The Tcpdump Group git mirrors - tcpdump/blob - print-tcp.c

   1 /*      $NetBSD: print-tcp.c,v 1.9 2007/07/26 18:15:12 plunky Exp $     */
   2
   3 /*
   4  * Copyright (c) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997
   5  *      The Regents of the University of California.  All rights reserved.
   6  *
   7  * Copyright (c) 1999-2004 The tcpdump.org project
   8  *
   9  * Redistribution and use in source and binary forms, with or without
  10  * modification, are permitted provided that: (1) source code distributions
  11  * retain the above copyright notice and this paragraph in its entirety, (2)
  12  * distributions including binary code include the above copyright notice and
  13  * this paragraph in its entirety in the documentation or other materials
  14  * provided with the distribution, and (3) all advertising materials mentioning
  15  * features or use of this software display the following acknowledgement:
  16  * ``This product includes software developed by the University of California,
  17  * Lawrence Berkeley Laboratory and its contributors.'' Neither the name of
  18  * the University nor the names of its contributors may be used to endorse
  19  * or promote products derived from this software without specific prior
  20  * written permission.
  21  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
  22  * WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
  23  * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
  24  */
  25
  26 #ifndef lint
  27 static const char rcsid[] _U_ =
  28 "@(#) $Header: /tcpdump/master/tcpdump/print-tcp.c,v 1.135 2008-11-09 23:35:03 mcr Exp $ (LBL)";
  29 #else
  30 __RCSID("$NetBSD: print-tcp.c,v 1.8 2007/07/24 11:53:48 drochner Exp $");
  31 #endif
  32
  33 #ifdef HAVE_CONFIG_H
  34 #include "config.h"
  35 #endif
  36
  37 #include <tcpdump-stdinc.h>
  38
  39 #include <stdio.h>
  40 #include <stdlib.h>
  41 #include <string.h>
  42
  43 #include "interface.h"
  44 #include "addrtoname.h"
  45 #include "extract.h"
  46
  47 #include "tcp.h"
  48
  49 #include "ip.h"
  50 #ifdef INET6
  51 #include "ip6.h"
  52 #endif
  53 #include "ipproto.h"
  54 #include "rpc_auth.h"
  55 #include "rpc_msg.h"
  56
  57 #include "nameser.h"
  58
  59 #ifdef HAVE_LIBCRYPTO
  60 #include <openssl/md5.h>
  61 #include <signature.h>
  62
  63 static int tcp_verify_signature(const struct ip *ip, const struct tcphdr *tp,
  64                                 const u_char *data, int length, const u_char *rcvsig);
  65 #endif
  66
  67 static void print_tcp_rst_data(register const u_char *sp, u_int length);
  68
  69 #define MAX_RST_DATA_LEN        30
  70
  71
  72 struct tha {
  73 #ifndef INET6
  74         struct in_addr src;
  75         struct in_addr dst;
  76 #else
  77         struct in6_addr src;
  78         struct in6_addr dst;
  79 #endif /*INET6*/
  80         u_int port;
  81 };
  82
  83 struct tcp_seq_hash {
  84         struct tcp_seq_hash *nxt;
  85         struct tha addr;
  86         tcp_seq seq;
  87         tcp_seq ack;
  88 };
  89
  90 #define TSEQ_HASHSIZE 919
  91
  92 /* These tcp optinos do not have the size octet */
  93 #define ZEROLENOPT(o) ((o) == TCPOPT_EOL || (o) == TCPOPT_NOP)
  94
  95 static struct tcp_seq_hash tcp_seq_hash[TSEQ_HASHSIZE];
  96
  97 struct tok tcp_flag_values[] = {
  98         { TH_FIN, "F" },
  99         { TH_SYN, "S" },
 100         { TH_RST, "R" },
 101         { TH_PUSH, "P" },
 102         { TH_ACK, "." },
 103         { TH_URG, "U" },
 104         { TH_ECNECHO, "E" },
 105         { TH_CWR, "W" },
 106         { 0, NULL }
 107 };
 108
 109 struct tok tcp_option_values[] = {
 110         { TCPOPT_EOL, "eol" },
 111         { TCPOPT_NOP, "nop" },
 112         { TCPOPT_MAXSEG, "mss" },
 113         { TCPOPT_WSCALE, "wscale" },
 114         { TCPOPT_SACKOK, "sackOK" },
 115         { TCPOPT_SACK, "sack" },
 116         { TCPOPT_ECHO, "echo" },
 117         { TCPOPT_ECHOREPLY, "echoreply" },
 118         { TCPOPT_TIMESTAMP, "TS" },
 119         { TCPOPT_CC, "cc" },
 120         { TCPOPT_CCNEW, "ccnew" },
 121         { TCPOPT_CCECHO, "" },
 122         { TCPOPT_SIGNATURE, "md5" },
 123         { TCPOPT_AUTH, "enhanced auth" },
 124         { 0, NULL }
 125 };
 126
 127 static int tcp_cksum(register const struct ip *ip,
 128                      register const struct tcphdr *tp,
 129                      register u_int len)
 130 {
 131         union phu {
 132                 struct phdr {
 133                         u_int32_t src;
 134                         u_int32_t dst;
 135                         u_char mbz;
 136                         u_char proto;
 137                         u_int16_t len;
 138                 } ph;
 139                 u_int16_t pa[6];
 140         } phu;
 141         const u_int16_t *sp;
 142
 143         /* pseudo-header.. */
 144         phu.ph.len = htons((u_int16_t)len);
 145         phu.ph.mbz = 0;
 146         phu.ph.proto = IPPROTO_TCP;
 147         memcpy(&phu.ph.src, &ip->ip_src.s_addr, sizeof(u_int32_t));
 148         if (IP_HL(ip) == 5)
 149                 memcpy(&phu.ph.dst, &ip->ip_dst.s_addr, sizeof(u_int32_t));
 150         else
 151                 phu.ph.dst = ip_finddst(ip);
 152
 153         sp = &phu.pa[0];
 154         return in_cksum((u_short *)tp, len,
 155                         sp[0]+sp[1]+sp[2]+sp[3]+sp[4]+sp[5]);
 156 }
 157
 158 #ifdef INET6
 159 static int tcp6_cksum(const struct ip6_hdr *ip6, const struct tcphdr *tp,
 160                       u_int len)
 161 {
 162         size_t i;
 163         u_int32_t sum = 0;
 164         union {
 165                 struct {
 166                         struct in6_addr ph_src;
 167                         struct in6_addr ph_dst;
 168                         u_int32_t       ph_len;
 169                         u_int8_t        ph_zero[3];
 170                         u_int8_t        ph_nxt;
 171                 } ph;
 172                 u_int16_t pa[20];
 173         } phu;
 174
 175         /* pseudo-header */
 176         memset(&phu, 0, sizeof(phu));
 177         phu.ph.ph_src = ip6->ip6_src;
 178         phu.ph.ph_dst = ip6->ip6_dst;
 179         phu.ph.ph_len = htonl(len);
 180         phu.ph.ph_nxt = IPPROTO_TCP;
 181
 182         for (i = 0; i < sizeof(phu.pa) / sizeof(phu.pa[0]); i++)
 183                 sum += phu.pa[i];
 184
 185         return in_cksum((u_short *)tp, len, sum);
 186 }
 187 #endif
 188
 189 void
 190 tcp_print(register const u_char *bp, register u_int length,
 191           register const u_char *bp2, int fragmented)
 192 {
 193         register const struct tcphdr *tp;
 194         register const struct ip *ip;
 195         register u_char flags;
 196         register u_int hlen;
 197         register char ch;
 198         u_int16_t sport, dport, win, urp;
 199         u_int32_t seq, ack, thseq, thack;
 200         int threv;
 201 #ifdef INET6
 202         register const struct ip6_hdr *ip6;
 203 #endif
 204
 205         tp = (struct tcphdr *)bp;
 206         ip = (struct ip *)bp2;
 207 #ifdef INET6
 208         if (IP_V(ip) == 6)
 209                 ip6 = (struct ip6_hdr *)bp2;
 210         else
 211                 ip6 = NULL;
 212 #endif /*INET6*/
 213         ch = '\0';
 214         if (!TTEST(tp->th_dport)) {
 215                 (void)printf("%s > %s: [|tcp]",
 216                              ipaddr_string(&ip->ip_src),
 217                              ipaddr_string(&ip->ip_dst));
 218                 return;
 219         }
 220
 221         sport = EXTRACT_16BITS(&tp->th_sport);
 222         dport = EXTRACT_16BITS(&tp->th_dport);
 223
 224         hlen = TH_OFF(tp) * 4;
 225
 226         /*
 227          * If data present, header length valid, and NFS port used,
 228          * assume NFS.
 229          * Pass offset of data plus 4 bytes for RPC TCP msg length
 230          * to NFS print routines.
 231          */
 232         if (!qflag && hlen >= sizeof(*tp) && hlen <= length &&
 233             (length - hlen) >= 4) {
 234                 u_char *fraglenp;
 235                 u_int32_t fraglen;
 236                 register struct sunrpc_msg *rp;
 237                 enum sunrpc_msg_type direction;
 238
 239                 fraglenp = (u_char *)tp + hlen;
 240                 if (TTEST2(*fraglenp, 4)) {
 241                         fraglen = EXTRACT_32BITS(fraglenp) & 0x7FFFFFFF;
 242                         if (fraglen > (length - hlen) - 4)
 243                                 fraglen = (length - hlen) - 4;
 244                         rp = (struct sunrpc_msg *)(fraglenp + 4);
 245                         if (TTEST(rp->rm_direction)) {
 246                                 direction = (enum sunrpc_msg_type)EXTRACT_32BITS(&rp->rm_direction);
 247                                 if (dport == NFS_PORT &&
 248                                     direction == SUNRPC_CALL) {
 249                                         nfsreq_print((u_char *)rp, fraglen,
 250                                             (u_char *)ip);
 251                                         return;
 252                                 }
 253                                 if (sport == NFS_PORT &&
 254                                     direction == SUNRPC_REPLY) {
 255                                         nfsreply_print((u_char *)rp, fraglen,
 256                                             (u_char *)ip);
 257                                         return;
 258                                 }
 259                         }
 260                 }
 261         }
 262 #ifdef INET6
 263         if (ip6) {
 264                 if (ip6->ip6_nxt == IPPROTO_TCP) {
 265                         (void)printf("%s.%s > %s.%s: ",
 266                                      ip6addr_string(&ip6->ip6_src),
 267                                      tcpport_string(sport),
 268                                      ip6addr_string(&ip6->ip6_dst),
 269                                      tcpport_string(dport));
 270                 } else {
 271                         (void)printf("%s > %s: ",
 272                                      tcpport_string(sport), tcpport_string(dport));
 273                 }
 274         } else
 275 #endif /*INET6*/
 276         {
 277                 if (ip->ip_p == IPPROTO_TCP) {
 278                         (void)printf("%s.%s > %s.%s: ",
 279                                      ipaddr_string(&ip->ip_src),
 280                                      tcpport_string(sport),
 281                                      ipaddr_string(&ip->ip_dst),
 282                                      tcpport_string(dport));
 283                 } else {
 284                         (void)printf("%s > %s: ",
 285                                      tcpport_string(sport), tcpport_string(dport));
 286                 }
 287         }
 288
 289         if (hlen < sizeof(*tp)) {
 290                 (void)printf(" tcp %d [bad hdr length %u - too short, < %lu]",
 291                              length - hlen, hlen, (unsigned long)sizeof(*tp));
 292                 return;
 293         }
 294
 295         TCHECK(*tp);
 296
 297         seq = EXTRACT_32BITS(&tp->th_seq);
 298         ack = EXTRACT_32BITS(&tp->th_ack);
 299         win = EXTRACT_16BITS(&tp->th_win);
 300         urp = EXTRACT_16BITS(&tp->th_urp);
 301
 302         if (qflag) {
 303                 (void)printf("tcp %d", length - hlen);
 304                 if (hlen > length) {
 305                         (void)printf(" [bad hdr length %u - too long, > %u]",
 306                                      hlen, length);
 307                 }
 308                 return;
 309         }
 310
 311         flags = tp->th_flags;
 312         printf("Flags [%s]", bittok2str_nosep(tcp_flag_values, "none", flags));
 313
 314         if (!Sflag && (flags & TH_ACK)) {
 315                 register struct tcp_seq_hash *th;
 316                 const void *src, *dst;
 317                 register int rev;
 318                 struct tha tha;
 319                 /*
 320                  * Find (or record) the initial sequence numbers for
 321                  * this conversation.  (we pick an arbitrary
 322                  * collating order so there's only one entry for
 323                  * both directions).
 324                  */
 325 #ifdef INET6
 326                 memset(&tha, 0, sizeof(tha));
 327                 rev = 0;
 328                 if (ip6) {
 329                         src = &ip6->ip6_src;
 330                         dst = &ip6->ip6_dst;
 331                         if (sport > dport)
 332                                 rev = 1;
 333                         else if (sport == dport) {
 334                                 if (memcmp(src, dst, sizeof ip6->ip6_dst) > 0)
 335                                         rev = 1;
 336                         }
 337                         if (rev) {
 338                                 memcpy(&tha.src, dst, sizeof ip6->ip6_dst);
 339                                 memcpy(&tha.dst, src, sizeof ip6->ip6_src);
 340                                 tha.port = dport << 16 | sport;
 341                         } else {
 342                                 memcpy(&tha.dst, dst, sizeof ip6->ip6_dst);
 343                                 memcpy(&tha.src, src, sizeof ip6->ip6_src);
 344                                 tha.port = sport << 16 | dport;
 345                         }
 346                 } else {
 347                         src = &ip->ip_src;
 348                         dst = &ip->ip_dst;
 349                         if (sport > dport)
 350                                 rev = 1;
 351                         else if (sport == dport) {
 352                                 if (memcmp(src, dst, sizeof ip->ip_dst) > 0)
 353                                         rev = 1;
 354                         }
 355                         if (rev) {
 356                                 memcpy(&tha.src, dst, sizeof ip->ip_dst);
 357                                 memcpy(&tha.dst, src, sizeof ip->ip_src);
 358                                 tha.port = dport << 16 | sport;
 359                         } else {
 360                                 memcpy(&tha.dst, dst, sizeof ip->ip_dst);
 361                                 memcpy(&tha.src, src, sizeof ip->ip_src);
 362                                 tha.port = sport << 16 | dport;
 363                         }
 364                 }
 365 #else
 366                 rev = 0;
 367                 src = &ip->ip_src;
 368                 dst = &ip->ip_dst;
 369                 if (sport > dport)
 370                         rev = 1;
 371                 else if (sport == dport) {
 372                         if (memcmp(src, dst, sizeof ip->ip_dst) > 0)
 373                                 rev = 1;
 374                 }
 375                 if (rev) {
 376                         memcpy(&tha.src, dst, sizeof ip->ip_dst);
 377                         memcpy(&tha.dst, src, sizeof ip->ip_src);
 378                         tha.port = dport << 16 | sport;
 379                 } else {
 380                         memcpy(&tha.dst, dst, sizeof ip->ip_dst);
 381                         memcpy(&tha.src, src, sizeof ip->ip_src);
 382                         tha.port = sport << 16 | dport;
 383                 }
 384 #endif
 385
 386                 threv = rev;
 387                 for (th = &tcp_seq_hash[tha.port % TSEQ_HASHSIZE];
 388                      th->nxt; th = th->nxt)
 389                         if (memcmp((char *)&tha, (char *)&th->addr,
 390                                    sizeof(th->addr)) == 0)
 391                                 break;
 392
 393                 if (!th->nxt || (flags & TH_SYN)) {
 394                         /* didn't find it or new conversation */
 395                         if (th->nxt == NULL) {
 396                                 th->nxt = (struct tcp_seq_hash *)
 397                                         calloc(1, sizeof(*th));
 398                                 if (th->nxt == NULL)
 399                                         error("tcp_print: calloc");
 400                         }
 401                         th->addr = tha;
 402                         if (rev)
 403                                 th->ack = seq, th->seq = ack - 1;
 404                         else
 405                                 th->seq = seq, th->ack = ack - 1;
 406                 } else {
 407                         if (rev)
 408                                 seq -= th->ack, ack -= th->seq;
 409                         else
 410                                 seq -= th->seq, ack -= th->ack;
 411                 }
 412
 413                 thseq = th->seq;
 414                 thack = th->ack;
 415         } else {
 416                 /*fool gcc*/
 417                 thseq = thack = threv = 0;
 418         }
 419         if (hlen > length) {
 420                 (void)printf(" [bad hdr length %u - too long, > %u]",
 421                              hlen, length);
 422                 return;
 423         }
 424
 425         if (IP_V(ip) == 4 && vflag && !Kflag && !fragmented) {
 426                 u_int16_t sum, tcp_sum;
 427                 if (TTEST2(tp->th_sport, length)) {
 428                         sum = tcp_cksum(ip, tp, length);
 429
 430                         (void)printf(", cksum 0x%04x",EXTRACT_16BITS(&tp->th_sum));
 431                         if (sum != 0) {
 432                                 tcp_sum = EXTRACT_16BITS(&tp->th_sum);
 433                                 (void)printf(" (incorrect -> 0x%04x)",in_cksum_shouldbe(tcp_sum, sum));
 434                         } else
 435                                 (void)printf(" (correct)");
 436                 }
 437         }
 438 #ifdef INET6
 439         if (IP_V(ip) == 6 && ip6->ip6_plen && vflag && !Kflag && !fragmented) {
 440                 u_int16_t sum,tcp_sum;
 441                 if (TTEST2(tp->th_sport, length)) {
 442                         sum = tcp6_cksum(ip6, tp, length);
 443                         (void)printf(", cksum 0x%04x",EXTRACT_16BITS(&tp->th_sum));
 444                         if (sum != 0) {
 445                                 tcp_sum = EXTRACT_16BITS(&tp->th_sum);
 446                                 (void)printf(" (incorrect -> 0x%04x)",in_cksum_shouldbe(tcp_sum, sum));
 447                         } else
 448                                 (void)printf(" (correct)");
 449
 450                 }
 451         }
 452 #endif
 453
 454         length -= hlen;
 455         if (vflag > 1 || flags & (TH_SYN | TH_FIN | TH_RST)) {
 456                 (void)printf(", seq %u", seq);
 457
 458                 if (length > 0) {
 459                         (void)printf(":%u", seq + length);
 460                 }
 461         }
 462
 463         if (flags & TH_ACK) {
 464                 (void)printf(", ack %u", ack);
 465         }
 466
 467         (void)printf(", win %d", win);
 468
 469         if (flags & TH_URG)
 470                 (void)printf(", urg %d", urp);
 471         /*
 472          * Handle any options.
 473          */
 474         if (hlen > sizeof(*tp)) {
 475                 register const u_char *cp;
 476                 register u_int i, opt, datalen;
 477                 register u_int len;
 478
 479                 hlen -= sizeof(*tp);
 480                 cp = (const u_char *)tp + sizeof(*tp);
 481                 printf(", options [");
 482                 while (hlen > 0) {
 483                         if (ch != '\0')
 484                                 putchar(ch);
 485                         TCHECK(*cp);
 486                         opt = *cp++;
 487                         if (ZEROLENOPT(opt))
 488                                 len = 1;
 489                         else {
 490                                 TCHECK(*cp);
 491                                 len = *cp++;    /* total including type, len */
 492                                 if (len < 2 || len > hlen)
 493                                         goto bad;
 494                                 --hlen;         /* account for length byte */
 495                         }
 496                         --hlen;                 /* account for type byte */
 497                         datalen = 0;
 498
 499 /* Bail if "l" bytes of data are not left or were not captured  */
 500 #define LENCHECK(l) { if ((l) > hlen) goto bad; TCHECK2(*cp, l); }
 501
 502
 503                         printf("%s", tok2str(tcp_option_values, "Unknown Option %u", opt));
 504
 505                         switch (opt) {
 506
 507                         case TCPOPT_MAXSEG:
 508                                 datalen = 2;
 509                                 LENCHECK(datalen);
 510                                 (void)printf(" %u", EXTRACT_16BITS(cp));
 511                                 break;
 512
 513                         case TCPOPT_WSCALE:
 514                                 datalen = 1;
 515                                 LENCHECK(datalen);
 516                                 (void)printf(" %u", *cp);
 517                                 break;
 518
 519                         case TCPOPT_SACK:
 520                                 datalen = len - 2;
 521                                 if (datalen % 8 != 0) {
 522                                         (void)printf("malformed sack");
 523                                 } else {
 524                                         u_int32_t s, e;
 525
 526                                         (void)printf(" %d ", datalen / 8);
 527                                         for (i = 0; i < datalen; i += 8) {
 528                                                 LENCHECK(i + 4);
 529                                                 s = EXTRACT_32BITS(cp + i);
 530                                                 LENCHECK(i + 8);
 531                                                 e = EXTRACT_32BITS(cp + i + 4);
 532                                                 if (threv) {
 533                                                         s -= thseq;
 534                                                         e -= thseq;
 535                                                 } else {
 536                                                         s -= thack;
 537                                                         e -= thack;
 538                                                 }
 539                                                 (void)printf("{%u:%u}", s, e);
 540                                         }
 541                                 }
 542                                 break;
 543
 544                         case TCPOPT_CC:
 545                         case TCPOPT_CCNEW:
 546                         case TCPOPT_CCECHO:
 547                         case TCPOPT_ECHO:
 548                         case TCPOPT_ECHOREPLY:
 549
 550                                 /*
 551                                  * those options share their semantics.
 552                                  * fall through
 553                                  */
 554                                 datalen = 4;
 555                                 LENCHECK(datalen);
 556                                 (void)printf(" %u", EXTRACT_32BITS(cp));
 557                                 break;
 558
 559                         case TCPOPT_TIMESTAMP:
 560                                 datalen = 8;
 561                                 LENCHECK(datalen);
 562                                 (void)printf(" val %u ecr %u",
 563                                              EXTRACT_32BITS(cp),
 564                                              EXTRACT_32BITS(cp + 4));
 565                                 break;
 566
 567                         case TCPOPT_SIGNATURE:
 568                                 datalen = TCP_SIGLEN;
 569                                 LENCHECK(datalen);
 570 #ifdef HAVE_LIBCRYPTO
 571                                 switch (tcp_verify_signature(ip, tp,
 572                                                              bp + TH_OFF(tp) * 4, length, cp)) {
 573
 574                                 case SIGNATURE_VALID:
 575                                         (void)printf("valid");
 576                                         break;
 577
 578                                 case SIGNATURE_INVALID:
 579                                         (void)printf("invalid");
 580                                         break;
 581
 582                                 case CANT_CHECK_SIGNATURE:
 583                                         (void)printf("can't check - ");
 584                                         for (i = 0; i < TCP_SIGLEN; ++i)
 585                                                 (void)printf("%02x", cp[i]);
 586                                         break;
 587                                 }
 588 #else
 589                                 for (i = 0; i < TCP_SIGLEN; ++i)
 590                                         (void)printf("%02x", cp[i]);
 591 #endif
 592                                 break;
 593
 594                         case TCPOPT_AUTH:
 595                                 (void)printf("keyid %d", *cp++);
 596                                 datalen = len - 3;
 597                                 for (i = 0; i < datalen; ++i) {
 598                                         LENCHECK(i);
 599                                         (void)printf("%02x", cp[i]);
 600                                 }
 601                                 break;
 602
 603
 604                         case TCPOPT_EOL:
 605                         case TCPOPT_NOP:
 606                         case TCPOPT_SACKOK:
 607                                 /*
 608                                  * Nothing interesting.
 609                                  * fall through
 610                                  */
 611                                 break;
 612
 613                         default:
 614                                 datalen = len - 2;
 615                                 for (i = 0; i < datalen; ++i) {
 616                                         LENCHECK(i);
 617                                         (void)printf("%02x", cp[i]);
 618                                 }
 619                                 break;
 620                         }
 621
 622                         /* Account for data printed */
 623                         cp += datalen;
 624                         hlen -= datalen;
 625
 626                         /* Check specification against observed length */
 627                         ++datalen;                      /* option octet */
 628                         if (!ZEROLENOPT(opt))
 629                                 ++datalen;              /* size octet */
 630                         if (datalen != len)
 631                                 (void)printf("[len %d]", len);
 632                         ch = ',';
 633                         if (opt == TCPOPT_EOL)
 634                                 break;
 635                 }
 636                 putchar(']');
 637         }
 638
 639         /*
 640          * Print length field before crawling down the stack.
 641          */
 642         printf(", length %u", length);
 643
 644         if (length <= 0)
 645                 return;
 646
 647         /*
 648          * Decode payload if necessary.
 649          */
 650         bp += TH_OFF(tp) * 4;
 651         if ((flags & TH_RST) && vflag) {
 652                 print_tcp_rst_data(bp, length);
 653                 return;
 654         }
 655
 656         if (sport == TELNET_PORT || dport == TELNET_PORT) {
 657                 if (!qflag && vflag)
 658                         telnet_print(bp, length);
 659         } else if (sport == BGP_PORT || dport == BGP_PORT)
 660                 bgp_print(bp, length);
 661         else if (sport == PPTP_PORT || dport == PPTP_PORT)
 662                 pptp_print(bp);
 663 #ifdef TCPDUMP_DO_SMB
 664         else if (sport == NETBIOS_SSN_PORT || dport == NETBIOS_SSN_PORT)
 665                 nbt_tcp_print(bp, length);
 666         else if (sport == SMB_PORT || dport == SMB_PORT)
 667                 smb_tcp_print(bp, length);
 668 #endif
 669         else if (sport == BEEP_PORT || dport == BEEP_PORT)
 670                 beep_print(bp, length);
 671         else if (length > 2 &&
 672                  (sport == NAMESERVER_PORT || dport == NAMESERVER_PORT ||
 673                   sport == MULTICASTDNS_PORT || dport == MULTICASTDNS_PORT)) {
 674                 /*
 675                  * TCP DNS query has 2byte length at the head.
 676                  * XXX packet could be unaligned, it can go strange
 677                  */
 678                 ns_print(bp + 2, length - 2, 0);
 679         } else if (sport == MSDP_PORT || dport == MSDP_PORT) {
 680                 msdp_print(bp, length);
 681         }
 682         else if (length > 0 && (sport == LDP_PORT || dport == LDP_PORT)) {
 683                 ldp_print(bp, length);
 684         }
 685
 686         return;
 687  bad:
 688         fputs("[bad opt]", stdout);
 689         if (ch != '\0')
 690                 putchar('>');
 691         return;
 692  trunc:
 693         fputs("[|tcp]", stdout);
 694         if (ch != '\0')
 695                 putchar('>');
 696 }
 697
 698 /*
 699  * RFC1122 says the following on data in RST segments:
 700  *
 701  *         4.2.2.12  RST Segment: RFC-793 Section 3.4
 702  *
 703  *            A TCP SHOULD allow a received RST segment to include data.
 704  *
 705  *            DISCUSSION
 706  *                 It has been suggested that a RST segment could contain
 707  *                 ASCII text that encoded and explained the cause of the
 708  *                 RST.  No standard has yet been established for such
 709  *                 data.
 710  *
 711  */
 712
 713 static void
 714 print_tcp_rst_data(register const u_char *sp, u_int length)
 715 {
 716         int c;
 717
 718         if (TTEST2(*sp, length))
 719                 printf(" [RST");
 720         else
 721                 printf(" [!RST");
 722         if (length > MAX_RST_DATA_LEN) {
 723                 length = MAX_RST_DATA_LEN;      /* can use -X for longer */
 724                 putchar('+');                   /* indicate we truncate */
 725         }
 726         putchar(' ');
 727         while (length-- && sp <= snapend) {
 728                 c = *sp++;
 729                 safeputchar(c);
 730         }
 731         putchar(']');
 732 }
 733
 734 #ifdef HAVE_LIBCRYPTO
 735 static int
 736 tcp_verify_signature(const struct ip *ip, const struct tcphdr *tp,
 737                      const u_char *data, int length, const u_char *rcvsig)
 738 {
 739         struct tcphdr tp1;
 740         u_char sig[TCP_SIGLEN];
 741         char zero_proto = 0;
 742         MD5_CTX ctx;
 743         u_int16_t savecsum, tlen;
 744 #ifdef INET6
 745         struct ip6_hdr *ip6;
 746         u_int32_t len32;
 747         u_int8_t nxt;
 748 #endif
 749
 750         if (data + length > snapend) {
 751                 printf("snaplen too short, ");
 752                 return (CANT_CHECK_SIGNATURE);
 753         }
 754
 755         tp1 = *tp;
 756
 757         if (sigsecret == NULL) {
 758                 printf("shared secret not supplied with -M, ");
 759                 return (CANT_CHECK_SIGNATURE);
 760         }
 761
 762         MD5_Init(&ctx);
 763         /*
 764          * Step 1: Update MD5 hash with IP pseudo-header.
 765          */
 766         if (IP_V(ip) == 4) {
 767                 MD5_Update(&ctx, (char *)&ip->ip_src, sizeof(ip->ip_src));
 768                 MD5_Update(&ctx, (char *)&ip->ip_dst, sizeof(ip->ip_dst));
 769                 MD5_Update(&ctx, (char *)&zero_proto, sizeof(zero_proto));
 770                 MD5_Update(&ctx, (char *)&ip->ip_p, sizeof(ip->ip_p));
 771                 tlen = EXTRACT_16BITS(&ip->ip_len) - IP_HL(ip) * 4;
 772                 tlen = htons(tlen);
 773                 MD5_Update(&ctx, (char *)&tlen, sizeof(tlen));
 774 #ifdef INET6
 775         } else if (IP_V(ip) == 6) {
 776                 ip6 = (struct ip6_hdr *)ip;
 777                 MD5_Update(&ctx, (char *)&ip6->ip6_src, sizeof(ip6->ip6_src));
 778                 MD5_Update(&ctx, (char *)&ip6->ip6_dst, sizeof(ip6->ip6_dst));
 779                 len32 = htonl(ntohs(ip6->ip6_plen));
 780                 MD5_Update(&ctx, (char *)&len32, sizeof(len32));
 781                 nxt = 0;
 782                 MD5_Update(&ctx, (char *)&nxt, sizeof(nxt));
 783                 MD5_Update(&ctx, (char *)&nxt, sizeof(nxt));
 784                 MD5_Update(&ctx, (char *)&nxt, sizeof(nxt));
 785                 nxt = IPPROTO_TCP;
 786                 MD5_Update(&ctx, (char *)&nxt, sizeof(nxt));
 787 #endif
 788         } else {
 789 #ifdef INET6
 790                 printf("IP version not 4 or 6, ");
 791 #else
 792                 printf("IP version not 4, ");
 793 #endif
 794                 return (CANT_CHECK_SIGNATURE);
 795         }
 796
 797         /*
 798          * Step 2: Update MD5 hash with TCP header, excluding options.
 799          * The TCP checksum must be set to zero.
 800          */
 801         savecsum = tp1.th_sum;
 802         tp1.th_sum = 0;
 803         MD5_Update(&ctx, (char *)&tp1, sizeof(struct tcphdr));
 804         tp1.th_sum = savecsum;
 805         /*
 806          * Step 3: Update MD5 hash with TCP segment data, if present.
 807          */
 808         if (length > 0)
 809                 MD5_Update(&ctx, data, length);
 810         /*
 811          * Step 4: Update MD5 hash with shared secret.
 812          */
 813         MD5_Update(&ctx, sigsecret, strlen(sigsecret));
 814         MD5_Final(sig, &ctx);
 815
 816         if (memcmp(rcvsig, sig, TCP_SIGLEN) == 0)
 817                 return (SIGNATURE_VALID);
 818         else
 819                 return (SIGNATURE_INVALID);
 820 }
 821 #endif /* HAVE_LIBCRYPTO */
 822
 823 /*
 824  * Local Variables:
 825  * c-style: whitesmith
 826  * c-basic-offset: 8
 827  * End:
 828  */