wireshark/packet-udp.c

/* packet-udp.c
 * Routines for UDP packet disassembly
 *
 * $Id: packet-udp.c,v 1.103 2002/06/08 21:54:51 guy Exp $
 *
 * Ethereal - Network traffic analyzer
 * By Gerald Combs <gerald@ethereal.com>
 * Copyright 1998 Gerald Combs
 *
 * Richard Sharpe, 13-Feb-1999, added dispatch table support and 
 *                              support for tftp.
 * 
 * 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.
 */
 
#ifdef HAVE_CONFIG_H
# include "config.h"
#endif

#ifdef HAVE_SYS_TYPES_H
# include <sys/types.h>
#endif

#ifdef HAVE_NETINET_IN_H
# include <netinet/in.h>
#endif

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

#include <glib.h>
#include <epan/packet.h>
#include <epan/resolv.h>
#include "ipproto.h"
#include "in_cksum.h"
#include "prefs.h"

#include "packet-udp.h"

#include "packet-ip.h"
#include <epan/conversation.h>

static int proto_udp = -1;		
static int hf_udp_srcport = -1;
static int hf_udp_dstport = -1;
static int hf_udp_port = -1;
static int hf_udp_length = -1;
static int hf_udp_checksum = -1;
static int hf_udp_checksum_bad = -1;

static gint ett_udp = -1;

/* Place UDP summary in proto tree */
static gboolean udp_summary_in_tree = TRUE;

/* UDP structs and definitions */

typedef struct _e_udphdr {
  guint16 uh_sport;
  guint16 uh_dport;
  guint16 uh_ulen;
  guint16 uh_sum;
} e_udphdr;

static dissector_table_t udp_dissector_table;
static heur_dissector_list_t heur_subdissector_list;
static dissector_handle_t data_handle;

/* Determine if there is a sub-dissector and call it.  This has been */
/* separated into a stand alone routine to other protocol dissectors */
/* can call to it, ie. socks	*/

void
decode_udp_ports(tvbuff_t *tvb, int offset, packet_info *pinfo,
	proto_tree *tree, int uh_sport, int uh_dport)
{
  tvbuff_t *next_tvb;
  int low_port, high_port;

  next_tvb = tvb_new_subset(tvb, offset, -1, -1);

/* determine if this packet is part of a conversation and call dissector */
/* for the conversation if available */

  if (try_conversation_dissector(&pinfo->src, &pinfo->dst, PT_UDP,
		uh_sport, uh_dport, next_tvb, pinfo, tree))
    return;

  /* Do lookups with the subdissector table.
     We try the port number with the lower value first, followed by the
     port number with the higher value.  This means that, for packets
     where a dissector is registered for *both* port numbers:

	1) we pick the same dissector for traffic going in both directions;

	2) we prefer the port number that's more likely to be the right
	   one (as that prefers well-known ports to reserved ports);

     although there is, of course, no guarantee that any such strategy
     will always pick the right port number.

     XXX - we ignore port numbers of 0, as some dissectors use a port
     number of 0 to disable the port, and as RFC 768 says that the source
     port in UDP datagrams is optional and is 0 if not used. */
  if (uh_sport > uh_dport) {
    low_port = uh_dport;
    high_port = uh_sport;
  } else {
    low_port = uh_sport;
    high_port = uh_dport;
  }
  if (low_port != 0 &&
      dissector_try_port(udp_dissector_table, low_port, next_tvb, pinfo, tree))
    return;
  if (high_port != 0 &&
      dissector_try_port(udp_dissector_table, high_port, next_tvb, pinfo, tree))
    return;

  /* do lookup with the heuristic subdissector table */
  if (dissector_try_heuristic(heur_subdissector_list, next_tvb, pinfo, tree))
    return;

  call_dissector(data_handle,next_tvb, pinfo, tree);
}


static void
dissect_udp(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
{
  e_udphdr  uh;
  guint16    uh_sport, uh_dport, uh_ulen, uh_sum;
  proto_tree *udp_tree;
  proto_item *ti;
  guint      len;
  guint      reported_len;
  vec_t      cksum_vec[4];
  guint32    phdr[2];
  guint16    computed_cksum;
  int        offset = 0;

  if (check_col(pinfo->cinfo, COL_PROTOCOL))
    col_set_str(pinfo->cinfo, COL_PROTOCOL, "UDP");
  if (check_col(pinfo->cinfo, COL_INFO))
    col_clear(pinfo->cinfo, COL_INFO);

  /* Avoids alignment problems on many architectures. */
  tvb_memcpy(tvb, (guint8 *)&uh, offset, sizeof(e_udphdr));
  uh_sport = ntohs(uh.uh_sport);
  uh_dport = ntohs(uh.uh_dport);
  uh_ulen  = ntohs(uh.uh_ulen);
  uh_sum   = ntohs(uh.uh_sum);
  
  if (check_col(pinfo->cinfo, COL_INFO))
    col_add_fstr(pinfo->cinfo, COL_INFO, "Source port: %s  Destination port: %s",
	    get_udp_port(uh_sport), get_udp_port(uh_dport));
    
  if (tree) {
    if (udp_summary_in_tree) {
      ti = proto_tree_add_protocol_format(tree, proto_udp, tvb, offset, 8,
      "User Datagram Protocol, Src Port: %s (%u), Dst Port: %s (%u)",
      get_udp_port(uh_sport), uh_sport, get_udp_port(uh_dport), uh_dport);
    } else {
      ti = proto_tree_add_item(tree, proto_udp, tvb, offset, 8, FALSE);
    }
    udp_tree = proto_item_add_subtree(ti, ett_udp);

    proto_tree_add_uint_format(udp_tree, hf_udp_srcport, tvb, offset, 2, uh_sport,
	"Source port: %s (%u)", get_udp_port(uh_sport), uh_sport);
    proto_tree_add_uint_format(udp_tree, hf_udp_dstport, tvb, offset + 2, 2, uh_dport,
	"Destination port: %s (%u)", get_udp_port(uh_dport), uh_dport);

    proto_tree_add_uint_hidden(udp_tree, hf_udp_port, tvb, offset, 2, uh_sport);
    proto_tree_add_uint_hidden(udp_tree, hf_udp_port, tvb, offset+2, 2, uh_dport);

    proto_tree_add_uint(udp_tree, hf_udp_length, tvb, offset + 4, 2,  uh_ulen);
    reported_len = tvb_reported_length(tvb);
    len = tvb_length(tvb);
    if (uh_sum == 0) {
      /* No checksum supplied in the packet. */
      proto_tree_add_uint_format(udp_tree, hf_udp_checksum, tvb,
        offset + 6, 2, uh_sum, "Checksum: 0x%04x (none)", uh_sum);
    } else if (!pinfo->fragmented && len >= reported_len && len >= uh_ulen) {
      /* The packet isn't part of a fragmented datagram and isn't
         truncated, so we can checksum it.
	 XXX - make a bigger scatter-gather list once we do fragment
	 reassembly? */

      /* Set up the fields of the pseudo-header. */
      cksum_vec[0].ptr = pinfo->src.data;
      cksum_vec[0].len = pinfo->src.len;
      cksum_vec[1].ptr = pinfo->dst.data;
      cksum_vec[1].len = pinfo->dst.len;
      cksum_vec[2].ptr = (const guint8 *)&phdr;
      switch (pinfo->src.type) {

      case AT_IPv4:
	phdr[0] = htonl((IP_PROTO_UDP<<16) + reported_len);
	cksum_vec[2].len = 4;
	break;

      case AT_IPv6:
        phdr[0] = htonl(reported_len);
        phdr[1] = htonl(IP_PROTO_UDP);
        cksum_vec[2].len = 8;
        break;

      default:
        /* TCP runs only atop IPv4 and IPv6.... */
        g_assert_not_reached();
        break;
      }
      cksum_vec[3].ptr = tvb_get_ptr(tvb, offset, len);
      cksum_vec[3].len = reported_len;
      computed_cksum = in_cksum(&cksum_vec[0], 4);
      if (computed_cksum == 0) {
        proto_tree_add_uint_format(udp_tree, hf_udp_checksum, tvb,
          offset + 6, 2, uh_sum, "Checksum: 0x%04x (correct)", uh_sum);
      } else {
	proto_tree_add_boolean_hidden(udp_tree, hf_udp_checksum_bad, tvb,
	   offset + 6, 2, TRUE);
        proto_tree_add_uint_format(udp_tree, hf_udp_checksum, tvb,
          offset + 6, 2, uh_sum,
	  "Checksum: 0x%04x (incorrect, should be 0x%04x)", uh_sum,
	   in_cksum_shouldbe(uh_sum, computed_cksum));
      }
    } else {
      proto_tree_add_uint_format(udp_tree, hf_udp_checksum, tvb,
        offset + 6, 2, uh_sum, "Checksum: 0x%04x", uh_sum);
    }
  }

  /* Skip over header */
  offset += 8;

  pinfo->ptype = PT_UDP;
  pinfo->srcport = uh_sport;
  pinfo->destport = uh_dport;

/* call sub-dissectors */
  decode_udp_ports( tvb, offset, pinfo, tree, uh_sport, uh_dport);

}

void
proto_register_udp(void)
{
	module_t *udp_module;
	static hf_register_info hf[] = {
		{ &hf_udp_srcport,
		{ "Source Port",	"udp.srcport", FT_UINT16, BASE_DEC, NULL, 0x0,
			"", HFILL }},

		{ &hf_udp_dstport,
		{ "Destination Port",	"udp.dstport", FT_UINT16, BASE_DEC, NULL, 0x0,
			"", HFILL }},

		{ &hf_udp_port,
		{ "Source or Destination Port",	"udp.port", FT_UINT16, BASE_DEC,  NULL, 0x0,
			"", HFILL }},

		{ &hf_udp_length,
		{ "Length",		"udp.length", FT_UINT16, BASE_DEC, NULL, 0x0,
			"", HFILL }},

		{ &hf_udp_checksum_bad,
		{ "Bad Checksum",	"udp.checksum_bad", FT_BOOLEAN, BASE_NONE, NULL, 0x0,
			"", HFILL }},

		{ &hf_udp_checksum,
		{ "Checksum",		"udp.checksum", FT_UINT16, BASE_HEX, NULL, 0x0,
			"", HFILL }},
	};
	static gint *ett[] = {
		&ett_udp,
	};

	proto_udp = proto_register_protocol("User Datagram Protocol",
	    "UDP", "udp");
	proto_register_field_array(proto_udp, hf, array_length(hf));
	proto_register_subtree_array(ett, array_length(ett));

/* subdissector code */
	udp_dissector_table = register_dissector_table("udp.port",
	    "UDP port", FT_UINT16, BASE_DEC);
	register_heur_dissector_list("udp", &heur_subdissector_list);
	
	/* Register configuration preferences */
	udp_module = prefs_register_protocol(proto_udp, NULL);
	prefs_register_bool_preference(udp_module, "udp_summary_in_tree",
	"Show UDP summary in protocol tree", 
	"Whether the UDP summary line should be shown in the protocol tree",
	&udp_summary_in_tree);
}

void
proto_reg_handoff_udp(void)
{
	dissector_handle_t udp_handle;

	udp_handle = create_dissector_handle(dissect_udp, proto_udp);
	dissector_add("ip.proto", IP_PROTO_UDP, udp_handle);
	data_handle = find_dissector("data");
}