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 1.111 2004-03-23 07:15:36 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, 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 and NFS port used, assume NFS.
 223          * Pass offset of data plus 4 bytes for RPC TCP msg length
 224          * to NFS print routines.
 225          */
 226         if (!qflag) {
 227                 if ((u_char *)tp + 4 + sizeof(struct rpc_msg) <= snapend &&
 228                     dport == NFS_PORT) {
 229                         nfsreq_print((u_char *)tp + hlen + 4, length - hlen,
 230                                      (u_char *)ip);
 231                         return;
 232                 } else if ((u_char *)tp + 4 + sizeof(struct rpc_msg)
 233                            <= snapend &&
 234                            sport == NFS_PORT) {
 235                         nfsreply_print((u_char *)tp + hlen + 4, length - hlen,
 236                                        (u_char *)ip);
 237                         return;
 238                 }
 239         }
 240 #ifdef INET6
 241         if (ip6) {
 242                 if (ip6->ip6_nxt == IPPROTO_TCP) {
 243                         (void)printf("%s.%s > %s.%s: ",
 244                                 ip6addr_string(&ip6->ip6_src),
 245                                 tcpport_string(sport),
 246                                 ip6addr_string(&ip6->ip6_dst),
 247                                 tcpport_string(dport));
 248                 } else {
 249                         (void)printf("%s > %s: ",
 250                                 tcpport_string(sport), tcpport_string(dport));
 251                 }
 252         } else
 253 #endif /*INET6*/
 254         {
 255                 if (ip->ip_p == IPPROTO_TCP) {
 256                         (void)printf("%s.%s > %s.%s: ",
 257                                 ipaddr_string(&ip->ip_src),
 258                                 tcpport_string(sport),
 259                                 ipaddr_string(&ip->ip_dst),
 260                                 tcpport_string(dport));
 261                 } else {
 262                         (void)printf("%s > %s: ",
 263                                 tcpport_string(sport), tcpport_string(dport));
 264                 }
 265         }
 266
 267         TCHECK(*tp);
 268
 269         seq = EXTRACT_32BITS(&tp->th_seq);
 270         ack = EXTRACT_32BITS(&tp->th_ack);
 271         win = EXTRACT_16BITS(&tp->th_win);
 272         urp = EXTRACT_16BITS(&tp->th_urp);
 273
 274         if (qflag) {
 275                 (void)printf("tcp %d", length - TH_OFF(tp) * 4);
 276                 return;
 277         }
 278         if ((flags = tp->th_flags) & (TH_SYN|TH_FIN|TH_RST|TH_PUSH|
 279                                       TH_ECNECHO|TH_CWR)) {
 280                 if (flags & TH_SYN)
 281                         putchar('S');
 282                 if (flags & TH_FIN)
 283                         putchar('F');
 284                 if (flags & TH_RST)
 285                         putchar('R');
 286                 if (flags & TH_PUSH)
 287                         putchar('P');
 288                 if (flags & TH_CWR)
 289                         putchar('W');   /* congestion _W_indow reduced (ECN) */
 290                 if (flags & TH_ECNECHO)
 291                         putchar('E');   /* ecn _E_cho sent (ECN) */
 292         } else
 293                 putchar('.');
 294
 295         if (!Sflag && (flags & TH_ACK)) {
 296                 register struct tcp_seq_hash *th;
 297                 const void *src, *dst;
 298                 register int rev;
 299                 struct tha tha;
 300                 /*
 301                  * Find (or record) the initial sequence numbers for
 302                  * this conversation.  (we pick an arbitrary
 303                  * collating order so there's only one entry for
 304                  * both directions).
 305                  */
 306 #ifdef INET6
 307                 memset(&tha, 0, sizeof(tha));
 308                 rev = 0;
 309                 if (ip6) {
 310                         src = &ip6->ip6_src;
 311                         dst = &ip6->ip6_dst;
 312                         if (sport > dport)
 313                                 rev = 1;
 314                         else if (sport == dport) {
 315                                 if (memcmp(src, dst, sizeof ip6->ip6_dst) > 0)
 316                                         rev = 1;
 317                         }
 318                         if (rev) {
 319                                 memcpy(&tha.src, dst, sizeof ip6->ip6_dst);
 320                                 memcpy(&tha.dst, src, sizeof ip6->ip6_src);
 321                                 tha.port = dport << 16 | sport;
 322                         } else {
 323                                 memcpy(&tha.dst, dst, sizeof ip6->ip6_dst);
 324                                 memcpy(&tha.src, src, sizeof ip6->ip6_src);
 325                                 tha.port = sport << 16 | dport;
 326                         }
 327                 } else {
 328                         src = &ip->ip_src;
 329                         dst = &ip->ip_dst;
 330                         if (sport > dport)
 331                                 rev = 1;
 332                         else if (sport == dport) {
 333                                 if (memcmp(src, dst, sizeof ip->ip_dst) > 0)
 334                                         rev = 1;
 335                         }
 336                         if (rev) {
 337                                 memcpy(&tha.src, dst, sizeof ip->ip_dst);
 338                                 memcpy(&tha.dst, src, sizeof ip->ip_src);
 339                                 tha.port = dport << 16 | sport;
 340                         } else {
 341                                 memcpy(&tha.dst, dst, sizeof ip->ip_dst);
 342                                 memcpy(&tha.src, src, sizeof ip->ip_src);
 343                                 tha.port = sport << 16 | dport;
 344                         }
 345                 }
 346 #else
 347                 rev = 0;
 348                 src = &ip->ip_src;
 349                 dst = &ip->ip_dst;
 350                 if (sport > dport)
 351                         rev = 1;
 352                 else if (sport == dport) {
 353                         if (memcmp(src, dst, sizeof ip->ip_dst) > 0)
 354                                 rev = 1;
 355                 }
 356                 if (rev) {
 357                         memcpy(&tha.src, dst, sizeof ip->ip_dst);
 358                         memcpy(&tha.dst, src, sizeof ip->ip_src);
 359                         tha.port = dport << 16 | sport;
 360                 } else {
 361                         memcpy(&tha.dst, dst, sizeof ip->ip_dst);
 362                         memcpy(&tha.src, src, sizeof ip->ip_src);
 363                         tha.port = sport << 16 | dport;
 364                 }
 365 #endif
 366
 367                 threv = rev;
 368                 for (th = &tcp_seq_hash[tha.port % TSEQ_HASHSIZE];
 369                      th->nxt; th = th->nxt)
 370                         if (memcmp((char *)&tha, (char *)&th->addr,
 371                                   sizeof(th->addr)) == 0)
 372                                 break;
 373
 374                 if (!th->nxt || (flags & TH_SYN)) {
 375                         /* didn't find it or new conversation */
 376                         if (th->nxt == NULL) {
 377                                 th->nxt = (struct tcp_seq_hash *)
 378                                         calloc(1, sizeof(*th));
 379                                 if (th->nxt == NULL)
 380                                         error("tcp_print: calloc");
 381                         }
 382                         th->addr = tha;
 383                         if (rev)
 384                                 th->ack = seq, th->seq = ack - 1;
 385                         else
 386                                 th->seq = seq, th->ack = ack - 1;
 387                 } else {
 388                         if (rev)
 389                                 seq -= th->ack, ack -= th->seq;
 390                         else
 391                                 seq -= th->seq, ack -= th->ack;
 392                 }
 393
 394                 thseq = th->seq;
 395                 thack = th->ack;
 396         } else {
 397                 /*fool gcc*/
 398                 thseq = thack = threv = 0;
 399         }
 400         if (hlen > length) {
 401                 (void)printf(" [bad hdr length]");
 402                 return;
 403         }
 404
 405         if (IP_V(ip) == 4 && vflag && !fragmented) {
 406                 u_int16_t sum, tcp_sum;
 407                 if (TTEST2(tp->th_sport, length)) {
 408                         sum = tcp_cksum(ip, tp, length);
 409                         if (sum != 0) {
 410                                 tcp_sum = EXTRACT_16BITS(&tp->th_sum);
 411                                 (void)printf(" [bad tcp cksum %x (->%x)!]",
 412                                     tcp_sum, in_cksum_shouldbe(tcp_sum, sum));
 413                         } else
 414                                 (void)printf(" [tcp sum ok]");
 415                 }
 416         }
 417 #ifdef INET6
 418         if (IP_V(ip) == 6 && ip6->ip6_plen && vflag && !fragmented) {
 419                 int sum;
 420                 if (TTEST2(tp->th_sport, length)) {
 421                         sum = tcp6_cksum(ip6, tp, length);
 422                         if (sum != 0)
 423                                 (void)printf(" [bad tcp cksum %x!]", sum);
 424                         else
 425                                 (void)printf(" [tcp sum ok]");
 426                 }
 427         }
 428 #endif
 429
 430         length -= hlen;
 431         if (vflag > 1 || length > 0 || flags & (TH_SYN | TH_FIN | TH_RST))
 432                 (void)printf(" %u:%u(%u)", seq, seq + length, length);
 433         if (flags & TH_ACK)
 434                 (void)printf(" ack %u", ack);
 435
 436         (void)printf(" win %d", win);
 437
 438         if (flags & TH_URG)
 439                 (void)printf(" urg %d", urp);
 440         /*
 441          * Handle any options.
 442          */
 443         if (hlen > sizeof(*tp)) {
 444                 register const u_char *cp;
 445                 register u_int i, opt, datalen;
 446                 register u_int len;
 447
 448                 hlen -= sizeof(*tp);
 449                 cp = (const u_char *)tp + sizeof(*tp);
 450                 putchar(' ');
 451                 ch = '<';
 452                 while (hlen > 0) {
 453                         putchar(ch);
 454                         TCHECK(*cp);
 455                         opt = *cp++;
 456                         if (ZEROLENOPT(opt))
 457                                 len = 1;
 458                         else {
 459                                 TCHECK(*cp);
 460                                 len = *cp++;    /* total including type, len */
 461                                 if (len < 2 || len > hlen)
 462                                         goto bad;
 463                                 --hlen;         /* account for length byte */
 464                         }
 465                         --hlen;                 /* account for type byte */
 466                         datalen = 0;
 467
 468 /* Bail if "l" bytes of data are not left or were not captured  */
 469 #define LENCHECK(l) { if ((l) > hlen) goto bad; TCHECK2(*cp, l); }
 470
 471                         switch (opt) {
 472
 473                         case TCPOPT_MAXSEG:
 474                                 (void)printf("mss");
 475                                 datalen = 2;
 476                                 LENCHECK(datalen);
 477                                 (void)printf(" %u", EXTRACT_16BITS(cp));
 478
 479                                 break;
 480
 481                         case TCPOPT_EOL:
 482                                 (void)printf("eol");
 483                                 break;
 484
 485                         case TCPOPT_NOP:
 486                                 (void)printf("nop");
 487                                 break;
 488
 489                         case TCPOPT_WSCALE:
 490                                 (void)printf("wscale");
 491                                 datalen = 1;
 492                                 LENCHECK(datalen);
 493                                 (void)printf(" %u", *cp);
 494                                 break;
 495
 496                         case TCPOPT_SACKOK:
 497                                 (void)printf("sackOK");
 498                                 break;
 499
 500                         case TCPOPT_SACK:
 501                                 (void)printf("sack");
 502                                 datalen = len - 2;
 503                                 if (datalen % 8 != 0) {
 504                                         (void)printf(" malformed sack ");
 505                                 } else {
 506                                         u_int32_t s, e;
 507
 508                                         (void)printf(" sack %d ", datalen / 8);
 509                                         for (i = 0; i < datalen; i += 8) {
 510                                                 LENCHECK(i + 4);
 511                                                 s = EXTRACT_32BITS(cp + i);
 512                                                 LENCHECK(i + 8);
 513                                                 e = EXTRACT_32BITS(cp + i + 4);
 514                                                 if (threv) {
 515                                                         s -= thseq;
 516                                                         e -= thseq;
 517                                                 } else {
 518                                                         s -= thack;
 519                                                         e -= thack;
 520                                                 }
 521                                                 (void)printf("{%u:%u}", s, e);
 522                                         }
 523                                         (void)printf(" ");
 524                                 }
 525                                 break;
 526
 527                         case TCPOPT_ECHO:
 528                                 (void)printf("echo");
 529                                 datalen = 4;
 530                                 LENCHECK(datalen);
 531                                 (void)printf(" %u", EXTRACT_32BITS(cp));
 532                                 break;
 533
 534                         case TCPOPT_ECHOREPLY:
 535                                 (void)printf("echoreply");
 536                                 datalen = 4;
 537                                 LENCHECK(datalen);
 538                                 (void)printf(" %u", EXTRACT_32BITS(cp));
 539                                 break;
 540
 541                         case TCPOPT_TIMESTAMP:
 542                                 (void)printf("timestamp");
 543                                 datalen = 8;
 544                                 LENCHECK(4);
 545                                 (void)printf(" %u", EXTRACT_32BITS(cp));
 546                                 LENCHECK(datalen);
 547                                 (void)printf(" %u", EXTRACT_32BITS(cp + 4));
 548                                 break;
 549
 550                         case TCPOPT_CC:
 551                                 (void)printf("cc");
 552                                 datalen = 4;
 553                                 LENCHECK(datalen);
 554                                 (void)printf(" %u", EXTRACT_32BITS(cp));
 555                                 break;
 556
 557                         case TCPOPT_CCNEW:
 558                                 (void)printf("ccnew");
 559                                 datalen = 4;
 560                                 LENCHECK(datalen);
 561                                 (void)printf(" %u", EXTRACT_32BITS(cp));
 562                                 break;
 563
 564                         case TCPOPT_CCECHO:
 565                                 (void)printf("ccecho");
 566                                 datalen = 4;
 567                                 LENCHECK(datalen);
 568                                 (void)printf(" %u", EXTRACT_32BITS(cp));
 569                                 break;
 570
 571                         case TCPOPT_SIGNATURE:
 572                                 (void)printf("md5:");
 573                                 if (IP_V(ip) != 4) {
 574                                         (void)printf("!ipv4");
 575                                         break;
 576                                 }
 577                                 datalen = TCP_SIGLEN;
 578                                 LENCHECK(datalen);
 579 #ifdef HAVE_LIBCRYPTO
 580                                 if (tcp_verify_signature(ip, tp,
 581                                     bp + TH_OFF(tp) * 4, length, cp) == 0)
 582                                         (void)printf("valid");
 583                                 else
 584                                         (void)printf("invalid");
 585 #else
 586                                 for (i = 0; i < TCP_SIGLEN; ++i)
 587                                         (void)printf("%02x", cp[i]);
 588 #endif
 589                                 break;
 590
 591                         default:
 592                                 (void)printf("opt-%u:", opt);
 593                                 datalen = len - 2;
 594                                 for (i = 0; i < datalen; ++i) {
 595                                         LENCHECK(i);
 596                                         (void)printf("%02x", cp[i]);
 597                                 }
 598                                 break;
 599                         }
 600
 601                         /* Account for data printed */
 602                         cp += datalen;
 603                         hlen -= datalen;
 604
 605                         /* Check specification against observed length */
 606                         ++datalen;                      /* option octet */
 607                         if (!ZEROLENOPT(opt))
 608                                 ++datalen;              /* size octet */
 609                         if (datalen != len)
 610                                 (void)printf("[len %d]", len);
 611                         ch = ',';
 612                         if (opt == TCPOPT_EOL)
 613                                 break;
 614                 }
 615                 putchar('>');
 616         }
 617
 618         if (length <= 0)
 619                 return;
 620
 621         /*
 622          * Decode payload if necessary.
 623          */
 624         bp += TH_OFF(tp) * 4;
 625         if (flags & TH_RST) {
 626                 if (vflag)
 627                         print_tcp_rst_data(bp, length);
 628         } else {
 629                 if (sport == TELNET_PORT || dport == TELNET_PORT) {
 630                         if (!qflag && vflag)
 631                                 telnet_print(bp, length);
 632                 } else if (sport == BGP_PORT || dport == BGP_PORT)
 633                         bgp_print(bp, length);
 634                 else if (sport == PPTP_PORT || dport == PPTP_PORT)
 635                         pptp_print(bp);
 636 #ifdef TCPDUMP_DO_SMB
 637                 else if (sport == NETBIOS_SSN_PORT || dport == NETBIOS_SSN_PORT)
 638                         nbt_tcp_print(bp, length);
 639 #endif
 640                 else if (sport == BEEP_PORT || dport == BEEP_PORT)
 641                         beep_print(bp, length);
 642                 else if (length > 2 &&
 643                     (sport == NAMESERVER_PORT || dport == NAMESERVER_PORT ||
 644                      sport == MULTICASTDNS_PORT || dport == MULTICASTDNS_PORT)) {
 645                         /*
 646                          * TCP DNS query has 2byte length at the head.
 647                          * XXX packet could be unaligned, it can go strange
 648                          */
 649                         ns_print(bp + 2, length - 2, 0);
 650                 } else if (sport == MSDP_PORT || dport == MSDP_PORT) {
 651                         msdp_print(bp, length);
 652                 }
 653                 else if (sport == LDP_PORT || dport == LDP_PORT)
 654                         printf(": LDP, length: %u", length);
 655         }
 656         return;
 657 bad:
 658         fputs("[bad opt]", stdout);
 659         if (ch != '\0')
 660                 putchar('>');
 661         return;
 662 trunc:
 663         fputs("[|tcp]", stdout);
 664         if (ch != '\0')
 665                 putchar('>');
 666 }
 667
 668 /*
 669  * RFC1122 says the following on data in RST segments:
 670  *
 671  *         4.2.2.12  RST Segment: RFC-793 Section 3.4
 672  *
 673  *            A TCP SHOULD allow a received RST segment to include data.
 674  *
 675  *            DISCUSSION
 676  *                 It has been suggested that a RST segment could contain
 677  *                 ASCII text that encoded and explained the cause of the
 678  *                 RST.  No standard has yet been established for such
 679  *                 data.
 680  *
 681  */
 682
 683 static void
 684 print_tcp_rst_data(register const u_char *sp, u_int length)
 685 {
 686         int c;
 687
 688         if (TTEST2(*sp, length))
 689                 printf(" [RST");
 690         else
 691                 printf(" [!RST");
 692         if (length > MAX_RST_DATA_LEN) {
 693                 length = MAX_RST_DATA_LEN;      /* can use -X for longer */
 694                 putchar('+');                   /* indicate we truncate */
 695         }
 696         putchar(' ');
 697         while (length-- && sp <= snapend) {
 698                 c = *sp++;
 699                 safeputchar(c);
 700         }
 701         putchar(']');
 702 }
 703
 704 #ifdef HAVE_LIBCRYPTO
 705 static int
 706 tcp_verify_signature(const struct ip *ip, struct tcphdr *tp,
 707     const u_char *data, int length, const u_char *rcvsig)
 708 {
 709         char sig[TCP_SIGLEN];
 710         char zero_proto = 0;
 711         MD5_CTX ctx;
 712         u_short savecsum, tlen;
 713
 714         if (tcpmd5secret == NULL)
 715                 return (-1);
 716
 717         MD5_Init(&ctx);
 718         /*
 719          * Step 1: Update MD5 hash with IP pseudo-header.
 720          */
 721         MD5_Update(&ctx, (char *)&ip->ip_src, sizeof(ip->ip_src));
 722         MD5_Update(&ctx, (char *)&ip->ip_dst, sizeof(ip->ip_dst));
 723         MD5_Update(&ctx, (char *)&zero_proto, sizeof(zero_proto));
 724         MD5_Update(&ctx, (char *)&ip->ip_p, sizeof(ip->ip_p));
 725         tlen = EXTRACT_16BITS(&ip->ip_len) - IP_HL(ip) * 4;
 726         tlen = htons(tlen);
 727         MD5_Update(&ctx, (char *)&tlen, sizeof(tlen));
 728         /*
 729          * Step 2: Update MD5 hash with TCP header, excluding options.
 730          * The TCP checksum must be set to zero.
 731          */
 732         savecsum = tp->th_sum;
 733         tp->th_sum = 0;
 734         MD5_Update(&ctx, (char *)tp, sizeof(struct tcphdr));
 735         tp->th_sum = savecsum;
 736         /*
 737          * Step 3: Update MD5 hash with TCP segment data, if present.
 738          */
 739         if (length > 0)
 740                 MD5_Update(&ctx, data, length);
 741         /*
 742          * Step 4: Update MD5 hash with shared secret.
 743          */
 744         MD5_Update(&ctx, tcpmd5secret, strlen(tcpmd5secret));
 745         MD5_Final(sig, &ctx);
 746
 747         return (memcmp(rcvsig, sig, 16));
 748 }
 749 #endif /* HAVE_LIBCRYPTO */