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

/* vi: set sw=4 ts=4: */
/* 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 "common.h"
#include "dhcpd.h"
#include "options.h"


/* send a packet to giaddr using the kernel ip stack */
static int send_packet_to_relay(struct dhcpMessage *payload)
{
    DEBUG("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)
{
    const uint8_t *chaddr;
    uint32_t ciaddr;

    if (force_broadcast) {
        DEBUG("broadcasting packet to client (NAK)");
        ciaddr = INADDR_BROADCAST;
        chaddr = MAC_BCAST_ADDR;
    } else if (payload->ciaddr) {
        DEBUG("unicasting packet to client ciaddr");
        ciaddr = payload->ciaddr;
        chaddr = payload->chaddr;
    } else if (ntohs(payload->flags) & BROADCAST_FLAG) {
        DEBUG("broadcasting packet to client (requested)");
        ciaddr = INADDR_BROADCAST;
        chaddr = MAC_BCAST_ADDR;
    } else {
        DEBUG("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 */
        lease = find_lease_by_chaddr(oldpacket->chaddr);
        if (lease) {
            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) >= server_config.start_ip
         && ntohl(req_align) <= server_config.end_ip
         && !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) {
            bb_error_msg("no IP addresses to give - OFFER abandoned");
            return -1;
        }
        if (!add_lease(packet.chaddr, packet.yiaddr, server_config.offer_time)) {
            bb_error_msg("lease pool is full - OFFER abandoned");
            return -1;
        }
        lease_time = get_option(oldpacket, DHCP_LEASE_TIME);
        if (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;
    bb_info_msg("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("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;

    lease_time = get_option(oldpacket, DHCP_LEASE_TIME);
    if (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;
    bb_info_msg("Sending ACK to %s", inet_ntoa(addr));

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

    add_lease(packet.chaddr, packet.yiaddr, lease_time_align);
    if (ENABLE_FEATURE_UDHCPD_WRITE_LEASES_EARLY) {
        /* rewrite the file with leases at every new acceptance */
        write_leases();
    }

    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);
}