Wed Aug 20 06:36:40 2008

Asterisk developer's documentation

---

chan_h323.c

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/*
 * Asterisk -- An open source telephony toolkit.
 *
 * Copyright (C) 1999 - 2005
 *
 * OpenH323 Channel Driver for ASTERISK PBX.
 *       By Jeremy McNamara
 *                      For The NuFone Network 
 *
 * chan_h323 has been derived from code created by
 *               Michael Manousos and Mark Spencer
 *
 * See http://www.asterisk.org for more information about
 * the Asterisk project. Please do not directly contact
 * any of the maintainers of this project for assistance;
 * the project provides a web site, mailing lists and IRC
 * channels for your use.
 *
 * This program is free software, distributed under the terms of
 * the GNU General Public License Version 2. See the LICENSE file
 * at the top of the source tree.
 */

/*! \file
 *
 * \brief This file is part of the chan_h323 driver for Asterisk
 *
 * \par See also
 * \arg Config_h323
 *
 * \ingroup channel_drivers
 */

#include <sys/socket.h>
#include <sys/signal.h>
#include <sys/param.h>
#if defined(BSD)
#ifndef IPTOS_MINCOST
#define IPTOS_MINCOST 0x02
#endif
#endif
#include <arpa/inet.h>
#include <net/if.h>
#include <netinet/in.h>
#include <netinet/in_systm.h>
#include <netinet/ip.h>
#include <unistd.h>
#include <stdlib.h>
#include <netdb.h>
#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <fcntl.h>
#ifdef __cplusplus
extern "C" {
#endif   

#include "asterisk.h"

ASTERISK_FILE_VERSION(__FILE__, "$Revision: 53045 $")

#include "asterisk/lock.h"
#include "asterisk/logger.h"
#include "asterisk/channel.h"
#include "asterisk/config.h"
#include "asterisk/module.h"
#include "asterisk/pbx.h"
#include "asterisk/options.h"
#include "asterisk/utils.h"
#include "asterisk/lock.h"
#include "asterisk/sched.h"
#include "asterisk/io.h"
#include "asterisk/rtp.h"
#include "asterisk/acl.h"
#include "asterisk/callerid.h"
#include "asterisk/cli.h"
#include "asterisk/dsp.h"
#include "asterisk/causes.h"
#ifdef __cplusplus
}
#endif
#include "h323/chan_h323.h"

send_digit_cb on_send_digit; 
on_rtp_cb on_external_rtp_create; 
start_rtp_cb on_start_rtp_channel; 
setup_incoming_cb on_incoming_call;
setup_outbound_cb on_outgoing_call; 
chan_ringing_cb   on_chan_ringing;
con_established_cb on_connection_established;
clear_con_cb on_connection_cleared;
answer_call_cb on_answer_call;
progress_cb on_progress;
rfc2833_cb on_set_rfc2833_payload;
hangup_cb on_hangup;
setcapabilities_cb on_setcapabilities;

/* global debug flag */
int h323debug;

/** Variables required by Asterisk */
static const char type[] = "H323";
static const char desc[] = "The NuFone Network's Open H.323 Channel Driver";
static const char tdesc[] = "The NuFone Network's Open H.323 Channel Driver";
static const char config[] = "h323.conf";
static char default_context[AST_MAX_CONTEXT] = "default";
static struct sockaddr_in bindaddr;

/** H.323 configuration values */
static int h323_signalling_port = 1720;
static char gatekeeper[100];
static int gatekeeper_disable = 1;
static int gatekeeper_discover = 0;
static int usingGk = 0;
static int gkroute = 0;
/* Find user by alias (h.323 id) is default, alternative is the incomming call's source IP address*/
static int userbyalias = 1;
static int tos = 0;
static char secret[50];
static unsigned int unique = 0;

static call_options_t global_options;

/** Private structure of a OpenH323 channel */
struct oh323_pvt {
   ast_mutex_t lock;             /* Channel private lock */
   call_options_t options;             /* Options to be used during call setup */
   int alreadygone;              /* Whether or not we've already been destroyed by our peer */
   int needdestroy;              /* if we need to be destroyed */
   call_details_t cd;               /* Call details */
   struct ast_channel *owner;          /* Who owns us */
   struct sockaddr_in sa;                       /* Our peer */
   struct sockaddr_in redirip;                 /* Where our RTP should be going if not to us */
   int nonCodecCapability;             /* non-audio capability */
   int outgoing;                 /* Outgoing or incoming call? */
   char exten[AST_MAX_EXTENSION];            /* Requested extension */
   char context[AST_MAX_CONTEXT];            /* Context where to start */
   char accountcode[256];              /* Account code */
   char cid_num[80];             /* Caller*id number, if available */
   char cid_name[80];               /* Caller*id name, if available */
   char rdnis[80];                  /* Referring DNIS, if available */
   int amaflags;                 /* AMA Flags */
   struct ast_rtp *rtp;             /* RTP Session */
   struct ast_dsp *vad;             /* Used for in-band DTMF detection */
   int nativeformats;               /* Codec formats supported by a channel */
   int needhangup;                  /* Send hangup when Asterisk is ready */
   int hangupcause;              /* Hangup cause from OpenH323 layer */
   int newstate;                 /* Pending state change */
   int newcontrol;                  /* Pending control to send */
   struct oh323_pvt *next;          /* Next channel in list */
} *iflist = NULL;

static struct ast_user_list {
   struct oh323_user *users;
   ast_mutex_t lock;
} userl;

static struct ast_peer_list {
   struct oh323_peer *peers;
   ast_mutex_t lock;
} peerl;

static struct ast_alias_list {
   struct oh323_alias *aliases;
   ast_mutex_t lock;
} aliasl;

/** Asterisk RTP stuff */
static struct sched_context *sched;
static struct io_context *io;

/** Protect the interface list (oh323_pvt) */
AST_MUTEX_DEFINE_STATIC(iflock);

/** Usage counter and associated lock */
static int usecnt = 0;
AST_MUTEX_DEFINE_STATIC(usecnt_lock);

/* Protect the monitoring thread, so only one process can kill or start it, and not
   when it's doing something critical. */
AST_MUTEX_DEFINE_STATIC(monlock);

/* Protect the H.323 capabilities list, to avoid more than one channel to set the capabilities simultaneaously in the h323 stack. */
AST_MUTEX_DEFINE_STATIC(caplock);

/* Protect the reload process */
AST_MUTEX_DEFINE_STATIC(h323_reload_lock);
static int h323_reloading = 0;

/* This is the thread for the monitor which checks for input on the channels
   which are not currently in use.  */
static pthread_t monitor_thread = AST_PTHREADT_NULL;
static int restart_monitor(void);
static int h323_do_reload(void);

static struct ast_channel *oh323_request(const char *type, int format, void *data, int *cause);
static int oh323_digit(struct ast_channel *c, char digit);
static int oh323_call(struct ast_channel *c, char *dest, int timeout);
static int oh323_hangup(struct ast_channel *c);
static int oh323_answer(struct ast_channel *c);
static struct ast_frame *oh323_read(struct ast_channel *c);
static int oh323_write(struct ast_channel *c, struct ast_frame *frame);
static int oh323_indicate(struct ast_channel *c, int condition);
static int oh323_fixup(struct ast_channel *oldchan, struct ast_channel *newchan);

static const struct ast_channel_tech oh323_tech = {
   .type = type,
   .description = tdesc,
   .capabilities = AST_FORMAT_ULAW,
   .properties = AST_CHAN_TP_WANTSJITTER,
   .requester = oh323_request,
   .send_digit = oh323_digit,
   .call = oh323_call,
   .hangup = oh323_hangup,
   .answer = oh323_answer,
   .read = oh323_read,
   .write = oh323_write,
   .indicate = oh323_indicate,
   .fixup = oh323_fixup,
   /* disable, for now */
#if 0
   .bridge = ast_rtp_bridge,
#endif
};

/* Channel and private structures should be already locked */
static void __oh323_update_info(struct ast_channel *c, struct oh323_pvt *pvt)
{
   if (c->nativeformats != pvt->nativeformats) {
      if (h323debug)
         ast_log(LOG_DEBUG, "Preparing %s for new native format\n", c->name);
      c->nativeformats = pvt->nativeformats;
      ast_set_read_format(c, c->readformat);
      ast_set_write_format(c, c->writeformat);
   }
   if (pvt->needhangup) {
      if (h323debug)
         ast_log(LOG_DEBUG, "Process pending hangup for %s\n", c->name);
      c->_softhangup |= AST_SOFTHANGUP_DEV;
      c->hangupcause = pvt->hangupcause;
      ast_queue_hangup(c);
      pvt->needhangup = 0;
      pvt->newstate = pvt->newcontrol = -1;
   }
   if (pvt->newstate >= 0) {
      ast_setstate(c, pvt->newstate);
      pvt->newstate = -1;
   }
   if (pvt->newcontrol >= 0) {
      ast_queue_control(c, pvt->newcontrol);
      pvt->newcontrol = -1;
   }
}

/* Only channel structure should be locked */
static void oh323_update_info(struct ast_channel *c)
{
   struct oh323_pvt *pvt = c->tech_pvt;

   if (pvt) {
      ast_mutex_lock(&pvt->lock);
      __oh323_update_info(c, pvt);
      ast_mutex_unlock(&pvt->lock);
   }
}

static void cleanup_call_details(call_details_t *cd) 
{
        if (cd->call_token) {
                free(cd->call_token);
                cd->call_token = NULL;
        }
        if (cd->call_source_aliases) {
                free(cd->call_source_aliases);
                cd->call_source_aliases = NULL;
        }
        if (cd->call_dest_alias) {
                free(cd->call_dest_alias);
                cd->call_dest_alias = NULL;
   }
        if (cd->call_source_name) { 
                free(cd->call_source_name);
                cd->call_source_name = NULL;
        }
        if (cd->call_source_e164) {
                free(cd->call_source_e164);
                cd->call_source_e164 = NULL;
        }
        if (cd->call_dest_e164) {
                free(cd->call_dest_e164);
                cd->call_dest_e164 = NULL;
        }
        if (cd->sourceIp) {
                free(cd->sourceIp);
                cd->sourceIp = NULL;
        }
}

static void __oh323_destroy(struct oh323_pvt *pvt)
{
   struct oh323_pvt *cur, *prev = NULL;
   
   if (pvt->rtp) {
      ast_rtp_destroy(pvt->rtp);
   }
   
   /* Free dsp used for in-band DTMF detection */
   if (pvt->vad) {
      ast_dsp_free(pvt->vad);
   }
   cleanup_call_details(&pvt->cd);

   /* Unlink us from the owner if we have one */
   if (pvt->owner) {
      ast_mutex_lock(&pvt->owner->lock);
      ast_log(LOG_DEBUG, "Detaching from %s\n", pvt->owner->name);
      pvt->owner->tech_pvt = NULL;
      ast_mutex_unlock(&pvt->owner->lock);
   }
   cur = iflist;
   while(cur) {
      if (cur == pvt) {
         if (prev)
            prev->next = cur->next;
         else
            iflist = cur->next;
         break;
      }
      prev = cur;
      cur = cur->next;
   }
   if (!cur) {
      ast_log(LOG_WARNING, "%p is not in list?!?! \n", cur);
   } else {
      ast_mutex_destroy(&pvt->lock);
      free(pvt);
   }
}

static void oh323_destroy(struct oh323_pvt *pvt)
{
   ast_mutex_lock(&iflock);
   __oh323_destroy(pvt);
   ast_mutex_unlock(&iflock);
}

/**
 * Send (play) the specified digit to the channel.
 * 
 */
static int oh323_digit(struct ast_channel *c, char digit)
{
   struct oh323_pvt *pvt = (struct oh323_pvt *) c->tech_pvt;
   char *token;

   if (!pvt) {
      ast_log(LOG_ERROR, "No private structure?! This is bad\n");
      return -1;
   }
   ast_mutex_lock(&pvt->lock);
   if (pvt->rtp && (pvt->options.dtmfmode & H323_DTMF_RFC2833)) {
      /* out-of-band DTMF */
      if (h323debug) {
         ast_log(LOG_DEBUG, "Sending out-of-band digit %c on %s\n", digit, c->name);
      }
      ast_rtp_senddigit(pvt->rtp, digit);
   } else {
      /* in-band DTMF */
      if (h323debug) {
         ast_log(LOG_DEBUG, "Sending inband digit %c on %s\n", digit, c->name);
      }
      token = pvt->cd.call_token ? strdup(pvt->cd.call_token) : NULL;
      h323_send_tone(token, digit);
      if (token) {
         free(token);
      }
   }
   ast_mutex_unlock(&pvt->lock);
   oh323_update_info(c);
   return 0;
}

/**
 * Make a call over the specified channel to the specified 
 * destination.
 * Returns -1 on error, 0 on success.
 */
static int oh323_call(struct ast_channel *c, char *dest, int timeout)
{  
   int res = 0;
   struct oh323_pvt *pvt = (struct oh323_pvt *)c->tech_pvt;
   char addr[INET_ADDRSTRLEN];
   char called_addr[1024];

   if (h323debug) {
      ast_log(LOG_DEBUG, "Calling to %s on %s\n", dest, c->name);
   }
   if ((c->_state != AST_STATE_DOWN) && (c->_state != AST_STATE_RESERVED)) {
      ast_log(LOG_WARNING, "Line is already in use (%s)\n", c->name);
      return -1;
   }
   ast_mutex_lock(&pvt->lock);
   if (usingGk) {
      if (ast_strlen_zero(pvt->exten)) {
         strncpy(called_addr, dest, sizeof(called_addr));
      } else {
         snprintf(called_addr, sizeof(called_addr), "%s@%s", pvt->exten, dest);
      }
   } else {
      ast_inet_ntoa(addr, sizeof(addr), pvt->sa.sin_addr);
      res = htons(pvt->sa.sin_port);
      if (ast_strlen_zero(pvt->exten)) {
         snprintf(called_addr, sizeof(called_addr), "%s:%d", addr, res);
      } else {
         snprintf(called_addr, sizeof(called_addr), "%s@%s:%d", pvt->exten, addr, res);
      }
   }
   /* make sure null terminated */
   called_addr[sizeof(called_addr) - 1] = '\0'; 

   if (c->cid.cid_num) {
      strncpy(pvt->options.cid_num, c->cid.cid_num, sizeof(pvt->options.cid_num));
   }
   if (c->cid.cid_name) {
      strncpy(pvt->options.cid_name, c->cid.cid_name, sizeof(pvt->options.cid_name));
   }

   /* indicate that this is an outgoing call */
   pvt->outgoing = 1;

   ast_log(LOG_DEBUG, "Placing outgoing call to %s, %d\n", called_addr, pvt->options.dtmfcodec);
   ast_mutex_unlock(&pvt->lock);
   res = h323_make_call(called_addr, &(pvt->cd), &pvt->options);
   if (res) {
      ast_log(LOG_NOTICE, "h323_make_call failed(%s)\n", c->name);
      return -1;
   }
   oh323_update_info(c);
   return 0;
}

static int oh323_answer(struct ast_channel *c)
{
   int res;
   struct oh323_pvt *pvt = (struct oh323_pvt *) c->tech_pvt;
   char *token;

   if (h323debug)
      ast_log(LOG_DEBUG, "Answering on %s\n", c->name);

   ast_mutex_lock(&pvt->lock);
   token = pvt->cd.call_token ? strdup(pvt->cd.call_token) : NULL;
   ast_mutex_unlock(&pvt->lock);
   res = h323_answering_call(token, 0);
   if (token)
      free(token);

   oh323_update_info(c);
   if (c->_state != AST_STATE_UP) {
      ast_setstate(c, AST_STATE_UP);
   }
   return res;
}

static int oh323_hangup(struct ast_channel *c)
{
   struct oh323_pvt *pvt = (struct oh323_pvt *) c->tech_pvt;
   int needcancel = 0;
   int q931cause = AST_CAUSE_NORMAL_CLEARING;
   char *call_token;


   if (h323debug)
      ast_log(LOG_DEBUG, "Hanging up call %s\n", c->name);

   if (!c->tech_pvt) {
      ast_log(LOG_DEBUG, "Asked to hangup channel not connected\n");
      return 0;
   }
   ast_mutex_lock(&pvt->lock);
   /* Determine how to disconnect */
   if (pvt->owner != c) {
      ast_log(LOG_WARNING, "Huh?  We aren't the owner?\n");
      ast_mutex_unlock(&pvt->lock);
      return 0;
   }
   if (!c || (c->_state != AST_STATE_UP)) {
      needcancel = 1;
   }
   
   pvt->owner = NULL;
   c->tech_pvt = NULL;

   if (c->hangupcause) {
      q931cause = c->hangupcause;
   } else {
      char *cause = pbx_builtin_getvar_helper(c, "DIALSTATUS");
      if (cause) {
         if (!strcmp(cause, "CONGESTION")) {
            q931cause = AST_CAUSE_NORMAL_CIRCUIT_CONGESTION;
         } else if (!strcmp(cause, "BUSY")) {
            q931cause = AST_CAUSE_USER_BUSY;
         } else if (!strcmp(cause, "CHANISUNVAIL")) {
            q931cause = AST_CAUSE_REQUESTED_CHAN_UNAVAIL;
         } else if (!strcmp(cause, "NOANSWER")) {
            q931cause = AST_CAUSE_NO_ANSWER;
         } else if (!strcmp(cause, "CANCEL")) {
            q931cause = AST_CAUSE_CALL_REJECTED;
         }
      }
   }

   /* Start the process if it's not already started */
   if (!pvt->alreadygone && !pvt->hangupcause) {
      call_token = pvt->cd.call_token ? strdup(pvt->cd.call_token) : NULL;
      if (call_token) {
         /* Release lock to eliminate deadlock */
         ast_mutex_unlock(&pvt->lock);
         if (h323_clear_call(call_token, q931cause)) { 
            ast_log(LOG_DEBUG, "ClearCall failed.\n");
         }
         free(call_token);
         ast_mutex_lock(&pvt->lock);
      }
   } 
   pvt->needdestroy = 1;

   /* Update usage counter */
   ast_mutex_lock(&usecnt_lock);
   usecnt--;
   if (usecnt < 0) {
      ast_log(LOG_WARNING, "Usecnt < 0\n");
   }
   ast_mutex_unlock(&usecnt_lock);
   ast_mutex_unlock(&pvt->lock);
   ast_update_use_count();
   return 0;
}

static struct ast_frame *oh323_rtp_read(struct oh323_pvt *pvt)
{
   /* Retrieve audio/etc from channel.  Assumes pvt->lock is already held. */
   struct ast_frame *f;
   static struct ast_frame null_frame = { AST_FRAME_NULL, };

   /* Only apply it for the first packet, we just need the correct ip/port */
   if (pvt->options.nat) {
      ast_rtp_setnat(pvt->rtp, pvt->options.nat);
      pvt->options.nat = 0;
   }

   f = ast_rtp_read(pvt->rtp);
   /* Don't send RFC2833 if we're not supposed to */
   if (f && (f->frametype == AST_FRAME_DTMF) && !(pvt->options.dtmfmode & H323_DTMF_RFC2833)) {
      return &null_frame;
   }
   if (pvt->owner) {
      /* We already hold the channel lock */
      if (f->frametype == AST_FRAME_VOICE) {
         if (f->subclass != pvt->owner->nativeformats) {
            /* Try to avoid deadlock */
            if (ast_mutex_trylock(&pvt->owner->lock)) {
               ast_log(LOG_NOTICE, "Format changed but channel is locked. Ignoring frame...\n");
               return &null_frame;
            }
            ast_log(LOG_DEBUG, "Oooh, format changed to %d\n", f->subclass);
            pvt->owner->nativeformats = f->subclass;
            pvt->nativeformats = f->subclass;
            ast_set_read_format(pvt->owner, pvt->owner->readformat);
            ast_set_write_format(pvt->owner, pvt->owner->writeformat);
            ast_mutex_unlock(&pvt->owner->lock);
         }  
         /* Do in-band DTMF detection */
         if ((pvt->options.dtmfmode & H323_DTMF_INBAND) && pvt->vad) {
            if (!ast_mutex_trylock(&pvt->owner->lock)) {
               f = ast_dsp_process(pvt->owner,pvt->vad,f);
               ast_mutex_unlock(&pvt->owner->lock);
            }
            else
               ast_log(LOG_NOTICE, "Unable to process inband DTMF while channel is locked\n");
            if (f &&(f->frametype == AST_FRAME_DTMF)) {
               ast_log(LOG_DEBUG, "Received in-band digit %c.\n", f->subclass);
            }
         }
      }
   }
   return f;
}

static struct ast_frame *oh323_read(struct ast_channel *c)
{
   struct ast_frame *fr;
   struct oh323_pvt *pvt = (struct oh323_pvt *)c->tech_pvt;
   ast_mutex_lock(&pvt->lock);
   __oh323_update_info(c, pvt);
   fr = oh323_rtp_read(pvt);
   ast_mutex_unlock(&pvt->lock);
   return fr;
}

static int oh323_write(struct ast_channel *c, struct ast_frame *frame)
{
   struct oh323_pvt *pvt = (struct oh323_pvt *) c->tech_pvt;
   int res = 0;
   if (frame->frametype != AST_FRAME_VOICE) {
      if (frame->frametype == AST_FRAME_IMAGE) {
         return 0;
      } else {
         ast_log(LOG_WARNING, "Can't send %d type frames with H323 write\n", frame->frametype);
         return 0;
      }
   } else {
      if (!(frame->subclass & c->nativeformats)) {
         ast_log(LOG_WARNING, "Asked to transmit frame type %d, while native formats is %d (read/write = %d/%d)\n",
            frame->subclass, c->nativeformats, c->readformat, c->writeformat);
         return 0;
      }
   }
   if (pvt) {
      ast_mutex_lock(&pvt->lock);
      if (pvt->rtp) {
         res =  ast_rtp_write(pvt->rtp, frame);
      }
      __oh323_update_info(c, pvt);
      ast_mutex_unlock(&pvt->lock);
   }
   return res;
}

static int oh323_indicate(struct ast_channel *c, int condition)
{

   struct oh323_pvt *pvt = (struct oh323_pvt *) c->tech_pvt;
   char *token = (char *)NULL;

   ast_mutex_lock(&pvt->lock);
   token = (pvt->cd.call_token ? strdup(pvt->cd.call_token) : NULL);
   ast_mutex_unlock(&pvt->lock);

   if (h323debug)
      ast_log(LOG_DEBUG, "OH323: Indicating %d on %s\n", condition, token);

   switch(condition) {
   case AST_CONTROL_RINGING:
      if (c->_state == AST_STATE_RING || c->_state == AST_STATE_RINGING) {
         h323_send_alerting(token);
         break;
      }
      if (token)
         free(token);
      return -1;
   case AST_CONTROL_PROGRESS:
      if (c->_state != AST_STATE_UP) {
         h323_send_progress(token);
         break;
      }
      if (token)
         free(token);
      return -1;

   case AST_CONTROL_BUSY:
      if (c->_state != AST_STATE_UP) {
         h323_answering_call(token, 1);
         ast_mutex_lock(&pvt->lock);
         pvt->alreadygone = 1;
         ast_mutex_unlock(&pvt->lock);
         ast_softhangup_nolock(c, AST_SOFTHANGUP_DEV);         
         break;
      }
      if (token)
         free(token);
      return -1;
   case AST_CONTROL_CONGESTION:
      if (c->_state != AST_STATE_UP) {
         h323_answering_call(token, 1);
         ast_mutex_lock(&pvt->lock);
         pvt->alreadygone = 1;
         ast_mutex_unlock(&pvt->lock);
         ast_softhangup_nolock(c, AST_SOFTHANGUP_DEV);
         break;
      }
      if (token)
         free(token);
      return -1;
   case AST_CONTROL_PROCEEDING:
   case -1:
      if (token)
         free(token);
      return -1;
   default:
      ast_log(LOG_WARNING, "Don't know how to indicate condition %d on %s\n", condition, token);
      if (token)
         free(token);
      return -1;
   }

   if (h323debug)
      ast_log(LOG_DEBUG, "OH323: Indicated %d on %s\n", condition, token);
   if (token)
      free(token);
   oh323_update_info(c);

   return -1;
}

static int oh323_fixup(struct ast_channel *oldchan, struct ast_channel *newchan)
{
   struct oh323_pvt *pvt = (struct oh323_pvt *) newchan->tech_pvt;

   ast_mutex_lock(&pvt->lock);
   if (pvt->owner != oldchan) {
      ast_log(LOG_WARNING, "old channel wasn't %p but was %p\n", oldchan, pvt->owner);
      return -1;
   }
   pvt->owner = newchan;
   ast_mutex_unlock(&pvt->lock);
   return 0;
}

/* Private structure should be locked on a call */
static struct ast_channel *__oh323_new(struct oh323_pvt *pvt, int state, const char *host)
{
   struct ast_channel *ch;
   int fmt;
   
   /* Don't hold a oh323_pvt lock while we allocate a chanel */
   ast_mutex_unlock(&pvt->lock);
   ch = ast_channel_alloc(1);
   /* Update usage counter */
   ast_mutex_lock(&usecnt_lock);
   usecnt++;
   ast_mutex_unlock(&usecnt_lock);
   ast_update_use_count();
   ast_mutex_lock(&pvt->lock);
   if (ch) {
      ch->tech = &oh323_tech;
      snprintf(ch->name, sizeof(ch->name), "H323/%s", host);
      ch->nativeformats = pvt->options.capability;
      if (!ch->nativeformats) {
         ch->nativeformats = global_options.capability;
      }
      pvt->nativeformats = ch->nativeformats;
      fmt = ast_best_codec(ch->nativeformats);
      ch->type = type;
      ch->fds[0] = ast_rtp_fd(pvt->rtp);
      if (state == AST_STATE_RING) {
         ch->rings = 1;
      }
      ch->writeformat = fmt;
      ch->rawwriteformat = fmt;
      ch->readformat = fmt;
      ch->rawreadformat = fmt;
      /* Allocate dsp for in-band DTMF support */
      if (pvt->options.dtmfmode & H323_DTMF_INBAND) {
         pvt->vad = ast_dsp_new();
         ast_dsp_set_features(pvt->vad, DSP_FEATURE_DTMF_DETECT);
         }
      /* Register channel functions. */
      ch->tech_pvt = pvt;
      /*  Set the owner of this channel */
      pvt->owner = ch;
      
      strncpy(ch->context, pvt->context, sizeof(ch->context) - 1);
      strncpy(ch->exten, pvt->exten, sizeof(ch->exten) - 1);      
      ch->priority = 1;
      if (!ast_strlen_zero(pvt->accountcode)) {
         strncpy(ch->accountcode, pvt->accountcode, sizeof(ch->accountcode) - 1);
      }
      if (pvt->amaflags) {
         ch->amaflags = pvt->amaflags;
      }

      if (!ast_strlen_zero(pvt->cid_num))
         ch->cid.cid_num = strdup(pvt->cid_num);
      else if (!ast_strlen_zero(pvt->cd.call_source_e164))
         ch->cid.cid_num = strdup(pvt->cd.call_source_e164);
      if (!ast_strlen_zero(pvt->cid_name))
         ch->cid.cid_name = strdup(pvt->cid_name);

      if (!ast_strlen_zero(pvt->rdnis)) {
         ch->cid.cid_rdnis = strdup(pvt->rdnis);
      }
      if (!ast_strlen_zero(pvt->exten) && strcmp(pvt->exten, "s")) {
         ch->cid.cid_dnid = strdup(pvt->exten);
      }
      ast_setstate(ch, state);
      if (state != AST_STATE_DOWN) {
         if (ast_pbx_start(ch)) {
            ast_log(LOG_WARNING, "Unable to start PBX on %s\n", ch->name);
            ast_hangup(ch);
            ch = NULL;
         }
      }
   } else  {
      ast_log(LOG_WARNING, "Unable to allocate channel structure\n");
   }
   return ch;
}

static struct oh323_pvt *oh323_alloc(int callid)
{
   struct oh323_pvt *pvt;

   pvt = (struct oh323_pvt *) malloc(sizeof(struct oh323_pvt));
   if (!pvt) {
      ast_log(LOG_ERROR, "Couldn't allocate private structure. This is bad\n");
      return NULL;
   }
   memset(pvt, 0, sizeof(struct oh323_pvt));
   pvt->rtp = ast_rtp_new_with_bindaddr(sched, io, 1, 0,bindaddr.sin_addr);
   if (!pvt->rtp) {
      ast_log(LOG_WARNING, "Unable to create RTP session: %s\n", strerror(errno));
      free(pvt);
      return NULL;
   }
   ast_rtp_settos(pvt->rtp, tos);
   ast_mutex_init(&pvt->lock);
   /* Ensure the call token is allocated */
   if ((pvt->cd).call_token == NULL) {
      (pvt->cd).call_token = (char *)malloc(128);
   }
   if (!pvt->cd.call_token) {
      ast_log(LOG_ERROR, "Not enough memory to alocate call token\n");
      return NULL;
   }
   memset((char *)(pvt->cd).call_token, 0, 128);
   pvt->cd.call_reference = callid;
   memcpy(&pvt->options, &global_options, sizeof(pvt->options));
   if (pvt->options.dtmfmode & H323_DTMF_RFC2833) {
      pvt->nonCodecCapability |= AST_RTP_DTMF;
   } else {
      pvt->nonCodecCapability &= ~AST_RTP_DTMF;
   }
   strncpy(pvt->context, default_context, sizeof(pvt->context) - 1);
   pvt->newstate = pvt->newcontrol = -1;
   /* Add to interface list */
   ast_mutex_lock(&iflock);
   pvt->next = iflist;