[Jon Ringle <ml-ethereal@xxxxxxxxxx>]

Hello,

I am currently developing an ICE implementation 
(http://www.ietf.org/internet-drafts/draft-ietf-mmusic-ice-03.txt). ICE uses 
STUN on the same port that the RTP media is sent on. The ICE application 
demultiplexes STUN/RTP by looking at the first 2 bits of the UDP packet. RTP 
will have 0b10 (rtp.version == 2) and a STUN packet will have 0b00. I would 
like to have ethereal dissect what looks like a rtp.version == 0 packet as a 
STUN packet.

I found in epan/dissectors/packet-rtp.c:dissect_rtp_heur() a check to validate 
that rtp.version == 2. I would like to modify this routine to call the STUN 
dissector, but I'm not sure how to make this call:

static gboolean
dissect_rtp_heur( tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree )
{
        guint8      octet1, octet2;
        unsigned int version;
        unsigned int payload_type;
        unsigned int offset = 0;

        /* This is a heuristic dissector, which means we get all the UDP
         * traffic not sent to a known dissector and not claimed by
         * a heuristic dissector called before us!
         */

        if (! global_rtp_heur)
                return FALSE;

        /* Get the fields in the first octet */
        octet1 = tvb_get_guint8( tvb, offset );
        version = RTP_VERSION( octet1 );

        if (version == 0) {
                /******************************************/
                /* Call the STUN dissector here, but how? */
                /******************************************/
                return TRUE;
        } else if (version != 2) {
                /* Unknown or unsupported version */
                return FALSE;
        }

        /* Get the fields in the second octet */
        octet2 = tvb_get_guint8( tvb, offset + 1 );
        payload_type = RTP_PAYLOAD_TYPE( octet2 );
        /*      if (payload_type == PT_PCMU ||
         *                   payload_type == PT_PCMA)
         *           payload_type == PT_G729)
         *       */
        if (payload_type <= PT_H263) {
                dissect_rtp( tvb, pinfo, tree );
                return TRUE;
        }
        else {
                return FALSE;
        }
}