/* 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 dyn_lease *oldest_expired_lease(void) { struct dyn_lease *oldest_lease = NULL; leasetime_t oldest_time = time(NULL); unsigned i; /* Unexpired leases have g_leases[i].expires >= current time * and therefore can't ever match */ for (i = 0; i < server_config.max_leases; i++) { if (g_leases[i].expires < oldest_time) { oldest_time = g_leases[i].expires; oldest_lease = &g_leases[i]; } } return oldest_lease; } /* Clear out all leases with matching nonzero chaddr OR yiaddr. * If chaddr == NULL, this is a conflict lease. */ static void clear_leases(const uint8_t *chaddr, uint32_t yiaddr) { unsigned i; for (i = 0; i < server_config.max_leases; i++) { if ((chaddr && memcmp(g_leases[i].lease_mac, chaddr, 6) == 0) || (yiaddr && g_leases[i].lease_nip == yiaddr) ) { memset(&g_leases[i], 0, sizeof(g_leases[i])); } } } /* Add a lease into the table, clearing out any old ones * If chaddr == NULL, this is a conflict lease. */ struct dyn_lease* FAST_FUNC add_lease( const uint8_t *chaddr, uint32_t yiaddr, leasetime_t leasetime, const char *hostname, int hostname_len) { struct dyn_lease *oldest; /* clean out any old ones */ clear_leases(chaddr, yiaddr); oldest = oldest_expired_lease(); if (oldest) { memset(oldest, 0, sizeof(*oldest)); if (hostname) { char *p; if (hostname_len > sizeof(oldest->hostname)) hostname_len = sizeof(oldest->hostname); p = safe_strncpy(oldest->hostname, hostname, hostname_len); /* sanitization (s/non-ASCII/^/g) */ while (*p) { if (*p < ' ' || *p > 126) *p = '^'; p++; } } if (chaddr) memcpy(oldest->lease_mac, chaddr, 6); oldest->lease_nip = yiaddr; oldest->expires = time(NULL) + leasetime; } return oldest; } /* True if a lease has expired */ int FAST_FUNC is_expired_lease(struct dyn_lease *lease) { return (lease->expires < (leasetime_t) time(NULL)); } /* Find the first lease that matches MAC, NULL if no match */ struct dyn_lease* FAST_FUNC find_lease_by_mac(const uint8_t *mac) { unsigned i; for (i = 0; i < server_config.max_leases; i++) if (memcmp(g_leases[i].lease_mac, mac, 6) == 0) return &g_leases[i]; return NULL; } /* Find the first lease that matches IP, NULL is no match */ struct dyn_lease* FAST_FUNC find_lease_by_nip(uint32_t nip) { unsigned i; for (i = 0; i < server_config.max_leases; i++) if (g_leases[i].lease_nip == nip) return &g_leases[i]; return NULL; } /* Check if the IP is taken; if it is, add it to the lease table */ static int nobody_responds_to_arp(uint32_t nip, const uint8_t *safe_mac) { struct in_addr temp; int r; r = arpping(nip, safe_mac, server_config.server_nip, server_config.server_mac, server_config.interface); if (r) return r; temp.s_addr = nip; bb_info_msg("%s belongs to someone, reserving it for %u seconds", inet_ntoa(temp), (unsigned)server_config.conflict_time); add_lease(NULL, nip, server_config.conflict_time, NULL, 0); return 0; } /* Find a new usable (we think) address */ uint32_t FAST_FUNC find_free_or_expired_nip(const uint8_t *safe_mac) { uint32_t addr; struct dyn_lease *oldest_lease = NULL; addr = server_config.start_ip; /* addr is in host order here */ for (; addr <= server_config.end_ip; addr++) { uint32_t nip; struct dyn_lease *lease; /* ie, 192.168.55.0 */ if ((addr & 0xff) == 0) continue; /* ie, 192.168.55.255 */ if ((addr & 0xff) == 0xff) continue; nip = htonl(addr); /* is this a static lease addr? */ if (is_nip_reserved(server_config.static_leases, nip)) continue; lease = find_lease_by_nip(nip); if (!lease) { //TODO: DHCP servers do not always sit on the same subnet as clients: should *ping*, not arp-ping! if (nobody_responds_to_arp(nip, safe_mac)) return nip; } else { if (!oldest_lease || lease->expires < oldest_lease->expires) oldest_lease = lease; } } if (oldest_lease && is_expired_lease(oldest_lease) && nobody_responds_to_arp(oldest_lease->lease_nip, safe_mac) ) { return oldest_lease->lease_nip; } return 0; }