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 "serverpacket.h"
  29 #include "dhcpd.h"
  30 #include "options.h"
  31 #include "common.h"
  32
  33 /* send a packet to giaddr using the kernel ip stack */
  34 static int send_packet_to_relay(struct dhcpMessage *payload)
  35 {
  36         DEBUG(LOG_INFO, "Forwarding packet to relay");
  37
  38         return kernel_packet(payload, server_config.server, SERVER_PORT,
  39                         payload->giaddr, SERVER_PORT);
  40 }
  41
  42
  43 /* send a packet to a specific arp address and ip address by creating our own ip packet */
  44 static int send_packet_to_client(struct dhcpMessage *payload, int force_broadcast)
  45 {
  46         uint8_t *chaddr;
  47         uint32_t ciaddr;
  48
  49         if (force_broadcast) {
  50                 DEBUG(LOG_INFO, "broadcasting packet to client (NAK)");
  51                 ciaddr = INADDR_BROADCAST;
  52                 chaddr = MAC_BCAST_ADDR;
  53         } else if (payload->ciaddr) {
  54                 DEBUG(LOG_INFO, "unicasting packet to client ciaddr");
  55                 ciaddr = payload->ciaddr;
  56                 chaddr = payload->chaddr;
  57         } else if (ntohs(payload->flags) & BROADCAST_FLAG) {
  58                 DEBUG(LOG_INFO, "broadcasting packet to client (requested)");
  59                 ciaddr = INADDR_BROADCAST;
  60                 chaddr = MAC_BCAST_ADDR;
  61         } else {
  62                 DEBUG(LOG_INFO, "unicasting packet to client yiaddr");
  63                 ciaddr = payload->yiaddr;
  64                 chaddr = payload->chaddr;
  65         }
  66         return raw_packet(payload, server_config.server, SERVER_PORT,
  67                         ciaddr, CLIENT_PORT, chaddr, server_config.ifindex);
  68 }
  69
  70
  71 /* send a dhcp packet, if force broadcast is set, the packet will be broadcast to the client */
  72 static int send_packet(struct dhcpMessage *payload, int force_broadcast)
  73 {
  74         int ret;
  75
  76         if (payload->giaddr)
  77                 ret = send_packet_to_relay(payload);
  78         else ret = send_packet_to_client(payload, force_broadcast);
  79         return ret;
  80 }
  81
  82
  83 static void init_packet(struct dhcpMessage *packet, struct dhcpMessage *oldpacket, char type)
  84 {
  85         init_header(packet, type);
  86         packet->xid = oldpacket->xid;
  87         memcpy(packet->chaddr, oldpacket->chaddr, 16);
  88         packet->flags = oldpacket->flags;
  89         packet->giaddr = oldpacket->giaddr;
  90         packet->ciaddr = oldpacket->ciaddr;
  91         add_simple_option(packet->options, DHCP_SERVER_ID, server_config.server);
  92 }
  93
  94
  95 /* add in the bootp options */
  96 static void add_bootp_options(struct dhcpMessage *packet)
  97 {
  98         packet->siaddr = server_config.siaddr;
  99         if (server_config.sname)
 100                 strncpy(packet->sname, server_config.sname, sizeof(packet->sname) - 1);
 101         if (server_config.boot_file)
 102                 strncpy(packet->file, server_config.boot_file, sizeof(packet->file) - 1);
 103 }
 104
 105
 106 /* send a DHCP OFFER to a DHCP DISCOVER */
 107 int sendOffer(struct dhcpMessage *oldpacket)
 108 {
 109         struct dhcpMessage packet;
 110         struct dhcpOfferedAddr *lease = NULL;
 111         uint32_t req_align, lease_time_align = server_config.lease;
 112         uint8_t *req, *lease_time;
 113         struct option_set *curr;
 114         struct in_addr addr;
 115
 116         init_packet(&packet, oldpacket, DHCPOFFER);
 117
 118         /* ADDME: if static, short circuit */
 119         /* the client is in our lease/offered table */
 120         if ((lease = find_lease_by_chaddr(oldpacket->chaddr))) {
 121                 if (!lease_expired(lease))
 122                         lease_time_align = lease->expires - time(0);
 123                 packet.yiaddr = lease->yiaddr;
 124
 125         /* Or the client has a requested ip */
 126         } else if ((req = get_option(oldpacket, DHCP_REQUESTED_IP)) &&
 127
 128                    /* Don't look here (ugly hackish thing to do) */
 129                    memcpy(&req_align, req, 4) &&
 130
 131                    /* and the ip is in the lease range */
 132                    ntohl(req_align) >= ntohl(server_config.start) &&
 133                    ntohl(req_align) <= ntohl(server_config.end) &&
 134
 135                    /* and its not already taken/offered */ /* ADDME: check that its not a static lease */
 136                    ((!(lease = find_lease_by_yiaddr(req_align)) ||
 137
 138                    /* or its taken, but expired */ /* ADDME: or maybe in here */
 139                    lease_expired(lease)))) {
 140                                 packet.yiaddr = req_align; /* FIXME: oh my, is there a host using this IP? */
 141
 142         /* otherwise, find a free IP */ /*ADDME: is it a static lease? */
 143         } else {
 144                 packet.yiaddr = find_address(0);
 145
 146                 /* try for an expired lease */
 147                 if (!packet.yiaddr) packet.yiaddr = find_address(1);
 148         }
 149
 150         if(!packet.yiaddr) {
 151                 LOG(LOG_WARNING, "no IP addresses to give -- OFFER abandoned");
 152                 return -1;
 153         }
 154
 155         if (!add_lease(packet.chaddr, packet.yiaddr, server_config.offer_time)) {
 156                 LOG(LOG_WARNING, "lease pool is full -- OFFER abandoned");
 157                 return -1;
 158         }
 159
 160         if ((lease_time = get_option(oldpacket, DHCP_LEASE_TIME))) {
 161                 memcpy(&lease_time_align, lease_time, 4);
 162                 lease_time_align = ntohl(lease_time_align);
 163                 if (lease_time_align > server_config.lease)
 164                         lease_time_align = server_config.lease;
 165         }
 166
 167         /* Make sure we aren't just using the lease time from the previous offer */
 168         if (lease_time_align < server_config.min_lease)
 169                 lease_time_align = server_config.lease;
 170         /* ADDME: end of short circuit */
 171         add_simple_option(packet.options, DHCP_LEASE_TIME, htonl(lease_time_align));
 172
 173         curr = server_config.options;
 174         while (curr) {
 175                 if (curr->data[OPT_CODE] != DHCP_LEASE_TIME)
 176                         add_option_string(packet.options, curr->data);
 177                 curr = curr->next;
 178         }
 179
 180         add_bootp_options(&packet);
 181
 182         addr.s_addr = packet.yiaddr;
 183         LOG(LOG_INFO, "sending OFFER of %s", inet_ntoa(addr));
 184         return send_packet(&packet, 0);
 185 }
 186
 187
 188 int sendNAK(struct dhcpMessage *oldpacket)
 189 {
 190         struct dhcpMessage packet;
 191
 192         init_packet(&packet, oldpacket, DHCPNAK);
 193
 194         DEBUG(LOG_INFO, "sending NAK");
 195         return send_packet(&packet, 1);
 196 }
 197
 198
 199 int sendACK(struct dhcpMessage *oldpacket, uint32_t yiaddr)
 200 {
 201         struct dhcpMessage packet;
 202         struct option_set *curr;
 203         uint8_t *lease_time;
 204         uint32_t lease_time_align = server_config.lease;
 205         struct in_addr addr;
 206
 207         init_packet(&packet, oldpacket, DHCPACK);
 208         packet.yiaddr = yiaddr;
 209
 210         if ((lease_time = get_option(oldpacket, DHCP_LEASE_TIME))) {
 211                 memcpy(&lease_time_align, lease_time, 4);
 212                 lease_time_align = ntohl(lease_time_align);
 213                 if (lease_time_align > server_config.lease)
 214                         lease_time_align = server_config.lease;
 215                 else if (lease_time_align < server_config.min_lease)
 216                         lease_time_align = server_config.lease;
 217         }
 218
 219         add_simple_option(packet.options, DHCP_LEASE_TIME, htonl(lease_time_align));
 220
 221         curr = server_config.options;
 222         while (curr) {
 223                 if (curr->data[OPT_CODE] != DHCP_LEASE_TIME)
 224                         add_option_string(packet.options, curr->data);
 225                 curr = curr->next;
 226         }
 227
 228         add_bootp_options(&packet);
 229
 230         addr.s_addr = packet.yiaddr;
 231         LOG(LOG_INFO, "sending ACK to %s", inet_ntoa(addr));
 232
 233         if (send_packet(&packet, 0) < 0)
 234                 return -1;
 235
 236         add_lease(packet.chaddr, packet.yiaddr, lease_time_align);
 237
 238         return 0;
 239 }
 240
 241
 242 int send_inform(struct dhcpMessage *oldpacket)
 243 {
 244         struct dhcpMessage packet;
 245         struct option_set *curr;
 246
 247         init_packet(&packet, oldpacket, DHCPACK);
 248
 249         curr = server_config.options;
 250         while (curr) {
 251                 if (curr->data[OPT_CODE] != DHCP_LEASE_TIME)
 252                         add_option_string(packet.options, curr->data);
 253                 curr = curr->next;
 254         }
 255
 256         add_bootp_options(&packet);
 257
 258         return send_packet(&packet, 0);
 259 }