git.maemo.org Git - busybox4maemo/blob - 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 "common.h"
  24 #include "dhcpc.h"
  25 #include "dhcpd.h"
  26 #include "options.h"
  27
  28
  29 /* send a packet to giaddr using the kernel ip stack */
  30 static int send_packet_to_relay(struct dhcpMessage *payload)
  31 {
  32         DEBUG("Forwarding packet to relay");
  33
  34         return udhcp_send_kernel_packet(payload, server_config.server, SERVER_PORT,
  35                         payload->giaddr, SERVER_PORT);
  36 }
  37
  38
  39 /* send a packet to a specific arp address and ip address by creating our own ip packet */
  40 static int send_packet_to_client(struct dhcpMessage *payload, int force_broadcast)
  41 {
  42         const uint8_t *chaddr;
  43         uint32_t ciaddr;
  44
  45         if (force_broadcast) {
  46                 DEBUG("broadcasting packet to client (NAK)");
  47                 ciaddr = INADDR_BROADCAST;
  48                 chaddr = MAC_BCAST_ADDR;
  49         } else if (payload->ciaddr) {
  50                 DEBUG("unicasting packet to client ciaddr");
  51                 ciaddr = payload->ciaddr;
  52                 chaddr = payload->chaddr;
  53         } else if (ntohs(payload->flags) & BROADCAST_FLAG) {
  54                 DEBUG("broadcasting packet to client (requested)");
  55                 ciaddr = INADDR_BROADCAST;
  56                 chaddr = MAC_BCAST_ADDR;
  57         } else {
  58                 DEBUG("unicasting packet to client yiaddr");
  59                 ciaddr = payload->yiaddr;
  60                 chaddr = payload->chaddr;
  61         }
  62         return udhcp_send_raw_packet(payload, server_config.server, SERVER_PORT,
  63                         ciaddr, CLIENT_PORT, chaddr, server_config.ifindex);
  64 }
  65
  66
  67 /* send a dhcp packet, if force broadcast is set, the packet will be broadcast to the client */
  68 static int send_packet(struct dhcpMessage *payload, int force_broadcast)
  69 {
  70         int ret;
  71
  72         if (payload->giaddr)
  73                 ret = send_packet_to_relay(payload);
  74         else ret = send_packet_to_client(payload, force_broadcast);
  75         return ret;
  76 }
  77
  78
  79 static void init_packet(struct dhcpMessage *packet, struct dhcpMessage *oldpacket, char type)
  80 {
  81         udhcp_init_header(packet, type);
  82         packet->xid = oldpacket->xid;
  83         memcpy(packet->chaddr, oldpacket->chaddr, 16);
  84         packet->flags = oldpacket->flags;
  85         packet->giaddr = oldpacket->giaddr;
  86         packet->ciaddr = oldpacket->ciaddr;
  87         add_simple_option(packet->options, DHCP_SERVER_ID, server_config.server);
  88 }
  89
  90
  91 /* add in the bootp options */
  92 static void add_bootp_options(struct dhcpMessage *packet)
  93 {
  94         packet->siaddr = server_config.siaddr;
  95         if (server_config.sname)
  96                 strncpy((char*)packet->sname, server_config.sname, sizeof(packet->sname) - 1);
  97         if (server_config.boot_file)
  98                 strncpy((char*)packet->file, server_config.boot_file, sizeof(packet->file) - 1);
  99 }
 100
 101
 102 /* send a DHCP OFFER to a DHCP DISCOVER */
 103 int sendOffer(struct dhcpMessage *oldpacket)
 104 {
 105         struct dhcpMessage packet;
 106         struct dhcpOfferedAddr *lease = NULL;
 107         uint32_t req_align, lease_time_align = server_config.lease;
 108         uint8_t *req, *lease_time;
 109         struct option_set *curr;
 110         struct in_addr addr;
 111
 112         uint32_t static_lease_ip;
 113
 114         init_packet(&packet, oldpacket, DHCPOFFER);
 115
 116         static_lease_ip = getIpByMac(server_config.static_leases, oldpacket->chaddr);
 117
 118         /* ADDME: if static, short circuit */
 119         if (!static_lease_ip) {
 120                 /* the client is in our lease/offered table */
 121                 lease = find_lease_by_chaddr(oldpacket->chaddr);
 122                 if (lease) {
 123                         if (!lease_expired(lease))
 124                                 lease_time_align = lease->expires - time(0);
 125                         packet.yiaddr = lease->yiaddr;
 126                 /* Or the client has a requested ip */
 127                 } else if ((req = get_option(oldpacket, DHCP_REQUESTED_IP))
 128                  /* Don't look here (ugly hackish thing to do) */
 129                  && memcpy(&req_align, req, 4)
 130                  /* and the ip is in the lease range */
 131                  && ntohl(req_align) >= server_config.start_ip
 132                  && ntohl(req_align) <= server_config.end_ip
 133                  && !static_lease_ip /* Check that its not a static lease */
 134                  /* and is not already taken/offered */
 135                  && (!(lease = find_lease_by_yiaddr(req_align))
 136                         /* or its taken, but expired */ /* ADDME: or maybe in here */
 137                         || lease_expired(lease))
 138                 ) {
 139                         packet.yiaddr = req_align; /* FIXME: oh my, is there a host using this IP? */
 140                         /* otherwise, find a free IP */
 141                 } else {
 142                         /* Is it a static lease? (No, because find_address skips static lease) */
 143                         packet.yiaddr = find_address(0);
 144                         /* try for an expired lease */
 145                         if (!packet.yiaddr)
 146                                 packet.yiaddr = find_address(1);
 147                 }
 148
 149                 if (!packet.yiaddr) {
 150                         bb_error_msg("no IP addresses to give - OFFER abandoned");
 151                         return -1;
 152                 }
 153                 if (!add_lease(packet.chaddr, packet.yiaddr, server_config.offer_time)) {
 154                         bb_error_msg("lease pool is full - OFFER abandoned");
 155                         return -1;
 156                 }
 157                 lease_time = get_option(oldpacket, DHCP_LEASE_TIME);
 158                 if (lease_time) {
 159                         memcpy(&lease_time_align, lease_time, 4);
 160                         lease_time_align = ntohl(lease_time_align);
 161                         if (lease_time_align > server_config.lease)
 162                                 lease_time_align = server_config.lease;
 163                 }
 164
 165                 /* Make sure we aren't just using the lease time from the previous offer */
 166                 if (lease_time_align < server_config.min_lease)
 167                         lease_time_align = server_config.lease;
 168                 /* ADDME: end of short circuit */
 169         } else {
 170                 /* It is a static lease... use it */
 171                 packet.yiaddr = static_lease_ip;
 172         }
 173
 174         add_simple_option(packet.options, DHCP_LEASE_TIME, htonl(lease_time_align));
 175
 176         curr = server_config.options;
 177         while (curr) {
 178                 if (curr->data[OPT_CODE] != DHCP_LEASE_TIME)
 179                         add_option_string(packet.options, curr->data);
 180                 curr = curr->next;
 181         }
 182
 183         add_bootp_options(&packet);
 184
 185         addr.s_addr = packet.yiaddr;
 186         bb_info_msg("Sending OFFER of %s", inet_ntoa(addr));
 187         return send_packet(&packet, 0);
 188 }
 189
 190
 191 int sendNAK(struct dhcpMessage *oldpacket)
 192 {
 193         struct dhcpMessage packet;
 194
 195         init_packet(&packet, oldpacket, DHCPNAK);
 196
 197         DEBUG("Sending NAK");
 198         return send_packet(&packet, 1);
 199 }
 200
 201
 202 int sendACK(struct dhcpMessage *oldpacket, uint32_t yiaddr)
 203 {
 204         struct dhcpMessage packet;
 205         struct option_set *curr;
 206         uint8_t *lease_time;
 207         uint32_t lease_time_align = server_config.lease;
 208         struct in_addr addr;
 209
 210         init_packet(&packet, oldpacket, DHCPACK);
 211         packet.yiaddr = yiaddr;
 212
 213         lease_time = get_option(oldpacket, DHCP_LEASE_TIME);
 214         if (lease_time) {
 215                 memcpy(&lease_time_align, lease_time, 4);
 216                 lease_time_align = ntohl(lease_time_align);
 217                 if (lease_time_align > server_config.lease)
 218                         lease_time_align = server_config.lease;
 219                 else if (lease_time_align < server_config.min_lease)
 220                         lease_time_align = server_config.lease;
 221         }
 222
 223         add_simple_option(packet.options, DHCP_LEASE_TIME, htonl(lease_time_align));
 224
 225         curr = server_config.options;
 226         while (curr) {
 227                 if (curr->data[OPT_CODE] != DHCP_LEASE_TIME)
 228                         add_option_string(packet.options, curr->data);
 229                 curr = curr->next;
 230         }
 231
 232         add_bootp_options(&packet);
 233
 234         addr.s_addr = packet.yiaddr;
 235         bb_info_msg("Sending ACK to %s", inet_ntoa(addr));
 236
 237         if (send_packet(&packet, 0) < 0)
 238                 return -1;
 239
 240         add_lease(packet.chaddr, packet.yiaddr, lease_time_align);
 241         if (ENABLE_FEATURE_UDHCPD_WRITE_LEASES_EARLY) {
 242                 /* rewrite the file with leases at every new acceptance */
 243                 write_leases();
 244         }
 245
 246         return 0;
 247 }
 248
 249
 250 int send_inform(struct dhcpMessage *oldpacket)
 251 {
 252         struct dhcpMessage packet;
 253         struct option_set *curr;
 254
 255         init_packet(&packet, oldpacket, DHCPACK);
 256
 257         curr = server_config.options;
 258         while (curr) {
 259                 if (curr->data[OPT_CODE] != DHCP_LEASE_TIME)
 260                         add_option_string(packet.options, curr->data);
 261                 curr = curr->next;
 262         }
 263
 264         add_bootp_options(&packet);
 265
 266         return send_packet(&packet, 0);
 267 }