print-ip.c - platform/external/tcpdump - Git at Google

 /*
  * Copyright (c) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997
  *	The Regents of the University of California.  All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that: (1) source code distributions
  * retain the above copyright notice and this paragraph in its entirety, (2)
  * distributions including binary code include the above copyright notice and
  * this paragraph in its entirety in the documentation or other materials
  * provided with the distribution, and (3) all advertising materials mentioning
  * features or use of this software display the following acknowledgement:
  * ``This product includes software developed by the University of California,
  * Lawrence Berkeley Laboratory and its contributors.'' Neither the name of
  * the University nor the names of its contributors may be used to endorse
  * or promote products derived from this software without specific prior
  * written permission.
  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
  * WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
  * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
  */

 #ifndef lint
 static const char rcsid[] =
     "@(#) $Header: /tcpdump/master/tcpdump/print-ip.c,v 1.111 2002-08-01 08:53:10 risso Exp $ (LBL)";
 #endif

 #ifdef HAVE_CONFIG_H
 #include "config.h"
 #endif

 #include <tcpdump-stdinc.h>

 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>

 #include "addrtoname.h"
 #include "interface.h"
 #include "extract.h"			/* must come after interface.h */

 #include "ip.h"

 /* Compatibility */
 #ifndef	IPPROTO_ND
 #define	IPPROTO_ND	77
 #endif

 /*
  * print the recorded route in an IP RR, LSRR or SSRR option.
  */
 static void
 ip_printroute(const char *type, register const u_char *cp, u_int length)
 {
 	register u_int ptr = cp[2] - 1;
 	register u_int len;

 	printf(" %s{", type);
 	if ((length + 1) & 3)
 		printf(" [bad length %d]", length);
 	if (ptr < 3 || ((ptr + 1) & 3) || ptr > length + 1)
 		printf(" [bad ptr %d]", cp[2]);

 	type = "";
 	for (len = 3; len < length; len += 4) {
 		if (ptr == len)
 			type = "#";
 		printf("%s%s", type, ipaddr_string(&cp[len]));
 		type = " ";
 	}
 	printf("%s}", ptr == len? "#" : "");
 }

 /*
  * If source-routing is present, return the final destination.
  * Otherwise, return IP destination.
  *
  * This is used for UDP and TCP pseudo-header in the checksum
  * calculation.
  */
 u_int32_t
 ip_finddst(const struct ip *ip)
 {
 	int length;
 	int len;
 	const u_char *cp;
 	u_int32_t retval;

 	cp = (const u_char *)(ip + 1);
 	length = (IP_HL(ip) << 2) - sizeof(struct ip);

 	for (; length > 0; cp += len, length -= len) {
 		int tt = *cp;

 		if (tt == IPOPT_NOP || tt == IPOPT_EOL)
 			len = 1;
 		else {
 			if (&cp[1] >= snapend) {
 				return 0;
 			}
 			len = cp[1];
 		}
 		if (len <= 0) {
 			return 0;
 		}
 		if (&cp[1] >= snapend || cp + len > snapend) {
 			return 0;
 		}
 		switch (tt) {

 		case IPOPT_SSRR:
 		case IPOPT_LSRR:
 			memcpy(&retval, cp + len - 4, 4);
 			return retval;
 		}
 	}
 	return ip->ip_dst.s_addr;
 }

 static void
 ip_printts(register const u_char *cp, u_int length)
 {
 	register u_int ptr = cp[2] - 1;
 	register u_int len = 0;
 	int hoplen;
 	char *type;

 	printf(" TS{");
 	hoplen = ((cp[3]&0xF) != IPOPT_TS_TSONLY) ? 8 : 4;
 	if ((length - 4) & (hoplen-1))
 		printf("[bad length %d]", length);
 	if (ptr < 4 || ((ptr - 4) & (hoplen-1)) || ptr > length + 1)
 		printf("[bad ptr %d]", cp[2]);
 	switch (cp[3]&0xF) {
 	case IPOPT_TS_TSONLY:
 		printf("TSONLY");
 		break;
 	case IPOPT_TS_TSANDADDR:
 		printf("TS+ADDR");
 		break;
 	/*
 	 * prespecified should really be 3, but some ones might send 2
 	 * instead, and the IPOPT_TS_PRESPEC constant can apparently
 	 * have both values, so we have to hard-code it here.
 	 */

 	case 2:
 		printf("PRESPEC2.0");
 		break;
 	case 3:			/* IPOPT_TS_PRESPEC */
 		printf("PRESPEC");
 		break;
 	default:
 		printf("[bad ts type %d]", cp[3]&0xF);
 		goto done;
 	}

 	type = " ";
 	for (len = 4; len < length; len += hoplen) {
 		if (ptr == len)
 			type = " ^ ";
 		printf("%s%d@%s", type, EXTRACT_32BITS(&cp[len+hoplen-4]),
 		       hoplen!=8 ? "" : ipaddr_string(&cp[len]));
 		type = " ";
 	}

 done:
 	printf("%s", ptr == len ? " ^ " : "");

 	if (cp[3]>>4)
 		printf(" [%d hops not recorded]} ", cp[3]>>4);
 	else
 		printf("}");
 }

 /*
  * print IP options.
  */
 static void
 ip_optprint(register const u_char *cp, u_int length)
 {
 	register u_int len;

 	for (; length > 0; cp += len, length -= len) {
 		int tt = *cp;

 		if (tt == IPOPT_NOP || tt == IPOPT_EOL)
 			len = 1;
 		else {
 			if (&cp[1] >= snapend) {
 				printf("[|ip]");
 				return;
 			}
 			len = cp[1];
 		}
 		if (len <= 0) {
 			printf("[|ip op len %d]", len);
 			return;
 		}
 		if (&cp[1] >= snapend || cp + len > snapend) {
 			printf("[|ip]");
 			return;
 		}
 		switch (tt) {

 		case IPOPT_EOL:
 			printf(" EOL");
 			if (length > 1)
 				printf("-%d", length - 1);
 			return;

 		case IPOPT_NOP:
 			printf(" NOP");
 			break;

 		case IPOPT_TS:
 			ip_printts(cp, len);
 			break;

 #ifndef IPOPT_SECURITY
 #define IPOPT_SECURITY 130
 #endif /* IPOPT_SECURITY */
 		case IPOPT_SECURITY:
 			printf(" SECURITY{%d}", len);
 			break;

 		case IPOPT_RR:
 			ip_printroute("RR", cp, len);
 			break;

 		case IPOPT_SSRR:
 			ip_printroute("SSRR", cp, len);
 			break;

 		case IPOPT_LSRR:
 			ip_printroute("LSRR", cp, len);
 			break;

 #ifndef IPOPT_RA
 #define IPOPT_RA 148		/* router alert */
 #endif
 		case IPOPT_RA:
 			printf(" RA");
 			if (len != 4)
 				printf("{%d}", len);
 			else if (cp[2] || cp[3])
 				printf("%d.%d", cp[2], cp[3]);
 			break;

 		default:
 			printf(" IPOPT-%d{%d}", cp[0], len);
 			break;
 		}
 	}
 }

 /*
  * compute an IP header checksum.
  * don't modifiy the packet.
  */
 u_short
 in_cksum(const u_short *addr, register u_int len, int csum)
 {
 	int nleft = len;
 	const u_short *w = addr;
 	u_short answer;
 	int sum = csum;

 	/*
 	 *  Our algorithm is simple, using a 32 bit accumulator (sum),
 	 *  we add sequential 16 bit words to it, and at the end, fold
 	 *  back all the carry bits from the top 16 bits into the lower
 	 *  16 bits.
 	 */
 	while (nleft > 1)  {
 		sum += *w++;
 		nleft -= 2;
 	}
 	if (nleft == 1)
 		sum += htons(*(u_char *)w<<8);

 	/*
 	 * add back carry outs from top 16 bits to low 16 bits
 	 */
 	sum = (sum >> 16) + (sum & 0xffff);	/* add hi 16 to low 16 */
 	sum += (sum >> 16);			/* add carry */
 	answer = ~sum;				/* truncate to 16 bits */
 	return (answer);
 }

 /*
  * Given the host-byte-order value of the checksum field in a packet
  * header, and the network-byte-order computed checksum of the data
  * that the checksum covers (including the checksum itself), compute
  * what the checksum field *should* have been.
  */
 u_int16_t
 in_cksum_shouldbe(u_int16_t sum, u_int16_t computed_sum)
 {
 	u_int32_t shouldbe;

 	/*
 	 * The value that should have gone into the checksum field
 	 * is the negative of the value gotten by summing up everything
 	 * *but* the checksum field.
 	 *
 	 * We can compute that by subtracting the value of the checksum
 	 * field from the sum of all the data in the packet, and then
 	 * computing the negative of that value.
 	 *
 	 * "sum" is the value of the checksum field, and "computed_sum"
 	 * is the negative of the sum of all the data in the packets,
 	 * so that's -(-computed_sum - sum), or (sum + computed_sum).
 	 *
 	 * All the arithmetic in question is one's complement, so the
 	 * addition must include an end-around carry; we do this by
 	 * doing the arithmetic in 32 bits (with no sign-extension),
 	 * and then adding the upper 16 bits of the sum, which contain
 	 * the carry, to the lower 16 bits of the sum, and then do it
 	 * again in case *that* sum produced a carry.
 	 *
 	 * As RFC 1071 notes, the checksum can be computed without
 	 * byte-swapping the 16-bit words; summing 16-bit words
 	 * on a big-endian machine gives a big-endian checksum, which
 	 * can be directly stuffed into the big-endian checksum fields
 	 * in protocol headers, and summing words on a little-endian
 	 * machine gives a little-endian checksum, which must be
 	 * byte-swapped before being stuffed into a big-endian checksum
 	 * field.
 	 *
 	 * "computed_sum" is a network-byte-order value, so we must put
 	 * it in host byte order before subtracting it from the
 	 * host-byte-order value from the header; the adjusted checksum
 	 * will be in host byte order, which is what we'll return.
 	 */
 	shouldbe = sum;
 	shouldbe += ntohs(computed_sum);
 	shouldbe = (shouldbe & 0xFFFF) + (shouldbe >> 16);
 	shouldbe = (shouldbe & 0xFFFF) + (shouldbe >> 16);
 	return shouldbe;
 }

 /*
  * print an IP datagram.
  */
 void
 ip_print(register const u_char *bp, register u_int length)
 {
 	register const struct ip *ip;
 	register u_int hlen, len, len0, off;
 	register const u_char *cp;
 	u_char nh;
 	int advance;
 	struct protoent *proto;

 	ip = (const struct ip *)bp;
 #ifdef LBL_ALIGN
 	/*
 	 * If the IP header is not aligned, copy into abuf.
 	 */
 	if ((long)ip & 3) {
 		static u_char *abuf = NULL;
 		static int didwarn = 0;

 		if (abuf == NULL) {
 			abuf = (u_char *)malloc(snaplen);
 			if (abuf == NULL)
 				error("ip_print: malloc");
 		}
 		memcpy((char *)abuf, (char *)ip, min(length, snaplen));
 		snapend += abuf - (u_char *)ip;
 		packetp = abuf;
 		ip = (struct ip *)abuf;
 		/* We really want libpcap to give us aligned packets */
 		if (!didwarn) {
 			warning("compensating for unaligned libpcap packets");
 			++didwarn;
 		}
 	}
 #endif
 	if ((u_char *)(ip + 1) > snapend) {
 		printf("[|ip]");
 		return;
 	}
 	if (length < sizeof (struct ip)) {
 		(void)printf("truncated-ip %d", length);
 		return;
 	}
 	hlen = IP_HL(ip) * 4;
 	if (hlen < sizeof (struct ip)) {
 		(void)printf("bad-hlen %d", hlen);
 		return;
 	}

 	len = ntohs(ip->ip_len);
 	if (length < len)
 		(void)printf("truncated-ip - %d bytes missing! ",
 			len - length);
 	len -= hlen;
 	len0 = len;

         printf("IP ");

 	off = ntohs(ip->ip_off);

         if (vflag) {
             (void)printf("(tos 0x%x", (int)ip->ip_tos);
             /* ECN bits */
             if (ip->ip_tos & 0x03) {
                 switch (ip->ip_tos & 0x03) {
                 case 1:
                     (void)printf(",ECT(1)");
                     break;
                 case 2:
                     (void)printf(",ECT(0)");
                     break;
                 case 3:
                     (void)printf(",CE");
                 }
             }

             if (ip->ip_ttl >= 1)
                 (void)printf(", ttl %d", (int)ip->ip_ttl);

             if ((off & 0x3fff) == 0)
                 (void)printf(", id %d", (int)ntohs(ip->ip_id));
             (void)printf(", len %d) ", (int)ntohs(ip->ip_len));
 	}

 	/*
 	 * If this is fragment zero, hand it to the next higher
 	 * level protocol.
 	 */
 	if ((off & 0x1fff) == 0) {
 		cp = (const u_char *)ip + hlen;
 		nh = ip->ip_p;

 #ifndef IPPROTO_SCTP
 #define IPPROTO_SCTP 132
 #endif
 		if (nh != IPPROTO_TCP && nh != IPPROTO_UDP &&
 		    nh != IPPROTO_SCTP) {
 			(void)printf("%s > %s: ", ipaddr_string(&ip->ip_src),
 				ipaddr_string(&ip->ip_dst));
 		}
 again:
 		switch (nh) {

 #ifndef IPPROTO_AH
 #define IPPROTO_AH	51
 #endif
 		case IPPROTO_AH:
 			nh = *cp;
 			advance = ah_print(cp, (const u_char *)ip);
 			cp += advance;
 			len -= advance;
 			goto again;

 #ifndef IPPROTO_ESP
 #define IPPROTO_ESP	50
 #endif
 		case IPPROTO_ESP:
 		    {
 			int enh, padlen;
 			advance = esp_print(cp, (const u_char *)ip, &enh, &padlen);
 			cp += advance;
 			len -= advance + padlen;
 			if (enh < 0)
 				break;
 			nh = enh & 0xff;
 			goto again;
 		    }

 #ifndef IPPROTO_IPCOMP
 #define IPPROTO_IPCOMP	108
 #endif
 		case IPPROTO_IPCOMP:
 		    {
 			int enh;
 			advance = ipcomp_print(cp, (const u_char *)ip, &enh);
 			cp += advance;
 			len -= advance;
 			if (enh < 0)
 				break;
 			nh = enh & 0xff;
 			goto again;
 		    }

 		case IPPROTO_SCTP:
 			sctp_print(cp, (const u_char *)ip, len);
 			break;

 		case IPPROTO_TCP:
 			tcp_print(cp, len, (const u_char *)ip, (off &~ 0x6000));
 			break;

 		case IPPROTO_UDP:
 			udp_print(cp, len, (const u_char *)ip, (off &~ 0x6000));
 			break;

 		case IPPROTO_ICMP:
 			icmp_print(cp, len, (const u_char *)ip);
 			break;

 #ifndef IPPROTO_IGRP
 #define IPPROTO_IGRP 9
 #endif
 		case IPPROTO_IGRP:
 			igrp_print(cp, len, (const u_char *)ip);
 			break;

 		case IPPROTO_ND:
 			(void)printf(" nd %d", len);
 			break;

 		case IPPROTO_EGP:
 			egp_print(cp, len, (const u_char *)ip);
 			break;

 #ifndef IPPROTO_OSPF
 #define IPPROTO_OSPF 89
 #endif
 		case IPPROTO_OSPF:
 			ospf_print(cp, len, (const u_char *)ip);
 			break;

 #ifndef IPPROTO_IGMP
 #define IPPROTO_IGMP 2
 #endif
 		case IPPROTO_IGMP:
 			igmp_print(cp, len);
 			break;

 		case 4:
 			/* DVMRP multicast tunnel (ip-in-ip encapsulation) */
 			ip_print(cp, len);
 			if (! vflag) {
 				printf(" (ipip-proto-4)");
 				return;
 			}
 			break;

 #ifdef INET6
 #ifndef IP6PROTO_ENCAP
 #define IP6PROTO_ENCAP 41
 #endif
 		case IP6PROTO_ENCAP:
 			/* ip6-in-ip encapsulation */
 			ip6_print(cp, len);
 			break;
 #endif /*INET6*/


 #ifndef IPPROTO_GRE
 #define IPPROTO_GRE 47
 #endif
 		case IPPROTO_GRE:
 			/* do it */
 			gre_print(cp, len);
 			break;

 #ifndef IPPROTO_MOBILE
 #define IPPROTO_MOBILE 55
 #endif
 		case IPPROTO_MOBILE:
 			mobile_print(cp, len);
 			break;

 #ifndef IPPROTO_PIM
 #define IPPROTO_PIM	103
 #endif
 		case IPPROTO_PIM:
 			pim_print(cp, len);
 			break;

 #ifndef IPPROTO_VRRP
 #define IPPROTO_VRRP	112
 #endif
 		case IPPROTO_VRRP:
 			vrrp_print(cp, len, ip->ip_ttl);
 			break;

 		default:
 			if ((proto = getprotobynumber(nh)) != NULL)
 				(void)printf(" %s", proto->p_name);
 			else
 				(void)printf(" ip-proto-%d", nh);
 			printf(" %d", len);
 			break;
 		}
 	}

 	/* Ultra quiet now means that all this stuff should be suppressed */
 	/* res 3-Nov-98 */
 	if (qflag > 1) return;


 	/*
 	 * for fragmented datagrams, print id:size@offset.  On all
 	 * but the last stick a "+".  For unfragmented datagrams, note
 	 * the don't fragment flag.
 	 */
 	len = len0;	/* get the original length */
 	if (off & 0x3fff) {
 		/*
 		 * if this isn't the first frag, we're missing the
 		 * next level protocol header.  print the ip addr
 		 * and the protocol.
 		 */
 		if (off & 0x1fff) {
 			(void)printf("%s > %s:", ipaddr_string(&ip->ip_src),
 				      ipaddr_string(&ip->ip_dst));
 			if ((proto = getprotobynumber(ip->ip_p)) != NULL)
 				(void)printf(" %s", proto->p_name);
 			else
 				(void)printf(" ip-proto-%d", ip->ip_p);
 		}
 #ifndef IP_MF
 #define IP_MF 0x2000
 #endif /* IP_MF */
 #ifndef IP_DF
 #define IP_DF 0x4000
 #endif /* IP_DF */
 		(void)printf(" (frag %d:%u@%d%s)", ntohs(ip->ip_id), len,
 			(off & 0x1fff) * 8,
 			(off & IP_MF)? "+" : "");

 	} else if (off & IP_DF)
 		(void)printf(" (DF)");

 	if (vflag) {
 		u_int16_t sum, ip_sum;
 		char *sep = "";

 		if ((u_char *)ip + hlen <= snapend) {
 			sum = in_cksum((const u_short *)ip, hlen, 0);
 			if (sum != 0) {
 				ip_sum = ntohs(ip->ip_sum);
 				(void)printf("%sbad cksum %x (->%x)!", sep,
 					     ip_sum,
 					     in_cksum_shouldbe(ip_sum, sum));
 				sep = ", ";
 			}
 		}
 		if ((hlen -= sizeof(struct ip)) > 0) {
 			(void)printf("%soptlen=%d", sep, hlen);
 			ip_optprint((u_char *)(ip + 1), hlen);
 		}
 	}

 }

 void
 ipN_print(register const u_char *bp, register u_int length)
 {
 	struct ip *ip, hdr;

 	ip = (struct ip *)bp;
 	if (length < 4) {
 		(void)printf("truncated-ip %d", length);
 		return;
 	}
 	memcpy (&hdr, (char *)ip, 4);
 	switch (IP_V(&hdr)) {
 	case 4:
 		ip_print (bp, length);
 		return;
 #ifdef INET6
 	case 6:
 		ip6_print (bp, length);
 		return;
 #endif
 	default:
 		(void)printf("unknown ip %d", IP_V(&hdr));
 		return;
 	}
 }
	/*
	* Copyright (c) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997
	* The Regents of the University of California. All rights reserved.
	*
	* Redistribution and use in source and binary forms, with or without
	* modification, are permitted provided that: (1) source code distributions
	* retain the above copyright notice and this paragraph in its entirety, (2)
	* distributions including binary code include the above copyright notice and
	* this paragraph in its entirety in the documentation or other materials
	* provided with the distribution, and (3) all advertising materials mentioning
	* features or use of this software display the following acknowledgement:
	* ``This product includes software developed by the University of California,
	* Lawrence Berkeley Laboratory and its contributors.'' Neither the name of
	* the University nor the names of its contributors may be used to endorse
	* or promote products derived from this software without specific prior
	* written permission.
	* THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
	* WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
	* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
	*/

	#ifndef lint
	static const char rcsid[] =
	"@(#) $Header: /tcpdump/master/tcpdump/print-ip.c,v 1.111 2002-08-01 08:53:10 risso Exp $ (LBL)";
	#endif

	#ifdef HAVE_CONFIG_H
	#include "config.h"
	#endif

	#include <tcpdump-stdinc.h>

	#include <stdio.h>
	#include <stdlib.h>
	#include <string.h>

	#include "addrtoname.h"
	#include "interface.h"
	#include "extract.h" /* must come after interface.h */

	#include "ip.h"

	/* Compatibility */
	#ifndef IPPROTO_ND
	#define IPPROTO_ND 77
	#endif

	/*
	* print the recorded route in an IP RR, LSRR or SSRR option.
	*/
	static void
	ip_printroute(const char type, register const u_char cp, u_int length)
	{
	register u_int ptr = cp[2] - 1;
	register u_int len;

	printf(" %s{", type);
	if ((length + 1) & 3)
	printf(" [bad length %d]", length);
	if (ptr < 3 \|\| ((ptr + 1) & 3) \|\| ptr > length + 1)
	printf(" [bad ptr %d]", cp[2]);

	type = "";
	for (len = 3; len < length; len += 4) {
	if (ptr == len)
	type = "#";
	printf("%s%s", type, ipaddr_string(&cp[len]));
	type = " ";
	}
	printf("%s}", ptr == len? "#" : "");
	}

	/*
	* If source-routing is present, return the final destination.
	* Otherwise, return IP destination.
	*
	* This is used for UDP and TCP pseudo-header in the checksum
	* calculation.
	*/
	u_int32_t
	ip_finddst(const struct ip *ip)
	{
	int length;
	int len;
	const u_char *cp;
	u_int32_t retval;

	cp = (const u_char *)(ip + 1);
	length = (IP_HL(ip) << 2) - sizeof(struct ip);

	for (; length > 0; cp += len, length -= len) {
	int tt = *cp;

	if (tt == IPOPT_NOP \|\| tt == IPOPT_EOL)
	len = 1;
	else {
	if (&cp[1] >= snapend) {
	return 0;
	}
	len = cp[1];
	}
	if (len <= 0) {
	return 0;
	}
	if (&cp[1] >= snapend \|\| cp + len > snapend) {
	return 0;
	}
	switch (tt) {

	case IPOPT_SSRR:
	case IPOPT_LSRR:
	memcpy(&retval, cp + len - 4, 4);
	return retval;
	}
	}
	return ip->ip_dst.s_addr;
	}

	static void
	ip_printts(register const u_char *cp, u_int length)
	{
	register u_int ptr = cp[2] - 1;
	register u_int len = 0;
	int hoplen;
	char *type;

	printf(" TS{");
	hoplen = ((cp[3]&0xF) != IPOPT_TS_TSONLY) ? 8 : 4;
	if ((length - 4) & (hoplen-1))
	printf("[bad length %d]", length);
	if (ptr < 4 \|\| ((ptr - 4) & (hoplen-1)) \|\| ptr > length + 1)
	printf("[bad ptr %d]", cp[2]);
	switch (cp[3]&0xF) {
	case IPOPT_TS_TSONLY:
	printf("TSONLY");
	break;
	case IPOPT_TS_TSANDADDR:
	printf("TS+ADDR");
	break;
	/*
	* prespecified should really be 3, but some ones might send 2
	* instead, and the IPOPT_TS_PRESPEC constant can apparently
	* have both values, so we have to hard-code it here.
	*/

	case 2:
	printf("PRESPEC2.0");
	break;
	case 3: /* IPOPT_TS_PRESPEC */
	printf("PRESPEC");
	break;
	default:
	printf("[bad ts type %d]", cp[3]&0xF);
	goto done;
	}

	type = " ";
	for (len = 4; len < length; len += hoplen) {
	if (ptr == len)
	type = " ^ ";
	printf("%s%d@%s", type, EXTRACT_32BITS(&cp[len+hoplen-4]),
	hoplen!=8 ? "" : ipaddr_string(&cp[len]));
	type = " ";
	}

	done:
	printf("%s", ptr == len ? " ^ " : "");

	if (cp[3]>>4)
	printf(" [%d hops not recorded]} ", cp[3]>>4);
	else
	printf("}");
	}

	/*
	* print IP options.
	*/
	static void
	ip_optprint(register const u_char *cp, u_int length)
	{
	register u_int len;

	for (; length > 0; cp += len, length -= len) {
	int tt = *cp;

	if (tt == IPOPT_NOP \|\| tt == IPOPT_EOL)
	len = 1;
	else {
	if (&cp[1] >= snapend) {
	printf("[\|ip]");
	return;
	}
	len = cp[1];
	}
	if (len <= 0) {
	printf("[\|ip op len %d]", len);
	return;
	}
	if (&cp[1] >= snapend \|\| cp + len > snapend) {
	printf("[\|ip]");
	return;
	}
	switch (tt) {

	case IPOPT_EOL:
	printf(" EOL");
	if (length > 1)
	printf("-%d", length - 1);
	return;

	case IPOPT_NOP:
	printf(" NOP");
	break;

	case IPOPT_TS:
	ip_printts(cp, len);
	break;

	#ifndef IPOPT_SECURITY
	#define IPOPT_SECURITY 130
	#endif /* IPOPT_SECURITY */
	case IPOPT_SECURITY:
	printf(" SECURITY{%d}", len);
	break;

	case IPOPT_RR:
	ip_printroute("RR", cp, len);
	break;

	case IPOPT_SSRR:
	ip_printroute("SSRR", cp, len);
	break;

	case IPOPT_LSRR:
	ip_printroute("LSRR", cp, len);
	break;

	#ifndef IPOPT_RA
	#define IPOPT_RA 148 /* router alert */
	#endif
	case IPOPT_RA:
	printf(" RA");
	if (len != 4)
	printf("{%d}", len);
	else if (cp[2] \|\| cp[3])
	printf("%d.%d", cp[2], cp[3]);
	break;

	default:
	printf(" IPOPT-%d{%d}", cp[0], len);
	break;
	}
	}
	}

	/*
	* compute an IP header checksum.
	* don't modifiy the packet.
	*/
	u_short
	in_cksum(const u_short *addr, register u_int len, int csum)
	{
	int nleft = len;
	const u_short *w = addr;
	u_short answer;
	int sum = csum;

	/*
	* Our algorithm is simple, using a 32 bit accumulator (sum),
	* we add sequential 16 bit words to it, and at the end, fold
	* back all the carry bits from the top 16 bits into the lower
	* 16 bits.
	*/
	while (nleft > 1) {
	sum += *w++;
	nleft -= 2;
	}
	if (nleft == 1)
	sum += htons((u_char )w<<8);

	/*
	* add back carry outs from top 16 bits to low 16 bits
	*/
	sum = (sum >> 16) + (sum & 0xffff); /* add hi 16 to low 16 */
	sum += (sum >> 16); /* add carry */
	answer = ~sum; /* truncate to 16 bits */
	return (answer);
	}

	/*
	* Given the host-byte-order value of the checksum field in a packet
	* header, and the network-byte-order computed checksum of the data
	* that the checksum covers (including the checksum itself), compute
	* what the checksum field should have been.
	*/
	u_int16_t
	in_cksum_shouldbe(u_int16_t sum, u_int16_t computed_sum)
	{
	u_int32_t shouldbe;

	/*
	* The value that should have gone into the checksum field
	* is the negative of the value gotten by summing up everything
	* but the checksum field.
	*
	* We can compute that by subtracting the value of the checksum
	* field from the sum of all the data in the packet, and then
	* computing the negative of that value.
	*
	* "sum" is the value of the checksum field, and "computed_sum"
	* is the negative of the sum of all the data in the packets,
	* so that's -(-computed_sum - sum), or (sum + computed_sum).
	*
	* All the arithmetic in question is one's complement, so the
	* addition must include an end-around carry; we do this by
	* doing the arithmetic in 32 bits (with no sign-extension),
	* and then adding the upper 16 bits of the sum, which contain
	* the carry, to the lower 16 bits of the sum, and then do it
	* again in case that sum produced a carry.
	*
	* As RFC 1071 notes, the checksum can be computed without
	* byte-swapping the 16-bit words; summing 16-bit words
	* on a big-endian machine gives a big-endian checksum, which
	* can be directly stuffed into the big-endian checksum fields
	* in protocol headers, and summing words on a little-endian
	* machine gives a little-endian checksum, which must be
	* byte-swapped before being stuffed into a big-endian checksum
	* field.
	*
	* "computed_sum" is a network-byte-order value, so we must put
	* it in host byte order before subtracting it from the
	* host-byte-order value from the header; the adjusted checksum
	* will be in host byte order, which is what we'll return.
	*/
	shouldbe = sum;
	shouldbe += ntohs(computed_sum);
	shouldbe = (shouldbe & 0xFFFF) + (shouldbe >> 16);
	shouldbe = (shouldbe & 0xFFFF) + (shouldbe >> 16);
	return shouldbe;
	}

	/*
	* print an IP datagram.
	*/
	void
	ip_print(register const u_char *bp, register u_int length)
	{
	register const struct ip *ip;
	register u_int hlen, len, len0, off;
	register const u_char *cp;
	u_char nh;
	int advance;
	struct protoent *proto;

	ip = (const struct ip *)bp;
	#ifdef LBL_ALIGN
	/*
	* If the IP header is not aligned, copy into abuf.
	*/
	if ((long)ip & 3) {
	static u_char *abuf = NULL;
	static int didwarn = 0;

	if (abuf == NULL) {
	abuf = (u_char *)malloc(snaplen);
	if (abuf == NULL)
	error("ip_print: malloc");
	}
	memcpy((char )abuf, (char )ip, min(length, snaplen));
	snapend += abuf - (u_char *)ip;
	packetp = abuf;
	ip = (struct ip *)abuf;
	/* We really want libpcap to give us aligned packets */
	if (!didwarn) {
	warning("compensating for unaligned libpcap packets");
	++didwarn;
	}
	}
	#endif
	if ((u_char *)(ip + 1) > snapend) {
	printf("[\|ip]");
	return;
	}
	if (length < sizeof (struct ip)) {
	(void)printf("truncated-ip %d", length);
	return;
	}
	hlen = IP_HL(ip) * 4;
	if (hlen < sizeof (struct ip)) {
	(void)printf("bad-hlen %d", hlen);
	return;
	}

	len = ntohs(ip->ip_len);
	if (length < len)
	(void)printf("truncated-ip - %d bytes missing! ",
	len - length);
	len -= hlen;
	len0 = len;

	printf("IP ");

	off = ntohs(ip->ip_off);

	if (vflag) {
	(void)printf("(tos 0x%x", (int)ip->ip_tos);
	/* ECN bits */
	if (ip->ip_tos & 0x03) {
	switch (ip->ip_tos & 0x03) {
	case 1:
	(void)printf(",ECT(1)");
	break;
	case 2:
	(void)printf(",ECT(0)");
	break;
	case 3:
	(void)printf(",CE");
	}
	}

	if (ip->ip_ttl >= 1)
	(void)printf(", ttl %d", (int)ip->ip_ttl);

	if ((off & 0x3fff) == 0)
	(void)printf(", id %d", (int)ntohs(ip->ip_id));
	(void)printf(", len %d) ", (int)ntohs(ip->ip_len));
	}

	/*
	* If this is fragment zero, hand it to the next higher
	* level protocol.
	*/
	if ((off & 0x1fff) == 0) {
	cp = (const u_char *)ip + hlen;
	nh = ip->ip_p;

	#ifndef IPPROTO_SCTP
	#define IPPROTO_SCTP 132
	#endif
	if (nh != IPPROTO_TCP && nh != IPPROTO_UDP &&
	nh != IPPROTO_SCTP) {
	(void)printf("%s > %s: ", ipaddr_string(&ip->ip_src),
	ipaddr_string(&ip->ip_dst));
	}
	again:
	switch (nh) {

	#ifndef IPPROTO_AH
	#define IPPROTO_AH 51
	#endif
	case IPPROTO_AH:
	nh = *cp;
	advance = ah_print(cp, (const u_char *)ip);
	cp += advance;
	len -= advance;
	goto again;

	#ifndef IPPROTO_ESP
	#define IPPROTO_ESP 50
	#endif
	case IPPROTO_ESP:
	{
	int enh, padlen;
	advance = esp_print(cp, (const u_char *)ip, &enh, &padlen);
	cp += advance;
	len -= advance + padlen;
	if (enh < 0)
	break;
	nh = enh & 0xff;
	goto again;
	}

	#ifndef IPPROTO_IPCOMP
	#define IPPROTO_IPCOMP 108
	#endif
	case IPPROTO_IPCOMP:
	{
	int enh;
	advance = ipcomp_print(cp, (const u_char *)ip, &enh);
	cp += advance;
	len -= advance;
	if (enh < 0)
	break;
	nh = enh & 0xff;
	goto again;
	}

	case IPPROTO_SCTP:
	sctp_print(cp, (const u_char *)ip, len);
	break;

	case IPPROTO_TCP:
	tcp_print(cp, len, (const u_char *)ip, (off &~ 0x6000));
	break;

	case IPPROTO_UDP:
	udp_print(cp, len, (const u_char *)ip, (off &~ 0x6000));
	break;

	case IPPROTO_ICMP:
	icmp_print(cp, len, (const u_char *)ip);
	break;

	#ifndef IPPROTO_IGRP
	#define IPPROTO_IGRP 9
	#endif
	case IPPROTO_IGRP:
	igrp_print(cp, len, (const u_char *)ip);
	break;

	case IPPROTO_ND:
	(void)printf(" nd %d", len);
	break;

	case IPPROTO_EGP:
	egp_print(cp, len, (const u_char *)ip);
	break;

	#ifndef IPPROTO_OSPF
	#define IPPROTO_OSPF 89
	#endif
	case IPPROTO_OSPF:
	ospf_print(cp, len, (const u_char *)ip);
	break;

	#ifndef IPPROTO_IGMP
	#define IPPROTO_IGMP 2
	#endif
	case IPPROTO_IGMP:
	igmp_print(cp, len);
	break;

	case 4:
	/* DVMRP multicast tunnel (ip-in-ip encapsulation) */
	ip_print(cp, len);
	if (! vflag) {
	printf(" (ipip-proto-4)");
	return;
	}
	break;

	#ifdef INET6
	#ifndef IP6PROTO_ENCAP
	#define IP6PROTO_ENCAP 41
	#endif
	case IP6PROTO_ENCAP:
	/* ip6-in-ip encapsulation */
	ip6_print(cp, len);
	break;
	#endif /INET6/


	#ifndef IPPROTO_GRE
	#define IPPROTO_GRE 47
	#endif
	case IPPROTO_GRE:
	/* do it */
	gre_print(cp, len);
	break;

	#ifndef IPPROTO_MOBILE
	#define IPPROTO_MOBILE 55
	#endif
	case IPPROTO_MOBILE:
	mobile_print(cp, len);
	break;

	#ifndef IPPROTO_PIM
	#define IPPROTO_PIM 103
	#endif
	case IPPROTO_PIM:
	pim_print(cp, len);
	break;

	#ifndef IPPROTO_VRRP
	#define IPPROTO_VRRP 112
	#endif
	case IPPROTO_VRRP:
	vrrp_print(cp, len, ip->ip_ttl);
	break;

	default:
	if ((proto = getprotobynumber(nh)) != NULL)
	(void)printf(" %s", proto->p_name);
	else
	(void)printf(" ip-proto-%d", nh);
	printf(" %d", len);
	break;
	}
	}

	/* Ultra quiet now means that all this stuff should be suppressed */
	/* res 3-Nov-98 */
	if (qflag > 1) return;


	/*
	* for fragmented datagrams, print id:size@offset. On all
	* but the last stick a "+". For unfragmented datagrams, note
	* the don't fragment flag.
	*/
	len = len0; /* get the original length */
	if (off & 0x3fff) {
	/*
	* if this isn't the first frag, we're missing the
	* next level protocol header. print the ip addr
	* and the protocol.
	*/
	if (off & 0x1fff) {
	(void)printf("%s > %s:", ipaddr_string(&ip->ip_src),
	ipaddr_string(&ip->ip_dst));
	if ((proto = getprotobynumber(ip->ip_p)) != NULL)
	(void)printf(" %s", proto->p_name);
	else
	(void)printf(" ip-proto-%d", ip->ip_p);
	}
	#ifndef IP_MF
	#define IP_MF 0x2000
	#endif /* IP_MF */
	#ifndef IP_DF
	#define IP_DF 0x4000
	#endif /* IP_DF */
	(void)printf(" (frag %d:%u@%d%s)", ntohs(ip->ip_id), len,
	(off & 0x1fff) * 8,
	(off & IP_MF)? "+" : "");

	} else if (off & IP_DF)
	(void)printf(" (DF)");

	if (vflag) {
	u_int16_t sum, ip_sum;
	char *sep = "";

	if ((u_char *)ip + hlen <= snapend) {
	sum = in_cksum((const u_short *)ip, hlen, 0);
	if (sum != 0) {
	ip_sum = ntohs(ip->ip_sum);
	(void)printf("%sbad cksum %x (->%x)!", sep,
	ip_sum,
	in_cksum_shouldbe(ip_sum, sum));
	sep = ", ";
	}
	}
	if ((hlen -= sizeof(struct ip)) > 0) {
	(void)printf("%soptlen=%d", sep, hlen);
	ip_optprint((u_char *)(ip + 1), hlen);
	}
	}

	}

	void
	ipN_print(register const u_char *bp, register u_int length)
	{
	struct ip *ip, hdr;

	ip = (struct ip *)bp;
	if (length < 4) {
	(void)printf("truncated-ip %d", length);
	return;
	}
	memcpy (&hdr, (char *)ip, 4);
	switch (IP_V(&hdr)) {
	case 4:
	ip_print (bp, length);
	return;
	#ifdef INET6
	case 6:
	ip6_print (bp, length);
	return;
	#endif
	default:
	(void)printf("unknown ip %d", IP_V(&hdr));
	return;
	}
	}