src/usr.sbin/dhcpd/memory.c

/*	$OpenBSD: memory.c,v 1.31 2022/01/28 06:33:27 guenther Exp $ */

/*
 * Copyright (c) 1995, 1996, 1997, 1998 The Internet Software Consortium.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of The Internet Software Consortium nor the names
 *    of its contributors may be used to endorse or promote products derived
 *    from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE INTERNET SOFTWARE CONSORTIUM AND
 * CONTRIBUTORS ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES,
 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL THE INTERNET SOFTWARE CONSORTIUM OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 * This software has been written for the Internet Software Consortium
 * by Ted Lemon <mellon@fugue.com> in cooperation with Vixie
 * Enterprises.  To learn more about the Internet Software Consortium,
 * see ``http://www.vix.com/isc''.  To learn more about Vixie
 * Enterprises, see ``http://www.vix.com''.
 */

#include <sys/types.h>
#include <sys/socket.h>

#include <arpa/inet.h>

#include <net/if.h>

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

#include "dhcp.h"
#include "tree.h"
#include "dhcpd.h"
#include "log.h"
#include "sync.h"

struct subnet *subnets;
static struct shared_network *shared_networks;
static struct hash_table *host_hw_addr_hash;
static struct hash_table *host_uid_hash;
static struct hash_table *lease_uid_hash;
static struct hash_table *lease_ip_addr_hash;
static struct hash_table *lease_hw_addr_hash;
static struct lease *dangling_leases;

static struct hash_table *vendor_class_hash;
static struct hash_table *user_class_hash;

extern int syncsend;

void
enter_host(struct host_decl *hd)
{
	struct host_decl *hp = NULL, *np = NULL;

	hd->n_ipaddr = NULL;
	if (hd->interface.hlen) {
		if (!host_hw_addr_hash)
			host_hw_addr_hash = new_hash();
		else
			hp = (struct host_decl *)hash_lookup(host_hw_addr_hash,
			    hd->interface.haddr, hd->interface.hlen);

		/*
		 * If there isn't already a host decl matching this
		 * address, add it to the hash table.
		 */
		if (!hp)
			add_hash(host_hw_addr_hash, hd->interface.haddr,
			    hd->interface.hlen, (unsigned char *)hd);
	}

	/*
	 * If there was already a host declaration for this hardware
	 * address, add this one to the end of the list.
	 */
	if (hp) {
		for (np = hp; np->n_ipaddr; np = np->n_ipaddr)
			;
		np->n_ipaddr = hd;
	}

	if (hd->group->options[DHO_DHCP_CLIENT_IDENTIFIER]) {
		if (!tree_evaluate(
		    hd->group->options[DHO_DHCP_CLIENT_IDENTIFIER]))
			return;

		/* If there's no uid hash, make one; otherwise, see if
		   there's already an entry in the hash for this host. */
		if (!host_uid_hash) {
			host_uid_hash = new_hash();
			hp = NULL;
		} else
			hp = (struct host_decl *)hash_lookup(host_uid_hash,
			    hd->group->options[DHO_DHCP_CLIENT_IDENTIFIER]->value,
			    hd->group->options[DHO_DHCP_CLIENT_IDENTIFIER]->len);

		/*
		 * If there's already a host declaration for this
		 * client identifier, add this one to the end of the
		 * list.  Otherwise, add it to the hash table.
		 */
		if (hp) {
			/* Don't link it in twice... */
			if (!np) {
				for (np = hp; np->n_ipaddr;
				    np = np->n_ipaddr)
					;
				np->n_ipaddr = hd;
			}
		} else {
			add_hash(host_uid_hash,
			    hd->group->options[DHO_DHCP_CLIENT_IDENTIFIER]->value,
			    hd->group->options[DHO_DHCP_CLIENT_IDENTIFIER]->len,
			    (unsigned char *)hd);
		}
	}
}

struct host_decl *
find_hosts_by_haddr(int htype, unsigned char *haddr, int hlen)
{
	return (struct host_decl *)hash_lookup(host_hw_addr_hash,
	    haddr, hlen);
}

struct host_decl *
find_hosts_by_uid(unsigned char *data, int len)
{
	return (struct host_decl *)hash_lookup(host_uid_hash, data, len);
}

/*
 * More than one host_decl can be returned by find_hosts_by_haddr or
 * find_hosts_by_uid, and each host_decl can have multiple addresses.
 * Loop through the list of hosts, and then for each host, through the
 * list of addresses, looking for an address that's in the same shared
 * network as the one specified.    Store the matching address through
 * the addr pointer, update the host pointer to point at the host_decl
 * that matched, and return the subnet that matched.
 */
struct subnet *
find_host_for_network(struct host_decl **host, struct iaddr *addr,
    struct shared_network *share)
{
	struct subnet *subnet;
	struct iaddr ip_address;
	struct host_decl *hp;
	int i;

	for (hp = *host; hp; hp = hp->n_ipaddr) {
		if (!hp->fixed_addr || !tree_evaluate(hp->fixed_addr))
			continue;
		for (i = 0; i < hp->fixed_addr->len; i += 4) {
			ip_address.len = 4;
			memcpy(ip_address.iabuf, hp->fixed_addr->value + i, 4);
			subnet = find_grouped_subnet(share, ip_address);
			if (subnet) {
				*addr = ip_address;
				*host = hp;
				return subnet;
			}
		}
	}
	return NULL;
}

void
new_address_range(struct iaddr low, struct iaddr high, struct subnet *subnet,
    int dynamic)
{
	struct lease *address_range, *lp, *plp;
	struct iaddr net;
	int min, max, i;
	char lowbuf[16], highbuf[16], netbuf[16];
	struct shared_network *share = subnet->shared_network;
	struct hostent *h;
	struct in_addr ia;

	/* All subnets should have attached shared network structures. */
	if (!share) {
		strlcpy(netbuf, piaddr(subnet->net), sizeof(netbuf));
		fatalx("No shared network for network %s (%s)",
		    netbuf, piaddr(subnet->netmask));
	}

	/* Initialize the hash table if it hasn't been done yet. */
	if (!lease_uid_hash)
		lease_uid_hash = new_hash();
	if (!lease_ip_addr_hash)
		lease_ip_addr_hash = new_hash();
	if (!lease_hw_addr_hash)
		lease_hw_addr_hash = new_hash();

	/* Make sure that high and low addresses are in same subnet. */
	net = subnet_number(low, subnet->netmask);
	if (!addr_eq(net, subnet_number(high, subnet->netmask))) {
		strlcpy(lowbuf, piaddr(low), sizeof(lowbuf));
		strlcpy(highbuf, piaddr(high), sizeof(highbuf));
		strlcpy(netbuf, piaddr(subnet->netmask), sizeof(netbuf));
		fatalx("Address range %s to %s, netmask %s spans %s!",
		    lowbuf, highbuf, netbuf, "multiple subnets");
	}

	/* Make sure that the addresses are on the correct subnet. */
	if (!addr_eq(net, subnet->net)) {
		strlcpy(lowbuf, piaddr(low), sizeof(lowbuf));
		strlcpy(highbuf, piaddr(high), sizeof(highbuf));
		strlcpy(netbuf, piaddr(subnet->netmask), sizeof(netbuf));
		fatalx("Address range %s to %s not on net %s/%s!",
		    lowbuf, highbuf, piaddr(subnet->net), netbuf);
	}

	/* Get the high and low host addresses... */
	max = host_addr(high, subnet->netmask);
	min = host_addr(low, subnet->netmask);

	/* Allow range to be specified high-to-low as well as low-to-high. */
	if (min > max) {
		max = min;
		min = host_addr(high, subnet->netmask);
	}

	/* Get a lease structure for each address in the range. */
	address_range = calloc(max - min + 1, sizeof(struct lease));
	if (!address_range) {
		strlcpy(lowbuf, piaddr(low), sizeof(lowbuf));
		strlcpy(highbuf, piaddr(high), sizeof(highbuf));
		fatalx("No memory for address range %s-%s.", lowbuf, highbuf);
	}
	memset(address_range, 0, (sizeof *address_range) * (max - min + 1));

	/* Fill in the last lease if it hasn't been already... */
	if (!share->last_lease)
		share->last_lease = &address_range[0];

	/* Fill out the lease structures with some minimal information. */
	for (i = 0; i < max - min + 1; i++) {
		address_range[i].ip_addr = ip_addr(subnet->net,
		    subnet->netmask, i + min);
		address_range[i].starts = address_range[i].timestamp =
		    MIN_TIME;
		address_range[i].ends = MIN_TIME;
		address_range[i].subnet = subnet;
		address_range[i].shared_network = share;
		address_range[i].flags = dynamic ? DYNAMIC_BOOTP_OK : 0;

		memcpy(&ia, address_range[i].ip_addr.iabuf, 4);

		if (subnet->group->get_lease_hostnames) {
			h = gethostbyaddr((char *)&ia, sizeof ia, AF_INET);
			if (!h)
				log_warnx("No hostname for %s", inet_ntoa(ia));
			else {
				address_range[i].hostname = strdup(h->h_name);
				if (address_range[i].hostname == NULL)
					fatalx("no memory for hostname %s.",
					    h->h_name);
			}
		}

		/* Link this entry into the list. */
		address_range[i].next = share->leases;
		address_range[i].prev = NULL;
		share->leases = &address_range[i];
		if (address_range[i].next)
			address_range[i].next->prev = share->leases;
		add_hash(lease_ip_addr_hash, address_range[i].ip_addr.iabuf,
		    address_range[i].ip_addr.len,
		    (unsigned char *)&address_range[i]);
	}

	/* Find out if any dangling leases are in range... */
	plp = NULL;
	for (lp = dangling_leases; lp; lp = lp->next) {
		struct iaddr lnet;
		int lhost;

		lnet = subnet_number(lp->ip_addr, subnet->netmask);
		lhost = host_addr(lp->ip_addr, subnet->netmask);

		/* If it's in range, fill in the real lease structure with
		   the dangling lease's values, and remove the lease from
		   the list of dangling leases. */
		if (addr_eq(lnet, subnet->net) && lhost >= i && lhost <= max) {
			if (plp) {
				plp->next = lp->next;
			} else {
				dangling_leases = lp->next;
			}
			lp->next = NULL;
			address_range[lhost - i].hostname = lp->hostname;
			address_range[lhost - i].client_hostname =
			    lp->client_hostname;
			supersede_lease(&address_range[lhost - i], lp, 0);
			free(lp);
			return;
		} else
			plp = lp;
	}
}

struct subnet *
find_subnet(struct iaddr addr)
{
	struct subnet *rv;

	for (rv = subnets; rv; rv = rv->next_subnet) {
		if (addr_eq(subnet_number(addr, rv->netmask), rv->net))
			return rv;
	}
	return NULL;
}

struct subnet *
find_grouped_subnet(struct shared_network *share, struct iaddr addr)
{
	struct subnet *rv;

	for (rv = share->subnets; rv; rv = rv->next_sibling) {
		if (addr_eq(subnet_number(addr, rv->netmask), rv->net))
			return rv;
	}
	return NULL;
}

int
subnet_inner_than(struct subnet *subnet, struct subnet *scan, int warnp)
{
	if (addr_eq(subnet_number(subnet->net, scan->netmask), scan->net) ||
	    addr_eq(subnet_number(scan->net, subnet->netmask), subnet->net)) {
		char n1buf[16];
		int i, j;

		for (i = 0; i < 32; i++)
			if (subnet->netmask.iabuf[3 - (i >> 3)] &
			    (1 << (i & 7)))
				break;
		for (j = 0; j < 32; j++)
			if (scan->netmask.iabuf[3 - (j >> 3)] &
			    (1 << (j & 7)))
				break;
		strlcpy(n1buf, piaddr(subnet->net), sizeof(n1buf));
		if (warnp)
			log_warnx("%ssubnet %s/%d conflicts with subnet %s/%d",
			    "Warning: ", n1buf, 32 - i,
			    piaddr(scan->net), 32 - j);
		if (i < j)
			return 1;
	}
	return 0;
}

/* Enter a new subnet into the subnet list. */
void
enter_subnet(struct subnet *subnet)
{
	struct subnet *scan, *prev = NULL;

	/* Check for duplicates... */
	for (scan = subnets; scan; scan = scan->next_subnet) {
		/*
		 * When we find a conflict, make sure that the
		 * subnet with the narrowest subnet mask comes
		 * first.
		 */
		if (subnet_inner_than(subnet, scan, 1)) {
			if (prev) {
				prev->next_subnet = subnet;
			} else
				subnets = subnet;
			subnet->next_subnet = scan;
			return;
		}
		prev = scan;
	}

	/* XXX use the BSD radix tree code instead of a linked list. */
	subnet->next_subnet = subnets;
	subnets = subnet;
}

/* Enter a new shared network into the shared network list. */
void
enter_shared_network(struct shared_network *share)
{
	/* XXX Sort the nets into a balanced tree to make searching quicker. */
	share->next = shared_networks;
	shared_networks = share;
}

/*
 * Enter a lease into the system.   This is called by the parser each
 * time it reads in a new lease.   If the subnet for that lease has
 * already been read in (usually the case), just update that lease;
 * otherwise, allocate temporary storage for the lease and keep it around
 * until we're done reading in the config file.
 */
void
enter_lease(struct lease *lease)
{
	struct lease *comp = find_lease_by_ip_addr(lease->ip_addr);

	/* If we don't have a place for this lease yet, save it for later. */
	if (!comp) {
		comp = calloc(1, sizeof(struct lease));
		if (!comp)
			fatalx("No memory for lease %s\n",
			    piaddr(lease->ip_addr));
		*comp = *lease;
		comp->next = dangling_leases;
		comp->prev = NULL;
		dangling_leases = comp;
	} else {
		/* Record the hostname information in the lease. */
		comp->hostname = lease->hostname;
		comp->client_hostname = lease->client_hostname;
		supersede_lease(comp, lease, 0);
	}
}

static inline int
hwaddrcmp(struct hardware *a, struct hardware *b)
{
	return ((a->htype != b->htype) || (a->hlen != b->hlen) ||
	    memcmp(a->haddr, b->haddr, b->hlen));
}

static inline int
uidcmp(struct lease *a, struct lease *b)
{
	return (a->uid_len != b->uid_len || memcmp(a->uid, b->uid,
	    b->uid_len));
}

static inline int
uid_or_hwaddr_cmp(struct lease *a, struct lease *b)
{
	if (a->uid && b->uid)
		return uidcmp(a, b);
	return hwaddrcmp(&a->hardware_addr, &b->hardware_addr);
}

/*
 * Replace the data in an existing lease with the data in a new lease;
 * adjust hash tables to suit, and insertion sort the lease into the
 * list of leases by expiry time so that we can always find the oldest
 * lease.
 */
int
supersede_lease(struct lease *comp, struct lease *lease, int commit)
{
	int enter_uid = 0;
	int enter_hwaddr = 0;
	int do_pftable = 0;
	struct lease *lp;

	/* Static leases are not currently kept in the database... */
	if (lease->flags & STATIC_LEASE)
		return 1;

	/*
	 * If the existing lease hasn't expired and has a different
	 * unique identifier or, if it doesn't have a unique
	 * identifier, a different hardware address, then the two
	 * leases are in conflict.  If the existing lease has a uid
	 * and the new one doesn't, but they both have the same
	 * hardware address, and dynamic bootp is allowed on this
	 * lease, then we allow that, in case a dynamic BOOTP lease is
	 * requested *after* a DHCP lease has been assigned.
	 */
	if (!(lease->flags & ABANDONED_LEASE) &&
	    comp->ends > cur_time && uid_or_hwaddr_cmp(comp, lease)) {
		log_warnx("Lease conflict at %s", piaddr(comp->ip_addr));
		return 0;
	} else {
		/* If there's a Unique ID, dissociate it from the hash
		   table and free it if necessary. */
		if (comp->uid) {
			uid_hash_delete(comp);
			enter_uid = 1;
			if (comp->uid != &comp->uid_buf[0]) {
				if (comp->uid != lease->uid)
					free(comp->uid);
				comp->uid_max = 0;
				comp->uid_len = 0;
			}
			comp->uid = NULL;
		} else
			enter_uid = 1;

		if (comp->hardware_addr.htype &&
		    hwaddrcmp(&comp->hardware_addr, &lease->hardware_addr)) {
			hw_hash_delete(comp);
			enter_hwaddr = 1;
			do_pftable = 1;
		} else if (!comp->hardware_addr.htype) {
			enter_hwaddr = 1;
			do_pftable = 1;
		}

		/* Copy the data files, but not the linkages. */
		comp->starts = lease->starts;
		if (lease->uid) {
			if (lease->uid_len <= sizeof (lease->uid_buf)) {
				memcpy(comp->uid_buf, lease->uid,
				    lease->uid_len);
				comp->uid = &comp->uid_buf[0];
				comp->uid_max = sizeof comp->uid_buf;
			} else if (lease->uid != &lease->uid_buf[0]) {
				comp->uid = lease->uid;
				comp->uid_max = lease->uid_max;
				lease->uid = NULL;
				lease->uid_max = 0;
			} else {
				fatalx("corrupt lease uid."); /* XXX */
			}
		} else {
			comp->uid = NULL;
			comp->uid_max = 0;
		}
		comp->uid_len = lease->uid_len;
		comp->host = lease->host;
		comp->hardware_addr = lease->hardware_addr;
		comp->flags = ((lease->flags & ~PERSISTENT_FLAGS) |
		    (comp->flags & ~EPHEMERAL_FLAGS));

		/* Record the lease in the uid hash if necessary. */
		if (enter_uid && lease->uid)
			uid_hash_add(comp);

		/* Record it in the hardware address hash if necessary. */
		if (enter_hwaddr && lease->hardware_addr.htype)
			hw_hash_add(comp);

		/* Remove the lease from its current place in the
		   timeout sequence. */
		if (comp->prev)
			comp->prev->next = comp->next;
		else
			comp->shared_network->leases = comp->next;
		if (comp->next)
			comp->next->prev = comp->prev;
		if (comp->shared_network->last_lease == comp)
			comp->shared_network->last_lease = comp->prev;

		/* Find the last insertion point... */
		if (comp == comp->shared_network->insertion_point ||
		    !comp->shared_network->insertion_point)
			lp = comp->shared_network->leases;
		else
			lp = comp->shared_network->insertion_point;

		if (!lp) {
			/* Nothing on the list yet?    Just make comp the
			   head of the list. */
			comp->shared_network->leases = comp;
			comp->shared_network->last_lease = comp;
		} else if (lp->ends > lease->ends) {
			/* Skip down the list until we run out of list
			   or find a place for comp. */
			while (lp->next && lp->ends > lease->ends) {
				lp = lp->next;
			}
			if (lp->ends > lease->ends) {
				/* If we ran out of list, put comp
				   at the end. */
				lp->next = comp;
				comp->prev = lp;
				comp->next = NULL;
				comp->shared_network->last_lease = comp;
			} else {
				/* If we didn't, put it between lp and
				   the previous item on the list. */
				if ((comp->prev = lp->prev))
					comp->prev->next = comp;
				comp->next = lp;
				lp->prev = comp;
			}
		} else {
			/* Skip up the list until we run out of list
			   or find a place for comp. */
			while (lp->prev && lp->ends < lease->ends) {
				lp = lp->prev;
			}
			if (lp->ends < lease->ends) {
				/* If we ran out of list, put comp
				   at the beginning. */
				lp->prev = comp;
				comp->next = lp;
				comp->prev = NULL;
				comp->shared_network->leases = comp;
			} else {
				/* If we didn't, put it between lp and
				   the next item on the list. */
				if ((comp->next = lp->next))
					comp->next->prev = comp;
				comp->prev = lp;
				lp->next = comp;
			}
		}
		comp->shared_network->insertion_point = comp;
		comp->ends = lease->ends;
	}

	pfmsg('L', lease); /* address is leased. remove from purgatory */
	if (do_pftable) /* address changed hwaddr. remove from overload */
		pfmsg('C', lease);

	/* Return zero if we didn't commit the lease to permanent storage;
	   nonzero if we did. */
	return commit && write_lease(comp) && commit_leases();
}

/* Release the specified lease and re-hash it as appropriate. */

void
release_lease(struct lease *lease)
{
	struct lease lt;

	lt = *lease;
	if (lt.ends > cur_time) {
		lt.ends = cur_time;
		supersede_lease(lease, &lt, 1);
		log_info("Released lease for IP address %s",
		    piaddr(lease->ip_addr));
		pfmsg('R', lease);
	}
}


/*
 * Abandon the specified lease for the specified time. sets its
 * particulars to zero, the end time appropriately and re-hash it as
 * appropriate. abandons permanently if abtime is 0
 */
void
abandon_lease(struct lease *lease, char *message)
{
	struct lease lt;
	time_t abtime;

	abtime = lease->subnet->group->default_lease_time;
	lease->flags |= ABANDONED_LEASE;
	lt = *lease;
	lt.ends = cur_time + abtime;
	log_warnx("Abandoning IP address %s for %lld seconds: %s",
	    piaddr(lease->ip_addr), (long long)abtime, message);
	lt.hardware_addr.htype = 0;
	lt.hardware_addr.hlen = 0;
	lt.uid = NULL;
	lt.uid_len = 0;
	supersede_lease(lease, &lt, 1);

	pfmsg('A', lease); /* address is abandoned. send to purgatory */
	return;
}

/* Locate the lease associated with a given IP address... */
struct lease *
find_lease_by_ip_addr(struct iaddr addr)
{
	return (struct lease *)hash_lookup(lease_ip_addr_hash,
	    addr.iabuf, addr.len);
}

struct lease *
find_lease_by_uid(unsigned char *uid, int len)
{
	return (struct lease *)hash_lookup(lease_uid_hash, uid, len);
}

struct lease *
find_lease_by_hw_addr(unsigned char *hwaddr, int hwlen)
{
	return (struct lease *)hash_lookup(lease_hw_addr_hash, hwaddr, hwlen);
}

/* Add the specified lease to the uid hash. */
void
uid_hash_add(struct lease *lease)
{
	struct lease *head = find_lease_by_uid(lease->uid, lease->uid_len);
	struct lease *scan;

	/* If it's not in the hash, just add it. */
	if (!head)
		add_hash(lease_uid_hash, lease->uid,
		    lease->uid_len, (unsigned char *)lease);
	else {
		/* Otherwise, attach it to the end of the list. */
		for (scan = head; scan->n_uid; scan = scan->n_uid)
			;
		scan->n_uid = lease;
	}
}

/* Delete the specified lease from the uid hash. */
void
uid_hash_delete(struct lease *lease)
{
	struct lease *head = find_lease_by_uid(lease->uid, lease->uid_len);
	struct lease *scan;

	/* If it's not in the hash, we have no work to do. */
	if (!head) {
		lease->n_uid = NULL;
		return;
	}

	/* If the lease we're freeing is at the head of the list,
	   remove the hash table entry and add a new one with the
	   next lease on the list (if there is one). */
	if (head == lease) {
		delete_hash_entry(lease_uid_hash, lease->uid, lease->uid_len);
		if (lease->n_uid)
			add_hash(lease_uid_hash, lease->n_uid->uid,
			    lease->n_uid->uid_len,
			    (unsigned char *)(lease->n_uid));
	} else {
		/* Otherwise, look for the lease in the list of leases
		   attached to the hash table entry, and remove it if
		   we find it. */
		for (scan = head; scan->n_uid; scan = scan->n_uid) {
			if (scan->n_uid == lease) {
				scan->n_uid = scan->n_uid->n_uid;
				break;
			}
		}
	}
	lease->n_uid = NULL;
}

/* Add the specified lease to the hardware address hash. */
void
hw_hash_add(struct lease *lease)
{
	struct lease *head = find_lease_by_hw_addr(lease->hardware_addr.haddr,
	    lease->hardware_addr.hlen);
	struct lease *scan;

	/* If it's not in the hash, just add it. */
	if (!head)
		add_hash(lease_hw_addr_hash, lease->hardware_addr.haddr,
		    lease->hardware_addr.hlen, (unsigned char *)lease);
	else {
		/* Otherwise, attach it to the end of the list. */
		for (scan = head; scan->n_hw; scan = scan->n_hw)
			;
		scan->n_hw = lease;
	}
}

/* Delete the specified lease from the hardware address hash. */
void
hw_hash_delete(struct lease *lease)
{
	struct lease *head = find_lease_by_hw_addr(lease->hardware_addr.haddr,
	    lease->hardware_addr.hlen);
	struct lease *scan;

	/* If it's not in the hash, we have no work to do. */
	if (!head) {
		lease->n_hw = NULL;
		return;
	}

	/* If the lease we're freeing is at the head of the list,
	   remove the hash table entry and add a new one with the
	   next lease on the list (if there is one). */
	if (head == lease) {
		delete_hash_entry(lease_hw_addr_hash,
		    lease->hardware_addr.haddr, lease->hardware_addr.hlen);
		if (lease->n_hw)
			add_hash(lease_hw_addr_hash,
			    lease->n_hw->hardware_addr.haddr,
			    lease->n_hw->hardware_addr.hlen,
			    (unsigned char *)(lease->n_hw));
	} else {
		/*
		 * Otherwise, look for the lease in the list of leases
		 * attached to the hash table entry, and remove it if
		 * we find it.
		 */
		for (scan = head; scan->n_hw; scan = scan->n_hw) {
			if (scan->n_hw == lease) {
				scan->n_hw = scan->n_hw->n_hw;
				break;
			}
		}
	}
	lease->n_hw = NULL;
}


struct class *
add_class(int type, char *name)
{
	struct class *class;
	char *tname;

	class = calloc(1, sizeof(*class));
	tname = strdup(name);

	if (!vendor_class_hash)
		vendor_class_hash = new_hash();
	if (!user_class_hash)
		user_class_hash = new_hash();

	if (!tname || !class || !vendor_class_hash || !user_class_hash) {
		log_warnx("No memory for %s.", name);
		free(class);
		free(tname);
		return NULL;
	}

	class->name = tname;

	if (type)
		add_hash(user_class_hash, (unsigned char *)tname,
		    strlen(tname), (unsigned char *)class);
	else
		add_hash(vendor_class_hash, (unsigned char *)tname,
		    strlen(tname), (unsigned char *)class);

	return class;
}

struct class *
find_class(int type, unsigned char *name, int len)
{
	return (struct class *)hash_lookup(type ? user_class_hash :
	    vendor_class_hash, name, len);
}

struct group *
clone_group(struct group *group, char *caller)
{
	struct group *g;

	g = calloc(1, sizeof(struct group));
	if (!g)
		fatalx("%s: can't allocate new group", caller);
	*g = *group;
	return g;
}

/* Write all interesting leases to permanent storage. */

void
write_leases(void)
{
	struct lease *l;
	struct shared_network *s;

	for (s = shared_networks; s; s = s->next) {
		for (l = s->leases; l; l = l->next) {
			if (l->hardware_addr.hlen || l->uid_len ||
			    (l->flags & ABANDONED_LEASE)) {
				if (!write_lease(l))
					fatalx("Can't rewrite lease database");
				if (syncsend)
					sync_lease(l);
			}
		}
	}
	if (!commit_leases())
		fatal("Can't commit leases to new database");
}