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print-ip.c

/*
 * 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[] _U_ =
    "@(#) $Header: /tcpdump/master/tcpdump/print-ip.c,v 1.128.2.6 2004/03/24 09:01:39 guy 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"
#include "ipproto.h"

/*
 * 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;
      register u_int len;

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

            TCHECK(*cp);
            tt = *cp;
            if (tt == IPOPT_NOP || tt == IPOPT_EOL)
                  len = 1;
            else {
                  TCHECK(cp[1]);
                  len = cp[1];
            }
            if (len < 2) {
                  return 0;
            }
            TCHECK2(*cp, len);
            switch (tt) {

            case IPOPT_SSRR:
            case IPOPT_LSRR:
                  if (len < 7)
                        return 0;
                  memcpy(&retval, cp + len - 4, 4);
                  return retval;
            }
      }
      return ip->ip_dst.s_addr;

trunc:
      return 0;
}

static void
ip_printts(register const u_char *cp, u_int length)
{
      register u_int ptr;
      register u_int len;
      int hoplen;
      const char *type;

      if (length < 4) {
            printf("[bad length %d]", length);
            return;
      }
      printf(" TS{");
      hoplen = ((cp[3]&0xF) != IPOPT_TS_TSONLY) ? 8 : 4;
      if ((length - 4) & (hoplen-1))
            printf("[bad length %d]", length);
      ptr = cp[2] - 1;
      len = 0;
      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;

            TCHECK(*cp);
            tt = *cp;
            if (tt == IPOPT_NOP || tt == IPOPT_EOL)
                  len = 1;
            else {
                  TCHECK(cp[1]);
                  len = cp[1];
                  if (len < 2) {
                        printf("[|ip op len %d]", len);
                        return;
                  }
                  TCHECK2(*cp, len);
            }
            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 {
                        TCHECK(cp[3]);
                        if (cp[2] || cp[3])
                              printf("%d.%d", cp[2], cp[3]);
                  }
                  break;

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

trunc:
      printf("[|ip]");
}

/*
 * 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;
}

#ifndef IP_MF
#define IP_MF 0x2000
#endif /* IP_MF */
#ifndef IP_DF
#define IP_DF 0x4000
#endif /* IP_DF */
#define IP_RES 0x8000

static struct tok ip_frag_values[] = {
        { IP_MF,        "+" },
        { IP_DF,        "DF" },
      { IP_RES,       "rsvd" }, /* The RFC3514 evil ;-) bit */
        { 0,            NULL }
};

/*
 * 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;
      const u_char *ipend;
      register const u_char *cp;
      u_char nh;
      int advance;
      struct protoent *proto;
      u_int16_t sum, ip_sum;

      ip = (const struct ip *)bp;
      if (IP_V(ip) != 4) { /* print version if != 4 */
          printf("IP%u ", IP_V(ip));
          if (IP_V(ip) == 6)
            printf(", wrong link-layer encapsulation");
      }
        else
          printf("IP ");

      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 %u", hlen);
            return;
      }

      len = EXTRACT_16BITS(&ip->ip_len);
      if (length < len)
            (void)printf("truncated-ip - %u bytes missing! ",
                  len - length);
      if (len < hlen) {
            (void)printf("bad-len %u", len);
            return;
      }

      /*
       * Cut off the snapshot length to the end of the IP payload.
       */
      ipend = bp + len;
      if (ipend < snapend)
            snapend = ipend;

      len -= hlen;
      len0 = len;

      off = EXTRACT_16BITS(&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 %3u", ip->ip_ttl);    

          /*
           * for the firewall guys, print id, offset.
             * On all but the last stick a "+" in the flags portion.
           * For unfragmented datagrams, note the don't fragment flag.
           */

          (void)printf(", id %u, offset %u, flags [%s]",
                       EXTRACT_16BITS(&ip->ip_id),
                       (off & 0x1fff) * 8,
                       bittok2str(ip_frag_values, "none", off & 0xe000 ));

            (void)printf(", length: %u", EXTRACT_16BITS(&ip->ip_len));

            if ((hlen - sizeof(struct ip)) > 0) {
                (void)printf(", optlength: %u (", hlen - (u_int)sizeof(struct ip));
                ip_optprint((u_char *)(ip + 1), hlen - sizeof(struct ip));
                printf(" )");
            }

          if ((u_char *)ip + hlen <= snapend) {
              sum = in_cksum((const u_short *)ip, hlen, 0);
            if (sum != 0) {
                ip_sum = EXTRACT_16BITS(&ip->ip_sum);
                (void)printf(", bad cksum %x (->%x)!", ip_sum,
                       in_cksum_shouldbe(ip_sum, sum));
            }
          }

            printf(") ");
      }

      /*
       * 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;

            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) {

            case IPPROTO_AH:
                  nh = *cp;
                  advance = ah_print(cp);
                  if (advance <= 0)
                        break;
                  cp += advance;
                  len -= advance;
                  goto again;

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

            case IPPROTO_IPCOMP:
                {
                  int enh;
                  advance = ipcomp_print(cp, &enh);
                  if (advance <= 0)
                        break;
                  cp += advance;
                  len -= advance;
                  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:
                    /* pass on the MF bit plus the offset to detect fragments */
                  icmp_print(cp, len, (const u_char *)ip, (off & 0x3fff));
                  break;

            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);
                  break;

            case IPPROTO_OSPF:
                  ospf_print(cp, len, (const u_char *)ip);
                  break;

            case IPPROTO_IGMP:
                  igmp_print(cp, len);
                  break;

            case IPPROTO_IPV4:
                  /* DVMRP multicast tunnel (ip-in-ip encapsulation) */
                  ip_print(cp, len);
                  if (! vflag) {
                        printf(" (ipip-proto-4)");
                        return;
                  }
                  break;

#ifdef INET6
            case IPPROTO_IPV6:
                  /* ip6-in-ip encapsulation */
                  ip6_print(cp, len);
                  break;
#endif /*INET6*/

            case IPPROTO_RSVP:
                  rsvp_print(cp, len);
                  break;

            case IPPROTO_GRE:
                  /* do it */
                  gre_print(cp, len);
                  break;

            case IPPROTO_MOBILE:
                  mobile_print(cp, len);
                  break;

            case IPPROTO_PIM:
                  pim_print(cp, len);
                  break;

            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;
            }
      } else {
          /* Ultra quiet now means that all this stuff should be suppressed */
          if (qflag > 1) return;

          /*
           * 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);
          } 
      }
}

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;
      }
}




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