/* * leases.c -- tools to manage DHCP leases * Russ Dill <Russ.Dill@asu.edu> July 2001 */#include <time.h>#include <string.h>#include <sys/socket.h>#include <netinet/in.h>#include <arpa/inet.h>#include "dhcpd.h"#include "files.h"#include "options.h"#include "leases.h"#include "arpping.h"#include "common.h"#include "static_leases.h"uint8_t blank_chaddr[] = {[0 ... 15] = 0};/* clear every lease out that chaddr OR yiaddr matches and is nonzero */void clear_lease(uint8_t *chaddr, uint32_t yiaddr){	unsigned int i, j;	for (j = 0; j < 16 && !chaddr[j]; j++);	for (i = 0; i < server_config.max_leases; i++)		if ((j != 16 && !memcmp(leases[i].chaddr, chaddr, 16)) ||		    (yiaddr && leases[i].yiaddr == yiaddr)) {			memset(&(leases[i]), 0, sizeof(struct dhcpOfferedAddr));		}}/* add a lease into the table, clearing out any old ones */struct dhcpOfferedAddr *add_lease(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 oldest expired lease, NULL if there are no expired leases */struct dhcpOfferedAddr *oldest_expired_lease(void){	struct dhcpOfferedAddr *oldest = NULL;	unsigned long oldest_lease = time(0);	unsigned int 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;}/* Find the first lease that matches chaddr, NULL if no match */struct dhcpOfferedAddr *find_lease_by_chaddr(uint8_t *chaddr){	unsigned int 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 int 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 check_ip(uint32_t addr){	struct in_addr temp;	if (arpping(addr, server_config.server, server_config.arp, server_config.interface) == 0) {		temp.s_addr = addr;		LOG(LOG_INFO, "%s belongs to someone, reserving it for %ld seconds",			inet_ntoa(temp), server_config.conflict_time);		add_lease(blank_chaddr, addr, server_config.conflict_time);		return 1;	} else return 0;}/* find an assignable address, it 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 = ntohl(server_config.start); /* addr is in host order here */	for (;addr <= ntohl(server_config.end); 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 an assigned as a static lease */		if(!reservedIp(server_config.static_leases, htonl(addr)))		{		/* lease is not taken */		ret = htonl(addr);		if ((!(lease = find_lease_by_yiaddr(ret)) ||		     /* or it expired and we are checking for expired leases */		     (check_expired  && lease_expired(lease))) &&		     /* and it isn't on the network */		     !check_ip(ret)) {			return ret;			break;		}	}	}	return 0;}