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wireshark/packet-udp.c

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/* packet-udp.c
* Routines for UDP packet disassembly
*
* $Id: packet-udp.c,v 1.112 2004/01/22 20:43:17 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
#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>
#include "tap.h"
static int udp_tap = -1;
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;
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 */
static gboolean try_heuristic_first = FALSE;
void
decode_udp_ports(tvbuff_t *tvb, int offset, packet_info *pinfo,
proto_tree *tree, int uh_sport, int uh_dport, int uh_ulen)
{
tvbuff_t *next_tvb;
int low_port, high_port;
gint len, reported_len;
len = tvb_length_remaining(tvb, offset);
reported_len = tvb_reported_length_remaining(tvb, offset);
if (uh_ulen != -1) {
/* This is the length from the UDP header; the payload should be cut
off at that length.
XXX - what if it's *greater* than the reported length? */
if (uh_ulen < len)
len = uh_ulen;
if (uh_ulen < reported_len)
reported_len = uh_ulen;
}
next_tvb = tvb_new_subset(tvb, offset, len, reported_len);
/* 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;
if (try_heuristic_first) {
/* do lookup with the heuristic subdissector table */
if (dissector_try_heuristic(heur_subdissector_list, 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;
if (!try_heuristic_first) {
/* 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)
{
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;
static e_udphdr udphstruct[4], *udph;
static int udph_count=0;
udph_count++;
if(udph_count>=4){
udph_count=0;
}
udph=&udphstruct[udph_count];
SET_ADDRESS(&udph->ip_src, pinfo->src.type, pinfo->src.len, pinfo->src.data);
SET_ADDRESS(&udph->ip_dst, pinfo->dst.type, pinfo->dst.len, pinfo->dst.data);
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);
udph->uh_sport=tvb_get_ntohs(tvb, offset);
udph->uh_dport=tvb_get_ntohs(tvb, offset+2);
udph->uh_ulen=tvb_get_ntohs(tvb, offset+4);
udph->uh_sum=tvb_get_ntohs(tvb, offset+6);
if (check_col(pinfo->cinfo, COL_INFO))
col_add_fstr(pinfo->cinfo, COL_INFO, "Source port: %s Destination port: %s",
get_udp_port(udph->uh_sport), get_udp_port(udph->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(udph->uh_sport), udph->uh_sport, get_udp_port(udph->uh_dport), udph->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, udph->uh_sport,
"Source port: %s (%u)", get_udp_port(udph->uh_sport), udph->uh_sport);
proto_tree_add_uint_format(udp_tree, hf_udp_dstport, tvb, offset + 2, 2, udph->uh_dport,
"Destination port: %s (%u)", get_udp_port(udph->uh_dport), udph->uh_dport);
proto_tree_add_uint_hidden(udp_tree, hf_udp_port, tvb, offset, 2, udph->uh_sport);
proto_tree_add_uint_hidden(udp_tree, hf_udp_port, tvb, offset+2, 2, udph->uh_dport);
if (udph->uh_ulen < 8) {
/* Bogus length - it includes the header, so it must be >= 8. */
proto_tree_add_uint_format(udp_tree, hf_udp_length, tvb, offset + 4, 2,
udph->uh_ulen, "Length: %u (bogus, must be >= 8)", udph->uh_ulen);
return;
}
proto_tree_add_uint(udp_tree, hf_udp_length, tvb, offset + 4, 2, udph->uh_ulen);
reported_len = tvb_reported_length(tvb);
len = tvb_length(tvb);
if (udph->uh_sum == 0) {
/* No checksum supplied in the packet. */
proto_tree_add_uint_format(udp_tree, hf_udp_checksum, tvb,
offset + 6, 2, udph->uh_sum, "Checksum: 0x%04x (none)", udph->uh_sum);
} else if (!pinfo->fragmented && len >= reported_len &&
len >= udph->uh_ulen && reported_len >= udph->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] = g_htonl((IP_PROTO_UDP<<16) + udph->uh_ulen);
cksum_vec[2].len = 4;
break;
case AT_IPv6:
phdr[0] = g_htonl(udph->uh_ulen);
phdr[1] = g_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, udph->uh_ulen);
cksum_vec[3].len = udph->uh_ulen;
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, udph->uh_sum, "Checksum: 0x%04x (correct)", udph->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, udph->uh_sum,
"Checksum: 0x%04x (incorrect, should be 0x%04x)", udph->uh_sum,
in_cksum_shouldbe(udph->uh_sum, computed_cksum));
}
} else {
proto_tree_add_uint_format(udp_tree, hf_udp_checksum, tvb,
offset + 6, 2, udph->uh_sum, "Checksum: 0x%04x", udph->uh_sum);
}
}
/* Skip over header */
offset += 8;
pinfo->ptype = PT_UDP;
pinfo->srcport = udph->uh_sport;
pinfo->destport = udph->uh_dport;
tap_queue_packet(udp_tap, pinfo, udph);
/*
* Call sub-dissectors.
*
* XXX - should we do this if this is included in an error packet?
* It might be nice to see the details of the packet that caused the
* ICMP error, but it might not be nice to have the dissector update
* state based on it.
* Also, we probably don't want to run UDP taps on those packets.
*
* We definitely don't want to do it for an error packet if there's
* nothing left in the packet.
*/
if (!pinfo->in_error_pkt || tvb_length_remaining(tvb, offset) > 0)
decode_udp_ports(tvb, offset, pinfo, tree, udph->uh_sport, udph->uh_dport,
udph->uh_ulen);
}
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, "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);
prefs_register_bool_preference(udp_module, "try_heuristic_first",
"Try heuristic sub-dissectors first",
"Try to decode a packet using an heuristic sub-dissector before using a sub-dissector registered to a specific port",
&try_heuristic_first);
}
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");
udp_tap = register_tap("udp");
}
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