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 "dhcpd.h"
  29 #include "options.h"
  30 #include "common.h"
  31
  32 /* send a packet to giaddr using the kernel ip stack */
  33 static int send_packet_to_relay(struct dhcpMessage *payload)
  34 {
  35         DEBUG(LOG_INFO, "Forwarding packet to relay");
  36
  37         return kernel_packet(payload, server_config.server, SERVER_PORT,
  38                         payload->giaddr, SERVER_PORT);
  39 }
  40
  41
  42 /* send a packet to a specific arp address and ip address by creating our own ip packet */
  43 static int send_packet_to_client(struct dhcpMessage *payload, int force_broadcast)
  44 {
  45         unsigned char *chaddr;
  46         u_int32_t ciaddr;
  47
  48         if (force_broadcast) {
  49                 DEBUG(LOG_INFO, "broadcasting packet to client (NAK)");
  50                 ciaddr = INADDR_BROADCAST;
  51                 chaddr = MAC_BCAST_ADDR;
  52         } else if (payload->ciaddr) {
  53                 DEBUG(LOG_INFO, "unicasting packet to client ciaddr");
  54                 ciaddr = payload->ciaddr;
  55                 chaddr = payload->chaddr;
  56         } else if (ntohs(payload->flags) & BROADCAST_FLAG) {
  57                 DEBUG(LOG_INFO, "broadcasting packet to client (requested)");
  58                 ciaddr = INADDR_BROADCAST;
  59                 chaddr = MAC_BCAST_ADDR;
  60         } else {
  61                 DEBUG(LOG_INFO, "unicasting packet to client yiaddr");
  62                 ciaddr = payload->yiaddr;
  63                 chaddr = payload->chaddr;
  64         }
  65         return raw_packet(payload, server_config.server, SERVER_PORT,
  66                         ciaddr, CLIENT_PORT, chaddr, server_config.ifindex);
  67 }
  68
  69
  70 /* send a dhcp packet, if force broadcast is set, the packet will be broadcast to the client */
  71 static int send_packet(struct dhcpMessage *payload, int force_broadcast)
  72 {
  73         int ret;
  74
  75         if (payload->giaddr)
  76                 ret = send_packet_to_relay(payload);
  77         else ret = send_packet_to_client(payload, force_broadcast);
  78         return ret;
  79 }
  80
  81
  82 static void init_packet(struct dhcpMessage *packet, struct dhcpMessage *oldpacket, char type)
  83 {
  84         init_header(packet, type);
  85         packet->xid = oldpacket->xid;
  86         memcpy(packet->chaddr, oldpacket->chaddr, 16);
  87         packet->flags = oldpacket->flags;
  88         packet->giaddr = oldpacket->giaddr;
  89         packet->ciaddr = oldpacket->ciaddr;
  90         add_simple_option(packet->options, DHCP_SERVER_ID, server_config.server);
  91 }
  92
  93
  94 /* add in the bootp options */
  95 static void add_bootp_options(struct dhcpMessage *packet)
  96 {
  97         packet->siaddr = server_config.siaddr;
  98         if (server_config.sname)
  99                 strncpy(packet->sname, server_config.sname, sizeof(packet->sname) - 1);
 100         if (server_config.boot_file)
 101                 strncpy(packet->file, server_config.boot_file, sizeof(packet->file) - 1);
 102 }
 103
 104
 105 /* send a DHCP OFFER to a DHCP DISCOVER */
 106 int sendOffer(struct dhcpMessage *oldpacket)
 107 {
 108         struct dhcpMessage packet;
 109         struct dhcpOfferedAddr *lease = NULL;
 110         u_int32_t req_align, lease_time_align = server_config.lease;
 111         unsigned char *req, *lease_time;
 112         struct option_set *curr;
 113         struct in_addr addr;
 114
 115         init_packet(&packet, oldpacket, DHCPOFFER);
 116
 117         /* ADDME: if static, short circuit */
 118         /* the client is in our lease/offered table */
 119         if ((lease = find_lease_by_chaddr(oldpacket->chaddr))) {
 120                 if (!lease_expired(lease))
 121                         lease_time_align = lease->expires - time(0);
 122                 packet.yiaddr = lease->yiaddr;
 123
 124         /* Or the client has a requested ip */
 125         } else if ((req = get_option(oldpacket, DHCP_REQUESTED_IP)) &&
 126
 127                    /* Don't look here (ugly hackish thing to do) */
 128                    memcpy(&req_align, req, 4) &&
 129
 130                    /* and the ip is in the lease range */
 131                    ntohl(req_align) >= ntohl(server_config.start) &&
 132                    ntohl(req_align) <= ntohl(server_config.end) &&
 133
 134                    /* and its not already taken/offered */ /* ADDME: check that its not a static lease */
 135                    ((!(lease = find_lease_by_yiaddr(req_align)) ||
 136
 137                    /* or its taken, but expired */ /* ADDME: or maybe in here */
 138                    lease_expired(lease)))) {
 139                                 packet.yiaddr = req_align; /* FIXME: oh my, is there a host using this IP? */
 140
 141         /* otherwise, find a free IP */ /*ADDME: is it a static lease? */
 142         } else {
 143                 packet.yiaddr = find_address(0);
 144
 145                 /* try for an expired lease */
 146                 if (!packet.yiaddr) packet.yiaddr = find_address(1);
 147         }
 148
 149         if(!packet.yiaddr) {
 150                 LOG(LOG_WARNING, "no IP addresses to give -- OFFER abandoned");
 151                 return -1;
 152         }
 153
 154         if (!add_lease(packet.chaddr, packet.yiaddr, server_config.offer_time)) {
 155                 LOG(LOG_WARNING, "lease pool is full -- OFFER abandoned");
 156                 return -1;
 157         }
 158
 159         if ((lease_time = get_option(oldpacket, DHCP_LEASE_TIME))) {
 160                 memcpy(&lease_time_align, lease_time, 4);
 161                 lease_time_align = ntohl(lease_time_align);
 162                 if (lease_time_align > server_config.lease)
 163                         lease_time_align = server_config.lease;
 164         }
 165
 166         /* Make sure we aren't just using the lease time from the previous offer */
 167         if (lease_time_align < server_config.min_lease)
 168                 lease_time_align = server_config.lease;
 169         /* ADDME: end of short circuit */
 170         add_simple_option(packet.options, DHCP_LEASE_TIME, htonl(lease_time_align));
 171
 172         curr = server_config.options;
 173         while (curr) {
 174                 if (curr->data[OPT_CODE] != DHCP_LEASE_TIME)
 175                         add_option_string(packet.options, curr->data);
 176                 curr = curr->next;
 177         }
 178
 179         add_bootp_options(&packet);
 180
 181         addr.s_addr = packet.yiaddr;
 182         LOG(LOG_INFO, "sending OFFER of %s", inet_ntoa(addr));
 183         return send_packet(&packet, 0);
 184 }
 185
 186
 187 int sendNAK(struct dhcpMessage *oldpacket)
 188 {
 189         struct dhcpMessage packet;
 190
 191         init_packet(&packet, oldpacket, DHCPNAK);
 192
 193         DEBUG(LOG_INFO, "sending NAK");
 194         return send_packet(&packet, 1);
 195 }
 196
 197
 198 int sendACK(struct dhcpMessage *oldpacket, u_int32_t yiaddr)
 199 {
 200         struct dhcpMessage packet;
 201         struct option_set *curr;
 202         unsigned char *lease_time;
 203         u_int32_t lease_time_align = server_config.lease;
 204         struct in_addr addr;
 205
 206         init_packet(&packet, oldpacket, DHCPACK);
 207         packet.yiaddr = yiaddr;
 208
 209         if ((lease_time = get_option(oldpacket, DHCP_LEASE_TIME))) {
 210                 memcpy(&lease_time_align, lease_time, 4);
 211                 lease_time_align = ntohl(lease_time_align);
 212                 if (lease_time_align > server_config.lease)
 213                         lease_time_align = server_config.lease;
 214                 else if (lease_time_align < server_config.min_lease)
 215                         lease_time_align = server_config.lease;
 216         }
 217
 218         add_simple_option(packet.options, DHCP_LEASE_TIME, htonl(lease_time_align));
 219
 220         curr = server_config.options;
 221         while (curr) {
 222                 if (curr->data[OPT_CODE] != DHCP_LEASE_TIME)
 223                         add_option_string(packet.options, curr->data);
 224                 curr = curr->next;
 225         }
 226
 227         add_bootp_options(&packet);
 228
 229         addr.s_addr = packet.yiaddr;
 230         LOG(LOG_INFO, "sending ACK to %s", inet_ntoa(addr));
 231
 232         if (send_packet(&packet, 0) < 0)
 233                 return -1;
 234
 235         add_lease(packet.chaddr, packet.yiaddr, lease_time_align);
 236
 237         return 0;
 238 }
 239
 240
 241 int send_inform(struct dhcpMessage *oldpacket)
 242 {
 243         struct dhcpMessage packet;
 244         struct option_set *curr;
 245
 246         init_packet(&packet, oldpacket, DHCPACK);
 247
 248         curr = server_config.options;
 249         while (curr) {
 250                 if (curr->data[OPT_CODE] != DHCP_LEASE_TIME)
 251                         add_option_string(packet.options, curr->data);
 252                 curr = curr->next;
 253         }
 254
 255         add_bootp_options(&packet);
 256
 257         return send_packet(&packet, 0);
 258 }