2 * Routines for TCP packet disassembly
4 * $Id: packet-tcp.c,v 1.91 2000/12/04 06:37:44 guy Exp $
6 * Ethereal - Network traffic analyzer
7 * By Gerald Combs <gerald@zing.org>
8 * Copyright 1998 Gerald Combs
11 * This program is free software; you can redistribute it and/or
12 * modify it under the terms of the GNU General Public License
13 * as published by the Free Software Foundation; either version 2
14 * of the License, or (at your option) any later version.
16 * This program is distributed in the hope that it will be useful,
17 * but WITHOUT ANY WARRANTY; without even the implied warranty of
18 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
19 * GNU General Public License for more details.
21 * You should have received a copy of the GNU General Public License
22 * along with this program; if not, write to the Free Software
23 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
30 #ifdef HAVE_SYS_TYPES_H
31 # include <sys/types.h>
34 #ifdef HAVE_NETINET_IN_H
35 # include <netinet/in.h>
42 #ifdef NEED_SNPRINTF_H
43 # include "snprintf.h"
51 #include "packet-tcp.h"
52 #include "packet-ip.h"
53 #include "conversation.h"
56 /* Place TCP summary in proto tree */
57 gboolean g_tcp_summary_in_tree = TRUE;
59 extern FILE* data_out_file;
61 guint16 tcp_urgent_pointer;
63 static int proto_tcp = -1;
64 static int hf_tcp_srcport = -1;
65 static int hf_tcp_dstport = -1;
66 static int hf_tcp_port = -1;
67 static int hf_tcp_seq = -1;
68 static int hf_tcp_nxtseq = -1;
69 static int hf_tcp_ack = -1;
70 static int hf_tcp_hdr_len = -1;
71 static int hf_tcp_flags = -1;
72 static int hf_tcp_flags_cwr = -1;
73 static int hf_tcp_flags_ecn = -1;
74 static int hf_tcp_flags_urg = -1;
75 static int hf_tcp_flags_ack = -1;
76 static int hf_tcp_flags_push = -1;
77 static int hf_tcp_flags_reset = -1;
78 static int hf_tcp_flags_syn = -1;
79 static int hf_tcp_flags_fin = -1;
80 static int hf_tcp_window_size = -1;
81 static int hf_tcp_checksum = -1;
82 static int hf_tcp_urgent_pointer = -1;
84 static gint ett_tcp = -1;
85 static gint ett_tcp_flags = -1;
86 static gint ett_tcp_options = -1;
87 static gint ett_tcp_option_sack = -1;
89 static dissector_table_t subdissector_table;
90 static heur_dissector_list_t heur_subdissector_list;
94 #define TCP_PORT_SMTP 25
96 /* TCP structs and definitions */
98 typedef struct _e_tcphdr {
103 guint8 th_off_x2; /* combines th_off and th_x2 */
122 #define TCPOPT_NOP 1 /* Padding */
123 #define TCPOPT_EOL 0 /* End of options */
124 #define TCPOPT_MSS 2 /* Segment size negotiating */
125 #define TCPOPT_WINDOW 3 /* Window scaling */
126 #define TCPOPT_SACK_PERM 4 /* SACK Permitted */
127 #define TCPOPT_SACK 5 /* SACK Block */
128 #define TCPOPT_ECHO 6
129 #define TCPOPT_ECHOREPLY 7
130 #define TCPOPT_TIMESTAMP 8 /* Better RTT estimations/PAWS */
132 #define TCPOPT_CCNEW 12
133 #define TCPOPT_CCECHO 13
139 #define TCPOLEN_MSS 4
140 #define TCPOLEN_WINDOW 3
141 #define TCPOLEN_SACK_PERM 2
142 #define TCPOLEN_SACK_MIN 2
143 #define TCPOLEN_ECHO 6
144 #define TCPOLEN_ECHOREPLY 6
145 #define TCPOLEN_TIMESTAMP 10
147 #define TCPOLEN_CCNEW 6
148 #define TCPOLEN_CCECHO 6
151 tcp_info_append_uint(frame_data *fd, const char *abbrev, guint32 val)
153 if (check_col(fd, COL_INFO))
154 col_append_fstr(fd, COL_INFO, " %s=%u", abbrev, val);
158 dissect_tcpopt_maxseg(const ip_tcp_opt *optp, tvbuff_t *tvb,
159 int offset, guint optlen, frame_data *fd, proto_tree *opt_tree)
163 mss = tvb_get_ntohs(tvb, offset + 2);
164 proto_tree_add_text(opt_tree, tvb, offset, optlen,
165 "%s: %u bytes", optp->name, mss);
166 tcp_info_append_uint(fd, "MSS", mss);
170 dissect_tcpopt_wscale(const ip_tcp_opt *optp, tvbuff_t *tvb,
171 int offset, guint optlen, frame_data *fd, proto_tree *opt_tree)
175 ws = tvb_get_guint8(tvb, offset + 2);
176 proto_tree_add_text(opt_tree, tvb, offset, optlen,
177 "%s: %u bytes", optp->name, ws);
178 tcp_info_append_uint(fd, "WS", ws);
182 dissect_tcpopt_sack(const ip_tcp_opt *optp, tvbuff_t *tvb,
183 int offset, guint optlen, frame_data *fd, proto_tree *opt_tree)
185 proto_tree *field_tree = NULL;
187 guint leftedge, rightedge;
189 tf = proto_tree_add_text(opt_tree, tvb, offset, optlen, "%s:", optp->name);
190 offset += 2; /* skip past type and length */
191 optlen -= 2; /* subtract size of type and length */
193 if (field_tree == NULL) {
194 /* Haven't yet made a subtree out of this option. Do so. */
195 field_tree = proto_item_add_subtree(tf, *optp->subtree_index);
198 proto_tree_add_text(field_tree, tvb, offset, optlen,
199 "(suboption would go past end of option)");
202 leftedge = tvb_get_ntohl(tvb, offset);
205 proto_tree_add_text(field_tree, tvb, offset, optlen,
206 "(suboption would go past end of option)");
209 /* XXX - check whether it goes past end of packet */
210 rightedge = tvb_get_ntohl(tvb, offset + 4);
212 proto_tree_add_text(field_tree, tvb, offset, 8,
213 "left edge = %u, right edge = %u", leftedge, rightedge);
214 tcp_info_append_uint(fd, "SLE", leftedge);
215 tcp_info_append_uint(fd, "SRE", rightedge);
221 dissect_tcpopt_echo(const ip_tcp_opt *optp, tvbuff_t *tvb,
222 int offset, guint optlen, frame_data *fd, proto_tree *opt_tree)
226 echo = tvb_get_ntohl(tvb, offset + 2);
227 proto_tree_add_text(opt_tree, tvb, offset, optlen,
228 "%s: %u", optp->name, echo);
229 tcp_info_append_uint(fd, "ECHO", echo);
233 dissect_tcpopt_timestamp(const ip_tcp_opt *optp, tvbuff_t *tvb,
234 int offset, guint optlen, frame_data *fd, proto_tree *opt_tree)
238 tsv = tvb_get_ntohl(tvb, offset + 2);
239 tser = tvb_get_ntohl(tvb, offset + 6);
240 proto_tree_add_text(opt_tree, tvb, offset, optlen,
241 "%s: tsval %u, tsecr %u", optp->name, tsv, tser);
242 tcp_info_append_uint(fd, "TSV", tsv);
243 tcp_info_append_uint(fd, "TSER", tser);
247 dissect_tcpopt_cc(const ip_tcp_opt *optp, tvbuff_t *tvb,
248 int offset, guint optlen, frame_data *fd, proto_tree *opt_tree)
252 cc = tvb_get_ntohl(tvb, offset + 2);
253 proto_tree_add_text(opt_tree, tvb, offset, optlen,
254 "%s: %u", optp->name, cc);
255 tcp_info_append_uint(fd, "CC", cc);
258 static const ip_tcp_opt tcpopts[] = {
277 "Maximum segment size",
281 dissect_tcpopt_maxseg
289 dissect_tcpopt_wscale
302 &ett_tcp_option_sack,
329 dissect_tcpopt_timestamp
357 #define N_TCP_OPTS (sizeof tcpopts / sizeof tcpopts[0])
360 static const true_false_string flags_set_truth = {
366 /* Determine if there is a sub-dissector and call it. This has been */
367 /* separated into a stand alone routine to other protocol dissectors */
368 /* can call to it, ie. socks */
371 decode_tcp_ports(tvbuff_t *tvb, int offset, packet_info *pinfo,
372 proto_tree *tree, int src_port, int dst_port)
376 const u_char *next_pd;
380 next_tvb = tvb_new_subset(tvb, offset, -1, -1);
382 /* determine if this packet is part of a conversation and call dissector */
383 /* for the conversation if available */
385 if (try_conversation_dissector(&pinfo->src, &pinfo->dst, PT_TCP,
386 src_port, dst_port, next_tvb, pinfo, tree))
389 /* try to apply the plugins */
392 plugin *pt_plug = plugin_list;
394 if (enabled_plugins_number > 0) {
395 tvb_compat(next_tvb, &next_pd, &next_offset);
397 if (pt_plug->enabled && strstr(pt_plug->protocol, "tcp") &&
398 tree && dfilter_apply(pt_plug->filter, tree, next_pd, pinfo->fd->cap_len)) {
399 pt_plug->dissector(next_pd, next_offset, pinfo->fd, tree);
402 pt_plug = pt_plug->next;
408 /* do lookup with the subdissector table */
409 if (dissector_try_port(subdissector_table, src_port, next_tvb, pinfo, tree) ||
410 dissector_try_port(subdissector_table, dst_port, next_tvb, pinfo, tree))
413 /* do lookup with the heuristic subdissector table */
414 if (dissector_try_heuristic(heur_subdissector_list, next_tvb, pinfo, tree))
417 /* Oh, well, we don't know this; dissect it as data. */
418 dissect_data(next_tvb, 0, pinfo, tree);
423 dissect_tcp(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
426 proto_tree *tcp_tree = NULL, *field_tree = NULL;
429 gchar flags[64] = "<None>";
430 gchar *fstr[] = {"FIN", "SYN", "RST", "PSH", "ACK", "URG", "ECN", "CWR" };
437 guint length_remaining;
439 CHECK_DISPLAY_AS_DATA(proto_tcp, tvb, pinfo, tree);
441 pinfo->current_proto = "TCP";
443 if (check_col(pinfo->fd, COL_PROTOCOL))
444 col_set_str(pinfo->fd, COL_PROTOCOL, "TCP");
446 /* Clear out the Info column. */
447 if (check_col(pinfo->fd, COL_INFO))
448 col_clear(pinfo->fd, COL_INFO);
450 /* Avoids alignment problems on many architectures. */
451 tvb_memcpy(tvb, (guint8 *)&th, offset, sizeof(e_tcphdr));
452 th.th_sport = ntohs(th.th_sport);
453 th.th_dport = ntohs(th.th_dport);
454 th.th_win = ntohs(th.th_win);
455 th.th_sum = ntohs(th.th_sum);
456 th.th_urp = ntohs(th.th_urp);
457 th.th_seq = ntohl(th.th_seq);
458 th.th_ack = ntohl(th.th_ack);
460 /* Export the urgent pointer, for the benefit of protocols such as
462 tcp_urgent_pointer = th.th_urp;
464 if (check_col(pinfo->fd, COL_INFO) || tree) {
465 for (i = 0; i < 8; i++) {
467 if (th.th_flags & bpos) {
469 strcpy(&flags[fpos], ", ");
472 strcpy(&flags[fpos], fstr[i]);
479 hlen = hi_nibble(th.th_off_x2) * 4; /* TCP header length, in bytes */
481 /* Compute the length of data in this segment. */
482 seglen = tvb_reported_length(tvb) - hlen;
484 /* Compute the sequence number of next octet after this segment. */
485 nxtseq = th.th_seq + seglen;
487 if (check_col(pinfo->fd, COL_INFO)) {
488 if (th.th_flags & TH_URG)
489 col_append_fstr(pinfo->fd, COL_INFO, "%s > %s [%s] Seq=%u Ack=%u Win=%u Urg=%u Len=%d",
490 get_tcp_port(th.th_sport), get_tcp_port(th.th_dport), flags,
491 th.th_seq, th.th_ack, th.th_win, th.th_urp, seglen);
493 col_append_fstr(pinfo->fd, COL_INFO, "%s > %s [%s] Seq=%u Ack=%u Win=%u Len=%d",
494 get_tcp_port(th.th_sport), get_tcp_port(th.th_dport), flags,
495 th.th_seq, th.th_ack, th.th_win, seglen);
499 if (g_tcp_summary_in_tree) {
500 ti = proto_tree_add_protocol_format(tree, proto_tcp, tvb, 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);
503 ti = proto_tree_add_item(tree, proto_tcp, tvb, offset, hlen, FALSE);
505 tcp_tree = proto_item_add_subtree(ti, ett_tcp);
506 proto_tree_add_uint_format(tcp_tree, hf_tcp_srcport, tvb, offset, 2, th.th_sport,
507 "Source port: %s (%u)", get_tcp_port(th.th_sport), th.th_sport);
508 proto_tree_add_uint_format(tcp_tree, hf_tcp_dstport, tvb, offset + 2, 2, th.th_dport,
509 "Destination port: %s (%u)", get_tcp_port(th.th_dport), th.th_dport);
510 proto_tree_add_uint_hidden(tcp_tree, hf_tcp_port, tvb, offset, 2, th.th_sport);
511 proto_tree_add_uint_hidden(tcp_tree, hf_tcp_port, tvb, offset + 2, 2, th.th_dport);
512 proto_tree_add_uint(tcp_tree, hf_tcp_seq, tvb, offset + 4, 4, th.th_seq);
513 if (nxtseq != th.th_seq)
514 proto_tree_add_uint(tcp_tree, hf_tcp_nxtseq, tvb, offset, 0, nxtseq);
515 if (th.th_flags & TH_ACK)
516 proto_tree_add_uint(tcp_tree, hf_tcp_ack, tvb, offset + 8, 4, th.th_ack);
517 proto_tree_add_uint_format(tcp_tree, hf_tcp_hdr_len, tvb, offset + 12, 1, hlen,
518 "Header length: %u bytes", hlen);
519 tf = proto_tree_add_uint_format(tcp_tree, hf_tcp_flags, tvb, offset + 13, 1,
520 th.th_flags, "Flags: 0x%04x (%s)", th.th_flags, flags);
521 field_tree = proto_item_add_subtree(tf, ett_tcp_flags);
522 proto_tree_add_boolean(field_tree, hf_tcp_flags_cwr, tvb, offset + 13, 1, th.th_flags);
523 proto_tree_add_boolean(field_tree, hf_tcp_flags_ecn, tvb, offset + 13, 1, th.th_flags);
524 proto_tree_add_boolean(field_tree, hf_tcp_flags_urg, tvb, offset + 13, 1, th.th_flags);
525 proto_tree_add_boolean(field_tree, hf_tcp_flags_ack, tvb, offset + 13, 1, th.th_flags);
526 proto_tree_add_boolean(field_tree, hf_tcp_flags_push, tvb, offset + 13, 1, th.th_flags);
527 proto_tree_add_boolean(field_tree, hf_tcp_flags_reset, tvb, offset + 13, 1, th.th_flags);
528 proto_tree_add_boolean(field_tree, hf_tcp_flags_syn, tvb, offset + 13, 1, th.th_flags);
529 proto_tree_add_boolean(field_tree, hf_tcp_flags_fin, tvb, offset + 13, 1, th.th_flags);
530 proto_tree_add_uint(tcp_tree, hf_tcp_window_size, tvb, offset + 14, 2, th.th_win);
531 proto_tree_add_uint(tcp_tree, hf_tcp_checksum, tvb, offset + 16, 2, th.th_sum);
532 if (th.th_flags & TH_URG)
533 proto_tree_add_uint(tcp_tree, hf_tcp_urgent_pointer, tvb, offset + 18, 2, th.th_urp);
536 /* Decode TCP options, if any. */
537 if (tree && hlen > sizeof (e_tcphdr)) {
538 /* There's more than just the fixed-length header. Decode the
540 optlen = hlen - sizeof (e_tcphdr); /* length of options, in bytes */
541 tf = proto_tree_add_text(tcp_tree, tvb, offset + 20, optlen,
542 "Options: (%d bytes)", optlen);
543 field_tree = proto_item_add_subtree(tf, ett_tcp_options);
544 dissect_ip_tcp_options(tvb, offset + 20, optlen,
545 tcpopts, N_TCP_OPTS, TCPOPT_EOL, pinfo->fd, field_tree);
548 /* Skip over header + options */
551 pinfo->ptype = PT_TCP;
552 pinfo->srcport = th.th_sport;
553 pinfo->destport = th.th_dport;
555 /* Check the packet length to see if there's more data
556 (it could be an ACK-only packet) */
557 length_remaining = tvb_length_remaining(tvb, offset);
558 if (length_remaining != 0) {
559 if (th.th_flags & TH_RST) {
563 * 4.2.2.12 RST Segment: RFC-793 Section 3.4
565 * A TCP SHOULD allow a received RST segment to include data.
568 * It has been suggested that a RST segment could contain
569 * ASCII text that encoded and explained the cause of the
570 * RST. No standard has yet been established for such
573 * so for segments with RST we just display the data as text.
575 proto_tree_add_text(tcp_tree, tvb, offset, length_remaining,
577 tvb_format_text(tvb, offset, length_remaining));
579 decode_tcp_ports( tvb, offset, pinfo, tree, th.th_sport, th.th_dport);
582 if( data_out_file ) {
583 reassemble_tcp( th.th_seq, /* sequence number */
584 seglen, /* data length */
585 tvb_get_ptr(tvb, offset, length_remaining), /* data */
586 length_remaining, /* captured data length */
587 ( th.th_flags & TH_SYN ), /* is syn set? */
596 proto_register_tcp(void)
598 static hf_register_info hf[] = {
601 { "Source Port", "tcp.srcport", FT_UINT16, BASE_DEC, NULL, 0x0,
605 { "Destination Port", "tcp.dstport", FT_UINT16, BASE_DEC, NULL, 0x0,
609 { "Source or Destination Port", "tcp.port", FT_UINT16, BASE_DEC, NULL, 0x0,
613 { "Sequence number", "tcp.seq", FT_UINT32, BASE_DEC, NULL, 0x0,
617 { "Next sequence number", "tcp.nxtseq", FT_UINT32, BASE_DEC, NULL, 0x0,
621 { "Acknowledgement number", "tcp.ack", FT_UINT32, BASE_DEC, NULL, 0x0,
625 { "Header Length", "tcp.hdr_len", FT_UINT8, BASE_DEC, NULL, 0x0,
629 { "Flags", "tcp.flags", FT_UINT8, BASE_HEX, NULL, 0x0,
633 { "Congestion Window Reduced (CWR)", "tcp.flags.cwr", FT_BOOLEAN, 8, TFS(&flags_set_truth), TH_CWR,
637 { "ECN-Echo", "tcp.flags.ecn", FT_BOOLEAN, 8, TFS(&flags_set_truth), TH_ECN,
641 { "Urgent", "tcp.flags.urg", FT_BOOLEAN, 8, TFS(&flags_set_truth), TH_URG,
645 { "Acknowledgment", "tcp.flags.ack", FT_BOOLEAN, 8, TFS(&flags_set_truth), TH_ACK,
648 { &hf_tcp_flags_push,
649 { "Push", "tcp.flags.push", FT_BOOLEAN, 8, TFS(&flags_set_truth), TH_PUSH,
652 { &hf_tcp_flags_reset,
653 { "Reset", "tcp.flags.reset", FT_BOOLEAN, 8, TFS(&flags_set_truth), TH_RST,
657 { "Syn", "tcp.flags.syn", FT_BOOLEAN, 8, TFS(&flags_set_truth), TH_SYN,
661 { "Fin", "tcp.flags.fin", FT_BOOLEAN, 8, TFS(&flags_set_truth), TH_FIN,
664 { &hf_tcp_window_size,
665 { "Window size", "tcp.window_size", FT_UINT16, BASE_DEC, NULL, 0x0,
669 { "Checksum", "tcp.checksum", FT_UINT16, BASE_HEX, NULL, 0x0,
672 { &hf_tcp_urgent_pointer,
673 { "Urgent pointer", "tcp.urgent_pointer", FT_UINT16, BASE_DEC, NULL, 0x0,
676 static gint *ett[] = {
680 &ett_tcp_option_sack,
682 module_t *tcp_module;
684 proto_tcp = proto_register_protocol ("Transmission Control Protocol", "tcp");
685 proto_register_field_array(proto_tcp, hf, array_length(hf));
686 proto_register_subtree_array(ett, array_length(ett));
688 /* subdissector code */
689 subdissector_table = register_dissector_table("tcp.port");
690 register_heur_dissector_list("tcp", &heur_subdissector_list);
692 /* Register a configuration preferences */
693 tcp_module = prefs_register_module("tcp", "TCP", NULL);
694 prefs_register_bool_preference(tcp_module, "tcp_summary_in_tree",
695 "Show TCP summary in protocol tree",
696 "Whether the TCP summary line should be shown in the protocol tree",
697 &g_tcp_summary_in_tree);
701 proto_reg_handoff_tcp(void)
703 dissector_add("ip.proto", IP_PROTO_TCP, dissect_tcp);