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[] =
  24     "@(#) $Header: /tcpdump/master/tcpdump/print-tcp.c,v 1.84 2001-02-03 05:04:49 itojun Exp $ (LBL)";
  25 #endif
  26
  27 #ifdef HAVE_CONFIG_H
  28 #include "config.h"
  29 #endif
  30
  31 #include <sys/param.h>
  32 #include <sys/time.h>
  33
  34 #include <rpc/rpc.h>
  35
  36 #include <netinet/in.h>
  37
  38 #include <stdio.h>
  39 #include <stdlib.h>
  40 #include <string.h>
  41 #include <ctype.h>
  42 #include <unistd.h>
  43
  44 #include "interface.h"
  45 #include "addrtoname.h"
  46 #include "extract.h"
  47
  48 #include "tcp.h"
  49
  50 #include "ip.h"
  51 #ifdef INET6
  52 #include "ip6.h"
  53 #endif
  54
  55 #include "nameser.h"
  56
  57 static void print_tcp_rst_data(register const u_char *sp, u_int length);
  58
  59 #define MAX_RST_DATA_LEN        30
  60
  61 /* Compatibility */
  62 #ifndef TCPOPT_WSCALE
  63 #define TCPOPT_WSCALE           3       /* window scale factor (rfc1072) */
  64 #endif
  65 #ifndef TCPOPT_SACKOK
  66 #define TCPOPT_SACKOK           4       /* selective ack ok (rfc1072) */
  67 #endif
  68 #ifndef TCPOPT_SACK
  69 #define TCPOPT_SACK             5       /* selective ack (rfc1072) */
  70 #endif
  71 #ifndef TCPOPT_ECHO
  72 #define TCPOPT_ECHO             6       /* echo (rfc1072) */
  73 #endif
  74 #ifndef TCPOPT_ECHOREPLY
  75 #define TCPOPT_ECHOREPLY        7       /* echo (rfc1072) */
  76 #endif
  77 #ifndef TCPOPT_TIMESTAMP
  78 #define TCPOPT_TIMESTAMP        8       /* timestamps (rfc1323) */
  79 #endif
  80 #ifndef TCPOPT_CC
  81 #define TCPOPT_CC               11      /* T/TCP CC options (rfc1644) */
  82 #endif
  83 #ifndef TCPOPT_CCNEW
  84 #define TCPOPT_CCNEW            12      /* T/TCP CC options (rfc1644) */
  85 #endif
  86 #ifndef TCPOPT_CCECHO
  87 #define TCPOPT_CCECHO           13      /* T/TCP CC options (rfc1644) */
  88 #endif
  89
  90 /*
  91  * Definitions required for ECN
  92  * for use if the OS running tcpdump does not have ECN
  93  */
  94 #ifndef TH_ECNECHO
  95 #define TH_ECNECHO              0x40    /* ECN Echo in tcp header */
  96 #endif
  97 #ifndef TH_CWR
  98 #define TH_CWR                  0x80    /* ECN Cwnd Reduced in tcp header*/
  99 #endif
 100
 101 struct tha {
 102 #ifndef INET6
 103         struct in_addr src;
 104         struct in_addr dst;
 105 #else
 106         struct in6_addr src;
 107         struct in6_addr dst;
 108 #endif /*INET6*/
 109         u_int port;
 110 };
 111
 112 struct tcp_seq_hash {
 113         struct tcp_seq_hash *nxt;
 114         struct tha addr;
 115         tcp_seq seq;
 116         tcp_seq ack;
 117 };
 118
 119 #define TSEQ_HASHSIZE 919
 120
 121 /* These tcp optinos do not have the size octet */
 122 #define ZEROLENOPT(o) ((o) == TCPOPT_EOL || (o) == TCPOPT_NOP)
 123
 124 static struct tcp_seq_hash tcp_seq_hash[TSEQ_HASHSIZE];
 125
 126
 127 #ifndef TELNET_PORT
 128 #define TELNET_PORT     23
 129 #endif
 130 #ifndef BGP_PORT
 131 #define BGP_PORT        179
 132 #endif
 133 #define NETBIOS_SSN_PORT 139
 134 #define BXXP_PORT        10288
 135 #ifndef NFS_PORT
 136 #define NFS_PORT        2049
 137 #endif
 138
 139 static int tcp_cksum(register const struct ip *ip,
 140                      register const struct tcphdr *tp,
 141                      register int len)
 142 {
 143         int i, tlen;
 144         union phu {
 145                 struct phdr {
 146                         u_int32_t src;
 147                         u_int32_t dst;
 148                         u_char mbz;
 149                         u_char proto;
 150                         u_int16_t len;
 151                 } ph;
 152                 u_int16_t pa[6];
 153         } phu;
 154         register const u_int16_t *sp;
 155         u_int32_t sum;
 156         tlen = ntohs(ip->ip_len) - ((const char *)tp-(const char*)ip);
 157
 158         /* pseudo-header.. */
 159         phu.ph.len = htons(tlen);
 160         phu.ph.mbz = 0;
 161         phu.ph.proto = IPPROTO_TCP;
 162         memcpy(&phu.ph.src, &ip->ip_src.s_addr, sizeof(u_int32_t));
 163         memcpy(&phu.ph.dst, &ip->ip_dst.s_addr, sizeof(u_int32_t));
 164
 165         sp = &phu.pa[0];
 166         sum = sp[0]+sp[1]+sp[2]+sp[3]+sp[4]+sp[5];
 167
 168         sp = (const u_int16_t *)tp;
 169
 170         for (i=0; i<(tlen&~1); i+= 2)
 171                 sum += *sp++;
 172
 173         if (tlen & 1) {
 174                 sum += htons( (*(const u_int8_t *)sp) << 8);
 175         }
 176
 177         while (sum > 0xffff)
 178                 sum = (sum & 0xffff) + (sum >> 16);
 179         sum = ~sum & 0xffff;
 180
 181         return (sum);
 182 }
 183
 184 #ifdef INET6
 185 static int tcp6_cksum(const struct ip6_hdr *ip6, const struct tcphdr *tp,
 186         int len)
 187 {
 188         int i, tlen;
 189         register const u_int16_t *sp;
 190         u_int32_t sum;
 191         union {
 192                 struct {
 193                         struct in6_addr ph_src;
 194                         struct in6_addr ph_dst;
 195                         u_int32_t       ph_len;
 196                         u_int8_t        ph_zero[3];
 197                         u_int8_t        ph_nxt;
 198                 } ph;
 199                 u_int16_t pa[20];
 200         } phu;
 201
 202         tlen = ntohs(ip6->ip6_plen) + sizeof(struct ip6_hdr) -
 203             ((const char *)tp - (const char*)ip6);
 204
 205         /* pseudo-header */
 206         memset(&phu, 0, sizeof(phu));
 207         phu.ph.ph_src = ip6->ip6_src;
 208         phu.ph.ph_dst = ip6->ip6_dst;
 209         phu.ph.ph_len = htonl(tlen);
 210         phu.ph.ph_nxt = IPPROTO_TCP;
 211
 212         sum = 0;
 213         for (i = 0; i < sizeof(phu.pa) / sizeof(phu.pa[0]); i++)
 214                 sum += phu.pa[i];
 215
 216         sp = (const u_int16_t *)tp;
 217
 218         for (i = 0; i < (tlen & ~1); i += 2)
 219                 sum += *sp++;
 220
 221         if (tlen & 1)
 222                 sum += htons((*(const u_int8_t *)sp) << 8);
 223
 224         while (sum > 0xffff)
 225                 sum = (sum & 0xffff) + (sum >> 16);
 226         sum = ~sum & 0xffff;
 227
 228         return (sum);
 229 }
 230 #endif
 231
 232 void
 233 tcp_print(register const u_char *bp, register u_int length,
 234           register const u_char *bp2, int fragmented)
 235 {
 236         register const struct tcphdr *tp;
 237         register const struct ip *ip;
 238         register u_char flags;
 239         register int hlen;
 240         register char ch;
 241         u_int16_t sport, dport, win, urp;
 242         u_int32_t seq, ack, thseq, thack;
 243         int threv;
 244 #ifdef INET6
 245         register const struct ip6_hdr *ip6;
 246 #endif
 247
 248         tp = (struct tcphdr *)bp;
 249         ip = (struct ip *)bp2;
 250 #ifdef INET6
 251         if (IP_V(ip) == 6)
 252                 ip6 = (struct ip6_hdr *)bp2;
 253         else
 254                 ip6 = NULL;
 255 #endif /*INET6*/
 256         ch = '\0';
 257         if (!TTEST(tp->th_dport)) {
 258                 (void)printf("%s > %s: [|tcp]",
 259                         ipaddr_string(&ip->ip_src),
 260                         ipaddr_string(&ip->ip_dst));
 261                 return;
 262         }
 263
 264         sport = ntohs(tp->th_sport);
 265         dport = ntohs(tp->th_dport);
 266
 267
 268         hlen = TH_OFF(tp) * 4;
 269
 270         /*
 271          * If data present and NFS port used, assume NFS.
 272          * Pass offset of data plus 4 bytes for RPC TCP msg length
 273          * to NFS print routines.
 274          */
 275         if (!qflag) {
 276                 if ((u_char *)tp + 4 + sizeof(struct rpc_msg) <= snapend &&
 277                     dport == NFS_PORT) {
 278                         nfsreq_print((u_char *)tp + hlen + 4, length - hlen,
 279                                      (u_char *)ip);
 280                         return;
 281                 } else if ((u_char *)tp + 4 + sizeof(struct rpc_msg)
 282                            <= snapend &&
 283                            sport == NFS_PORT) {
 284                         nfsreply_print((u_char *)tp + hlen + 4,length-hlen,
 285                                        (u_char *)ip);
 286                         return;
 287                 }
 288         }
 289 #ifdef INET6
 290         if (ip6) {
 291                 if (ip6->ip6_nxt == IPPROTO_TCP) {
 292                         (void)printf("%s.%s > %s.%s: ",
 293                                 ip6addr_string(&ip6->ip6_src),
 294                                 tcpport_string(sport),
 295                                 ip6addr_string(&ip6->ip6_dst),
 296                                 tcpport_string(dport));
 297                 } else {
 298                         (void)printf("%s > %s: ",
 299                                 tcpport_string(sport), tcpport_string(dport));
 300                 }
 301         } else
 302 #endif /*INET6*/
 303         {
 304                 if (ip->ip_p == IPPROTO_TCP) {
 305                         (void)printf("%s.%s > %s.%s: ",
 306                                 ipaddr_string(&ip->ip_src),
 307                                 tcpport_string(sport),
 308                                 ipaddr_string(&ip->ip_dst),
 309                                 tcpport_string(dport));
 310                 } else {
 311                         (void)printf("%s > %s: ",
 312                                 tcpport_string(sport), tcpport_string(dport));
 313                 }
 314         }
 315
 316         TCHECK(*tp);
 317
 318         seq = (u_int32_t)ntohl(tp->th_seq);
 319         ack = (u_int32_t)ntohl(tp->th_ack);
 320         win = ntohs(tp->th_win);
 321         urp = ntohs(tp->th_urp);
 322
 323         if (qflag) {
 324                 (void)printf("tcp %d", length - TH_OFF(tp) * 4);
 325                 return;
 326         }
 327         if ((flags = tp->th_flags) & (TH_SYN|TH_FIN|TH_RST|TH_PUSH|
 328                                       TH_ECNECHO|TH_CWR)) {
 329                 if (flags & TH_SYN)
 330                         putchar('S');
 331                 if (flags & TH_FIN)
 332                         putchar('F');
 333                 if (flags & TH_RST)
 334                         putchar('R');
 335                 if (flags & TH_PUSH)
 336                         putchar('P');
 337                 if (flags & TH_CWR)
 338                         putchar('W');   /* congestion _W_indow reduced (ECN) */
 339                 if (flags & TH_ECNECHO)
 340                         putchar('E');   /* ecn _E_cho sent (ECN) */
 341         } else
 342                 putchar('.');
 343
 344         if (!Sflag && (flags & TH_ACK)) {
 345                 register struct tcp_seq_hash *th;
 346                 register int rev;
 347                 struct tha tha;
 348                 /*
 349                  * Find (or record) the initial sequence numbers for
 350                  * this conversation.  (we pick an arbitrary
 351                  * collating order so there's only one entry for
 352                  * both directions).
 353                  */
 354 #ifdef INET6
 355                 memset(&tha, 0, sizeof(tha));
 356                 rev = 0;
 357                 if (ip6) {
 358                         if (sport > dport)
 359                                 rev = 1;
 360                         else if (sport == dport) {
 361                                 int i;
 362
 363                                 for (i = 0; i < 4; i++) {
 364                                         if (((u_int32_t *)(&ip6->ip6_src))[i] >
 365                                             ((u_int32_t *)(&ip6->ip6_dst))[i]) {
 366                                                 rev = 1;
 367                                                 break;
 368                                         }
 369                                 }
 370                         }
 371                         if (rev) {
 372                                 tha.src = ip6->ip6_dst;
 373                                 tha.dst = ip6->ip6_src;
 374                                 tha.port = dport << 16 | sport;
 375                         } else {
 376                                 tha.dst = ip6->ip6_dst;
 377                                 tha.src = ip6->ip6_src;
 378                                 tha.port = sport << 16 | dport;
 379                         }
 380                 } else {
 381                         if (sport > dport ||
 382                             (sport == dport &&
 383                              ip->ip_src.s_addr > ip->ip_dst.s_addr)) {
 384                                 rev = 1;
 385                         }
 386                         if (rev) {
 387                                 *(struct in_addr *)&tha.src = ip->ip_dst;
 388                                 *(struct in_addr *)&tha.dst = ip->ip_src;
 389                                 tha.port = dport << 16 | sport;
 390                         } else {
 391                                 *(struct in_addr *)&tha.dst = ip->ip_dst;
 392                                 *(struct in_addr *)&tha.src = ip->ip_src;
 393                                 tha.port = sport << 16 | dport;
 394                         }
 395                 }
 396 #else
 397                 if (sport < dport ||
 398                     (sport == dport &&
 399                      ip->ip_src.s_addr < ip->ip_dst.s_addr)) {
 400                         tha.src = ip->ip_src, tha.dst = ip->ip_dst;
 401                         tha.port = sport << 16 | dport;
 402                         rev = 0;
 403                 } else {
 404                         tha.src = ip->ip_dst, tha.dst = ip->ip_src;
 405                         tha.port = dport << 16 | sport;
 406                         rev = 1;
 407                 }
 408 #endif
 409
 410                 threv = rev;
 411                 for (th = &tcp_seq_hash[tha.port % TSEQ_HASHSIZE];
 412                      th->nxt; th = th->nxt)
 413                         if (!memcmp((char *)&tha, (char *)&th->addr,
 414                                   sizeof(th->addr)))
 415                                 break;
 416
 417                 if (!th->nxt || (flags & TH_SYN)) {
 418                         /* didn't find it or new conversation */
 419                         if (th->nxt == NULL) {
 420                                 th->nxt = (struct tcp_seq_hash *)
 421                                         calloc(1, sizeof(*th));
 422                                 if (th->nxt == NULL)
 423                                         error("tcp_print: calloc");
 424                         }
 425                         th->addr = tha;
 426                         if (rev)
 427                                 th->ack = seq, th->seq = ack - 1;
 428                         else
 429                                 th->seq = seq, th->ack = ack - 1;
 430                 } else {
 431                         if (rev)
 432                                 seq -= th->ack, ack -= th->seq;
 433                         else
 434                                 seq -= th->seq, ack -= th->ack;
 435                 }
 436
 437                 thseq = th->seq;
 438                 thack = th->ack;
 439         } else {
 440                 /*fool gcc*/
 441                 thseq = thack = threv = 0;
 442         }
 443         if (hlen > length) {
 444                 (void)printf(" [bad hdr length]");
 445                 return;
 446         }
 447
 448         if (IP_V(ip) == 4 && vflag && !fragmented) {
 449                 int sum;
 450                 if (TTEST2(tp->th_sport, length)) {
 451                         sum = tcp_cksum(ip, tp, length);
 452                         if (sum != 0)
 453                                 (void)printf(" [bad tcp cksum %x!]", sum);
 454                         else
 455                                 (void)printf(" [tcp sum ok]");
 456                 }
 457         }
 458 #ifdef INET6
 459         if (IP_V(ip) == 6 && ip6->ip6_plen && vflag && !fragmented) {
 460                 int sum;
 461                 if (TTEST2(tp->th_sport, length)) {
 462                         sum = tcp6_cksum(ip6, tp, length);
 463                         if (sum != 0)
 464                                 (void)printf(" [bad tcp cksum %x!]", sum);
 465                         else
 466                                 (void)printf(" [tcp sum ok]");
 467                 }
 468         }
 469 #endif
 470
 471         length -= hlen;
 472         if (vflag > 1 || length > 0 || flags & (TH_SYN | TH_FIN | TH_RST))
 473                 (void)printf(" %u:%u(%d)", seq, seq + length, length);
 474         if (flags & TH_ACK)
 475                 (void)printf(" ack %u", ack);
 476
 477         (void)printf(" win %d", win);
 478
 479         if (flags & TH_URG)
 480                 (void)printf(" urg %d", urp);
 481         /*
 482          * Handle any options.
 483          */
 484         if ((hlen -= sizeof(*tp)) > 0) {
 485                 register const u_char *cp;
 486                 register int i, opt, len, datalen;
 487
 488                 cp = (const u_char *)tp + sizeof(*tp);
 489                 putchar(' ');
 490                 ch = '<';
 491                 while (hlen > 0) {
 492                         putchar(ch);
 493                         TCHECK(*cp);
 494                         opt = *cp++;
 495                         if (ZEROLENOPT(opt))
 496                                 len = 1;
 497                         else {
 498                                 TCHECK(*cp);
 499                                 len = *cp++;    /* total including type, len */
 500                                 if (len < 2 || len > hlen)
 501                                         goto bad;
 502                                 --hlen;         /* account for length byte */
 503                         }
 504                         --hlen;                 /* account for type byte */
 505                         datalen = 0;
 506
 507 /* Bail if "l" bytes of data are not left or were not captured  */
 508 #define LENCHECK(l) { if ((l) > hlen) goto bad; TCHECK2(*cp, l); }
 509
 510                         switch (opt) {
 511
 512                         case TCPOPT_MAXSEG:
 513                                 (void)printf("mss");
 514                                 datalen = 2;
 515                                 LENCHECK(datalen);
 516                                 (void)printf(" %u", EXTRACT_16BITS(cp));
 517
 518                                 break;
 519
 520                         case TCPOPT_EOL:
 521                                 (void)printf("eol");
 522                                 break;
 523
 524                         case TCPOPT_NOP:
 525                                 (void)printf("nop");
 526                                 break;
 527
 528                         case TCPOPT_WSCALE:
 529                                 (void)printf("wscale");
 530                                 datalen = 1;
 531                                 LENCHECK(datalen);
 532                                 (void)printf(" %u", *cp);
 533                                 break;
 534
 535                         case TCPOPT_SACKOK:
 536                                 (void)printf("sackOK");
 537                                 break;
 538
 539                         case TCPOPT_SACK:
 540                                 (void)printf("sack");
 541                                 datalen = len - 2;
 542                                 if (datalen % 8 != 0) {
 543                                         (void)printf(" malformed sack ");
 544                                 } else {
 545                                         u_int32_t s, e;
 546
 547                                         (void)printf(" sack %d ", datalen / 8);
 548                                         for (i = 0; i < datalen; i += 8) {
 549                                                 LENCHECK(i + 4);
 550                                                 s = EXTRACT_32BITS(cp + i);
 551                                                 LENCHECK(i + 8);
 552                                                 e = EXTRACT_32BITS(cp + i + 4);
 553                                                 if (threv) {
 554                                                         s -= thseq;
 555                                                         e -= thseq;
 556                                                 } else {
 557                                                         s -= thack;
 558                                                         e -= thack;
 559                                                 }
 560                                                 (void)printf("{%u:%u}", s, e);
 561                                         }
 562                                         (void)printf(" ");
 563                                 }
 564                                 break;
 565
 566                         case TCPOPT_ECHO:
 567                                 (void)printf("echo");
 568                                 datalen = 4;
 569                                 LENCHECK(datalen);
 570                                 (void)printf(" %u", EXTRACT_32BITS(cp));
 571                                 break;
 572
 573                         case TCPOPT_ECHOREPLY:
 574                                 (void)printf("echoreply");
 575                                 datalen = 4;
 576                                 LENCHECK(datalen);
 577                                 (void)printf(" %u", EXTRACT_32BITS(cp));
 578                                 break;
 579
 580                         case TCPOPT_TIMESTAMP:
 581                                 (void)printf("timestamp");
 582                                 datalen = 8;
 583                                 LENCHECK(4);
 584                                 (void)printf(" %u", EXTRACT_32BITS(cp));
 585                                 LENCHECK(datalen);
 586                                 (void)printf(" %u", EXTRACT_32BITS(cp + 4));
 587                                 break;
 588
 589                         case TCPOPT_CC:
 590                                 (void)printf("cc");
 591                                 datalen = 4;
 592                                 LENCHECK(datalen);
 593                                 (void)printf(" %u", EXTRACT_32BITS(cp));
 594                                 break;
 595
 596                         case TCPOPT_CCNEW:
 597                                 (void)printf("ccnew");
 598                                 datalen = 4;
 599                                 LENCHECK(datalen);
 600                                 (void)printf(" %u", EXTRACT_32BITS(cp));
 601                                 break;
 602
 603                         case TCPOPT_CCECHO:
 604                                 (void)printf("ccecho");
 605                                 datalen = 4;
 606                                 LENCHECK(datalen);
 607                                 (void)printf(" %u", EXTRACT_32BITS(cp));
 608                                 break;
 609
 610                         default:
 611                                 (void)printf("opt-%d:", opt);
 612                                 datalen = len - 2;
 613                                 for (i = 0; i < datalen; ++i) {
 614                                         LENCHECK(i);
 615                                         (void)printf("%02x", cp[i]);
 616                                 }
 617                                 break;
 618                         }
 619
 620                         /* Account for data printed */
 621                         cp += datalen;
 622                         hlen -= datalen;
 623
 624                         /* Check specification against observed length */
 625                         ++datalen;                      /* option octet */
 626                         if (!ZEROLENOPT(opt))
 627                                 ++datalen;              /* size octet */
 628                         if (datalen != len)
 629                                 (void)printf("[len %d]", len);
 630                         ch = ',';
 631                         if (opt == TCPOPT_EOL)
 632                                 break;
 633                 }
 634                 putchar('>');
 635         }
 636
 637         if (length <= 0)
 638                 return;
 639
 640         /*
 641          * Decode payload if necessary.
 642          */
 643         bp += TH_OFF(tp) * 4;
 644         if (flags & TH_RST) {
 645                 if (vflag)
 646                         print_tcp_rst_data(bp, length);
 647         } else {
 648                 if (sport == TELNET_PORT || dport == TELNET_PORT) {
 649                         if (!qflag && vflag)
 650                                 telnet_print(bp, length);
 651                 } else if (sport == BGP_PORT || dport == BGP_PORT)
 652                         bgp_print(bp, length);
 653                 else if (sport == NETBIOS_SSN_PORT || dport == NETBIOS_SSN_PORT)
 654                         nbt_tcp_print(bp, length);
 655                 else if (sport == BXXP_PORT || dport == BXXP_PORT)
 656                         bxxp_print(bp, length);
 657                 else if (length > 2 &&
 658                     (sport == NAMESERVER_PORT || dport == NAMESERVER_PORT)) {
 659                         /* TCP DNS query has 2byte length at the head */
 660                         ns_print(bp + 2, length - 2);
 661                 }
 662         }
 663         return;
 664 bad:
 665         fputs("[bad opt]", stdout);
 666         if (ch != '\0')
 667                 putchar('>');
 668         return;
 669 trunc:
 670         fputs("[|tcp]", stdout);
 671         if (ch != '\0')
 672                 putchar('>');
 673 }
 674
 675 /*
 676  * RFC1122 says the following on data in RST segments:
 677  *
 678  *         4.2.2.12  RST Segment: RFC-793 Section 3.4
 679  *
 680  *            A TCP SHOULD allow a received RST segment to include data.
 681  *
 682  *            DISCUSSION
 683  *                 It has been suggested that a RST segment could contain
 684  *                 ASCII text that encoded and explained the cause of the
 685  *                 RST.  No standard has yet been established for such
 686  *                 data.
 687  *
 688  */
 689
 690 static void
 691 print_tcp_rst_data(register const u_char *sp, u_int length)
 692 {
 693         int c;
 694
 695         if (TTEST2(*sp, length))
 696                 printf(" [RST");
 697         else
 698                 printf(" [!RST");
 699         if (length > MAX_RST_DATA_LEN) {
 700                 length = MAX_RST_DATA_LEN;      /* can use -X for longer */
 701                 putchar('+');                   /* indicate we truncate */
 702         }
 703         putchar(' ');
 704         while (length-- && sp <= snapend) {
 705                 c = *sp++;
 706                 safeputchar(c);
 707         }
 708         putchar(']');
 709 }