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

   1 /*
   2  * Copyright (c) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997
   3  *      The Regents of the University of California.  All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that: (1) source code distributions
   7  * retain the above copyright notice and this paragraph in its entirety, (2)
   8  * distributions including binary code include the above copyright notice and
   9  * this paragraph in its entirety in the documentation or other materials
  10  * provided with the distribution, and (3) all advertising materials mentioning
  11  * features or use of this software display the following acknowledgement:
  12  * ``This product includes software developed by the University of California,
  13  * Lawrence Berkeley Laboratory and its contributors.'' Neither the name of
  14  * the University nor the names of its contributors may be used to endorse
  15  * or promote products derived from this software without specific prior
  16  * written permission.
  17  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
  18  * WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
  19  * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
  20  */
  21
  22 #ifndef lint
  23 static const char rcsid[] _U_ =
  24     "@(#) $Header: /tcpdump/master/tcpdump/print-tcp.c,v 1.117 2004-07-15 00:13:01 guy Exp $ (LBL)";
  25 #endif
  26
  27 #ifdef HAVE_CONFIG_H
  28 #include "config.h"
  29 #endif
  30
  31 #include <tcpdump-stdinc.h>
  32
  33 #include <rpc/rpc.h>
  34
  35 #include <stdio.h>
  36 #include <stdlib.h>
  37 #include <string.h>
  38
  39 #include "interface.h"
  40 #include "addrtoname.h"
  41 #include "extract.h"
  42
  43 #include "tcp.h"
  44
  45 #include "ip.h"
  46 #ifdef INET6
  47 #include "ip6.h"
  48 #endif
  49 #include "ipproto.h"
  50
  51 #include "nameser.h"
  52
  53 #ifdef HAVE_LIBCRYPTO
  54 #include <openssl/md5.h>
  55
  56 static int tcp_verify_signature(const struct ip *ip, const struct tcphdr *tp,
  57     const u_char *data, int length, const u_char *rcvsig);
  58 #endif
  59
  60 static void print_tcp_rst_data(register const u_char *sp, u_int length);
  61
  62 #define MAX_RST_DATA_LEN        30
  63
  64
  65 struct tha {
  66 #ifndef INET6
  67         struct in_addr src;
  68         struct in_addr dst;
  69 #else
  70         struct in6_addr src;
  71         struct in6_addr dst;
  72 #endif /*INET6*/
  73         u_int port;
  74 };
  75
  76 struct tcp_seq_hash {
  77         struct tcp_seq_hash *nxt;
  78         struct tha addr;
  79         tcp_seq seq;
  80         tcp_seq ack;
  81 };
  82
  83 #define TSEQ_HASHSIZE 919
  84
  85 /* These tcp optinos do not have the size octet */
  86 #define ZEROLENOPT(o) ((o) == TCPOPT_EOL || (o) == TCPOPT_NOP)
  87
  88 static struct tcp_seq_hash tcp_seq_hash[TSEQ_HASHSIZE];
  89
  90
  91 #ifndef TELNET_PORT
  92 #define TELNET_PORT     23
  93 #endif
  94 #ifndef BGP_PORT
  95 #define BGP_PORT        179
  96 #endif
  97 #define NETBIOS_SSN_PORT 139
  98 #ifndef PPTP_PORT
  99 #define PPTP_PORT       1723
 100 #endif
 101 #define BEEP_PORT        10288
 102 #ifndef NFS_PORT
 103 #define NFS_PORT        2049
 104 #endif
 105 #define MSDP_PORT       639
 106 #define LDP_PORT        646
 107
 108 static int tcp_cksum(register const struct ip *ip,
 109                      register const struct tcphdr *tp,
 110                      register u_int len)
 111 {
 112         union phu {
 113                 struct phdr {
 114                         u_int32_t src;
 115                         u_int32_t dst;
 116                         u_char mbz;
 117                         u_char proto;
 118                         u_int16_t len;
 119                 } ph;
 120                 u_int16_t pa[6];
 121         } phu;
 122         const u_int16_t *sp;
 123
 124         /* pseudo-header.. */
 125         phu.ph.len = htons((u_int16_t)len);
 126         phu.ph.mbz = 0;
 127         phu.ph.proto = IPPROTO_TCP;
 128         memcpy(&phu.ph.src, &ip->ip_src.s_addr, sizeof(u_int32_t));
 129         if (IP_HL(ip) == 5)
 130                 memcpy(&phu.ph.dst, &ip->ip_dst.s_addr, sizeof(u_int32_t));
 131         else
 132                 phu.ph.dst = ip_finddst(ip);
 133
 134         sp = &phu.pa[0];
 135         return in_cksum((u_short *)tp, len,
 136                         sp[0]+sp[1]+sp[2]+sp[3]+sp[4]+sp[5]);
 137 }
 138
 139 #ifdef INET6
 140 static int tcp6_cksum(const struct ip6_hdr *ip6, const struct tcphdr *tp,
 141         u_int len)
 142 {
 143         size_t i;
 144         register const u_int16_t *sp;
 145         u_int32_t sum;
 146         union {
 147                 struct {
 148                         struct in6_addr ph_src;
 149                         struct in6_addr ph_dst;
 150                         u_int32_t       ph_len;
 151                         u_int8_t        ph_zero[3];
 152                         u_int8_t        ph_nxt;
 153                 } ph;
 154                 u_int16_t pa[20];
 155         } phu;
 156
 157         /* pseudo-header */
 158         memset(&phu, 0, sizeof(phu));
 159         phu.ph.ph_src = ip6->ip6_src;
 160         phu.ph.ph_dst = ip6->ip6_dst;
 161         phu.ph.ph_len = htonl(len);
 162         phu.ph.ph_nxt = IPPROTO_TCP;
 163
 164         sum = 0;
 165         for (i = 0; i < sizeof(phu.pa) / sizeof(phu.pa[0]); i++)
 166                 sum += phu.pa[i];
 167
 168         sp = (const u_int16_t *)tp;
 169
 170         for (i = 0; i < (len & ~1); i += 2)
 171                 sum += *sp++;
 172
 173         if (len & 1)
 174                 sum += htons((*(const u_int8_t *)sp) << 8);
 175
 176         while (sum > 0xffff)
 177                 sum = (sum & 0xffff) + (sum >> 16);
 178         sum = ~sum & 0xffff;
 179
 180         return (sum);
 181 }
 182 #endif
 183
 184 void
 185 tcp_print(register const u_char *bp, register u_int length,
 186           register const u_char *bp2, int fragmented)
 187 {
 188         register const struct tcphdr *tp;
 189         register const struct ip *ip;
 190         register u_char flags;
 191         register u_int hlen;
 192         register char ch;
 193         u_int16_t sport, dport, win, urp;
 194         u_int32_t seq, ack, thseq, thack;
 195         int threv;
 196 #ifdef INET6
 197         register const struct ip6_hdr *ip6;
 198 #endif
 199
 200         tp = (struct tcphdr *)bp;
 201         ip = (struct ip *)bp2;
 202 #ifdef INET6
 203         if (IP_V(ip) == 6)
 204                 ip6 = (struct ip6_hdr *)bp2;
 205         else
 206                 ip6 = NULL;
 207 #endif /*INET6*/
 208         ch = '\0';
 209         if (!TTEST(tp->th_dport)) {
 210                 (void)printf("%s > %s: [|tcp]",
 211                         ipaddr_string(&ip->ip_src),
 212                         ipaddr_string(&ip->ip_dst));
 213                 return;
 214         }
 215
 216         sport = EXTRACT_16BITS(&tp->th_sport);
 217         dport = EXTRACT_16BITS(&tp->th_dport);
 218
 219         hlen = TH_OFF(tp) * 4;
 220
 221         /*
 222          * If data present, header length valid, and NFS port used,
 223          * assume NFS.
 224          * Pass offset of data plus 4 bytes for RPC TCP msg length
 225          * to NFS print routines.
 226          */
 227         if (!qflag && hlen >= sizeof(*tp) && hlen <= length) {
 228                 if ((u_char *)tp + 4 + sizeof(struct rpc_msg) <= snapend &&
 229                     dport == NFS_PORT) {
 230                         nfsreq_print((u_char *)tp + hlen + 4, length - hlen,
 231                                      (u_char *)ip);
 232                         return;
 233                 } else if ((u_char *)tp + 4 + sizeof(struct rpc_msg)
 234                            <= snapend &&
 235                            sport == NFS_PORT) {
 236                         nfsreply_print((u_char *)tp + hlen + 4, length - hlen,
 237                                        (u_char *)ip);
 238                         return;
 239                 }
 240         }
 241 #ifdef INET6
 242         if (ip6) {
 243                 if (ip6->ip6_nxt == IPPROTO_TCP) {
 244                         (void)printf("%s.%s > %s.%s: ",
 245                                 ip6addr_string(&ip6->ip6_src),
 246                                 tcpport_string(sport),
 247                                 ip6addr_string(&ip6->ip6_dst),
 248                                 tcpport_string(dport));
 249                 } else {
 250                         (void)printf("%s > %s: ",
 251                                 tcpport_string(sport), tcpport_string(dport));
 252                 }
 253         } else
 254 #endif /*INET6*/
 255         {
 256                 if (ip->ip_p == IPPROTO_TCP) {
 257                         (void)printf("%s.%s > %s.%s: ",
 258                                 ipaddr_string(&ip->ip_src),
 259                                 tcpport_string(sport),
 260                                 ipaddr_string(&ip->ip_dst),
 261                                 tcpport_string(dport));
 262                 } else {
 263                         (void)printf("%s > %s: ",
 264                                 tcpport_string(sport), tcpport_string(dport));
 265                 }
 266         }
 267
 268         if (hlen < sizeof(*tp)) {
 269                 (void)printf(" tcp %d [bad hdr length %u - too short, < %lu]",
 270                     length - hlen, hlen, (unsigned long)sizeof(*tp));
 271                 return;
 272         }
 273
 274         TCHECK(*tp);
 275
 276         seq = EXTRACT_32BITS(&tp->th_seq);
 277         ack = EXTRACT_32BITS(&tp->th_ack);
 278         win = EXTRACT_16BITS(&tp->th_win);
 279         urp = EXTRACT_16BITS(&tp->th_urp);
 280
 281         if (qflag) {
 282                 (void)printf("tcp %d", length - hlen);
 283                 if (hlen > length) {
 284                         (void)printf(" [bad hdr length %u - too long, > %u]",
 285                             hlen, length);
 286                 }
 287                 return;
 288         }
 289         if ((flags = tp->th_flags) & (TH_SYN|TH_FIN|TH_RST|TH_PUSH|
 290                                       TH_ECNECHO|TH_CWR)) {
 291                 if (flags & TH_SYN)
 292                         putchar('S');
 293                 if (flags & TH_FIN)
 294                         putchar('F');
 295                 if (flags & TH_RST)
 296                         putchar('R');
 297                 if (flags & TH_PUSH)
 298                         putchar('P');
 299                 if (flags & TH_CWR)
 300                         putchar('W');   /* congestion _W_indow reduced (ECN) */
 301                 if (flags & TH_ECNECHO)
 302                         putchar('E');   /* ecn _E_cho sent (ECN) */
 303         } else
 304                 putchar('.');
 305
 306         if (!Sflag && (flags & TH_ACK)) {
 307                 register struct tcp_seq_hash *th;
 308                 const void *src, *dst;
 309                 register int rev;
 310                 struct tha tha;
 311                 /*
 312                  * Find (or record) the initial sequence numbers for
 313                  * this conversation.  (we pick an arbitrary
 314                  * collating order so there's only one entry for
 315                  * both directions).
 316                  */
 317 #ifdef INET6
 318                 memset(&tha, 0, sizeof(tha));
 319                 rev = 0;
 320                 if (ip6) {
 321                         src = &ip6->ip6_src;
 322                         dst = &ip6->ip6_dst;
 323                         if (sport > dport)
 324                                 rev = 1;
 325                         else if (sport == dport) {
 326                                 if (memcmp(src, dst, sizeof ip6->ip6_dst) > 0)
 327                                         rev = 1;
 328                         }
 329                         if (rev) {
 330                                 memcpy(&tha.src, dst, sizeof ip6->ip6_dst);
 331                                 memcpy(&tha.dst, src, sizeof ip6->ip6_src);
 332                                 tha.port = dport << 16 | sport;
 333                         } else {
 334                                 memcpy(&tha.dst, dst, sizeof ip6->ip6_dst);
 335                                 memcpy(&tha.src, src, sizeof ip6->ip6_src);
 336                                 tha.port = sport << 16 | dport;
 337                         }
 338                 } else {
 339                         src = &ip->ip_src;
 340                         dst = &ip->ip_dst;
 341                         if (sport > dport)
 342                                 rev = 1;
 343                         else if (sport == dport) {
 344                                 if (memcmp(src, dst, sizeof ip->ip_dst) > 0)
 345                                         rev = 1;
 346                         }
 347                         if (rev) {
 348                                 memcpy(&tha.src, dst, sizeof ip->ip_dst);
 349                                 memcpy(&tha.dst, src, sizeof ip->ip_src);
 350                                 tha.port = dport << 16 | sport;
 351                         } else {
 352                                 memcpy(&tha.dst, dst, sizeof ip->ip_dst);
 353                                 memcpy(&tha.src, src, sizeof ip->ip_src);
 354                                 tha.port = sport << 16 | dport;
 355                         }
 356                 }
 357 #else
 358                 rev = 0;
 359                 src = &ip->ip_src;
 360                 dst = &ip->ip_dst;
 361                 if (sport > dport)
 362                         rev = 1;
 363                 else if (sport == dport) {
 364                         if (memcmp(src, dst, sizeof ip->ip_dst) > 0)
 365                                 rev = 1;
 366                 }
 367                 if (rev) {
 368                         memcpy(&tha.src, dst, sizeof ip->ip_dst);
 369                         memcpy(&tha.dst, src, sizeof ip->ip_src);
 370                         tha.port = dport << 16 | sport;
 371                 } else {
 372                         memcpy(&tha.dst, dst, sizeof ip->ip_dst);
 373                         memcpy(&tha.src, src, sizeof ip->ip_src);
 374                         tha.port = sport << 16 | dport;
 375                 }
 376 #endif
 377
 378                 threv = rev;
 379                 for (th = &tcp_seq_hash[tha.port % TSEQ_HASHSIZE];
 380                      th->nxt; th = th->nxt)
 381                         if (memcmp((char *)&tha, (char *)&th->addr,
 382                                   sizeof(th->addr)) == 0)
 383                                 break;
 384
 385                 if (!th->nxt || (flags & TH_SYN)) {
 386                         /* didn't find it or new conversation */
 387                         if (th->nxt == NULL) {
 388                                 th->nxt = (struct tcp_seq_hash *)
 389                                         calloc(1, sizeof(*th));
 390                                 if (th->nxt == NULL)
 391                                         error("tcp_print: calloc");
 392                         }
 393                         th->addr = tha;
 394                         if (rev)
 395                                 th->ack = seq, th->seq = ack - 1;
 396                         else
 397                                 th->seq = seq, th->ack = ack - 1;
 398                 } else {
 399                         if (rev)
 400                                 seq -= th->ack, ack -= th->seq;
 401                         else
 402                                 seq -= th->seq, ack -= th->ack;
 403                 }
 404
 405                 thseq = th->seq;
 406                 thack = th->ack;
 407         } else {
 408                 /*fool gcc*/
 409                 thseq = thack = threv = 0;
 410         }
 411         if (hlen > length) {
 412                 (void)printf(" [bad hdr length %u - too long, > %u]",
 413                     hlen, length);
 414                 return;
 415         }
 416
 417         if (IP_V(ip) == 4 && vflag && !fragmented) {
 418                 u_int16_t sum, tcp_sum;
 419                 if (TTEST2(tp->th_sport, length)) {
 420                         sum = tcp_cksum(ip, tp, length);
 421
 422                         (void)printf(", cksum 0x%04x",EXTRACT_16BITS(&tp->th_sum));
 423                         if (sum != 0) {
 424                                 tcp_sum = EXTRACT_16BITS(&tp->th_sum);
 425                                 (void)printf(" (incorrect (-> 0x%04x),",in_cksum_shouldbe(tcp_sum, sum));
 426                         } else
 427                                 (void)printf(" (correct),");
 428                 }
 429         }
 430 #ifdef INET6
 431         if (IP_V(ip) == 6 && ip6->ip6_plen && vflag && !fragmented) {
 432                 u_int16_t sum,tcp_sum;
 433                 if (TTEST2(tp->th_sport, length)) {
 434                         sum = tcp6_cksum(ip6, tp, length);
 435                         (void)printf(", cksum 0x%04x",EXTRACT_16BITS(&tp->th_sum));
 436                         if (sum != 0) {
 437                                 tcp_sum = EXTRACT_16BITS(&tp->th_sum);
 438                                 (void)printf(" (incorrect (-> 0x%04x),",in_cksum_shouldbe(tcp_sum, sum));
 439                         } else
 440                                 (void)printf(" (correct),");
 441
 442                 }
 443         }
 444 #endif
 445
 446         length -= hlen;
 447         if (vflag > 1 || length > 0 || flags & (TH_SYN | TH_FIN | TH_RST))
 448                 (void)printf(" %u:%u(%u)", seq, seq + length, length);
 449         if (flags & TH_ACK)
 450                 (void)printf(" ack %u", ack);
 451
 452         (void)printf(" win %d", win);
 453
 454         if (flags & TH_URG)
 455                 (void)printf(" urg %d", urp);
 456         /*
 457          * Handle any options.
 458          */
 459         if (hlen > sizeof(*tp)) {
 460                 register const u_char *cp;
 461                 register u_int i, opt, datalen;
 462                 register u_int len;
 463
 464                 hlen -= sizeof(*tp);
 465                 cp = (const u_char *)tp + sizeof(*tp);
 466                 putchar(' ');
 467                 ch = '<';
 468                 while (hlen > 0) {
 469                         putchar(ch);
 470                         TCHECK(*cp);
 471                         opt = *cp++;
 472                         if (ZEROLENOPT(opt))
 473                                 len = 1;
 474                         else {
 475                                 TCHECK(*cp);
 476                                 len = *cp++;    /* total including type, len */
 477                                 if (len < 2 || len > hlen)
 478                                         goto bad;
 479                                 --hlen;         /* account for length byte */
 480                         }
 481                         --hlen;                 /* account for type byte */
 482                         datalen = 0;
 483
 484 /* Bail if "l" bytes of data are not left or were not captured  */
 485 #define LENCHECK(l) { if ((l) > hlen) goto bad; TCHECK2(*cp, l); }
 486
 487                         switch (opt) {
 488
 489                         case TCPOPT_MAXSEG:
 490                                 (void)printf("mss");
 491                                 datalen = 2;
 492                                 LENCHECK(datalen);
 493                                 (void)printf(" %u", EXTRACT_16BITS(cp));
 494
 495                                 break;
 496
 497                         case TCPOPT_EOL:
 498                                 (void)printf("eol");
 499                                 break;
 500
 501                         case TCPOPT_NOP:
 502                                 (void)printf("nop");
 503                                 break;
 504
 505                         case TCPOPT_WSCALE:
 506                                 (void)printf("wscale");
 507                                 datalen = 1;
 508                                 LENCHECK(datalen);
 509                                 (void)printf(" %u", *cp);
 510                                 break;
 511
 512                         case TCPOPT_SACKOK:
 513                                 (void)printf("sackOK");
 514                                 break;
 515
 516                         case TCPOPT_SACK:
 517                                 (void)printf("sack");
 518                                 datalen = len - 2;
 519                                 if (datalen % 8 != 0) {
 520                                         (void)printf(" malformed sack ");
 521                                 } else {
 522                                         u_int32_t s, e;
 523
 524                                         (void)printf(" sack %d ", datalen / 8);
 525                                         for (i = 0; i < datalen; i += 8) {
 526                                                 LENCHECK(i + 4);
 527                                                 s = EXTRACT_32BITS(cp + i);
 528                                                 LENCHECK(i + 8);
 529                                                 e = EXTRACT_32BITS(cp + i + 4);
 530                                                 if (threv) {
 531                                                         s -= thseq;
 532                                                         e -= thseq;
 533                                                 } else {
 534                                                         s -= thack;
 535                                                         e -= thack;
 536                                                 }
 537                                                 (void)printf("{%u:%u}", s, e);
 538                                         }
 539                                         (void)printf(" ");
 540                                 }
 541                                 break;
 542
 543                         case TCPOPT_ECHO:
 544                                 (void)printf("echo");
 545                                 datalen = 4;
 546                                 LENCHECK(datalen);
 547                                 (void)printf(" %u", EXTRACT_32BITS(cp));
 548                                 break;
 549
 550                         case TCPOPT_ECHOREPLY:
 551                                 (void)printf("echoreply");
 552                                 datalen = 4;
 553                                 LENCHECK(datalen);
 554                                 (void)printf(" %u", EXTRACT_32BITS(cp));
 555                                 break;
 556
 557                         case TCPOPT_TIMESTAMP:
 558                                 (void)printf("timestamp");
 559                                 datalen = 8;
 560                                 LENCHECK(4);
 561                                 (void)printf(" %u", EXTRACT_32BITS(cp));
 562                                 LENCHECK(datalen);
 563                                 (void)printf(" %u", EXTRACT_32BITS(cp + 4));
 564                                 break;
 565
 566                         case TCPOPT_CC:
 567                                 (void)printf("cc");
 568                                 datalen = 4;
 569                                 LENCHECK(datalen);
 570                                 (void)printf(" %u", EXTRACT_32BITS(cp));
 571                                 break;
 572
 573                         case TCPOPT_CCNEW:
 574                                 (void)printf("ccnew");
 575                                 datalen = 4;
 576                                 LENCHECK(datalen);
 577                                 (void)printf(" %u", EXTRACT_32BITS(cp));
 578                                 break;
 579
 580                         case TCPOPT_CCECHO:
 581                                 (void)printf("ccecho");
 582                                 datalen = 4;
 583                                 LENCHECK(datalen);
 584                                 (void)printf(" %u", EXTRACT_32BITS(cp));
 585                                 break;
 586
 587                         case TCPOPT_SIGNATURE:
 588                                 (void)printf("md5:");
 589                                 datalen = TCP_SIGLEN;
 590                                 LENCHECK(datalen);
 591 #ifdef HAVE_LIBCRYPTO
 592                                 if (tcp_verify_signature(ip, tp,
 593                                     bp + TH_OFF(tp) * 4, length, cp) == 0)
 594                                         (void)printf("valid");
 595                                 else
 596                                         (void)printf("invalid");
 597 #else
 598                                 for (i = 0; i < TCP_SIGLEN; ++i)
 599                                         (void)printf("%02x", cp[i]);
 600 #endif
 601                                 break;
 602
 603                         default:
 604                                 (void)printf("opt-%u:", opt);
 605                                 datalen = len - 2;
 606                                 for (i = 0; i < datalen; ++i) {
 607                                         LENCHECK(i);
 608                                         (void)printf("%02x", cp[i]);
 609                                 }
 610                                 break;
 611                         }
 612
 613                         /* Account for data printed */
 614                         cp += datalen;
 615                         hlen -= datalen;
 616
 617                         /* Check specification against observed length */
 618                         ++datalen;                      /* option octet */
 619                         if (!ZEROLENOPT(opt))
 620                                 ++datalen;              /* size octet */
 621                         if (datalen != len)
 622                                 (void)printf("[len %d]", len);
 623                         ch = ',';
 624                         if (opt == TCPOPT_EOL)
 625                                 break;
 626                 }
 627                 putchar('>');
 628         }
 629
 630         if (length <= 0)
 631                 return;
 632
 633         /*
 634          * Decode payload if necessary.
 635          */
 636         bp += TH_OFF(tp) * 4;
 637         if (flags & TH_RST) {
 638                 if (vflag)
 639                         print_tcp_rst_data(bp, length);
 640         } else {
 641                 if (sport == TELNET_PORT || dport == TELNET_PORT) {
 642                         if (!qflag && vflag)
 643                                 telnet_print(bp, length);
 644                 } else if (sport == BGP_PORT || dport == BGP_PORT)
 645                         bgp_print(bp, length);
 646                 else if (sport == PPTP_PORT || dport == PPTP_PORT)
 647                         pptp_print(bp);
 648 #ifdef TCPDUMP_DO_SMB
 649                 else if (sport == NETBIOS_SSN_PORT || dport == NETBIOS_SSN_PORT)
 650                         nbt_tcp_print(bp, length);
 651 #endif
 652                 else if (sport == BEEP_PORT || dport == BEEP_PORT)
 653                         beep_print(bp, length);
 654                 else if (length > 2 &&
 655                     (sport == NAMESERVER_PORT || dport == NAMESERVER_PORT ||
 656                      sport == MULTICASTDNS_PORT || dport == MULTICASTDNS_PORT)) {
 657                         /*
 658                          * TCP DNS query has 2byte length at the head.
 659                          * XXX packet could be unaligned, it can go strange
 660                          */
 661                         ns_print(bp + 2, length - 2, 0);
 662                 } else if (sport == MSDP_PORT || dport == MSDP_PORT) {
 663                         msdp_print(bp, length);
 664                 }
 665                 else if (length > 0 && (sport == LDP_PORT || dport == LDP_PORT)) {
 666                         ldp_print(bp, length);
 667                 }
 668         }
 669         return;
 670 bad:
 671         fputs("[bad opt]", stdout);
 672         if (ch != '\0')
 673                 putchar('>');
 674         return;
 675 trunc:
 676         fputs("[|tcp]", stdout);
 677         if (ch != '\0')
 678                 putchar('>');
 679 }
 680
 681 /*
 682  * RFC1122 says the following on data in RST segments:
 683  *
 684  *         4.2.2.12  RST Segment: RFC-793 Section 3.4
 685  *
 686  *            A TCP SHOULD allow a received RST segment to include data.
 687  *
 688  *            DISCUSSION
 689  *                 It has been suggested that a RST segment could contain
 690  *                 ASCII text that encoded and explained the cause of the
 691  *                 RST.  No standard has yet been established for such
 692  *                 data.
 693  *
 694  */
 695
 696 static void
 697 print_tcp_rst_data(register const u_char *sp, u_int length)
 698 {
 699         int c;
 700
 701         if (TTEST2(*sp, length))
 702                 printf(" [RST");
 703         else
 704                 printf(" [!RST");
 705         if (length > MAX_RST_DATA_LEN) {
 706                 length = MAX_RST_DATA_LEN;      /* can use -X for longer */
 707                 putchar('+');                   /* indicate we truncate */
 708         }
 709         putchar(' ');
 710         while (length-- && sp <= snapend) {
 711                 c = *sp++;
 712                 safeputchar(c);
 713         }
 714         putchar(']');
 715 }
 716
 717 #ifdef HAVE_LIBCRYPTO
 718 static int
 719 tcp_verify_signature(const struct ip *ip, const struct tcphdr *tp,
 720     const u_char *data, int length, const u_char *rcvsig)
 721 {
 722         struct tcphdr tp1;
 723         char sig[TCP_SIGLEN];
 724         char zero_proto = 0;
 725         MD5_CTX ctx;
 726         u_int16_t savecsum, tlen;
 727         struct ip6_hdr *ip6;
 728         u_int32_t len32;
 729         u_int8_t nxt;
 730
 731         tp1 = *tp;
 732
 733         if (tcpmd5secret == NULL)
 734                 return (-1);
 735
 736         MD5_Init(&ctx);
 737         /*
 738          * Step 1: Update MD5 hash with IP pseudo-header.
 739          */
 740         if (IP_V(ip) == 4) {
 741                 MD5_Update(&ctx, (char *)&ip->ip_src, sizeof(ip->ip_src));
 742                 MD5_Update(&ctx, (char *)&ip->ip_dst, sizeof(ip->ip_dst));
 743                 MD5_Update(&ctx, (char *)&zero_proto, sizeof(zero_proto));
 744                 MD5_Update(&ctx, (char *)&ip->ip_p, sizeof(ip->ip_p));
 745                 tlen = EXTRACT_16BITS(&ip->ip_len) - IP_HL(ip) * 4;
 746                 tlen = htons(tlen);
 747                 MD5_Update(&ctx, (char *)&tlen, sizeof(tlen));
 748         } else if (IP_V(ip) == 6) {
 749                 ip6 = (struct ip6_hdr *)ip;
 750                 MD5_Update(&ctx, (char *)&ip6->ip6_src, sizeof(ip6->ip6_src));
 751                 MD5_Update(&ctx, (char *)&ip6->ip6_dst, sizeof(ip6->ip6_dst));
 752                 len32 = htonl(ntohs(ip6->ip6_plen));
 753                 MD5_Update(&ctx, (char *)&len32, sizeof(len32));
 754                 nxt = 0;
 755                 MD5_Update(&ctx, (char *)&nxt, sizeof(nxt));
 756                 MD5_Update(&ctx, (char *)&nxt, sizeof(nxt));
 757                 MD5_Update(&ctx, (char *)&nxt, sizeof(nxt));
 758                 nxt = IPPROTO_TCP;
 759                 MD5_Update(&ctx, (char *)&nxt, sizeof(nxt));
 760         } else
 761                 return (-1);
 762
 763         /*
 764          * Step 2: Update MD5 hash with TCP header, excluding options.
 765          * The TCP checksum must be set to zero.
 766          */
 767         savecsum = tp1.th_sum;
 768         tp1.th_sum = 0;
 769         MD5_Update(&ctx, (char *)&tp1, sizeof(struct tcphdr));
 770         tp1.th_sum = savecsum;
 771         /*
 772          * Step 3: Update MD5 hash with TCP segment data, if present.
 773          */
 774         if (length > 0)
 775                 MD5_Update(&ctx, data, length);
 776         /*
 777          * Step 4: Update MD5 hash with shared secret.
 778          */
 779         MD5_Update(&ctx, tcpmd5secret, strlen(tcpmd5secret));
 780         MD5_Final(sig, &ctx);
 781
 782         return (memcmp(rcvsig, sig, 16));
 783 }
 784 #endif /* HAVE_LIBCRYPTO */