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 1.73 1999-11-21 03:47:35 assar Exp $ (LBL)";
  25 #endif
  26
  27 #include <sys/param.h>
  28 #include <sys/time.h>
  29 #include <sys/socket.h>
  30
  31 #include <netinet/in.h>
  32 #include <netinet/in_systm.h>
  33 #include <netinet/ip.h>
  34 #include <netinet/ip_var.h>
  35 #include <netinet/udp.h>
  36 #include <netinet/udp_var.h>
  37 #include <netinet/tcp.h>
  38
  39 #ifdef HAVE_MALLOC_H
  40 #include <malloc.h>
  41 #endif
  42 #include <stdio.h>
  43 #include <stdlib.h>
  44 #include <string.h>
  45 #include <unistd.h>
  46
  47 #include "addrtoname.h"
  48 #include "interface.h"
  49 #include "extract.h"                    /* must come after interface.h */
  50
  51 /* Compatibility */
  52 #ifndef IPPROTO_ND
  53 #define IPPROTO_ND      77
  54 #endif
  55
  56 #ifndef IN_CLASSD
  57 #define IN_CLASSD(i) (((int32_t)(i) & 0xf0000000) == 0xe0000000)
  58 #endif
  59
  60 /* (following from ipmulti/mrouted/prune.h) */
  61
  62 /*
  63  * The packet format for a traceroute request.
  64  */
  65 struct tr_query {
  66         u_int  tr_src;                  /* traceroute source */
  67         u_int  tr_dst;                  /* traceroute destination */
  68         u_int  tr_raddr;                /* traceroute response address */
  69 #if defined(WORDS_BIGENDIAN) || (defined(BYTE_ORDER) && (BYTE_ORDER == BIG_ENDIAN))
  70         struct {
  71                 u_int   ttl : 8;        /* traceroute response ttl */
  72                 u_int   qid : 24;       /* traceroute query id */
  73         } q;
  74 #else
  75         struct {
  76                 u_int   qid : 24;       /* traceroute query id */
  77                 u_int   ttl : 8;        /* traceroute response ttl */
  78         } q;
  79 #endif
  80 };
  81
  82 #define tr_rttl q.ttl
  83 #define tr_qid  q.qid
  84
  85 /*
  86  * Traceroute response format.  A traceroute response has a tr_query at the
  87  * beginning, followed by one tr_resp for each hop taken.
  88  */
  89 struct tr_resp {
  90         u_int tr_qarr;                  /* query arrival time */
  91         u_int tr_inaddr;                /* incoming interface address */
  92         u_int tr_outaddr;               /* outgoing interface address */
  93         u_int tr_rmtaddr;               /* parent address in source tree */
  94         u_int tr_vifin;                 /* input packet count on interface */
  95         u_int tr_vifout;                /* output packet count on interface */
  96         u_int tr_pktcnt;                /* total incoming packets for src-grp */
  97         u_char  tr_rproto;              /* routing proto deployed on router */
  98         u_char  tr_fttl;                /* ttl required to forward on outvif */
  99         u_char  tr_smask;               /* subnet mask for src addr */
 100         u_char  tr_rflags;              /* forwarding error codes */
 101 };
 102
 103 /* defs within mtrace */
 104 #define TR_QUERY 1
 105 #define TR_RESP 2
 106
 107 /* fields for tr_rflags (forwarding error codes) */
 108 #define TR_NO_ERR       0
 109 #define TR_WRONG_IF     1
 110 #define TR_PRUNED       2
 111 #define TR_OPRUNED      3
 112 #define TR_SCOPED       4
 113 #define TR_NO_RTE       5
 114 #define TR_NO_FWD       7
 115 #define TR_NO_SPACE     0x81
 116 #define TR_OLD_ROUTER   0x82
 117
 118 /* fields for tr_rproto (routing protocol) */
 119 #define TR_PROTO_DVMRP  1
 120 #define TR_PROTO_MOSPF  2
 121 #define TR_PROTO_PIM    3
 122 #define TR_PROTO_CBT    4
 123
 124 static void print_mtrace(register const u_char *bp, register u_int len)
 125 {
 126         register struct tr_query *tr = (struct tr_query *)(bp + 8);
 127
 128         printf("mtrace %d: %s to %s reply-to %s", tr->tr_qid,
 129                 ipaddr_string(&tr->tr_src), ipaddr_string(&tr->tr_dst),
 130                 ipaddr_string(&tr->tr_raddr));
 131         if (IN_CLASSD(ntohl(tr->tr_raddr)))
 132                 printf(" with-ttl %d", tr->tr_rttl);
 133 }
 134
 135 static void print_mresp(register const u_char *bp, register u_int len)
 136 {
 137         register struct tr_query *tr = (struct tr_query *)(bp + 8);
 138
 139         printf("mresp %d: %s to %s reply-to %s", tr->tr_qid,
 140                 ipaddr_string(&tr->tr_src), ipaddr_string(&tr->tr_dst),
 141                 ipaddr_string(&tr->tr_raddr));
 142         if (IN_CLASSD(ntohl(tr->tr_raddr)))
 143                 printf(" with-ttl %d", tr->tr_rttl);
 144 }
 145
 146 static void
 147 igmp_print(register const u_char *bp, register u_int len,
 148            register const u_char *bp2)
 149 {
 150         register const struct ip *ip;
 151
 152         ip = (const struct ip *)bp2;
 153         (void)printf("%s > %s: ",
 154                 ipaddr_string(&ip->ip_src),
 155                 ipaddr_string(&ip->ip_dst));
 156
 157         TCHECK2(bp[0], 8);
 158         switch (bp[0]) {
 159         case 0x11:
 160                 (void)printf("igmp query");
 161                 if (*(int *)&bp[4])
 162                         (void)printf(" [gaddr %s]", ipaddr_string(&bp[4]));
 163                 if (len != 8)
 164                         (void)printf(" [len %d]", len);
 165                 break;
 166         case 0x12:
 167                 (void)printf("igmp report %s", ipaddr_string(&bp[4]));
 168                 if (len != 8)
 169                         (void)printf(" [len %d]", len);
 170                 break;
 171         case 0x16:
 172                 (void)printf("igmp nreport %s", ipaddr_string(&bp[4]));
 173                 break;
 174         case 0x17:
 175                 (void)printf("igmp leave %s", ipaddr_string(&bp[4]));
 176                 break;
 177         case 0x13:
 178                 (void)printf("igmp dvmrp");
 179                 if (len < 8)
 180                         (void)printf(" [len %d]", len);
 181                 else
 182                         dvmrp_print(bp, len);
 183                 break;
 184         case 0x14:
 185                 (void)printf("igmp pim");
 186                 igmp_pim_print(bp, len);
 187                 break;
 188         case 0x1e:
 189                 print_mresp(bp, len);
 190                 break;
 191         case 0x1f:
 192                 print_mtrace(bp, len);
 193                 break;
 194         default:
 195                 (void)printf("igmp-%d", bp[0] & 0xf);
 196                 break;
 197         }
 198         if ((bp[0] >> 4) != 1)
 199                 (void)printf(" [v%d]", bp[0] >> 4);
 200
 201         TCHECK2(bp[0], len);
 202         if (vflag) {
 203                 /* Check the IGMP checksum */
 204                 if (in_cksum((const u_short*)bp, len, 0))
 205                         printf(" bad igmp cksum %x!", EXTRACT_16BITS(&bp[2]));
 206         }
 207         return;
 208 trunc:
 209         fputs("[|igmp]", stdout);
 210 }
 211
 212 /*
 213  * print the recorded route in an IP RR, LSRR or SSRR option.
 214  */
 215 static void
 216 ip_printroute(const char *type, register const u_char *cp, u_int length)
 217 {
 218         register u_int ptr = cp[2] - 1;
 219         register u_int len;
 220
 221         printf(" %s{", type);
 222         if ((length + 1) & 3)
 223                 printf(" [bad length %d]", length);
 224         if (ptr < 3 || ((ptr + 1) & 3) || ptr > length + 1)
 225                 printf(" [bad ptr %d]", cp[2]);
 226
 227         type = "";
 228         for (len = 3; len < length; len += 4) {
 229                 if (ptr == len)
 230                         type = "#";
 231                 printf("%s%s", type, ipaddr_string(&cp[len]));
 232                 type = " ";
 233         }
 234         printf("%s}", ptr == len? "#" : "");
 235 }
 236
 237 static void
 238 ip_printts(register const u_char *cp, u_int length)
 239 {
 240         register u_int ptr = cp[2] - 1;
 241         register u_int len;
 242         int hoplen;
 243         char *type;
 244
 245         printf(" TS{");
 246         hoplen = ((cp[3]&0xF) != IPOPT_TS_TSONLY) ? 8 : 4;
 247         if ((length - 4) & (hoplen-1))
 248                 printf("[bad length %d]", length);
 249         if (ptr < 4 || ((ptr - 4) & (hoplen-1)) || ptr > length + 1)
 250                 printf("[bad ptr %d]", cp[2]);
 251         switch (cp[3]&0xF) {
 252         case IPOPT_TS_TSONLY:
 253                 printf("TSONLY");
 254                 break;
 255         case IPOPT_TS_TSANDADDR:
 256                 printf("TS+ADDR");
 257                 break;
 258         case 2:
 259                 printf("PRESPEC2.0");
 260                 break;
 261         case IPOPT_TS_PRESPEC:
 262                 printf("PRESPEC");
 263                 break;
 264         default:
 265                 printf("[bad ts type %d]", cp[3]&0xF);
 266                 goto done;
 267         }
 268
 269         type = " ";
 270         for (len = 4; len < length; len += hoplen) {
 271                 if (ptr == len)
 272                         type = " ^ ";
 273                 printf("%s%d@%s", type, ntohl(*(u_int32_t *)&cp[len+hoplen-4]),
 274                        hoplen!=8 ? "" : ipaddr_string(&cp[len]));
 275                 type = " ";
 276         }
 277
 278 done:
 279         printf("%s", ptr == len ? " ^ " : "");
 280
 281         if (cp[3]>>4)
 282                 printf(" [%d hops not recorded]} ", cp[3]>>4);
 283         else
 284                 printf("}");
 285 }
 286
 287 /*
 288  * print IP options.
 289  */
 290 static void
 291 ip_optprint(register const u_char *cp, u_int length)
 292 {
 293         register u_int len;
 294
 295         for (; length > 0; cp += len, length -= len) {
 296                 int tt = *cp;
 297
 298                 len = (tt == IPOPT_NOP || tt == IPOPT_EOL) ? 1 : cp[1];
 299                 if (len <= 0) {
 300                         printf("[|ip op len %d]", len);
 301                         return;
 302                 }
 303                 if (&cp[1] >= snapend || cp + len > snapend) {
 304                         printf("[|ip]");
 305                         return;
 306                 }
 307                 switch (tt) {
 308
 309                 case IPOPT_EOL:
 310                         printf(" EOL");
 311                         if (length > 1)
 312                                 printf("-%d", length - 1);
 313                         return;
 314
 315                 case IPOPT_NOP:
 316                         printf(" NOP");
 317                         break;
 318
 319                 case IPOPT_TS:
 320                         ip_printts(cp, len);
 321                         break;
 322
 323 #ifndef IPOPT_SECURITY
 324 #define IPOPT_SECURITY 130
 325 #endif /* IPOPT_SECURITY */
 326                 case IPOPT_SECURITY:
 327                         printf(" SECURITY{%d}", len);
 328                         break;
 329
 330                 case IPOPT_RR:
 331                         ip_printroute("RR", cp, len);
 332                         break;
 333
 334                 case IPOPT_SSRR:
 335                         ip_printroute("SSRR", cp, len);
 336                         break;
 337
 338                 case IPOPT_LSRR:
 339                         ip_printroute("LSRR", cp, len);
 340                         break;
 341
 342 #ifndef IPOPT_RA
 343 #define IPOPT_RA 148            /* router alert */
 344 #endif
 345                 case IPOPT_RA:
 346                         printf(" RA");
 347                         if (len != 4)
 348                                 printf("{%d}", len);
 349                         else if (cp[2] || cp[3])
 350                                 printf("%d.%d", cp[2], cp[3]);
 351                         break;
 352
 353                 default:
 354                         printf(" IPOPT-%d{%d}", cp[0], len);
 355                         break;
 356                 }
 357         }
 358 }
 359
 360 /*
 361  * compute an IP header checksum.
 362  * don't modifiy the packet.
 363  */
 364 u_short
 365 in_cksum(const u_short *addr, register int len, u_short csum)
 366 {
 367         int nleft = len;
 368         const u_short *w = addr;
 369         u_short answer;
 370         int sum = csum;
 371
 372         /*
 373          *  Our algorithm is simple, using a 32 bit accumulator (sum),
 374          *  we add sequential 16 bit words to it, and at the end, fold
 375          *  back all the carry bits from the top 16 bits into the lower
 376          *  16 bits.
 377          */
 378         while (nleft > 1)  {
 379                 sum += *w++;
 380                 nleft -= 2;
 381         }
 382         if (nleft == 1)
 383                 sum += htons(*(u_char *)w<<8);
 384
 385         /*
 386          * add back carry outs from top 16 bits to low 16 bits
 387          */
 388         sum = (sum >> 16) + (sum & 0xffff);     /* add hi 16 to low 16 */
 389         sum += (sum >> 16);                     /* add carry */
 390         answer = ~sum;                          /* truncate to 16 bits */
 391         return (answer);
 392 }
 393
 394 /*
 395  * print an IP datagram.
 396  */
 397 void
 398 ip_print(register const u_char *bp, register u_int length)
 399 {
 400         register const struct ip *ip;
 401         register u_int hlen, len, len0, off;
 402         register const u_char *cp;
 403         u_char nh;
 404         int advance;
 405
 406         ip = (const struct ip *)bp;
 407 #ifdef LBL_ALIGN
 408         /*
 409          * If the IP header is not aligned, copy into abuf.
 410          * This will never happen with BPF.  It does happen raw packet
 411          * dumps from -r.
 412          */
 413         if ((long)ip & 3) {
 414                 static u_char *abuf = NULL;
 415                 static int didwarn = 0;
 416
 417                 if (abuf == NULL) {
 418                         abuf = (u_char *)malloc(snaplen);
 419                         if (abuf == NULL)
 420                                 error("ip_print: malloc");
 421                 }
 422                 memcpy((char *)abuf, (char *)ip, min(length, snaplen));
 423                 snapend += abuf - (u_char *)ip;
 424                 packetp = abuf;
 425                 ip = (struct ip *)abuf;
 426                 /* We really want libpcap to give us aligned packets */
 427                 if (!didwarn) {
 428                         warning("compensating for unaligned libpcap packets");
 429                         ++didwarn;
 430                 }
 431         }
 432 #endif
 433         if ((u_char *)(ip + 1) > snapend) {
 434                 printf("[|ip]");
 435                 return;
 436         }
 437         if (length < sizeof (struct ip)) {
 438                 (void)printf("truncated-ip %d", length);
 439                 return;
 440         }
 441         hlen = ip->ip_hl * 4;
 442
 443         len = ntohs(ip->ip_len);
 444         if (length < len)
 445                 (void)printf("truncated-ip - %d bytes missing!",
 446                         len - length);
 447         len -= hlen;
 448         len0 = len;
 449
 450         /*
 451          * If this is fragment zero, hand it to the next higher
 452          * level protocol.
 453          */
 454         off = ntohs(ip->ip_off);
 455         if ((off & 0x1fff) == 0) {
 456                 cp = (const u_char *)ip + hlen;
 457                 nh = ip->ip_p;
 458
 459                 if (nh != IPPROTO_TCP && nh != IPPROTO_UDP) {
 460                         (void)printf("%s > %s: ", ipaddr_string(&ip->ip_src),
 461                                 ipaddr_string(&ip->ip_dst));
 462                 }
 463 again:
 464                 switch (nh) {
 465
 466 #ifndef IPPROTO_AH
 467 #define IPPROTO_AH      51
 468 #endif
 469                 case IPPROTO_AH:
 470                         nh = *cp;
 471                         advance = ah_print(cp, (const u_char *)ip);
 472                         cp += advance;
 473                         len -= advance;
 474                         goto again;
 475
 476 #ifndef IPPROTO_ESP
 477 #define IPPROTO_ESP     50
 478 #endif
 479                 case IPPROTO_ESP:
 480                     {
 481                         int enh;
 482                         advance = esp_print(cp, (const u_char *)ip, &enh);
 483                         cp += advance;
 484                         len -= advance;
 485                         if (enh < 0)
 486                                 break;
 487                         nh = enh & 0xff;
 488                         goto again;
 489                     }
 490
 491 #ifndef IPPROTO_IPCOMP
 492 #define IPPROTO_IPCOMP  108
 493 #endif
 494                 case IPPROTO_IPCOMP:
 495                     {
 496                         int enh;
 497                         advance = ipcomp_print(cp, (const u_char *)ip, &enh);
 498                         cp += advance;
 499                         len -= advance;
 500                         if (enh < 0)
 501                                 break;
 502                         nh = enh & 0xff;
 503                         goto again;
 504                     }
 505
 506                 case IPPROTO_TCP:
 507                         tcp_print(cp, len, (const u_char *)ip);
 508                         break;
 509
 510                 case IPPROTO_UDP:
 511                         udp_print(cp, len, (const u_char *)ip);
 512                         break;
 513
 514                 case IPPROTO_ICMP:
 515                         icmp_print(cp, len, (const u_char *)ip);
 516                         break;
 517
 518 #ifndef IPPROTO_IGRP
 519 #define IPPROTO_IGRP 9
 520 #endif
 521                 case IPPROTO_IGRP:
 522                         igrp_print(cp, len, (const u_char *)ip);
 523                         break;
 524
 525                 case IPPROTO_ND:
 526 #if 0
 527                         (void)printf("%s > %s:", ipaddr_string(&ip->ip_src),
 528                                 ipaddr_string(&ip->ip_dst));
 529 #endif
 530                         (void)printf(" nd %d", len);
 531                         break;
 532
 533                 case IPPROTO_EGP:
 534                         egp_print(cp, len, (const u_char *)ip);
 535                         break;
 536
 537 #ifndef IPPROTO_OSPF
 538 #define IPPROTO_OSPF 89
 539 #endif
 540                 case IPPROTO_OSPF:
 541                         ospf_print(cp, len, (const u_char *)ip);
 542                         break;
 543
 544 #ifndef IPPROTO_IGMP
 545 #define IPPROTO_IGMP 2
 546 #endif
 547                 case IPPROTO_IGMP:
 548                         igmp_print(cp, len, (const u_char *)ip);
 549                         break;
 550
 551                 case 4:
 552                         /* DVMRP multicast tunnel (ip-in-ip encapsulation) */
 553 #if 0
 554                         if (vflag)
 555                                 (void)printf("%s > %s: ",
 556                                              ipaddr_string(&ip->ip_src),
 557                                              ipaddr_string(&ip->ip_dst));
 558 #endif
 559                         ip_print(cp, len);
 560                         if (! vflag) {
 561                                 printf(" (ipip)");
 562                                 return;
 563                         }
 564                         break;
 565
 566 #ifdef INET6
 567 #ifndef IP6PROTO_ENCAP
 568 #define IP6PROTO_ENCAP 41
 569 #endif
 570                 case IP6PROTO_ENCAP:
 571                         /* ip6-in-ip encapsulation */
 572 #if 0
 573                         if (vflag)
 574                                 (void)printf("%s > %s: ",
 575                                              ipaddr_string(&ip->ip_src),
 576                                              ipaddr_string(&ip->ip_dst));
 577 #endif
 578                         ip6_print(cp, len);
 579                         if (! vflag) {
 580                                 printf(" (encap)");
 581                                 return;
 582                         }
 583                         break;
 584 #endif /*INET6*/
 585
 586
 587 #ifndef IPPROTO_GRE
 588 #define IPPROTO_GRE 47
 589 #endif
 590                 case IPPROTO_GRE:
 591                         if (vflag)
 592                                 (void)printf("gre %s > %s: ",
 593                                              ipaddr_string(&ip->ip_src),
 594                                              ipaddr_string(&ip->ip_dst));
 595                         /* do it */
 596                         gre_print(cp, len);
 597                         if (! vflag) {
 598                                 printf(" (gre encap)");
 599                                 return;
 600                         }
 601                         break;
 602
 603 #ifndef IPPROTO_MOBILE
 604 #define IPPROTO_MOBILE 55
 605 #endif
 606                 case IPPROTO_MOBILE:
 607                         if (vflag)
 608                                 (void)printf("mobile %s > %s: ",
 609                                              ipaddr_string(&ip->ip_src),
 610                                              ipaddr_string(&ip->ip_dst));
 611                         mobile_print(cp, len);
 612                         if (! vflag) {
 613                                 printf(" (mobile encap)");
 614                                 return;
 615                         }
 616                         break;
 617
 618 #ifndef IPPROTO_PIM
 619 #define IPPROTO_PIM     103
 620 #endif
 621                 case IPPROTO_PIM:
 622                         pim_print(cp, len);
 623                         break;
 624
 625                 default:
 626 #if 0
 627                         (void)printf("%s > %s:", ipaddr_string(&ip->ip_src),
 628                                 ipaddr_string(&ip->ip_dst));
 629 #endif
 630                         (void)printf(" ip-proto-%d %d", nh, len);
 631                         break;
 632                 }
 633         }
 634
 635         /*
 636          * for fragmented datagrams, print id:size@offset.  On all
 637          * but the last stick a "+".  For unfragmented datagrams, note
 638          * the don't fragment flag.
 639          */
 640         len = len0;     /* get the original length */
 641         if (off & 0x3fff) {
 642                 /*
 643                  * if this isn't the first frag, we're missing the
 644                  * next level protocol header.  print the ip addr.
 645                  */
 646                 if (off & 0x1fff)
 647                         (void)printf("%s > %s:", ipaddr_string(&ip->ip_src),
 648                                       ipaddr_string(&ip->ip_dst));
 649 #ifndef IP_MF
 650 #define IP_MF 0x2000
 651 #endif /* IP_MF */
 652 #ifndef IP_DF
 653 #define IP_DF 0x4000
 654 #endif /* IP_DF */
 655                 (void)printf(" (frag %d:%u@%d%s)", ntohs(ip->ip_id), len,
 656                         (off & 0x1fff) * 8,
 657                         (off & IP_MF)? "+" : "");
 658
 659         } else if (off & IP_DF)
 660                 (void)printf(" (DF)");
 661
 662         if (ip->ip_tos) {
 663                 (void)printf(" [tos 0x%x", (int)ip->ip_tos);
 664                 /* ECN bits */
 665                 if (ip->ip_tos&0x02) {
 666                         (void)printf(",ECT");
 667                         if (ip->ip_tos&0x01)
 668                                 (void)printf(",CE");
 669                 }
 670                 (void)printf("] ");
 671         }
 672
 673         if (ip->ip_ttl <= 1)
 674                 (void)printf(" [ttl %d]", (int)ip->ip_ttl);
 675
 676         if (vflag) {
 677                 int sum;
 678                 char *sep = "";
 679
 680                 printf(" (");
 681                 if (ip->ip_ttl > 1) {
 682                         (void)printf("%sttl %d", sep, (int)ip->ip_ttl);
 683                         sep = ", ";
 684                 }
 685                 if ((off & 0x3fff) == 0) {
 686                         (void)printf("%sid %d", sep, (int)ntohs(ip->ip_id));
 687                         sep = ", ";
 688                 }
 689                 if ((u_char *)ip + hlen <= snapend) {
 690                         sum = in_cksum((const u_short *)ip, hlen, 0);
 691                         if (sum != 0) {
 692                                 (void)printf("%sbad cksum %x!", sep,
 693                                              ntohs(ip->ip_sum));
 694                                 sep = ", ";
 695                         }
 696                 }
 697                 if ((hlen -= sizeof(struct ip)) > 0) {
 698                         (void)printf("%soptlen=%d", sep, hlen);
 699                         ip_optprint((u_char *)(ip + 1), hlen);
 700                 }
 701                 printf(")");
 702         }
 703 }