callid.c

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/*
 * $Id: callid.c 5299 2008-12-04 18:12:33Z henningw $
 *
 * Fast Call-ID Generator
 *
 * Copyright (C) 2001-2003 FhG Fokus
 *
 * This file is part of Kamailio, a free SIP server.
 *
 * Kamailio 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
 *
 * Kamailio 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
 *
 * History:
 * ----------
 *  2003-04-09  Created by janakj
 *  2003-10-24  updated to the new socket_info lists (andrei)
 */

/*! \file
 * \brief TM :: Fast Call-ID Generator
 *
 * \ingroup tm
 * - Module: \ref tm
 */

#include <stdio.h>
#include <stdlib.h>
#include "../../dprint.h"
#include "../../pt.h"
#include "../../socket_info.h"
#include "callid.h"

#define CALLID_NR_LEN 20

/*! \brief
 *  Call-ID has the following form: <callid_nr>-<pid>\@<ip>
 * callid_nr is initialized as a random number and continually
 * increases; -<pid>\@<ip> is kept in callid_suffix
 */
#define CALLID_SUFFIX_LEN ( 1 /*!< - */                                            + \
             5 /*!< pid */                                          + \
                           42 /*!< embedded v4inv6 address can be looong '128.' */ + \
                       2 /*!< parenthesis [] */                              + \
                            1 /*!< ZT 0 */                                         + \
                      16 /*!< one never knows ;-) */                            \
                          )

#define CID_SEP '-'  /*!< the character which separates random from constant part */

static unsigned long callid_nr;
static char callid_buf[CALLID_NR_LEN + CALLID_SUFFIX_LEN];

str callid_prefix;
str callid_suffix;


/*! \brief
 * Initialize the Call-ID generator -- generates random prefix
 */
int init_callid(void)
{
   int rand_bits, i;

   /* calculate the initial call-id */
   /* how many bits and chars do we need to display the 
    * whole ULONG number */
   callid_prefix.len = sizeof(unsigned long) * 2;
   callid_prefix.s = callid_buf;

   if (callid_prefix.len > CALLID_NR_LEN) {
      LM_ERR("too small callid buffer\n");
      return -1;
   }
   
   for(rand_bits = 1, i = RAND_MAX; i; i >>= 1, rand_bits++);  /* how long are the rand()s ? */
   i = callid_prefix.len * 4 / rand_bits; /* how many rands() fit in the ULONG ? */

   /* now fill in the callid with as many random numbers as you can + 1 */
         callid_nr = rand(); /* this is the + 1 */

   while(i--) {
      callid_nr <<= rand_bits;
      callid_nr |= rand();
   }

   i = snprintf(callid_prefix.s, callid_prefix.len + 1, "%0*lx", callid_prefix.len, callid_nr);
   if ((i == -1) || (i > callid_prefix.len)) {
      LM_CRIT("callid calculation failed\n");
      return -2;
   }
   
   LM_DBG("Call-ID initialization: '%.*s'\n", callid_prefix.len, callid_prefix.s);
   return 0;
}


/*! \brief
 * Child initialization -- generates suffix
 */
int child_init_callid(int rank) 
{
   struct socket_info *si;
   
   /* on tcp/tls bind_address is 0 so try to get the first address we listen
    * on no matter the protocol */
   si=bind_address?bind_address:get_first_socket();
   if (si==0){
      LM_CRIT("null socket list\n");
      return -1;
   }
   callid_suffix.s = callid_buf + callid_prefix.len;

   callid_suffix.len = snprintf(callid_suffix.s, CALLID_SUFFIX_LEN,
                 "%c%d@%.*s", CID_SEP, my_pid(), 
                 si->address_str.len,
                 si->address_str.s);
   if ((callid_suffix.len == -1) || (callid_suffix.len > CALLID_SUFFIX_LEN)) {
      LM_ERR("buffer too small\n");
      return -1;
   }

   LM_DBG("callid: '%.*s'\n", callid_prefix.len + callid_suffix.len, callid_prefix.s);
   return 0;
}


/*! \brief
 * Increment a character in hex, return
 * carry flag
 */
static inline int inc_hexchar(char* _c)
{
   if (*_c == '9') {
      *_c = 'a';
      return 0;
   }

   if (*_c == 'f') {
      *_c = '0';
      return 1;
   }

   (*_c)++;
   return 0;
}


/*! \brief
 * Get a unique Call-ID
 */
void generate_callid(str* callid)
{
   int i;

   for(i = callid_prefix.len; i; i--) {
      if (!inc_hexchar(callid_prefix.s + i - 1)) break;
   }
   callid->s = callid_prefix.s;
   callid->len = callid_prefix.len + callid_suffix.len;
}