3 * Constuct and send DHCP server packets
5 * Russ Dill <Russ.Dill@asu.edu> July 2001
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.
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.
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.
22 #include <sys/socket.h>
23 #include <netinet/in.h>
24 #include <arpa/inet.h>
32 /* send a packet to giaddr using the kernel ip stack */
33 static int send_packet_to_relay(struct dhcpMessage *payload)
35 DEBUG(LOG_INFO, "Forwarding packet to relay");
37 return kernel_packet(payload, server_config.server, SERVER_PORT,
38 payload->giaddr, SERVER_PORT);
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)
45 unsigned char *chaddr;
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;
61 DEBUG(LOG_INFO, "unicasting packet to client yiaddr");
62 ciaddr = payload->yiaddr;
63 chaddr = payload->chaddr;
65 return raw_packet(payload, server_config.server, SERVER_PORT,
66 ciaddr, CLIENT_PORT, chaddr, server_config.ifindex);
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)
76 ret = send_packet_to_relay(payload);
77 else ret = send_packet_to_client(payload, force_broadcast);
82 static void init_packet(struct dhcpMessage *packet, struct dhcpMessage *oldpacket, char type)
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);
94 /* add in the bootp options */
95 static void add_bootp_options(struct dhcpMessage *packet)
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);
105 /* send a DHCP OFFER to a DHCP DISCOVER */
106 int sendOffer(struct dhcpMessage *oldpacket)
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;
115 init_packet(&packet, oldpacket, DHCPOFFER);
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;
124 /* Or the client has a requested ip */
125 } else if ((req = get_option(oldpacket, DHCP_REQUESTED_IP)) &&
127 /* Don't look here (ugly hackish thing to do) */
128 memcpy(&req_align, req, 4) &&
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) &&
134 /* and its not already taken/offered */ /* ADDME: check that its not a static lease */
135 ((!(lease = find_lease_by_yiaddr(req_align)) ||
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? */
141 /* otherwise, find a free IP */ /*ADDME: is it a static lease? */
143 packet.yiaddr = find_address(0);
145 /* try for an expired lease */
146 if (!packet.yiaddr) packet.yiaddr = find_address(1);
150 LOG(LOG_WARNING, "no IP addresses to give -- OFFER abandoned");
154 if (!add_lease(packet.chaddr, packet.yiaddr, server_config.offer_time)) {
155 LOG(LOG_WARNING, "lease pool is full -- OFFER abandoned");
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;
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));
172 curr = server_config.options;
174 if (curr->data[OPT_CODE] != DHCP_LEASE_TIME)
175 add_option_string(packet.options, curr->data);
179 add_bootp_options(&packet);
181 addr.s_addr = packet.yiaddr;
182 LOG(LOG_INFO, "sending OFFER of %s", inet_ntoa(addr));
183 return send_packet(&packet, 0);
187 int sendNAK(struct dhcpMessage *oldpacket)
189 struct dhcpMessage packet;
191 init_packet(&packet, oldpacket, DHCPNAK);
193 DEBUG(LOG_INFO, "sending NAK");
194 return send_packet(&packet, 1);
198 int sendACK(struct dhcpMessage *oldpacket, u_int32_t yiaddr)
200 struct dhcpMessage packet;
201 struct option_set *curr;
202 unsigned char *lease_time;
203 u_int32_t lease_time_align = server_config.lease;
206 init_packet(&packet, oldpacket, DHCPACK);
207 packet.yiaddr = yiaddr;
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;
218 add_simple_option(packet.options, DHCP_LEASE_TIME, htonl(lease_time_align));
220 curr = server_config.options;
222 if (curr->data[OPT_CODE] != DHCP_LEASE_TIME)
223 add_option_string(packet.options, curr->data);
227 add_bootp_options(&packet);
229 addr.s_addr = packet.yiaddr;
230 LOG(LOG_INFO, "sending ACK to %s", inet_ntoa(addr));
232 if (send_packet(&packet, 0) < 0)
235 add_lease(packet.chaddr, packet.yiaddr, lease_time_align);
241 int send_inform(struct dhcpMessage *oldpacket)
243 struct dhcpMessage packet;
244 struct option_set *curr;
246 init_packet(&packet, oldpacket, DHCPACK);
248 curr = server_config.options;
250 if (curr->data[OPT_CODE] != DHCP_LEASE_TIME)
251 add_option_string(packet.options, curr->data);
255 add_bootp_options(&packet);
257 return send_packet(&packet, 0);