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packet-t38-template.c

/* packet-t38.c
 * Routines for T.38 packet dissection
 * 2003  Hans Viens
 * 2004  Alejandro Vaquero, add support Conversations for SDP
 * 2006  Alejandro Vaquero, add T30 reassemble and dissection
 *
 * $Id: packet-t38-template.c 26693 2008-11-04 21:42:02Z wmeier $
 *
 * Wireshark - Network traffic analyzer
 * By Gerald Combs <gerald@wireshark.org>
 * Copyright 1998 Gerald Combs
 *
 * 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.
 */


/* Depending on what ASN.1 specification is used you may have to change
 * the preference setting regarding Pre-Corrigendum ASN.1 specification:
 * http://www.itu.int/ITU-T/asn1/database/itu-t/t/t38/1998/T38.html  (Pre-Corrigendum=TRUE)
 * http://www.itu.int/ITU-T/asn1/database/itu-t/t/t38/2003/T38(1998).html (Pre-Corrigendum=TRUE)
 *
 * http://www.itu.int/ITU-T/asn1/database/itu-t/t/t38/2003/T38(2002).html (Pre-Corrigendum=FALSE)
 * http://www.itu.int/ITU-T/asn1/database/itu-t/t/t38/2002/t38.html  (Pre-Corrigendum=FALSE)
 * http://www.itu.int/ITU-T/asn1/database/itu-t/t/t38/2002-Amd1/T38.html (Pre-Corrigendum=FALSE)
 */

/* TO DO:  
 * - TCP desegmentation is currently not supported for T.38 IFP directly over TCP. 
 * - H.245 dissectors should be updated to start conversations for T.38 similar to RTP.
 * - Sometimes the last octet is not high-lighted when selecting something in the tree. Bug in PER dissector? 
 * - Add support for RTP payload audio/t38 (draft-jones-avt-audio-t38-03.txt), i.e. T38 in RTP packets.
 */


#ifdef HAVE_CONFIG_H
# include "config.h"
#endif

#include <glib.h>
#include <epan/packet.h>
#include <epan/reassemble.h>
#include <epan/conversation.h>
#include <epan/tap.h>
#include <epan/expert.h>

#include <stdio.h>
#include <string.h>

#include "packet-t38.h"
#include <epan/prefs.h>
#include <epan/ipproto.h>
#include <epan/asn1.h>
#include "packet-per.h"
#include "packet-tpkt.h"
#include <epan/emem.h>
#include <epan/strutil.h>

#define PORT_T38 6004  
static guint global_t38_tcp_port = PORT_T38;
static guint global_t38_udp_port = PORT_T38;

static int t38_tap = -1;

/* dissect using the Pre Corrigendum T.38 ASN.1 specification (1998) */
static gboolean use_pre_corrigendum_asn1_specification = TRUE;

/* dissect packets that looks like RTP version 2 packets as RTP     */
/* instead of as T.38. This may result in that some T.38 UPTL       */
/* packets with sequence number values higher than 32767 may be     */
/* shown as RTP packets.                                            */ 
static gboolean dissect_possible_rtpv2_packets_as_rtp = FALSE;


/* Reassembly of T.38 PDUs over TPKT over TCP */
static gboolean t38_tpkt_reassembly = TRUE;

/* Preference setting whether TPKT header is used when sending T.38 over TCP.
 * The default setting is Maybe where the dissector will look on the first
 * bytes to try to determine whether TPKT header is used or not. This may not
 * work so well in some cases. You may want to change the setting to Always or
 * Newer.
 */
#define T38_TPKT_NEVER 0   /* Assume that there is never a TPKT header    */
#define T38_TPKT_ALWAYS 1  /* Assume that there is always a TPKT header   */
#define T38_TPKT_MAYBE 2   /* Assume TPKT if first octets are 03-00-xx-xx */
static gint t38_tpkt_usage = T38_TPKT_MAYBE;

static const enum_val_t t38_tpkt_options[] = {
  {"never", "Never", T38_TPKT_NEVER},
  {"always", "Always", T38_TPKT_ALWAYS},
  {"maybe", "Maybe", T38_TPKT_MAYBE},
  {NULL, NULL, -1}
};



/* T38 */
static dissector_handle_t t38_udp_handle;
static dissector_handle_t t38_tcp_handle;
static dissector_handle_t t38_tcp_pdu_handle;
static dissector_handle_t rtp_handle;
static dissector_handle_t t30_hdlc_handle;
static dissector_handle_t data_handle;

static gint32 Type_of_msg_value;
static guint32 Data_Field_field_type_value;
static guint32 Data_value;
static guint32 T30ind_value;
static guint32 Data_Field_item_num;

static int proto_t38 = -1;
#include "packet-t38-hf.c"

/* T38 setup fields */
static int hf_t38_setup        = -1;
static int hf_t38_setup_frame  = -1;
static int hf_t38_setup_method = -1;

/* T38 Data reassemble fields */
static int hf_t38_fragments = -1;
static int hf_t38_fragment = -1;
static int hf_t38_fragment_overlap = -1;
static int hf_t38_fragment_overlap_conflicts = -1;
static int hf_t38_fragment_multiple_tails = -1;
static int hf_t38_fragment_too_long_fragment = -1;
static int hf_t38_fragment_error = -1;
static int hf_t38_reassembled_in = -1;

static gint ett_t38 = -1;
#include "packet-t38-ett.c"
static gint ett_t38_setup = -1;

static gint ett_data_fragment = -1;
static gint ett_data_fragments = -1;

static gboolean primary_part = TRUE;
static guint32 seq_number = 0;

/* Tables for reassembly of Data fragments. */
static GHashTable *data_fragment_table = NULL;
static GHashTable *data_reassembled_table = NULL;

static const fragment_items data_frag_items = {
      /* Fragment subtrees */
      &ett_data_fragment,
      &ett_data_fragments,
      /* Fragment fields */
      &hf_t38_fragments,
      &hf_t38_fragment,
      &hf_t38_fragment_overlap,
      &hf_t38_fragment_overlap_conflicts,
      &hf_t38_fragment_multiple_tails,
      &hf_t38_fragment_too_long_fragment,
      &hf_t38_fragment_error,
      /* Reassembled in field */
      &hf_t38_reassembled_in,
      /* Tag */
      "Data fragments"
};

typedef struct _fragment_key {
      address src;
      address dst;
      guint32     id;
} fragment_key;

static conversation_t *p_conv= NULL;
static t38_conv *p_t38_conv = NULL;
static t38_conv *p_t38_packet_conv = NULL;
static t38_conv_info *p_t38_conv_info = NULL;
static t38_conv_info *p_t38_packet_conv_info = NULL;

/* RTP Version is the first 2 bits of the first octet in the UDP payload*/
#define RTP_VERSION(octet)    ((octet) >> 6)

void proto_reg_handoff_t38(void);

static void show_setup_info(tvbuff_t *tvb, proto_tree *tree, t38_conv *p_t38_conv);
/* Preferences bool to control whether or not setup info should be shown */
static gboolean global_t38_show_setup_info = TRUE;

/* Can tap up to 4 T38 packets within same packet */
/* We only tap the primary part, not the redundancy */
#define MAX_T38_MESSAGES_IN_PACKET 4
static t38_packet_info t38_info_arr[MAX_T38_MESSAGES_IN_PACKET];
static int t38_info_current=0;
static t38_packet_info *t38_info=NULL;

static void t38_defragment_init(void)
{
      /* Init reassemble tables */
      fragment_table_init(&data_fragment_table);
      reassembled_table_init(&data_reassembled_table);
}


/* Set up an T38 conversation */
void t38_add_address(packet_info *pinfo,
                     address *addr, int port,
                     int other_port,
                     const gchar *setup_method, guint32 setup_frame_number)
{
        address null_addr;
        conversation_t* p_conv;
        t38_conv* p_conv_data = NULL;

        /*
         * If this isn't the first time this packet has been processed,
         * we've already done this work, so we don't need to do it
         * again.
         */
        if (pinfo->fd->flags.visited)
        {
                return;
        }

        SET_ADDRESS(&null_addr, AT_NONE, 0, NULL);

        /*
         * Check if the ip address and port combination is not
         * already registered as a conversation.
         */
        p_conv = find_conversation( setup_frame_number, addr, &null_addr, PT_UDP, port, other_port,
                                NO_ADDR_B | (!other_port ? NO_PORT_B : 0));

        /*
         * If not, create a new conversation.
         */
        if ( !p_conv || p_conv->setup_frame != setup_frame_number) {
                p_conv = conversation_new( setup_frame_number, addr, &null_addr, PT_UDP,
                                           (guint32)port, (guint32)other_port,
                                                                   NO_ADDR2 | (!other_port ? NO_PORT2 : 0));
        }

        /* Set dissector */
        conversation_set_dissector(p_conv, t38_udp_handle);

        /*
         * Check if the conversation has data associated with it.
         */
        p_conv_data = conversation_get_proto_data(p_conv, proto_t38);

        /*
         * If not, add a new data item.
         */
        if ( ! p_conv_data ) {
                /* Create conversation data */
                p_conv_data = se_alloc(sizeof(t38_conv));

                conversation_add_proto_data(p_conv, proto_t38, p_conv_data);
        }

        /*
         * Update the conversation data.
         */
        g_strlcpy(p_conv_data->setup_method, setup_method, MAX_T38_SETUP_METHOD_SIZE);
        p_conv_data->setup_frame_number = setup_frame_number;
            p_conv_data->src_t38_info.reass_ID = 0;
            p_conv_data->src_t38_info.reass_start_seqnum = -1;
            p_conv_data->src_t38_info.reass_data_type = 0;
            p_conv_data->src_t38_info.last_seqnum = -1;
            p_conv_data->src_t38_info.packet_lost = 0;
            p_conv_data->src_t38_info.burst_lost = 0;
            p_conv_data->src_t38_info.time_first_t4_data = 0;


            p_conv_data->dst_t38_info.reass_ID = 0;
            p_conv_data->dst_t38_info.reass_start_seqnum = -1;
            p_conv_data->dst_t38_info.reass_data_type = 0;
            p_conv_data->dst_t38_info.last_seqnum = -1;
            p_conv_data->dst_t38_info.packet_lost = 0;
            p_conv_data->dst_t38_info.burst_lost = 0;
            p_conv_data->dst_t38_info.time_first_t4_data = 0;
}


fragment_data *
force_reassemble_seq(packet_info *pinfo, guint32 id,
           GHashTable *fragment_table)
{
      fragment_key key;
      fragment_data *fd_head;
      fragment_data *fd_i;
      fragment_data *last_fd;
      guint32 dfpos, size, packet_lost, burst_lost, seq_num;

      /* create key to search hash with */
      key.src = pinfo->src;
      key.dst = pinfo->dst;
      key.id  = id;

      fd_head = g_hash_table_lookup(fragment_table, &key);

      /* have we already seen this frame ?*/
      if (pinfo->fd->flags.visited) {
            if (fd_head != NULL && fd_head->flags & FD_DEFRAGMENTED) {
                  return fd_head;
            } else {
                  return NULL;
            }
      }

      if (fd_head==NULL){
            /* we must have it to continue */
            return NULL;
      }

      /* check for packet lost and count the burst of packet lost */
      packet_lost = 0;
      burst_lost = 0;
      seq_num = 0;
      for(fd_i=fd_head->next;fd_i;fd_i=fd_i->next) {
            if (seq_num != fd_i->offset) {
                  packet_lost += fd_i->offset - seq_num;
                  if ( (fd_i->offset - seq_num) > burst_lost ) {
                        burst_lost = fd_i->offset - seq_num;
                  }
            }
            seq_num = fd_i->offset + 1;
      }

      /* we have received an entire packet, defragment it and
     * free all fragments
     */
      size=0;
      last_fd=NULL;
      for(fd_i=fd_head->next;fd_i;fd_i=fd_i->next) {
        if(!last_fd || last_fd->offset!=fd_i->offset){
          size+=fd_i->len;
        }
        last_fd=fd_i;
      }
      fd_head->data = g_malloc(size);
      fd_head->len = size;          /* record size for caller     */

      /* add all data fragments */
      dfpos = 0;
      last_fd=NULL;
      for (fd_i=fd_head->next;fd_i && fd_i->len + dfpos <= size;fd_i=fd_i->next) {
        if (fd_i->len) {
          if(!last_fd || last_fd->offset!=fd_i->offset){
            memcpy(fd_head->data+dfpos,fd_i->data,fd_i->len);
            dfpos += fd_i->len;
          } else {
            /* duplicate/retransmission/overlap */
            fd_i->flags    |= FD_OVERLAP;
            fd_head->flags |= FD_OVERLAP;
            if( (last_fd->len!=fd_i->datalen)
              || memcmp(last_fd->data, fd_i->data, last_fd->len) ){
                  fd_i->flags    |= FD_OVERLAPCONFLICT;
                  fd_head->flags |= FD_OVERLAPCONFLICT;
            }
          }
        }
        last_fd=fd_i;
      }

      /* we have defragmented the pdu, now free all fragments*/
      for (fd_i=fd_head->next;fd_i;fd_i=fd_i->next) {
        if(fd_i->data){
          g_free(fd_i->data);
          fd_i->data=NULL;
        }
      }

      /* mark this packet as defragmented */
      fd_head->flags |= FD_DEFRAGMENTED;
      fd_head->reassembled_in=pinfo->fd->num;

      if (check_col(pinfo->cinfo, COL_INFO))
                  col_append_fstr(pinfo->cinfo, COL_INFO, " (t4-data Reassembled: %d pack lost, %d pack burst lost)", packet_lost, burst_lost);
      
      p_t38_packet_conv_info->packet_lost = packet_lost;
      p_t38_packet_conv_info->burst_lost = burst_lost;

      return fd_head;
}

/* T38 Routines */
#include "packet-t38-fn.c"

/* initialize the tap t38_info and the conversation */
static void
init_t38_info_conv(packet_info *pinfo)
{
      /* tap info */
      t38_info_current++;
      if (t38_info_current==MAX_T38_MESSAGES_IN_PACKET) {
            t38_info_current=0;
      }
      t38_info = &t38_info_arr[t38_info_current];

      t38_info->seq_num = 0;
      t38_info->type_msg = 0;
      t38_info->data_value = 0;
      t38_info->t30ind_value =0;
      t38_info->setup_frame_number = 0;
      t38_info->Data_Field_field_type_value = 0;
      t38_info->desc[0] = '\0';
      t38_info->desc_comment[0] = '\0';
      t38_info->time_first_t4_data = 0;
      t38_info->frame_num_first_t4_data = 0;


      /* 
            p_t38_packet_conv hold the conversation info in each of the packets.
            p_t38_conv hold the conversation info used to reassemble the HDLC packets, and also the Setup info (e.g SDP)
            If we already have p_t38_packet_conv in the packet, it means we already reassembled the HDLC packets, so we don't 
            need to use p_t38_conv 
      */
      p_t38_packet_conv = NULL;
      p_t38_conv = NULL;

      /* Use existing packet info if available */
       p_t38_packet_conv = p_get_proto_data(pinfo->fd, proto_t38);


      /* find the conversation used for Reassemble and Setup Info */
      p_conv = find_conversation(pinfo->fd->num, &pinfo->net_src, &pinfo->net_dst,
                                   pinfo->ptype,
                                   pinfo->srcport, pinfo->destport, NO_ADDR_B | NO_PORT_B);

      /* create a conv if it doen't exist */
      if (!p_conv) {
            p_conv = conversation_new(pinfo->fd->num, &pinfo->net_src, &pinfo->net_dst,
                        pinfo->ptype, pinfo->srcport, pinfo->destport, NO_ADDR_B | NO_PORT_B);

            /* Set dissector */
            conversation_set_dissector(p_conv, t38_udp_handle);
      }

      if (!p_t38_packet_conv) {
            p_t38_conv = conversation_get_proto_data(p_conv, proto_t38);

            /* create the conversation if it doen't exist */
            if (!p_t38_conv) {
                  p_t38_conv = se_alloc(sizeof(t38_conv));
                  p_t38_conv->setup_method[0] = '\0';
                  p_t38_conv->setup_frame_number = 0;

                  p_t38_conv->src_t38_info.reass_ID = 0;
                  p_t38_conv->src_t38_info.reass_start_seqnum = -1;
                  p_t38_conv->src_t38_info.reass_data_type = 0;
                  p_t38_conv->src_t38_info.last_seqnum = -1;
                  p_t38_conv->src_t38_info.packet_lost = 0;
                  p_t38_conv->src_t38_info.burst_lost = 0;
                  p_t38_conv->src_t38_info.time_first_t4_data = 0;

                  p_t38_conv->dst_t38_info.reass_ID = 0;
                  p_t38_conv->dst_t38_info.reass_start_seqnum = -1;
                  p_t38_conv->dst_t38_info.reass_data_type = 0;
                  p_t38_conv->dst_t38_info.last_seqnum = -1;
                  p_t38_conv->dst_t38_info.packet_lost = 0;
                  p_t38_conv->dst_t38_info.burst_lost = 0;
                  p_t38_conv->dst_t38_info.time_first_t4_data = 0;

                  conversation_add_proto_data(p_conv, proto_t38, p_t38_conv);
            }

            /* copy the t38 conversation info to the packet t38 conversation */
            p_t38_packet_conv = se_alloc(sizeof(t38_conv));
            g_strlcpy(p_t38_packet_conv->setup_method, p_t38_conv->setup_method, MAX_T38_SETUP_METHOD_SIZE);
            p_t38_packet_conv->setup_frame_number = p_t38_conv->setup_frame_number;

            memcpy(&(p_t38_packet_conv->src_t38_info), &(p_t38_conv->src_t38_info), sizeof(t38_conv_info));
            memcpy(&(p_t38_packet_conv->dst_t38_info), &(p_t38_conv->dst_t38_info), sizeof(t38_conv_info));

            p_add_proto_data(pinfo->fd, proto_t38, p_t38_packet_conv);
      }

      if (ADDRESSES_EQUAL(&p_conv->key_ptr->addr1, &pinfo->net_src)) {
            p_t38_conv_info = &(p_t38_conv->src_t38_info);
            p_t38_packet_conv_info = &(p_t38_packet_conv->src_t38_info);
      } else {
            p_t38_conv_info = &(p_t38_conv->dst_t38_info);
            p_t38_packet_conv_info = &(p_t38_packet_conv->dst_t38_info);
      }

      /* update t38_info */
      t38_info->setup_frame_number = p_t38_packet_conv->setup_frame_number;
}

/* Entry point for dissection */
static void
dissect_t38_udp(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
{
      guint8 octet1;
      proto_item *it;
      proto_tree *tr;
      guint32 offset=0;

      /*
       * XXX - heuristic to check for misidentified packets.
       */
      if (dissect_possible_rtpv2_packets_as_rtp){
            octet1 = tvb_get_guint8(tvb, offset);
            if (RTP_VERSION(octet1) == 2){
                  call_dissector(rtp_handle,tvb,pinfo,tree);
                  return;
            }
      }

      if (check_col(pinfo->cinfo, COL_PROTOCOL)){
            col_set_str(pinfo->cinfo, COL_PROTOCOL, "T.38");
      }
      if (check_col(pinfo->cinfo, COL_INFO)){
            col_clear(pinfo->cinfo, COL_INFO);
      }

      primary_part = TRUE;

      /* This indicate the item number in the primary part of the T38 message, it is used for the reassemble of T30 packets */
      Data_Field_item_num = 0;

      it=proto_tree_add_protocol_format(tree, proto_t38, tvb, 0, -1, "ITU-T Recommendation T.38");
      tr=proto_item_add_subtree(it, ett_t38);

      /* init tap and conv info */
      init_t38_info_conv(pinfo);

      /* Show Conversation setup info if exists*/
      if (global_t38_show_setup_info) {
            show_setup_info(tvb, tr, p_t38_packet_conv);
      }

      if (check_col(pinfo->cinfo, COL_INFO)){
            col_append_str(pinfo->cinfo, COL_INFO, "UDP: UDPTLPacket ");
      }

      offset = dissect_UDPTLPacket_PDU(tvb, pinfo, tr);

      if (tvb_length_remaining(tvb,offset)>0){
            if (tr){
                  proto_tree_add_text(tr, tvb, offset, tvb_reported_length_remaining(tvb, offset),
                        "[MALFORMED PACKET or wrong preference settings]");
            }
            if (check_col(pinfo->cinfo, COL_INFO)){
                  col_append_str(pinfo->cinfo, COL_INFO, " [Malformed?]");
            }
      }
}

static void
dissect_t38_tcp_pdu(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
{
      proto_item *it;
      proto_tree *tr;
      guint32 offset=0;
    tvbuff_t *next_tvb;
      guint16 ifp_packet_number=1;

      if (check_col(pinfo->cinfo, COL_PROTOCOL)){
            col_set_str(pinfo->cinfo, COL_PROTOCOL, "T.38");
      }
      if (check_col(pinfo->cinfo, COL_INFO)){
            col_clear(pinfo->cinfo, COL_INFO);
      }

      primary_part = TRUE;

      /* This indicate the item number in the primary part of the T38 message, it is used for the reassemble of T30 packets */
      Data_Field_item_num = 0;

      it=proto_tree_add_protocol_format(tree, proto_t38, tvb, 0, -1, "ITU-T Recommendation T.38");
      tr=proto_item_add_subtree(it, ett_t38);

      /* init tap and conv info */
      init_t38_info_conv(pinfo);

      /* Show Conversation setup info if exists*/
      if (global_t38_show_setup_info) {
            show_setup_info(tvb, tr, p_t38_packet_conv);
      }

      if (check_col(pinfo->cinfo, COL_INFO)){
            col_append_str(pinfo->cinfo, COL_INFO, "TCP: IFPPacket");
      }

      while(tvb_length_remaining(tvb,offset)>0)
      {
            next_tvb = tvb_new_subset(tvb, offset, -1, -1);
            offset += dissect_IFPPacket_PDU(next_tvb, pinfo, tr);
            ifp_packet_number++;

            if(tvb_length_remaining(tvb,offset)>0){
                  if(t38_tpkt_usage == T38_TPKT_ALWAYS){
                        if(tr){
                              proto_tree_add_text(tr, tvb, offset, tvb_reported_length_remaining(tvb, offset),
                                    "[MALFORMED PACKET or wrong preference settings]");
                        }
                        if (check_col(pinfo->cinfo, COL_INFO)){
                              col_append_str(pinfo->cinfo, COL_INFO, " [Malformed?]");
                        }
                        break;
                  } 
                  else {
                        if (check_col(pinfo->cinfo, COL_INFO)){
                              col_append_fstr(pinfo->cinfo, COL_INFO, " IFPPacket#%u",ifp_packet_number);
                        }
                  }
            }
      }

}

static void
dissect_t38_tcp(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
{
      primary_part = TRUE;

      if(t38_tpkt_usage == T38_TPKT_ALWAYS){
            dissect_tpkt_encap(tvb,pinfo,tree,t38_tpkt_reassembly,t38_tcp_pdu_handle);
      } 
      else if((t38_tpkt_usage == T38_TPKT_NEVER) || (is_tpkt(tvb,1) == -1)){
            dissect_t38_tcp_pdu(tvb, pinfo, tree);
      } 
      else {
            dissect_tpkt_encap(tvb,pinfo,tree,t38_tpkt_reassembly,t38_tcp_pdu_handle);
      }
}

static void
dissect_t38(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
{
      if(pinfo->ipproto == IP_PROTO_TCP)
      {
            dissect_t38_tcp(tvb, pinfo, tree);
      }
      else if(pinfo->ipproto == IP_PROTO_UDP)
      {   
            dissect_t38_udp(tvb, pinfo, tree);
      }
}

/* Look for conversation info and display any setup info found */
void 
show_setup_info(tvbuff_t *tvb, proto_tree *tree, t38_conv *p_t38_conv)
{
      proto_tree *t38_setup_tree;
      proto_item *ti;

      if (!p_t38_conv || p_t38_conv->setup_frame_number == 0) {
            /* there is no Setup info */
            return;
      }

      ti =  proto_tree_add_string_format(tree, hf_t38_setup, tvb, 0, 0,
                      "",
                      "Stream setup by %s (frame %u)",
                      p_t38_conv->setup_method,
                      p_t38_conv->setup_frame_number);
    PROTO_ITEM_SET_GENERATED(ti);
    t38_setup_tree = proto_item_add_subtree(ti, ett_t38_setup);
    if (t38_setup_tree)
    {
            /* Add details into subtree */
            proto_item* item = proto_tree_add_uint(t38_setup_tree, hf_t38_setup_frame,
                                                               tvb, 0, 0, p_t38_conv->setup_frame_number);
            PROTO_ITEM_SET_GENERATED(item);
            item = proto_tree_add_string(t38_setup_tree, hf_t38_setup_method,
                                                     tvb, 0, 0, p_t38_conv->setup_method);
            PROTO_ITEM_SET_GENERATED(item);
    }
}



/* Wireshark Protocol Registration */
void
proto_register_t38(void)
{
      static hf_register_info hf[] =
      {
#include "packet-t38-hfarr.c"
            {   &hf_t38_setup,
                { "Stream setup", "t38.setup", FT_STRING, BASE_NONE,
                NULL, 0x0, "Stream setup, method and frame number", HFILL }},
            {   &hf_t38_setup_frame,
            { "Stream frame", "t38.setup-frame", FT_FRAMENUM, BASE_NONE,
            NULL, 0x0, "Frame that set up this stream", HFILL }},
        {   &hf_t38_setup_method,
            { "Stream Method", "t38.setup-method", FT_STRING, BASE_NONE,
            NULL, 0x0, "Method used to set up this stream", HFILL }},
            {&hf_t38_fragments,
                  {"Message fragments", "t38.fragments",
                  FT_NONE, BASE_NONE, NULL, 0x00,     NULL, HFILL } },
            {&hf_t38_fragment,
                  {"Message fragment", "t38.fragment",
                  FT_FRAMENUM, BASE_NONE, NULL, 0x00, NULL, HFILL } },
            {&hf_t38_fragment_overlap,
                  {"Message fragment overlap", "t38.fragment.overlap",
                  FT_BOOLEAN, BASE_NONE, NULL, 0x00, NULL, HFILL } },
            {&hf_t38_fragment_overlap_conflicts,
                  {"Message fragment overlapping with conflicting data",
                  "t38.fragment.overlap.conflicts",
                  FT_BOOLEAN, BASE_NONE, NULL, 0x00, NULL, HFILL } },
            {&hf_t38_fragment_multiple_tails,
                  {"Message has multiple tail fragments",
                  "t38.fragment.multiple_tails", 
                  FT_BOOLEAN, BASE_NONE, NULL, 0x00, NULL, HFILL } },
            {&hf_t38_fragment_too_long_fragment,
                  {"Message fragment too long", "t38.fragment.too_long_fragment",
                  FT_BOOLEAN, BASE_NONE, NULL, 0x00, NULL, HFILL } },
            {&hf_t38_fragment_error,
                  {"Message defragmentation error", "t38.fragment.error",
                  FT_FRAMENUM, BASE_NONE, NULL, 0x00, NULL, HFILL } },
            {&hf_t38_reassembled_in,
                  {"Reassembled in", "t38.reassembled.in",
                  FT_FRAMENUM, BASE_NONE, NULL, 0x00, NULL, HFILL } },
      };

      static gint *ett[] =
      {
            &ett_t38,
#include "packet-t38-ettarr.c"
            &ett_t38_setup,
            &ett_data_fragment,
            &ett_data_fragments
      };

      module_t *t38_module;

      proto_t38 = proto_register_protocol("T.38", "T.38", "t38");
      proto_register_field_array(proto_t38, hf, array_length(hf));
      proto_register_subtree_array(ett, array_length(ett));
      register_dissector("t38", dissect_t38, proto_t38);

      /* Init reassemble tables for HDLC */
      register_init_routine(t38_defragment_init);

      t38_tap = register_tap("t38");

      t38_module = prefs_register_protocol(proto_t38, proto_reg_handoff_t38);
      prefs_register_bool_preference(t38_module, "use_pre_corrigendum_asn1_specification",
          "Use the Pre-Corrigendum ASN.1 specification",
          "Whether the T.38 dissector should decode using the Pre-Corrigendum T.38 "
            "ASN.1 specification (1998).",
          &use_pre_corrigendum_asn1_specification);
      prefs_register_bool_preference(t38_module, "dissect_possible_rtpv2_packets_as_rtp",
          "Dissect possible RTP version 2 packets with RTP dissector",
          "Whether a UDP packet that looks like RTP version 2 packet will "
            "be dissected as RTP packet or T.38 packet. If enabled there is a risk that T.38 UDPTL "
            "packets with sequence number higher than 32767 may be dissected as RTP.",
          &dissect_possible_rtpv2_packets_as_rtp);
      prefs_register_uint_preference(t38_module, "tcp.port",
            "T.38 TCP Port",
            "Set the TCP port for T.38 messages",
            10, &global_t38_tcp_port);
      prefs_register_uint_preference(t38_module, "udp.port",
            "T.38 UDP Port",
            "Set the UDP port for T.38 messages",
            10, &global_t38_udp_port);    
      prefs_register_bool_preference(t38_module, "reassembly",
            "Reassemble T.38 PDUs over TPKT over TCP",
            "Whether the dissector should reassemble T.38 PDUs spanning multiple TCP segments "
            "when TPKT is used over TCP. "
            "To use this option, you must also enable \"Allow subdissectors to reassemble "
            "TCP streams\" in the TCP protocol settings.",
            &t38_tpkt_reassembly);
      prefs_register_enum_preference(t38_module, "tpkt_usage",
            "TPKT used over TCP",
            "Whether T.38 is used with TPKT for TCP",
            (gint *)&t38_tpkt_usage,t38_tpkt_options,FALSE);

      prefs_register_bool_preference(t38_module, "show_setup_info",
                "Show stream setup information",
                "Where available, show which protocol and frame caused "
                "this T.38 stream to be created",
                &global_t38_show_setup_info);

}

void
proto_reg_handoff_t38(void)
{
      static gboolean t38_prefs_initialized = FALSE;
      static guint tcp_port;
      static guint udp_port;

      if (!t38_prefs_initialized) {
            t38_udp_handle=create_dissector_handle(dissect_t38_udp, proto_t38);
            t38_tcp_handle=create_dissector_handle(dissect_t38_tcp, proto_t38);
            t38_tcp_pdu_handle=create_dissector_handle(dissect_t38_tcp_pdu, proto_t38);
            rtp_handle = find_dissector("rtp");
            t30_hdlc_handle = find_dissector("t30.hdlc");
            data_handle = find_dissector("data");
            t38_prefs_initialized = TRUE;
      }
      else {
            dissector_delete("tcp.port", tcp_port, t38_tcp_handle);
            dissector_delete("udp.port", udp_port, t38_udp_handle);
      }
      tcp_port = global_t38_tcp_port;
      udp_port = global_t38_udp_port;

      dissector_add("tcp.port", tcp_port, t38_tcp_handle);
      dissector_add("udp.port", udp_port, t38_udp_handle);

}


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