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/* packet-tcp.c
* Routines for TCP packet disassembly
*
* $Id: packet-tcp.c,v 1.83 2000/09/14 21:58:48 gram Exp $
*
* Ethereal - Network traffic analyzer
* By Gerald Combs <gerald@zing.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.
*/
#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 <glib.h>
#ifdef NEED_SNPRINTF_H
# include "snprintf.h"
#endif
#include "globals.h"
#include "resolv.h"
#include "follow.h"
#include "prefs.h"
#include "plugins.h"
#include "packet-tcp.h"
#include "packet-ip.h"
#include "conversation.h"
#include "strutil.h"
/* Place TCP summary in proto tree */
gboolean g_tcp_summary_in_tree = TRUE;
extern FILE* data_out_file;
guint16 tcp_urgent_pointer;
static gchar info_str[COL_MAX_LEN];
static int info_len;
static int proto_tcp = -1;
static int hf_tcp_srcport = -1;
static int hf_tcp_dstport = -1;
static int hf_tcp_port = -1;
static int hf_tcp_seq = -1;
static int hf_tcp_ack = -1;
static int hf_tcp_hdr_len = -1;
static int hf_tcp_flags = -1;
static int hf_tcp_flags_cwr = -1;
static int hf_tcp_flags_ecn = -1;
static int hf_tcp_flags_urg = -1;
static int hf_tcp_flags_ack = -1;
static int hf_tcp_flags_push = -1;
static int hf_tcp_flags_reset = -1;
static int hf_tcp_flags_syn = -1;
static int hf_tcp_flags_fin = -1;
static int hf_tcp_window_size = -1;
static int hf_tcp_checksum = -1;
static int hf_tcp_urgent_pointer = -1;
static gint ett_tcp = -1;
static gint ett_tcp_flags = -1;
static gint ett_tcp_options = -1;
static gint ett_tcp_option_sack = -1;
static dissector_table_t subdissector_table;
static heur_dissector_list_t heur_subdissector_list;
/* TCP Ports */
#define TCP_PORT_SMTP 25
/* TCP structs and definitions */
typedef struct _e_tcphdr {
guint16 th_sport;
guint16 th_dport;
guint32 th_seq;
guint32 th_ack;
guint8 th_off_x2; /* combines th_off and th_x2 */
guint8 th_flags;
#define TH_FIN 0x01
#define TH_SYN 0x02
#define TH_RST 0x04
#define TH_PUSH 0x08
#define TH_ACK 0x10
#define TH_URG 0x20
#define TH_ECN 0x40
#define TH_CWR 0x80
guint16 th_win;
guint16 th_sum;
guint16 th_urp;
} e_tcphdr;
/*
* TCP option
*/
#define TCPOPT_NOP 1 /* Padding */
#define TCPOPT_EOL 0 /* End of options */
#define TCPOPT_MSS 2 /* Segment size negotiating */
#define TCPOPT_WINDOW 3 /* Window scaling */
#define TCPOPT_SACK_PERM 4 /* SACK Permitted */
#define TCPOPT_SACK 5 /* SACK Block */
#define TCPOPT_ECHO 6
#define TCPOPT_ECHOREPLY 7
#define TCPOPT_TIMESTAMP 8 /* Better RTT estimations/PAWS */
#define TCPOPT_CC 11
#define TCPOPT_CCNEW 12
#define TCPOPT_CCECHO 13
/*
* TCP option lengths
*/
#define TCPOLEN_MSS 4
#define TCPOLEN_WINDOW 3
#define TCPOLEN_SACK_PERM 2
#define TCPOLEN_SACK_MIN 2
#define TCPOLEN_ECHO 6
#define TCPOLEN_ECHOREPLY 6
#define TCPOLEN_TIMESTAMP 10
#define TCPOLEN_CC 6
#define TCPOLEN_CCNEW 6
#define TCPOLEN_CCECHO 6
static void
tcp_info_append_uint(const char *abbrev, guint32 val) {
int add_len = 0;
if (info_len > 0)
if(info_len > 0)
add_len = snprintf(&info_str[info_len], COL_MAX_LEN - info_len, " %s=%u",
abbrev, val);
if (add_len > 0)
info_len += add_len;
}
static void
dissect_tcpopt_maxseg(const ip_tcp_opt *optp, const u_char *opd,
int offset, guint optlen, proto_tree *opt_tree)
{
proto_tree_add_text(opt_tree, NullTVB, offset, optlen,
"%s: %u bytes", optp->name, pntohs(opd));
tcp_info_append_uint("MSS", pntohs(opd));
}
static void
dissect_tcpopt_wscale(const ip_tcp_opt *optp, const u_char *opd,
int offset, guint optlen, proto_tree *opt_tree)
{
proto_tree_add_text(opt_tree, NullTVB, offset, optlen,
"%s: %u bytes", optp->name, *opd);
tcp_info_append_uint("WS", *opd);
}
static void
dissect_tcpopt_sack(const ip_tcp_opt *optp, const u_char *opd,
int offset, guint optlen, proto_tree *opt_tree)
{
proto_tree *field_tree = NULL;
proto_item *tf;
guint leftedge, rightedge;
tf = proto_tree_add_text(opt_tree, NullTVB, offset, optlen, "%s:", optp->name);
offset += 2; /* skip past type and length */
optlen -= 2; /* subtract size of type and length */
while (optlen > 0) {
if (field_tree == NULL) {
/* Haven't yet made a subtree out of this option. Do so. */
field_tree = proto_item_add_subtree(tf, *optp->subtree_index);
}
if (optlen < 4) {
proto_tree_add_text(field_tree, NullTVB, offset, optlen,
"(suboption would go past end of option)");
break;
}
/* XXX - check whether it goes past end of packet */
leftedge = pntohl(opd);
opd += 4;
optlen -= 4;
if (optlen < 4) {
proto_tree_add_text(field_tree, NullTVB, offset, optlen,
"(suboption would go past end of option)");
break;
}
/* XXX - check whether it goes past end of packet */
rightedge = pntohl(opd);
opd += 4;
optlen -= 4;
proto_tree_add_text(field_tree, NullTVB, offset, 8,
"left edge = %u, right edge = %u", leftedge, rightedge);
tcp_info_append_uint("SLE", leftedge);
tcp_info_append_uint("SRE", rightedge);
offset += 8;
}
}
static void
dissect_tcpopt_echo(const ip_tcp_opt *optp, const u_char *opd,
int offset, guint optlen, proto_tree *opt_tree)
{
proto_tree_add_text(opt_tree, NullTVB, offset, optlen,
"%s: %u", optp->name, pntohl(opd));
tcp_info_append_uint("ECHO", pntohl(opd));
}
static void
dissect_tcpopt_timestamp(const ip_tcp_opt *optp, const u_char *opd,
int offset, guint optlen, proto_tree *opt_tree)
{
proto_tree_add_text(opt_tree, NullTVB, offset, optlen,
"%s: tsval %u, tsecr %u", optp->name, pntohl(opd), pntohl(opd + 4));
tcp_info_append_uint("TSV", pntohl(opd));
tcp_info_append_uint("TSER", pntohl(opd + 4));
}
static void
dissect_tcpopt_cc(const ip_tcp_opt *optp, const u_char *opd,
int offset, guint optlen, proto_tree *opt_tree)
{
proto_tree_add_text(opt_tree, NullTVB, offset, optlen,
"%s: %u", optp->name, pntohl(opd));
tcp_info_append_uint("CC", pntohl(opd));
}
static const ip_tcp_opt tcpopts[] = {
{
TCPOPT_EOL,
"EOL",
NULL,
NO_LENGTH,
0,
NULL,
},
{
TCPOPT_NOP,
"NOP",
NULL,
NO_LENGTH,
0,
NULL,
},
{
TCPOPT_MSS,
"Maximum segment size",
NULL,
FIXED_LENGTH,
TCPOLEN_MSS,
dissect_tcpopt_maxseg
},
{
TCPOPT_WINDOW,
"Window scale",
NULL,
FIXED_LENGTH,
TCPOLEN_WINDOW,
dissect_tcpopt_wscale
},
{
TCPOPT_SACK_PERM,
"SACK permitted",
NULL,
FIXED_LENGTH,
TCPOLEN_SACK_PERM,
NULL,
},
{
TCPOPT_SACK,
"SACK",
&ett_tcp_option_sack,
VARIABLE_LENGTH,
TCPOLEN_SACK_MIN,
dissect_tcpopt_sack
},
{
TCPOPT_ECHO,
"Echo",
NULL,
FIXED_LENGTH,
TCPOLEN_ECHO,
dissect_tcpopt_echo
},
{
TCPOPT_ECHOREPLY,
"Echo reply",
NULL,
FIXED_LENGTH,
TCPOLEN_ECHOREPLY,
dissect_tcpopt_echo
},
{
TCPOPT_TIMESTAMP,
"Time stamp",
NULL,
FIXED_LENGTH,
TCPOLEN_TIMESTAMP,
dissect_tcpopt_timestamp
},
{
TCPOPT_CC,
"CC",
NULL,
FIXED_LENGTH,
TCPOLEN_CC,
dissect_tcpopt_cc
},
{
TCPOPT_CCNEW,
"CC.NEW",
NULL,
FIXED_LENGTH,
TCPOPT_CCNEW,
dissect_tcpopt_cc
},
{
TCPOPT_CCECHO,
"CC.ECHO",
NULL,
FIXED_LENGTH,
TCPOLEN_CCECHO,
dissect_tcpopt_cc
}
};
#define N_TCP_OPTS (sizeof tcpopts / sizeof tcpopts[0])
/* TCP flags flag */
static const true_false_string flags_set_truth = {
"Set",
"Not set"
};
/* 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_tcp_ports(const u_char *pd, int offset, frame_data *fd, proto_tree *tree,
int src_port, int dst_port)
{
/* determine if this packet is part of a conversation and call dissector */
/* for the conversation if available */
if (old_try_conversation_dissector(&pi.src, &pi.dst, PT_TCP,
src_port, dst_port, pd, offset, fd, tree))
return;
/* try to apply the plugins */
#ifdef HAVE_PLUGINS
{
plugin *pt_plug = plugin_list;
if (enabled_plugins_number > 0) {
while (pt_plug) {
if (pt_plug->enabled && !strcmp(pt_plug->protocol, "tcp") &&
tree && dfilter_apply(pt_plug->filter, tree, pd, fd->cap_len)) {
pt_plug->dissector(pd, offset, fd, tree);
return;
}
pt_plug = pt_plug->next;
}
}
}
#endif
/* do lookup with the subdissector table */
if (old_dissector_try_port(subdissector_table, src_port, pd, offset, fd, tree) ||
old_dissector_try_port(subdissector_table, dst_port, pd, offset, fd, tree))
return;
/* do lookup with the heuristic subdissector table */
if (old_dissector_try_heuristic(heur_subdissector_list, pd, offset, fd, tree))
return;
/* Oh, well, we don't know this; dissect it as data. */
old_dissect_data(pd, offset, fd, tree);
}
static void
dissect_tcp(const u_char *pd, int offset, frame_data *fd, proto_tree *tree) {
e_tcphdr th;
proto_tree *tcp_tree = NULL, *field_tree = NULL;
proto_item *ti, *tf;
gchar flags[64] = "<None>";
gchar *fstr[] = {"FIN", "SYN", "RST", "PSH", "ACK", "URG", "ECN", "CWR" };
gint fpos = 0, i;
guint bpos;
guint hlen;
guint optlen;
guint packet_max = pi.len;
OLD_CHECK_DISPLAY_AS_DATA(proto_tcp, pd, offset, fd, tree);
/* To do: Check for {cap len,pkt len} < struct len */
/* Avoids alignment problems on many architectures. */
memcpy(&th, &pd[offset], sizeof(e_tcphdr));
th.th_sport = ntohs(th.th_sport);
th.th_dport = ntohs(th.th_dport);
th.th_win = ntohs(th.th_win);
th.th_sum = ntohs(th.th_sum);
th.th_urp = ntohs(th.th_urp);
th.th_seq = ntohl(th.th_seq);
th.th_ack = ntohl(th.th_ack);
/* Export the urgent pointer, for the benefit of protocols such as
rlogin. */
tcp_urgent_pointer = th.th_urp;
info_len = 0;
if (check_col(fd, COL_PROTOCOL) || tree) {
for (i = 0; i < 8; i++) {
bpos = 1 << i;
if (th.th_flags & bpos) {
if (fpos) {
strcpy(&flags[fpos], ", ");
fpos += 2;
}
strcpy(&flags[fpos], fstr[i]);
fpos += 3;
}
}
flags[fpos] = '\0';
}
hlen = hi_nibble(th.th_off_x2) * 4; /* TCP header length, in bytes */
if (check_col(fd, COL_PROTOCOL))
col_add_str(fd, COL_PROTOCOL, "TCP");
if (check_col(fd, COL_INFO)) {
/* Copy the data into info_str in case one of the option handling
routines needs to append to it. */
if (th.th_flags & TH_URG)
info_len = snprintf(info_str, COL_MAX_LEN, "%s > %s [%s] Seq=%u Ack=%u Win=%u Urg=%u Len=%d",
get_tcp_port(th.th_sport), get_tcp_port(th.th_dport), flags,
th.th_seq, th.th_ack, th.th_win, th.th_urp, pi.len - offset - hlen);
else
info_len = snprintf(info_str, COL_MAX_LEN, "%s > %s [%s] Seq=%u Ack=%u Win=%u Len=%d",
get_tcp_port(th.th_sport), get_tcp_port(th.th_dport), flags,
th.th_seq, th.th_ack, th.th_win, pi.len - offset - hlen);
/* The info column is actually written after the options are decoded */
}
if (tree) {
if (g_tcp_summary_in_tree) {
ti = proto_tree_add_protocol_format(tree, proto_tcp, NullTVB, offset, hlen, "Transmission Control Protocol, Src Port: %s (%u), Dst Port: %s (%u), Seq: %u, Ack: %u", get_tcp_port(th.th_sport), th.th_sport, get_tcp_port(th.th_dport), th.th_dport, th.th_seq, th.th_ack);
}
else {
ti = proto_tree_add_item(tree, proto_tcp, NullTVB, offset, hlen, FALSE);
}
tcp_tree = proto_item_add_subtree(ti, ett_tcp);
proto_tree_add_uint_format(tcp_tree, hf_tcp_srcport, NullTVB, offset, 2, th.th_sport,
"Source port: %s (%u)", get_tcp_port(th.th_sport), th.th_sport);
proto_tree_add_uint_format(tcp_tree, hf_tcp_dstport, NullTVB, offset + 2, 2, th.th_dport,
"Destination port: %s (%u)", get_tcp_port(th.th_dport), th.th_dport);
proto_tree_add_uint_hidden(tcp_tree, hf_tcp_port, NullTVB, offset, 2, th.th_sport);
proto_tree_add_uint_hidden(tcp_tree, hf_tcp_port, NullTVB, offset + 2, 2, th.th_dport);
proto_tree_add_uint(tcp_tree, hf_tcp_seq, NullTVB, offset + 4, 4, th.th_seq);
if (th.th_flags & TH_ACK)
proto_tree_add_uint(tcp_tree, hf_tcp_ack, NullTVB, offset + 8, 4, th.th_ack);
proto_tree_add_uint_format(tcp_tree, hf_tcp_hdr_len, NullTVB, offset + 12, 1, hlen,
"Header length: %u bytes", hlen);
tf = proto_tree_add_uint_format(tcp_tree, hf_tcp_flags, NullTVB, offset + 13, 1,
th.th_flags, "Flags: 0x%04x (%s)", th.th_flags, flags);
field_tree = proto_item_add_subtree(tf, ett_tcp_flags);
proto_tree_add_boolean(field_tree, hf_tcp_flags_cwr, NullTVB, offset + 13, 1, th.th_flags);
proto_tree_add_boolean(field_tree, hf_tcp_flags_ecn, NullTVB, offset + 13, 1, th.th_flags);
proto_tree_add_boolean(field_tree, hf_tcp_flags_urg, NullTVB, offset + 13, 1, th.th_flags);
proto_tree_add_boolean(field_tree, hf_tcp_flags_ack, NullTVB, offset + 13, 1, th.th_flags);
proto_tree_add_boolean(field_tree, hf_tcp_flags_push, NullTVB, offset + 13, 1, th.th_flags);
proto_tree_add_boolean(field_tree, hf_tcp_flags_reset, NullTVB, offset + 13, 1, th.th_flags);
proto_tree_add_boolean(field_tree, hf_tcp_flags_syn, NullTVB, offset + 13, 1, th.th_flags);
proto_tree_add_boolean(field_tree, hf_tcp_flags_fin, NullTVB, offset + 13, 1, th.th_flags);
proto_tree_add_uint(tcp_tree, hf_tcp_window_size, NullTVB, offset + 14, 2, th.th_win);
proto_tree_add_uint(tcp_tree, hf_tcp_checksum, NullTVB, offset + 16, 2, th.th_sum);
if (th.th_flags & TH_URG)
proto_tree_add_uint(tcp_tree, hf_tcp_urgent_pointer, NullTVB, offset + 18, 2, th.th_urp);
}
/* Decode TCP options, if any. */
if (tree && hlen > sizeof (e_tcphdr)) {
/* There's more than just the fixed-length header. Decode the
options. */
optlen = hlen - sizeof (e_tcphdr); /* length of options, in bytes */
tf = proto_tree_add_text(tcp_tree, NullTVB, offset + 20, optlen,
"Options: (%d bytes)", optlen);
field_tree = proto_item_add_subtree(tf, ett_tcp_options);
dissect_ip_tcp_options(&pd[offset + 20], offset + 20, optlen,
tcpopts, N_TCP_OPTS, TCPOPT_EOL, field_tree);
}
if (check_col(fd, COL_INFO))
col_add_str(fd, COL_INFO, info_str);
/* Skip over header + options */
offset += hlen;
pi.ptype = PT_TCP;
pi.srcport = th.th_sport;
pi.destport = th.th_dport;
/* Check the packet length to see if there's more data
(it could be an ACK-only packet) */
if (packet_max > offset) {
if (th.th_flags & TH_RST) {
/*
* RFC1122 says:
*
* 4.2.2.12 RST Segment: RFC-793 Section 3.4
*
* A TCP SHOULD allow a received RST segment to include data.
*
* DISCUSSION
* It has been suggested that a RST segment could contain
* ASCII text that encoded and explained the cause of the
* RST. No standard has yet been established for such
* data.
*
* so for segments with RST we just display the data as text.
*/
proto_tree_add_text(tcp_tree, NullTVB, offset, END_OF_FRAME,
"Reset cause: %s",
format_text(&pd[offset], END_OF_FRAME));
} else
decode_tcp_ports( pd, offset, fd, tree, th.th_sport, th.th_dport);
}
if( data_out_file ) {
reassemble_tcp( th.th_seq, /* sequence number */
( pi.len - offset ), /* data length */
( pd+offset ), /* data */
( pi.captured_len - offset ), /* captured data length */
( th.th_flags & TH_SYN ), /* is syn set? */
&pi.net_src,
&pi.net_dst,
pi.srcport,
pi.destport);
}
}
void
proto_register_tcp(void)
{
static hf_register_info hf[] = {
{ &hf_tcp_srcport,
{ "Source Port", "tcp.srcport", FT_UINT16, BASE_DEC, NULL, 0x0,
"" }},
{ &hf_tcp_dstport,
{ "Destination Port", "tcp.dstport", FT_UINT16, BASE_DEC, NULL, 0x0,
"" }},
{ &hf_tcp_port,
{ "Source or Destination Port", "tcp.port", FT_UINT16, BASE_DEC, NULL, 0x0,
"" }},
{ &hf_tcp_seq,
{ "Sequence number", "tcp.seq", FT_UINT32, BASE_DEC, NULL, 0x0,
"" }},
{ &hf_tcp_ack,
{ "Acknowledgement number", "tcp.ack", FT_UINT32, BASE_DEC, NULL, 0x0,
"" }},
{ &hf_tcp_hdr_len,
{ "Header Length", "tcp.hdr_len", FT_UINT8, BASE_DEC, NULL, 0x0,
"" }},
{ &hf_tcp_flags,
{ "Flags", "tcp.flags", FT_UINT8, BASE_HEX, NULL, 0x0,
"" }},
{ &hf_tcp_flags_cwr,
{ "Congestion Window Reduced (CWR)", "tcp.flags.cwr", FT_BOOLEAN, 8, TFS(&flags_set_truth), TH_CWR,
"" }},
{ &hf_tcp_flags_ecn,
{ "ECN-Echo", "tcp.flags.ecn", FT_BOOLEAN, 8, TFS(&flags_set_truth), TH_ECN,
"" }},
{ &hf_tcp_flags_urg,
{ "Urgent", "tcp.flags.urg", FT_BOOLEAN, 8, TFS(&flags_set_truth), TH_URG,
"" }},
{ &hf_tcp_flags_ack,
{ "Acknowledgment", "tcp.flags.ack", FT_BOOLEAN, 8, TFS(&flags_set_truth), TH_ACK,
"" }},
{ &hf_tcp_flags_push,
{ "Push", "tcp.flags.push", FT_BOOLEAN, 8, TFS(&flags_set_truth), TH_PUSH,
"" }},
{ &hf_tcp_flags_reset,
{ "Reset", "tcp.flags.reset", FT_BOOLEAN, 8, TFS(&flags_set_truth), TH_RST,
"" }},
{ &hf_tcp_flags_syn,
{ "Syn", "tcp.flags.syn", FT_BOOLEAN, 8, TFS(&flags_set_truth), TH_SYN,
"" }},
{ &hf_tcp_flags_fin,
{ "Fin", "tcp.flags.fin", FT_BOOLEAN, 8, TFS(&flags_set_truth), TH_FIN,
"" }},
{ &hf_tcp_window_size,
{ "Window size", "tcp.window_size", FT_UINT16, BASE_DEC, NULL, 0x0,
"" }},
{ &hf_tcp_checksum,
{ "Checksum", "tcp.checksum", FT_UINT16, BASE_HEX, NULL, 0x0,
"" }},
{ &hf_tcp_urgent_pointer,
{ "Urgent pointer", "tcp.urgent_pointer", FT_UINT16, BASE_DEC, NULL, 0x0,
"" }},
};
static gint *ett[] = {
&ett_tcp,
&ett_tcp_flags,
&ett_tcp_options,
&ett_tcp_option_sack,
};
module_t *tcp_module;
proto_tcp = proto_register_protocol ("Transmission Control Protocol", "tcp");
proto_register_field_array(proto_tcp, hf, array_length(hf));
proto_register_subtree_array(ett, array_length(ett));
/* subdissector code */
subdissector_table = register_dissector_table("tcp.port");
register_heur_dissector_list("tcp", &heur_subdissector_list);
/* Register a configuration preferences */
tcp_module = prefs_register_module("tcp", "TCP", NULL);
prefs_register_bool_preference(tcp_module, "tcp_summary_in_tree",
"Show TCP summary in protocol tree",
"Whether the TCP summary line should be shown in the protocol tree",
&g_tcp_summary_in_tree);
}
void
proto_reg_handoff_tcp(void)
{
old_dissector_add("ip.proto", IP_PROTO_TCP, dissect_tcp);
}
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