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>
47 /* Create a random xid */
48 unsigned long random_xid(void)
50 static int initialized;
55 fd = open("/dev/urandom", 0);
56 if (fd < 0 || read(fd, &seed, sizeof(seed)) < 0) {
57 LOG(LOG_WARNING, "Could not load seed from /dev/urandom: %m");
60 if (fd >= 0) close(fd);
68 /* initialize a packet with the proper defaults */
69 static void init_packet(struct dhcpMessage *packet, char type)
73 char str[sizeof("udhcp "VERSION)];
74 } vendor_id = { DHCP_VENDOR, sizeof("udhcp "VERSION) - 1, "udhcp "VERSION};
76 init_header(packet, type);
77 memcpy(packet->chaddr, client_config.arp, 6);
78 add_option_string(packet->options, client_config.clientid);
79 if (client_config.hostname) add_option_string(packet->options, client_config.hostname);
80 add_option_string(packet->options, (unsigned char *) &vendor_id);
84 /* Add a paramater request list for stubborn DHCP servers. Pull the data
85 * from the struct in options.c. Don't do bounds checking here because it
86 * goes towards the head of the packet. */
87 static void add_requests(struct dhcpMessage *packet)
89 int end = end_option(packet->options);
92 packet->options[end + OPT_CODE] = DHCP_PARAM_REQ;
93 for (i = 0; options[i].code; i++)
94 if (options[i].flags & OPTION_REQ)
95 packet->options[end + OPT_DATA + len++] = options[i].code;
96 packet->options[end + OPT_LEN] = len;
97 packet->options[end + OPT_DATA + len] = DHCP_END;
102 /* Broadcast a DHCP discover packet to the network, with an optionally requested IP */
103 int send_discover(unsigned long xid, unsigned long requested)
105 struct dhcpMessage packet;
107 init_packet(&packet, DHCPDISCOVER);
110 add_simple_option(packet.options, DHCP_REQUESTED_IP, requested);
112 add_requests(&packet);
113 LOG(LOG_DEBUG, "Sending discover...");
114 return raw_packet(&packet, INADDR_ANY, CLIENT_PORT, INADDR_BROADCAST,
115 SERVER_PORT, MAC_BCAST_ADDR, client_config.ifindex);
119 /* Broadcasts a DHCP request message */
120 int send_selecting(unsigned long xid, unsigned long server, unsigned long requested)
122 struct dhcpMessage packet;
125 init_packet(&packet, DHCPREQUEST);
128 add_simple_option(packet.options, DHCP_REQUESTED_IP, requested);
129 add_simple_option(packet.options, DHCP_SERVER_ID, server);
131 add_requests(&packet);
132 addr.s_addr = requested;
133 LOG(LOG_DEBUG, "Sending select for %s...", inet_ntoa(addr));
134 return raw_packet(&packet, INADDR_ANY, CLIENT_PORT, INADDR_BROADCAST,
135 SERVER_PORT, MAC_BCAST_ADDR, client_config.ifindex);
139 /* Unicasts or broadcasts a DHCP renew message */
140 int send_renew(unsigned long xid, unsigned long server, unsigned long ciaddr)
142 struct dhcpMessage packet;
145 init_packet(&packet, DHCPREQUEST);
147 packet.ciaddr = ciaddr;
149 add_requests(&packet);
150 LOG(LOG_DEBUG, "Sending renew...");
152 ret = kernel_packet(&packet, ciaddr, CLIENT_PORT, server, SERVER_PORT);
153 else ret = raw_packet(&packet, INADDR_ANY, CLIENT_PORT, INADDR_BROADCAST,
154 SERVER_PORT, MAC_BCAST_ADDR, client_config.ifindex);
159 /* Unicasts a DHCP release message */
160 int send_release(unsigned long server, unsigned long ciaddr)
162 struct dhcpMessage packet;
164 init_packet(&packet, DHCPRELEASE);
165 packet.xid = random_xid();
166 packet.ciaddr = ciaddr;
168 add_simple_option(packet.options, DHCP_REQUESTED_IP, ciaddr);
169 add_simple_option(packet.options, DHCP_SERVER_ID, server);
171 LOG(LOG_DEBUG, "Sending release...");
172 return kernel_packet(&packet, ciaddr, CLIENT_PORT, server, SERVER_PORT);
176 /* return -1 on errors that are fatal for the socket, -2 for those that aren't */
177 int get_raw_packet(struct dhcpMessage *payload, int fd)
180 struct udp_dhcp_packet packet;
181 u_int32_t source, dest;
184 memset(&packet, 0, sizeof(struct udp_dhcp_packet));
185 bytes = read(fd, &packet, sizeof(struct udp_dhcp_packet));
187 DEBUG(LOG_INFO, "couldn't read on raw listening socket -- ignoring");
188 usleep(500000); /* possible down interface, looping condition */
192 if (bytes < (int) (sizeof(struct iphdr) + sizeof(struct udphdr))) {
193 DEBUG(LOG_INFO, "message too short, ignoring");
197 if (bytes < ntohs(packet.ip.tot_len)) {
198 DEBUG(LOG_INFO, "Truncated packet");
202 /* ignore any extra garbage bytes */
203 bytes = ntohs(packet.ip.tot_len);
205 /* Make sure its the right packet for us, and that it passes sanity checks */
206 if (packet.ip.protocol != IPPROTO_UDP || packet.ip.version != IPVERSION ||
207 packet.ip.ihl != sizeof(packet.ip) >> 2 || packet.udp.dest != htons(CLIENT_PORT) ||
208 bytes > (int) sizeof(struct udp_dhcp_packet) ||
209 ntohs(packet.udp.len) != (short) (bytes - sizeof(packet.ip))) {
210 DEBUG(LOG_INFO, "unrelated/bogus packet");
214 /* check IP checksum */
215 check = packet.ip.check;
217 if (check != checksum(&(packet.ip), sizeof(packet.ip))) {
218 DEBUG(LOG_INFO, "bad IP header checksum, ignoring");
222 /* verify the UDP checksum by replacing the header with a psuedo header */
223 source = packet.ip.saddr;
224 dest = packet.ip.daddr;
225 check = packet.udp.check;
226 packet.udp.check = 0;
227 memset(&packet.ip, 0, sizeof(packet.ip));
229 packet.ip.protocol = IPPROTO_UDP;
230 packet.ip.saddr = source;
231 packet.ip.daddr = dest;
232 packet.ip.tot_len = packet.udp.len; /* cheat on the psuedo-header */
233 if (check && check != checksum(&packet, bytes)) {
234 DEBUG(LOG_ERR, "packet with bad UDP checksum received, ignoring");
238 memcpy(payload, &(packet.data), bytes - (sizeof(packet.ip) + sizeof(packet.udp)));
240 if (ntohl(payload->cookie) != DHCP_MAGIC) {
241 LOG(LOG_ERR, "received bogus message (bad magic) -- ignoring");
244 DEBUG(LOG_INFO, "oooooh!!! got some!");
245 return bytes - (sizeof(packet.ip) + sizeof(packet.udp));