/* $Id: turn_session.c 4368 2013-02-21 21:53:28Z bennylp $ */
/* 
 * 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;
};


/* 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));
}

/*
 * 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;

    /* 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_pool_t *pool = sess->pool;

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

	sess->pool = NULL;
	pj_pool_release(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://trac.pjsip.org/repos/ticket/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)
{
    PJ_ASSERT_RETURN(sess, PJ_EINVAL);

    pj_grp_lock_acquire(sess->grp_lock);

    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;
	}

	/* Fallback to DNS A only if default port is specified */
	if (default_port>0 && default_port<65536) {
	    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;
	}

	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);
	    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;
	    addr->ipv4.sin_port = pj_htons(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_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(PJ_TURN_TP_UDP));

    /* 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);
    }

    /* 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(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;
	}
    }

    pj_assert(attr_added != 0);

    /* 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;
	}
    }

    /* 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;
}


/**
 * 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_pkt(pj_turn_session *sess,
					      void *pkt,
					      pj_size_t pkt_len,
					      pj_size_t *parsed_len)
{
    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*)pkt)[0] & 0xC0) == 0);

    if (is_stun) {
	/* This looks like STUN, give it to the STUN session */
	unsigned options;

	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, pkt, pkt_len,
					 options, NULL, parsed_len,
					 sess->srv_addr,
					 pj_sockaddr_get_len(sess->srv_addr));

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

	if (pkt_len < 4) {
	    if (parsed_len) *parsed_len = 0;
	    return PJ_ETOOSMALL;
	}

	/* Decode ChannelData packet */
	pj_memcpy(&cd, 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 (pkt_len < cd.length+sizeof(cd)) {
	    if (parsed_len) {
		if (is_datagram) {
		    /* Discard the datagram */
		    *parsed_len = pkt_len;
		} else {
		    /* Insufficient fragment */
		    *parsed_len = 0;
		}
	    }
	    status = PJ_ETOOSMALL;
	    goto on_return;
	} else {
	    if (parsed_len) {
		/* Apply padding too */
		*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*)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);
    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 && raddr_attr->sockaddr.addr.sa_family != sess->af) {
	on_session_fail(sess, method, PJNATH_EINSTUNMSG,
			pj_cstr(&s, "Error: RELAY-ADDRESS with non IPv4"
				    " address family is not supported "
				    "for now"));
	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 {
	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);

    /* 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);
	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) 
	{
	    pj_sockaddr_in *addr = &sess->srv_addr_list[cnt].ipv4;

	    addr->sin_family = sess->af;
	    addr->sin_port = pj_htons(rec->entry[i].port);
	    addr->sin_addr.s_addr = rec->entry[i].server.addr[j].s_addr;

	    ++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_turn_session_alloc(sess, NULL);
    }
}


/*
 * 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_LOG(1,(sess->obj_name, 
				 "Error creating CreatePermission request: %d",
				 status));
			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_LOG(1,(sess->obj_name, 
		      "Error sending CreatePermission request: %d",
		      status));
	    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);
}

