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