/* packet-tcp.c * Routines for TCP packet disassembly * * $Id: packet-tcp.c,v 1.79 2000/08/07 03:21:15 guy Exp $ * * Ethereal - Network traffic analyzer * By Gerald Combs * 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 #endif #ifdef HAVE_NETINET_IN_H # include #endif #include #include #include "globals.h" #include "resolv.h" #include "follow.h" #include "prefs.h" #ifdef NEED_SNPRINTF_H # ifdef HAVE_STDARG_H # include # else # include # endif # include "snprintf.h" #endif #include "plugins.h" #include "packet-tcp.h" #include "packet-ip.h" #include "conversation.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_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 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] = ""; gchar *fstr[] = {"FIN", "SYN", "RST", "PSH", "ACK", "URG"}; gint fpos = 0, i; guint bpos; guint hlen; guint optlen; guint packet_max = pi.len; /* 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 < 6; 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_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_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); }