from nicolas ferrero <[email protected]>:

[tcpdump] / 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 1.146 2005-01-12 11:19:08 hannes 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"

struct tok ip_option_values[] = {
    { IPOPT_EOL, "EOL" },
    { IPOPT_NOP, "NOP" },
    { IPOPT_TS, "timestamp" },
    { IPOPT_SECURITY, "security" },
    { IPOPT_RR, "RR" },
    { IPOPT_SSRR, "SSRR" },
    { IPOPT_LSRR, "LSRR" },
    { IPOPT_RA, "RA" },
    { 0, NULL }
};

/*
 * print the recorded route in an IP RR, LSRR or SSRR option.
 */
static void
ip_printroute(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;
        }
        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]);

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

/*
 * If source-routing is present and valid, 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_EOL)
                        break;
                else if (tt == IPOPT_NOP)
                        len = 1;
                else {
                        TCHECK(cp[1]);
                        len = cp[1];
                        if (len < 2)
                                break;
                }
                TCHECK2(*cp, len);
                switch (tt) {

                case IPOPT_SSRR:
                case IPOPT_LSRR:
                        if (len < 7)
                                break;
                        memcpy(&retval, cp + len - 4, 4);
                        return retval;
                }
        }
trunc:
        memcpy(&retval, &ip->ip_dst.s_addr, sizeof(u_int32_t));
        return retval;
}

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 option_len;

        for (; length > 0; cp += option_len, length -= option_len) {
                u_int option_code;

                TCHECK(*cp);
                option_code = *cp;

                if (option_code == IPOPT_NOP ||
                    option_code == IPOPT_EOL)
                        option_len = 1;

                else {
                        TCHECK(cp[1]);
                        option_len = cp[1];                     
                }

                printf("%s (%u) len %u",
                       tok2str(ip_option_values,"unknown",option_code),
                       option_code,
                       option_len);

                if (option_len < 2)
                        return;

                TCHECK2(*cp, option_len);

                switch (option_code) {
                case IPOPT_EOL:
                        return;

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

                case IPOPT_RR:       /* fall through */
                case IPOPT_SSRR:
                case IPOPT_LSRR:
                        ip_printroute( cp, option_len);
                        break;

                case IPOPT_RA:
                        TCHECK(cp[3]);
                        if (EXTRACT_16BITS(&cp[2]) != 0)
                            printf("value %u", EXTRACT_16BITS(&cp[2]));
                        break;

                case IPOPT_NOP:       /* nothing to print - fall through */
                case IPOPT_SECURITY:
                default:
                        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, 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 if (!eflag)
            printf("IP ");

        if ((u_char *)(ip + 1) > snapend) {
                printf("[|ip]");
                return;
        }
        if (length < sizeof (struct ip)) {
                (void)printf("truncated-ip %u", 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;

        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], proto: %s (%u)",
                         EXTRACT_16BITS(&ip->ip_id),
                         (off & 0x1fff) * 8,
                         bittok2str(ip_frag_values, "none", off & 0xe000 ),
                         tok2str(ipproto_values,"unknown",ip->ip_p),
                         ip->ip_p);

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

            if ((hlen - sizeof(struct ip)) > 0) {
                printf(", options ( ");
                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(gndo, cp, len, (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_PIGP:
                        /*
                         * XXX - the current IANA protocol number assignments
                         * page lists 9 as "any private interior gateway
                         * (used by Cisco for their IGRP)" and 88 as
                         * "EIGRP" from Cisco.
                         *
                         * Recent BSD <netinet/in.h> headers define
                         * IP_PROTO_PIGP as 9 and IP_PROTO_IGRP as 88.
                         * We define IP_PROTO_PIGP as 9 and
                         * IP_PROTO_EIGRP as 88; those names better
                         * match was the current protocol number
                         * assignments say.
                         */
                        igrp_print(cp, len, (const u_char *)ip);
                        break;

                case IPPROTO_EIGRP:
                        eigrp_print(cp, len);
                        break;

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

                case IPPROTO_EGP:
                        egp_print(cp, len);
                        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;
        }
}