152 lines
3.7 KiB
C
152 lines
3.7 KiB
C
/* vi: set sw=4 ts=4: */
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/*
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* leases.c -- tools to manage DHCP leases
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* Russ Dill <Russ.Dill@asu.edu> July 2001
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*
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* Licensed under GPLv2, see file LICENSE in this tarball for details.
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*/
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#include "common.h"
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#include "dhcpd.h"
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/* Find the oldest expired lease, NULL if there are no expired leases */
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static struct dhcpOfferedAddr *oldest_expired_lease(void)
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{
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struct dhcpOfferedAddr *oldest = NULL;
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// TODO: use monotonic_sec()
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unsigned long oldest_lease = time(0);
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unsigned i;
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for (i = 0; i < server_config.max_leases; i++)
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if (oldest_lease > leases[i].expires) {
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oldest_lease = leases[i].expires;
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oldest = &(leases[i]);
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}
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return oldest;
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}
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/* clear every lease out that chaddr OR yiaddr matches and is nonzero */
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static void clear_lease(const uint8_t *chaddr, uint32_t yiaddr)
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{
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unsigned i, j;
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for (j = 0; j < 16 && !chaddr[j]; j++)
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continue;
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for (i = 0; i < server_config.max_leases; i++)
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if ((j != 16 && memcmp(leases[i].chaddr, chaddr, 16) == 0)
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|| (yiaddr && leases[i].yiaddr == yiaddr)
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) {
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memset(&(leases[i]), 0, sizeof(leases[i]));
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}
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}
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/* add a lease into the table, clearing out any old ones */
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struct dhcpOfferedAddr* FAST_FUNC add_lease(const uint8_t *chaddr, uint32_t yiaddr, unsigned long lease)
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{
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struct dhcpOfferedAddr *oldest;
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/* clean out any old ones */
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clear_lease(chaddr, yiaddr);
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oldest = oldest_expired_lease();
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if (oldest) {
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memcpy(oldest->chaddr, chaddr, 16);
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oldest->yiaddr = yiaddr;
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oldest->expires = time(0) + lease;
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}
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return oldest;
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}
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/* true if a lease has expired */
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int FAST_FUNC lease_expired(struct dhcpOfferedAddr *lease)
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{
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return (lease->expires < (unsigned long) time(0));
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}
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/* Find the first lease that matches chaddr, NULL if no match */
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struct dhcpOfferedAddr* FAST_FUNC find_lease_by_chaddr(const uint8_t *chaddr)
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{
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unsigned i;
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for (i = 0; i < server_config.max_leases; i++)
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if (!memcmp(leases[i].chaddr, chaddr, 16))
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return &(leases[i]);
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return NULL;
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}
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/* Find the first lease that matches yiaddr, NULL is no match */
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struct dhcpOfferedAddr* FAST_FUNC find_lease_by_yiaddr(uint32_t yiaddr)
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{
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unsigned i;
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for (i = 0; i < server_config.max_leases; i++)
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if (leases[i].yiaddr == yiaddr)
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return &(leases[i]);
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return NULL;
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}
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/* check is an IP is taken, if it is, add it to the lease table */
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static int nobody_responds_to_arp(uint32_t addr)
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{
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/* 16 zero bytes */
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static const uint8_t blank_chaddr[16] = { 0 };
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/* = { 0 } helps gcc to put it in rodata, not bss */
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struct in_addr temp;
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int r;
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r = arpping(addr, server_config.server, server_config.arp, server_config.interface);
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if (r)
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return r;
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temp.s_addr = addr;
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bb_info_msg("%s belongs to someone, reserving it for %u seconds",
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inet_ntoa(temp), (unsigned)server_config.conflict_time);
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add_lease(blank_chaddr, addr, server_config.conflict_time);
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return 0;
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}
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/* find an assignable address, if check_expired is true, we check all the expired leases as well.
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* Maybe this should try expired leases by age... */
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uint32_t FAST_FUNC find_address(int check_expired)
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{
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uint32_t addr, ret;
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struct dhcpOfferedAddr *lease = NULL;
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addr = server_config.start_ip; /* addr is in host order here */
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for (; addr <= server_config.end_ip; addr++) {
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/* ie, 192.168.55.0 */
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if (!(addr & 0xFF))
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continue;
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/* ie, 192.168.55.255 */
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if ((addr & 0xFF) == 0xFF)
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continue;
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/* Only do if it isn't assigned as a static lease */
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ret = htonl(addr);
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if (!reservedIp(server_config.static_leases, ret)) {
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/* lease is not taken */
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lease = find_lease_by_yiaddr(ret);
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/* no lease or it expired and we are checking for expired leases */
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if ((!lease || (check_expired && lease_expired(lease)))
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&& nobody_responds_to_arp(ret) /* it isn't used on the network */
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) {
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return ret;
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}
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}
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}
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return 0;
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}
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