/* vi: set sw=4 ts=4: */ /* * leases.c -- tools to manage DHCP leases * Russ Dill 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; }