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/*
* leases.c -- tools to manage DHCP leases
* Russ Dill <Russ.Dill@asu.edu> July 2001
*/
#include <time.h>
#include <string.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include "dhcpd.h"
#include "files.h"
#include "options.h"
#include "leases.h"
#include "arpping.h"
#include "common.h"
uint8_t blank_chaddr[] = {[0 ... 15] = 0};
/* clear every lease out that chaddr OR yiaddr matches and is nonzero */
void clear_lease(uint8_t *chaddr, uint32_t yiaddr)
{
unsigned int i, j;
for (j = 0; j < 16 && !chaddr[j]; j++);
for (i = 0; i < server_config.max_leases; i++)
if ((j != 16 && !memcmp(leases[i].chaddr, chaddr, 16)) ||
(yiaddr && leases[i].yiaddr == yiaddr)) {
memset(&(leases[i]), 0, sizeof(struct dhcpOfferedAddr));
}
}
/* add a lease into the table, clearing out any old ones */
struct dhcpOfferedAddr *add_lease(uint8_t *chaddr, uint32_t yiaddr, unsigned long lease)
{
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(0) + lease;
}
return oldest;
}
/* true if a lease has expired */
int lease_expired(struct dhcpOfferedAddr *lease)
{
return (lease->expires < (unsigned long) time(0));
}
/* Find the oldest expired lease, NULL if there are no expired leases */
struct dhcpOfferedAddr *oldest_expired_lease(void)
{
struct dhcpOfferedAddr *oldest = NULL;
unsigned long oldest_lease = time(0);
unsigned int i;
for (i = 0; i < server_config.max_leases; i++)
if (oldest_lease > leases[i].expires) {
oldest_lease = leases[i].expires;
oldest = &(leases[i]);
}
return oldest;
}
/* Find the first lease that matches chaddr, NULL if no match */
struct dhcpOfferedAddr *find_lease_by_chaddr(uint8_t *chaddr)
{
unsigned int 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 *find_lease_by_yiaddr(uint32_t yiaddr)
{
unsigned int 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 check_ip(uint32_t addr)
{
struct in_addr temp;
if (arpping(addr, server_config.server, server_config.arp, server_config.interface) == 0) {
temp.s_addr = addr;
LOG(LOG_INFO, "%s belongs to someone, reserving it for %ld seconds",
inet_ntoa(temp), server_config.conflict_time);
add_lease(blank_chaddr, addr, server_config.conflict_time);
return 1;
} else return 0;
}
/* find an assignable address, it check_expired is true, we check all the expired leases as well.
* Maybe this should try expired leases by age... */
uint32_t find_address(int check_expired)
{
uint32_t addr, ret;
struct dhcpOfferedAddr *lease = NULL;
addr = ntohl(server_config.start); /* addr is in host order here */
for (;addr <= ntohl(server_config.end); addr++) {
/* ie, 192.168.55.0 */
if (!(addr & 0xFF)) continue;
/* ie, 192.168.55.255 */
if ((addr & 0xFF) == 0xFF) continue;
/* lease is not taken */
ret = htonl(addr);
if ((!(lease = find_lease_by_yiaddr(ret)) ||
/* or it expired and we are checking for expired leases */
(check_expired && lease_expired(lease))) &&
/* and it isn't on the network */
!check_ip(ret)) {
return ret;
break;
}
}
return 0;
}
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