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

 /*
  * 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, [email protected]
  *
  * Reference documentation:
  *    http://www.cisco.com/univercd/cc/td/doc/product/lan/trsrb/frames.htm
  */

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

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

 #include "netdissect-stdinc.h"

 #include <string.h>

 #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_tlv_values[] = {
     { 0x01,             "Device-ID"},
     { 0x02,             "Address"},
     { 0x03,             "Port-ID"},
     { 0x04,             "Capability"},
     { 0x05,             "Version String"},
     { 0x06,             "Platform"},
     { 0x07,             "Prefixes"},
     { 0x08,             "Protocol-Hello option"},
     { 0x09,             "VTP Management Domain"},
     { 0x0a,             "Native VLAN ID"},
     { 0x0b,             "Duplex"},
     { 0x0e,             "ATA-186 VoIP VLAN assignment"},
     { 0x0f,             "ATA-186 VoIP VLAN request"},
     { 0x10,             "power consumption"},
     { 0x11,             "MTU"},
     { 0x12,             "AVVID trust bitmap"},
     { 0x13,             "AVVID untrusted ports CoS"},
     { 0x14,             "System Name"},
     { 0x15,             "System Object ID (not decoded)"},
     { 0x16,             "Management Addresses"},
     { 0x17,             "Physical Location"},
     { 0, NULL}
 };

 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 int cdp_print_addr(netdissect_options *, const u_char *, u_int);
 static int cdp_print_prefixes(netdissect_options *, const u_char *, u_int);
 static unsigned int cdp_get_number(const u_char *, u_int);

 void
 cdp_print(netdissect_options *ndo,
           const u_char *pptr, u_int length, u_int caplen)
 {
 	u_int type, len, i, j;
 	const u_char *tptr;

 	ndo->ndo_protocol = "cdp";
 	if (caplen < CDP_HEADER_LEN) {
 		nd_print_trunc(ndo);
 		return;
 	}

 	tptr = pptr; /* temporary pointer */

 	ND_TCHECK_LEN(tptr, CDP_HEADER_LEN);
 	ND_PRINT("CDPv%u, ttl: %us", EXTRACT_U_1((tptr + CDP_HEADER_VERSION_OFFSET)),
 					   EXTRACT_U_1(tptr + CDP_HEADER_TTL_OFFSET));
 	if (ndo->ndo_vflag)
 		ND_PRINT(", checksum: 0x%04x (unverified), length %u", EXTRACT_BE_U_2(tptr + CDP_HEADER_CHECKSUM_OFFSET), length);
 	tptr += CDP_HEADER_LEN;

 	while (tptr < (pptr+length)) {
 		ND_TCHECK_LEN(tptr, CDP_TLV_HEADER_LEN); /* read out Type and Length */
 		type = EXTRACT_BE_U_2(tptr + CDP_TLV_TYPE_OFFSET);
 		len  = EXTRACT_BE_U_2(tptr + CDP_TLV_LEN_OFFSET); /* object length includes the 4 bytes header length */
 		if (len < CDP_TLV_HEADER_LEN) {
 		    if (ndo->ndo_vflag)
 			ND_PRINT("\n\t%s (0x%02x), TLV length: %u byte%s (too short)",
 			       tok2str(cdp_tlv_values,"unknown field type", type),
 			       type,
 			       len,
 			       PLURAL_SUFFIX(len)); /* plural */
 		    else
 			ND_PRINT(", %s TLV length %u too short",
 			       tok2str(cdp_tlv_values,"unknown field type", type),
 			       len);
 		    break;
 		}
 		tptr += CDP_TLV_HEADER_LEN;
 		len -= CDP_TLV_HEADER_LEN;

 		ND_TCHECK_LEN(tptr, len);

 		if (ndo->ndo_vflag || type == 1) { /* in non-verbose mode just print Device-ID */

 		    if (ndo->ndo_vflag)
 			ND_PRINT("\n\t%s (0x%02x), value length: %u byte%s: ",
 			       tok2str(cdp_tlv_values,"unknown field type", type),
 			       type,
 			       len,
 			       PLURAL_SUFFIX(len)); /* plural */

 		    switch (type) {

 		    case 0x01: /* Device-ID */
 			if (!ndo->ndo_vflag)
 			    ND_PRINT(", Device-ID ");
 			ND_PRINT("'");
 			(void)nd_printn(ndo, tptr, len, NULL);
 			ND_PRINT("'");
 			break;
 		    case 0x02: /* Address */
 			if (cdp_print_addr(ndo, tptr, len) < 0)
 			    goto trunc;
 			break;
 		    case 0x03: /* Port-ID */
 			ND_PRINT("'");
 			(void)nd_printn(ndo, tptr, len, NULL);
 			ND_PRINT("'");
 			break;
 		    case 0x04: /* Capabilities */
 			if (len < 4)
 			    goto trunc;
 			ND_PRINT("(0x%08x): %s",
 			       EXTRACT_BE_U_4(tptr),
 			       bittok2str(cdp_capability_values, "none", EXTRACT_BE_U_4(tptr)));
 			break;
 		    case 0x05: /* Version */
 			ND_PRINT("\n\t  ");
 			for (i=0;i<len;i++) {
 			    j = EXTRACT_U_1(tptr + i);
 			    if (j == '\n') /* lets rework the version string to
 					      get a nice indentation */
 				ND_PRINT("\n\t  ");
 			    else
 				fn_print_char(ndo, j);
 			}
 			break;
 		    case 0x06: /* Platform */
 			ND_PRINT("'");
 			(void)nd_printn(ndo, tptr, len, NULL);
 			ND_PRINT("'");
 			break;
 		    case 0x07: /* Prefixes */
 			if (cdp_print_prefixes(ndo, tptr, len) < 0)
 			    goto trunc;
 			break;
 		    case 0x08: /* Protocol Hello Option - not documented */
 			break;
 		    case 0x09: /* VTP Mgmt Domain  - CDPv2 */
 			ND_PRINT("'");
 			(void)nd_printn(ndo, tptr, len, NULL);
 			ND_PRINT("'");
 			break;
 		    case 0x0a: /* Native VLAN ID - CDPv2 */
 			if (len < 2)
 			    goto trunc;
 			ND_PRINT("%u", EXTRACT_BE_U_2(tptr));
 			break;
 		    case 0x0b: /* Duplex - CDPv2 */
 			if (len < 1)
 			    goto trunc;
 			ND_PRINT("%s", EXTRACT_U_1(tptr) ? "full": "half");
 			break;

 		    /* http://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.
 		     */
 		    case 0x0e: /* ATA-186 VoIP VLAN assignment - incomplete doc. */
 			if (len < 3)
 			    goto trunc;
 			ND_PRINT("app %u, vlan %u", EXTRACT_U_1(tptr), EXTRACT_BE_U_2(tptr + 1));
 			break;
 		    case 0x0f: /* ATA-186 VoIP VLAN request - incomplete doc. */
 			if (len < 2)
 			    goto trunc;
 			if (len == 2)
 			    ND_PRINT("unknown 0x%04x", EXTRACT_BE_U_2(tptr));
 			else
 			    ND_PRINT("app %u, vlan %u", EXTRACT_U_1(tptr), EXTRACT_BE_U_2(tptr + 1));
 			break;
 		    case 0x10: /* Power - not documented */
 			ND_PRINT("%1.2fW", cdp_get_number(tptr, len) / 1000.0);
 			break;
 		    case 0x11: /* MTU - not documented */
 			if (len < 4)
 			    goto trunc;
 			ND_PRINT("%u bytes", EXTRACT_BE_U_4(tptr));
 			break;
 		    case 0x12: /* AVVID trust bitmap - not documented */
 			if (len < 1)
 			    goto trunc;
 			ND_PRINT("0x%02x", EXTRACT_U_1(tptr));
 			break;
 		    case 0x13: /* AVVID untrusted port CoS - not documented */
 			if (len < 1)
 			    goto trunc;
 			ND_PRINT("0x%02x", EXTRACT_U_1(tptr));
 			break;
 		    case 0x14: /* System Name - not documented */
 			ND_PRINT("'");
 			(void)nd_printn(ndo, tptr, len, NULL);
 			ND_PRINT("'");
 			break;
 		    case 0x16: /* System Object ID - not documented */
 			if (cdp_print_addr(ndo, tptr, len) < 0)
 				goto trunc;
 			break;
 		    case 0x17: /* Physical Location - not documented */
 			if (len < 1)
 			    goto trunc;
 			ND_PRINT("0x%02x", EXTRACT_U_1(tptr));
 			if (len > 1) {
 				ND_PRINT("/");
 				(void)nd_printn(ndo, tptr + 1, len - 1, NULL);
 			}
 			break;
 		    default:
 			print_unknown_data(ndo, tptr, "\n\t  ", len);
 			break;
 		    }
 		}
 		tptr = tptr+len;
 	}
 	if (ndo->ndo_vflag < 1)
 	    ND_PRINT(", length %u", caplen);

 	return;
 trunc:
 	nd_print_trunc(ndo);
 }

 /*
  * 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 int
 cdp_print_addr(netdissect_options *ndo,
 	       const u_char * p, u_int l)
 {
 	u_int pt, pl, al, num;
 	const u_char *endp = p + l;
 	static const u_char prot_ipv6[] = {
 		0xaa, 0xaa, 0x03, 0x00, 0x00, 0x00, 0x86, 0xdd
 	};

 	ND_TCHECK_4(p);
 	if (p + 4 > endp)
 		goto trunc;
 	num = EXTRACT_BE_U_4(p);
 	p += 4;

 	while (p < endp && num != 0) {
 		ND_TCHECK_2(p);
 		if (p + 2 > endp)
 			goto trunc;
 		pt = EXTRACT_U_1(p);		/* type of "protocol" field */
 		pl = EXTRACT_U_1(p + 1);	/* length of "protocol" field */
 		p += 2;

 		ND_TCHECK_2(p + pl);
 		if (p + pl + 2 > endp)
 			goto trunc;
 		al = EXTRACT_BE_U_2(p + pl);	/* address length */

 		if (pt == PT_NLPID && pl == 1 && EXTRACT_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 += 3;

 			ND_TCHECK_4(p);
 			if (p + 4 > endp)
 				goto trunc;
 			ND_PRINT("IPv4 (%u) %s", num, ipaddr_string(ndo, p));
 			p += 4;
 		}
 		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 += 10;
 			ND_TCHECK_LEN(p, al);
 			if (p + al > endp)
 				goto trunc;

 			ND_PRINT("IPv6 (%u) %s", num, ip6addr_string(ndo, p));
 			p += al;
 		}
 		else {
 			/*
 			 * Generic case: just print raw data
 			 */
 			ND_TCHECK_LEN(p, pl);
 			if (p + pl > endp)
 				goto trunc;
 			ND_PRINT("pt=0x%02x, pl=%u, pb=", EXTRACT_U_1((p - 2)), pl);
 			while (pl-- > 0) {
 				ND_PRINT(" %02x", EXTRACT_U_1(p));
 				p++;
 			}
 			ND_TCHECK_2(p);
 			if (p + 2 > endp)
 				goto trunc;
 			ND_PRINT(", al=%u, a=", al);
 			p += 2;
 			ND_TCHECK_LEN(p, al);
 			if (p + al > endp)
 				goto trunc;
 			while (al-- > 0) {
 				ND_PRINT(" %02x", EXTRACT_U_1(p));
 				p++;
 			}
 		}
 		num--;
 		if (num)
 			ND_PRINT(" ");
 	}

 	return 0;

 trunc:
 	return -1;
 }


 static int
 cdp_print_prefixes(netdissect_options *ndo,
 		   const u_char * p, u_int l)
 {
 	if (l % 5)
 		goto trunc;

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

 	while (l > 0) {
 		ND_PRINT(" %u.%u.%u.%u/%u",
 			  EXTRACT_U_1(p), EXTRACT_U_1(p + 1), EXTRACT_U_1(p + 2),
 			  EXTRACT_U_1(p + 3), EXTRACT_U_1(p + 4));
 		l -= 5;
 		p += 5;
 	}

 	return 0;

 trunc:
 	return -1;
 }

 /* read in a <n>-byte number, MSB first
  * (of course this can handle max sizeof(int))
  */
 static unsigned int cdp_get_number(const u_char * p, u_int l)
 {
     unsigned int res=0;
     while( l>0 )
     {
 	res = (res<<8) + EXTRACT_U_1(p);
 	p++; l--;
     }
     return res;
 }
	/*
	* 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, [email protected]
	*
	* Reference documentation:
	* http://www.cisco.com/univercd/cc/td/doc/product/lan/trsrb/frames.htm
	*/

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

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

	#include "netdissect-stdinc.h"

	#include <string.h>

	#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_tlv_values[] = {
	{ 0x01, "Device-ID"},
	{ 0x02, "Address"},
	{ 0x03, "Port-ID"},
	{ 0x04, "Capability"},
	{ 0x05, "Version String"},
	{ 0x06, "Platform"},
	{ 0x07, "Prefixes"},
	{ 0x08, "Protocol-Hello option"},
	{ 0x09, "VTP Management Domain"},
	{ 0x0a, "Native VLAN ID"},
	{ 0x0b, "Duplex"},
	{ 0x0e, "ATA-186 VoIP VLAN assignment"},
	{ 0x0f, "ATA-186 VoIP VLAN request"},
	{ 0x10, "power consumption"},
	{ 0x11, "MTU"},
	{ 0x12, "AVVID trust bitmap"},
	{ 0x13, "AVVID untrusted ports CoS"},
	{ 0x14, "System Name"},
	{ 0x15, "System Object ID (not decoded)"},
	{ 0x16, "Management Addresses"},
	{ 0x17, "Physical Location"},
	{ 0, NULL}
	};

	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 int cdp_print_addr(netdissect_options , const u_char , u_int);
	static int cdp_print_prefixes(netdissect_options , const u_char , u_int);
	static unsigned int cdp_get_number(const u_char *, u_int);

	void
	cdp_print(netdissect_options *ndo,
	const u_char *pptr, u_int length, u_int caplen)
	{
	u_int type, len, i, j;
	const u_char *tptr;

	ndo->ndo_protocol = "cdp";
	if (caplen < CDP_HEADER_LEN) {
	nd_print_trunc(ndo);
	return;
	}

	tptr = pptr; /* temporary pointer */

	ND_TCHECK_LEN(tptr, CDP_HEADER_LEN);
	ND_PRINT("CDPv%u, ttl: %us", EXTRACT_U_1((tptr + CDP_HEADER_VERSION_OFFSET)),
	EXTRACT_U_1(tptr + CDP_HEADER_TTL_OFFSET));
	if (ndo->ndo_vflag)
	ND_PRINT(", checksum: 0x%04x (unverified), length %u", EXTRACT_BE_U_2(tptr + CDP_HEADER_CHECKSUM_OFFSET), length);
	tptr += CDP_HEADER_LEN;

	while (tptr < (pptr+length)) {
	ND_TCHECK_LEN(tptr, CDP_TLV_HEADER_LEN); /* read out Type and Length */
	type = EXTRACT_BE_U_2(tptr + CDP_TLV_TYPE_OFFSET);
	len = EXTRACT_BE_U_2(tptr + CDP_TLV_LEN_OFFSET); /* object length includes the 4 bytes header length */
	if (len < CDP_TLV_HEADER_LEN) {
	if (ndo->ndo_vflag)
	ND_PRINT("\n\t%s (0x%02x), TLV length: %u byte%s (too short)",
	tok2str(cdp_tlv_values,"unknown field type", type),
	type,
	len,
	PLURAL_SUFFIX(len)); /* plural */
	else
	ND_PRINT(", %s TLV length %u too short",
	tok2str(cdp_tlv_values,"unknown field type", type),
	len);
	break;
	}
	tptr += CDP_TLV_HEADER_LEN;
	len -= CDP_TLV_HEADER_LEN;

	ND_TCHECK_LEN(tptr, len);

	if (ndo->ndo_vflag \|\| type == 1) { /* in non-verbose mode just print Device-ID */

	if (ndo->ndo_vflag)
	ND_PRINT("\n\t%s (0x%02x), value length: %u byte%s: ",
	tok2str(cdp_tlv_values,"unknown field type", type),
	type,
	len,
	PLURAL_SUFFIX(len)); /* plural */

	switch (type) {

	case 0x01: /* Device-ID */
	if (!ndo->ndo_vflag)
	ND_PRINT(", Device-ID ");
	ND_PRINT("'");
	(void)nd_printn(ndo, tptr, len, NULL);
	ND_PRINT("'");
	break;
	case 0x02: /* Address */
	if (cdp_print_addr(ndo, tptr, len) < 0)
	goto trunc;
	break;
	case 0x03: /* Port-ID */
	ND_PRINT("'");
	(void)nd_printn(ndo, tptr, len, NULL);
	ND_PRINT("'");
	break;
	case 0x04: /* Capabilities */
	if (len < 4)
	goto trunc;
	ND_PRINT("(0x%08x): %s",
	EXTRACT_BE_U_4(tptr),
	bittok2str(cdp_capability_values, "none", EXTRACT_BE_U_4(tptr)));
	break;
	case 0x05: /* Version */
	ND_PRINT("\n\t ");
	for (i=0;i<len;i++) {
	j = EXTRACT_U_1(tptr + i);
	if (j == '\n') /* lets rework the version string to
	get a nice indentation */
	ND_PRINT("\n\t ");
	else
	fn_print_char(ndo, j);
	}
	break;
	case 0x06: /* Platform */
	ND_PRINT("'");
	(void)nd_printn(ndo, tptr, len, NULL);
	ND_PRINT("'");
	break;
	case 0x07: /* Prefixes */
	if (cdp_print_prefixes(ndo, tptr, len) < 0)
	goto trunc;
	break;
	case 0x08: /* Protocol Hello Option - not documented */
	break;
	case 0x09: /* VTP Mgmt Domain - CDPv2 */
	ND_PRINT("'");
	(void)nd_printn(ndo, tptr, len, NULL);
	ND_PRINT("'");
	break;
	case 0x0a: /* Native VLAN ID - CDPv2 */
	if (len < 2)
	goto trunc;
	ND_PRINT("%u", EXTRACT_BE_U_2(tptr));
	break;
	case 0x0b: /* Duplex - CDPv2 */
	if (len < 1)
	goto trunc;
	ND_PRINT("%s", EXTRACT_U_1(tptr) ? "full": "half");
	break;

	/* http://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.
	*/
	case 0x0e: /* ATA-186 VoIP VLAN assignment - incomplete doc. */
	if (len < 3)
	goto trunc;
	ND_PRINT("app %u, vlan %u", EXTRACT_U_1(tptr), EXTRACT_BE_U_2(tptr + 1));
	break;
	case 0x0f: /* ATA-186 VoIP VLAN request - incomplete doc. */
	if (len < 2)
	goto trunc;
	if (len == 2)
	ND_PRINT("unknown 0x%04x", EXTRACT_BE_U_2(tptr));
	else
	ND_PRINT("app %u, vlan %u", EXTRACT_U_1(tptr), EXTRACT_BE_U_2(tptr + 1));
	break;
	case 0x10: /* Power - not documented */
	ND_PRINT("%1.2fW", cdp_get_number(tptr, len) / 1000.0);
	break;
	case 0x11: /* MTU - not documented */
	if (len < 4)
	goto trunc;
	ND_PRINT("%u bytes", EXTRACT_BE_U_4(tptr));
	break;
	case 0x12: /* AVVID trust bitmap - not documented */
	if (len < 1)
	goto trunc;
	ND_PRINT("0x%02x", EXTRACT_U_1(tptr));
	break;
	case 0x13: /* AVVID untrusted port CoS - not documented */
	if (len < 1)
	goto trunc;
	ND_PRINT("0x%02x", EXTRACT_U_1(tptr));
	break;
	case 0x14: /* System Name - not documented */
	ND_PRINT("'");
	(void)nd_printn(ndo, tptr, len, NULL);
	ND_PRINT("'");
	break;
	case 0x16: /* System Object ID - not documented */
	if (cdp_print_addr(ndo, tptr, len) < 0)
	goto trunc;
	break;
	case 0x17: /* Physical Location - not documented */
	if (len < 1)
	goto trunc;
	ND_PRINT("0x%02x", EXTRACT_U_1(tptr));
	if (len > 1) {
	ND_PRINT("/");
	(void)nd_printn(ndo, tptr + 1, len - 1, NULL);
	}
	break;
	default:
	print_unknown_data(ndo, tptr, "\n\t ", len);
	break;
	}
	}
	tptr = tptr+len;
	}
	if (ndo->ndo_vflag < 1)
	ND_PRINT(", length %u", caplen);

	return;
	trunc:
	nd_print_trunc(ndo);
	}

	/*
	* 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 int
	cdp_print_addr(netdissect_options *ndo,
	const u_char * p, u_int l)
	{
	u_int pt, pl, al, num;
	const u_char *endp = p + l;
	static const u_char prot_ipv6[] = {
	0xaa, 0xaa, 0x03, 0x00, 0x00, 0x00, 0x86, 0xdd
	};

	ND_TCHECK_4(p);
	if (p + 4 > endp)
	goto trunc;
	num = EXTRACT_BE_U_4(p);
	p += 4;

	while (p < endp && num != 0) {
	ND_TCHECK_2(p);
	if (p + 2 > endp)
	goto trunc;
	pt = EXTRACT_U_1(p); /* type of "protocol" field */
	pl = EXTRACT_U_1(p + 1); /* length of "protocol" field */
	p += 2;

	ND_TCHECK_2(p + pl);
	if (p + pl + 2 > endp)
	goto trunc;
	al = EXTRACT_BE_U_2(p + pl); /* address length */

	if (pt == PT_NLPID && pl == 1 && EXTRACT_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 += 3;

	ND_TCHECK_4(p);
	if (p + 4 > endp)
	goto trunc;
	ND_PRINT("IPv4 (%u) %s", num, ipaddr_string(ndo, p));
	p += 4;
	}
	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 += 10;
	ND_TCHECK_LEN(p, al);
	if (p + al > endp)
	goto trunc;

	ND_PRINT("IPv6 (%u) %s", num, ip6addr_string(ndo, p));
	p += al;
	}
	else {
	/*
	* Generic case: just print raw data
	*/
	ND_TCHECK_LEN(p, pl);
	if (p + pl > endp)
	goto trunc;
	ND_PRINT("pt=0x%02x, pl=%u, pb=", EXTRACT_U_1((p - 2)), pl);
	while (pl-- > 0) {
	ND_PRINT(" %02x", EXTRACT_U_1(p));
	p++;
	}
	ND_TCHECK_2(p);
	if (p + 2 > endp)
	goto trunc;
	ND_PRINT(", al=%u, a=", al);
	p += 2;
	ND_TCHECK_LEN(p, al);
	if (p + al > endp)
	goto trunc;
	while (al-- > 0) {
	ND_PRINT(" %02x", EXTRACT_U_1(p));
	p++;
	}
	}
	num--;
	if (num)
	ND_PRINT(" ");
	}

	return 0;

	trunc:
	return -1;
	}


	static int
	cdp_print_prefixes(netdissect_options *ndo,
	const u_char * p, u_int l)
	{
	if (l % 5)
	goto trunc;

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

	while (l > 0) {
	ND_PRINT(" %u.%u.%u.%u/%u",
	EXTRACT_U_1(p), EXTRACT_U_1(p + 1), EXTRACT_U_1(p + 2),
	EXTRACT_U_1(p + 3), EXTRACT_U_1(p + 4));
	l -= 5;
	p += 5;
	}

	return 0;

	trunc:
	return -1;
	}

	/* read in a <n>-byte number, MSB first
	* (of course this can handle max sizeof(int))
	*/
	static unsigned int cdp_get_number(const u_char * p, u_int l)
	{
	unsigned int res=0;
	while( l>0 )
	{
	res = (res<<8) + EXTRACT_U_1(p);
	p++; l--;
	}
	return res;
	}