contrib/tcpdump-3.9/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  * Copyright (c) 1999-2004 The tcpdump.org project
   6  *
   7  * Redistribution and use in source and binary forms, with or without
   8  * modification, are permitted provided that: (1) source code distributions
   9  * retain the above copyright notice and this paragraph in its entirety, (2)
  10  * distributions including binary code include the above copyright notice and
  11  * this paragraph in its entirety in the documentation or other materials
  12  * provided with the distribution, and (3) all advertising materials mentioning
  13  * features or use of this software display the following acknowledgement:
  14  * ``This product includes software developed by the University of California,
  15  * Lawrence Berkeley Laboratory and its contributors.'' Neither the name of
  16  * the University nor the names of its contributors may be used to endorse
  17  * or promote products derived from this software without specific prior
  18  * written permission.
  19  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
  20  * WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
  21  * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
  22  */
  23
  24 #ifndef lint
  25 static const char rcsid[] _U_ =
  26     "@(#) $Header: /tcpdump/master/tcpdump/print-tcp.c,v 1.120.2.3 2005/10/16 06:05:46 guy Exp $ (LBL)";
  27 #endif
  28
  29 #ifdef HAVE_CONFIG_H
  30 #include "config.h"
  31 #endif
  32
  33 #include <tcpdump-stdinc.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 #include "rpc_auth.h"
  51 #include "rpc_msg.h"
  52
  53 #include "nameser.h"
  54
  55 #ifdef HAVE_LIBCRYPTO
  56 #include <openssl/md5.h>
  57
  58 #define SIGNATURE_VALID         0
  59 #define SIGNATURE_INVALID       1
  60 #define CANT_CHECK_SIGNATURE    2
  61
  62 static int tcp_verify_signature(const struct ip *ip, const struct tcphdr *tp,
  63     const u_char *data, int length, const u_char *rcvsig);
  64 #endif
  65
  66 static void print_tcp_rst_data(register const u_char *sp, u_int length);
  67
  68 #define MAX_RST_DATA_LEN        30
  69
  70
  71 struct tha {
  72 #ifndef INET6
  73         struct in_addr src;
  74         struct in_addr dst;
  75 #else
  76         struct in6_addr src;
  77         struct in6_addr dst;
  78 #endif /*INET6*/
  79         u_int port;
  80 };
  81
  82 struct tcp_seq_hash {
  83         struct tcp_seq_hash *nxt;
  84         struct tha addr;
  85         tcp_seq seq;
  86         tcp_seq ack;
  87 };
  88
  89 #define TSEQ_HASHSIZE 919
  90
  91 /* These tcp optinos do not have the size octet */
  92 #define ZEROLENOPT(o) ((o) == TCPOPT_EOL || (o) == TCPOPT_NOP)
  93
  94 static struct tcp_seq_hash tcp_seq_hash[TSEQ_HASHSIZE];
  95
  96
  97 #ifndef TELNET_PORT
  98 #define TELNET_PORT     23
  99 #endif
 100 #ifndef BGP_PORT
 101 #define BGP_PORT        179
 102 #endif
 103 #define NETBIOS_SSN_PORT 139
 104 #ifndef PPTP_PORT
 105 #define PPTP_PORT       1723
 106 #endif
 107 #define BEEP_PORT        10288
 108 #ifndef NFS_PORT
 109 #define NFS_PORT        2049
 110 #endif
 111 #define MSDP_PORT       639
 112 #define LDP_PORT        646
 113
 114 static int tcp_cksum(register const struct ip *ip,
 115                      register const struct tcphdr *tp,
 116                      register u_int len)
 117 {
 118         union phu {
 119                 struct phdr {
 120                         u_int32_t src;
 121                         u_int32_t dst;
 122                         u_char mbz;
 123                         u_char proto;
 124                         u_int16_t len;
 125                 } ph;
 126                 u_int16_t pa[6];
 127         } phu;
 128         const u_int16_t *sp;
 129
 130         /* pseudo-header.. */
 131         phu.ph.len = htons((u_int16_t)len);
 132         phu.ph.mbz = 0;
 133         phu.ph.proto = IPPROTO_TCP;
 134         memcpy(&phu.ph.src, &ip->ip_src.s_addr, sizeof(u_int32_t));
 135         if (IP_HL(ip) == 5)
 136                 memcpy(&phu.ph.dst, &ip->ip_dst.s_addr, sizeof(u_int32_t));
 137         else
 138                 phu.ph.dst = ip_finddst(ip);
 139
 140         sp = &phu.pa[0];
 141         return in_cksum((u_short *)tp, len,
 142                         sp[0]+sp[1]+sp[2]+sp[3]+sp[4]+sp[5]);
 143 }
 144
 145 #ifdef INET6
 146 static int tcp6_cksum(const struct ip6_hdr *ip6, const struct tcphdr *tp,
 147         u_int len)
 148 {
 149         size_t i;
 150         register const u_int16_t *sp;
 151         u_int32_t sum;
 152         union {
 153                 struct {
 154                         struct in6_addr ph_src;
 155                         struct in6_addr ph_dst;
 156                         u_int32_t       ph_len;
 157                         u_int8_t        ph_zero[3];
 158                         u_int8_t        ph_nxt;
 159                 } ph;
 160                 u_int16_t pa[20];
 161         } phu;
 162
 163         /* pseudo-header */
 164         memset(&phu, 0, sizeof(phu));
 165         phu.ph.ph_src = ip6->ip6_src;
 166         phu.ph.ph_dst = ip6->ip6_dst;
 167         phu.ph.ph_len = htonl(len);
 168         phu.ph.ph_nxt = IPPROTO_TCP;
 169
 170         sum = 0;
 171         for (i = 0; i < sizeof(phu.pa) / sizeof(phu.pa[0]); i++)
 172                 sum += phu.pa[i];
 173
 174         sp = (const u_int16_t *)tp;
 175
 176         for (i = 0; i < (len & ~1); i += 2)
 177                 sum += *sp++;
 178
 179         if (len & 1)
 180                 sum += htons((*(const u_int8_t *)sp) << 8);
 181
 182         while (sum > 0xffff)
 183                 sum = (sum & 0xffff) + (sum >> 16);
 184         sum = ~sum & 0xffff;
 185
 186         return (sum);
 187 }
 188 #endif
 189
 190 void
 191 tcp_print(register const u_char *bp, register u_int length,
 192           register const u_char *bp2, int fragmented)
 193 {
 194         register const struct tcphdr *tp;
 195         register const struct ip *ip;
 196         register u_char flags;
 197         register u_int hlen;
 198         register char ch;
 199         u_int16_t sport, dport, win, urp;
 200         u_int32_t seq, ack, thseq, thack;
 201         int threv;
 202 #ifdef INET6
 203         register const struct ip6_hdr *ip6;
 204 #endif
 205
 206         tp = (struct tcphdr *)bp;
 207         ip = (struct ip *)bp2;
 208 #ifdef INET6
 209         if (IP_V(ip) == 6)
 210                 ip6 = (struct ip6_hdr *)bp2;
 211         else
 212                 ip6 = NULL;
 213 #endif /*INET6*/
 214         ch = '\0';
 215         if (!TTEST(tp->th_dport)) {
 216                 (void)printf("%s > %s: [|tcp]",
 217                         ipaddr_string(&ip->ip_src),
 218                         ipaddr_string(&ip->ip_dst));
 219                 return;
 220         }
 221
 222         sport = EXTRACT_16BITS(&tp->th_sport);
 223         dport = EXTRACT_16BITS(&tp->th_dport);
 224
 225         hlen = TH_OFF(tp) * 4;
 226
 227         /*
 228          * If data present, header length valid, and NFS port used,
 229          * assume NFS.
 230          * Pass offset of data plus 4 bytes for RPC TCP msg length
 231          * to NFS print routines.
 232          */
 233         if (!qflag && hlen >= sizeof(*tp) && hlen <= length) {
 234                 if ((u_char *)tp + 4 + sizeof(struct sunrpc_msg) <= snapend &&
 235                     dport == NFS_PORT) {
 236                         nfsreq_print((u_char *)tp + hlen + 4, length - hlen,
 237                                      (u_char *)ip);
 238                         return;
 239                 } else if ((u_char *)tp + 4 + sizeof(struct sunrpc_msg)
 240                            <= snapend &&
 241                            sport == NFS_PORT) {
 242                         nfsreply_print((u_char *)tp + hlen + 4, length - hlen,
 243                                        (u_char *)ip);
 244                         return;
 245                 }
 246         }
 247 #ifdef INET6
 248         if (ip6) {
 249                 if (ip6->ip6_nxt == IPPROTO_TCP) {
 250                         (void)printf("%s.%s > %s.%s: ",
 251                                 ip6addr_string(&ip6->ip6_src),
 252                                 tcpport_string(sport),
 253                                 ip6addr_string(&ip6->ip6_dst),
 254                                 tcpport_string(dport));
 255                 } else {
 256                         (void)printf("%s > %s: ",
 257                                 tcpport_string(sport), tcpport_string(dport));
 258                 }
 259         } else
 260 #endif /*INET6*/
 261         {
 262                 if (ip->ip_p == IPPROTO_TCP) {
 263                         (void)printf("%s.%s > %s.%s: ",
 264                                 ipaddr_string(&ip->ip_src),
 265                                 tcpport_string(sport),
 266                                 ipaddr_string(&ip->ip_dst),
 267                                 tcpport_string(dport));
 268                 } else {
 269                         (void)printf("%s > %s: ",
 270                                 tcpport_string(sport), tcpport_string(dport));
 271                 }
 272         }
 273
 274         if (hlen < sizeof(*tp)) {
 275                 (void)printf(" tcp %d [bad hdr length %u - too short, < %lu]",
 276                     length - hlen, hlen, (unsigned long)sizeof(*tp));
 277                 return;
 278         }
 279
 280         TCHECK(*tp);
 281
 282         seq = EXTRACT_32BITS(&tp->th_seq);
 283         ack = EXTRACT_32BITS(&tp->th_ack);
 284         win = EXTRACT_16BITS(&tp->th_win);
 285         urp = EXTRACT_16BITS(&tp->th_urp);
 286
 287         if (qflag) {
 288                 (void)printf("tcp %d", length - hlen);
 289                 if (hlen > length) {
 290                         (void)printf(" [bad hdr length %u - too long, > %u]",
 291                             hlen, length);
 292                 }
 293                 return;
 294         }
 295         if ((flags = tp->th_flags) & (TH_SYN|TH_FIN|TH_RST|TH_PUSH|
 296                                       TH_ECNECHO|TH_CWR)) {
 297                 if (flags & TH_SYN)
 298                         putchar('S');
 299                 if (flags & TH_FIN)
 300                         putchar('F');
 301                 if (flags & TH_RST)
 302                         putchar('R');
 303                 if (flags & TH_PUSH)
 304                         putchar('P');
 305                 if (flags & TH_CWR)
 306                         putchar('W');   /* congestion _W_indow reduced (ECN) */
 307                 if (flags & TH_ECNECHO)
 308                         putchar('E');   /* ecn _E_cho sent (ECN) */
 309         } else
 310                 putchar('.');
 311
 312         if (!Sflag && (flags & TH_ACK)) {
 313                 register struct tcp_seq_hash *th;
 314                 const void *src, *dst;
 315                 register int rev;
 316                 struct tha tha;
 317                 /*
 318                  * Find (or record) the initial sequence numbers for
 319                  * this conversation.  (we pick an arbitrary
 320                  * collating order so there's only one entry for
 321                  * both directions).
 322                  */
 323 #ifdef INET6
 324                 memset(&tha, 0, sizeof(tha));
 325                 rev = 0;
 326                 if (ip6) {
 327                         src = &ip6->ip6_src;
 328                         dst = &ip6->ip6_dst;
 329                         if (sport > dport)
 330                                 rev = 1;
 331                         else if (sport == dport) {
 332                                 if (memcmp(src, dst, sizeof ip6->ip6_dst) > 0)
 333                                         rev = 1;
 334                         }
 335                         if (rev) {
 336                                 memcpy(&tha.src, dst, sizeof ip6->ip6_dst);
 337                                 memcpy(&tha.dst, src, sizeof ip6->ip6_src);
 338                                 tha.port = dport << 16 | sport;
 339                         } else {
 340                                 memcpy(&tha.dst, dst, sizeof ip6->ip6_dst);
 341                                 memcpy(&tha.src, src, sizeof ip6->ip6_src);
 342                                 tha.port = sport << 16 | dport;
 343                         }
 344                 } else {
 345                         src = &ip->ip_src;
 346                         dst = &ip->ip_dst;
 347                         if (sport > dport)
 348                                 rev = 1;
 349                         else if (sport == dport) {
 350                                 if (memcmp(src, dst, sizeof ip->ip_dst) > 0)
 351                                         rev = 1;
 352                         }
 353                         if (rev) {
 354                                 memcpy(&tha.src, dst, sizeof ip->ip_dst);
 355                                 memcpy(&tha.dst, src, sizeof ip->ip_src);
 356                                 tha.port = dport << 16 | sport;
 357                         } else {
 358                                 memcpy(&tha.dst, dst, sizeof ip->ip_dst);
 359                                 memcpy(&tha.src, src, sizeof ip->ip_src);
 360                                 tha.port = sport << 16 | dport;
 361                         }
 362                 }
 363 #else
 364                 rev = 0;
 365                 src = &ip->ip_src;
 366                 dst = &ip->ip_dst;
 367                 if (sport > dport)
 368                         rev = 1;
 369                 else if (sport == dport) {
 370                         if (memcmp(src, dst, sizeof ip->ip_dst) > 0)
 371                                 rev = 1;
 372                 }
 373                 if (rev) {
 374                         memcpy(&tha.src, dst, sizeof ip->ip_dst);
 375                         memcpy(&tha.dst, src, sizeof ip->ip_src);
 376                         tha.port = dport << 16 | sport;
 377                 } else {
 378                         memcpy(&tha.dst, dst, sizeof ip->ip_dst);
 379                         memcpy(&tha.src, src, sizeof ip->ip_src);
 380                         tha.port = sport << 16 | dport;
 381                 }
 382 #endif
 383
 384                 threv = rev;
 385                 for (th = &tcp_seq_hash[tha.port % TSEQ_HASHSIZE];
 386                      th->nxt; th = th->nxt)
 387                         if (memcmp((char *)&tha, (char *)&th->addr,
 388                                   sizeof(th->addr)) == 0)
 389                                 break;
 390
 391                 if (!th->nxt || (flags & TH_SYN)) {
 392                         /* didn't find it or new conversation */
 393                         if (th->nxt == NULL) {
 394                                 th->nxt = (struct tcp_seq_hash *)
 395                                         calloc(1, sizeof(*th));
 396                                 if (th->nxt == NULL)
 397                                         error("tcp_print: calloc");
 398                         }
 399                         th->addr = tha;
 400                         if (rev)
 401                                 th->ack = seq, th->seq = ack - 1;
 402                         else
 403                                 th->seq = seq, th->ack = ack - 1;
 404                 } else {
 405                         if (rev)
 406                                 seq -= th->ack, ack -= th->seq;
 407                         else
 408                                 seq -= th->seq, ack -= th->ack;
 409                 }
 410
 411                 thseq = th->seq;
 412                 thack = th->ack;
 413         } else {
 414                 /*fool gcc*/
 415                 thseq = thack = threv = 0;
 416         }
 417         if (hlen > length) {
 418                 (void)printf(" [bad hdr length %u - too long, > %u]",
 419                     hlen, length);
 420                 return;
 421         }
 422
 423         if (IP_V(ip) == 4 && vflag && !fragmented) {
 424                 u_int16_t sum, tcp_sum;
 425                 if (TTEST2(tp->th_sport, length)) {
 426                         sum = tcp_cksum(ip, tp, length);
 427
 428                         (void)printf(", cksum 0x%04x",EXTRACT_16BITS(&tp->th_sum));
 429                         if (sum != 0) {
 430                                 tcp_sum = EXTRACT_16BITS(&tp->th_sum);
 431                                 (void)printf(" (incorrect (-> 0x%04x),",in_cksum_shouldbe(tcp_sum, sum));
 432                         } else
 433                                 (void)printf(" (correct),");
 434                 }
 435         }
 436 #ifdef INET6
 437         if (IP_V(ip) == 6 && ip6->ip6_plen && vflag && !fragmented) {
 438                 u_int16_t sum,tcp_sum;
 439                 if (TTEST2(tp->th_sport, length)) {
 440                         sum = tcp6_cksum(ip6, tp, length);
 441                         (void)printf(", cksum 0x%04x",EXTRACT_16BITS(&tp->th_sum));
 442                         if (sum != 0) {
 443                                 tcp_sum = EXTRACT_16BITS(&tp->th_sum);
 444                                 (void)printf(" (incorrect (-> 0x%04x),",in_cksum_shouldbe(tcp_sum, sum));
 445                         } else
 446                                 (void)printf(" (correct),");
 447
 448                 }
 449         }
 450 #endif
 451
 452         length -= hlen;
 453         if (vflag > 1 || length > 0 || flags & (TH_SYN | TH_FIN | TH_RST))
 454                 (void)printf(" %u:%u(%u)", seq, seq + length, length);
 455         if (flags & TH_ACK)
 456                 (void)printf(" ack %u", ack);
 457
 458         (void)printf(" win %d", win);
 459
 460         if (flags & TH_URG)
 461                 (void)printf(" urg %d", urp);
 462         /*
 463          * Handle any options.
 464          */
 465         if (hlen > sizeof(*tp)) {
 466                 register const u_char *cp;
 467                 register u_int i, opt, datalen;
 468                 register u_int len;
 469
 470                 hlen -= sizeof(*tp);
 471                 cp = (const u_char *)tp + sizeof(*tp);
 472                 putchar(' ');
 473                 ch = '<';
 474                 while (hlen > 0) {
 475                         putchar(ch);
 476                         TCHECK(*cp);
 477                         opt = *cp++;
 478                         if (ZEROLENOPT(opt))
 479                                 len = 1;
 480                         else {
 481                                 TCHECK(*cp);
 482                                 len = *cp++;    /* total including type, len */
 483                                 if (len < 2 || len > hlen)
 484                                         goto bad;
 485                                 --hlen;         /* account for length byte */
 486                         }
 487                         --hlen;                 /* account for type byte */
 488                         datalen = 0;
 489
 490 /* Bail if "l" bytes of data are not left or were not captured  */
 491 #define LENCHECK(l) { if ((l) > hlen) goto bad; TCHECK2(*cp, l); }
 492
 493                         switch (opt) {
 494
 495                         case TCPOPT_MAXSEG:
 496                                 (void)printf("mss");
 497                                 datalen = 2;
 498                                 LENCHECK(datalen);
 499                                 (void)printf(" %u", EXTRACT_16BITS(cp));
 500
 501                                 break;
 502
 503                         case TCPOPT_EOL:
 504                                 (void)printf("eol");
 505                                 break;
 506
 507                         case TCPOPT_NOP:
 508                                 (void)printf("nop");
 509                                 break;
 510
 511                         case TCPOPT_WSCALE:
 512                                 (void)printf("wscale");
 513                                 datalen = 1;
 514                                 LENCHECK(datalen);
 515                                 (void)printf(" %u", *cp);
 516                                 break;
 517
 518                         case TCPOPT_SACKOK:
 519                                 (void)printf("sackOK");
 520                                 break;
 521
 522                         case TCPOPT_SACK:
 523                                 datalen = len - 2;
 524                                 if (datalen % 8 != 0) {
 525                                         (void)printf("malformed sack");
 526                                 } else {
 527                                         u_int32_t s, e;
 528
 529                                         (void)printf("sack %d ", datalen / 8);
 530                                         for (i = 0; i < datalen; i += 8) {
 531                                                 LENCHECK(i + 4);
 532                                                 s = EXTRACT_32BITS(cp + i);
 533                                                 LENCHECK(i + 8);
 534                                                 e = EXTRACT_32BITS(cp + i + 4);
 535                                                 if (threv) {
 536                                                         s -= thseq;
 537                                                         e -= thseq;
 538                                                 } else {
 539                                                         s -= thack;
 540                                                         e -= thack;
 541                                                 }
 542                                                 (void)printf("{%u:%u}", s, e);
 543                                         }
 544                                 }
 545                                 break;
 546
 547                         case TCPOPT_ECHO:
 548                                 (void)printf("echo");
 549                                 datalen = 4;
 550                                 LENCHECK(datalen);
 551                                 (void)printf(" %u", EXTRACT_32BITS(cp));
 552                                 break;
 553
 554                         case TCPOPT_ECHOREPLY:
 555                                 (void)printf("echoreply");
 556                                 datalen = 4;
 557                                 LENCHECK(datalen);
 558                                 (void)printf(" %u", EXTRACT_32BITS(cp));
 559                                 break;
 560
 561                         case TCPOPT_TIMESTAMP:
 562                                 (void)printf("timestamp");
 563                                 datalen = 8;
 564                                 LENCHECK(4);
 565                                 (void)printf(" %u", EXTRACT_32BITS(cp));
 566                                 LENCHECK(datalen);
 567                                 (void)printf(" %u", EXTRACT_32BITS(cp + 4));
 568                                 break;
 569
 570                         case TCPOPT_CC:
 571                                 (void)printf("cc");
 572                                 datalen = 4;
 573                                 LENCHECK(datalen);
 574                                 (void)printf(" %u", EXTRACT_32BITS(cp));
 575                                 break;
 576
 577                         case TCPOPT_CCNEW:
 578                                 (void)printf("ccnew");
 579                                 datalen = 4;
 580                                 LENCHECK(datalen);
 581                                 (void)printf(" %u", EXTRACT_32BITS(cp));
 582                                 break;
 583
 584                         case TCPOPT_CCECHO:
 585                                 (void)printf("ccecho");
 586                                 datalen = 4;
 587                                 LENCHECK(datalen);
 588                                 (void)printf(" %u", EXTRACT_32BITS(cp));
 589                                 break;
 590
 591                         case TCPOPT_SIGNATURE:
 592                                 (void)printf("md5:");
 593                                 datalen = TCP_SIGLEN;
 594                                 LENCHECK(datalen);
 595 #ifdef HAVE_LIBCRYPTO
 596                                 switch (tcp_verify_signature(ip, tp,
 597                                     bp + TH_OFF(tp) * 4, length, cp)) {
 598
 599                                 case SIGNATURE_VALID:
 600                                         (void)printf("valid");
 601                                         break;
 602
 603                                 case SIGNATURE_INVALID:
 604                                         (void)printf("invalid");
 605                                         break;
 606
 607                                 case CANT_CHECK_SIGNATURE:
 608                                         (void)printf("can't check - ");
 609                                         for (i = 0; i < TCP_SIGLEN; ++i)
 610                                                 (void)printf("%02x", cp[i]);
 611                                         break;
 612                                 }
 613 #else
 614                                 for (i = 0; i < TCP_SIGLEN; ++i)
 615                                         (void)printf("%02x", cp[i]);
 616 #endif
 617                                 break;
 618
 619                         default:
 620                                 (void)printf("opt-%u:", opt);
 621                                 datalen = len - 2;
 622                                 for (i = 0; i < datalen; ++i) {
 623                                         LENCHECK(i);
 624                                         (void)printf("%02x", cp[i]);
 625                                 }
 626                                 break;
 627                         }
 628
 629                         /* Account for data printed */
 630                         cp += datalen;
 631                         hlen -= datalen;
 632
 633                         /* Check specification against observed length */
 634                         ++datalen;                      /* option octet */
 635                         if (!ZEROLENOPT(opt))
 636                                 ++datalen;              /* size octet */
 637                         if (datalen != len)
 638                                 (void)printf("[len %d]", len);
 639                         ch = ',';
 640                         if (opt == TCPOPT_EOL)
 641                                 break;
 642                 }
 643                 putchar('>');
 644         }
 645
 646         if (length <= 0)
 647                 return;
 648
 649         /*
 650          * Decode payload if necessary.
 651          */
 652         bp += TH_OFF(tp) * 4;
 653         if (flags & TH_RST) {
 654                 if (vflag)
 655                         print_tcp_rst_data(bp, length);
 656         } else {
 657                 if (sport == TELNET_PORT || dport == TELNET_PORT) {
 658                         if (!qflag && vflag)
 659                                 telnet_print(bp, length);
 660                 } else if (sport == BGP_PORT || dport == BGP_PORT)
 661                         bgp_print(bp, length);
 662                 else if (sport == PPTP_PORT || dport == PPTP_PORT)
 663                         pptp_print(bp);
 664 #ifdef TCPDUMP_DO_SMB
 665                 else if (sport == NETBIOS_SSN_PORT || dport == NETBIOS_SSN_PORT)
 666                         nbt_tcp_print(bp, length);
 667 #endif
 668                 else if (sport == BEEP_PORT || dport == BEEP_PORT)
 669                         beep_print(bp, length);
 670                 else if (length > 2 &&
 671                     (sport == NAMESERVER_PORT || dport == NAMESERVER_PORT ||
 672                      sport == MULTICASTDNS_PORT || dport == MULTICASTDNS_PORT)) {
 673                         /*
 674                          * TCP DNS query has 2byte length at the head.
 675                          * XXX packet could be unaligned, it can go strange
 676                          */
 677                         ns_print(bp + 2, length - 2, 0);
 678                 } else if (sport == MSDP_PORT || dport == MSDP_PORT) {
 679                         msdp_print(bp, length);
 680                 }
 681                 else if (length > 0 && (sport == LDP_PORT || dport == LDP_PORT)) {
 682                         ldp_print(bp, length);
 683                 }
 684         }
 685         return;
 686 bad:
 687         fputs("[bad opt]", stdout);
 688         if (ch != '\0')
 689                 putchar('>');
 690         return;
 691 trunc:
 692         fputs("[|tcp]", stdout);
 693         if (ch != '\0')
 694                 putchar('>');
 695 }
 696
 697 /*
 698  * RFC1122 says the following on data in RST segments:
 699  *
 700  *         4.2.2.12  RST Segment: RFC-793 Section 3.4
 701  *
 702  *            A TCP SHOULD allow a received RST segment to include data.
 703  *
 704  *            DISCUSSION
 705  *                 It has been suggested that a RST segment could contain
 706  *                 ASCII text that encoded and explained the cause of the
 707  *                 RST.  No standard has yet been established for such
 708  *                 data.
 709  *
 710  */
 711
 712 static void
 713 print_tcp_rst_data(register const u_char *sp, u_int length)
 714 {
 715         int c;
 716
 717         if (TTEST2(*sp, length))
 718                 printf(" [RST");
 719         else
 720                 printf(" [!RST");
 721         if (length > MAX_RST_DATA_LEN) {
 722                 length = MAX_RST_DATA_LEN;      /* can use -X for longer */
 723                 putchar('+');                   /* indicate we truncate */
 724         }
 725         putchar(' ');
 726         while (length-- && sp <= snapend) {
 727                 c = *sp++;
 728                 safeputchar(c);
 729         }
 730         putchar(']');
 731 }
 732
 733 #ifdef HAVE_LIBCRYPTO
 734 static int
 735 tcp_verify_signature(const struct ip *ip, const struct tcphdr *tp,
 736     const u_char *data, int length, const u_char *rcvsig)
 737 {
 738         struct tcphdr tp1;
 739         u_char sig[TCP_SIGLEN];
 740         char zero_proto = 0;
 741         MD5_CTX ctx;
 742         u_int16_t savecsum, tlen;
 743 #ifdef INET6
 744         struct ip6_hdr *ip6;
 745 #endif
 746         u_int32_t len32;
 747         u_int8_t nxt;
 748
 749         tp1 = *tp;
 750
 751         if (tcpmd5secret == NULL)
 752                 return (CANT_CHECK_SIGNATURE);
 753
 754         MD5_Init(&ctx);
 755         /*
 756          * Step 1: Update MD5 hash with IP pseudo-header.
 757          */
 758         if (IP_V(ip) == 4) {
 759                 MD5_Update(&ctx, (char *)&ip->ip_src, sizeof(ip->ip_src));
 760                 MD5_Update(&ctx, (char *)&ip->ip_dst, sizeof(ip->ip_dst));
 761                 MD5_Update(&ctx, (char *)&zero_proto, sizeof(zero_proto));
 762                 MD5_Update(&ctx, (char *)&ip->ip_p, sizeof(ip->ip_p));
 763                 tlen = EXTRACT_16BITS(&ip->ip_len) - IP_HL(ip) * 4;
 764                 tlen = htons(tlen);
 765                 MD5_Update(&ctx, (char *)&tlen, sizeof(tlen));
 766 #ifdef INET6
 767         } else if (IP_V(ip) == 6) {
 768                 ip6 = (struct ip6_hdr *)ip;
 769                 MD5_Update(&ctx, (char *)&ip6->ip6_src, sizeof(ip6->ip6_src));
 770                 MD5_Update(&ctx, (char *)&ip6->ip6_dst, sizeof(ip6->ip6_dst));
 771                 len32 = htonl(ntohs(ip6->ip6_plen));
 772                 MD5_Update(&ctx, (char *)&len32, sizeof(len32));
 773                 nxt = 0;
 774                 MD5_Update(&ctx, (char *)&nxt, sizeof(nxt));
 775                 MD5_Update(&ctx, (char *)&nxt, sizeof(nxt));
 776                 MD5_Update(&ctx, (char *)&nxt, sizeof(nxt));
 777                 nxt = IPPROTO_TCP;
 778                 MD5_Update(&ctx, (char *)&nxt, sizeof(nxt));
 779 #endif
 780         } else
 781                 return (CANT_CHECK_SIGNATURE);
 782
 783         /*
 784          * Step 2: Update MD5 hash with TCP header, excluding options.
 785          * The TCP checksum must be set to zero.
 786          */
 787         savecsum = tp1.th_sum;
 788         tp1.th_sum = 0;
 789         MD5_Update(&ctx, (char *)&tp1, sizeof(struct tcphdr));
 790         tp1.th_sum = savecsum;
 791         /*
 792          * Step 3: Update MD5 hash with TCP segment data, if present.
 793          */
 794         if (length > 0)
 795                 MD5_Update(&ctx, data, length);
 796         /*
 797          * Step 4: Update MD5 hash with shared secret.
 798          */
 799         MD5_Update(&ctx, tcpmd5secret, strlen(tcpmd5secret));
 800         MD5_Final(sig, &ctx);
 801
 802         if (memcmp(rcvsig, sig, TCP_SIGLEN) == 0)
 803                 return (SIGNATURE_VALID);
 804         else
 805                 return (SIGNATURE_INVALID);
 806 }
 807 #endif /* HAVE_LIBCRYPTO */