The Tcpdump Group git mirrors - tcpdump/blob - print-ip.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-ip.c,v 1.127 2003-06-07 11:57:53 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 <stdio.h>
  34 #include <stdlib.h>
  35 #include <string.h>
  36
  37 #include "addrtoname.h"
  38 #include "interface.h"
  39 #include "extract.h"                    /* must come after interface.h */
  40
  41 #include "ip.h"
  42 #include "ipproto.h"
  43
  44 /*
  45  * print the recorded route in an IP RR, LSRR or SSRR option.
  46  */
  47 static void
  48 ip_printroute(const char *type, register const u_char *cp, u_int length)
  49 {
  50         register u_int ptr = cp[2] - 1;
  51         register u_int len;
  52
  53         printf(" %s{", type);
  54         if ((length + 1) & 3)
  55                 printf(" [bad length %d]", length);
  56         if (ptr < 3 || ((ptr + 1) & 3) || ptr > length + 1)
  57                 printf(" [bad ptr %d]", cp[2]);
  58
  59         type = "";
  60         for (len = 3; len < length; len += 4) {
  61                 if (ptr == len)
  62                         type = "#";
  63                 printf("%s%s", type, ipaddr_string(&cp[len]));
  64                 type = " ";
  65         }
  66         printf("%s}", ptr == len? "#" : "");
  67 }
  68
  69 /*
  70  * If source-routing is present, return the final destination.
  71  * Otherwise, return IP destination.
  72  *
  73  * This is used for UDP and TCP pseudo-header in the checksum
  74  * calculation.
  75  */
  76 u_int32_t
  77 ip_finddst(const struct ip *ip)
  78 {
  79         int length;
  80         int len;
  81         const u_char *cp;
  82         u_int32_t retval;
  83
  84         cp = (const u_char *)(ip + 1);
  85         length = (IP_HL(ip) << 2) - sizeof(struct ip);
  86
  87         for (; length > 0; cp += len, length -= len) {
  88                 int tt = *cp;
  89
  90                 if (tt == IPOPT_NOP || tt == IPOPT_EOL)
  91                         len = 1;
  92                 else {
  93                         if (&cp[1] >= snapend) {
  94                                 return 0;
  95                         }
  96                         len = cp[1];
  97                 }
  98                 if (len <= 0) {
  99                         return 0;
 100                 }
 101                 if (&cp[1] >= snapend || cp + len > snapend) {
 102                         return 0;
 103                 }
 104                 switch (tt) {
 105
 106                 case IPOPT_SSRR:
 107                 case IPOPT_LSRR:
 108                         memcpy(&retval, cp + len - 4, 4);
 109                         return retval;
 110                 }
 111         }
 112         return ip->ip_dst.s_addr;
 113 }
 114
 115 static void
 116 ip_printts(register const u_char *cp, u_int length)
 117 {
 118         register u_int ptr = cp[2] - 1;
 119         register u_int len = 0;
 120         int hoplen;
 121         const char *type;
 122
 123         printf(" TS{");
 124         hoplen = ((cp[3]&0xF) != IPOPT_TS_TSONLY) ? 8 : 4;
 125         if ((length - 4) & (hoplen-1))
 126                 printf("[bad length %d]", length);
 127         if (ptr < 4 || ((ptr - 4) & (hoplen-1)) || ptr > length + 1)
 128                 printf("[bad ptr %d]", cp[2]);
 129         switch (cp[3]&0xF) {
 130         case IPOPT_TS_TSONLY:
 131                 printf("TSONLY");
 132                 break;
 133         case IPOPT_TS_TSANDADDR:
 134                 printf("TS+ADDR");
 135                 break;
 136         /*
 137          * prespecified should really be 3, but some ones might send 2
 138          * instead, and the IPOPT_TS_PRESPEC constant can apparently
 139          * have both values, so we have to hard-code it here.
 140          */
 141
 142         case 2:
 143                 printf("PRESPEC2.0");
 144                 break;
 145         case 3:                 /* IPOPT_TS_PRESPEC */
 146                 printf("PRESPEC");
 147                 break;
 148         default:
 149                 printf("[bad ts type %d]", cp[3]&0xF);
 150                 goto done;
 151         }
 152
 153         type = " ";
 154         for (len = 4; len < length; len += hoplen) {
 155                 if (ptr == len)
 156                         type = " ^ ";
 157                 printf("%s%d@%s", type, EXTRACT_32BITS(&cp[len+hoplen-4]),
 158                        hoplen!=8 ? "" : ipaddr_string(&cp[len]));
 159                 type = " ";
 160         }
 161
 162 done:
 163         printf("%s", ptr == len ? " ^ " : "");
 164
 165         if (cp[3]>>4)
 166                 printf(" [%d hops not recorded]} ", cp[3]>>4);
 167         else
 168                 printf("}");
 169 }
 170
 171 /*
 172  * print IP options.
 173  */
 174 static void
 175 ip_optprint(register const u_char *cp, u_int length)
 176 {
 177         register u_int len;
 178
 179         for (; length > 0; cp += len, length -= len) {
 180                 int tt = *cp;
 181
 182                 if (tt == IPOPT_NOP || tt == IPOPT_EOL)
 183                         len = 1;
 184                 else {
 185                         if (&cp[1] >= snapend) {
 186                                 printf("[|ip]");
 187                                 return;
 188                         }
 189                         len = cp[1];
 190                 }
 191                 if (len <= 0) {
 192                         printf("[|ip op len %d]", len);
 193                         return;
 194                 }
 195                 if (&cp[1] >= snapend || cp + len > snapend) {
 196                         printf("[|ip]");
 197                         return;
 198                 }
 199                 switch (tt) {
 200
 201                 case IPOPT_EOL:
 202                         printf(" EOL");
 203                         if (length > 1)
 204                                 printf("-%d", length - 1);
 205                         return;
 206
 207                 case IPOPT_NOP:
 208                         printf(" NOP");
 209                         break;
 210
 211                 case IPOPT_TS:
 212                         ip_printts(cp, len);
 213                         break;
 214
 215 #ifndef IPOPT_SECURITY
 216 #define IPOPT_SECURITY 130
 217 #endif /* IPOPT_SECURITY */
 218                 case IPOPT_SECURITY:
 219                         printf(" SECURITY{%d}", len);
 220                         break;
 221
 222                 case IPOPT_RR:
 223                         ip_printroute("RR", cp, len);
 224                         break;
 225
 226                 case IPOPT_SSRR:
 227                         ip_printroute("SSRR", cp, len);
 228                         break;
 229
 230                 case IPOPT_LSRR:
 231                         ip_printroute("LSRR", cp, len);
 232                         break;
 233
 234 #ifndef IPOPT_RA
 235 #define IPOPT_RA 148            /* router alert */
 236 #endif
 237                 case IPOPT_RA:
 238                         printf(" RA");
 239                         if (len != 4)
 240                                 printf("{%d}", len);
 241                         else if (cp[2] || cp[3])
 242                                 printf("%d.%d", cp[2], cp[3]);
 243                         break;
 244
 245                 default:
 246                         printf(" IPOPT-%d{%d}", cp[0], len);
 247                         break;
 248                 }
 249         }
 250 }
 251
 252 /*
 253  * compute an IP header checksum.
 254  * don't modifiy the packet.
 255  */
 256 u_short
 257 in_cksum(const u_short *addr, register u_int len, int csum)
 258 {
 259         int nleft = len;
 260         const u_short *w = addr;
 261         u_short answer;
 262         int sum = csum;
 263
 264         /*
 265          *  Our algorithm is simple, using a 32 bit accumulator (sum),
 266          *  we add sequential 16 bit words to it, and at the end, fold
 267          *  back all the carry bits from the top 16 bits into the lower
 268          *  16 bits.
 269          */
 270         while (nleft > 1)  {
 271                 sum += *w++;
 272                 nleft -= 2;
 273         }
 274         if (nleft == 1)
 275                 sum += htons(*(u_char *)w<<8);
 276
 277         /*
 278          * add back carry outs from top 16 bits to low 16 bits
 279          */
 280         sum = (sum >> 16) + (sum & 0xffff);     /* add hi 16 to low 16 */
 281         sum += (sum >> 16);                     /* add carry */
 282         answer = ~sum;                          /* truncate to 16 bits */
 283         return (answer);
 284 }
 285
 286 /*
 287  * Given the host-byte-order value of the checksum field in a packet
 288  * header, and the network-byte-order computed checksum of the data
 289  * that the checksum covers (including the checksum itself), compute
 290  * what the checksum field *should* have been.
 291  */
 292 u_int16_t
 293 in_cksum_shouldbe(u_int16_t sum, u_int16_t computed_sum)
 294 {
 295         u_int32_t shouldbe;
 296
 297         /*
 298          * The value that should have gone into the checksum field
 299          * is the negative of the value gotten by summing up everything
 300          * *but* the checksum field.
 301          *
 302          * We can compute that by subtracting the value of the checksum
 303          * field from the sum of all the data in the packet, and then
 304          * computing the negative of that value.
 305          *
 306          * "sum" is the value of the checksum field, and "computed_sum"
 307          * is the negative of the sum of all the data in the packets,
 308          * so that's -(-computed_sum - sum), or (sum + computed_sum).
 309          *
 310          * All the arithmetic in question is one's complement, so the
 311          * addition must include an end-around carry; we do this by
 312          * doing the arithmetic in 32 bits (with no sign-extension),
 313          * and then adding the upper 16 bits of the sum, which contain
 314          * the carry, to the lower 16 bits of the sum, and then do it
 315          * again in case *that* sum produced a carry.
 316          *
 317          * As RFC 1071 notes, the checksum can be computed without
 318          * byte-swapping the 16-bit words; summing 16-bit words
 319          * on a big-endian machine gives a big-endian checksum, which
 320          * can be directly stuffed into the big-endian checksum fields
 321          * in protocol headers, and summing words on a little-endian
 322          * machine gives a little-endian checksum, which must be
 323          * byte-swapped before being stuffed into a big-endian checksum
 324          * field.
 325          *
 326          * "computed_sum" is a network-byte-order value, so we must put
 327          * it in host byte order before subtracting it from the
 328          * host-byte-order value from the header; the adjusted checksum
 329          * will be in host byte order, which is what we'll return.
 330          */
 331         shouldbe = sum;
 332         shouldbe += ntohs(computed_sum);
 333         shouldbe = (shouldbe & 0xFFFF) + (shouldbe >> 16);
 334         shouldbe = (shouldbe & 0xFFFF) + (shouldbe >> 16);
 335         return shouldbe;
 336 }
 337
 338 #ifndef IP_MF
 339 #define IP_MF 0x2000
 340 #endif /* IP_MF */
 341 #ifndef IP_DF
 342 #define IP_DF 0x4000
 343 #endif /* IP_DF */
 344 #define IP_RES 0x8000
 345
 346 static struct tok ip_frag_values[] = {
 347         { IP_MF,        "+" },
 348         { IP_DF,        "DF" },
 349         { IP_RES,       "rsvd" }, /* The RFC3514 evil ;-) bit */
 350         { 0,            NULL }
 351 };
 352
 353 /*
 354  * print an IP datagram.
 355  */
 356 void
 357 ip_print(register const u_char *bp, register u_int length)
 358 {
 359         register const struct ip *ip;
 360         register u_int hlen, len, len0, off;
 361         register const u_char *cp;
 362         u_char nh;
 363         int advance;
 364         struct protoent *proto;
 365         u_int16_t sum, ip_sum;
 366         const char *sep = "";
 367
 368         ip = (const struct ip *)bp;
 369         if (IP_V(ip) != 4) { /* print version if != 4 */
 370             printf("IP%u ", IP_V(ip));
 371             if (IP_V(ip) == 6)
 372                 printf(", wrong link-layer encapsulation");
 373         }
 374         else
 375             printf("IP ");
 376
 377         if ((u_char *)(ip + 1) > snapend) {
 378                 printf("[|ip]");
 379                 return;
 380         }
 381         if (length < sizeof (struct ip)) {
 382                 (void)printf("truncated-ip %d", length);
 383                 return;
 384         }
 385         hlen = IP_HL(ip) * 4;
 386         if (hlen < sizeof (struct ip)) {
 387                 (void)printf("bad-hlen %d", hlen);
 388                 return;
 389         }
 390
 391         len = EXTRACT_16BITS(&ip->ip_len);
 392         if (length < len)
 393                 (void)printf("truncated-ip - %d bytes missing! ",
 394                         len - length);
 395         len -= hlen;
 396         len0 = len;
 397
 398         off = EXTRACT_16BITS(&ip->ip_off);
 399
 400         if (vflag) {
 401             (void)printf("(tos 0x%x", (int)ip->ip_tos);
 402             /* ECN bits */
 403             if (ip->ip_tos & 0x03) {
 404                 switch (ip->ip_tos & 0x03) {
 405                 case 1:
 406                     (void)printf(",ECT(1)");
 407                     break;
 408                 case 2:
 409                     (void)printf(",ECT(0)");
 410                     break;
 411                 case 3:
 412                     (void)printf(",CE");
 413                 }
 414             }
 415
 416             if (ip->ip_ttl >= 1)
 417                 (void)printf(", ttl %3u", ip->ip_ttl);
 418
 419             /*
 420              * for the firewall guys, print id, offset.
 421              * On all but the last stick a "+" in the flags portion.
 422              * For unfragmented datagrams, note the don't fragment flag.
 423              */
 424
 425             (void)printf(", id %u, offset %u, flags [%s]",
 426                              EXTRACT_16BITS(&ip->ip_id),
 427                              (off & 0x1fff) * 8,
 428                              bittok2str(ip_frag_values, "none", off & 0xe000 ));
 429
 430             (void)printf(", length: %u", EXTRACT_16BITS(&ip->ip_len));
 431
 432             if ((hlen - sizeof(struct ip)) > 0) {
 433                 (void)printf(", optlength: %u (", hlen - (u_int)sizeof(struct ip));
 434                 ip_optprint((u_char *)(ip + 1), hlen - sizeof(struct ip));
 435                 printf(" )");
 436             }
 437
 438             if ((u_char *)ip + hlen <= snapend) {
 439                 sum = in_cksum((const u_short *)ip, hlen, 0);
 440                 if (sum != 0) {
 441                     ip_sum = EXTRACT_16BITS(&ip->ip_sum);
 442                     (void)printf("%sbad cksum %x (->%x)!", sep,
 443                              ip_sum,
 444                              in_cksum_shouldbe(ip_sum, sum));
 445                     sep = ", ";
 446                 }
 447             }
 448
 449             printf(") ");
 450         }
 451
 452         /*
 453          * If this is fragment zero, hand it to the next higher
 454          * level protocol.
 455          */
 456         if ((off & 0x1fff) == 0) {
 457                 cp = (const u_char *)ip + hlen;
 458                 nh = ip->ip_p;
 459
 460                 if (nh != IPPROTO_TCP && nh != IPPROTO_UDP &&
 461                     nh != IPPROTO_SCTP) {
 462                         (void)printf("%s > %s: ", ipaddr_string(&ip->ip_src),
 463                                 ipaddr_string(&ip->ip_dst));
 464                 }
 465 again:
 466                 switch (nh) {
 467
 468                 case IPPROTO_AH:
 469                         nh = *cp;
 470                         advance = ah_print(cp);
 471                         cp += advance;
 472                         len -= advance;
 473                         goto again;
 474
 475                 case IPPROTO_ESP:
 476                     {
 477                         int enh, padlen;
 478                         advance = esp_print(cp, (const u_char *)ip, &enh, &padlen);
 479                         cp += advance;
 480                         len -= advance + padlen;
 481                         if (enh < 0)
 482                                 break;
 483                         nh = enh & 0xff;
 484                         goto again;
 485                     }
 486
 487                 case IPPROTO_IPCOMP:
 488                     {
 489                         int enh;
 490                         advance = ipcomp_print(cp, &enh);
 491                         cp += advance;
 492                         len -= advance;
 493                         if (enh < 0)
 494                                 break;
 495                         nh = enh & 0xff;
 496                         goto again;
 497                     }
 498
 499                 case IPPROTO_SCTP:
 500                         sctp_print(cp, (const u_char *)ip, len);
 501                         break;
 502
 503                 case IPPROTO_TCP:
 504                         tcp_print(cp, len, (const u_char *)ip, (off &~ 0x6000));
 505                         break;
 506
 507                 case IPPROTO_UDP:
 508                         udp_print(cp, len, (const u_char *)ip, (off &~ 0x6000));
 509                         break;
 510
 511                 case IPPROTO_ICMP:
 512                         /* pass on the MF bit plus the offset to detect fragments */
 513                         icmp_print(cp, len, (const u_char *)ip, (off & 0x3fff));
 514                         break;
 515
 516                 case IPPROTO_IGRP:
 517                         igrp_print(cp, len, (const u_char *)ip);
 518                         break;
 519
 520                 case IPPROTO_ND:
 521                         (void)printf(" nd %d", len);
 522                         break;
 523
 524                 case IPPROTO_EGP:
 525                         egp_print(cp);
 526                         break;
 527
 528                 case IPPROTO_OSPF:
 529                         ospf_print(cp, len, (const u_char *)ip);
 530                         break;
 531
 532                 case IPPROTO_IGMP:
 533                         igmp_print(cp, len);
 534                         break;
 535
 536                 case IPPROTO_IPV4:
 537                         /* DVMRP multicast tunnel (ip-in-ip encapsulation) */
 538                         ip_print(cp, len);
 539                         if (! vflag) {
 540                                 printf(" (ipip-proto-4)");
 541                                 return;
 542                         }
 543                         break;
 544
 545 #ifdef INET6
 546                 case IPPROTO_IPV6:
 547                         /* ip6-in-ip encapsulation */
 548                         ip6_print(cp, len);
 549                         break;
 550 #endif /*INET6*/
 551
 552                 case IPPROTO_RSVP:
 553                         rsvp_print(cp, len);
 554                         break;
 555
 556                 case IPPROTO_GRE:
 557                         /* do it */
 558                         gre_print(cp, len);
 559                         break;
 560
 561                 case IPPROTO_MOBILE:
 562                         mobile_print(cp, len);
 563                         break;
 564
 565                 case IPPROTO_PIM:
 566                         pim_print(cp, len);
 567                         break;
 568
 569                 case IPPROTO_VRRP:
 570                         vrrp_print(cp, len, ip->ip_ttl);
 571                         break;
 572
 573                 default:
 574                         if ((proto = getprotobynumber(nh)) != NULL)
 575                                 (void)printf(" %s", proto->p_name);
 576                         else
 577                                 (void)printf(" ip-proto-%d", nh);
 578                         printf(" %d", len);
 579                         break;
 580                 }
 581         } else {
 582             /* Ultra quiet now means that all this stuff should be suppressed */
 583             if (qflag > 1) return;
 584
 585             /*
 586              * if this isn't the first frag, we're missing the
 587              * next level protocol header.  print the ip addr
 588              * and the protocol.
 589              */
 590             if (off & 0x1fff) {
 591                 (void)printf("%s > %s:", ipaddr_string(&ip->ip_src),
 592                              ipaddr_string(&ip->ip_dst));
 593                 if ((proto = getprotobynumber(ip->ip_p)) != NULL)
 594                     (void)printf(" %s", proto->p_name);
 595                 else
 596                     (void)printf(" ip-proto-%d", ip->ip_p);
 597             }
 598         }
 599 }
 600
 601 void
 602 ipN_print(register const u_char *bp, register u_int length)
 603 {
 604         struct ip *ip, hdr;
 605
 606         ip = (struct ip *)bp;
 607         if (length < 4) {
 608                 (void)printf("truncated-ip %d", length);
 609                 return;
 610         }
 611         memcpy (&hdr, (char *)ip, 4);
 612         switch (IP_V(&hdr)) {
 613         case 4:
 614                 ip_print (bp, length);
 615                 return;
 616 #ifdef INET6
 617         case 6:
 618                 ip6_print (bp, length);
 619                 return;
 620 #endif
 621         default:
 622                 (void)printf("unknown ip %d", IP_V(&hdr));
 623                 return;
 624         }
 625 }
 626
 627
 628