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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
*/
#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 = NULL;
// TODO: use monotonic_sec()
unsigned long oldest_lease = time(0);
unsigned 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;
}
/* 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 *add_lease(const 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 first lease that matches chaddr, NULL if no match */
struct dhcpOfferedAddr *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 *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)
{
static const uint8_t blank_chaddr[16]; /* 16 zero bytes */
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 an assignable address, if 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 = server_config.start_ip; /* addr is in host order here */
for (; addr <= server_config.end_ip; addr++) {
/* ie, 192.168.55.0 */
if (!(addr & 0xFF))
continue;
/* ie, 192.168.55.255 */
if ((addr & 0xFF) == 0xFF)
continue;
/* Only do if it isn't assigned as a static lease */
ret = htonl(addr);
if (!reservedIp(server_config.static_leases, ret)) {
/* lease is not taken */
lease = find_lease_by_yiaddr(ret);
/* no lease or it expired and we are checking for expired leases */
if ((!lease || (check_expired && lease_expired(lease)))
&& nobody_responds_to_arp(ret) /* it isn't used on the network */
) {
return ret;
}
}
}
return 0;
}
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