1/* 2 * leases.c -- tools to manage DHCP leases 3 * Russ Dill <Russ.Dill@asu.edu> July 2001 4 */ 5 6#include <time.h> 7#include <string.h> 8#include <sys/socket.h> 9#include <netinet/in.h> 10#include <arpa/inet.h> 11 12#include "debug.h" 13#include "dhcpd.h" 14#include "files.h" 15#include "options.h" 16#include "leases.h" 17#include "arpping.h" 18 19unsigned char blank_chaddr[] = {[0 ... 15] = 0}; 20 21/* clear every lease out that chaddr OR yiaddr matches and is nonzero */ 22void clear_lease(u_int8_t *chaddr, u_int32_t yiaddr) 23{ 24 unsigned int i, j; 25 26 for (j = 0; j < 16 && !chaddr[j]; j++); 27 28 for (i = 0; i < server_config.max_leases; i++) 29 if ((j != 16 && !memcmp(leases[i].chaddr, chaddr, 16)) || 30 (yiaddr && leases[i].yiaddr == yiaddr)) { 31 memset(&(leases[i]), 0, sizeof(struct dhcpOfferedAddr)); 32 } 33} 34 35 36/* add a lease into the table, clearing out any old ones */ 37struct dhcpOfferedAddr *add_lease(u_int8_t *chaddr, u_int32_t yiaddr, unsigned long lease) 38{ 39 struct dhcpOfferedAddr *oldest; 40 41 /* clean out any old ones */ 42 clear_lease(chaddr, yiaddr); 43 44 oldest = oldest_expired_lease(); 45 46 if (oldest) { 47 memcpy(oldest->chaddr, chaddr, 16); 48 oldest->yiaddr = yiaddr; 49 oldest->expires = time(0) + lease; 50 } 51 52 return oldest; 53} 54 55 56/* true if a lease has expired */ 57int lease_expired(struct dhcpOfferedAddr *lease) 58{ 59 return (lease->expires < (unsigned long) time(0)); 60} 61 62 63/* Find the oldest expired lease, NULL if there are no expired leases */ 64struct dhcpOfferedAddr *oldest_expired_lease(void) 65{ 66 struct dhcpOfferedAddr *oldest = NULL; 67 unsigned long oldest_lease = time(0); 68 unsigned int i; 69 70 71 for (i = 0; i < server_config.max_leases; i++) 72 if (oldest_lease > leases[i].expires) { 73 oldest_lease = leases[i].expires; 74 oldest = &(leases[i]); 75 } 76 return oldest; 77 78} 79 80 81/* Find the first lease that matches chaddr, NULL if no match */ 82struct dhcpOfferedAddr *find_lease_by_chaddr(u_int8_t *chaddr) 83{ 84 unsigned int i; 85 86 for (i = 0; i < server_config.max_leases; i++) 87 if (!memcmp(leases[i].chaddr, chaddr, 16)) return &(leases[i]); 88 89 return NULL; 90} 91 92 93/* Find the first lease that matches yiaddr, NULL is no match */ 94struct dhcpOfferedAddr *find_lease_by_yiaddr(u_int32_t yiaddr) 95{ 96 unsigned int i; 97 98 for (i = 0; i < server_config.max_leases; i++) 99 if (leases[i].yiaddr == yiaddr) return &(leases[i]); 100 101 return NULL; 102} 103 104 105/* find an assignable address, it check_expired is true, we check all the expired leases as well. 106 * Maybe this should try expired leases by age... */ 107u_int32_t find_address(int check_expired) 108{ 109 u_int32_t addr, ret; 110 struct dhcpOfferedAddr *lease = NULL; 111 112 addr = ntohl(server_config.start); /* addr is in host order here */ 113 for (;addr <= ntohl(server_config.end); addr++) { 114 115 /* ie, 192.168.55.0 */ 116 if (!(addr & 0xFF)) continue; 117 118 /* ie, 192.168.55.255 */ 119 if ((addr & 0xFF) == 0xFF) continue; 120 121 /* lease is not taken */ 122 ret = htonl(addr); 123 if ((!(lease = find_lease_by_yiaddr(ret)) || 124 125 /* or it expired and we are checking for expired leases */ 126 (check_expired && lease_expired(lease))) && 127 128 /* and it isn't on the network */ 129 !check_ip(ret)) { 130 return ret; 131 break; 132 } 133 } 134 return 0; 135} 136 137 138/* check is an IP is taken, if it is, add it to the lease table */ 139int check_ip(u_int32_t addr) 140{ 141 struct in_addr temp; 142 143 if (arpping(addr, server_config.server, server_config.arp, server_config.interface) == 0) { 144 temp.s_addr = addr; 145 LOG(LOG_INFO, "%s belongs to someone, reserving it for %ld seconds", 146 inet_ntoa(temp), server_config.conflict_time); 147 add_lease(blank_chaddr, addr, server_config.conflict_time); 148 return 1; 149 } else return 0; 150} 151