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/* vi: set sw=4 ts=4: */
/*
* leases.c -- tools to manage DHCP leases
* Russ Dill <Russ.Dill@asu.edu> July 2001
*
* Licensed under GPLv2, see file LICENSE in this tarball for details.
*/
#include "common.h"
#include "dhcpd.h"
/* Find the oldest expired lease, NULL if there are no expired leases */
static struct dhcpOfferedAddr *oldest_expired_lease(void)
{
struct dhcpOfferedAddr *oldest_lease = NULL;
leasetime_t oldest_time = time(NULL);
unsigned i;
/* Unexpired leases have leases[i].expires >= current time
* and therefore can't ever match */
for (i = 0; i < server_config.max_leases; i++) {
if (leases[i].expires < oldest_time) {
oldest_time = leases[i].expires;
oldest_lease = &(leases[i]);
}
}
return oldest_lease;
}
/* Clear every lease out that chaddr OR yiaddr matches and is nonzero */
static void clear_lease(const uint8_t *chaddr, uint32_t yiaddr)
{
unsigned i, j;
for (j = 0; j < 16 && !chaddr[j]; j++)
continue;
for (i = 0; i < server_config.max_leases; i++) {
if ((j != 16 && memcmp(leases[i].chaddr, chaddr, 16) == 0)
|| (yiaddr && leases[i].yiaddr == yiaddr)
) {
memset(&(leases[i]), 0, sizeof(leases[i]));
}
}
}
/* Add a lease into the table, clearing out any old ones */
struct dhcpOfferedAddr* FAST_FUNC add_lease(const uint8_t *chaddr, uint32_t yiaddr, leasetime_t leasetime)
{
struct dhcpOfferedAddr *oldest;
/* clean out any old ones */
clear_lease(chaddr, yiaddr);
oldest = oldest_expired_lease();
if (oldest) {
memcpy(oldest->chaddr, chaddr, 16);
oldest->yiaddr = yiaddr;
oldest->expires = time(NULL) + leasetime;
}
return oldest;
}
/* True if a lease has expired */
int FAST_FUNC lease_expired(struct dhcpOfferedAddr *lease)
{
return (lease->expires < (leasetime_t) time(NULL));
}
/* Find the first lease that matches chaddr, NULL if no match */
struct dhcpOfferedAddr* FAST_FUNC find_lease_by_chaddr(const uint8_t *chaddr)
{
unsigned i;
for (i = 0; i < server_config.max_leases; i++)
if (!memcmp(leases[i].chaddr, chaddr, 16))
return &(leases[i]);
return NULL;
}
/* Find the first lease that matches yiaddr, NULL is no match */
struct dhcpOfferedAddr* FAST_FUNC find_lease_by_yiaddr(uint32_t yiaddr)
{
unsigned i;
for (i = 0; i < server_config.max_leases; i++)
if (leases[i].yiaddr == yiaddr)
return &(leases[i]);
return NULL;
}
/* check is an IP is taken, if it is, add it to the lease table */
static int nobody_responds_to_arp(uint32_t addr)
{
/* 16 zero bytes */
static const uint8_t blank_chaddr[16] = { 0 };
/* = { 0 } helps gcc to put it in rodata, not bss */
struct in_addr temp;
int r;
r = arpping(addr, server_config.server, server_config.arp, server_config.interface);
if (r)
return r;
temp.s_addr = addr;
bb_info_msg("%s belongs to someone, reserving it for %u seconds",
inet_ntoa(temp), (unsigned)server_config.conflict_time);
add_lease(blank_chaddr, addr, server_config.conflict_time);
return 0;
}
/* Find a new usable (we think) address. */
uint32_t FAST_FUNC find_free_or_expired_address(void)
{
uint32_t addr;
struct dhcpOfferedAddr *oldest_lease = NULL;
addr = server_config.start_ip; /* addr is in host order here */
for (; addr <= server_config.end_ip; addr++) {
uint32_t net_addr;
struct dhcpOfferedAddr *lease;
/* ie, 192.168.55.0 */
if ((addr & 0xff) == 0)
continue;
/* ie, 192.168.55.255 */
if ((addr & 0xff) == 0xff)
continue;
net_addr = htonl(addr);
/* addr has a static lease? */
if (reservedIp(server_config.static_leases, net_addr))
continue;
lease = find_lease_by_yiaddr(net_addr);
if (!lease) {
if (nobody_responds_to_arp(net_addr))
return net_addr;
} else {
if (!oldest_lease || lease->expires < oldest_lease->expires)
oldest_lease = lease;
}
}
if (oldest_lease && lease_expired(oldest_lease)
&& nobody_responds_to_arp(oldest_lease->yiaddr)
) {
return oldest_lease->yiaddr;
}
return 0;
}
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