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Sourcecode: udhcp version File versions

serverpacket.c

/* 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 "serverpacket.h"
#include "dhcpd.h"
#include "options.h"
#include "common.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 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 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)
{
      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(packet->sname, server_config.sname, sizeof(packet->sname) - 1);
      if (server_config.boot_file)
            strncpy(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);
}

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