networking/udhcp/serverpacket.c

   1 /* serverpacket.c
   2  *
   3  * Constuct and send DHCP server packets
   4  *
   5  * Russ Dill <Russ.Dill@asu.edu> July 2001
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License as published by
   9  * the Free Software Foundation; either version 2 of the License, or
  10  * (at your option) any later version.
  11  *
  12  * This program is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  * GNU General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU General Public License
  18  * along with this program; if not, write to the Free Software
  19  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  20  */
  21
  22 #include <sys/socket.h>
  23 #include <netinet/in.h>
  24 #include <arpa/inet.h>
  25 #include <string.h>
  26 #include <time.h>
  27
  28 #include "packet.h"
  29 #include "debug.h"
  30 #include "dhcpd.h"
  31 #include "options.h"
  32 #include "leases.h"
  33
  34 /* send a packet to giaddr using the kernel ip stack */
  35 static int send_packet_to_relay(struct dhcpMessage *payload)
  36 {
  37         DEBUG(LOG_INFO, "Forwarding packet to relay");
  38
  39         return kernel_packet(payload, server_config.server, SERVER_PORT,
  40                         payload->giaddr, SERVER_PORT);
  41 }
  42
  43
  44 /* send a packet to a specific arp address and ip address by creating our own ip packet */
  45 static int send_packet_to_client(struct dhcpMessage *payload, int force_broadcast)
  46 {
  47         unsigned char *chaddr;
  48         u_int32_t ciaddr;
  49
  50         if (force_broadcast) {
  51                 DEBUG(LOG_INFO, "broadcasting packet to client (NAK)");
  52                 ciaddr = INADDR_BROADCAST;
  53                 chaddr = MAC_BCAST_ADDR;
  54         } else if (payload->ciaddr) {
  55                 DEBUG(LOG_INFO, "unicasting packet to client ciaddr");
  56                 ciaddr = payload->ciaddr;
  57                 chaddr = payload->chaddr;
  58         } else if (ntohs(payload->flags) & BROADCAST_FLAG) {
  59                 DEBUG(LOG_INFO, "broadcasting packet to client (requested)");
  60                 ciaddr = INADDR_BROADCAST;
  61                 chaddr = MAC_BCAST_ADDR;
  62         } else {
  63                 DEBUG(LOG_INFO, "unicasting packet to client yiaddr");
  64                 ciaddr = payload->yiaddr;
  65                 chaddr = payload->chaddr;
  66         }
  67         return raw_packet(payload, server_config.server, SERVER_PORT,
  68                         ciaddr, CLIENT_PORT, chaddr, server_config.ifindex);
  69 }
  70
  71
  72 /* send a dhcp packet, if force broadcast is set, the packet will be broadcast to the client */
  73 static int send_packet(struct dhcpMessage *payload, int force_broadcast)
  74 {
  75         int ret;
  76
  77         if (payload->giaddr)
  78                 ret = send_packet_to_relay(payload);
  79         else ret = send_packet_to_client(payload, force_broadcast);
  80         return ret;
  81 }
  82
  83
  84 static void init_packet(struct dhcpMessage *packet, struct dhcpMessage *oldpacket, char type)
  85 {
  86         init_header(packet, type);
  87         packet->xid = oldpacket->xid;
  88         memcpy(packet->chaddr, oldpacket->chaddr, 16);
  89         packet->flags = oldpacket->flags;
  90         packet->giaddr = oldpacket->giaddr;
  91         packet->ciaddr = oldpacket->ciaddr;
  92         add_simple_option(packet->options, DHCP_SERVER_ID, server_config.server);
  93 }
  94
  95
  96 /* add in the bootp options */
  97 static void add_bootp_options(struct dhcpMessage *packet)
  98 {
  99         packet->siaddr = server_config.siaddr;
 100         if (server_config.sname)
 101                 strncpy(packet->sname, server_config.sname, sizeof(packet->sname) - 1);
 102         if (server_config.boot_file)
 103                 strncpy(packet->file, server_config.boot_file, sizeof(packet->file) - 1);
 104 }
 105
 106
 107 /* send a DHCP OFFER to a DHCP DISCOVER */
 108 int sendOffer(struct dhcpMessage *oldpacket)
 109 {
 110         struct dhcpMessage packet;
 111         struct dhcpOfferedAddr *lease = NULL;
 112         u_int32_t req_align, lease_time_align = server_config.lease;
 113         unsigned char *req, *lease_time;
 114         struct option_set *curr;
 115         struct in_addr addr;
 116
 117         init_packet(&packet, oldpacket, DHCPOFFER);
 118
 119         /* ADDME: if static, short circuit */
 120         /* the client is in our lease/offered table */
 121         if ((lease = find_lease_by_chaddr(oldpacket->chaddr))) {
 122                 if (!lease_expired(lease))
 123                         lease_time_align = lease->expires - time(0);
 124                 packet.yiaddr = lease->yiaddr;
 125
 126         /* Or the client has a requested ip */
 127         } else if ((req = get_option(oldpacket, DHCP_REQUESTED_IP)) &&
 128
 129                    /* Don't look here (ugly hackish thing to do) */
 130                    memcpy(&req_align, req, 4) &&
 131
 132                    /* and the ip is in the lease range */
 133                    ntohl(req_align) >= ntohl(server_config.start) &&
 134                    ntohl(req_align) <= ntohl(server_config.end) &&
 135
 136                    /* and its not already taken/offered */ /* ADDME: check that its not a static lease */
 137                    ((!(lease = find_lease_by_yiaddr(req_align)) ||
 138
 139                    /* or its taken, but expired */ /* ADDME: or maybe in here */
 140                    lease_expired(lease)))) {
 141                                 packet.yiaddr = req_align; /* FIXME: oh my, is there a host using this IP? */
 142
 143         /* otherwise, find a free IP */ /*ADDME: is it a static lease? */
 144         } else {
 145                 packet.yiaddr = find_address(0);
 146
 147                 /* try for an expired lease */
 148                 if (!packet.yiaddr) packet.yiaddr = find_address(1);
 149         }
 150
 151         if(!packet.yiaddr) {
 152                 LOG(LOG_WARNING, "no IP addresses to give -- OFFER abandoned");
 153                 return -1;
 154         }
 155
 156         if (!add_lease(packet.chaddr, packet.yiaddr, server_config.offer_time)) {
 157                 LOG(LOG_WARNING, "lease pool is full -- OFFER abandoned");
 158                 return -1;
 159         }
 160
 161         if ((lease_time = get_option(oldpacket, DHCP_LEASE_TIME))) {
 162                 memcpy(&lease_time_align, lease_time, 4);
 163                 lease_time_align = ntohl(lease_time_align);
 164                 if (lease_time_align > server_config.lease)
 165                         lease_time_align = server_config.lease;
 166         }
 167
 168         /* Make sure we aren't just using the lease time from the previous offer */
 169         if (lease_time_align < server_config.min_lease)
 170                 lease_time_align = server_config.lease;
 171         /* ADDME: end of short circuit */
 172         add_simple_option(packet.options, DHCP_LEASE_TIME, htonl(lease_time_align));
 173
 174         curr = server_config.options;
 175         while (curr) {
 176                 if (curr->data[OPT_CODE] != DHCP_LEASE_TIME)
 177                         add_option_string(packet.options, curr->data);
 178                 curr = curr->next;
 179         }
 180
 181         add_bootp_options(&packet);
 182
 183         addr.s_addr = packet.yiaddr;
 184         LOG(LOG_INFO, "sending OFFER of %s", inet_ntoa(addr));
 185         return send_packet(&packet, 0);
 186 }
 187
 188
 189 int sendNAK(struct dhcpMessage *oldpacket)
 190 {
 191         struct dhcpMessage packet;
 192
 193         init_packet(&packet, oldpacket, DHCPNAK);
 194
 195         DEBUG(LOG_INFO, "sending NAK");
 196         return send_packet(&packet, 1);
 197 }
 198
 199
 200 int sendACK(struct dhcpMessage *oldpacket, u_int32_t yiaddr)
 201 {
 202         struct dhcpMessage packet;
 203         struct option_set *curr;
 204         unsigned char *lease_time;
 205         u_int32_t lease_time_align = server_config.lease;
 206         struct in_addr addr;
 207
 208         init_packet(&packet, oldpacket, DHCPACK);
 209         packet.yiaddr = yiaddr;
 210
 211         if ((lease_time = get_option(oldpacket, DHCP_LEASE_TIME))) {
 212                 memcpy(&lease_time_align, lease_time, 4);
 213                 lease_time_align = ntohl(lease_time_align);
 214                 if (lease_time_align > server_config.lease)
 215                         lease_time_align = server_config.lease;
 216                 else if (lease_time_align < server_config.min_lease)
 217                         lease_time_align = server_config.lease;
 218         }
 219
 220         add_simple_option(packet.options, DHCP_LEASE_TIME, htonl(lease_time_align));
 221
 222         curr = server_config.options;
 223         while (curr) {
 224                 if (curr->data[OPT_CODE] != DHCP_LEASE_TIME)
 225                         add_option_string(packet.options, curr->data);
 226                 curr = curr->next;
 227         }
 228
 229         add_bootp_options(&packet);
 230
 231         addr.s_addr = packet.yiaddr;
 232         LOG(LOG_INFO, "sending ACK to %s", inet_ntoa(addr));
 233
 234         if (send_packet(&packet, 0) < 0)
 235                 return -1;
 236
 237         add_lease(packet.chaddr, packet.yiaddr, lease_time_align);
 238
 239         return 0;
 240 }
 241
 242
 243 int send_inform(struct dhcpMessage *oldpacket)
 244 {
 245         struct dhcpMessage packet;
 246         struct option_set *curr;
 247
 248         init_packet(&packet, oldpacket, DHCPACK);
 249
 250         curr = server_config.options;
 251         while (curr) {
 252                 if (curr->data[OPT_CODE] != DHCP_LEASE_TIME)
 253                         add_option_string(packet.options, curr->data);
 254                 curr = curr->next;
 255         }
 256
 257         add_bootp_options(&packet);
 258
 259         return send_packet(&packet, 0);
 260 }
 261
 262
 263