2 * Routines for TCP packet disassembly
4 * $Id: packet-tcp.c,v 1.100 2001/02/28 19:33:49 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"
51 #include "packet-tcp.h"
52 #include "packet-ip.h"
53 #include "conversation.h"
56 /* Place TCP summary in proto tree */
57 static gboolean 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_checksum_bad = -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;
92 static conv_dissector_list_t conv_subdissector_list;
96 #define TCP_PORT_SMTP 25
98 /* TCP structs and definitions */
100 typedef struct _e_tcphdr {
105 guint8 th_off_x2; /* combines th_off and th_x2 */
124 #define TCPOPT_NOP 1 /* Padding */
125 #define TCPOPT_EOL 0 /* End of options */
126 #define TCPOPT_MSS 2 /* Segment size negotiating */
127 #define TCPOPT_WINDOW 3 /* Window scaling */
128 #define TCPOPT_SACK_PERM 4 /* SACK Permitted */
129 #define TCPOPT_SACK 5 /* SACK Block */
130 #define TCPOPT_ECHO 6
131 #define TCPOPT_ECHOREPLY 7
132 #define TCPOPT_TIMESTAMP 8 /* Better RTT estimations/PAWS */
134 #define TCPOPT_CCNEW 12
135 #define TCPOPT_CCECHO 13
136 #define TCPOPT_MD5 19 /* RFC2385 */
142 #define TCPOLEN_MSS 4
143 #define TCPOLEN_WINDOW 3
144 #define TCPOLEN_SACK_PERM 2
145 #define TCPOLEN_SACK_MIN 2
146 #define TCPOLEN_ECHO 6
147 #define TCPOLEN_ECHOREPLY 6
148 #define TCPOLEN_TIMESTAMP 10
150 #define TCPOLEN_CCNEW 6
151 #define TCPOLEN_CCECHO 6
152 #define TCPOLEN_MD5 18
155 tcp_info_append_uint(frame_data *fd, const char *abbrev, guint32 val)
157 if (check_col(fd, COL_INFO))
158 col_append_fstr(fd, COL_INFO, " %s=%u", abbrev, val);
162 dissect_tcpopt_maxseg(const ip_tcp_opt *optp, tvbuff_t *tvb,
163 int offset, guint optlen, frame_data *fd, proto_tree *opt_tree)
167 mss = tvb_get_ntohs(tvb, offset + 2);
168 proto_tree_add_text(opt_tree, tvb, offset, optlen,
169 "%s: %u bytes", optp->name, mss);
170 tcp_info_append_uint(fd, "MSS", mss);
174 dissect_tcpopt_wscale(const ip_tcp_opt *optp, tvbuff_t *tvb,
175 int offset, guint optlen, frame_data *fd, proto_tree *opt_tree)
179 ws = tvb_get_guint8(tvb, offset + 2);
180 proto_tree_add_text(opt_tree, tvb, offset, optlen,
181 "%s: %u bytes", optp->name, ws);
182 tcp_info_append_uint(fd, "WS", ws);
186 dissect_tcpopt_sack(const ip_tcp_opt *optp, tvbuff_t *tvb,
187 int offset, guint optlen, frame_data *fd, proto_tree *opt_tree)
189 proto_tree *field_tree = NULL;
191 guint leftedge, rightedge;
193 tf = proto_tree_add_text(opt_tree, tvb, offset, optlen, "%s:", optp->name);
194 offset += 2; /* skip past type and length */
195 optlen -= 2; /* subtract size of type and length */
197 if (field_tree == NULL) {
198 /* Haven't yet made a subtree out of this option. Do so. */
199 field_tree = proto_item_add_subtree(tf, *optp->subtree_index);
202 proto_tree_add_text(field_tree, tvb, offset, optlen,
203 "(suboption would go past end of option)");
206 leftedge = tvb_get_ntohl(tvb, offset);
209 proto_tree_add_text(field_tree, tvb, offset, optlen,
210 "(suboption would go past end of option)");
213 /* XXX - check whether it goes past end of packet */
214 rightedge = tvb_get_ntohl(tvb, offset + 4);
216 proto_tree_add_text(field_tree, tvb, offset, 8,
217 "left edge = %u, right edge = %u", leftedge, rightedge);
218 tcp_info_append_uint(fd, "SLE", leftedge);
219 tcp_info_append_uint(fd, "SRE", rightedge);
225 dissect_tcpopt_echo(const ip_tcp_opt *optp, tvbuff_t *tvb,
226 int offset, guint optlen, frame_data *fd, proto_tree *opt_tree)
230 echo = tvb_get_ntohl(tvb, offset + 2);
231 proto_tree_add_text(opt_tree, tvb, offset, optlen,
232 "%s: %u", optp->name, echo);
233 tcp_info_append_uint(fd, "ECHO", echo);
237 dissect_tcpopt_timestamp(const ip_tcp_opt *optp, tvbuff_t *tvb,
238 int offset, guint optlen, frame_data *fd, proto_tree *opt_tree)
242 tsv = tvb_get_ntohl(tvb, offset + 2);
243 tser = tvb_get_ntohl(tvb, offset + 6);
244 proto_tree_add_text(opt_tree, tvb, offset, optlen,
245 "%s: tsval %u, tsecr %u", optp->name, tsv, tser);
246 tcp_info_append_uint(fd, "TSV", tsv);
247 tcp_info_append_uint(fd, "TSER", tser);
251 dissect_tcpopt_cc(const ip_tcp_opt *optp, tvbuff_t *tvb,
252 int offset, guint optlen, frame_data *fd, proto_tree *opt_tree)
256 cc = tvb_get_ntohl(tvb, offset + 2);
257 proto_tree_add_text(opt_tree, tvb, offset, optlen,
258 "%s: %u", optp->name, cc);
259 tcp_info_append_uint(fd, "CC", cc);
262 static const ip_tcp_opt tcpopts[] = {
281 "Maximum segment size",
285 dissect_tcpopt_maxseg
293 dissect_tcpopt_wscale
306 &ett_tcp_option_sack,
333 dissect_tcpopt_timestamp
369 #define N_TCP_OPTS (sizeof tcpopts / sizeof tcpopts[0])
372 static const true_false_string flags_set_truth = {
378 /* Determine if there is a sub-dissector and call it. This has been */
379 /* separated into a stand alone routine to other protocol dissectors */
380 /* can call to it, ie. socks */
383 decode_tcp_ports(tvbuff_t *tvb, int offset, packet_info *pinfo,
384 proto_tree *tree, int src_port, int dst_port)
388 next_tvb = tvb_new_subset(tvb, offset, -1, -1);
390 /* determine if this packet is part of a conversation and call dissector */
391 /* for the conversation if available */
393 if (try_conversation_dissector(&pinfo->src, &pinfo->dst, PT_TCP,
394 src_port, dst_port, next_tvb, pinfo, tree))
397 /* do lookup with the subdissector table */
398 if (dissector_try_port(subdissector_table, src_port, next_tvb, pinfo, tree) ||
399 dissector_try_port(subdissector_table, dst_port, next_tvb, pinfo, tree))
402 /* do lookup with the heuristic subdissector table */
403 if (dissector_try_heuristic(heur_subdissector_list, next_tvb, pinfo, tree))
406 /* Oh, well, we don't know this; dissect it as data. */
407 dissect_data(next_tvb, 0, pinfo, tree);
412 dissect_tcp(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
415 proto_tree *tcp_tree = NULL, *field_tree = NULL;
418 gchar flags[64] = "<None>";
419 gchar *fstr[] = {"FIN", "SYN", "RST", "PSH", "ACK", "URG", "ECN", "CWR" };
430 guint16 computed_cksum;
431 guint length_remaining;
433 if (check_col(pinfo->fd, COL_PROTOCOL))
434 col_set_str(pinfo->fd, COL_PROTOCOL, "TCP");
436 /* Clear out the Info column. */
437 if (check_col(pinfo->fd, COL_INFO))
438 col_clear(pinfo->fd, COL_INFO);
440 /* Avoids alignment problems on many architectures. */
441 tvb_memcpy(tvb, (guint8 *)&th, offset, sizeof(e_tcphdr));
442 th.th_sport = ntohs(th.th_sport);
443 th.th_dport = ntohs(th.th_dport);
444 th.th_win = ntohs(th.th_win);
445 th.th_sum = ntohs(th.th_sum);
446 th.th_urp = ntohs(th.th_urp);
447 th.th_seq = ntohl(th.th_seq);
448 th.th_ack = ntohl(th.th_ack);
450 /* Export the urgent pointer, for the benefit of protocols such as
452 tcp_urgent_pointer = th.th_urp;
454 if (check_col(pinfo->fd, COL_INFO) || tree) {
455 for (i = 0; i < 8; i++) {
457 if (th.th_flags & bpos) {
459 strcpy(&flags[fpos], ", ");
462 strcpy(&flags[fpos], fstr[i]);
469 hlen = hi_nibble(th.th_off_x2) * 4; /* TCP header length, in bytes */
471 reported_len = tvb_reported_length(tvb);
472 len = tvb_length(tvb);
474 /* Compute the length of data in this segment. */
475 seglen = reported_len - hlen;
477 /* Compute the sequence number of next octet after this segment. */
478 nxtseq = th.th_seq + seglen;
480 if (check_col(pinfo->fd, COL_INFO)) {
481 if (th.th_flags & TH_URG)
482 col_append_fstr(pinfo->fd, COL_INFO, "%s > %s [%s] Seq=%u Ack=%u Win=%u Urg=%u Len=%d",
483 get_tcp_port(th.th_sport), get_tcp_port(th.th_dport), flags,
484 th.th_seq, th.th_ack, th.th_win, th.th_urp, seglen);
486 col_append_fstr(pinfo->fd, COL_INFO, "%s > %s [%s] Seq=%u Ack=%u Win=%u Len=%d",
487 get_tcp_port(th.th_sport), get_tcp_port(th.th_dport), flags,
488 th.th_seq, th.th_ack, th.th_win, seglen);
492 if (tcp_summary_in_tree) {
493 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);
496 ti = proto_tree_add_item(tree, proto_tcp, tvb, offset, hlen, FALSE);
498 tcp_tree = proto_item_add_subtree(ti, ett_tcp);
499 proto_tree_add_uint_format(tcp_tree, hf_tcp_srcport, tvb, offset, 2, th.th_sport,
500 "Source port: %s (%u)", get_tcp_port(th.th_sport), th.th_sport);
501 proto_tree_add_uint_format(tcp_tree, hf_tcp_dstport, tvb, offset + 2, 2, th.th_dport,
502 "Destination port: %s (%u)", get_tcp_port(th.th_dport), th.th_dport);
503 proto_tree_add_uint_hidden(tcp_tree, hf_tcp_port, tvb, offset, 2, th.th_sport);
504 proto_tree_add_uint_hidden(tcp_tree, hf_tcp_port, tvb, offset + 2, 2, th.th_dport);
505 proto_tree_add_uint(tcp_tree, hf_tcp_seq, tvb, offset + 4, 4, th.th_seq);
506 if (nxtseq != th.th_seq)
507 proto_tree_add_uint(tcp_tree, hf_tcp_nxtseq, tvb, offset, 0, nxtseq);
508 if (th.th_flags & TH_ACK)
509 proto_tree_add_uint(tcp_tree, hf_tcp_ack, tvb, offset + 8, 4, th.th_ack);
510 proto_tree_add_uint_format(tcp_tree, hf_tcp_hdr_len, tvb, offset + 12, 1, hlen,
511 "Header length: %u bytes", hlen);
512 tf = proto_tree_add_uint_format(tcp_tree, hf_tcp_flags, tvb, offset + 13, 1,
513 th.th_flags, "Flags: 0x%04x (%s)", th.th_flags, flags);
514 field_tree = proto_item_add_subtree(tf, ett_tcp_flags);
515 proto_tree_add_boolean(field_tree, hf_tcp_flags_cwr, tvb, offset + 13, 1, th.th_flags);
516 proto_tree_add_boolean(field_tree, hf_tcp_flags_ecn, tvb, offset + 13, 1, th.th_flags);
517 proto_tree_add_boolean(field_tree, hf_tcp_flags_urg, tvb, offset + 13, 1, th.th_flags);
518 proto_tree_add_boolean(field_tree, hf_tcp_flags_ack, tvb, offset + 13, 1, th.th_flags);
519 proto_tree_add_boolean(field_tree, hf_tcp_flags_push, tvb, offset + 13, 1, th.th_flags);
520 proto_tree_add_boolean(field_tree, hf_tcp_flags_reset, tvb, offset + 13, 1, th.th_flags);
521 proto_tree_add_boolean(field_tree, hf_tcp_flags_syn, tvb, offset + 13, 1, th.th_flags);
522 proto_tree_add_boolean(field_tree, hf_tcp_flags_fin, tvb, offset + 13, 1, th.th_flags);
523 proto_tree_add_uint(tcp_tree, hf_tcp_window_size, tvb, offset + 14, 2, th.th_win);
524 if (!pinfo->fragmented && len >= reported_len) {
525 /* The packet isn't part of a fragmented datagram and isn't
526 truncated, so we can checksum it.
527 XXX - make a bigger scatter-gather list once we do fragment
530 /* Set up the fields of the pseudo-header. */
531 cksum_vec[0].ptr = pinfo->src.data;
532 cksum_vec[0].len = pinfo->src.len;
533 cksum_vec[1].ptr = pinfo->dst.data;
534 cksum_vec[1].len = pinfo->dst.len;
535 cksum_vec[2].ptr = (const guint8 *)&phdr;
536 switch (pinfo->src.type) {
539 phdr[0] = htonl((IP_PROTO_TCP<<16) + reported_len);
540 cksum_vec[2].len = 4;
544 phdr[0] = htonl(reported_len);
545 phdr[1] = htonl(IP_PROTO_TCP);
546 cksum_vec[2].len = 8;
550 /* TCP runs only atop IPv4 and IPv6.... */
551 g_assert_not_reached();
554 cksum_vec[3].ptr = tvb_get_ptr(tvb, offset, len);
555 cksum_vec[3].len = reported_len;
556 computed_cksum = in_cksum(&cksum_vec[0], 4);
557 if (computed_cksum == 0) {
558 proto_tree_add_uint_format(tcp_tree, hf_tcp_checksum, tvb,
559 offset + 16, 2, th.th_sum, "Checksum: 0x%04x (correct)", th.th_sum);
561 proto_tree_add_item_hidden(tcp_tree, hf_tcp_checksum_bad, tvb,
562 offset + 16, 2, TRUE);
563 proto_tree_add_uint_format(tcp_tree, hf_tcp_checksum, tvb,
564 offset + 16, 2, th.th_sum,
565 "Checksum: 0x%04x (incorrect, should be 0x%04x)", th.th_sum,
566 in_cksum_shouldbe(th.th_sum, computed_cksum));
569 proto_tree_add_uint_format(tcp_tree, hf_tcp_checksum, tvb,
570 offset + 16, 2, th.th_sum, "Checksum: 0x%04x", th.th_sum);
572 if (th.th_flags & TH_URG)
573 proto_tree_add_uint(tcp_tree, hf_tcp_urgent_pointer, tvb, offset + 18, 2, th.th_urp);
576 /* Decode TCP options, if any. */
577 if (tree && hlen > sizeof (e_tcphdr)) {
578 /* There's more than just the fixed-length header. Decode the
580 optlen = hlen - sizeof (e_tcphdr); /* length of options, in bytes */
581 tf = proto_tree_add_text(tcp_tree, tvb, offset + 20, optlen,
582 "Options: (%d bytes)", optlen);
583 field_tree = proto_item_add_subtree(tf, ett_tcp_options);
584 dissect_ip_tcp_options(tvb, offset + 20, optlen,
585 tcpopts, N_TCP_OPTS, TCPOPT_EOL, pinfo->fd, field_tree);
588 /* Skip over header + options */
591 pinfo->ptype = PT_TCP;
592 pinfo->srcport = th.th_sport;
593 pinfo->destport = th.th_dport;
595 /* Check the packet length to see if there's more data
596 (it could be an ACK-only packet) */
597 length_remaining = tvb_length_remaining(tvb, offset);
598 if (length_remaining != 0) {
599 if (th.th_flags & TH_RST) {
603 * 4.2.2.12 RST Segment: RFC-793 Section 3.4
605 * A TCP SHOULD allow a received RST segment to include data.
608 * It has been suggested that a RST segment could contain
609 * ASCII text that encoded and explained the cause of the
610 * RST. No standard has yet been established for such
613 * so for segments with RST we just display the data as text.
615 proto_tree_add_text(tcp_tree, tvb, offset, length_remaining,
617 tvb_format_text(tvb, offset, length_remaining));
619 decode_tcp_ports( tvb, offset, pinfo, tree, th.th_sport, th.th_dport);
622 if( data_out_file ) {
623 reassemble_tcp( th.th_seq, /* sequence number */
624 seglen, /* data length */
625 tvb_get_ptr(tvb, offset, length_remaining), /* data */
626 length_remaining, /* captured data length */
627 ( th.th_flags & TH_SYN ), /* is syn set? */
636 proto_register_tcp(void)
638 static hf_register_info hf[] = {
641 { "Source Port", "tcp.srcport", FT_UINT16, BASE_DEC, NULL, 0x0,
645 { "Destination Port", "tcp.dstport", FT_UINT16, BASE_DEC, NULL, 0x0,
649 { "Source or Destination Port", "tcp.port", FT_UINT16, BASE_DEC, NULL, 0x0,
653 { "Sequence number", "tcp.seq", FT_UINT32, BASE_DEC, NULL, 0x0,
657 { "Next sequence number", "tcp.nxtseq", FT_UINT32, BASE_DEC, NULL, 0x0,
661 { "Acknowledgement number", "tcp.ack", FT_UINT32, BASE_DEC, NULL, 0x0,
665 { "Header Length", "tcp.hdr_len", FT_UINT8, BASE_DEC, NULL, 0x0,
669 { "Flags", "tcp.flags", FT_UINT8, BASE_HEX, NULL, 0x0,
673 { "Congestion Window Reduced (CWR)", "tcp.flags.cwr", FT_BOOLEAN, 8, TFS(&flags_set_truth), TH_CWR,
677 { "ECN-Echo", "tcp.flags.ecn", FT_BOOLEAN, 8, TFS(&flags_set_truth), TH_ECN,
681 { "Urgent", "tcp.flags.urg", FT_BOOLEAN, 8, TFS(&flags_set_truth), TH_URG,
685 { "Acknowledgment", "tcp.flags.ack", FT_BOOLEAN, 8, TFS(&flags_set_truth), TH_ACK,
688 { &hf_tcp_flags_push,
689 { "Push", "tcp.flags.push", FT_BOOLEAN, 8, TFS(&flags_set_truth), TH_PUSH,
692 { &hf_tcp_flags_reset,
693 { "Reset", "tcp.flags.reset", FT_BOOLEAN, 8, TFS(&flags_set_truth), TH_RST,
697 { "Syn", "tcp.flags.syn", FT_BOOLEAN, 8, TFS(&flags_set_truth), TH_SYN,
701 { "Fin", "tcp.flags.fin", FT_BOOLEAN, 8, TFS(&flags_set_truth), TH_FIN,
704 { &hf_tcp_window_size,
705 { "Window size", "tcp.window_size", FT_UINT16, BASE_DEC, NULL, 0x0,
709 { "Checksum", "tcp.checksum", FT_UINT16, BASE_HEX, NULL, 0x0,
712 { &hf_tcp_checksum_bad,
713 { "Bad Checksum", "tcp.checksum_bad", FT_BOOLEAN, BASE_NONE, NULL, 0x0,
716 { &hf_tcp_urgent_pointer,
717 { "Urgent pointer", "tcp.urgent_pointer", FT_UINT16, BASE_DEC, NULL, 0x0,
720 static gint *ett[] = {
724 &ett_tcp_option_sack,
726 module_t *tcp_module;
728 proto_tcp = proto_register_protocol("Transmission Control Protocol",
730 proto_register_field_array(proto_tcp, hf, array_length(hf));
731 proto_register_subtree_array(ett, array_length(ett));
733 /* subdissector code */
734 subdissector_table = register_dissector_table("tcp.port");
735 register_heur_dissector_list("tcp", &heur_subdissector_list);
736 register_conv_dissector_list("tcp", &conv_subdissector_list);
738 /* Register configuration preferences */
739 tcp_module = prefs_register_protocol(proto_tcp, NULL);
740 prefs_register_bool_preference(tcp_module, "tcp_summary_in_tree",
741 "Show TCP summary in protocol tree",
742 "Whether the TCP summary line should be shown in the protocol tree",
743 &tcp_summary_in_tree);
747 proto_reg_handoff_tcp(void)
749 dissector_add("ip.proto", IP_PROTO_TCP, dissect_tcp, proto_tcp);