3 * Packet generation and dispatching functions for the DHCP client.
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.
23 #include <sys/socket.h>
25 #if __GLIBC__ >=2 && __GLIBC_MINOR >= 1
26 #include <netpacket/packet.h>
27 #include <net/ethernet.h>
29 #include <asm/types.h>
30 #include <linux/if_packet.h>
31 #include <linux/if_ether.h>
36 #include <netinet/in.h>
37 #include <arpa/inet.h>
42 #include "clientpacket.h"
48 /* Create a random xid */
49 unsigned long random_xid(void)
51 static int initialized;
56 fd = open("/dev/urandom", 0);
57 if (fd < 0 || read(fd, &seed, sizeof(seed)) < 0) {
58 LOG(LOG_WARNING, "Could not load seed from /dev/urandom: %m");
61 if (fd >= 0) close(fd);
69 /* initialize a packet with the proper defaults */
70 static void init_packet(struct dhcpMessage *packet, char type)
72 init_header(packet, type);
73 memcpy(packet->chaddr, client_config.arp, 6);
74 if (client_config.clientid)
75 add_option_string(packet->options, client_config.clientid);
76 if (client_config.hostname) add_option_string(packet->options, client_config.hostname);
77 if (client_config.fqdn) add_option_string(packet->options, client_config.fqdn);
78 add_option_string(packet->options, client_config.vendorclass);
82 /* Add a parameter request list for stubborn DHCP servers. Pull the data
83 * from the struct in options.c. Don't do bounds checking here because it
84 * goes towards the head of the packet. */
85 static void add_requests(struct dhcpMessage *packet)
87 int end = end_option(packet->options);
90 packet->options[end + OPT_CODE] = DHCP_PARAM_REQ;
91 for (i = 0; dhcp_options[i].code; i++)
92 if (dhcp_options[i].flags & OPTION_REQ)
93 packet->options[end + OPT_DATA + len++] = dhcp_options[i].code;
94 packet->options[end + OPT_LEN] = len;
95 packet->options[end + OPT_DATA + len] = DHCP_END;
100 /* Broadcast a DHCP discover packet to the network, with an optionally requested IP */
101 int send_discover(unsigned long xid, unsigned long requested)
103 struct dhcpMessage packet;
105 init_packet(&packet, DHCPDISCOVER);
108 add_simple_option(packet.options, DHCP_REQUESTED_IP, requested);
110 add_requests(&packet);
111 LOG(LOG_DEBUG, "Sending discover...");
112 return raw_packet(&packet, INADDR_ANY, CLIENT_PORT, INADDR_BROADCAST,
113 SERVER_PORT, MAC_BCAST_ADDR, client_config.ifindex);
117 /* Broadcasts a DHCP request message */
118 int send_selecting(unsigned long xid, unsigned long server, unsigned long requested)
120 struct dhcpMessage packet;
123 init_packet(&packet, DHCPREQUEST);
126 add_simple_option(packet.options, DHCP_REQUESTED_IP, requested);
127 add_simple_option(packet.options, DHCP_SERVER_ID, server);
129 add_requests(&packet);
130 addr.s_addr = requested;
131 LOG(LOG_DEBUG, "Sending select for %s...", inet_ntoa(addr));
132 return raw_packet(&packet, INADDR_ANY, CLIENT_PORT, INADDR_BROADCAST,
133 SERVER_PORT, MAC_BCAST_ADDR, client_config.ifindex);
137 /* Unicasts or broadcasts a DHCP renew message */
138 int send_renew(unsigned long xid, unsigned long server, unsigned long ciaddr)
140 struct dhcpMessage packet;
143 init_packet(&packet, DHCPREQUEST);
145 packet.ciaddr = ciaddr;
147 add_requests(&packet);
148 LOG(LOG_DEBUG, "Sending renew...");
150 ret = kernel_packet(&packet, ciaddr, CLIENT_PORT, server, SERVER_PORT);
151 else ret = raw_packet(&packet, INADDR_ANY, CLIENT_PORT, INADDR_BROADCAST,
152 SERVER_PORT, MAC_BCAST_ADDR, client_config.ifindex);
157 /* Unicasts a DHCP release message */
158 int send_release(unsigned long server, unsigned long ciaddr)
160 struct dhcpMessage packet;
162 init_packet(&packet, DHCPRELEASE);
163 packet.xid = random_xid();
164 packet.ciaddr = ciaddr;
166 add_simple_option(packet.options, DHCP_REQUESTED_IP, ciaddr);
167 add_simple_option(packet.options, DHCP_SERVER_ID, server);
169 LOG(LOG_DEBUG, "Sending release...");
170 return kernel_packet(&packet, ciaddr, CLIENT_PORT, server, SERVER_PORT);
174 /* return -1 on errors that are fatal for the socket, -2 for those that aren't */
175 int get_raw_packet(struct dhcpMessage *payload, int fd)
178 struct udp_dhcp_packet packet;
179 uint32_t source, dest;
182 memset(&packet, 0, sizeof(struct udp_dhcp_packet));
183 bytes = read(fd, &packet, sizeof(struct udp_dhcp_packet));
185 DEBUG(LOG_INFO, "couldn't read on raw listening socket -- ignoring");
186 usleep(500000); /* possible down interface, looping condition */
190 if (bytes < (int) (sizeof(struct iphdr) + sizeof(struct udphdr))) {
191 DEBUG(LOG_INFO, "message too short, ignoring");
195 if (bytes < ntohs(packet.ip.tot_len)) {
196 DEBUG(LOG_INFO, "Truncated packet");
200 /* ignore any extra garbage bytes */
201 bytes = ntohs(packet.ip.tot_len);
203 /* Make sure its the right packet for us, and that it passes sanity checks */
204 if (packet.ip.protocol != IPPROTO_UDP || packet.ip.version != IPVERSION ||
205 packet.ip.ihl != sizeof(packet.ip) >> 2 || packet.udp.dest != htons(CLIENT_PORT) ||
206 bytes > (int) sizeof(struct udp_dhcp_packet) ||
207 ntohs(packet.udp.len) != (uint16_t) (bytes - sizeof(packet.ip))) {
208 DEBUG(LOG_INFO, "unrelated/bogus packet");
212 /* check IP checksum */
213 check = packet.ip.check;
215 if (check != checksum(&(packet.ip), sizeof(packet.ip))) {
216 DEBUG(LOG_INFO, "bad IP header checksum, ignoring");
220 /* verify the UDP checksum by replacing the header with a psuedo header */
221 source = packet.ip.saddr;
222 dest = packet.ip.daddr;
223 check = packet.udp.check;
224 packet.udp.check = 0;
225 memset(&packet.ip, 0, sizeof(packet.ip));
227 packet.ip.protocol = IPPROTO_UDP;
228 packet.ip.saddr = source;
229 packet.ip.daddr = dest;
230 packet.ip.tot_len = packet.udp.len; /* cheat on the psuedo-header */
231 if (check && check != checksum(&packet, bytes)) {
232 DEBUG(LOG_ERR, "packet with bad UDP checksum received, ignoring");
236 memcpy(payload, &(packet.data), bytes - (sizeof(packet.ip) + sizeof(packet.udp)));
238 if (ntohl(payload->cookie) != DHCP_MAGIC) {
239 LOG(LOG_ERR, "received bogus message (bad magic) -- ignoring");
242 DEBUG(LOG_INFO, "oooooh!!! got some!");
243 return bytes - (sizeof(packet.ip) + sizeof(packet.udp));