJ_STUN_ATTR_ERROR_CODE, 0);
                if (err_attr) {
                    status = PJ_STATUS_FROM_STUN_CODE(err_attr->err_code);
                    reason = err_attr->reason;
                } else {
                    status = PJNATH_EINSTUNMSG;
                }
            }
            pj_perror(1, sess->obj_name, status, "ConnectionBind failed: %.*s",
                      (int)reason.slen, reason.ptr);
        }

        /* Notify app */
        if (sess->cb.on_connection_bind_status) {
            (*sess->cb.on_connection_bind_status)
                        (sess, status, conn_bind->id,
                        &conn_bind->peer_addr, conn_bind->peer_addr_len);
        }
    } else if (method == PJ_STUN_CONNECT_METHOD) {
        /* Handle Connct response */
        struct pj_sockaddr_t *peer_addr = (struct pj_sockaddr_t*)token;
        pj_uint32_t conn_id = 0;

        if (status != PJ_SUCCESS ||
            !PJ_STUN_IS_SUCCESS_RESPONSE(response->hdr.type))
        {
            pj_str_t reason = {0};
            if (status == PJ_SUCCESS) {
                const pj_stun_errcode_attr *err_attr;
                err_attr = (const pj_stun_errcode_attr*)
                           pj_stun_msg_find_attr(response,
                                                 PJ_STUN_ATTR_ERROR_CODE, 0);
                if (err_attr) {
                    status = PJ_STATUS_FROM_STUN_CODE(err_attr->err_code);
                    reason = err_attr->reason;
                } else {
                    status = PJNATH_EINSTUNMSG;
                }
            }
            pj_perror(1, sess->obj_name, status, "Connect failed: %.*s",
                      (int)reason.slen, reason.ptr);
        } else {
            const pj_stun_uint_attr *conn_id_attr;
            conn_id_attr = (const pj_stun_uint_attr*)
            pj_stun_msg_find_attr(response, PJ_STUN_ATTR_CONNECTION_ID, 0);
            if (conn_id_attr == NULL) {
                status = PJNATH_EINSTUNMSG;
                pj_perror(1, sess->obj_name, status,
                          "Error: Missing CONNECTION-ID attribute");
            }
            else {
                conn_id = conn_id_attr->value;
            }
        }

        /* Notify app */
        if (sess->cb.on_connect_complete) {
            (*sess->cb.on_connect_complete)
                        (sess, status, conn_id,
                        peer_addr, pj_sockaddr_get_len(peer_addr));
        }
    } else {
        PJ_LOG(4,(sess->obj_name, "Unexpected STUN %s response",
                  pj_stun_get_method_name(response->hdr.type)));
    }
}


/*
 * Notification from STUN session on incoming STUN Indication
 * message.
 */
static pj_status_t stun_on_rx_indication(pj_stun_session *stun,
                                         const pj_uint8_t *pkt,
                                         unsigned pkt_len,
                                         const pj_stun_msg *msg,
                                         void *token,
                                         const pj_sockaddr_t *src_addr,
                                         unsigned src_addr_len)
{
    pj_turn_session *sess;
    pj_stun_xor_peer_addr_attr *peer_attr;
    pj_stun_icmp_attr *icmp;
    pj_stun_data_attr *data_attr;

    PJ_UNUSED_ARG(token);
    PJ_UNUSED_ARG(pkt);
    PJ_UNUSED_ARG(pkt_len);
    PJ_UNUSED_ARG(src_addr);
    PJ_UNUSED_ARG(src_addr_len);

    sess = (pj_turn_session*)pj_stun_session_get_user_data(stun);

    /* ConnectionAttempt Indication */
    if (msg->hdr.type == PJ_STUN_CONNECTION_ATTEMPT_INDICATION) {
        pj_stun_uint_attr *connection_id_attr;

        /* Get CONNECTION-ID attribute */
        connection_id_attr = (pj_stun_uint_attr*)
            pj_stun_msg_find_attr(msg, PJ_STUN_ATTR_CONNECTION_ID, 0);

        /* Get XOR-PEER-ADDRESS attribute */
        peer_attr = (pj_stun_xor_peer_addr_attr*)
            pj_stun_msg_find_attr(msg, PJ_STUN_ATTR_XOR_PEER_ADDR, 0);

        /* Must have both XOR-PEER-ADDRESS and CONNECTION-ID attributes */
        if (!peer_attr || !connection_id_attr) {
            PJ_LOG(4,(sess->obj_name, 
                      "Received ConnectionAttempt indication with missing "
                      "attributes"));
            return PJ_EINVALIDOP;
        }

        /* Notify application */
        if (sess->cb.on_connection_attempt) {
            (*sess->cb.on_connection_attempt)
                                (sess,
                                connection_id_attr->value,
                                &peer_attr->sockaddr,
                                pj_sockaddr_get_len(&peer_attr->sockaddr));
        }
        return PJ_SUCCESS;
    }

    /* Next, expecting Data Indication only */
    if (msg->hdr.type != PJ_STUN_DATA_INDICATION) {
        PJ_LOG(4,(sess->obj_name, "Unexpected STUN %s indication",
                  pj_stun_get_method_name(msg->hdr.type)));
        return PJ_EINVALIDOP;
    }

    /* Check if there is ICMP attribute in the message */
    icmp = (pj_stun_icmp_attr*)
           pj_stun_msg_find_attr(msg, PJ_STUN_ATTR_ICMP, 0);
    if (icmp != NULL) {
        /* This is a forwarded ICMP packet. Ignore it for now */
        return PJ_SUCCESS;
    }

    /* Get XOR-PEER-ADDRESS attribute */
    peer_attr = (pj_stun_xor_peer_addr_attr*)
                pj_stun_msg_find_attr(msg, PJ_STUN_ATTR_XOR_PEER_ADDR, 0);

    /* Get DATA attribute */
    data_attr = (pj_stun_data_attr*)
                pj_stun_msg_find_attr(msg, PJ_STUN_ATTR_DATA, 0);

    /* Must have both XOR-PEER-ADDRESS and DATA attributes */
    if (!peer_attr || !data_attr) {
        PJ_LOG(4,(sess->obj_name, 
                  "Received Data indication with missing attributes"));
        return PJ_EINVALIDOP;
    }

    /* Notify application */
    if (sess->cb.on_rx_data) {
        (*sess->cb.on_rx_data)(sess, data_attr->data, data_attr->length, 
                               &peer_attr->sockaddr,
                               pj_sockaddr_get_len(&peer_attr->sockaddr));
    }

    return PJ_SUCCESS;
}


/*
 * Notification on completion of DNS SRV resolution.
 */
static void dns_srv_resolver_cb(void *user_data,
                                pj_status_t status,
                                const pj_dns_srv_record *rec)
{
    pj_turn_session *sess = (pj_turn_session*) user_data;
    unsigned i, cnt, tot_cnt;

    /* Check failure */
    if (status != PJ_SUCCESS || sess->pending_destroy) {
        set_state(sess, PJ_TURN_STATE_DESTROYING);
        sess_shutdown(sess, status);
        pj_grp_lock_dec_ref(sess->grp_lock);
        return;
    }

    /* Calculate total number of server entries in the response */
    tot_cnt = 0;
    for (i=0; i<rec->count; ++i) {
        tot_cnt += rec->entry[i].server.addr_count;
    }

    if (tot_cnt > PJ_TURN_MAX_DNS_SRV_CNT)
        tot_cnt = PJ_TURN_MAX_DNS_SRV_CNT;

    /* Allocate server entries */
    sess->srv_addr_list = (pj_sockaddr*)
                           pj_pool_calloc(sess->pool, tot_cnt, 
                                          sizeof(pj_sockaddr));

    /* Copy results to server entries */
    for (i=0, cnt=0; i<rec->count && cnt<PJ_TURN_MAX_DNS_SRV_CNT; ++i) {
        unsigned j;

        for (j=0; j<rec->entry[i].server.addr_count && 
                  cnt<PJ_TURN_MAX_DNS_SRV_CNT; ++j) 
        {
            if (rec->entry[i].server.addr[j].af == sess->af) {
                pj_sockaddr *addr = &sess->srv_addr_list[cnt];

                addr->addr.sa_family = sess->af;
                pj_sockaddr_set_port(addr, rec->entry[i].port);
                if (sess->af == pj_AF_INET6())
                    addr->ipv6.sin6_addr = rec->entry[i].server.addr[j].ip.v6;
                else
                    addr->ipv4.sin_addr = rec->entry[i].server.addr[j].ip.v4;

                ++cnt;
            }
        }
    }
    sess->srv_addr_cnt = (pj_uint16_t)cnt;

    /* Set current server */
    sess->srv_addr = &sess->srv_addr_list[0];

    /* Set state to PJ_TURN_STATE_RESOLVED */
    set_state(sess, PJ_TURN_STATE_RESOLVED);

    /* Run pending allocation */
    if (sess->pending_alloc) {
        pj_status_t status2;
        status2 = pj_turn_session_alloc(sess, NULL);
        if (status2 != PJ_SUCCESS)
            on_session_fail(sess, PJ_STUN_ALLOCATE_METHOD, status2, NULL);
    }

    pj_grp_lock_dec_ref(sess->grp_lock);
}


/*
 * Lookup peer descriptor from its address.
 */
static struct ch_t *lookup_ch_by_addr(pj_turn_session *sess,
                                      const pj_sockaddr_t *addr,
                                      unsigned addr_len,
                                      pj_bool_t update,
                                      pj_bool_t bind_channel)
{
    pj_uint32_t hval = 0;
    struct ch_t *ch;

    ch = (struct ch_t*) 
         pj_hash_get(sess->ch_table, addr, addr_len, &hval);
    if (ch == NULL && update) {
        ch = PJ_POOL_ZALLOC_T(sess->pool, struct ch_t);
        ch->num = PJ_TURN_INVALID_CHANNEL;
        pj_memcpy(&ch->addr, addr, addr_len);

        /* Register by peer address */
        pj_hash_set(sess->pool, sess->ch_table, &ch->addr, addr_len,
                    hval, ch);
    }

    if (ch && update) {
        pj_gettimeofday(&ch->expiry);
        ch->expiry.sec += PJ_TURN_PERM_TIMEOUT - sess->ka_interval - 1;

        if (bind_channel) {
            pj_uint32_t hval2 = 0;
            /* Register by channel number */
            pj_assert(ch->num != PJ_TURN_INVALID_CHANNEL && ch->bound);

            if (pj_hash_get(sess->ch_table, &ch->num, 
                            sizeof(ch->num), &hval2)==0) {
                pj_hash_set(sess->pool, sess->ch_table, &ch->num,
                            sizeof(ch->num), hval2, ch);
            }
        }
    }

    /* Also create/update permission for this destination. Ideally we
     * should update this when we receive the successful response,
     * but that would cause duplicate CreatePermission to be sent
     * during refreshing.
     */
    if (ch && update) {
        lookup_perm(sess, &ch->addr, pj_sockaddr_get_len(&ch->addr), PJ_TRUE);
    }

    return ch;
}


/*
 * Lookup channel descriptor from its channel number.
 */
static struct ch_t *lookup_ch_by_chnum(pj_turn_session *sess,
                                         pj_uint16_t chnum)
{
    return (struct ch_t*) pj_hash_get(sess->ch_table, &chnum, 
                                      sizeof(chnum), NULL);
}


/*
 * Lookup permission and optionally create if it doesn't exist.
 */
static struct perm_t *lookup_perm(pj_turn_session *sess,
                                  const pj_sockaddr_t *addr,
                                  unsigned addr_len,
                                  pj_bool_t update)
{
    pj_uint32_t hval = 0;
    pj_sockaddr perm_addr;
    struct perm_t *perm;

    /* make sure port number if zero */
    if (pj_sockaddr_get_port(addr) != 0) {
        pj_memcpy(&perm_addr, addr, addr_len);
        pj_sockaddr_set_port(&perm_addr, 0);
        addr = &perm_addr;
    }

    /* lookup and create if it doesn't exist and wanted */
    perm = (struct perm_t*) 
           pj_hash_get(sess->perm_table, addr, addr_len, &hval);
    if (perm == NULL && update) {
        perm = PJ_POOL_ZALLOC_T(sess->pool, struct perm_t);
        pj_memcpy(&perm->addr, addr, addr_len);
        perm->hval = hval;

        pj_hash_set(sess->pool, sess->perm_table, &perm->addr, addr_len,
                    perm->hval, perm);
    }

    if (perm && update) {
        pj_gettimeofday(&perm->expiry);
        perm->expiry.sec += PJ_TURN_PERM_TIMEOUT - sess->ka_interval - 1;

    }

    return perm;
}

/*
 * Delete permission
 */
static void invalidate_perm(pj_turn_session *sess,
                            struct perm_t *perm)
{
    pj_hash_set(NULL, sess->perm_table, &perm->addr,
                pj_sockaddr_get_len(&perm->addr), perm->hval, NULL);
}

/*
 * Scan permission's hash table to refresh the permission.
 */
static unsigned refresh_permissions(pj_turn_session *sess, 
                                    const pj_time_val *now)
{
    pj_stun_tx_data *tdata = NULL;
    unsigned count = 0;
    void *req_token = NULL;
    pj_hash_iterator_t *it, itbuf;
    pj_status_t status;

    it = pj_hash_first(sess->perm_table, &itbuf);
    while (it) {
        struct perm_t *perm = (struct perm_t*)
                              pj_hash_this(sess->perm_table, it);

        it = pj_hash_next(sess->perm_table, it);

        if (perm->expiry.sec-1 <= now->sec) {
            if (perm->renew) {
                /* Renew this permission */
                if (tdata == NULL) {
                    /* Create a bare CreatePermission request */
                    status = pj_stun_session_create_req(
                                        sess->stun, 
                                        PJ_STUN_CREATE_PERM_REQUEST,
                                        PJ_STUN_MAGIC, NULL, &tdata);
                    if (status != PJ_SUCCESS) {
                        PJ_PERROR(1,(sess->obj_name, status,
                                  "Error creating CreatePermission request"));
                        return 0;
                    }

                    /* Create request token to map the request to the perm
                     * structures which the request belongs.
                     */
                    req_token = (void*)(pj_ssize_t)pj_rand();
                }

                status = pj_stun_msg_add_sockaddr_attr(
                                        tdata->pool, 
                                        tdata->msg,
                                        PJ_STUN_ATTR_XOR_PEER_ADDR,
                                        PJ_TRUE,
                                        &perm->addr,
                                        sizeof(perm->addr));
                if (status != PJ_SUCCESS) {
                    pj_stun_msg_destroy_tdata(sess->stun, tdata);
                    return 0;
                }

                perm->expiry = *now;
                perm->expiry.sec += PJ_TURN_PERM_TIMEOUT-sess->ka_interval-1;
                perm->req_token = req_token;
                ++count;

            } else {
                /* This permission has expired and app doesn't want
                 * us to renew, so delete it from the hash table.
                 */
                invalidate_perm(sess, perm);
            }
        }
    }

    if (tdata) {
        status = pj_stun_session_send_msg(sess->stun, req_token, PJ_FALSE, 
                                          (sess->conn_type==PJ_TURN_TP_UDP),
                                          sess->srv_addr,
                                          pj_sockaddr_get_len(sess->srv_addr), 
                                          tdata);
        if (status != PJ_SUCCESS) {
            PJ_PERROR(1,(sess->obj_name, status,
                      "Error sending CreatePermission request"));
            count = 0;
        }

    }

    return count;
}

/*
 * Timer event.
 */
static void on_timer_event(pj_timer_heap_t *th, pj_timer_entry *e)
{
    pj_turn_session *sess = (pj_turn_session*)e->user_data;
    enum timer_id_t eid;

    PJ_UNUSED_ARG(th);

    pj_grp_lock_acquire(sess->grp_lock);

    eid = (enum timer_id_t) e->id;
    e->id = TIMER_NONE;
    
    if (eid == TIMER_KEEP_ALIVE) {
        pj_time_val now;
        pj_hash_iterator_t itbuf, *it;
        pj_bool_t resched = PJ_TRUE;
        pj_bool_t pkt_sent = PJ_FALSE;

        if (sess->state >= PJ_TURN_STATE_DEALLOCATING) {
            /* Ignore if we're deallocating */
            goto on_return;
        }

        pj_gettimeofday(&now);

        /* Refresh allocation if it's time to do so */
        if (PJ_TIME_VAL_LTE(sess->expiry, now)) {
            int lifetime = sess->alloc_param.lifetime;

            if (lifetime == 0)
                lifetime = -1;

            send_refresh(sess, lifetime);
            resched = PJ_FALSE;
            pkt_sent = PJ_TRUE;
        }

        /* Scan hash table to refresh bound channels */
        it = pj_hash_first(sess->ch_table, &itbuf);
        while (it) {
            struct ch_t *ch = (struct ch_t*) 
                              pj_hash_this(sess->ch_table, it);
            if (ch->bound && PJ_TIME_VAL_LTE(ch->expiry, now)) {

                /* Send ChannelBind to refresh channel binding and 
                 * permission.
                 */
                pj_turn_session_bind_channel(sess, &ch->addr,
                                             pj_sockaddr_get_len(&ch->addr));
                pkt_sent = PJ_TRUE;
            }

            it = pj_hash_next(sess->ch_table, it);
        }

        /* Scan permission table to refresh permissions */
        if (refresh_permissions(sess, &now))
            pkt_sent = PJ_TRUE;

        /* If no packet is sent, send a blank Send indication to
         * refresh local NAT.
         */
        if (!pkt_sent && sess->alloc_param.ka_interval > 0) {
            pj_stun_tx_data *tdata;
            pj_status_t rc;

            /* Create blank SEND-INDICATION */
            rc = pj_stun_session_create_ind(sess->stun, 
                                            PJ_STUN_SEND_INDICATION, &tdata);
            if (rc == PJ_SUCCESS) {
                /* Add DATA attribute with zero length */
                pj_stun_msg_add_binary_attr(tdata->pool, tdata->msg,
                                            PJ_STUN_ATTR_DATA, NULL, 0);

                /* Send the indication */
                pj_stun_session_send_msg(sess->stun, NULL, PJ_FALSE, 
                                         PJ_FALSE, sess->srv_addr,
                                         pj_sockaddr_get_len(sess->srv_addr),
                                         tdata);
            }
        }

        /* Reshcedule timer */
        if (resched) {
            pj_time_val delay;

            delay.sec = sess->ka_interval;
            delay.msec = 0;

            pj_timer_heap_schedule_w_grp_lock(sess->timer_heap, &sess->timer,
                                              &delay, TIMER_KEEP_ALIVE,
                                              sess->grp_lock);
        }

    } else if (eid == TIMER_DESTROY) {
        /* Time to destroy */
        do_destroy(sess);
    } else {
        pj_assert(!"Unknown timer event");
    }

on_return:
    pj_grp_lock_release(sess->grp_lock);
}

