xref: /freebsd/contrib/tcpdump/print-ip.c (revision 1e413cf93298b5b97441a21d9a50fdcd0ee9945e)
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  * $FreeBSD$
22  */
23 
24 #ifndef lint
25 static const char rcsid[] _U_ =
26     "@(#) $Header: /tcpdump/master/tcpdump/print-ip.c,v 1.149.2.9 2007/09/14 01:30:02 guy Exp $ (LBL)";
27 #endif
28 
29 #ifdef HAVE_CONFIG_H
30 #include "config.h"
31 #endif
32 
33 #include <tcpdump-stdinc.h>
34 
35 #include <stdio.h>
36 #include <stdlib.h>
37 #include <string.h>
38 
39 #include "addrtoname.h"
40 #include "interface.h"
41 #include "extract.h"			/* must come after interface.h */
42 
43 #include "ip.h"
44 #include "ipproto.h"
45 
46 struct tok ip_option_values[] = {
47     { IPOPT_EOL, "EOL" },
48     { IPOPT_NOP, "NOP" },
49     { IPOPT_TS, "timestamp" },
50     { IPOPT_SECURITY, "security" },
51     { IPOPT_RR, "RR" },
52     { IPOPT_SSRR, "SSRR" },
53     { IPOPT_LSRR, "LSRR" },
54     { IPOPT_RA, "RA" },
55     { IPOPT_RFC1393, "traceroute" },
56     { 0, NULL }
57 };
58 
59 /*
60  * print the recorded route in an IP RR, LSRR or SSRR option.
61  */
62 static void
63 ip_printroute(register const u_char *cp, u_int length)
64 {
65 	register u_int ptr;
66 	register u_int len;
67 
68 	if (length < 3) {
69 		printf(" [bad length %u]", length);
70 		return;
71 	}
72 	if ((length + 1) & 3)
73 		printf(" [bad length %u]", length);
74 	ptr = cp[2] - 1;
75 	if (ptr < 3 || ((ptr + 1) & 3) || ptr > length + 1)
76 		printf(" [bad ptr %u]", cp[2]);
77 
78 	for (len = 3; len < length; len += 4) {
79 		printf(" %s", ipaddr_string(&cp[len]));
80                 if (ptr > len)
81                         printf(",");
82 	}
83 }
84 
85 /*
86  * If source-routing is present and valid, return the final destination.
87  * Otherwise, return IP destination.
88  *
89  * This is used for UDP and TCP pseudo-header in the checksum
90  * calculation.
91  */
92 u_int32_t
93 ip_finddst(const struct ip *ip)
94 {
95 	int length;
96 	int len;
97 	const u_char *cp;
98 	u_int32_t retval;
99 
100 	cp = (const u_char *)(ip + 1);
101 	length = (IP_HL(ip) << 2) - sizeof(struct ip);
102 
103 	for (; length > 0; cp += len, length -= len) {
104 		int tt;
105 
106 		TCHECK(*cp);
107 		tt = *cp;
108 		if (tt == IPOPT_EOL)
109 			break;
110 		else if (tt == IPOPT_NOP)
111 			len = 1;
112 		else {
113 			TCHECK(cp[1]);
114 			len = cp[1];
115 			if (len < 2)
116 				break;
117 		}
118 		TCHECK2(*cp, len);
119 		switch (tt) {
120 
121 		case IPOPT_SSRR:
122 		case IPOPT_LSRR:
123 			if (len < 7)
124 				break;
125 			memcpy(&retval, cp + len - 4, 4);
126 			return retval;
127 		}
128 	}
129 trunc:
130 	memcpy(&retval, &ip->ip_dst.s_addr, sizeof(u_int32_t));
131 	return retval;
132 }
133 
134 static void
135 ip_printts(register const u_char *cp, u_int length)
136 {
137 	register u_int ptr;
138 	register u_int len;
139 	int hoplen;
140 	const char *type;
141 
142 	if (length < 4) {
143 		printf("[bad length %u]", length);
144 		return;
145 	}
146 	printf(" TS{");
147 	hoplen = ((cp[3]&0xF) != IPOPT_TS_TSONLY) ? 8 : 4;
148 	if ((length - 4) & (hoplen-1))
149 		printf("[bad length %u]", length);
150 	ptr = cp[2] - 1;
151 	len = 0;
152 	if (ptr < 4 || ((ptr - 4) & (hoplen-1)) || ptr > length + 1)
153 		printf("[bad ptr %u]", cp[2]);
154 	switch (cp[3]&0xF) {
155 	case IPOPT_TS_TSONLY:
156 		printf("TSONLY");
157 		break;
158 	case IPOPT_TS_TSANDADDR:
159 		printf("TS+ADDR");
160 		break;
161 	/*
162 	 * prespecified should really be 3, but some ones might send 2
163 	 * instead, and the IPOPT_TS_PRESPEC constant can apparently
164 	 * have both values, so we have to hard-code it here.
165 	 */
166 
167 	case 2:
168 		printf("PRESPEC2.0");
169 		break;
170 	case 3:			/* IPOPT_TS_PRESPEC */
171 		printf("PRESPEC");
172 		break;
173 	default:
174 		printf("[bad ts type %d]", cp[3]&0xF);
175 		goto done;
176 	}
177 
178 	type = " ";
179 	for (len = 4; len < length; len += hoplen) {
180 		if (ptr == len)
181 			type = " ^ ";
182 		printf("%s%d@%s", type, EXTRACT_32BITS(&cp[len+hoplen-4]),
183 		       hoplen!=8 ? "" : ipaddr_string(&cp[len]));
184 		type = " ";
185 	}
186 
187 done:
188 	printf("%s", ptr == len ? " ^ " : "");
189 
190 	if (cp[3]>>4)
191 		printf(" [%d hops not recorded]} ", cp[3]>>4);
192 	else
193 		printf("}");
194 }
195 
196 /*
197  * print IP options.
198  */
199 static void
200 ip_optprint(register const u_char *cp, u_int length)
201 {
202 	register u_int option_len;
203 	const char *sep = "";
204 
205 	for (; length > 0; cp += option_len, length -= option_len) {
206 		u_int option_code;
207 
208 		printf("%s", sep);
209 		sep = ",";
210 
211 		TCHECK(*cp);
212 		option_code = *cp;
213 
214                 printf("%s",
215                         tok2str(ip_option_values,"unknown %u",option_code));
216 
217 		if (option_code == IPOPT_NOP ||
218                     option_code == IPOPT_EOL)
219 			option_len = 1;
220 
221 		else {
222 			TCHECK(cp[1]);
223 			option_len = cp[1];
224 			if (option_len < 2) {
225 		                printf(" [bad length %u]", option_len);
226 				return;
227 			}
228 		}
229 
230 		if (option_len > length) {
231 	                printf(" [bad length %u]", option_len);
232 			return;
233 		}
234 
235                 TCHECK2(*cp, option_len);
236 
237 		switch (option_code) {
238 		case IPOPT_EOL:
239 			return;
240 
241 		case IPOPT_TS:
242 			ip_printts(cp, option_len);
243 			break;
244 
245 		case IPOPT_RR:       /* fall through */
246 		case IPOPT_SSRR:
247 		case IPOPT_LSRR:
248 			ip_printroute(cp, option_len);
249 			break;
250 
251 		case IPOPT_RA:
252 			if (option_len < 4) {
253 				printf(" [bad length %u]", option_len);
254 				break;
255 			}
256                         TCHECK(cp[3]);
257                         if (EXTRACT_16BITS(&cp[2]) != 0)
258                             printf(" value %u", EXTRACT_16BITS(&cp[2]));
259 			break;
260 
261 		case IPOPT_NOP:       /* nothing to print - fall through */
262 		case IPOPT_SECURITY:
263 		default:
264 			break;
265 		}
266 	}
267 	return;
268 
269 trunc:
270 	printf("[|ip]");
271 }
272 
273 /*
274  * compute an IP header checksum.
275  * don't modifiy the packet.
276  */
277 u_short
278 in_cksum(const u_short *addr, register u_int len, int csum)
279 {
280 	int nleft = len;
281 	const u_short *w = addr;
282 	u_short answer;
283 	int sum = csum;
284 
285 	/*
286 	 *  Our algorithm is simple, using a 32 bit accumulator (sum),
287 	 *  we add sequential 16 bit words to it, and at the end, fold
288 	 *  back all the carry bits from the top 16 bits into the lower
289 	 *  16 bits.
290 	 */
291 	while (nleft > 1)  {
292 		sum += *w++;
293 		nleft -= 2;
294 	}
295 	if (nleft == 1)
296 		sum += htons(*(u_char *)w<<8);
297 
298 	/*
299 	 * add back carry outs from top 16 bits to low 16 bits
300 	 */
301 	sum = (sum >> 16) + (sum & 0xffff);	/* add hi 16 to low 16 */
302 	sum += (sum >> 16);			/* add carry */
303 	answer = ~sum;				/* truncate to 16 bits */
304 	return (answer);
305 }
306 
307 /*
308  * Given the host-byte-order value of the checksum field in a packet
309  * header, and the network-byte-order computed checksum of the data
310  * that the checksum covers (including the checksum itself), compute
311  * what the checksum field *should* have been.
312  */
313 u_int16_t
314 in_cksum_shouldbe(u_int16_t sum, u_int16_t computed_sum)
315 {
316 	u_int32_t shouldbe;
317 
318 	/*
319 	 * The value that should have gone into the checksum field
320 	 * is the negative of the value gotten by summing up everything
321 	 * *but* the checksum field.
322 	 *
323 	 * We can compute that by subtracting the value of the checksum
324 	 * field from the sum of all the data in the packet, and then
325 	 * computing the negative of that value.
326 	 *
327 	 * "sum" is the value of the checksum field, and "computed_sum"
328 	 * is the negative of the sum of all the data in the packets,
329 	 * so that's -(-computed_sum - sum), or (sum + computed_sum).
330 	 *
331 	 * All the arithmetic in question is one's complement, so the
332 	 * addition must include an end-around carry; we do this by
333 	 * doing the arithmetic in 32 bits (with no sign-extension),
334 	 * and then adding the upper 16 bits of the sum, which contain
335 	 * the carry, to the lower 16 bits of the sum, and then do it
336 	 * again in case *that* sum produced a carry.
337 	 *
338 	 * As RFC 1071 notes, the checksum can be computed without
339 	 * byte-swapping the 16-bit words; summing 16-bit words
340 	 * on a big-endian machine gives a big-endian checksum, which
341 	 * can be directly stuffed into the big-endian checksum fields
342 	 * in protocol headers, and summing words on a little-endian
343 	 * machine gives a little-endian checksum, which must be
344 	 * byte-swapped before being stuffed into a big-endian checksum
345 	 * field.
346 	 *
347 	 * "computed_sum" is a network-byte-order value, so we must put
348 	 * it in host byte order before subtracting it from the
349 	 * host-byte-order value from the header; the adjusted checksum
350 	 * will be in host byte order, which is what we'll return.
351 	 */
352 	shouldbe = sum;
353 	shouldbe += ntohs(computed_sum);
354 	shouldbe = (shouldbe & 0xFFFF) + (shouldbe >> 16);
355 	shouldbe = (shouldbe & 0xFFFF) + (shouldbe >> 16);
356 	return shouldbe;
357 }
358 
359 #define IP_RES 0x8000
360 
361 static struct tok ip_frag_values[] = {
362         { IP_MF,        "+" },
363         { IP_DF,        "DF" },
364 	{ IP_RES,       "rsvd" }, /* The RFC3514 evil ;-) bit */
365         { 0,            NULL }
366 };
367 
368 struct ip_print_demux_state {
369 	const struct ip *ip;
370 	const u_char *cp;
371 	u_int   len, off;
372 	u_char  nh;
373 	int     advance;
374 };
375 
376 static void
377 ip_print_demux(netdissect_options *ndo,
378 	       struct ip_print_demux_state *ipds)
379 {
380 	struct protoent *proto;
381 
382 again:
383 	switch (ipds->nh) {
384 
385 	case IPPROTO_AH:
386 		ipds->nh = *ipds->cp;
387 		ipds->advance = ah_print(ipds->cp);
388 		if (ipds->advance <= 0)
389 			break;
390 		ipds->cp += ipds->advance;
391 		ipds->len -= ipds->advance;
392 		goto again;
393 
394 	case IPPROTO_ESP:
395 	{
396 		int enh, padlen;
397 		ipds->advance = esp_print(ndo, ipds->cp, ipds->len,
398 				    (const u_char *)ipds->ip,
399 				    &enh, &padlen);
400 		if (ipds->advance <= 0)
401 			break;
402 		ipds->cp += ipds->advance;
403 		ipds->len -= ipds->advance + padlen;
404 		ipds->nh = enh & 0xff;
405 		goto again;
406 	}
407 
408 	case IPPROTO_IPCOMP:
409 	{
410 		int enh;
411 		ipds->advance = ipcomp_print(ipds->cp, &enh);
412 		if (ipds->advance <= 0)
413 			break;
414 		ipds->cp += ipds->advance;
415 		ipds->len -= ipds->advance;
416 		ipds->nh = enh & 0xff;
417 		goto again;
418 	}
419 
420 	case IPPROTO_SCTP:
421 		sctp_print(ipds->cp, (const u_char *)ipds->ip, ipds->len);
422 		break;
423 
424 	case IPPROTO_DCCP:
425 		dccp_print(ipds->cp, (const u_char *)ipds->ip, ipds->len);
426 		break;
427 
428 	case IPPROTO_TCP:
429 		/* pass on the MF bit plus the offset to detect fragments */
430 		tcp_print(ipds->cp, ipds->len, (const u_char *)ipds->ip,
431 			  ipds->off & (IP_MF|IP_OFFMASK));
432 		break;
433 
434 	case IPPROTO_UDP:
435 		/* pass on the MF bit plus the offset to detect fragments */
436 		udp_print(ipds->cp, ipds->len, (const u_char *)ipds->ip,
437 			  ipds->off & (IP_MF|IP_OFFMASK));
438 		break;
439 
440 	case IPPROTO_ICMP:
441 		/* pass on the MF bit plus the offset to detect fragments */
442 		icmp_print(ipds->cp, ipds->len, (const u_char *)ipds->ip,
443 			   ipds->off & (IP_MF|IP_OFFMASK));
444 		break;
445 
446 	case IPPROTO_PIGP:
447 		/*
448 		 * XXX - the current IANA protocol number assignments
449 		 * page lists 9 as "any private interior gateway
450 		 * (used by Cisco for their IGRP)" and 88 as
451 		 * "EIGRP" from Cisco.
452 		 *
453 		 * Recent BSD <netinet/in.h> headers define
454 		 * IP_PROTO_PIGP as 9 and IP_PROTO_IGRP as 88.
455 		 * We define IP_PROTO_PIGP as 9 and
456 		 * IP_PROTO_EIGRP as 88; those names better
457 		 * match was the current protocol number
458 		 * assignments say.
459 		 */
460 		igrp_print(ipds->cp, ipds->len, (const u_char *)ipds->ip);
461 		break;
462 
463 	case IPPROTO_EIGRP:
464 		eigrp_print(ipds->cp, ipds->len);
465 		break;
466 
467 	case IPPROTO_ND:
468 		ND_PRINT((ndo, " nd %d", ipds->len));
469 		break;
470 
471 	case IPPROTO_EGP:
472 		egp_print(ipds->cp, ipds->len);
473 		break;
474 
475 	case IPPROTO_OSPF:
476 		ospf_print(ipds->cp, ipds->len, (const u_char *)ipds->ip);
477 		break;
478 
479 	case IPPROTO_IGMP:
480 		igmp_print(ipds->cp, ipds->len);
481 		break;
482 
483 	case IPPROTO_IPV4:
484 		/* DVMRP multicast tunnel (ip-in-ip encapsulation) */
485 		ip_print(gndo, ipds->cp, ipds->len);
486 		if (! vflag) {
487 			ND_PRINT((ndo, " (ipip-proto-4)"));
488 			return;
489 		}
490 		break;
491 
492 #ifdef INET6
493 	case IPPROTO_IPV6:
494 		/* ip6-in-ip encapsulation */
495 		ip6_print(ipds->cp, ipds->len);
496 		break;
497 #endif /*INET6*/
498 
499 	case IPPROTO_RSVP:
500 		rsvp_print(ipds->cp, ipds->len);
501 		break;
502 
503 	case IPPROTO_GRE:
504 		/* do it */
505 		gre_print(ipds->cp, ipds->len);
506 		break;
507 
508 	case IPPROTO_MOBILE:
509 		mobile_print(ipds->cp, ipds->len);
510 		break;
511 
512 	case IPPROTO_PIM:
513 		pim_print(ipds->cp,  ipds->len);
514 		break;
515 
516 	case IPPROTO_VRRP:
517 		vrrp_print(ipds->cp, ipds->len, ipds->ip->ip_ttl);
518 		break;
519 
520 	case IPPROTO_PGM:
521 		pgm_print(ipds->cp, ipds->len, (const u_char *)ipds->ip);
522 		break;
523 
524 	default:
525 		if ((proto = getprotobynumber(ipds->nh)) != NULL)
526 			ND_PRINT((ndo, " %s", proto->p_name));
527 		else
528 			ND_PRINT((ndo, " ip-proto-%d", ipds->nh));
529 		ND_PRINT((ndo, " %d", ipds->len));
530 		break;
531 	}
532 }
533 
534 void
535 ip_print_inner(netdissect_options *ndo,
536 	       const u_char *bp,
537 	       u_int length, u_int nh,
538 	       const u_char *bp2)
539 {
540 	struct ip_print_demux_state  ipd;
541 
542 	ipd.ip = (const struct ip *)bp2;
543 	ipd.cp = bp;
544 	ipd.len  = length;
545 	ipd.off  = 0;
546 	ipd.nh   = nh;
547 	ipd.advance = 0;
548 
549 	ip_print_demux(ndo, &ipd);
550 }
551 
552 
553 /*
554  * print an IP datagram.
555  */
556 void
557 ip_print(netdissect_options *ndo,
558 	 const u_char *bp,
559 	 u_int length)
560 {
561 	struct ip_print_demux_state  ipd;
562 	struct ip_print_demux_state *ipds=&ipd;
563 	const u_char *ipend;
564 	u_int hlen;
565 	u_int16_t sum, ip_sum;
566 	struct protoent *proto;
567 
568 	ipds->ip = (const struct ip *)bp;
569 	if (IP_V(ipds->ip) != 4) { /* print version if != 4 */
570 	    printf("IP%u ", IP_V(ipds->ip));
571 	    if (IP_V(ipds->ip) == 6)
572 		printf(", wrong link-layer encapsulation");
573 	}
574         else if (!eflag)
575 	    printf("IP ");
576 
577 	if ((u_char *)(ipds->ip + 1) > snapend) {
578 		printf("[|ip]");
579 		return;
580 	}
581 	if (length < sizeof (struct ip)) {
582 		(void)printf("truncated-ip %u", length);
583 		return;
584 	}
585 	hlen = IP_HL(ipds->ip) * 4;
586 	if (hlen < sizeof (struct ip)) {
587 		(void)printf("bad-hlen %u", hlen);
588 		return;
589 	}
590 
591 	ipds->len = EXTRACT_16BITS(&ipds->ip->ip_len);
592 	if (length < ipds->len)
593 		(void)printf("truncated-ip - %u bytes missing! ",
594 			ipds->len - length);
595 	if (ipds->len < hlen) {
596 #ifdef GUESS_TSO
597             if (ipds->len) {
598                 (void)printf("bad-len %u", ipds->len);
599                 return;
600             }
601             else {
602                 /* we guess that it is a TSO send */
603                 ipds->len = length;
604             }
605 #else
606             (void)printf("bad-len %u", ipds->len);
607             return;
608 #endif /* GUESS_TSO */
609 	}
610 
611 	/*
612 	 * Cut off the snapshot length to the end of the IP payload.
613 	 */
614 	ipend = bp + ipds->len;
615 	if (ipend < snapend)
616 		snapend = ipend;
617 
618 	ipds->len -= hlen;
619 
620 	ipds->off = EXTRACT_16BITS(&ipds->ip->ip_off);
621 
622         if (vflag) {
623             (void)printf("(tos 0x%x", (int)ipds->ip->ip_tos);
624             /* ECN bits */
625             if (ipds->ip->ip_tos & 0x03) {
626                 switch (ipds->ip->ip_tos & 0x03) {
627                 case 1:
628                     (void)printf(",ECT(1)");
629                     break;
630                 case 2:
631                     (void)printf(",ECT(0)");
632                     break;
633                 case 3:
634                     (void)printf(",CE");
635                 }
636             }
637 
638             if (ipds->ip->ip_ttl >= 1)
639                 (void)printf(", ttl %u", ipds->ip->ip_ttl);
640 
641 	    /*
642 	     * for the firewall guys, print id, offset.
643              * On all but the last stick a "+" in the flags portion.
644 	     * For unfragmented datagrams, note the don't fragment flag.
645 	     */
646 
647 	    (void)printf(", id %u, offset %u, flags [%s], proto %s (%u)",
648                          EXTRACT_16BITS(&ipds->ip->ip_id),
649                          (ipds->off & 0x1fff) * 8,
650                          bittok2str(ip_frag_values, "none", ipds->off&0xe000),
651                          tok2str(ipproto_values,"unknown",ipds->ip->ip_p),
652                          ipds->ip->ip_p);
653 
654             (void)printf(", length %u", EXTRACT_16BITS(&ipds->ip->ip_len));
655 
656             if ((hlen - sizeof(struct ip)) > 0) {
657                 printf(", options (");
658                 ip_optprint((u_char *)(ipds->ip + 1), hlen - sizeof(struct ip));
659                 printf(")");
660             }
661 
662 	    if ((u_char *)ipds->ip + hlen <= snapend) {
663 	        sum = in_cksum((const u_short *)ipds->ip, hlen, 0);
664 		if (sum != 0) {
665 		    ip_sum = EXTRACT_16BITS(&ipds->ip->ip_sum);
666 		    (void)printf(", bad cksum %x (->%x)!", ip_sum,
667 			     in_cksum_shouldbe(ip_sum, sum));
668 		}
669 	    }
670 
671             printf(") ");
672 	}
673 
674 	/*
675 	 * If this is fragment zero, hand it to the next higher
676 	 * level protocol.
677 	 */
678 	if ((ipds->off & 0x1fff) == 0) {
679 		ipds->cp = (const u_char *)ipds->ip + hlen;
680 		ipds->nh = ipds->ip->ip_p;
681 
682 		if (ipds->nh != IPPROTO_TCP && ipds->nh != IPPROTO_UDP &&
683 		    ipds->nh != IPPROTO_SCTP && ipds->nh != IPPROTO_DCCP) {
684 			(void)printf("%s > %s: ",
685 				     ipaddr_string(&ipds->ip->ip_src),
686 				     ipaddr_string(&ipds->ip->ip_dst));
687 		}
688 		ip_print_demux(ndo, ipds);
689 	} else {
690 	    /* Ultra quiet now means that all this stuff should be suppressed */
691 	    if (qflag > 1) return;
692 
693 	    /*
694 	     * if this isn't the first frag, we're missing the
695 	     * next level protocol header.  print the ip addr
696 	     * and the protocol.
697 	     */
698 	    if (ipds->off & 0x1fff) {
699 	        (void)printf("%s > %s:", ipaddr_string(&ipds->ip->ip_src),
700 			     ipaddr_string(&ipds->ip->ip_dst));
701 		if ((proto = getprotobynumber(ipds->ip->ip_p)) != NULL)
702 		    (void)printf(" %s", proto->p_name);
703 		else
704 		    (void)printf(" ip-proto-%d", ipds->ip->ip_p);
705 	    }
706 	}
707 }
708 
709 void
710 ipN_print(register const u_char *bp, register u_int length)
711 {
712 	struct ip *ip, hdr;
713 
714 	ip = (struct ip *)bp;
715 	if (length < 4) {
716 		(void)printf("truncated-ip %d", length);
717 		return;
718 	}
719 	memcpy (&hdr, (char *)ip, 4);
720 	switch (IP_V(&hdr)) {
721 	case 4:
722 		ip_print (gndo, bp, length);
723 		return;
724 #ifdef INET6
725 	case 6:
726 		ip6_print (bp, length);
727 		return;
728 #endif
729 	default:
730 		(void)printf("unknown ip %d", IP_V(&hdr));
731 		return;
732 	}
733 }
734 
735 /*
736  * Local Variables:
737  * c-style: whitesmith
738  * c-basic-offset: 8
739  * End:
740  */
741 
742 
743