source: MondoRescue/branches/stable/mindi-busybox/networking/udhcp/serverpacket.c@ 821

/* serverpacket.c
 *
 * Construct and send DHCP server packets
 *
 * Russ Dill <Russ.Dill@asu.edu> July 2001
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <string.h>
#include <time.h>

#include "common.h"
#include "serverpacket.h"
#include "dhcpd.h"
#include "options.h"
#include "static_leases.h"

/* send a packet to giaddr using the kernel ip stack */
static int send_packet_to_relay(struct dhcpMessage *payload)
{
    DEBUG(LOG_INFO, "Forwarding packet to relay");

    return udhcp_kernel_packet(payload, server_config.server, SERVER_PORT,
            payload->giaddr, SERVER_PORT);
}


/* send a packet to a specific arp address and ip address by creating our own ip packet */
static int send_packet_to_client(struct dhcpMessage *payload, int force_broadcast)
{
    uint8_t *chaddr;
    uint32_t ciaddr;

    if (force_broadcast) {
        DEBUG(LOG_INFO, "broadcasting packet to client (NAK)");
        ciaddr = INADDR_BROADCAST;
        chaddr = MAC_BCAST_ADDR;
    } else if (payload->ciaddr) {
        DEBUG(LOG_INFO, "unicasting packet to client ciaddr");
        ciaddr = payload->ciaddr;
        chaddr = payload->chaddr;
    } else if (ntohs(payload->flags) & BROADCAST_FLAG) {
        DEBUG(LOG_INFO, "broadcasting packet to client (requested)");
        ciaddr = INADDR_BROADCAST;
        chaddr = MAC_BCAST_ADDR;
    } else {
        DEBUG(LOG_INFO, "unicasting packet to client yiaddr");
        ciaddr = payload->yiaddr;
        chaddr = payload->chaddr;
    }
    return udhcp_raw_packet(payload, server_config.server, SERVER_PORT,
            ciaddr, CLIENT_PORT, chaddr, server_config.ifindex);
}


/* send a dhcp packet, if force broadcast is set, the packet will be broadcast to the client */
static int send_packet(struct dhcpMessage *payload, int force_broadcast)
{
    int ret;

    if (payload->giaddr)
        ret = send_packet_to_relay(payload);
    else ret = send_packet_to_client(payload, force_broadcast);
    return ret;
}


static void init_packet(struct dhcpMessage *packet, struct dhcpMessage *oldpacket, char type)
{
    udhcp_init_header(packet, type);
    packet->xid = oldpacket->xid;
    memcpy(packet->chaddr, oldpacket->chaddr, 16);
    packet->flags = oldpacket->flags;
    packet->giaddr = oldpacket->giaddr;
    packet->ciaddr = oldpacket->ciaddr;
    add_simple_option(packet->options, DHCP_SERVER_ID, server_config.server);
}


/* add in the bootp options */
static void add_bootp_options(struct dhcpMessage *packet)
{
    packet->siaddr = server_config.siaddr;
    if (server_config.sname)
        strncpy((char*)packet->sname, server_config.sname, sizeof(packet->sname) - 1);
    if (server_config.boot_file)
        strncpy((char*)packet->file, server_config.boot_file, sizeof(packet->file) - 1);
}


/* send a DHCP OFFER to a DHCP DISCOVER */
int sendOffer(struct dhcpMessage *oldpacket)
{
    struct dhcpMessage packet;
    struct dhcpOfferedAddr *lease = NULL;
    uint32_t req_align, lease_time_align = server_config.lease;
    uint8_t *req, *lease_time;
    struct option_set *curr;
    struct in_addr addr;

    uint32_t static_lease_ip;

    init_packet(&packet, oldpacket, DHCPOFFER);

    static_lease_ip = getIpByMac(server_config.static_leases, oldpacket->chaddr);

    /* ADDME: if static, short circuit */
    if(!static_lease_ip)
    {
    /* the client is in our lease/offered table */
    if ((lease = find_lease_by_chaddr(oldpacket->chaddr))) {
        if (!lease_expired(lease))
            lease_time_align = lease->expires - time(0);
        packet.yiaddr = lease->yiaddr;

    /* Or the client has a requested ip */
    } else if ((req = get_option(oldpacket, DHCP_REQUESTED_IP)) &&

           /* Don't look here (ugly hackish thing to do) */
           memcpy(&req_align, req, 4) &&

           /* and the ip is in the lease range */
           ntohl(req_align) >= ntohl(server_config.start) &&
           ntohl(req_align) <= ntohl(server_config.end) &&

            !static_lease_ip &&  /* Check that its not a static lease */
            /* and is not already taken/offered */
           ((!(lease = find_lease_by_yiaddr(req_align)) ||

           /* or its taken, but expired */ /* ADDME: or maybe in here */
           lease_expired(lease)))) {
                packet.yiaddr = req_align; /* FIXME: oh my, is there a host using this IP? */

            /* otherwise, find a free IP */
    } else {
            /* Is it a static lease? (No, because find_address skips static lease) */
        packet.yiaddr = find_address(0);

        /* try for an expired lease */
        if (!packet.yiaddr) packet.yiaddr = find_address(1);
    }

    if(!packet.yiaddr) {
        LOG(LOG_WARNING, "no IP addresses to give -- OFFER abandoned");
        return -1;
    }

    if (!add_lease(packet.chaddr, packet.yiaddr, server_config.offer_time)) {
        LOG(LOG_WARNING, "lease pool is full -- OFFER abandoned");
        return -1;
    }

    if ((lease_time = get_option(oldpacket, DHCP_LEASE_TIME))) {
        memcpy(&lease_time_align, lease_time, 4);
        lease_time_align = ntohl(lease_time_align);
        if (lease_time_align > server_config.lease)
            lease_time_align = server_config.lease;
    }

    /* Make sure we aren't just using the lease time from the previous offer */
    if (lease_time_align < server_config.min_lease)
        lease_time_align = server_config.lease;
    }
    /* ADDME: end of short circuit */
    else
    {
        /* It is a static lease... use it */
        packet.yiaddr = static_lease_ip;
    }

    add_simple_option(packet.options, DHCP_LEASE_TIME, htonl(lease_time_align));

    curr = server_config.options;
    while (curr) {
        if (curr->data[OPT_CODE] != DHCP_LEASE_TIME)
            add_option_string(packet.options, curr->data);
        curr = curr->next;
    }

    add_bootp_options(&packet);

    addr.s_addr = packet.yiaddr;
    LOG(LOG_INFO, "sending OFFER of %s", inet_ntoa(addr));
    return send_packet(&packet, 0);
}


int sendNAK(struct dhcpMessage *oldpacket)
{
    struct dhcpMessage packet;

    init_packet(&packet, oldpacket, DHCPNAK);

    DEBUG(LOG_INFO, "sending NAK");
    return send_packet(&packet, 1);
}


int sendACK(struct dhcpMessage *oldpacket, uint32_t yiaddr)
{
    struct dhcpMessage packet;
    struct option_set *curr;
    uint8_t *lease_time;
    uint32_t lease_time_align = server_config.lease;
    struct in_addr addr;

    init_packet(&packet, oldpacket, DHCPACK);
    packet.yiaddr = yiaddr;

    if ((lease_time = get_option(oldpacket, DHCP_LEASE_TIME))) {
        memcpy(&lease_time_align, lease_time, 4);
        lease_time_align = ntohl(lease_time_align);
        if (lease_time_align > server_config.lease)
            lease_time_align = server_config.lease;
        else if (lease_time_align < server_config.min_lease)
            lease_time_align = server_config.lease;
    }

    add_simple_option(packet.options, DHCP_LEASE_TIME, htonl(lease_time_align));

    curr = server_config.options;
    while (curr) {
        if (curr->data[OPT_CODE] != DHCP_LEASE_TIME)
            add_option_string(packet.options, curr->data);
        curr = curr->next;
    }

    add_bootp_options(&packet);

    addr.s_addr = packet.yiaddr;
    LOG(LOG_INFO, "sending ACK to %s", inet_ntoa(addr));

    if (send_packet(&packet, 0) < 0)
        return -1;

    add_lease(packet.chaddr, packet.yiaddr, lease_time_align);

    return 0;
}


int send_inform(struct dhcpMessage *oldpacket)
{
    struct dhcpMessage packet;
    struct option_set *curr;

    init_packet(&packet, oldpacket, DHCPACK);

    curr = server_config.options;
    while (curr) {
        if (curr->data[OPT_CODE] != DHCP_LEASE_TIME)
            add_option_string(packet.options, curr->data);
        curr = curr->next;
    }

    add_bootp_options(&packet);

    return send_packet(&packet, 0);
}