xref: /freebsd/contrib/tcpdump/print-dhcp6.c (revision 27df3f5dddcc52e19be97c5e876161208987d4f1)

/*
 * Copyright (C) 1998 and 1999 WIDE Project.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the project 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 BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */
/*
 * RFC3315: DHCPv6
 * supported DHCPv6 options:
 *  RFC3319,
 *  RFC3633,
 *  RFC3646,
 *  RFC3898,
 *  RFC4075,
 *  RFC4242,
 *  RFC4280,
 */

#ifndef lint
static const char rcsid[] _U_ =
    "@(#) $Header: /tcpdump/master/tcpdump/print-dhcp6.c,v 1.37 2008-02-06 10:26:09 guy Exp $";
#endif

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

#include <tcpdump-stdinc.h>

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

#include "interface.h"
#include "addrtoname.h"
#include "extract.h"

/* lease duration */
#define DHCP6_DURATITION_INFINITE 0xffffffff

/* Error Values */
#define DH6ERR_FAILURE		16
#define DH6ERR_AUTHFAIL		17
#define DH6ERR_POORLYFORMED	18
#define DH6ERR_UNAVAIL		19
#define DH6ERR_OPTUNAVAIL	20

/* Message type */
#define DH6_SOLICIT	1
#define DH6_ADVERTISE	2
#define DH6_REQUEST	3
#define DH6_CONFIRM	4
#define DH6_RENEW	5
#define DH6_REBIND	6
#define DH6_REPLY	7
#define DH6_RELEASE	8
#define DH6_DECLINE	9
#define DH6_RECONFIGURE	10
#define DH6_INFORM_REQ	11
#define DH6_RELAY_FORW	12
#define DH6_RELAY_REPLY	13
#define DH6_LEASEQUERY	14
#define DH6_LQ_REPLY	15

/* DHCP6 base packet format */
struct dhcp6 {
	union {
		u_int8_t m;
		u_int32_t x;
	} dh6_msgtypexid;
	/* options follow */
};
#define dh6_msgtype	dh6_msgtypexid.m
#define dh6_xid		dh6_msgtypexid.x
#define DH6_XIDMASK	0x00ffffff

/* DHCPv6 relay messages */
struct dhcp6_relay {
	u_int8_t dh6relay_msgtype;
	u_int8_t dh6relay_hcnt;
	u_int8_t dh6relay_linkaddr[16];	/* XXX: badly aligned */
	u_int8_t dh6relay_peeraddr[16];
	/* options follow */
};

/* options */
#define DH6OPT_CLIENTID	1
#define DH6OPT_SERVERID	2
#define DH6OPT_IA_NA 3
#define DH6OPT_IA_TA 4
#define DH6OPT_IA_ADDR 5
#define DH6OPT_ORO 6
#define DH6OPT_PREFERENCE 7
#  define DH6OPT_PREF_MAX 255
#define DH6OPT_ELAPSED_TIME 8
#define DH6OPT_RELAY_MSG 9
/*#define DH6OPT_SERVER_MSG 10 deprecated */
#define DH6OPT_AUTH 11
#  define DH6OPT_AUTHPROTO_DELAYED 2
#  define DH6OPT_AUTHPROTO_RECONFIG 3
#  define DH6OPT_AUTHALG_HMACMD5 1
#  define DH6OPT_AUTHRDM_MONOCOUNTER 0
#  define DH6OPT_AUTHRECONFIG_KEY 1
#  define DH6OPT_AUTHRECONFIG_HMACMD5 2
#define DH6OPT_UNICAST 12
#define DH6OPT_STATUS_CODE 13
#  define DH6OPT_STCODE_SUCCESS 0
#  define DH6OPT_STCODE_UNSPECFAIL 1
#  define DH6OPT_STCODE_NOADDRAVAIL 2
#  define DH6OPT_STCODE_NOBINDING 3
#  define DH6OPT_STCODE_NOTONLINK 4
#  define DH6OPT_STCODE_USEMULTICAST 5
#  define DH6OPT_STCODE_NOPREFIXAVAIL 6
#  define DH6OPT_STCODE_UNKNOWNQUERYTYPE 7
#  define DH6OPT_STCODE_MALFORMEDQUERY 8
#  define DH6OPT_STCODE_NOTCONFIGURED 9
#  define DH6OPT_STCODE_NOTALLOWED 10
#define DH6OPT_RAPID_COMMIT 14
#define DH6OPT_USER_CLASS 15
#define DH6OPT_VENDOR_CLASS 16
#define DH6OPT_VENDOR_OPTS 17
#define DH6OPT_INTERFACE_ID 18
#define DH6OPT_RECONF_MSG 19
#define DH6OPT_RECONF_ACCEPT 20
#define DH6OPT_SIP_SERVER_D 21
#define DH6OPT_SIP_SERVER_A 22
#define DH6OPT_DNS 23
#define DH6OPT_DNSNAME 24
#define DH6OPT_IA_PD 25
#define DH6OPT_IA_PD_PREFIX 26
#define DH6OPT_NIS_SERVERS 27
#define DH6OPT_NISP_SERVERS 28
#define DH6OPT_NIS_NAME 29
#define DH6OPT_NISP_NAME 30
#define DH6OPT_NTP_SERVERS 31
#define DH6OPT_LIFETIME 32
#define DH6OPT_BCMCS_SERVER_D 33
#define DH6OPT_BCMCS_SERVER_A 34
#define DH6OPT_GEOCONF_CIVIC 36
#define DH6OPT_REMOTE_ID 37
#define DH6OPT_SUBSCRIBER_ID 38
#define DH6OPT_CLIENT_FQDN 39
#define DH6OPT_PANA_AGENT 40
#define DH6OPT_NEW_POSIX_TIMEZONE 41
#define DH6OPT_NEW_TZDB_TIMEZONE 42
#define DH6OPT_ERO 43
#define DH6OPT_LQ_QUERY 44
#define DH6OPT_CLIENT_DATA 45
#define DH6OPT_CLT_TIME 46
#define DH6OPT_LQ_RELAY_DATA 47
#define DH6OPT_LQ_CLIENT_LINK 48

struct dhcp6opt {
	u_int16_t dh6opt_type;
	u_int16_t dh6opt_len;
	/* type-dependent data follows */
};

static const char *
dhcp6opt_name(int type)
{
	static char genstr[sizeof("opt_65535") + 1]; /* XXX thread unsafe */

	if (type > 65535)
		return "INVALID-option";

	switch(type) {
	case DH6OPT_CLIENTID:
		return "client-ID";
	case DH6OPT_SERVERID:
		return "server-ID";
	case DH6OPT_IA_NA:
		return "IA_NA";
	case DH6OPT_IA_TA:
		return "IA_TA";
	case DH6OPT_IA_ADDR:
		return "IA_ADDR";
	case DH6OPT_ORO:
		return "option-request";
	case DH6OPT_PREFERENCE:
		return "preference";
	case DH6OPT_ELAPSED_TIME:
		return "elapsed-time";
	case DH6OPT_RELAY_MSG:
		return "relay-message";
	case DH6OPT_AUTH:
		return "authentication";
	case DH6OPT_UNICAST:
		return "server-unicast";
	case DH6OPT_STATUS_CODE:
		return "status-code";
	case DH6OPT_RAPID_COMMIT:
		return "rapid-commit";
	case DH6OPT_USER_CLASS:
		return "user-class";
	case DH6OPT_VENDOR_CLASS:
		return "vendor-class";
	case DH6OPT_VENDOR_OPTS:
		return "vendor-specific-info";
	case DH6OPT_INTERFACE_ID:
		return "interface-ID";
	case DH6OPT_RECONF_MSG:
		return "reconfigure-message";
	case DH6OPT_RECONF_ACCEPT:
		return "reconfigure-accept";
	case DH6OPT_SIP_SERVER_D:
		return "SIP-servers-domain";
	case DH6OPT_SIP_SERVER_A:
		return "SIP-servers-address";
	case DH6OPT_DNS:
		return "DNS";
	case DH6OPT_DNSNAME:
		return "DNS-name";
	case DH6OPT_IA_PD:
		return "IA_PD";
	case DH6OPT_IA_PD_PREFIX:
		return "IA_PD-prefix";
	case DH6OPT_NTP_SERVERS:
		return "NTP-Server";
	case DH6OPT_LIFETIME:
		return "lifetime";
	case DH6OPT_NIS_SERVERS:
		return "NIS-server";
	case DH6OPT_NISP_SERVERS:
		return "NIS+-server";
	case DH6OPT_NIS_NAME:
		return "NIS-domain-name";
	case DH6OPT_NISP_NAME:
		return "NIS+-domain-name";
	case DH6OPT_BCMCS_SERVER_D:
		return "BCMCS-domain-name";
	case DH6OPT_BCMCS_SERVER_A:
		return "BCMCS-server";
	case DH6OPT_GEOCONF_CIVIC:
		return "Geoconf-Civic";
	case DH6OPT_REMOTE_ID:
		return "Remote-ID";
	case DH6OPT_SUBSCRIBER_ID:
		return "Subscriber-ID";
	case DH6OPT_CLIENT_FQDN:
		return "Client-FQDN";
	case DH6OPT_PANA_AGENT:
		return "PANA-agent";
	case DH6OPT_NEW_POSIX_TIMEZONE:
		return "POSIX-timezone";
	case DH6OPT_NEW_TZDB_TIMEZONE:
		return "POSIX-tz-database";
	case DH6OPT_ERO:
		return "Echo-request-option";
	case DH6OPT_LQ_QUERY:
		return "Lease-query";
	case DH6OPT_CLIENT_DATA:
		return "LQ-client-data";
	case DH6OPT_CLT_TIME:
		return "Clt-time";
	case DH6OPT_LQ_RELAY_DATA:
		return "LQ-relay-data";
	case DH6OPT_LQ_CLIENT_LINK:
		return "LQ-client-link";
	default:
		snprintf(genstr, sizeof(genstr), "opt_%d", type);
		return(genstr);
	}
}

static const char *
dhcp6stcode(int code)
{
	static char genstr[sizeof("code255") + 1]; /* XXX thread unsafe */

	if (code > 255)
		return "INVALID code";

	switch(code) {
	case DH6OPT_STCODE_SUCCESS:
		return "success";
	case DH6OPT_STCODE_UNSPECFAIL:
		return "unspec failure";
	case DH6OPT_STCODE_NOADDRAVAIL:
		return "no addresses";
	case DH6OPT_STCODE_NOBINDING:
		return "no binding";
	case DH6OPT_STCODE_NOTONLINK:
		return "not on-link";
	case DH6OPT_STCODE_USEMULTICAST:
		return "use multicast";
	case DH6OPT_STCODE_NOPREFIXAVAIL:
		return "no prefixes";
	case DH6OPT_STCODE_UNKNOWNQUERYTYPE:
		return "unknown query type";
	case DH6OPT_STCODE_MALFORMEDQUERY:
		return "malformed query";
	case DH6OPT_STCODE_NOTCONFIGURED:
		return "not configured";
	case DH6OPT_STCODE_NOTALLOWED:
		return "not allowed";
	default:
		snprintf(genstr, sizeof(genstr), "code%d", code);
		return(genstr);
	}
}

static void
dhcp6opt_print(const u_char *cp, const u_char *ep)
{
	struct dhcp6opt *dh6o;
	u_char *tp;
	size_t i;
	u_int16_t opttype;
	size_t optlen;
	u_int8_t auth_proto;
	u_int authinfolen, authrealmlen;

	if (cp == ep)
		return;
	while (cp < ep) {
		if (ep < cp + sizeof(*dh6o))
			goto trunc;
		dh6o = (struct dhcp6opt *)cp;
		optlen = EXTRACT_16BITS(&dh6o->dh6opt_len);
		if (ep < cp + sizeof(*dh6o) + optlen)
			goto trunc;
		opttype = EXTRACT_16BITS(&dh6o->dh6opt_type);
		printf(" (%s", dhcp6opt_name(opttype));
		switch (opttype) {
		case DH6OPT_CLIENTID:
		case DH6OPT_SERVERID:
			if (optlen < 2) {
				/*(*/
				printf(" ?)");
				break;
			}
			tp = (u_char *)(dh6o + 1);
			switch (EXTRACT_16BITS(tp)) {
			case 1:
				if (optlen >= 2 + 6) {
					printf(" hwaddr/time type %u time %u ",
					    EXTRACT_16BITS(&tp[2]),
					    EXTRACT_32BITS(&tp[4]));
					for (i = 8; i < optlen; i++)
						printf("%02x", tp[i]);
					/*(*/
					printf(")");
				} else {
					/*(*/
					printf(" ?)");
				}
				break;
			case 2:
				if (optlen >= 2 + 8) {
					printf(" vid ");
					for (i = 2; i < 2 + 8; i++)
						printf("%02x", tp[i]);
					/*(*/
					printf(")");
				} else {
					/*(*/
					printf(" ?)");
				}
				break;
			case 3:
				if (optlen >= 2 + 2) {
					printf(" hwaddr type %u ",
					    EXTRACT_16BITS(&tp[2]));
					for (i = 4; i < optlen; i++)
						printf("%02x", tp[i]);
					/*(*/
					printf(")");
				} else {
					/*(*/
					printf(" ?)");
				}
				break;
			default:
				printf(" type %d)", EXTRACT_16BITS(tp));
				break;
			}
			break;
		case DH6OPT_IA_ADDR:
			if (optlen < 24) {
				/*(*/
				printf(" ?)");
				break;
			}
			tp = (u_char *)(dh6o + 1);
			printf(" %s", ip6addr_string(&tp[0]));
			printf(" pltime:%u vltime:%u",
			    EXTRACT_32BITS(&tp[16]),
			    EXTRACT_32BITS(&tp[20]));
			if (optlen > 24) {
				/* there are sub-options */
				dhcp6opt_print(tp + 24, tp + 24 + optlen);
			}
			printf(")");
			break;
		case DH6OPT_ORO:
		case DH6OPT_ERO:
			if (optlen % 2) {
				printf(" ?)");
				break;
			}
			tp = (u_char *)(dh6o + 1);
			for (i = 0; i < optlen; i += 2) {
				printf(" %s",
				    dhcp6opt_name(EXTRACT_16BITS(&tp[i])));
			}
			printf(")");
			break;
		case DH6OPT_PREFERENCE:
			if (optlen != 1) {
				printf(" ?)");
				break;
			}
			tp = (u_char *)(dh6o + 1);
			printf(" %d)", *tp);
			break;
		case DH6OPT_ELAPSED_TIME:
			if (optlen != 2) {
				printf(" ?)");
				break;
			}
			tp = (u_char *)(dh6o + 1);
			printf(" %d)", EXTRACT_16BITS(tp));
			break;
		case DH6OPT_RELAY_MSG:
			printf(" (");
			tp = (u_char *)(dh6o + 1);
			dhcp6_print(tp, optlen);
			printf(")");
			break;
		case DH6OPT_AUTH:
			if (optlen < 11) {
				printf(" ?)");
				break;
			}
			tp = (u_char *)(dh6o + 1);
			auth_proto = *tp;
			switch (auth_proto) {
			case DH6OPT_AUTHPROTO_DELAYED:
				printf(" proto: delayed");
				break;
			case DH6OPT_AUTHPROTO_RECONFIG:
				printf(" proto: reconfigure");
				break;
			default:
				printf(" proto: %d", auth_proto);
				break;
			}
			tp++;
			switch (*tp) {
			case DH6OPT_AUTHALG_HMACMD5:
				/* XXX: may depend on the protocol */
				printf(", alg: HMAC-MD5");
				break;
			default:
				printf(", alg: %d", *tp);
				break;
			}
			tp++;
			switch (*tp) {
			case DH6OPT_AUTHRDM_MONOCOUNTER:
				printf(", RDM: mono");
				break;
			default:
				printf(", RDM: %d", *tp);
				break;
			}
			tp++;
			printf(", RD:");
			for (i = 0; i < 4; i++, tp += 2)
				printf(" %04x", EXTRACT_16BITS(tp));

			/* protocol dependent part */
			authinfolen = optlen - 11;
			switch (auth_proto) {
			case DH6OPT_AUTHPROTO_DELAYED:
				if (authinfolen == 0)
					break;
				if (authinfolen < 20) {
					printf(" ??");
					break;
				}
				authrealmlen = authinfolen - 20;
				if (authrealmlen > 0) {
					printf(", realm: ");
				}
				for (i = 0; i < authrealmlen; i++, tp++)
					printf("%02x", *tp);
				printf(", key ID: %08x", EXTRACT_32BITS(tp));
				tp += 4;
				printf(", HMAC-MD5:");
				for (i = 0; i < 4; i++, tp+= 4)
					printf(" %08x", EXTRACT_32BITS(tp));
				break;
			case DH6OPT_AUTHPROTO_RECONFIG:
				if (authinfolen != 17) {
					printf(" ??");
					break;
				}
				switch (*tp++) {
				case DH6OPT_AUTHRECONFIG_KEY:
					printf(" reconfig-key");
					break;
				case DH6OPT_AUTHRECONFIG_HMACMD5:
					printf(" type: HMAC-MD5");
					break;
				default:
					printf(" type: ??");
					break;
				}
				printf(" value:");
				for (i = 0; i < 4; i++, tp+= 4)
					printf(" %08x", EXTRACT_32BITS(tp));
				break;
			default:
				printf(" ??");
				break;
			}

			printf(")");
			break;
		case DH6OPT_RAPID_COMMIT: /* nothing todo */
			printf(")");
			break;
		case DH6OPT_INTERFACE_ID:
		case DH6OPT_SUBSCRIBER_ID:
			/*
			 * Since we cannot predict the encoding, print hex dump
			 * at most 10 characters.
			 */
			tp = (u_char *)(dh6o + 1);
			printf(" ");
			for (i = 0; i < optlen && i < 10; i++)
				printf("%02x", tp[i]);
			printf("...)");
			break;
		case DH6OPT_RECONF_MSG:
			tp = (u_char *)(dh6o + 1);
			switch (*tp) {
			case DH6_RENEW:
				printf(" for renew)");
				break;
			case DH6_INFORM_REQ:
				printf(" for inf-req)");
				break;
			default:
				printf(" for ?\?\?(%02x))", *tp);
				break;
			}
			break;
		case DH6OPT_RECONF_ACCEPT: /* nothing todo */
			printf(")");
			break;
		case DH6OPT_SIP_SERVER_A:
		case DH6OPT_DNS:
		case DH6OPT_NTP_SERVERS:
		case DH6OPT_NIS_SERVERS:
		case DH6OPT_NISP_SERVERS:
		case DH6OPT_BCMCS_SERVER_A:
		case DH6OPT_PANA_AGENT:
		case DH6OPT_LQ_CLIENT_LINK:
			if (optlen % 16) {
				printf(" ?)");
				break;
			}
			tp = (u_char *)(dh6o + 1);
			for (i = 0; i < optlen; i += 16)
				printf(" %s", ip6addr_string(&tp[i]));
			printf(")");
			break;
		case DH6OPT_STATUS_CODE:
			if (optlen < 2) {
				printf(" ?)");
				break;
			}
			tp = (u_char *)(dh6o + 1);
			printf(" %s)", dhcp6stcode(EXTRACT_16BITS(&tp[0])));
			break;
		case DH6OPT_IA_NA:
		case DH6OPT_IA_PD:
			if (optlen < 12) {
				printf(" ?)");
				break;
			}
			tp = (u_char *)(dh6o + 1);
			printf(" IAID:%u T1:%u T2:%u",
			    EXTRACT_32BITS(&tp[0]),
			    EXTRACT_32BITS(&tp[4]),
			    EXTRACT_32BITS(&tp[8]));
			if (optlen > 12) {
				/* there are sub-options */
				dhcp6opt_print(tp + 12, tp + 12 + optlen);
			}
			printf(")");
			break;
		case DH6OPT_IA_TA:
			if (optlen < 4) {
				printf(" ?)");
				break;
			}
			tp = (u_char *)(dh6o + 1);
			printf(" IAID:%u", EXTRACT_32BITS(tp));
			if (optlen > 4) {
				/* there are sub-options */
				dhcp6opt_print(tp + 4, tp + 4 + optlen);
			}
			printf(")");
			break;
		case DH6OPT_IA_PD_PREFIX:
			if (optlen < 25) {
				printf(" ?)");
				break;
			}
			tp = (u_char *)(dh6o + 1);
			printf(" %s/%d", ip6addr_string(&tp[9]), tp[8]);
			printf(" pltime:%u vltime:%u",
			    EXTRACT_32BITS(&tp[0]),
			    EXTRACT_32BITS(&tp[4]));
			if (optlen > 25) {
				/* there are sub-options */
				dhcp6opt_print(tp + 25, tp + 25 + optlen);
			}
			printf(")");
			break;
		case DH6OPT_LIFETIME:
		case DH6OPT_CLT_TIME:
			if (optlen != 4) {
				printf(" ?)");
				break;
			}
			tp = (u_char *)(dh6o + 1);
			printf(" %d)", EXTRACT_32BITS(tp));
			break;
		case DH6OPT_REMOTE_ID:
			if (optlen < 4) {
				printf(" ?)");
				break;
			}
			tp = (u_char *)(dh6o + 1);
			printf(" %d ", EXTRACT_32BITS(tp));
			/*
			 * Print hex dump first 10 characters.
			 */
			for (i = 4; i < optlen && i < 14; i++)
				printf("%02x", tp[i]);
			printf("...)");
			break;
		case DH6OPT_LQ_QUERY:
			if (optlen < 17) {
				printf(" ?)");
				break;
			}
			tp = (u_char *)(dh6o + 1);
			switch (*tp) {
			case 1:
				printf(" by-address");
				break;
			case 2:
				printf(" by-clientID");
				break;
			default:
				printf(" type_%d", (int)*tp);
				break;
			}
			printf(" %s", ip6addr_string(&tp[1]));
			if (optlen > 17) {
				/* there are query-options */
				dhcp6opt_print(tp + 17, tp + optlen);
			}
			printf(")");
			break;
		case DH6OPT_CLIENT_DATA:
			tp = (u_char *)(dh6o + 1);
			if (optlen > 0) {
				/* there are encapsulated options */
				dhcp6opt_print(tp, tp + optlen);
			}
			printf(")");
			break;
		case DH6OPT_LQ_RELAY_DATA:
			if (optlen < 16) {
				printf(" ?)");
				break;
			}
			tp = (u_char *)(dh6o + 1);
			printf(" %s ", ip6addr_string(&tp[0]));
			/*
			 * Print hex dump first 10 characters.
			 */
			for (i = 16; i < optlen && i < 26; i++)
				printf("%02x", tp[i]);
			printf("...)");
			break;
		default:
			printf(")");
			break;
		}

		cp += sizeof(*dh6o) + optlen;
	}
	return;

trunc:
	printf("[|dhcp6ext]");
}

/*
 * Print dhcp6 packets
 */
void
dhcp6_print(const u_char *cp, u_int length)
{
	struct dhcp6 *dh6;
	struct dhcp6_relay *dh6relay;
	const u_char *ep;
	u_char *extp;
	const char *name;

	printf("dhcp6");

	ep = (u_char *)snapend;
	if (cp + length < ep)
		ep = cp + length;

	dh6 = (struct dhcp6 *)cp;
	dh6relay = (struct dhcp6_relay *)cp;
	TCHECK(dh6->dh6_xid);
	switch (dh6->dh6_msgtype) {
	case DH6_SOLICIT:
		name = "solicit";
		break;
	case DH6_ADVERTISE:
		name = "advertise";
		break;
	case DH6_REQUEST:
		name = "request";
		break;
	case DH6_CONFIRM:
		name = "confirm";
		break;
	case DH6_RENEW:
		name = "renew";
		break;
	case DH6_REBIND:
		name = "rebind";
		break;
	case DH6_REPLY:
		name = "reply";
		break;
	case DH6_RELEASE:
		name = "release";
		break;
	case DH6_DECLINE:
		name = "decline";
		break;
	case DH6_RECONFIGURE:
		name = "reconfigure";
		break;
	case DH6_INFORM_REQ:
		name= "inf-req";
		break;
	case DH6_RELAY_FORW:
		name= "relay-fwd";
		break;
	case DH6_RELAY_REPLY:
		name= "relay-reply";
		break;
	case DH6_LEASEQUERY:
		name= "leasequery";
		break;
	case DH6_LQ_REPLY:
		name= "leasequery-reply";
		break;
	default:
		name = NULL;
		break;
	}

	if (!vflag) {
		if (name)
			printf(" %s", name);
		else if (dh6->dh6_msgtype != DH6_RELAY_FORW &&
		    dh6->dh6_msgtype != DH6_RELAY_REPLY) {
			printf(" msgtype-%u", dh6->dh6_msgtype);
		}
		return;
	}

	/* XXX relay agent messages have to be handled differently */

	if (name)
		printf(" %s (", name);	/*)*/
	else
		printf(" msgtype-%u (", dh6->dh6_msgtype);	/*)*/
	if (dh6->dh6_msgtype != DH6_RELAY_FORW &&
	    dh6->dh6_msgtype != DH6_RELAY_REPLY) {
		printf("xid=%x", EXTRACT_32BITS(&dh6->dh6_xid) & DH6_XIDMASK);
		extp = (u_char *)(dh6 + 1);
		dhcp6opt_print(extp, ep);
	} else {		/* relay messages */
		struct in6_addr addr6;

		TCHECK(dh6relay->dh6relay_peeraddr);

		memcpy(&addr6, dh6relay->dh6relay_linkaddr, sizeof (addr6));
		printf("linkaddr=%s", ip6addr_string(&addr6));

		memcpy(&addr6, dh6relay->dh6relay_peeraddr, sizeof (addr6));
		printf(" peeraddr=%s", ip6addr_string(&addr6));

		dhcp6opt_print((u_char *)(dh6relay + 1), ep);
	}
	/*(*/
	printf(")");
	return;

trunc:
	printf("[|dhcp6]");
}