[tcpdump] / print-cdp.c

/*
 * Copyright (c) 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.
 *
 * Code by Gert Doering, SpaceNet GmbH, gert@space.net
 *
 * Reference documentation:
 *    https://web.archive.org/web/20000914194913/http://www.cisco.com/univercd/cc/td/doc/product/lan/trsrb/frames.pdf
 */

/* \summary: Cisco Discovery Protocol (CDP) printer */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include "netdissect-stdinc.h"

#include <string.h>

#define ND_LONGJMP_FROM_TCHECK
#include "netdissect.h"
#include "addrtoname.h"
#include "extract.h"
#include "nlpid.h"


#define CDP_HEADER_LEN             4
#define CDP_HEADER_VERSION_OFFSET  0
#define CDP_HEADER_TTL_OFFSET      1
#define CDP_HEADER_CHECKSUM_OFFSET 2

#define CDP_TLV_HEADER_LEN  4
#define CDP_TLV_TYPE_OFFSET 0
#define CDP_TLV_LEN_OFFSET  2

static const struct tok cdp_capability_values[] = {
    { 0x01,             "Router" },
    { 0x02,             "Transparent Bridge" },
    { 0x04,             "Source Route Bridge" },
    { 0x08,             "L2 Switch" },
    { 0x10,             "L3 capable" },
    { 0x20,             "IGMP snooping" },
    { 0x40,             "L1 capable" },
    { 0, NULL }
};

static void cdp_print_addr(netdissect_options *, const u_char *, u_int);
static void cdp_print_prefixes(netdissect_options *, const u_char *, u_int);

static void
cdp_print_string(netdissect_options *ndo,
                 const u_char *cp, const u_int len)
{
        ND_PRINT("'");
        nd_printjn(ndo, cp, len);
        ND_PRINT("'");
}

static void
cdp_print_power(netdissect_options *ndo,
                const u_char *cp, const u_int len)
{
        u_int val = 0;

        switch (len) {
        case 1:
                val = GET_U_1(cp);
                break;
        case 2:
                val = GET_BE_U_2(cp);
                break;
        case 3:
                val = GET_BE_U_3(cp);
                break;
        }
        ND_PRINT("%1.2fW", val / 1000.0);
}

static void
cdp_print_capability(netdissect_options *ndo,
                     const u_char *cp, const u_int len _U_)
{
        uint32_t val = GET_BE_U_4(cp);

        ND_PRINT("(0x%08x): %s", val,
                 bittok2str(cdp_capability_values, "none", val));
}

/* Rework the version string to get a nice indentation. */
static void
cdp_print_version(netdissect_options *ndo,
                  const u_char *cp, const u_int len)
{
        unsigned i;

        ND_PRINT("\n\t  ");
        for (i = 0; i < len; i++) {
                u_char c = GET_U_1(cp + i);

                if (c == '\n')
                        ND_PRINT("\n\t  ");
                else
                        fn_print_char(ndo, c);
        }
}

static void
cdp_print_uint16(netdissect_options *ndo,
                 const u_char *cp, const u_int len _U_)
{
        ND_PRINT("%u", GET_BE_U_2(cp));
}

static void
cdp_print_duplex(netdissect_options *ndo,
                 const u_char *cp, const u_int len _U_)
{
        ND_PRINT("%s", GET_U_1(cp) ? "full": "half");
}

/* https://www.cisco.com/c/en/us/td/docs/voice_ip_comm/cata/186/2_12_m/english/release/notes/186rn21m.html
* plus more details from other sources
*
* There are apparently versions of the request with both
* 2 bytes and 3 bytes of value.  The 3 bytes of value
* appear to be a 1-byte application type followed by a
* 2-byte VLAN ID; the 2 bytes of value are unknown
* (they're 0x20 0x00 in some captures I've seen; that
* is not a valid VLAN ID, as VLAN IDs are 12 bits).
*
* The replies all appear to be 3 bytes long.
*/
static void
cdp_print_ata186(netdissect_options *ndo,
                 const u_char *cp, const u_int len)
{
        if (len == 2)
                ND_PRINT("unknown 0x%04x", GET_BE_U_2(cp));
        else
                ND_PRINT("app %u, vlan %u", GET_U_1(cp), GET_BE_U_2(cp + 1));
}

static void
cdp_print_mtu(netdissect_options *ndo,
              const u_char *cp, const u_int len _U_)
{
        ND_PRINT("%u bytes", GET_BE_U_4(cp));
}

static void
cdp_print_uint8x(netdissect_options *ndo,
                 const u_char *cp, const u_int len _U_)
{
        ND_PRINT("0x%02x", GET_U_1(cp));
}

static void
cdp_print_phys_loc(netdissect_options *ndo,
                   const u_char *cp, const u_int len)
{
        ND_PRINT("0x%02x", GET_U_1(cp));
        if (len > 1) {
                ND_PRINT("/");
                nd_printjn(ndo, cp + 1, len - 1);
        }
}

typedef enum {
        VERBOSE_OR_NOT_VERBOSE,
        VERBOSE_ONLY
} when_to_print_t;

struct cdp_tlvinfo {
        const char *name;
        void (*printer)(netdissect_options *ndo, const u_char *, u_int);
        when_to_print_t when_to_print;
        int min_len, max_len;
};

static const struct cdp_tlvinfo cdptlvs[] = {
        /* 0x00 */
        [ 0x01 ] = { "Device-ID", cdp_print_string, VERBOSE_OR_NOT_VERBOSE, -1, -1 },
        [ 0x02 ] = { "Address", cdp_print_addr, VERBOSE_ONLY, -1, -1 },
        [ 0x03 ] = { "Port-ID", cdp_print_string, VERBOSE_ONLY, -1, -1 },
        [ 0x04 ] = { "Capability", cdp_print_capability, VERBOSE_ONLY, 4, 4 },
        [ 0x05 ] = { "Version String", cdp_print_version, VERBOSE_ONLY, -1, -1 },
        [ 0x06 ] = { "Platform", cdp_print_string, VERBOSE_ONLY, -1, -1 },
        [ 0x07 ] = { "Prefixes", cdp_print_prefixes, VERBOSE_ONLY, -1, -1 },
        /* not documented */
        [ 0x08 ] = { "Protocol-Hello option", NULL, VERBOSE_ONLY, -1, -1 },
        /* CDPv2 */
        [ 0x09 ] = { "VTP Management Domain", cdp_print_string, VERBOSE_ONLY, -1, -1 },
        /* CDPv2 */
        [ 0x0a ] = { "Native VLAN ID", cdp_print_uint16, VERBOSE_ONLY, 2, 2 },
        /* CDPv2 */
        [ 0x0b ] = { "Duplex", cdp_print_duplex, VERBOSE_ONLY, 1, 1 },
        /* 0x0c */
        /* 0x0d */
        /* incomplete doc. */
        [ 0x0e ] = { "ATA-186 VoIP VLAN assignment", cdp_print_ata186, VERBOSE_ONLY, 3, 3 },
        /* incomplete doc. */
        [ 0x0f ] = { "ATA-186 VoIP VLAN request", cdp_print_ata186, VERBOSE_ONLY, 2, 3 },
        /* not documented */
        [ 0x10 ] = { "power consumption", cdp_print_power, VERBOSE_ONLY, 1, 3 },
        /* not documented */
        [ 0x11 ] = { "MTU", cdp_print_mtu, VERBOSE_ONLY, 4, 4 },
        /* not documented */
        [ 0x12 ] = { "AVVID trust bitmap", cdp_print_uint8x, VERBOSE_ONLY, 1, 1 },
        /* not documented */
        [ 0x13 ] = { "AVVID untrusted ports CoS", cdp_print_uint8x, VERBOSE_ONLY, 1, 1 },
        /* not documented */
        [ 0x14 ] = { "System Name", cdp_print_string, VERBOSE_ONLY, -1, -1 },
        /* not documented */
        [ 0x15 ] = { "System Object ID (not decoded)", NULL, VERBOSE_ONLY, -1, -1 },
        [ 0x16 ] = { "Management Addresses", cdp_print_addr, VERBOSE_ONLY, 4, -1 },
        /* not documented */
        [ 0x17 ] = { "Physical Location", cdp_print_phys_loc, VERBOSE_ONLY, 1, -1 },
};

#define T_MAX   (sizeof cdptlvs / sizeof cdptlvs[0])

void
cdp_print(netdissect_options *ndo,
          const u_char *tptr, u_int length)
{
        u_int orig_length = length;
        uint16_t checksum;

        ndo->ndo_protocol = "cdp";

        if (length < CDP_HEADER_LEN) {
                ND_PRINT(" (packet length %u < %u)", length, CDP_HEADER_LEN);
                goto invalid;
        }
        ND_PRINT("CDPv%u, ttl: %us",
                 GET_U_1(tptr + CDP_HEADER_VERSION_OFFSET),
                 GET_U_1(tptr + CDP_HEADER_TTL_OFFSET));
        checksum = GET_BE_U_2(tptr + CDP_HEADER_CHECKSUM_OFFSET);
        if (ndo->ndo_vflag)
                ND_PRINT(", checksum: 0x%04x (unverified), length %u",
                         checksum, orig_length);
        tptr += CDP_HEADER_LEN;
        length -= CDP_HEADER_LEN;

        while (length) {
                u_int type, len;
                const struct cdp_tlvinfo *info;
                const char *name;
                int print_if_not_verbose;
                int covered = 0;

                if (length < CDP_TLV_HEADER_LEN) {
                        ND_PRINT(" (remaining packet length %u < %u)",
                                 length, CDP_TLV_HEADER_LEN);
                        goto invalid;
                }
                type = GET_BE_U_2(tptr + CDP_TLV_TYPE_OFFSET);
                len  = GET_BE_U_2(tptr + CDP_TLV_LEN_OFFSET); /* object length includes the 4 bytes header length */
                info = type < T_MAX ? &cdptlvs[type] : NULL;
                name = (info && info->name) ? info->name : "unknown field type";
                print_if_not_verbose =
                    (info ? (info->when_to_print == VERBOSE_OR_NOT_VERBOSE) : 0);
                if (len < CDP_TLV_HEADER_LEN) {
                        if (ndo->ndo_vflag)
                                ND_PRINT("\n\t%s (0x%02x), TLV length: %u byte%s (too short)",
                                         name, type, len, PLURAL_SUFFIX(len));
                        else
                                ND_PRINT(", %s TLV length %u too short",
                                         name, len);
                        goto invalid;
                }
                if (len > length) {
                        ND_PRINT(" (TLV length %u > %u)", len, length);
                        goto invalid;
                }
                tptr += CDP_TLV_HEADER_LEN;
                length -= CDP_TLV_HEADER_LEN;
                len -= CDP_TLV_HEADER_LEN;

                if (ndo->ndo_vflag) {
                        /* Print all TLVs when in verbose mode */
                        ND_PRINT("\n\t%s (0x%02x), value length: %u byte%s: ",
                                 name, type, len, PLURAL_SUFFIX(len));
                } else {
                        /* Print only some TLVs when not in verbose mode */
                        if (print_if_not_verbose)
                                ND_PRINT(", %s ", name);
                }

                if (info) {
                        if ((info->min_len > 0 && len < (unsigned)info->min_len) ||
                            (info->max_len > 0 && len > (unsigned)info->max_len))
                                ND_PRINT(" (malformed TLV)");
                        else if (ndo->ndo_vflag || print_if_not_verbose) {
                                if (info->printer)
                                        info->printer(ndo, tptr, len);
                                else
                                        ND_TCHECK_LEN(tptr, len);
                                /*
                                 * When the type is defined without a printer,
                                 * do not print the hex dump.
                                 */
                                covered = 1;
                        }
                }

                if (ndo->ndo_vflag && !covered) {
                        ND_TCHECK_LEN(tptr, len);
                        print_unknown_data(ndo, tptr, "\n\t  ", len);
                }
                tptr += len;
                length -= len;
        }
        if (ndo->ndo_vflag < 1)
                ND_PRINT(", length %u", orig_length);

        return;
invalid:
        nd_print_invalid(ndo);
        ND_TCHECK_LEN(tptr, length);
}

/*
 * Protocol type values.
 *
 * PT_NLPID means that the protocol type field contains an OSI NLPID.
 *
 * PT_IEEE_802_2 means that the protocol type field contains an IEEE 802.2
 * LLC header that specifies that the payload is for that protocol.
 */
#define PT_NLPID                1       /* OSI NLPID */
#define PT_IEEE_802_2           2       /* IEEE 802.2 LLC header */

static void
cdp_print_addr(netdissect_options *ndo,
               const u_char * p, u_int l)
{
        u_int num;
        static const u_char prot_ipv6[] = {
                0xaa, 0xaa, 0x03, 0x00, 0x00, 0x00, 0x86, 0xdd
        };

        if (l < 4) {
                ND_PRINT(" (not enough space for num)");
                goto invalid;
        }
        num = GET_BE_U_4(p);
        p += 4;
        l -= 4;

        while (num) {
                u_int pt, pl, al;

                if (l < 2) {
                        ND_PRINT(" (not enough space for PT+PL)");
                        goto invalid;
                }
                pt = GET_U_1(p);                /* type of "protocol" field */
                pl = GET_U_1(p + 1);    /* length of "protocol" field */
                p += 2;
                l -= 2;

                if (l < pl + 2) {
                        ND_PRINT(" (not enough space for P+AL)");
                        goto invalid;
                }
                /* Skip the protocol for now. */
                al = GET_BE_U_2(p + pl);        /* address length */

                if (pt == PT_NLPID && pl == 1 && GET_U_1(p) == NLPID_IP &&
                    al == 4) {
                        /*
                         * IPv4: protocol type = NLPID, protocol length = 1
                         * (1-byte NLPID), protocol = 0xcc (NLPID for IPv4),
                         * address length = 4
                         */
                        p += pl + 2;
                        l -= pl + 2;
                        /* p is just beyond al now. */
                        if (l < al) {
                                ND_PRINT(" (not enough space for A)");
                                goto invalid;
                        }
                        ND_PRINT("IPv4 (%u) %s", num, GET_IPADDR_STRING(p));
                        p += al;
                        l -= al;
                }
                else if (pt == PT_IEEE_802_2 && pl == 8 &&
                         memcmp(p, prot_ipv6, 8) == 0 && al == 16) {
                        /*
                         * IPv6: protocol type = IEEE 802.2 header,
                         * protocol length = 8 (size of LLC+SNAP header),
                         * protocol = LLC+SNAP header with the IPv6
                         * Ethertype, address length = 16
                         */
                        p += pl + 2;
                        l -= pl + 2;
                        /* p is just beyond al now. */
                        if (l < al) {
                                ND_PRINT(" (not enough space for A)");
                                goto invalid;
                        }
                        ND_PRINT("IPv6 (%u) %s", num, GET_IP6ADDR_STRING(p));
                        p += al;
                        l -= al;
                }
                else {
                        /*
                         * Generic case: just print raw data
                         */
                        ND_PRINT("pt=0x%02x, pl=%u, pb=", pt, pl);
                        while (pl != 0) {
                                ND_PRINT(" %02x", GET_U_1(p));
                                p++;
                                l--;
                                pl--;
                        }
                        ND_PRINT(", al=%u, a=", al);
                        p += 2;
                        l -= 2;
                        /* p is just beyond al now. */
                        if (l < al) {
                                ND_PRINT(" (not enough space for A)");
                                goto invalid;
                        }
                        while (al != 0) {
                                ND_PRINT(" %02x", GET_U_1(p));
                                p++;
                                l--;
                                al--;
                        }
                }
                num--;
                if (num)
                        ND_PRINT(" ");
        }
        if (l)
                ND_PRINT(" (%u bytes of stray data)", l);
        return;

invalid:
        ND_TCHECK_LEN(p, l);
}

static void
cdp_print_prefixes(netdissect_options *ndo,
                   const u_char * p, u_int l)
{
        if (l % 5) {
                ND_PRINT(" [length %u is not a multiple of 5]", l);
                goto invalid;
        }

        ND_PRINT(" IPv4 Prefixes (%u):", l / 5);

        while (l > 0) {
                ND_PRINT(" %u.%u.%u.%u/%u",
                         GET_U_1(p), GET_U_1(p + 1), GET_U_1(p + 2),
                         GET_U_1(p + 3), GET_U_1(p + 4));
                l -= 5;
                p += 5;
        }
        return;

invalid:
        ND_TCHECK_LEN(p, l);
}