2 * Routines for TCP packet disassembly
4 * $Id: packet-tcp.c,v 1.95 2001/01/03 07:53:43 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>
43 #ifdef NEED_SNPRINTF_H
44 # include "snprintf.h"
52 #include "packet-tcp.h"
53 #include "packet-ip.h"
54 #include "conversation.h"
57 /* Place TCP summary in proto tree */
58 static gboolean tcp_summary_in_tree = TRUE;
60 extern FILE* data_out_file;
62 guint16 tcp_urgent_pointer;
64 static int proto_tcp = -1;
65 static int hf_tcp_srcport = -1;
66 static int hf_tcp_dstport = -1;
67 static int hf_tcp_port = -1;
68 static int hf_tcp_seq = -1;
69 static int hf_tcp_nxtseq = -1;
70 static int hf_tcp_ack = -1;
71 static int hf_tcp_hdr_len = -1;
72 static int hf_tcp_flags = -1;
73 static int hf_tcp_flags_cwr = -1;
74 static int hf_tcp_flags_ecn = -1;
75 static int hf_tcp_flags_urg = -1;
76 static int hf_tcp_flags_ack = -1;
77 static int hf_tcp_flags_push = -1;
78 static int hf_tcp_flags_reset = -1;
79 static int hf_tcp_flags_syn = -1;
80 static int hf_tcp_flags_fin = -1;
81 static int hf_tcp_window_size = -1;
82 static int hf_tcp_checksum = -1;
83 static int hf_tcp_urgent_pointer = -1;
85 static gint ett_tcp = -1;
86 static gint ett_tcp_flags = -1;
87 static gint ett_tcp_options = -1;
88 static gint ett_tcp_option_sack = -1;
90 static dissector_table_t subdissector_table;
91 static heur_dissector_list_t heur_subdissector_list;
95 #define TCP_PORT_SMTP 25
97 /* TCP structs and definitions */
99 typedef struct _e_tcphdr {
104 guint8 th_off_x2; /* combines th_off and th_x2 */
123 #define TCPOPT_NOP 1 /* Padding */
124 #define TCPOPT_EOL 0 /* End of options */
125 #define TCPOPT_MSS 2 /* Segment size negotiating */
126 #define TCPOPT_WINDOW 3 /* Window scaling */
127 #define TCPOPT_SACK_PERM 4 /* SACK Permitted */
128 #define TCPOPT_SACK 5 /* SACK Block */
129 #define TCPOPT_ECHO 6
130 #define TCPOPT_ECHOREPLY 7
131 #define TCPOPT_TIMESTAMP 8 /* Better RTT estimations/PAWS */
133 #define TCPOPT_CCNEW 12
134 #define TCPOPT_CCECHO 13
135 #define TCPOPT_MD5 19 /* RFC2385 */
141 #define TCPOLEN_MSS 4
142 #define TCPOLEN_WINDOW 3
143 #define TCPOLEN_SACK_PERM 2
144 #define TCPOLEN_SACK_MIN 2
145 #define TCPOLEN_ECHO 6
146 #define TCPOLEN_ECHOREPLY 6
147 #define TCPOLEN_TIMESTAMP 10
149 #define TCPOLEN_CCNEW 6
150 #define TCPOLEN_CCECHO 6
151 #define TCPOLEN_MD5 18
154 tcp_info_append_uint(frame_data *fd, const char *abbrev, guint32 val)
156 if (check_col(fd, COL_INFO))
157 col_append_fstr(fd, COL_INFO, " %s=%u", abbrev, val);
161 dissect_tcpopt_maxseg(const ip_tcp_opt *optp, tvbuff_t *tvb,
162 int offset, guint optlen, frame_data *fd, proto_tree *opt_tree)
166 mss = tvb_get_ntohs(tvb, offset + 2);
167 proto_tree_add_text(opt_tree, tvb, offset, optlen,
168 "%s: %u bytes", optp->name, mss);
169 tcp_info_append_uint(fd, "MSS", mss);
173 dissect_tcpopt_wscale(const ip_tcp_opt *optp, tvbuff_t *tvb,
174 int offset, guint optlen, frame_data *fd, proto_tree *opt_tree)
178 ws = tvb_get_guint8(tvb, offset + 2);
179 proto_tree_add_text(opt_tree, tvb, offset, optlen,
180 "%s: %u bytes", optp->name, ws);
181 tcp_info_append_uint(fd, "WS", ws);
185 dissect_tcpopt_sack(const ip_tcp_opt *optp, tvbuff_t *tvb,
186 int offset, guint optlen, frame_data *fd, proto_tree *opt_tree)
188 proto_tree *field_tree = NULL;
190 guint leftedge, rightedge;
192 tf = proto_tree_add_text(opt_tree, tvb, offset, optlen, "%s:", optp->name);
193 offset += 2; /* skip past type and length */
194 optlen -= 2; /* subtract size of type and length */
196 if (field_tree == NULL) {
197 /* Haven't yet made a subtree out of this option. Do so. */
198 field_tree = proto_item_add_subtree(tf, *optp->subtree_index);
201 proto_tree_add_text(field_tree, tvb, offset, optlen,
202 "(suboption would go past end of option)");
205 leftedge = tvb_get_ntohl(tvb, offset);
208 proto_tree_add_text(field_tree, tvb, offset, optlen,
209 "(suboption would go past end of option)");
212 /* XXX - check whether it goes past end of packet */
213 rightedge = tvb_get_ntohl(tvb, offset + 4);
215 proto_tree_add_text(field_tree, tvb, offset, 8,
216 "left edge = %u, right edge = %u", leftedge, rightedge);
217 tcp_info_append_uint(fd, "SLE", leftedge);
218 tcp_info_append_uint(fd, "SRE", rightedge);
224 dissect_tcpopt_echo(const ip_tcp_opt *optp, tvbuff_t *tvb,
225 int offset, guint optlen, frame_data *fd, proto_tree *opt_tree)
229 echo = tvb_get_ntohl(tvb, offset + 2);
230 proto_tree_add_text(opt_tree, tvb, offset, optlen,
231 "%s: %u", optp->name, echo);
232 tcp_info_append_uint(fd, "ECHO", echo);
236 dissect_tcpopt_timestamp(const ip_tcp_opt *optp, tvbuff_t *tvb,
237 int offset, guint optlen, frame_data *fd, proto_tree *opt_tree)
241 tsv = tvb_get_ntohl(tvb, offset + 2);
242 tser = tvb_get_ntohl(tvb, offset + 6);
243 proto_tree_add_text(opt_tree, tvb, offset, optlen,
244 "%s: tsval %u, tsecr %u", optp->name, tsv, tser);
245 tcp_info_append_uint(fd, "TSV", tsv);
246 tcp_info_append_uint(fd, "TSER", tser);
250 dissect_tcpopt_cc(const ip_tcp_opt *optp, tvbuff_t *tvb,
251 int offset, guint optlen, frame_data *fd, proto_tree *opt_tree)
255 cc = tvb_get_ntohl(tvb, offset + 2);
256 proto_tree_add_text(opt_tree, tvb, offset, optlen,
257 "%s: %u", optp->name, cc);
258 tcp_info_append_uint(fd, "CC", cc);
261 static const ip_tcp_opt tcpopts[] = {
280 "Maximum segment size",
284 dissect_tcpopt_maxseg
292 dissect_tcpopt_wscale
305 &ett_tcp_option_sack,
332 dissect_tcpopt_timestamp
368 #define N_TCP_OPTS (sizeof tcpopts / sizeof tcpopts[0])
371 static const true_false_string flags_set_truth = {
377 /* Determine if there is a sub-dissector and call it. This has been */
378 /* separated into a stand alone routine to other protocol dissectors */
379 /* can call to it, ie. socks */
382 decode_tcp_ports(tvbuff_t *tvb, int offset, packet_info *pinfo,
383 proto_tree *tree, int src_port, int dst_port)
387 const u_char *next_pd;
391 next_tvb = tvb_new_subset(tvb, offset, -1, -1);
393 /* determine if this packet is part of a conversation and call dissector */
394 /* for the conversation if available */
396 if (try_conversation_dissector(&pinfo->src, &pinfo->dst, PT_TCP,
397 src_port, dst_port, next_tvb, pinfo, tree))
400 /* try to apply the plugins */
403 plugin *pt_plug = plugin_list;
405 if (enabled_plugins_number > 0) {
406 tvb_compat(next_tvb, &next_pd, &next_offset);
408 if (pt_plug->enabled && strstr(pt_plug->protocol, "tcp") &&
409 tree && dfilter_apply(pt_plug->filter, tree, next_pd, pinfo->fd->cap_len)) {
410 pt_plug->dissector(next_pd, next_offset, pinfo->fd, tree);
413 pt_plug = pt_plug->next;
419 /* do lookup with the subdissector table */
420 if (dissector_try_port(subdissector_table, src_port, next_tvb, pinfo, tree) ||
421 dissector_try_port(subdissector_table, dst_port, next_tvb, pinfo, tree))
424 /* do lookup with the heuristic subdissector table */
425 if (dissector_try_heuristic(heur_subdissector_list, next_tvb, pinfo, tree))
428 /* Oh, well, we don't know this; dissect it as data. */
429 dissect_data(next_tvb, 0, pinfo, tree);
434 dissect_tcp(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
437 proto_tree *tcp_tree = NULL, *field_tree = NULL;
440 gchar flags[64] = "<None>";
441 gchar *fstr[] = {"FIN", "SYN", "RST", "PSH", "ACK", "URG", "ECN", "CWR" };
452 guint16 computed_cksum;
453 guint length_remaining;
455 CHECK_DISPLAY_AS_DATA(proto_tcp, tvb, pinfo, tree);
457 pinfo->current_proto = "TCP";
459 if (check_col(pinfo->fd, COL_PROTOCOL))
460 col_set_str(pinfo->fd, COL_PROTOCOL, "TCP");
462 /* Clear out the Info column. */
463 if (check_col(pinfo->fd, COL_INFO))
464 col_clear(pinfo->fd, COL_INFO);
466 /* Avoids alignment problems on many architectures. */
467 tvb_memcpy(tvb, (guint8 *)&th, offset, sizeof(e_tcphdr));
468 th.th_sport = ntohs(th.th_sport);
469 th.th_dport = ntohs(th.th_dport);
470 th.th_win = ntohs(th.th_win);
471 th.th_sum = ntohs(th.th_sum);
472 th.th_urp = ntohs(th.th_urp);
473 th.th_seq = ntohl(th.th_seq);
474 th.th_ack = ntohl(th.th_ack);
476 /* Export the urgent pointer, for the benefit of protocols such as
478 tcp_urgent_pointer = th.th_urp;
480 if (check_col(pinfo->fd, COL_INFO) || tree) {
481 for (i = 0; i < 8; i++) {
483 if (th.th_flags & bpos) {
485 strcpy(&flags[fpos], ", ");
488 strcpy(&flags[fpos], fstr[i]);
495 hlen = hi_nibble(th.th_off_x2) * 4; /* TCP header length, in bytes */
497 reported_len = tvb_reported_length(tvb);
498 len = tvb_length(tvb);
500 /* Compute the length of data in this segment. */
501 seglen = reported_len - hlen;
503 /* Compute the sequence number of next octet after this segment. */
504 nxtseq = th.th_seq + seglen;
506 if (check_col(pinfo->fd, COL_INFO)) {
507 if (th.th_flags & TH_URG)
508 col_append_fstr(pinfo->fd, COL_INFO, "%s > %s [%s] Seq=%u Ack=%u Win=%u Urg=%u Len=%d",
509 get_tcp_port(th.th_sport), get_tcp_port(th.th_dport), flags,
510 th.th_seq, th.th_ack, th.th_win, th.th_urp, seglen);
512 col_append_fstr(pinfo->fd, COL_INFO, "%s > %s [%s] Seq=%u Ack=%u Win=%u Len=%d",
513 get_tcp_port(th.th_sport), get_tcp_port(th.th_dport), flags,
514 th.th_seq, th.th_ack, th.th_win, seglen);
518 if (tcp_summary_in_tree) {
519 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);
522 ti = proto_tree_add_item(tree, proto_tcp, tvb, offset, hlen, FALSE);
524 tcp_tree = proto_item_add_subtree(ti, ett_tcp);
525 proto_tree_add_uint_format(tcp_tree, hf_tcp_srcport, tvb, offset, 2, th.th_sport,
526 "Source port: %s (%u)", get_tcp_port(th.th_sport), th.th_sport);
527 proto_tree_add_uint_format(tcp_tree, hf_tcp_dstport, tvb, offset + 2, 2, th.th_dport,
528 "Destination port: %s (%u)", get_tcp_port(th.th_dport), th.th_dport);
529 proto_tree_add_uint_hidden(tcp_tree, hf_tcp_port, tvb, offset, 2, th.th_sport);
530 proto_tree_add_uint_hidden(tcp_tree, hf_tcp_port, tvb, offset + 2, 2, th.th_dport);
531 proto_tree_add_uint(tcp_tree, hf_tcp_seq, tvb, offset + 4, 4, th.th_seq);
532 if (nxtseq != th.th_seq)
533 proto_tree_add_uint(tcp_tree, hf_tcp_nxtseq, tvb, offset, 0, nxtseq);
534 if (th.th_flags & TH_ACK)
535 proto_tree_add_uint(tcp_tree, hf_tcp_ack, tvb, offset + 8, 4, th.th_ack);
536 proto_tree_add_uint_format(tcp_tree, hf_tcp_hdr_len, tvb, offset + 12, 1, hlen,
537 "Header length: %u bytes", hlen);
538 tf = proto_tree_add_uint_format(tcp_tree, hf_tcp_flags, tvb, offset + 13, 1,
539 th.th_flags, "Flags: 0x%04x (%s)", th.th_flags, flags);
540 field_tree = proto_item_add_subtree(tf, ett_tcp_flags);
541 proto_tree_add_boolean(field_tree, hf_tcp_flags_cwr, tvb, offset + 13, 1, th.th_flags);
542 proto_tree_add_boolean(field_tree, hf_tcp_flags_ecn, tvb, offset + 13, 1, th.th_flags);
543 proto_tree_add_boolean(field_tree, hf_tcp_flags_urg, tvb, offset + 13, 1, th.th_flags);
544 proto_tree_add_boolean(field_tree, hf_tcp_flags_ack, tvb, offset + 13, 1, th.th_flags);
545 proto_tree_add_boolean(field_tree, hf_tcp_flags_push, tvb, offset + 13, 1, th.th_flags);
546 proto_tree_add_boolean(field_tree, hf_tcp_flags_reset, tvb, offset + 13, 1, th.th_flags);
547 proto_tree_add_boolean(field_tree, hf_tcp_flags_syn, tvb, offset + 13, 1, th.th_flags);
548 proto_tree_add_boolean(field_tree, hf_tcp_flags_fin, tvb, offset + 13, 1, th.th_flags);
549 proto_tree_add_uint(tcp_tree, hf_tcp_window_size, tvb, offset + 14, 2, th.th_win);
550 if (!pinfo->fragmented && len >= reported_len) {
551 /* The packet isn't part of a fragmented datagram and isn't
552 truncated, so we can checksum it.
553 XXX - make a bigger scatter-gather list once we do fragment
556 /* Set up the fields of the pseudo-header. */
557 cksum_vec[0].ptr = pinfo->src.data;
558 cksum_vec[0].len = pinfo->src.len;
559 cksum_vec[1].ptr = pinfo->dst.data;
560 cksum_vec[1].len = pinfo->dst.len;
561 cksum_vec[2].ptr = (const guint8 *)&phdr;
562 switch (pinfo->src.type) {
565 phdr[0] = htonl((IP_PROTO_TCP<<16) + reported_len);
566 cksum_vec[2].len = 4;
570 phdr[0] = htonl(reported_len);
571 phdr[1] = htonl(IP_PROTO_TCP);
572 cksum_vec[2].len = 8;
576 /* TCP runs only atop IPv4 and IPv6.... */
577 g_assert_not_reached();
580 cksum_vec[3].ptr = tvb_get_ptr(tvb, offset, len);
581 cksum_vec[3].len = reported_len;
582 computed_cksum = in_cksum(&cksum_vec[0], 4);
583 if (computed_cksum == 0) {
584 proto_tree_add_uint_format(tcp_tree, hf_tcp_checksum, tvb,
585 offset + 16, 2, th.th_sum, "Checksum: 0x%04x (correct)", th.th_sum);
587 proto_tree_add_uint_format(tcp_tree, hf_tcp_checksum, tvb,
588 offset + 16, 2, th.th_sum,
589 "Checksum: 0x%04x (incorrect, should be 0x%04x)", th.th_sum,
590 in_cksum_shouldbe(th.th_sum, computed_cksum));
593 proto_tree_add_uint_format(tcp_tree, hf_tcp_checksum, tvb,
594 offset + 16, 2, th.th_sum, "Checksum: 0x%04x", th.th_sum);
596 if (th.th_flags & TH_URG)
597 proto_tree_add_uint(tcp_tree, hf_tcp_urgent_pointer, tvb, offset + 18, 2, th.th_urp);
600 /* Decode TCP options, if any. */
601 if (tree && hlen > sizeof (e_tcphdr)) {
602 /* There's more than just the fixed-length header. Decode the
604 optlen = hlen - sizeof (e_tcphdr); /* length of options, in bytes */
605 tf = proto_tree_add_text(tcp_tree, tvb, offset + 20, optlen,
606 "Options: (%d bytes)", optlen);
607 field_tree = proto_item_add_subtree(tf, ett_tcp_options);
608 dissect_ip_tcp_options(tvb, offset + 20, optlen,
609 tcpopts, N_TCP_OPTS, TCPOPT_EOL, pinfo->fd, field_tree);
612 /* Skip over header + options */
615 pinfo->ptype = PT_TCP;
616 pinfo->srcport = th.th_sport;
617 pinfo->destport = th.th_dport;
619 /* Check the packet length to see if there's more data
620 (it could be an ACK-only packet) */
621 length_remaining = tvb_length_remaining(tvb, offset);
622 if (length_remaining != 0) {
623 if (th.th_flags & TH_RST) {
627 * 4.2.2.12 RST Segment: RFC-793 Section 3.4
629 * A TCP SHOULD allow a received RST segment to include data.
632 * It has been suggested that a RST segment could contain
633 * ASCII text that encoded and explained the cause of the
634 * RST. No standard has yet been established for such
637 * so for segments with RST we just display the data as text.
639 proto_tree_add_text(tcp_tree, tvb, offset, length_remaining,
641 tvb_format_text(tvb, offset, length_remaining));
643 decode_tcp_ports( tvb, offset, pinfo, tree, th.th_sport, th.th_dport);
646 if( data_out_file ) {
647 reassemble_tcp( th.th_seq, /* sequence number */
648 seglen, /* data length */
649 tvb_get_ptr(tvb, offset, length_remaining), /* data */
650 length_remaining, /* captured data length */
651 ( th.th_flags & TH_SYN ), /* is syn set? */
660 proto_register_tcp(void)
662 static hf_register_info hf[] = {
665 { "Source Port", "tcp.srcport", FT_UINT16, BASE_DEC, NULL, 0x0,
669 { "Destination Port", "tcp.dstport", FT_UINT16, BASE_DEC, NULL, 0x0,
673 { "Source or Destination Port", "tcp.port", FT_UINT16, BASE_DEC, NULL, 0x0,
677 { "Sequence number", "tcp.seq", FT_UINT32, BASE_DEC, NULL, 0x0,
681 { "Next sequence number", "tcp.nxtseq", FT_UINT32, BASE_DEC, NULL, 0x0,
685 { "Acknowledgement number", "tcp.ack", FT_UINT32, BASE_DEC, NULL, 0x0,
689 { "Header Length", "tcp.hdr_len", FT_UINT8, BASE_DEC, NULL, 0x0,
693 { "Flags", "tcp.flags", FT_UINT8, BASE_HEX, NULL, 0x0,
697 { "Congestion Window Reduced (CWR)", "tcp.flags.cwr", FT_BOOLEAN, 8, TFS(&flags_set_truth), TH_CWR,
701 { "ECN-Echo", "tcp.flags.ecn", FT_BOOLEAN, 8, TFS(&flags_set_truth), TH_ECN,
705 { "Urgent", "tcp.flags.urg", FT_BOOLEAN, 8, TFS(&flags_set_truth), TH_URG,
709 { "Acknowledgment", "tcp.flags.ack", FT_BOOLEAN, 8, TFS(&flags_set_truth), TH_ACK,
712 { &hf_tcp_flags_push,
713 { "Push", "tcp.flags.push", FT_BOOLEAN, 8, TFS(&flags_set_truth), TH_PUSH,
716 { &hf_tcp_flags_reset,
717 { "Reset", "tcp.flags.reset", FT_BOOLEAN, 8, TFS(&flags_set_truth), TH_RST,
721 { "Syn", "tcp.flags.syn", FT_BOOLEAN, 8, TFS(&flags_set_truth), TH_SYN,
725 { "Fin", "tcp.flags.fin", FT_BOOLEAN, 8, TFS(&flags_set_truth), TH_FIN,
728 { &hf_tcp_window_size,
729 { "Window size", "tcp.window_size", FT_UINT16, BASE_DEC, NULL, 0x0,
733 { "Checksum", "tcp.checksum", FT_UINT16, BASE_HEX, NULL, 0x0,
736 { &hf_tcp_urgent_pointer,
737 { "Urgent pointer", "tcp.urgent_pointer", FT_UINT16, BASE_DEC, NULL, 0x0,
740 static gint *ett[] = {
744 &ett_tcp_option_sack,
746 module_t *tcp_module;
748 proto_tcp = proto_register_protocol("Transmission Control Protocol",
750 proto_register_field_array(proto_tcp, hf, array_length(hf));
751 proto_register_subtree_array(ett, array_length(ett));
753 /* subdissector code */
754 subdissector_table = register_dissector_table("tcp.port");
755 register_heur_dissector_list("tcp", &heur_subdissector_list);
757 /* Register configuration preferences */
758 tcp_module = prefs_register_protocol(proto_tcp, NULL);
759 prefs_register_bool_preference(tcp_module, "tcp_summary_in_tree",
760 "Show TCP summary in protocol tree",
761 "Whether the TCP summary line should be shown in the protocol tree",
762 &tcp_summary_in_tree);
766 proto_reg_handoff_tcp(void)
768 dissector_add("ip.proto", IP_PROTO_TCP, dissect_tcp);