path: root/client/dhc6.c

/* dhc6.c - DHCPv6 client routines. */

/*
 * Copyright (c) 2006-2007 by Internet Systems Consortium, Inc. ("ISC")
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
 * OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 *
 *   Internet Systems Consortium, Inc.
 *   950 Charter Street
 *   Redwood City, CA 94063
 *   <info@isc.org>
 *   http://www.isc.org/
 */

#include "dhcpd.h"

#ifdef DHCPv6

struct sockaddr_in6 DHCPv6DestAddr;

/* Option definition structures that are used by the software - declared
 * here once and assigned at startup to save lookups.
 */
struct option *clientid_option = NULL;
struct option *elapsed_option = NULL;
struct option *ia_na_option = NULL;
struct option *iaaddr_option = NULL;
struct option *oro_option = NULL;

static struct dhc6_lease *dhc6_dup_lease(struct dhc6_lease *lease,
					 const char *file, int line);
static struct dhc6_ia *dhc6_dup_ia(struct dhc6_ia *ia, 
				   const char *file, int line);
static struct dhc6_addr *dhc6_dup_addr(struct dhc6_addr *addr,
				       const char *file, int line);
static void dhc6_ia_destroy(struct dhc6_ia *ia, const char *file, int line);
static isc_result_t dhc6_parse_ia_na(struct dhc6_ia **pia,
				     struct packet *packet,
				     struct option_state *options);
static isc_result_t dhc6_parse_addrs(struct dhc6_addr **paddr,
				     struct packet *packet,
				     struct option_state *options);
static struct dhc6_ia *find_ia(struct dhc6_ia *head, const char *id);
static struct dhc6_addr *find_addr(struct dhc6_addr *head,
				   struct iaddr *address);
void init_handler(struct packet *packet, struct client_state *client);
void do_init6(void *input);
void do_confirm6(void *input);
void reply_handler(struct packet *packet, struct client_state *client);
static isc_result_t dhc6_add_ia(struct client_state *client,
				struct data_string *packet,
				struct dhc6_lease *lease,
                                u_int8_t message);
static void dhc6_merge_lease(struct dhc6_lease *src, struct dhc6_lease *dst);
void do_select6(void *input);
void do_refresh6(void *input);
static void do_release6(void *input);
static void start_bound(struct client_state *client);
void bound_handler(struct packet *packet, struct client_state *client);
void start_renew6(void *input);
void start_rebind6(void *input);
void do_depref(void *input);
void do_expire(void *input);
static void make_client6_options(struct client_state *client,
				 struct option_state **op,
				 struct dhc6_lease *lease, u_int8_t message);
static void script_write_params6(struct client_state *client, 
				 const char *prefix,
				 struct option_state *options);

/* The "best" default DUID, since we cannot predict any information
 * about the system (such as whether or not the hardware addresses are
 * integrated into the motherboard or similar), is the "LLT", link local
 * plus time, DUID.
 *
 * Once generated, this duid is stored into the state database, and
 * retained across restarts.
 *
 * For the time being, there is probably a different state database for
 * every daemon, so this winds up being a per-interface identifier...which
 * is not how it is intended.  Upcoming rearchitecting the client should
 * address this "one daemon model."
 */
void
form_duid(struct data_string *duid, const char *file, int line)
{
	struct interface_info *ip;
	int len;

	/* For now, just use the first interface on the list. */
	ip = interfaces;

	if (ip == NULL)
		log_fatal("Impossible condition at %s:%d.", MDL);

	if ((ip->hw_address.hlen == 0) ||
	    (ip->hw_address.hlen > sizeof(ip->hw_address.hbuf)))
		log_fatal("Impossible hardware address length at %s:%d.", MDL);

	/* 2 bytes for the 'duid type' field.
	 * 2 bytes for the 'htype' field.
	 * 4 bytes for the 'current time'.
	 * enough bytes for the hardware address (note that hw_address has
	 * the 'htype' on byte zero).
	 */
	len = 8 + (ip->hw_address.hlen - 1);
	if (!buffer_allocate(&duid->buffer, len, MDL))
		log_fatal("no memory for default DUID!");
	duid->data = duid->buffer->data;
	duid->len = len;

	/* Basic Link Local Address type of DUID. */
	putUShort(duid->buffer->data, DUID_LLT);
	putUShort(duid->buffer->data + 2, ip->hw_address.hbuf[0]);
	putULong(duid->buffer->data + 4, cur_time);
	memcpy(duid->buffer->data + 8, ip->hw_address.hbuf + 1,
	       ip->hw_address.hlen - 1);
}

/* Assign DHCPv6 port numbers as a client.
 */
void
dhcpv6_client_assignments(void)
{
	struct servent *ent;
	unsigned code;

	if (path_dhclient_pid == NULL)
		path_dhclient_pid = _PATH_DHCLIENT6_PID;
	if (path_dhclient_db == NULL)
		path_dhclient_db = _PATH_DHCLIENT6_DB;

	if (local_port == 0) {
		ent = getservbyname("dhcpv6-client", "udp");
		if (ent == NULL)
			local_port = htons(546);
		else
			local_port = ent->s_port;
	}

	if (remote_port == 0) {
		ent = getservbyname("dhcpv6-server", "udp");
		if (ent == NULL)
			remote_port = htons(547);
		else
			remote_port = ent->s_port;
	}

	memset(&DHCPv6DestAddr, 0, sizeof(DHCPv6DestAddr));
	DHCPv6DestAddr.sin6_family = AF_INET6;
	DHCPv6DestAddr.sin6_port = remote_port;
	inet_pton(AF_INET6, All_DHCP_Relay_Agents_and_Servers,
		  &DHCPv6DestAddr.sin6_addr);

	code = D6O_CLIENTID;
	if (!option_code_hash_lookup(&clientid_option,
				     dhcpv6_universe.code_hash, &code, 0, MDL))
		log_fatal("Unable to find the CLIENTID option definition.");

	code = D6O_ELAPSED_TIME;
	if (!option_code_hash_lookup(&elapsed_option,
				     dhcpv6_universe.code_hash, &code, 0, MDL))
		log_fatal("Unable to find the ELAPSED_TIME option definition.");

	code = D6O_IA_NA;
	if (!option_code_hash_lookup(&ia_na_option, dhcpv6_universe.code_hash,
				     &code, 0, MDL))
		log_fatal("Unable to find the IA_NA option definition.");

	code = D6O_IAADDR;
	if (!option_code_hash_lookup(&iaaddr_option, dhcpv6_universe.code_hash,
				     &code, 0, MDL))
		log_fatal("Unable to find the IAADDR option definition.");

	code = D6O_ORO;
	if (!option_code_hash_lookup(&oro_option, dhcpv6_universe.code_hash,
				     &code, 0, MDL))
		log_fatal("Unable to find the ORO option definition.");

#ifndef __CYGWIN32__ /* XXX */
	endservent();
#endif
}

/* Instead of implementing RFC3315 RAND (section 14) as a float "between"
 * -0.1 and 0.1 non-inclusive, we implement it as an integer.
 *
 * The result is expected to follow this table:
 *
 *		split range answer
 *		    - ERROR -		      base <= 0
 *		0	1   0..0	 1 <= base <= 10
 *		1	3  -1..1	11 <= base <= 20
 *		2	5  -2..2	21 <= base <= 30
 *		3	7  -3..3	31 <= base <= 40
 *		...
 *
 * XXX: For this to make sense, we really need to do timing on a
 * XXX: usec scale...we currently can assume zero for any value less than
 * XXX: 11, which are very common in early stages of transmission for most
 * XXX: messages.
 */
static TIME
dhc6_rand(TIME base)
{
	TIME rval;
	TIME range;
	TIME split;

	/* A zero or less timeout is a bad thing...we don't want to
	 * DHCP-flood anyone.
	 */
	if (base <= 0)
		log_fatal("Impossible condition at %s:%d.", MDL);

	/* The first thing we do is count how many random integers we want
	 * in either direction (best thought of as the maximum negative
	 * integer, as we will subtract this potentially from a random 0).
	 */
	split = (base - 1) / 10;

	/* Don't bother with the rest of the math if we know we'll get 0. */
	if (split == 0)
		return 0;

	/* Then we count the total number of integers in this set.  This
	 * is twice the number of integers in positive and negative
	 * directions, plus zero (-1, 0, 1 is 3, -2..2 adds 2 to 5, so forth).
	 */
	range = (split * 2) + 1;

	/* Take a random number from [0..(range-1)]. */
	rval = random();
	rval %= range;

	/* Offset it to uncover potential negative values. */
	rval -= split;

	return rval;
}

/* Get a new dhcpv6_transaction_id and store it to the client state. */
static void
dhc6_new_xid(struct client_state *client)
{
	int xid;

	if (RAND_MAX >= 0x00ffffff)
		xid = random();
	else if (RAND_MAX >= 0x0000ffff)
		xid = (random() << 16) | random();
	else
		xid = (random() << 24) | (random() << 16) | random();

	client->dhcpv6_transaction_id[0] = (xid >> 16) & 0xff;
	client->dhcpv6_transaction_id[1] = (xid >>  8) & 0xff;
	client->dhcpv6_transaction_id[2] =  xid        & 0xff;
}

/* Set RT from initial RT. */
static void
dhc6_retrans_init(struct client_state *client)
{
	client->start_time = cur_time;
	client->txcount = 0;
	client->RT = client->IRT + dhc6_rand(client->IRT);
}

/* Advance the DHCPv6 retransmission state once. */
static void
dhc6_retrans_advance(struct client_state *client)
{
	TIME elapsed;

	elapsed = cur_time - client->start_time;
	/* retrans_advance is called after consuming client->RT. */
	elapsed += client->RT;

        /* RT for each subsequent message transmission is based on the previous
         * value of RT:
         *
         *    RT = 2*RTprev + RAND*RTprev
         */
        client->RT += client->RT + dhc6_rand(client->RT);

        /* MRT specifies an upper bound on the value of RT (disregarding the
         * randomization added by the use of RAND).  If MRT has a value of 0,
         * there is no upper limit on the value of RT.  Otherwise:
         *
         *    if (RT > MRT)
         *       RT = MRT + RAND*MRT
         */
        if ((client->MRT != 0) && (client->RT > client->MRT))
                client->RT = client->MRT + dhc6_rand(client->MRT);

	/* Further, if there's an MRD, we should wake up upon reaching
	 * the MRD rather than at some point after it.
	 */
	if ((client->MRD != 0) && ((elapsed + client->RT) > client->MRD)) {
		client->RT = (client->start_time + client->MRD) - cur_time;
	}

	client->txcount++;
}

/* Quick validation of DHCPv6 ADVERTISE packet contents. */
static int
valid_reply(struct packet *packet, struct client_state *client)
{
	struct data_string sid, cid;
	struct option_cache *oc;
	int rval = ISC_TRUE;

	memset(&sid, 0, sizeof(sid));
	memset(&cid, 0, sizeof(cid));

	if (!lookup_option(&dhcpv6_universe, packet->options, D6O_SERVERID)) {
		log_error("Advertise without a server identifier received.");
		rval = ISC_FALSE;
	}

	oc = lookup_option(&dhcpv6_universe, packet->options, D6O_CLIENTID);
	if (!oc ||
	    !evaluate_option_cache(&sid, packet, NULL, client, packet->options,
				   client->sent_options, &global_scope, oc,
				   MDL)) {
		log_error("Advertise without a client identifier.");
		rval = ISC_FALSE;
	}

	oc = lookup_option(&dhcpv6_universe, client->sent_options,
			   D6O_CLIENTID);
	if (!oc ||
	    !evaluate_option_cache(&cid, packet, NULL, client,
				   client->sent_options, NULL, &global_scope,
				   oc, MDL)) {
		log_error("Local client identifier is missing!");
		rval = ISC_FALSE;
	}

	if (sid.len == 0 ||
	    sid.len != cid.len ||
	    memcmp(sid.data, cid.data, sid.len)) {
		log_error("Advertise with matching transaction ID, but "
			  "mismatching client id.");
		rval = ISC_FALSE;
	}

	return rval;
}

/* Create a complete copy of a DHCPv6 lease structure.
 */
static struct dhc6_lease *
dhc6_dup_lease(struct dhc6_lease *lease, const char *file, int line)
{
	struct dhc6_lease *copy;
	struct dhc6_ia **insert_ia, *ia;

	copy = dmalloc(sizeof(*copy), file, line);
	if (copy == NULL) {
		log_error("Out of memory for v6 lease structure.");
		return NULL;
	}

	data_string_copy(&copy->server_id, &lease->server_id, file, line);
	copy->pref = lease->pref;

	memcpy(copy->dhcpv6_transaction_id, lease->dhcpv6_transaction_id,
	       sizeof(copy->dhcpv6_transaction_id));

	option_state_reference(&copy->options, lease->options, file, line);

	insert_ia = &copy->bindings;
	for (ia = lease->bindings ; ia != NULL ; ia = ia->next) {
		*insert_ia = dhc6_dup_ia(ia, file, line);

		if (*insert_ia == NULL) {
			dhc6_lease_destroy(copy, file, line);
			return NULL;
		}

		insert_ia = &(*insert_ia)->next;
	}

	return copy;
}

/* Duplicate an IA structure.
 */
static struct dhc6_ia *
dhc6_dup_ia(struct dhc6_ia *ia, const char *file, int line)
{
	struct dhc6_ia *copy;
	struct dhc6_addr **insert_addr, *addr;

	copy = dmalloc(sizeof(*ia), file, line);

	memcpy(copy->iaid, ia->iaid, sizeof(copy->iaid));

	copy->starts = ia->starts;
	copy->renew = ia->renew;
	copy->rebind = ia->rebind;

	insert_addr = &copy->addrs;
	for (addr = ia->addrs ; addr != NULL ; addr = addr->next) {
		*insert_addr = dhc6_dup_addr(addr, file, line);

		if (*insert_addr == NULL) {
			dhc6_ia_destroy(copy, file, line);
			return NULL;
		}

		insert_addr = &(*insert_addr)->next;
	}

	if (ia->options != NULL)
		option_state_reference(&copy->options, ia->options,
				       file, line);

	return copy;
}

/* Duplicate an IAADDR structure.
 */
static struct dhc6_addr *
dhc6_dup_addr(struct dhc6_addr *addr, const char *file, int line)
{
	struct dhc6_addr *copy;

	copy = dmalloc(sizeof(*addr), file, line);

	if (copy == NULL)
		return NULL;

	memcpy(&copy->address, &addr->address, sizeof(copy->address));

	copy->flags = addr->flags;
	copy->starts = addr->starts;
	copy->preferred_life = addr->preferred_life;
	copy->max_life = addr->max_life;

	if (addr->options != NULL)
		option_state_reference(&copy->options, addr->options,
				       file, line);

	return copy;
}

/* Form a DHCPv6 lease structure based upon packet contents.  Creates and
 * populates IA's and any IAADDR's they contain.
 */
static struct dhc6_lease *
dhc6_leaseify(struct packet *packet)
{
	struct data_string ds;
	struct dhc6_lease *lease;
	struct option_cache *oc;

	lease = dmalloc(sizeof(*lease), MDL);
	if (lease == NULL) {
		log_error("Out of memory for v6 lease structure.");
		return NULL;
	}

	memcpy(lease->dhcpv6_transaction_id, packet->dhcpv6_transaction_id, 3);
	option_state_reference(&lease->options, packet->options, MDL);

	memset(&ds, 0, sizeof(ds));

	/* Determine preference (default zero). */
	oc = lookup_option(&dhcpv6_universe, lease->options, D6O_PREFERENCE);
	if (oc &&
	    evaluate_option_cache(&ds, packet, NULL, NULL, lease->options,
				  NULL, &global_scope, oc, MDL)) {
		if (ds.len != 1) {
			log_error("Invalid length of DHCPv6 Preference option "
				  "(%d != 1)", ds.len);
			data_string_forget(&ds, MDL);
			dhc6_lease_destroy(lease, MDL);
			return NULL;
		} else {
			lease->pref = ds.data[0];
			log_debug("RCV:  X-- Preference %u.",
				  (unsigned)lease->pref);
		}

		data_string_forget(&ds, MDL);
	}

	/* Dig into recursive DHCPv6 pockets for IA_NA and contained IAADDR
	 * options.
	 */
	if (dhc6_parse_ia_na(&lease->bindings, packet,
			     lease->options) != ISC_R_SUCCESS) {
		/* Error conditions are logged by the caller. */
		dhc6_lease_destroy(lease, MDL);
		return NULL;
	}

	/* This is last because in the future we may want to make a different
	 * key based upon additional information from the packet (we may need
	 * to allow multiple leases in one client state per server, but we're
	 * not sure based on what additional keys now).
	 */
	oc = lookup_option(&dhcpv6_universe, packet->options, D6O_SERVERID);
	if (!evaluate_option_cache(&lease->server_id, packet, NULL, NULL,
				   lease->options, NULL, &global_scope,
				   oc, MDL) ||
	    lease->server_id.len == 0) {
		/* This should be impossible due to validation checks earlier.
		 */
		log_error("Invalid SERVERID option cache.");
		dhc6_lease_destroy(lease, MDL);
		return NULL;
	} else {
		log_debug("RCV:  X-- Server ID: %s",
			  print_hex_1(lease->server_id.len,
				      lease->server_id.data, 52));
	}

	return lease;
}

static isc_result_t
dhc6_parse_ia_na(struct dhc6_ia **pia, struct packet *packet,
		 struct option_state *options)
{
	struct data_string ds;
	struct dhc6_ia *ia;
	struct option_cache *oc;
	isc_result_t result;

	memset(&ds, 0, sizeof(ds));

	oc = lookup_option(&dhcpv6_universe, options, D6O_IA_NA);
	for ( ; oc != NULL ; oc = oc->next) {
		ia = dmalloc(sizeof(*ia), MDL);
		if (ia == NULL) {
			log_error("Out of memory allocating IA_NA structure.");
			return ISC_R_NOMEMORY;
		} else if (evaluate_option_cache(&ds, packet, NULL, NULL,
						 options, NULL,
						 &global_scope, oc, MDL) &&
			   ds.len >= 12) {
			memcpy(ia->iaid, ds.data, 4);
			ia->starts = cur_time;
			ia->renew = getULong(ds.data + 4);
			ia->rebind = getULong(ds.data + 8);

			log_debug("RCV:  X-- IA_NA %s",
				  print_hex_1(4, ia->iaid, 59));
			/* XXX: This should be the printed time I think. */
			log_debug("RCV:  | X-- starts %u",
				  (unsigned)ia->starts);
			log_debug("RCV:  | X-- t1 - renew  +%u", ia->renew);
			log_debug("RCV:  | X-- t2 - rebind +%u", ia->rebind);

			/* RFC3315 section 22.4, discard IA_NA's that
			 * have t1 greater than t2, and both not zero.
			 * Since RFC3315 defines this behaviour, it is not
			 * an error - just normal operation.
			 *
			 * Note that RFC3315 says we MUST honor these values
			 * if they are not zero.  So insane values are
			 * totally OK.
			 */
			if ((ia->renew > 0) && (ia->rebind > 0) &&
			    (ia->renew > ia->rebind)) {
				log_debug("RCV:  | !-- INVALID renew/rebind "
					  "times, IA_NA discarded.");
				dfree(ia, MDL);
				data_string_forget(&ds, MDL);
				continue;
			}

			if (ds.len > 12) {
				log_debug("RCV:  | X-- [Options]");

				if (!option_state_allocate(&ia->options,
							   MDL)) {
					log_error("Out of memory allocating "
						  "IA option state.");
					dfree(ia, MDL);
					data_string_forget(&ds, MDL);
					return ISC_R_NOMEMORY;
				}

				if (!parse_option_buffer(ia->options,
							 ds.data + 12,
							 ds.len - 12,
							 &dhcpv6_universe)) {
					log_error("Corrupt IA_NA options.");
					option_state_dereference(&ia->options,
								 MDL);
					dfree(ia, MDL);
					data_string_forget(&ds, MDL);
					return ISC_R_BADPARSE;
				}
			}
			data_string_forget(&ds, MDL);

			if (ia->options != NULL) {
				result = dhc6_parse_addrs(&ia->addrs, packet,
							  ia->options);
				if (result != ISC_R_SUCCESS) {
					option_state_dereference(&ia->options,
								 MDL);
					dfree(ia, MDL);
					return result;
				}
			}

			*pia = ia;
			pia = &ia->next;
		} else {
			log_error("Invalid IA_NA option cache.");
			dfree(ia, MDL);
			if (ds.len != 0)
				data_string_forget(&ds, MDL);
			return ISC_R_UNEXPECTED;
		}
	}

	return ISC_R_SUCCESS;
}


static isc_result_t
dhc6_parse_addrs(struct dhc6_addr **paddr, struct packet *packet,
		 struct option_state *options)
{
	struct data_string ds;
	struct option_cache *oc;
	struct dhc6_addr *addr;

	memset(&ds, 0, sizeof(ds));

	oc = lookup_option(&dhcpv6_universe, options, D6O_IAADDR);
	for ( ; oc != NULL ; oc = oc->next) {
		addr = dmalloc(sizeof(*addr), MDL);
		if (addr == NULL) {
			log_error("Out of memory allocating "
				  "address structure.");
			return ISC_R_NOMEMORY;
		} else if (evaluate_option_cache(&ds, packet, NULL, NULL,
						 options, NULL, &global_scope,
						 oc, MDL) &&
			   (ds.len >= 24)) {

			addr->address.len = 16;
			memcpy(addr->address.iabuf, ds.data, 16);
			addr->starts = cur_time;
			addr->preferred_life = getULong(ds.data + 16);
			addr->max_life = getULong(ds.data + 20);

			log_debug("RCV:  | | X-- IAADDR %s",
				  piaddr(addr->address));
			log_debug("RCV:  | | | X-- Preferred lifetime %u.",
				  addr->preferred_life);
			log_debug("RCV:  | | | X-- Max lifetime %u.",
				  addr->max_life);

			/* RFC 3315 section 22.6 says we must discard
			 * addresses whose pref is later than valid.
			 */
			if ((addr->preferred_life > addr->max_life)) {
				log_debug("RCV:  | | | !-- INVALID lifetimes, "
					  "IAADDR discarded.  Check your "
					  "server configuration.");
				dfree(addr, MDL);
				data_string_forget(&ds, MDL);
				continue;
			}

			/* Fortunately this is the last recursion in the
			 * protocol.
			 */
			if (ds.len > 24) {
				if (!option_state_allocate(&addr->options,
							   MDL)) {
					log_error("Out of memory allocating "
						  "IAADDR option state.");
					dfree(addr, MDL);
					data_string_forget(&ds, MDL);
					return ISC_R_NOMEMORY;
				}

				if (!parse_option_buffer(addr->options,
							 ds.data + 24,
							 ds.len - 24,
							 &dhcpv6_universe)) {
					log_error("Corrupt IAADDR options.");
					option_state_dereference(&addr->options,
								 MDL);
					dfree(addr, MDL);
					data_string_forget(&ds, MDL);
					return ISC_R_BADPARSE;
				}
			}

			if (addr->options != NULL)
				log_debug("RCV:  | | | X-- "
					  "[Options]");

			data_string_forget(&ds, MDL);

			*paddr = addr;
			paddr = &addr->next;
		} else {
			log_error("Invalid IAADDR option cache.");
			dfree(addr, MDL);
			if (ds.len != 0)
				data_string_forget(&ds, MDL);
			return ISC_R_UNEXPECTED;
		}
	}

	return ISC_R_SUCCESS;
}

/* Clean up a lease object and deallocate all its parts. */
void
dhc6_lease_destroy(struct dhc6_lease *lease, const char *file, int line)
{
	struct dhc6_ia *ia, *nia;

	/* no-op */
	if (lease == NULL)
		return;

	if (lease->server_id.len != 0)
		data_string_forget(&lease->server_id, file, line);

	for (ia = lease->bindings ; ia != NULL ; ia = nia) {
		nia = ia->next;

		dhc6_ia_destroy(ia, file, line);
	}

	if (lease->options != NULL)
		option_state_dereference(&lease->options, file, line);

	dfree(lease, file, line);
}

/* Traverse the addresses list, and destroy their contents. */
static void
dhc6_ia_destroy(struct dhc6_ia *ia, const char *file, int line)
{
	struct dhc6_addr *addr, *naddr;

	for (addr = ia->addrs ; addr != NULL ; addr = naddr) {
		naddr = addr->next;

		if (addr->options != NULL)
			option_state_dereference(&addr->options, file, line);

		dfree(addr, file, line);
	}

	if (ia->options != NULL)
		option_state_dereference(&ia->options, file, line);

	dfree(ia, file, line);
}

/* For a given lease, insert it into the tail of the lease list.  Upon
 * finding a duplicate by server id, remove it and take over its position.
 */
static void
insert_lease(struct dhc6_lease **head, struct dhc6_lease *new)
{
	while (*head != NULL) {
		if ((*head)->server_id.len == new->server_id.len &&
		    memcmp((*head)->server_id.data, new->server_id.data,
			   new->server_id.len) == 0) {
			new->next = (*head)->next;
			dhc6_lease_destroy(*head, MDL);
			break;
		}

		head= &(*head)->next;
	}

	*head = new;
	return;
}

/* Not really clear what to do here yet.
 */
static int
dhc6_score_lease(struct client_state *client, struct dhc6_lease *lease)
{
	struct dhc6_ia *ia;
	struct dhc6_addr *addr;
	struct option **req;
	int i;

	if (lease->score)
		return lease->score;

	lease->score = 1;

	/* If this lease lacks a required option, dump it. */
	/* XXX: we should be able to cache the failure... */
	req = client->config->required_options;
	if (req != NULL) {
		for (i = 0 ; req[i] != NULL ; i++) {
			if (lookup_option(&dhcpv6_universe, lease->options,
					  req[i]->code) == NULL) {
				lease->score = 0;
				return lease->score;
			}
		}
	}

	/* If this lease contains a requested option, improve its
	 * score.
	 */
	req = client->config->requested_options;
	if (req != NULL) {
		for (i = 0 ; req[i] != NULL ; i++) {
			if (lookup_option(&dhcpv6_universe, lease->options,
					  req[i]->code) != NULL)
				lease->score++;
		}
	}

	for (ia = lease->bindings ; ia != NULL ; ia = ia->next) {
		lease->score += 50;

		for (addr = ia->addrs ; addr != NULL ; addr = addr->next) {
			lease->score += 100;
		}
	}

	return lease->score;
}

/* start_init6() kicks off the process, transmitting a packet and
 * scheduling a retransmission event.
 */
void
start_init6(struct client_state *client)
{
	log_debug("PRC: Soliciting for leases (INIT).");
	client->state = S_INIT;

	/* Fetch a 24-bit transaction ID. */
	dhc6_new_xid(client);

	/* Initialize timers, RFC3315 section 17.1.2. */
	client->IRT = SOL_TIMEOUT;
	client->MRT = SOL_MAX_RT;
	client->MRC = 0;
	client->MRD = 0;

	dhc6_retrans_init(client);
	/* RFC3315 section 17.1.2 goes out of its way:
	 *
	 * Also, the first RT MUST be selected to be strictly greater than IRT
	 * by choosing RAND to be strictly greater than 0.
	 */
	if (client->RT <= client->IRT)
		client->RT = client->IRT + 1;

	client->v6_handler = init_handler;

	/* RFC3315 section 17.1.2 says we MUST start the first packet
	 * between 0 and SOL_MAX_DELAY seconds.  The good news is
	 * SOL_MAX_DELAY is 1.
	 */
	add_timeout(cur_time + (random() % SOL_MAX_DELAY), do_init6, client,
		    NULL, NULL);

	if (nowait)
		go_daemon();
}

/* start_init6() kicks off an "init-reboot" version of the process, at
 * startup to find out if old bindings are 'fair' and at runtime whenever
 * a link cycles state we'll eventually want to do this.
 */
void
start_confirm6(struct client_state *client)
{
	/* If there is no active lease, there is nothing to check. */
	if (client->active_lease == NULL) {
		start_init6(client);
		return;
	}

	log_debug("PRC: Confirming active lease (INIT-REBOOT).");
	client->state = S_REBOOTING;

	/* Fetch a 24-bit transaction ID. */
	dhc6_new_xid(client);

	/* Initialize timers, RFC3315 section 17.1.3. */
	client->IRT = CNF_TIMEOUT;
	client->MRT = CNF_MAX_RT;
	client->MRC = 0;
	client->MRD = CNF_MAX_RD;

	dhc6_retrans_init(client);

	client->v6_handler = reply_handler;

	add_timeout(cur_time + (random() % CNF_MAX_DELAY), do_confirm6, client,
		    NULL, NULL);
}

/* do_init6() marshals and transmits a solicit.
 */
void
do_init6(void *input)
{
	struct client_state *client;
	struct dhc6_ia *old_ia;
	struct dhc6_addr *old_addr;
	struct data_string ds;
	struct data_string ia;
	struct data_string addr;
	TIME elapsed;
	u_int32_t t1, t2;
	int idx, len, send_ret;

	client = input;

	/* In RFC3315 section 17.1.2, the retransmission timer is
	 * used as the selecting timer.
	 */
	if (client->advertised_leases != NULL) {
		start_selecting6(client);
		return;
	}

	if ((client->MRC != 0) && (client->txcount > client->MRC)) {
		log_info("Max retransmission count exceeded.");
		return;
	}

	elapsed = cur_time - client->start_time;
	if ((client->MRD != 0) && (elapsed > client->MRD)) {
		log_info("Max retransmission duration exceeded.");
		return;
	}

	memset(&ds, 0, sizeof(ds));
	if (!buffer_allocate(&ds.buffer, 4, MDL)) {
		log_error("Unable to allocate memory for SOLICIT.");
		return;
	}
	ds.data = ds.buffer->data;
	ds.len = 4;

	ds.buffer->data[0] = DHCPV6_SOLICIT;
	memcpy(ds.buffer->data + 1, client->dhcpv6_transaction_id, 3);

	/* Form an elapsed option. */
	if ((elapsed < 0) || (elapsed > 655))
		client->elapsed = 0xffff;
	else
		client->elapsed = elapsed * 100;

	log_debug("XMT: Forming Solicit, %u ms elapsed.",
		  (unsigned)client->elapsed);

	client->elapsed = htons(client->elapsed);

	make_client6_options(client, &client->sent_options, NULL,
			     DHCPV6_SOLICIT);

	/* Fetch any configured 'sent' options (includes DUID) in wire format.
	 */
	dhcpv6_universe.encapsulate(&ds, NULL, NULL, client,
				    NULL, client->sent_options, &global_scope,
				    &dhcpv6_universe);

	/* Append an IA_NA. */
	/* XXX: maybe the IA_NA('s) should be put into the sent_options
	 * cache.  They'd have to be pulled down as they also contain
	 * different option caches in the same universe...
	 */
	memset(&ia, 0, sizeof(ia));
	if (!buffer_allocate(&ia.buffer, 12, MDL)) {
		log_error("Unable to allocate memory for IA_NA.");
		data_string_forget(&ds, MDL);
		return;
	}
	ia.data = ia.buffer->data;
	ia.len = 12;

	/* A simple IAID is the last 4 bytes of the hardware address. */
	if (client->interface->hw_address.hlen > 4) {
		idx = client->interface->hw_address.hlen - 4;
		len = 4;
	} else {
		idx = 0;
		len = client->interface->hw_address.hlen;
	}
	memcpy(ia.buffer->data, client->interface->hw_address.hbuf + idx, len);

	t1 = client->config->requested_lease / 2;
	t2 = t1 + (t1 / 2);
	putULong(ia.buffer->data + 4, t1);
	putULong(ia.buffer->data + 8, t2);

	log_debug("XMT:  X-- IA_NA %s", print_hex_1(4, ia.buffer->data, 55));
	log_debug("XMT:  | X-- Request renew in  +%u", (unsigned)t1);
	log_debug("XMT:  | X-- Request rebind in +%u", (unsigned)t2);

	if ((client->active_lease != NULL) &&
	    ((old_ia = find_ia(client->active_lease->bindings,
			       (char *)ia.buffer->data)) != NULL)) {
		/* For each address in the old IA, request a binding. */
		memset(&addr, 0, sizeof(addr));
		for (old_addr = old_ia->addrs ; old_addr != NULL ;
		     old_addr = old_addr->next) {
			if (old_addr->address.len != 16) {
				log_error("Invalid IPv6 address length %d.  "
				          "Ignoring.  (%s:%d)",
					  old_addr->address.len, MDL);
				continue;
			}

			if (!buffer_allocate(&addr.buffer, 24, MDL)) {
				log_error("Unable to allocate memory for "
					  "IAADDR.");
				data_string_forget(&ia, MDL);
				data_string_forget(&ds, MDL);
				return;
			}
			addr.data = addr.buffer->data;
			addr.len = 24;

			memcpy(addr.buffer->data, old_addr->address.iabuf, 16);

			t1 = client->config->requested_lease;
			t2 = t1 + (t1 / 2);
			putULong(addr.buffer->data + 16, t1);
			putULong(addr.buffer->data + 20, t2);

			log_debug("XMT:  | X-- Request address %s.",
				  piaddr(old_addr->address));
			log_debug("XMT:  | | X-- Request preferred in +%u",
				  (unsigned)t1);
			log_debug("XMT:  | | X-- Request valid in     +%u",
				  (unsigned)t2);

			append_option(&ia, &dhcpv6_universe, iaaddr_option,
				      &addr);

			data_string_forget(&addr, MDL);
		}
	}

	append_option(&ds, &dhcpv6_universe, ia_na_option, &ia);
	data_string_forget(&ia, MDL);

	/* Transmit and wait. */

	log_info("XMT: Solicit on %s, interval %ld",
		 client->name ? client->name : client->interface->name,
		 (long int)client->RT);

	send_ret = send_packet6(client->interface,
				ds.data, ds.len, &DHCPv6DestAddr);
	if (send_ret != ds.len) {
		log_error("dhc6: send_packet6() sent %d of %d bytes",
			  send_ret, ds.len);
	}

	data_string_forget(&ds, MDL);

	add_timeout(cur_time + client->RT, do_init6, client, NULL, NULL);

	dhc6_retrans_advance(client);
}

/* do_confirm6() creates a Confirm packet and transmits it.  This function
 * is called on every timeout to (re)transmit.
 */
void
do_confirm6(void *input)
{
	struct client_state *client;
	struct data_string ds;
	int send_ret;
	TIME elapsed;

	client = input;

	if (client->active_lease == NULL)
		log_fatal("Impossible condition at %s:%d.", MDL);

	/* In section 17.1.3, it is said:
	 *
	 *   If the client receives no responses before the message
	 *   transmission process terminates, as described in section 14,
	 *   the client SHOULD continue to use any IP addresses, using the
	 *   last known lifetimes for those addresses, and SHOULD continue
	 *   to use any other previously obtained configuration parameters.
	 *
	 * So if confirm times out, we go active.
	 *
	 * XXX: Should we reduce all IA's t1 to 0, so that we renew and
	 * stick there until we get a reply?
	 */

	if ((client->MRC != 0) && (client->txcount > client->MRC))  {
		log_info("Max retransmission count exceeded.");
		start_bound(client);
		return;
	}

	elapsed = cur_time - client->start_time;
	if ((client->MRD != 0) && (elapsed > client->MRD)) {
		log_info("Max retransmission duration exceeded.");
		start_bound(client);
		return;
	}

	memset(&ds, 0, sizeof(ds));
	if (!buffer_allocate(&ds.buffer, 4, MDL)) {
		log_error("Unable to allocate memory for Confirm.");
		return;
	}
	ds.data = ds.buffer->data;
	ds.len = 4;

	ds.buffer->data[0] = DHCPV6_CONFIRM;
	memcpy(ds.buffer->data + 1, client->dhcpv6_transaction_id, 3);

	/* Form an elapsed option. */
	if ((elapsed < 0) || (elapsed > 655))
		client->elapsed = 0xffff;
	else
		client->elapsed = elapsed * 100;

	log_debug("XMT: Forming Confirm, %u ms elapsed.",
		  (unsigned)client->elapsed);

	client->elapsed = htons(client->elapsed);

	make_client6_options(client, &client->sent_options,
			     client->active_lease, DHCPV6_CONFIRM);

	/* Fetch any configured 'sent' options (includes DUID') in wire format.
	 */
	dhcpv6_universe.encapsulate(&ds, NULL, NULL, client, NULL,
				    client->sent_options, &global_scope,
				    &dhcpv6_universe);

	/* Append IA's. */
	if (dhc6_add_ia(client, &ds, client->active_lease,
                        DHCPV6_CONFIRM) != ISC_R_SUCCESS) {
		data_string_forget(&ds, MDL);
		return;
	}

	/* Transmit and wait. */

	log_info("XMT: Confirm on %s, interval %ld.",
		 client->name ? client->name : client->interface->name,
		 (long int)client->RT);

	send_ret = send_packet6(client->interface, ds.data, ds.len,
				&DHCPv6DestAddr);
	if (send_ret != ds.len) {
		log_error("dhc6: sendpacket6() sent %d of %d bytes",
			  send_ret, ds.len);
	}

	data_string_forget(&ds, MDL);

	add_timeout(cur_time + client->RT, do_confirm6, client, NULL, NULL);

	dhc6_retrans_advance(client);
}

/*
 * Release addresses.
 */
void
start_release6(struct client_state *client)
{
        /* Cancel any pending transmissions */
	cancel_timeout(do_confirm6, client);
	cancel_timeout(do_select6, client);
	cancel_timeout(do_refresh6, client);
	cancel_timeout(do_release6, client);
        client->state = S_STOPPED;

        /*
         * It is written:  "The client MUST NOT use any of the addresses it
         * is releasing as the source address in the Release message or in
         * any subsequently transmitted message."  So unconfigure now.
         */
        unconfigure6(client, "RELEASE6");

	/* Fetch a 24-bit transaction ID. */
	dhc6_new_xid(client);

	/* Set timers per RFC3315 section 18.1.1. */
	client->IRT = REL_TIMEOUT;
	client->MRT = 0;
	client->MRC = REL_MAX_RC;
	client->MRD = 0;

	dhc6_retrans_init(client);
	client->v6_handler = reply_handler;

	/* ("re")transmit the first packet. */
	do_release6(client);
}
/*
 * do_release6() creates a Release packet and transmits it.
 */
static void
do_release6(void *input)
{
	struct sockaddr_in6 unicast, *dest_addr = &DHCPv6DestAddr;
	struct client_state *client;
	struct data_string ds;
	struct option_cache *oc;
	int send_ret;

	client = input;

	if (client->active_lease == NULL)
		log_fatal("Impossible condition at %s:%d.", MDL);

	if ((client->MRC != 0) && (client->txcount > client->MRC))  {
		log_info("Max retransmission count exceeded.");
		return;
	}

	/*
	 * Check whether the server has sent a unicast option; if so, we can
	 * use the address it specified.
	 */
	oc = lookup_option(&dhcpv6_universe, 
			   client->active_lease->options, D6O_UNICAST);
	if (oc && evaluate_option_cache(&ds, NULL, NULL, NULL,
                                        client->active_lease->options, 
					NULL, &global_scope, oc, MDL)) {
		if (ds.len < 16) {
			log_error("Invalid unicast option length %d.", ds.len);
		} else {
			memset(&unicast, 0, sizeof(DHCPv6DestAddr));
			unicast.sin6_family = AF_INET6;
			unicast.sin6_port = remote_port;
			memcpy(&unicast.sin6_addr, ds.data, 16);
			dest_addr = &unicast;
		}

		data_string_forget(&ds, MDL);
	}

	memset(&ds, 0, sizeof(ds));
	if (!buffer_allocate(&ds.buffer, 4, MDL)) {
		log_error("Unable to allocate memory for Release.");
		return;
	}

	ds.data = ds.buffer->data;
	ds.len = 4;
	ds.buffer->data[0] = DHCPV6_RELEASE;
	memcpy(ds.buffer->data + 1, client->dhcpv6_transaction_id, 3);

	log_debug("XMT: Forming Release.");
	make_client6_options(client, &client->sent_options,
			     client->active_lease, DHCPV6_RELEASE);
	dhcpv6_universe.encapsulate(&ds, NULL, NULL, client, NULL,
				    client->sent_options, &global_scope,
				    &dhcpv6_universe);

	/* Append IA's. */
	if (dhc6_add_ia(client, &ds, client->active_lease,
                        DHCPV6_RELEASE) != ISC_R_SUCCESS) {
		data_string_forget(&ds, MDL);
		return;
	}

	/* Transmit and wait. */
	log_info("XMT: Release on %s, interval %ld.",
		 client->name ? client->name : client->interface->name,
		 (long int)client->RT);

	send_ret = send_packet6(client->interface, ds.data, ds.len,
				&DHCPv6DestAddr);
	if (send_ret != ds.len) {
		log_error("dhc6: sendpacket6() sent %d of %d bytes",
			  send_ret, ds.len);
	}

	data_string_forget(&ds, MDL);

	add_timeout(cur_time + client->RT, do_release6, client, NULL, NULL);
	dhc6_retrans_advance(client);
}

/* status_log() just puts a status code into displayable form and logs it
 * to info level.
 */
static void
status_log(int code, const char *scope, const char *additional, int len)
{
	const char *msg = NULL;

	switch(code) {
	      case STATUS_Success:
		msg = "Succes";
		break;

	      case STATUS_UnspecFail:
		msg = "UnspecFail";
		break;
	      case STATUS_NoAddrsAvail:
		msg = "NoAddrsAvail";
		break;

	      case STATUS_NoBinding:
		msg = "NoBinding";
		break;

	      case STATUS_NotOnLink:
		msg = "NotOnLink";
		break;

	      case STATUS_UseMulticast:
		msg = "UseMulticast";
		break;

	      default:
		msg = "UNKNOWN";
		break;
	}

	if (len > 0)
		log_info("%s status code %s: %s", scope, msg,
			 print_hex_1(len, 
			 	     (const unsigned char *)additional, 50));
	else
		log_info("%s status code %s.", scope, msg);
}

/* Acquire a status code.
 */
static isc_result_t
dhc6_get_status_code(struct option_state *options, unsigned *code,
		     struct data_string *msg)
{
	struct option_cache *oc;
	struct data_string ds;
	isc_result_t rval = ISC_R_SUCCESS;

	if ((options == NULL) || (code == NULL))
		return ISC_R_INVALIDARG;

	if ((msg != NULL) && (msg->len != 0))
		return ISC_R_INVALIDARG;

	memset(&ds, 0, sizeof(ds));

	/* Assume success if there is no option. */
	*code = STATUS_Success;

	oc = lookup_option(&dhcpv6_universe, options, D6O_STATUS_CODE);
	if ((oc != NULL) &&
	    evaluate_option_cache(&ds, NULL, NULL, NULL, options,
				  NULL, &global_scope, oc, MDL)) {
		if (ds.len < 2) {
			log_error("Invalid status code length %d.", ds.len);
			rval = ISC_R_FORMERR;
		} else
			*code = getUShort(ds.data);

		if ((msg != NULL) && (ds.len > 2)) {
			data_string_copy(msg, &ds, MDL);
			msg->data += 2;
			msg->len -= 2;
		}

		data_string_forget(&ds, MDL);
		return rval;
	}

	return ISC_R_NOTFOUND;
}

/* Look at status codes in an advertise, and reform the return value.
 */
static isc_result_t
dhc6_check_status(isc_result_t rval, struct option_state *options,
		  const char *scope, unsigned *code)
{
	struct data_string msg;
	isc_result_t status;

	if ((scope == NULL) || (code == NULL))
		return ISC_R_INVALIDARG;

	/* If we don't find a code, we assume success. */
	*code = STATUS_Success;

	/* If there is no options cache, then there is no code. */
	if (options != NULL) {
		memset(&msg, 0, sizeof(msg));
		status = dhc6_get_status_code(options, code, &msg);

		if (status == ISC_R_SUCCESS) {
			status_log(*code, scope, (char *)msg.data, msg.len);
			data_string_forget(&msg, MDL);

			if (*code != STATUS_Success)
				rval = ISC_R_FAILURE;

		} else if (status != ISC_R_NOTFOUND)
			rval = status;
	}

	return rval;
}

/* Look in the packet, any IA's, and any IAADDR's within those IA's to find
 * status code options that are not SUCCESS.
 */
static isc_result_t
dhc6_check_advertise(struct dhc6_lease *lease)
{
	struct dhc6_ia *ia;
	struct dhc6_addr *addr;
	isc_result_t rval = ISC_R_SUCCESS;
	int have_addrs = ISC_FALSE;
	unsigned code;

	rval = dhc6_check_status(rval, lease->options, "message", &code);

	for (ia = lease->bindings ; ia != NULL ; ia = ia->next) {
		rval = dhc6_check_status(rval, ia->options, "IA_NA", &code);

		for (addr = ia->addrs ; addr != NULL ; addr = addr->next) {
			rval = dhc6_check_status(rval, addr->options,
						 "IAADDR", &code);
			have_addrs = ISC_TRUE;
		}
	}

	if (have_addrs != ISC_TRUE)
		rval = ISC_R_ADDRNOTAVAIL;

	return rval;
}

/* status code <-> action matrix for the client in SELECT state
 * (request/reply).  Returns true if action was taken (and the
 * packet should be ignored), or false if no action was taken.
 */
static isc_boolean_t
dhc6_select_action(struct client_state *client, isc_result_t rval,
		   unsigned code)
{
	struct dhc6_lease *lease;

	if (client == NULL)
		return ISC_R_INVALIDARG;

	if (rval == ISC_R_SUCCESS)
		return ISC_FALSE;

	switch (code) {
		/* We may have an earlier failure status code (so no
		 * success rval), and a success code now.  This
		 * doesn't upgrade the rval to success, but it does
		 * mean we take no action here.
		 */
	      case STATUS_Success:
		/* Gimpy server, or possibly an attacker. */
	      case STATUS_NoBinding:
	      case STATUS_UseMulticast:
		/* Take no action. */
		return ISC_FALSE;

		/* If the server can't deal with us, either try the
		 * next advertised server, or continue retrying if there
		 * weren't any.
		 */
	      default:
	      case STATUS_UnspecFail:
		if (client->advertised_leases != NULL) {
			dhc6_lease_destroy(client->selected_lease, MDL);
			client->selected_lease = NULL;

			start_selecting6(client);

			break;
		} else /* Take no action - continue to retry. */
			return ISC_FALSE;

		/* If the server has no addresses, try other servers if
		 * we got some, otherwise go to INIT to hope for more
		 * servers.
		 */
	      case STATUS_NoAddrsAvail:
		if (client->state == S_REBOOTING)
			return ISC_FALSE;

		if (client->selected_lease == NULL)
			log_fatal("Impossible case at %s:%d.", MDL);

		dhc6_lease_destroy(client->selected_lease, MDL);
		client->selected_lease = NULL;

		if (client->advertised_leases != NULL)
			start_selecting6(client);
		else
			start_init6(client);

		break;

		/* If we got a NotOnLink from a Confirm, then we're not
		 * on link.  Kill the old-active binding and start over.
		 *
		 * If we got a NotOnLink from our Request, something weird
		 * happened.  Start over from scratch anyway.
		 */
	      case STATUS_NotOnLink:
		if (client->state == S_REBOOTING) {
			if (client->active_lease == NULL)
				log_fatal("Impossible case at %s:%d.", MDL);

			dhc6_lease_destroy(client->active_lease, MDL);
		} else {
			if (client->selected_lease == NULL)
				log_fatal("Impossible case at %s:%d.", MDL);

			dhc6_lease_destroy(client->selected_lease, MDL);
			client->selected_lease = NULL;

			while (client->advertised_leases != NULL) {
				lease = client->advertised_leases;
				client->advertised_leases = lease->next;

				dhc6_lease_destroy(lease, MDL);
			}
		}

		start_init6(client);
		break;
	}

	return ISC_TRUE;
}

static void
dhc6_withdraw_lease(struct client_state *client)
{
	struct dhc6_ia *ia;
	struct dhc6_addr *addr;

	if ((client == NULL) || (client->active_lease == NULL))
		return;

	for (ia = client->active_lease->bindings ; ia != NULL ;
	     ia = ia->next) {
		for (addr = ia->addrs ; addr != NULL ; addr = addr->next) {
			addr->max_life = addr->preferred_life = 0;
		}
	}

	/* Perform expiry. */
	do_expire(client);
}

/* status code <-> action matrix for the client in BOUND state
 * (request/reply).  Returns true if action was taken (and the
 * packet should be ignored), or false if no action was taken.
 */
static isc_boolean_t
dhc6_reply_action(struct client_state *client, isc_result_t rval,
		  unsigned code)
{

	if (client == NULL)
		return ISC_R_INVALIDARG;

	if (rval == ISC_R_SUCCESS)
		return ISC_FALSE;

	switch (code) {
		/* It's possible an earlier status code set rval to a failure
		 * code, and we've encountered a later success.
		 */
	      case STATUS_Success:
		/* In "refreshes" (where we get replies), we probably
		 * still have a valid lease.  So "take no action" and
		 * the upper levels will keep retrying until the lease
		 * expires (or we rebind).
		 */
	      case STATUS_UnspecFail:
		/* For unknown codes...it's a soft (retryable) error. */
	      default:
		return ISC_FALSE;

		/* The server is telling us to use a multicast address, so
		 * we have to delete the unicast option from the active
		 * lease, then allow retransmission to occur normally.
		 * (XXX: It might be preferable in this case to retransmit
		 * sooner than the current interval, but for now we don't.)
		 */
	      case STATUS_UseMulticast:
		if(client->active_lease != NULL)
			delete_option(&dhcp_universe,
				      client->active_lease->options,
				      D6O_UNICAST);
		return ISC_FALSE;

		/* "When the client receives a NotOnLink status from the
		 *  server in response to a Request, the client can either
		 *  re-issue the Request without specifying any addresses
		 *  or restart the DHCP server discovery process."
		 *
		 * This is strange.  If competing server evaluation is
		 * useful (and therefore in the protocol), then why would
		 * a client's first reaction be to request from the same
		 * server on a different link?  Surely you'd want to
		 * re-evaluate your server selection.
		 *
		 * Well, I guess that's the answer.
		 */
	      case STATUS_NotOnLink:
		/* In this case, we need to rescind all current active
		 * bindings (just 'expire' them all normally, if early).
		 * They're no use to us on the wrong link.  Then head back
		 * to init, redo server selection and get new addresses.
		 */
		dhc6_withdraw_lease(client);
		return ISC_TRUE;

		/* "If the status code is NoAddrsAvail, the client has
		 *  received no usable addresses in the IA and may choose
		 *  to try obtaining addresses for the IA from another
		 *  server."
		 */
	      case STATUS_NoAddrsAvail:
		/* Head back to init, keeping any active bindings (!). */
		start_init6(client);
		break;

		/* -  sends a Request message if the IA contained a Status
		 *    Code option with the NoBinding status (and does not
		 *    send any additional Renew/Rebind messages)
		 */
	      case STATUS_NoBinding:
		if (client->advertised_leases != NULL)
			log_fatal("Impossible condition at %s:%d.", MDL);

		client->advertised_leases =
				dhc6_dup_lease(client->active_lease, MDL);
		start_selecting6(client);
		break;
	}

	return ISC_TRUE;
}

/* Look at a new and old lease, and make sure the new information is not
 * losing us any state.
 */
static isc_result_t
dhc6_check_reply(struct client_state *client, struct dhc6_lease *new)
{
	isc_boolean_t (*action)(struct client_state *, isc_result_t, unsigned);
	struct dhc6_ia *ia;
	struct dhc6_addr *addr;
	isc_result_t rval = ISC_R_SUCCESS;
	unsigned code;
	int nscore, sscore;

	if ((client == NULL) || (new == NULL))
		return ISC_R_INVALIDARG;

	switch (client->state) {
	      case S_SELECTING:
	      case S_REBOOTING:
		action = dhc6_select_action;
		break;

	      case S_RENEWING:
	      case S_REBINDING:
		action = dhc6_reply_action;
		break;

	      default:
		log_fatal("Impossible condition at %s:%d.", MDL);
		return ISC_R_CANCELED;
	}

	/* If there is a code to extract, and if there is some
	 * action to take based on that code, then take the action
	 * and do not continue.
	 */
	rval = dhc6_check_status(rval, new->options, "message", &code);
	if (action(client, rval, code))
		return ISC_R_CANCELED;

	for (ia = new->bindings ; ia != NULL ; ia = ia->next) {
		rval = dhc6_check_status(rval, ia->options, "IA_NA",
					 &code);
		if (action(client, rval, code))
			return ISC_R_CANCELED;

		for (addr = ia->addrs ; addr != NULL ;
		     addr = addr->next) {
			rval = dhc6_check_status(rval, addr->options,
						 "IAADDR", &code);
			if (action(client, rval, code))
				return ISC_R_CANCELED;
		}
	}

	switch (client->state) {
	      case S_SELECTING:
		/* Compare the new lease with the selected lease to make
		 * sure there is no risky business.
		 */
		nscore = dhc6_score_lease(client, new);
		sscore = dhc6_score_lease(client, client->selected_lease);
		if ((client->advertised_leases != NULL) &&
		    (nscore < (sscore / 2))) {
			/* XXX: An attacker might reply this way to make
			 * XXX: sure we latch onto their configuration.
			 * XXX: We might want to ignore the packet and
			 * XXX: schedule re-selection at the next timeout?
			 */
			log_error("PRC: BAIT AND SWITCH detected.  Score of "
				  "supplied lease (%d) is substantially "
				  "smaller than the advertised score (%d).  "
				  "Trying other servers.",
				  nscore, sscore);

			dhc6_lease_destroy(client->selected_lease, MDL);
			client->selected_lease = NULL;

			start_selecting6(client);

			return ISC_R_CANCELED;
		}
		break;

	      case S_RENEWING:
	      case S_REBINDING:
		/* This leaves one RFC3315 status check unimplemented:
		 *
		 * -  sends a Renew/Rebind if the IA is not in the Reply
		 *    message
		 *
		 * We rely on the scheduling system to note that the IA has
		 * not left Renewal/Rebinding/whatever since it still carries
		 * old times from the last successful binding.  So this is
		 * implemented actually, just not explicitly.
		 */
		break;

	      default:
		log_fatal("REALLY impossible condition at %s:%d.", MDL);
		return ISC_R_CANCELED;
	}

	return rval;
}

/* While in init state, we only collect advertisements.  If there happens
 * to be an advertisement with a preference option of 255, that's an
 * automatic exit.  Otherwise, we collect advertisements until our timeout
 * expires (client->RT).
 */
void
init_handler(struct packet *packet, struct client_state *client)
{
	struct dhc6_lease *lease;

	/* In INIT state, we send solicits, we only expect to get
	 * advertises (we don't support rapid commit yet).
	 */
	if (packet->dhcpv6_msg_type != DHCPV6_ADVERTISE)
		return;

	/* RFC3315 section 15.3 validation (same as 15.10 since we
	 * always include a client id).
	 */
	if (!valid_reply(packet, client)) {
		log_error("Invalid Advertise - rejecting.");
		return;
	}

	lease = dhc6_leaseify(packet);

	if (dhc6_check_advertise(lease) != ISC_R_SUCCESS) {
		log_debug("PRC: Lease failed to satisfy.");
		dhc6_lease_destroy(lease, MDL);
		return;
	}

	insert_lease(&client->advertised_leases, lease);

	/* According to RFC3315 section 17.1.2, the client MUST wait for
	 * the first RT before selecting a lease.  But on the 400th RT,
	 * we dont' want to wait the full timeout if we finally get an
	 * advertise.  We could probably wait a second, but ohwell,
	 * RFC3315 doesn't say so.
	 *
	 * If the lease is highest possible preference, 255, RFC3315 claims
	 * we should continue immediately even on the first RT.  We probably
	 * should not if the advertise contains less than one IA and address.
	 */
	if ((client->txcount > 1) ||
	    ((lease->pref == 255) &&
	    (dhc6_score_lease(client, lease) > 150))) {
		log_debug("RCV:  Advertisement immediately selected.");
		cancel_timeout(do_init6, client);
		start_selecting6(client);
	} else
		log_debug("RCV:  Advertisement recorded.");
}

/* Find the 'best' lease in the cache of advertised leases (usually).  From
 * RFC3315 Section 17.1.3:
 *
 *   Upon receipt of one or more valid Advertise messages, the client
 *   selects one or more Advertise messages based upon the following
 *   criteria.
 *
 *   -  Those Advertise messages with the highest server preference value
 *      are preferred over all other Advertise messages.
 *
 *   -  Within a group of Advertise messages with the same server
 *      preference value, a client MAY select those servers whose
 *      Advertise messages advertise information of interest to the
 *      client.  For example, the client may choose a server that returned
 *      an advertisement with configuration options of interest to the
 *      client.
 *
 *   -  The client MAY choose a less-preferred server if that server has a
 *      better set of advertised parameters, such as the available
 *      addresses advertised in IAs.
 *
 * Note that the first and third contradict each other.  The third should
 * probably be taken to mean that the client should prefer answers that
 * offer bindings, even if that violates the preference rule.
 *
 * The above also isn't deterministic where there are ties.  So the final
 * tiebreaker we add, if all other values are equal, is to compare the
 * server identifiers and to select the numerically lower one.
 */
static struct dhc6_lease *
dhc6_best_lease(struct client_state *client, struct dhc6_lease **head)
{
	struct dhc6_lease **rpos, *rval, **candp, *cand;
	int cscore, rscore;

	if (head == NULL || *head == NULL)
		return NULL;

	rpos = head;
	rval = *rpos;
	rscore = dhc6_score_lease(client, rval);
	candp = &rval->next;
	cand = *candp;

	log_debug("PRC: Considering best lease.");
	log_debug("PRC:  X-- Initial candidate %s (s: %d, p: %u).",
		  print_hex_1(rval->server_id.len,
			      rval->server_id.data, 48),
		  rscore, (unsigned)rval->pref);

	for (; cand != NULL ; candp = &cand->next, cand = *candp) {
		cscore = dhc6_score_lease(client, cand);

		log_debug("PRC:  X-- Candidate %s (s: %d, p: %u).",
			  print_hex_1(cand->server_id.len,
				      cand->server_id.data, 48),
			  cscore, (unsigned)cand->pref);

		/* Above you'll find quoted RFC3315 Section 17.1.3.
		 *
		 * The third clause tells us to give up on leases that
		 * have no bindings even if their preference is better.
		 * So where our 'selected' lease's score is less than 150
		 * (1 ia + 1 addr), choose any candidate >= 150.
		 *
		 * The first clause tells us to make preference the primary
		 * deciding factor.  So if it's lower, reject, if it's
		 * higher, select.
		 *
		 * The second clause tells us where the preference is
		 * equal, we should use 'our judgement' of what we like
		 * to see in an advertisement primarily.
		 *
		 * But there can still be a tie.  To make this deterministic,
		 * we compare the server identifiers and select the binary
		 * lowest.
		 *
		 * Since server id's are unique in this list, there is
		 * no further tie to break.
		 */
		if ((rscore < 150) && (cscore >= 150)) {
			log_debug("PRC:  | X-- Selected, has bndings.");
		} else if (cand->pref < rval->pref) {
			log_debug("PRC:  | X-- Rejected, lower preference.");
			continue;
		} else if (cand->pref > rval->pref) {
			log_debug("PRC:  | X-- Selected, higher preference.");
		} else if (cscore > rscore) {
			log_debug("PRC:  | X-- Selected, equal preference, "
				  "higher score.");
		} else if (cscore < rscore) {
			log_debug("PRC:  | X-- Rejected, equal preference, "
				  "lower score.");
			continue;
		} else if ((cand->server_id.len < rval->server_id.len) ||
			   ((cand->server_id.len == rval->server_id.len) &&
			    (memcmp(cand->server_id.data,
				    rval->server_id.data,
				    cand->server_id.len) < 0))) {
			log_debug("PRC:  | X-- Selected, equal preference, "
				  "equal score, binary lesser server ID.");
		} else {
			log_debug("PRC:  | X-- Rejected, equal preference, "
				  "equal score, binary greater server ID.");
			continue;
		}

		rpos = candp;
		rval = cand;
		rscore = cscore;
	}

	/* Remove the selected lease from the chain. */
	*rpos = rval->next;

	return rval;
}

/* Select a lease out of the advertised leases and setup state to try and
 * acquire that lease.
 */
void
start_selecting6(struct client_state *client)
{
	struct dhc6_lease *lease;

	if (client->advertised_leases == NULL) {
		log_error("Can not enter DHCPv6 SELECTING state with no "
			  "leases to select from!");
		return;
	}

	log_debug("PRC: Selecting best advertised lease.");
	client->state = S_SELECTING;

	lease = dhc6_best_lease(client, &client->advertised_leases);

	if (lease == NULL)
		log_fatal("Impossible error at %s:%d.", MDL);

	client->selected_lease = lease;

	/* Fetch a 24-bit transaction ID. */
	dhc6_new_xid(client);

	/* Set timers per RFC3315 section 18.1.1. */
	client->IRT = REQ_TIMEOUT;
	client->MRT = REQ_MAX_RT;
	client->MRC = REQ_MAX_RC;
	client->MRD = 0;

	dhc6_retrans_init(client);

	client->v6_handler = reply_handler;

	/* ("re")transmit the first packet. */
	do_select6(client);
}

/* Transmit a Request to select a lease offered in Advertisements.  In
 * the event of failure, either move on to the next-best advertised lease,
 * or head back to INIT state if there are none.
 */
void
do_select6(void *input)
{
	struct client_state *client;
	struct dhc6_lease *lease;
	struct data_string ds;
	TIME elapsed;
	int abort = ISC_FALSE;
	int send_ret;

	client = input;

	/* 'lease' is fewer characters to type. */
	lease = client->selected_lease;
	if (lease == NULL || lease->bindings == NULL) {
		log_error("Illegal to attempt selection without selecting "
			  "a lease.");
		return;
	}

	if ((client->MRC != 0) && (client->txcount > client->MRC)) {
		log_info("Max retransmission count exceeded.");
		abort = ISC_TRUE;
	}

	elapsed = cur_time - client->start_time;
	if ((client->MRD != 0) && (elapsed > client->MRD)) {
		log_info("Max retransmission duration exceeded.");
		abort = ISC_TRUE;
	}

	if (abort) {
		log_debug("PRC: Lease %s failed.",
			  print_hex_1(lease->server_id.len,
				      lease->server_id.data, 56));

		/* Get rid of the lease that timed/counted out. */
		dhc6_lease_destroy(lease, MDL);
		client->selected_lease = NULL;

		/* If there are more leases great.  If not, get more. */
		if (client->advertised_leases != NULL)
			start_selecting6(client);
		else
			start_init6(client);

		return;
	}

	/* Now make a packet that looks suspiciously like the one we
	 * got from the server.  But different.
	 *
	 * XXX: I guess IAID is supposed to be something the client
	 * indicates and uses as a key to its internal state.  It is
	 * kind of odd to ask the server for IA's whose IAID the client
	 * did not manufacture.  We first need a formal dhclient.conf
	 * construct for the iaid, then we can delve into this matter
	 * more properly.  In the time being, this will work.
	 */
	memset(&ds, 0, sizeof(ds));
	if (!buffer_allocate(&ds.buffer, 4, MDL)) {
		log_error("Unable to allocate memory for REQUEST.");
		return;
	}
	ds.data = ds.buffer->data;
	ds.len = 4;

	ds.buffer->data[0] = DHCPV6_REQUEST;
	memcpy(ds.buffer->data + 1, client->dhcpv6_transaction_id, 3);

	/* Form an elapsed option. */
	if ((elapsed < 0) || (elapsed > 655))
		client->elapsed = 0xffff;
	else
		client->elapsed = elapsed * 100;

	log_debug("XMT: Forming Request, %u ms elapsed.",
		  (unsigned)client->elapsed);

	client->elapsed = htons(client->elapsed);

	make_client6_options(client, &client->sent_options, lease,
			     DHCPV6_REQUEST);

	/* Fetch any configured 'sent' options (includes DUID) in wire format.
	 */
	dhcpv6_universe.encapsulate(&ds, NULL, NULL, client,
				    NULL, client->sent_options, &global_scope,
				    &dhcpv6_universe);

	/* Now append any IA_NA's, and within them any IAADDRs. */
	if (dhc6_add_ia(client, &ds, lease, DHCPV6_REQUEST) != ISC_R_SUCCESS) {
		data_string_forget(&ds, MDL);
		return;
	}

	log_info("XMT: Request on %s, interval %ld",
		 client->name ? client->name : client->interface->name,
		 (long int)client->RT);

	send_ret = send_packet6(client->interface,
				ds.data, ds.len, &DHCPv6DestAddr);
	if (send_ret != ds.len) {
		log_error("dhc6: send_packet6() sent %d of %d bytes",
			  send_ret, ds.len);
	}

	data_string_forget(&ds, MDL);

	add_timeout(cur_time + client->RT, do_select6, client, NULL, NULL);

	dhc6_retrans_advance(client);
}

/* For each IA in the lease, for each address in the IA, append that
 * information onto the packet-so-far.
 */
static isc_result_t
dhc6_add_ia(struct client_state *client, struct data_string *packet,
	    struct dhc6_lease *lease, u_int8_t message)
{
	struct data_string iads;
	struct data_string addrds;
	struct dhc6_addr *addr;
	struct dhc6_ia *ia;
	isc_result_t rval = ISC_R_SUCCESS;
	TIME t1, t2;

	memset(&iads, 0, sizeof(iads));
	memset(&addrds, 0, sizeof(addrds));
	for (ia = lease->bindings;
             ia != NULL && rval == ISC_R_SUCCESS;
             ia = ia->next) {
		if (!buffer_allocate(&iads.buffer, 12, MDL)) {
			log_error("Unable to allocate memory for IA_NA.");
			rval = ISC_R_NOMEMORY;
			break;
		}

		/* Copy the IAID into the packet buffer. */
		memcpy(iads.buffer->data, ia->iaid, 4);
		iads.data = iads.buffer->data;
		iads.len = 12;

                switch (message) {
                      case DHCPV6_REQUEST:
                      case DHCPV6_RENEW:
                      case DHCPV6_REBIND:
                        
                        t1 = client->config->requested_lease / 2;
                        t2 = t1 + (t1 / 2);
#if MAX_TIME > 0xffffffff
                        if (t1 > 0xffffffff)
                                t1 = 0xffffffff;
                        if (t2 > 0xffffffff)
                                t2 = 0xffffffff;
#endif
                        putULong(iads.buffer->data + 4, t1);
                        putULong(iads.buffer->data + 8, t2);

                        log_debug("XMT:  X-- IA_NA %s",
                                  print_hex_1(4, iads.data, 59));
                        log_debug("XMT:  | X-- Requested renew  +%u",
                                  (unsigned) t1);
                        log_debug("XMT:  | X-- Requested rebind +%u",
                                  (unsigned) t2);
                        break;

                      case DHCPV6_CONFIRM:
                      case DHCPV6_RELEASE:
		        /* Set t1 and t2 to zero; server will ignore them */
                        memset(iads.buffer->data + 4, 0, 8);
                        log_debug("XMT:  X-- IA_NA %s",
                                  print_hex_1(4, iads.buffer->data, 55));

                        break;

                      default:
                        log_fatal("Impossible condition at %s:%d.", MDL);
                }

		for (addr = ia->addrs ; addr != NULL ; addr = addr->next) {
			if (addr->address.len != 16) {
				log_error("Illegal IPv6 address length (%d), "
					  "ignoring.  (%s:%d)",
					  addr->address.len, MDL);
				continue;
			}

			if (!buffer_allocate(&addrds.buffer, 24, MDL)) {
				log_error("Unable to allocate memory for "
					  "IAADDR.");
				rval = ISC_R_NOMEMORY;
				break;
			}

			addrds.data = addrds.buffer->data;
			addrds.len = 24;

			/* Copy the address into the packet buffer. */
			memcpy(addrds.buffer->data, addr->address.iabuf, 16);

                        /* Copy in additional information as appropriate */
                        switch (message) {
                              case DHCPV6_REQUEST:
                              case DHCPV6_RENEW:
                              case DHCPV6_REBIND:
                                t1 = client->config->requested_lease;
                                t2 = t1 + 300;
                                putULong(addrds.buffer->data + 16, t1);
                                putULong(addrds.buffer->data + 20, t2);

                                log_debug("XMT:  | | X-- IAADDR %s",
                                          piaddr(addr->address));
                                log_debug("XMT:  | | | X-- Preferred "
                                          "lifetime +%u", (unsigned)t1);
                                log_debug("XMT:  | | | X-- Max lifetime +%u",
                                          (unsigned)t2);

                                break;

                              case DHCPV6_CONFIRM:
			        /*
                                 * Set preferred and max life to zero,
                                 * per 17.1.3.
                                 */
        			memset(addrds.buffer->data + 16, 0, 8);
                                log_debug("XMT:  | X-- Confirm Address %s",
                                          piaddr(addr->address));
                                break;

                              case DHCPV6_RELEASE:
                                /* Preferred and max life are irrelevant */
        			memset(addrds.buffer->data + 16, 0, 8);
                                log_debug("XMT:  | X-- Release Address %s",
                                          piaddr(addr->address));
                                break;

                              default:
                                log_fatal("Impossible condition at %s:%d.",
                                          MDL);
                        }

			append_option(&iads, &dhcpv6_universe, iaaddr_option,
                                      &addrds);
			data_string_forget(&addrds, MDL);
		}

		/*
                 * It doesn't make sense to make a request without an
		 * address.
		 */
		if (ia->addrs == NULL) {
			log_debug("!!!:  V IA_NA has no IAADDRs - removed.");
			rval = ISC_R_FAILURE;
		} else if (rval == ISC_R_SUCCESS) {
			log_debug("XMT:  V IA_NA appended.");
			append_option(packet, &dhcpv6_universe, ia_na_option,
				      &iads);
		}

		data_string_forget(&iads, MDL);
	}

        return rval;
}

/* reply_handler() accepts a Reply while we're attempting Select or Renew or
 * Rebind.  Basically any Reply packet.
 */
void
reply_handler(struct packet *packet, struct client_state *client)
{
	struct dhc6_lease *lease;
	isc_result_t check_status;

	if (packet->dhcpv6_msg_type != DHCPV6_REPLY)
		return;

	/* RFC3315 section 15.10 validation (same as 15.3 since we
	 * always include a client id).
	 */
	if (!valid_reply(packet, client)) {
		log_error("Invalid Advertise - rejecting.");
		return;
	}

	lease = dhc6_leaseify(packet);

	/* This is an out of memory condition...hopefully a temporary
	 * problem.  Returning now makes us try to retransmit later.
	 */
	if (lease == NULL)
		return;

	check_status = dhc6_check_reply(client, lease);
	if (check_status != ISC_R_SUCCESS) {
		dhc6_lease_destroy(lease, MDL);

		/* If no action was taken, but there is an error, then
		 * we wait for a retransmission.
		 */
		if (check_status != ISC_R_CANCELED)
			return;
	}

	/* We're done retransmititng at this point. */
	cancel_timeout(do_confirm6, client);
	cancel_timeout(do_select6, client);
	cancel_timeout(do_refresh6, client);
	cancel_timeout(do_release6, client);

	/* Action was taken, so now that we've torn down our scheduled
	 * retransmissions, return.
	 */
	if (check_status == ISC_R_CANCELED)
		return;

	if (client->selected_lease != NULL) {
		dhc6_lease_destroy(client->selected_lease, MDL);
		client->selected_lease = NULL;
	}

        /* If this is in response to a Release, clean up and return. */
	if (client->state == S_STOPPED) {
		if (client->active_lease == NULL)
			log_fatal("Impossible condition at %s:%d.", MDL);

                dhc6_lease_destroy(client->active_lease, MDL);
                client->active_lease = NULL;
                return;
        }

	/* If this is in response to a confirm, we use the lease we've
	 * already got, not the reply we were sent.
	 */
	if (client->state == S_REBOOTING) {
		if (client->active_lease == NULL)
			log_fatal("Impossible condition at %s:%d.", MDL);

		dhc6_lease_destroy(lease, MDL);
		start_bound(client);
		return;
	}

	/* Merge any bindings in the active lease (if there is one) into
	 * the new active lease.
	 */
	dhc6_merge_lease(client->active_lease, lease);

	/* Cleanup if a previous attempt to go bound failed. */
	if (client->old_lease != NULL) {
		dhc6_lease_destroy(client->old_lease, MDL);
		client->old_lease = NULL;
	}

	/* Make this lease active and BIND to it. */
	if (client->active_lease != NULL)
		client->old_lease = client->active_lease;
	client->active_lease = lease;

	/* We're done with the ADVERTISEd leases, if any. */
	while(client->advertised_leases != NULL) {
		lease = client->advertised_leases;
		client->advertised_leases = lease->next;

		dhc6_lease_destroy(lease, MDL);
	}

	start_bound(client);
}

/* DHCPv6 packets are a little sillier than they needed to be - the root
 * packet contains options, then IA's which contain options, then within
 * that IAADDR's which contain options.
 *
 * To sort this out at dhclient-script time (which fetches config parameters
 * in environment variables), start_bound() iterates over each IAADDR, and
 * calls this function to marshall an environment variable set that includes
 * the most-specific option values related to that IAADDR in particular.
 *
 * To acheive this, we load environment variables for the root options space,
 * then the IA, then the IAADDR.  Any duplicate option names will be
 * over-written by the later versions.
 */
static void
dhc6_marshall_values(const char *prefix, struct client_state *client,
		     struct dhc6_lease *lease, struct dhc6_ia *ia,
		     struct dhc6_addr *addr)
{
	/* Option cache contents, in descending order of
	 * scope.
	 */
	if ((lease != NULL) && (lease->options != NULL))
		script_write_params6(client, prefix, lease->options);
	if ((ia != NULL) && (ia->options != NULL))
		script_write_params6(client, prefix, ia->options);
	if ((addr != NULL) && (addr->options != NULL))
		script_write_params6(client, prefix, addr->options);

	/* addr fields. */
	if (addr != NULL) {
		/* Current practice is that all subnets are /64's, but
		 * some suspect this may not be permanent.
		 */
		client_envadd(client, prefix, "ip6_prefixlen", "%d", 64);
		client_envadd(client, prefix, "ip6_address", "%s",
			      piaddr(addr->address));
		client_envadd(client, prefix, "life_starts", "%d",
			      (int)(addr->starts));
		client_envadd(client, prefix, "preferred_life", "%d",
			      (int)(addr->preferred_life));
		client_envadd(client, prefix, "max_life", "%d",
			      (int)(addr->max_life));
	}

	/* ia fields. */
	if (ia != NULL) {
		client_envadd(client, prefix, "iaid", "%s",
			      print_hex_1(4, ia->iaid, 12));
		client_envadd(client, prefix, "starts", "%d",
			      (int)(ia->starts));
		client_envadd(client, prefix, "renew", "%u", ia->renew);
		client_envadd(client, prefix, "rebind", "%u", ia->rebind);
	}
}

/* Look at where the client's active lease is sitting.  If it's looking to
 * time out on renew, rebind, depref, or expiration, do those things.
 */
static void
dhc6_check_times(struct client_state *client)
{
	struct dhc6_lease *lease;
	struct dhc6_ia *ia;
	struct dhc6_addr *addr;
	TIME renew=MAX_TIME, rebind=MAX_TIME, depref=MAX_TIME,
	     lo_expire=MAX_TIME, hi_expire=0, tmp;
	int has_addrs = ISC_FALSE;

	lease = client->active_lease;

	/* Bit spammy.  We should probably keep record of scheduled
	 * events instead.
	 */
	cancel_timeout(start_renew6, client);
	cancel_timeout(start_rebind6, client);
	cancel_timeout(do_depref, client);
	cancel_timeout(do_expire, client);

	for(ia = lease->bindings ; ia != NULL ; ia = ia->next) {
		for (addr = ia->addrs ; addr != NULL ; addr = addr->next) {
			if(!(addr->flags & DHC6_ADDR_DEPREFFED)) {
				if (addr->preferred_life == 0xffffffff)
					tmp = MAX_TIME;
				else
					tmp = addr->starts +
					      addr->preferred_life;

				if (tmp < depref)
					depref = tmp;
			}

			if (!(addr->flags & DHC6_ADDR_EXPIRED)) {
				if (addr->max_life == 0xffffffff)
					tmp = MAX_TIME;
				else
					tmp = addr->starts + addr->max_life;

				if (tmp > hi_expire)
					hi_expire = tmp;
				if (tmp < lo_expire)
					lo_expire = tmp;

				has_addrs = ISC_TRUE;
			}
		}

		if (ia->renew == 0) {
			if (lo_expire != MAX_TIME)
				tmp = (lo_expire - ia->starts) / 2;
			else
				tmp = client->config->requested_lease / 2;

			tmp += ia->starts;
		} else if(ia->renew == 0xffffffff)
			tmp = MAX_TIME;
		else
			tmp = ia->starts + ia->renew;

		if (tmp < renew)
			renew = tmp;

		if (ia->rebind == 0) {
			if (lo_expire != MAX_TIME)
				tmp = (lo_expire - ia->starts) / 2;
			else
				tmp = client->config->requested_lease / 2;

			tmp += ia->starts + (tmp / 2);
		} else if (ia->renew == 0xffffffff)
			tmp = MAX_TIME;
		else
			tmp = ia->starts + ia->rebind;

		if (tmp < rebind)
			rebind = tmp;
	}

	/* If there are no addresses, give up, go to INIT.
	 * Note that if an address is unexpired with a date in the past,
	 * we're scheduling an expiration event to ocurr in the past.  We
	 * could probably optimize this to expire now (but then there's
	 * recursion).
	 *
	 * In the future, we may decide that we're done here, or to
	 * schedule a future request (using 4-pkt info-request model).
	 */
	if (has_addrs == ISC_FALSE) {
		dhc6_lease_destroy(client->active_lease, MDL);
		client->active_lease = NULL;

		/* Go back to the beginning. */
		start_init6(client);
		return;
	}

	switch(client->state) {
	      case S_BOUND:
		/* We'd like to hit renewing, but if rebinding has already
		 * passed (time warp), head straight there.
		 */
		if ((rebind > cur_time) && (renew < rebind)) {
			log_debug("PRC: Renewal event scheduled in %d seconds, "
				  "to run for %u seconds.",
				  (int)(renew - cur_time),
				  (unsigned)(rebind - renew));
			client->next_MRD = rebind - cur_time;
			add_timeout(renew, start_renew6, client, NULL, NULL);

			break;
		}
		/* FALL THROUGH */
	      case S_RENEWING:
		/* While actively renewing, MRD is bounded by the time
		 * we stop renewing and start rebinding.  This helps us
		 * process the state change on time.
		 */
		client->MRD = rebind - cur_time;
		if (rebind != MAX_TIME) {
			log_debug("PRC: Rebind event scheduled in %d seconds, "
				  "to run for %d seconds.",
				  (int)(rebind - cur_time),
				  (int)(hi_expire - rebind));
			client->next_MRD = hi_expire - cur_time;
			add_timeout(rebind, start_rebind6, client, NULL, NULL);
		}
		break;

	      case S_REBINDING:
		/* For now, we rebind up until the last lease expires.  In
		 * the future, we might want to start SOLICITing when we've
		 * depreffed an address.
		 */
		client->MRD = hi_expire - cur_time;
		break;

	      default:
		log_fatal("Impossible condition at %s:%d.", MDL);
	}

	/* Separately, set a time at which we will depref and expire
	 * leases.  This might happen with multiple addresses while we
	 * keep trying to refresh.
	 */
	if (depref != MAX_TIME) {
		log_debug("PRC: Depreference scheduled in %d seconds.",
			  (int)(depref - cur_time));
		add_timeout(depref, do_depref, client, NULL, NULL);
	}
	if (lo_expire != MAX_TIME) {
		log_debug("PRC: Expiration scheduled in %d seconds.",
			  (int)(lo_expire - cur_time));
		add_timeout(lo_expire, do_expire, client, NULL, NULL);
	}
}

/* In a given IA chain, find the IA with the same 'iaid'. */
static struct dhc6_ia *
find_ia(struct dhc6_ia *head, const char *id)
{
	struct dhc6_ia *ia;

	for (ia = head ; ia != NULL ; ia = ia->next) {
		if (memcmp(ia->iaid, id, 4) == 0)
			return ia;
	}

	return NULL;
}

/* In a given address chain, find a matching address. */
static struct dhc6_addr *
find_addr(struct dhc6_addr *head, struct iaddr *address)
{
	struct dhc6_addr *addr;

	for (addr = head ; addr != NULL ; addr = addr->next) {
		if ((addr->address.len == address->len) &&
		    (memcmp(addr->address.iabuf, address->iabuf,
			    address->len) == 0))
			return addr;
	}

	return NULL;
}

/* Merge the bindings from the source lease into the destination lease
 * structure, where they are missing.  We have to copy the stateful
 * objects rather than move them over, because later code needs to be
 * able to compare new versus old if they contain any bindings.
 */
static void
dhc6_merge_lease(struct dhc6_lease *src, struct dhc6_lease *dst)
{
	struct dhc6_ia *sia, *dia, *tia;
	struct dhc6_addr *saddr, *daddr, *taddr;
	int changes = 0;

	if ((dst == NULL) || (src == NULL))
		return;

	for (sia = src->bindings ; sia != NULL ; sia = sia->next) {
		dia = find_ia(dst->bindings, (char *)sia->iaid);

		if (dia == NULL) {
			tia = dhc6_dup_ia(sia, MDL);

			if (tia == NULL)
				log_fatal("Out of memory merging lease - "
					  "Unable to continue without losing "
					  "state! (%s:%d)", MDL);

			/* XXX: consider sorting? */
			tia->next = dst->bindings;
			dst->bindings = tia;
			changes = 1;
		} else {
			for (saddr = sia->addrs ; saddr != NULL ;
			     saddr = saddr->next) {
				daddr = find_addr(dia->addrs,
						  &saddr->address);

				if (daddr == NULL) {
					taddr = dhc6_dup_addr(saddr, MDL);

					if (taddr == NULL)
						log_fatal("Out of memory "
							  "merging lease - "
							  "Unable to continue "
							  "without losing "
							  "state! (%s:%d)",
							  MDL);

					/* XXX: consider sorting? */
					taddr->next = dia->addrs;
					dia->addrs = taddr;
					changes = 1;
				}
			}
		}
	}

	/* If we made changes, reset the score to 0 so it is recalculated. */
	if (changes)
		dst->score = 0;
}

/* We've either finished selecting or succeeded in Renew or Rebinding our
 * lease.  In all cases we got a Reply.  Give dhclient-script a tickle
 * to inform it about the new values, and then lay in wait for the next
 * event.
 */
void
start_bound(struct client_state *client)
{
	struct dhc6_ia *ia, *oldia;
	struct dhc6_addr *addr, *oldaddr;
	struct dhc6_lease *lease, *old;
	const char *reason;
	TIME dns_update_offset = 1;

	lease = client->active_lease;
	if (lease == NULL) {
		log_error("Cannot enter bound state unless an active lease "
			  "is selected.");
		return;
	}
	old = client->old_lease;

	client->v6_handler = bound_handler;

	switch (client->state) {
	      case S_SELECTING:
	      case S_REBOOTING: /* Pretend we got bound. */
		reason = "BOUND6";
		break;

	      case S_RENEWING:
		reason = "RENEW6";
		break;

	      case S_REBINDING:
		reason = "REBIND6";
		break;

	      default:
		log_fatal("Impossible condition at %s:%d.", MDL);
		/* Silence compiler warnings. */
		return;
	}

	log_debug("PRC: Bound to lease %s.",
		  print_hex_1(client->active_lease->server_id.len,
			      client->active_lease->server_id.data, 55));
	client->state = S_BOUND;

	write_client6_lease(client, lease, 0, 1);

	oldia = NULL;
	for (ia = lease->bindings ; ia != NULL ; ia = ia->next) {
		if (old != NULL)
			oldia = find_ia(old->bindings, (char *)ia->iaid);
		else
			oldia = NULL;

		for (addr = ia->addrs ; addr != NULL ; addr = addr->next) {
			if (oldia != NULL)
				oldaddr = find_addr(oldia->addrs,
						    &addr->address);
			else
				oldaddr = NULL;

			if (oldaddr == NULL)
				dhclient_schedule_updates(client,
							  &addr->address,
							  dns_update_offset++);

			/* Shell out to setup the new binding. */
			script_init(client, reason, NULL);

			if (old != NULL)
				dhc6_marshall_values("old_", client, old,
						     oldia, oldaddr);
			dhc6_marshall_values("new_", client, lease, ia, addr);

			script_go(client);
		}

		/* XXX: maybe we should loop on the old values instead? */
		if (ia->addrs == NULL) {
			script_init(client, reason, NULL);

			if (old != NULL)
				dhc6_marshall_values("old_", client, old,
						     oldia,
						     oldia != NULL ?
							 oldia->addrs : NULL);

			dhc6_marshall_values("new_", client, lease, ia,
					     NULL);

			script_go(client);
		}
	}

	/* XXX: maybe we should loop on the old values instead? */
	if (lease->bindings == NULL) {
		script_init(client, reason, NULL);

		if (old != NULL)
			dhc6_marshall_values("old_", client, old,
					     old->bindings,
					     (old->bindings != NULL) ?
						old->bindings->addrs : NULL);

		dhc6_marshall_values("new_", client, lease, NULL, NULL);

		script_go(client);
	}

	go_daemon();

	if (client->old_lease != NULL) {
		dhc6_lease_destroy(client->old_lease, MDL);
		client->old_lease = NULL;
	}

	/* Schedule events. */
	dhc6_check_times(client);
}

/* While bound, ignore packets.  In the future we'll want to answer
 * Reconfigure-Request messages and the like.
 */
void
bound_handler(struct packet *packet, struct client_state *client)
{
	log_debug("RCV: Input packets are ignored once bound.");
}

/* start_renew6() gets us all ready to go to start transmitting Renew packets.
 * Note that client->MRD must be set before entering this function - it must
 * be set to the time at which the client should start Rebinding.
 */
void
start_renew6(void *input)
{
	struct client_state *client;

	client = (struct client_state *)input;

	log_info("PRC: Renewing lease on %s.",
		 client->name ? client->name : client->interface->name);
	client->state = S_RENEWING;

	client->v6_handler = reply_handler;

	/* Times per RFC3315 section 18.1.3. */
	client->IRT = REN_TIMEOUT;
	client->MRT = REN_MAX_RT;
	client->MRC = 0;
	/* MRD is special in renew - we need to set it by checking timer
	 * state.
	 */
	client->MRD = client->next_MRD;

	dhc6_retrans_init(client);

	client->refresh_type = DHCPV6_RENEW;
	do_refresh6(client);
}

/* do_refresh6() transmits one DHCPv6 packet, be it a Renew or Rebind, and
 * gives the retransmission state a bump for the next time.  Note that
 * client->refresh_type must be set before entering this function.
 */
void
do_refresh6(void *input)
{
	struct option_cache *oc;
	struct sockaddr_in6 unicast, *dest_addr = &DHCPv6DestAddr;
	struct data_string ds;
	struct client_state *client;
	struct dhc6_lease *lease;
	TIME elapsed;
	int send_ret;

	client = (struct client_state *)input;

	lease = client->active_lease;
	if (lease == NULL) {
		log_error("Cannot renew without an active binding.");
		return;
	}

	/* Ensure we're emitting a valid message type. */
	switch (client->refresh_type) {
	      case DHCPV6_RENEW:
	      case DHCPV6_REBIND:
		break;

	      default:
		log_fatal("Internal inconsistency (%d) at %s:%d.",
			  client->refresh_type, MDL);
	}

	elapsed = cur_time - client->start_time;
	if (((client->MRC != 0) && (client->txcount > client->MRC)) ||
	    ((client->MRD != 0) && (elapsed >= client->MRD))) {
		/* We're done.  Move on to the next phase, if any. */
		dhc6_check_times(client);
		return;
	}

	/*
	 * Check whether the server has sent a unicast option; if so, we can
	 * use the address it specified.
	 */
	oc = lookup_option(&dhcpv6_universe, lease->options, D6O_UNICAST);
	if (oc && evaluate_option_cache(&ds, NULL, NULL, NULL,
                                        lease->options, NULL, &global_scope,
					oc, MDL)) {
		if (ds.len < 16) {
			log_error("Invalid unicast option length %d.", ds.len);
		} else {
			memset(&unicast, 0, sizeof(DHCPv6DestAddr));
			unicast.sin6_family = AF_INET6;
			unicast.sin6_port = remote_port;
			memcpy(&unicast.sin6_addr, ds.data, 16);
			dest_addr = &unicast;
		}

		data_string_forget(&ds, MDL);
	}

	/* Commence forming a renew packet. */
	memset(&ds, 0, sizeof(ds));
	if (!buffer_allocate(&ds.buffer, 4, MDL)) {
		log_error("Unable to allocate memory for packet.");
		return;
	}
	ds.data = ds.buffer->data;
	ds.len = 4;

	ds.buffer->data[0] = client->refresh_type;
	memcpy(ds.buffer->data + 1, client->dhcpv6_transaction_id, 3);

	if ((elapsed < 0) || (elapsed > 655))
		client->elapsed = 0xffff;
	else
		client->elapsed = elapsed * 100;

	log_debug("XMT: Forming %s, %u ms elapsed.",
		  dhcpv6_type_names[client->refresh_type],
		  (unsigned)client->elapsed);

	client->elapsed = htons(client->elapsed);

	make_client6_options(client, &client->sent_options, lease,
			     client->refresh_type);

	/* Put in any options from the sent cache. */
	dhcpv6_universe.encapsulate(&ds, NULL, NULL, client, NULL,
				    client->sent_options, &global_scope,
				    &dhcpv6_universe);

        /* Append IA's */
	if (dhc6_add_ia(client, &ds, lease,
                        client->refresh_type) != ISC_R_SUCCESS) {
		data_string_forget(&ds, MDL);
		return;
	}

	log_info("XMT: %s on %s, interval %ld",
		 dhcpv6_type_names[client->refresh_type],
		 client->name ? client->name : client->interface->name,
		 (long int)client->RT);

	send_ret = send_packet6(client->interface, ds.data, ds.len, dest_addr);

	if (send_ret != ds.len) {
		log_error("dhc6: send_packet6() sent %d of %d bytes",
			  send_ret, ds.len);
	}

	data_string_forget(&ds, MDL);

	add_timeout(cur_time + client->RT, do_refresh6, client, NULL, NULL);

	dhc6_retrans_advance(client);
}

/* start_rebind6() gets us all set up to go and rebind a lease.  Note that
 * client->MRD must be set before entering this function.  In this case,
 * MRD must be set to the maximum time any address in the packet will
 * expire.
 */
void
start_rebind6(void *input)
{
	struct client_state *client;

	client = (struct client_state *)input;

	log_info("PRC: Rebinding lease on %s.",
		 client->name ? client->name : client->interface->name);
	client->state = S_REBINDING;

	client->v6_handler = reply_handler;

	/* Times per RFC3315 section 18.1.4. */
	client->IRT = REB_TIMEOUT;
	client->MRT = REB_MAX_RT;
	client->MRC = 0;
	/* MRD is special in rebind - it's determined by the timer
	 * state.
	 */
	client->MRD = client->next_MRD;

	dhc6_retrans_init(client);

	client->refresh_type = DHCPV6_REBIND;
	do_refresh6(client);
}

/* do_depref() runs through a given lease's addresses, for each that has
 * not yet been depreffed, shells out to the dhclient-script to inform it
 * of the status change.  The dhclient-script should then do...something...
 * to encourage applications to move off the address and onto one of the
 * remaining 'preferred' addresses.
 */
void
do_depref(void *input)
{
	struct client_state *client;
	struct dhc6_lease *lease;
	struct dhc6_ia *ia;
	struct dhc6_addr *addr;

	client = (struct client_state *)input;

	lease = client->active_lease;
	if (lease == NULL)
		return;

	for (ia = lease->bindings ; ia != NULL ; ia = ia->next) {
		for (addr = ia->addrs ; addr != NULL ; addr = addr->next) {
			if (addr->flags & DHC6_ADDR_DEPREFFED)
				continue;

			if (addr->starts + addr->preferred_life <= cur_time) {
				script_init(client, "DEPREF6", NULL);
				dhc6_marshall_values("cur_", client, lease,
						     ia, addr);
				script_go(client);

				log_info("PRC: Address %s depreferred.",
					 print_hex_1(addr->address.len,
						     addr->address.iabuf,
						     50));


				addr->flags |= DHC6_ADDR_DEPREFFED;

				/* Remove DDNS bindings at depref time. */
				if (client->config->do_forward_update)
					client_dns_update(client, 0, 0,
							  &addr->address);
			}
		}
	}

	dhc6_check_times(client);
}

/* do_expire() searches through all the addresses on a given lease, and
 * expires/removes any addresses that are no longer valid.
 */
void
do_expire(void *input)
{
	struct client_state *client;
	struct dhc6_lease *lease;
	struct dhc6_ia *ia;
	struct dhc6_addr *addr;
	int has_addrs = ISC_FALSE;

	client = (struct client_state *)input;

	lease = client->active_lease;
	if (lease == NULL)
		return;

	for (ia = lease->bindings ; ia != NULL ; ia = ia->next) {
		for (addr = ia->addrs ; addr != NULL ; addr = addr->next) {
			if (addr->flags & DHC6_ADDR_EXPIRED)
				continue;

			if (addr->starts + addr->max_life <= cur_time) {
				script_init(client, "EXPIRE6", NULL);
				dhc6_marshall_values("old_", client, lease,
						     ia, addr);
				script_go(client);

				addr->flags |= DHC6_ADDR_EXPIRED;

				log_info("PRC: Address %s expired.",
					 print_hex_1(addr->address.len,
						     addr->address.iabuf,
						     50));

				/* We remove DNS records at depref time, but
				 * it is possible that we might get here
				 * without depreffing.
				 */
				if (client->config->do_forward_update &&
				    !(addr->flags & DHC6_ADDR_DEPREFFED))
					client_dns_update(client, 0, 0,
							  &addr->address);

				continue;
			}

			has_addrs = ISC_TRUE;
		}
	}

	/* Clean up empty leases. */
	if (has_addrs == ISC_FALSE) {
		log_info("PRC: Bound lease is devoid of active addresses."
			 "  Re-initializing.");

		dhc6_lease_destroy(lease, MDL);
		client->active_lease = NULL;

		start_init6(client);
		return;
	}

	/* Schedule the next run through. */
	dhc6_check_times(client);
}

/*
 * Run client script to unconfigure interface.
 * Called with reason STOP6 when dhclient -x is run, or with reason
 * RELEASE6 when server has replied to a Release message.
 */
void
unconfigure6(struct client_state *client, const char *reason)
{
	struct dhc6_ia *ia;
	struct dhc6_addr *addr;

	if (client->active_lease == NULL)
		return;

	for (ia = client->active_lease->bindings ; ia != NULL ; ia = ia->next) {
		for (addr = ia->addrs ; addr != NULL ; addr = addr->next) {
			script_init(client, reason, NULL);
			dhc6_marshall_values("old_", client, 
					     client->active_lease, ia, addr);
			script_go(client);
		 
			if (client->config->do_forward_update)
				client_dns_update(client, 0, 0, &addr->address);
		}
	}
}

/* make_client6_options() fetches option caches relevant to the client's
 * scope and places them into the sent_options cache.  This cache is later
 * used to populate DHCPv6 output packets with options.
 */
static void
make_client6_options(struct client_state *client, struct option_state **op,
		     struct dhc6_lease *lease, u_int8_t message)
{
	struct option_cache *oc;
	struct option **req;
	struct data_string oro;
	int buflen, i;

	if ((op == NULL) || (client == NULL))
		return;

	if (*op)
		option_state_dereference(op, MDL);

	/* Create a cache to carry options to transmission. */
	option_state_allocate(op, MDL);

	/* Create and store an 'elapsed time' option in the cache. */
	oc = NULL;
	if (option_cache_allocate(&oc, MDL)) {
		const unsigned char *cdata;

		cdata = (unsigned char *)&client->elapsed;

		if (make_const_data(&oc->expression, cdata, 2, 0, 0, MDL)) {
			option_reference(&oc->option, elapsed_option, MDL);
			save_option(&dhcpv6_universe, *op, oc);
		}

		option_cache_dereference(&oc, MDL);
	}

	/* See if the user configured a DUID in a relevant scope.  If not,
	 * introduce our default manufactured id.
	 */
	if ((oc = lookup_option(&dhcpv6_universe, *op,
				D6O_CLIENTID)) == NULL) {
		if (!option_cache(&oc, &default_duid, NULL, clientid_option,
				  MDL))
			log_fatal("Failure assembling a DUID.");

		save_option(&dhcpv6_universe, *op, oc);
		option_cache_dereference(&oc, MDL);
	}

	/* In cases where we're responding to a single server, put the
	 * server's id in the response.
	 *
	 * Note that lease is NULL for SOLICIT or INFO request messages,
	 * and otherwise MUST be present.
	 */
	if (lease == NULL) {
		if ((message != DHCPV6_SOLICIT) &&
		    (message != DHCPV6_INFORMATION_REQUEST))
			log_fatal("Impossible condition at %s:%d.", MDL);
	} else if ((message != DHCPV6_REBIND) &&
		   (message != DHCPV6_CONFIRM)) {
		oc = lookup_option(&dhcpv6_universe, lease->options,
				   D6O_SERVERID);
		if (oc != NULL)
			save_option(&dhcpv6_universe, *op, oc);
	}

	/* 'send dhcp6.oro foo;' syntax we used in 4.0.0a1/a2 has been
	 * deprecated by adjustments to the 'request' syntax also used for
	 * DHCPv4.
	 */
	if (lookup_option(&dhcpv6_universe, *op, D6O_ORO) == NULL)
		log_error("'send dhcp6.oro' syntax is deprecated, please "
			  "use the 'request' syntax ("man dhclient.conf").");

	/* Construct and store an ORO (Option Request Option).  It is a
	 * fatal error to fail to send an ORO (of at least zero length).
	 *
	 * Discussion:  RFC3315 appears to be inconsistent in its statements
	 * of whether or not the ORO is mandatory.  In section 18.1.1
	 * ("Creation and Transmission of Request Messages"):
	 *
	 *    The client MUST include an Option Request option (see section
	 *    22.7) to indicate the options the client is interested in
	 *    receiving.  The client MAY include options with data values as
	 *    hints to the server about parameter values the client would like
	 *    to have returned.
	 *
	 * This MUST is missing from the creation/transmission of other
	 * messages (such as Renew and Rebind), and the section 22.7 ("Option
	 * Request Option" format and definition):
	 *
	 *    A client MAY include an Option Request option in a Solicit,
	 *    Request, Renew, Rebind, Confirm or Information-request message to
	 *    inform the server about options the client wants the server to
	 *    send to the client.  A server MAY include an Option Request
	 *    option in a Reconfigure option to indicate which options the
	 *    client should request from the server.
	 *
	 * seems to relax the requirement from MUST to MAY (and still other
	 * language in RFC3315 supports this).
	 *
	 * In lieu of a clarification of RFC3315, we will conform with the
	 * MUST.  Instead of an absent ORO, we will if there are no options
	 * to request supply an empty ORO.  Theoretically, an absent ORO is
	 * difficult to interpret (does the client want all options or no
	 * options?).  A zero-length ORO is intuitively clear: requesting
	 * nothing.
	 */
	memset(&oro, 0, sizeof(oro));
	buflen = 32;
	if (!buffer_allocate(&oro.buffer, buflen, MDL))
		log_fatal("Out of memory constructing DHCPv6 ORO.");
	oro.data = oro.buffer->data;
	req = client->config->requested_options;
	if (req != NULL) {
		for (i = 0 ; req[i] != NULL ; i++) {
			if (buflen == oro.len) {
				struct buffer *tmpbuf = NULL;

				buflen += 32;

				/* Shell game. */
				buffer_reference(&tmpbuf, oro.buffer, MDL);
				buffer_dereference(&oro.buffer, MDL);

				if (!buffer_allocate(&oro.buffer, buflen, MDL))
					log_fatal("Out of memory resizing "
						  "DHCPv6 ORO buffer.");

				oro.data = oro.buffer->data;

				memcpy(oro.buffer->data, tmpbuf->data,
				       oro.len);

				buffer_dereference(&tmpbuf, MDL);
			}

			if (req[i]->universe == &dhcpv6_universe) {
				/* Append the code to the ORO. */
				putUShort(oro.buffer->data + oro.len,
					  req[i]->code);
				oro.len += 2;
			}
		}
	}

	oc = NULL;
	if (option_cache_allocate(&oc, MDL) &&
	    make_const_data(&oc->expression, oro.data, oro.len, 0, 0, MDL)) {
		option_reference(&oc->option, oro_option, MDL);
		save_option(&dhcpv6_universe, *op, oc);
	} else {
		log_fatal("Unable to create ORO option cache.");
	}

	data_string_forget(&oro, MDL);

	/* Bring in any configured options to send. */
	if (client->config->on_transmission)
		execute_statements_in_scope(NULL, NULL, NULL, client,
					    lease ? lease->options : NULL,
					    *op, &global_scope,
					    client->config->on_transmission,
					    NULL);

	/* RFC3315 says we MUST inclue an ORO in Requests.  If we have it
	 * in the cache for one, we have it for both, so it's fatal either
	 * way (may as well fail early).
	 */
	if (lookup_option(&dhcpv6_universe, *op, D6O_ORO) == NULL)
		log_fatal("Internal inconsistency: no dhcp6.oro in transmit "
			  "state.");
}

/* A clone of the DHCPv4 script_write_params() minus the DHCPv4-specific
 * filename, server-name, etc specifics.
 *
 * Simply, store all values present in all universes of the option state
 * (probably derived from a DHCPv6 packet) into environment variables
 * named after the option names (and universe names) but with the 'prefix'
 * prepended.
 *
 * Later, dhclient-script may compare for example "new_time_servers" and
 * "old_time_servers" for differences, and only upon detecting a change
 * bother to rewrite ntp.conf and restart it.  Or something along those
 * generic lines.
 */
static void
script_write_params6(struct client_state *client, const char *prefix,
		     struct option_state *options)
{
	struct envadd_state es;
	int i;

	if (options == NULL)
		return;

	es.client = client;
	es.prefix = prefix;

	for (i = 0 ; i < options->universe_count ; i++) {
		option_space_foreach(NULL, NULL, client, NULL, options,
				     &global_scope, universes[i], &es,
				     client_option_envadd);
	}
}

#endif /* DHCPv6 */