networking/udhcp/serverpacket.c

   1 /* vi: set sw=4 ts=4: */
   2 /* serverpacket.c
   3  *
   4  * Construct and send DHCP server packets
   5  *
   6  * Russ Dill <Russ.Dill@asu.edu> July 2001
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License as published by
  10  * the Free Software Foundation; either version 2 of the License, or
  11  * (at your option) any later version.
  12  *
  13  * This program is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16  * GNU General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU General Public License
  19  * along with this program; if not, write to the Free Software
  20  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  21  */
  22
  23 #include <sys/socket.h>
  24 #include <netinet/in.h>
  25 #include <arpa/inet.h>
  26 #include <string.h>
  27 #include <time.h>
  28
  29 #include "common.h"
  30 #include "serverpacket.h"
  31 #include "dhcpd.h"
  32 #include "options.h"
  33 #include "static_leases.h"
  34
  35 /* send a packet to giaddr using the kernel ip stack */
  36 static int send_packet_to_relay(struct dhcpMessage *payload)
  37 {
  38         DEBUG("Forwarding packet to relay");
  39
  40         return udhcp_kernel_packet(payload, server_config.server, SERVER_PORT,
  41                         payload->giaddr, SERVER_PORT);
  42 }
  43
  44
  45 /* send a packet to a specific arp address and ip address by creating our own ip packet */
  46 static int send_packet_to_client(struct dhcpMessage *payload, int force_broadcast)
  47 {
  48         uint8_t *chaddr;
  49         uint32_t ciaddr;
  50
  51         if (force_broadcast) {
  52                 DEBUG("broadcasting packet to client (NAK)");
  53                 ciaddr = INADDR_BROADCAST;
  54                 chaddr = MAC_BCAST_ADDR;
  55         } else if (payload->ciaddr) {
  56                 DEBUG("unicasting packet to client ciaddr");
  57                 ciaddr = payload->ciaddr;
  58                 chaddr = payload->chaddr;
  59         } else if (ntohs(payload->flags) & BROADCAST_FLAG) {
  60                 DEBUG("broadcasting packet to client (requested)");
  61                 ciaddr = INADDR_BROADCAST;
  62                 chaddr = MAC_BCAST_ADDR;
  63         } else {
  64                 DEBUG("unicasting packet to client yiaddr");
  65                 ciaddr = payload->yiaddr;
  66                 chaddr = payload->chaddr;
  67         }
  68         return udhcp_raw_packet(payload, server_config.server, SERVER_PORT,
  69                         ciaddr, CLIENT_PORT, chaddr, server_config.ifindex);
  70 }
  71
  72
  73 /* send a dhcp packet, if force broadcast is set, the packet will be broadcast to the client */
  74 static int send_packet(struct dhcpMessage *payload, int force_broadcast)
  75 {
  76         int ret;
  77
  78         if (payload->giaddr)
  79                 ret = send_packet_to_relay(payload);
  80         else ret = send_packet_to_client(payload, force_broadcast);
  81         return ret;
  82 }
  83
  84
  85 static void init_packet(struct dhcpMessage *packet, struct dhcpMessage *oldpacket, char type)
  86 {
  87         udhcp_init_header(packet, type);
  88         packet->xid = oldpacket->xid;
  89         memcpy(packet->chaddr, oldpacket->chaddr, 16);
  90         packet->flags = oldpacket->flags;
  91         packet->giaddr = oldpacket->giaddr;
  92         packet->ciaddr = oldpacket->ciaddr;
  93         add_simple_option(packet->options, DHCP_SERVER_ID, server_config.server);
  94 }
  95
  96
  97 /* add in the bootp options */
  98 static void add_bootp_options(struct dhcpMessage *packet)
  99 {
 100         packet->siaddr = server_config.siaddr;
 101         if (server_config.sname)
 102                 strncpy((char*)packet->sname, server_config.sname, sizeof(packet->sname) - 1);
 103         if (server_config.boot_file)
 104                 strncpy((char*)packet->file, server_config.boot_file, sizeof(packet->file) - 1);
 105 }
 106
 107
 108 /* send a DHCP OFFER to a DHCP DISCOVER */
 109 int sendOffer(struct dhcpMessage *oldpacket)
 110 {
 111         struct dhcpMessage packet;
 112         struct dhcpOfferedAddr *lease = NULL;
 113         uint32_t req_align, lease_time_align = server_config.lease;
 114         uint8_t *req, *lease_time;
 115         struct option_set *curr;
 116         struct in_addr addr;
 117
 118         uint32_t static_lease_ip;
 119
 120         init_packet(&packet, oldpacket, DHCPOFFER);
 121
 122         static_lease_ip = getIpByMac(server_config.static_leases, oldpacket->chaddr);
 123
 124         /* ADDME: if static, short circuit */
 125         if(!static_lease_ip)
 126         {
 127         /* the client is in our lease/offered table */
 128         if ((lease = find_lease_by_chaddr(oldpacket->chaddr))) {
 129                 if (!lease_expired(lease))
 130                         lease_time_align = lease->expires - time(0);
 131                 packet.yiaddr = lease->yiaddr;
 132
 133         /* Or the client has a requested ip */
 134         } else if ((req = get_option(oldpacket, DHCP_REQUESTED_IP)) &&
 135
 136                    /* Don't look here (ugly hackish thing to do) */
 137                    memcpy(&req_align, req, 4) &&
 138
 139                    /* and the ip is in the lease range */
 140                    ntohl(req_align) >= ntohl(server_config.start) &&
 141                    ntohl(req_align) <= ntohl(server_config.end) &&
 142
 143                         !static_lease_ip &&  /* Check that its not a static lease */
 144                         /* and is not already taken/offered */
 145                    ((!(lease = find_lease_by_yiaddr(req_align)) ||
 146
 147                    /* or its taken, but expired */ /* ADDME: or maybe in here */
 148                    lease_expired(lease)))) {
 149                                 packet.yiaddr = req_align; /* FIXME: oh my, is there a host using this IP? */
 150
 151                         /* otherwise, find a free IP */
 152         } else {
 153                         /* Is it a static lease? (No, because find_address skips static lease) */
 154                 packet.yiaddr = find_address(0);
 155
 156                 /* try for an expired lease */
 157                 if (!packet.yiaddr) packet.yiaddr = find_address(1);
 158         }
 159
 160         if(!packet.yiaddr) {
 161                 bb_error_msg("no IP addresses to give - OFFER abandoned");
 162                 return -1;
 163         }
 164
 165         if (!add_lease(packet.chaddr, packet.yiaddr, server_config.offer_time)) {
 166                 bb_error_msg("lease pool is full - OFFER abandoned");
 167                 return -1;
 168         }
 169
 170         if ((lease_time = get_option(oldpacket, DHCP_LEASE_TIME))) {
 171                 memcpy(&lease_time_align, lease_time, 4);
 172                 lease_time_align = ntohl(lease_time_align);
 173                 if (lease_time_align > server_config.lease)
 174                         lease_time_align = server_config.lease;
 175         }
 176
 177         /* Make sure we aren't just using the lease time from the previous offer */
 178         if (lease_time_align < server_config.min_lease)
 179                 lease_time_align = server_config.lease;
 180         }
 181         /* ADDME: end of short circuit */
 182         else
 183         {
 184                 /* It is a static lease... use it */
 185                 packet.yiaddr = static_lease_ip;
 186         }
 187
 188         add_simple_option(packet.options, DHCP_LEASE_TIME, htonl(lease_time_align));
 189
 190         curr = server_config.options;
 191         while (curr) {
 192                 if (curr->data[OPT_CODE] != DHCP_LEASE_TIME)
 193                         add_option_string(packet.options, curr->data);
 194                 curr = curr->next;
 195         }
 196
 197         add_bootp_options(&packet);
 198
 199         addr.s_addr = packet.yiaddr;
 200         bb_info_msg("Sending OFFER of %s", inet_ntoa(addr));
 201         return send_packet(&packet, 0);
 202 }
 203
 204
 205 int sendNAK(struct dhcpMessage *oldpacket)
 206 {
 207         struct dhcpMessage packet;
 208
 209         init_packet(&packet, oldpacket, DHCPNAK);
 210
 211         DEBUG("Sending NAK");
 212         return send_packet(&packet, 1);
 213 }
 214
 215
 216 int sendACK(struct dhcpMessage *oldpacket, uint32_t yiaddr)
 217 {
 218         struct dhcpMessage packet;
 219         struct option_set *curr;
 220         uint8_t *lease_time;
 221         uint32_t lease_time_align = server_config.lease;
 222         struct in_addr addr;
 223
 224         init_packet(&packet, oldpacket, DHCPACK);
 225         packet.yiaddr = yiaddr;
 226
 227         if ((lease_time = get_option(oldpacket, DHCP_LEASE_TIME))) {
 228                 memcpy(&lease_time_align, lease_time, 4);
 229                 lease_time_align = ntohl(lease_time_align);
 230                 if (lease_time_align > server_config.lease)
 231                         lease_time_align = server_config.lease;
 232                 else if (lease_time_align < server_config.min_lease)
 233                         lease_time_align = server_config.lease;
 234         }
 235
 236         add_simple_option(packet.options, DHCP_LEASE_TIME, htonl(lease_time_align));
 237
 238         curr = server_config.options;
 239         while (curr) {
 240                 if (curr->data[OPT_CODE] != DHCP_LEASE_TIME)
 241                         add_option_string(packet.options, curr->data);
 242                 curr = curr->next;
 243         }
 244
 245         add_bootp_options(&packet);
 246
 247         addr.s_addr = packet.yiaddr;
 248         bb_info_msg("Sending ACK to %s", inet_ntoa(addr));
 249
 250         if (send_packet(&packet, 0) < 0)
 251                 return -1;
 252
 253         add_lease(packet.chaddr, packet.yiaddr, lease_time_align);
 254
 255         return 0;
 256 }
 257
 258
 259 int send_inform(struct dhcpMessage *oldpacket)
 260 {
 261         struct dhcpMessage packet;
 262         struct option_set *curr;
 263
 264         init_packet(&packet, oldpacket, DHCPACK);
 265
 266         curr = server_config.options;
 267         while (curr) {
 268                 if (curr->data[OPT_CODE] != DHCP_LEASE_TIME)
 269                         add_option_string(packet.options, curr->data);
 270                 curr = curr->next;
 271         }
 272
 273         add_bootp_options(&packet);
 274
 275         return send_packet(&packet, 0);
 276 }