sip_pinger.h

/* $Id$
 *
 * Copyright (C) 2005 Voice System SRL
 *
 * 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:
 * ---------
 * 2005-07-11  created (bogdan)
 */


#ifndef NATHELPER_OPTIONS_H_
#define NATHELPER_OPTIONS_H_

#include <stdlib.h>
#include <string.h>

#include "../../parser/parse_rr.h"
#include "../../str.h"
#include "../../ut.h"
#include "../../ip_addr.h"

/* size of buffer used for building SIP PING req */
#define MAX_SIPPING_SIZE 65536

/* helping macros for building SIP PING ping request */
#define append_fix( _p, _s) \
        do {\
                memcpy(_p, _s, sizeof(_s)-1);\
                _p += sizeof(_s)-1;\
        }while(0)

/* info used to generate SIP ping requests */
static int  sipping_fromtag = 0;
static char sipping_callid_buf[8];
static int  sipping_callid_cnt = 0;
static str  sipping_callid = {0,0};
static str  sipping_from = {0,0};
static str  sipping_method = {"OPTIONS",7};



static void init_sip_ping(void)
{
        int len;
        char *p;

        /* FROM tag - some random number */
        sipping_fromtag = rand();
        /* callid fix part - hexa string */
        len = 8;
        p = sipping_callid_buf;
        int2reverse_hex( &p, &len, rand() );
        sipping_callid.s = sipping_callid_buf;
        sipping_callid.len = 8-len;
        /* callid counter part */
        sipping_callid_cnt = rand();
}



static int sipping_rpl_filter(struct sip_msg *rpl)
{
        struct cseq_body* cseq_b;

        /* first check number of vias -> must be only one */
        if (parse_headers( rpl, HDR_VIA2_F, 0 )==-1 || (rpl->via2!=0))
                goto skip;

        /* check the method -> we need CSeq header */
        if ( (!rpl->cseq && parse_headers(rpl,HDR_CSEQ_F,0)!=0) || rpl->cseq==0 ) {
                LM_ERR("failed to parse CSeq\n");
                goto error;
        }
        cseq_b = (struct cseq_body*)rpl->cseq->parsed;
        if (cseq_b->method.len!=sipping_method.len ||
        strncmp(cseq_b->method.s,sipping_method.s,sipping_method.len)!=0)
                goto skip;

        /* check constant part of callid */
        if ( (!rpl->callid && parse_headers(rpl,HDR_CALLID_F,0)!=0) ||
        rpl->callid==0 ) {
                LM_ERR("failed to parse Call-ID\n");
                goto error;
        }
        if ( rpl->callid->body.len<=sipping_callid.len+1 ||
        strncmp(rpl->callid->body.s,sipping_callid.s,sipping_callid.len)!=0 ||
        rpl->callid->body.s[sipping_callid.len]!='-')
                goto skip;

        LM_DBG("reply for SIP natping filtered\n");
        /* it's a reply to a SIP NAT ping -> absorb it and stop any
         * further processing of it */
        return 0;
skip:
        return 1;
error:
        return -1;
}



/* build the buffer of a SIP ping request */
static inline char* build_sipping(str *curi, struct socket_info* s, str *path,
                                                                                                                                int *len_p)
{
#define s_len(_s) (sizeof(_s)-1)
        static char buf[MAX_SIPPING_SIZE];
        char *p;
        int len;

        if ( sipping_method.len + 1 + curi->len + s_len(" SIP/2.0"CRLF) +
                s_len("Via: SIP/2.0/UDP ") + s->address_str.len +
                1 + s->port_no_str.len + s_len(";branch=0") +
                (path->len ? (s_len(CRLF"Route: ") + path->len) : 0) +
                s_len(CRLF"From: ") +  sipping_from.len + s_len(";tag=") + 8 +
                s_len(CRLF"To: ") + curi->len +
                s_len(CRLF"Call-ID: ") + sipping_callid.len + 1 + 8 + 1 + 8 + 1 +
                s->address_str.len +
                s_len(CRLF"CSeq: 1 ") + sipping_method.len +
                s_len(CRLF"Content-Length: 0" CRLF CRLF)
                > MAX_SIPPING_SIZE )
        {
                LM_ERR("len exceeds %d\n",MAX_SIPPING_SIZE);
                return 0;
        }

        p = buf;
        append_str( p, sipping_method.s, sipping_method.len);
        *(p++) = ' ';
        append_str( p, curi->s, curi->len);
        append_fix( p, " SIP/2.0"CRLF"Via: SIP/2.0/UDP ");
        append_str( p, s->address_str.s, s->address_str.len);
        *(p++) = ':';
        append_str( p, s->port_no_str.s, s->port_no_str.len);
        if (path->len) {
                append_fix( p, ";branch=0"CRLF"Route: ");
                append_str( p, path->s, path->len);
                append_fix( p, CRLF"From: ");
        } else {
                append_fix( p, ";branch=0"CRLF"From: ");
        }
        append_str( p, sipping_from.s, sipping_from.len);
        append_fix( p, ";tag=");
        len = 8;
        int2reverse_hex( &p, &len, sipping_fromtag++ );
        append_fix( p, CRLF"To: ");
        append_str( p, curi->s, curi->len);
        append_fix( p, CRLF"Call-ID: ");
        append_str( p, sipping_callid.s, sipping_callid.len);
        *(p++) = '-';
        len = 8;
        int2reverse_hex( &p, &len, sipping_callid_cnt++ );
        *(p++) = '-';
        len = 8;
        int2reverse_hex( &p, &len, get_ticks() );
        *(p++) = '@';
        append_str( p, s->address_str.s, s->address_str.len);
        append_fix( p, CRLF"CSeq: 1 ");
        append_str( p, sipping_method.s, sipping_method.len);
        append_fix( p, CRLF"Content-Length: 0" CRLF CRLF);

        *len_p = p - buf;
        return buf;
}


#endif