source: MondoRescue/trunk/mindi-busybox/networking/udhcp/leases.c@ 904

/*
 * 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;
}