blob: 86faec925d446c6896a4978f60d81daf07460d4d [file] [log] [blame]
Russ Dill61fb4892002-10-14 21:41:28 +00001/* clientpacket.c
2 *
3 * Packet generation and dispatching functions for the DHCP client.
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 <string.h>
23#include <sys/socket.h>
24#include <features.h>
25#if __GLIBC__ >=2 && __GLIBC_MINOR >= 1
26#include <netpacket/packet.h>
27#include <net/ethernet.h>
28#else
29#include <asm/types.h>
30#include <linux/if_packet.h>
31#include <linux/if_ether.h>
32#endif
33#include <stdlib.h>
34#include <time.h>
35#include <unistd.h>
36#include <netinet/in.h>
37#include <arpa/inet.h>
Russ Dillf5ecd432002-10-31 19:21:27 +000038#include <errno.h>
39#include <sys/types.h>
40#include <sys/stat.h>
41#include <fcntl.h>
Russ Dill61fb4892002-10-14 21:41:28 +000042
43
44#include "dhcpd.h"
45#include "packet.h"
46#include "options.h"
47#include "dhcpc.h"
48#include "debug.h"
49
50
51/* Create a random xid */
52unsigned long random_xid(void)
53{
54 static int initialized;
55 if (!initialized) {
Russ Dillf5ecd432002-10-31 19:21:27 +000056 int fd;
57 unsigned long seed;
58
59 fd = open("/dev/urandom", 0);
60 if (fd < 0 || read(fd, &seed, sizeof(seed)) < 0) {
61 LOG(LOG_WARNING, "Could not load seed from /dev/urandom: %s",
62 strerror(errno));
63 seed = time(0);
64 }
65 if (fd >= 0) close(fd);
66 srand(seed);
Russ Dill61fb4892002-10-14 21:41:28 +000067 initialized++;
68 }
69 return rand();
70}
71
72
73/* initialize a packet with the proper defaults */
74static void init_packet(struct dhcpMessage *packet, char type)
75{
76 struct vendor {
77 char vendor, length;
78 char str[sizeof("udhcp "VERSION)];
79 } vendor_id = { DHCP_VENDOR, sizeof("udhcp "VERSION) - 1, "udhcp "VERSION};
80
81 init_header(packet, type);
82 memcpy(packet->chaddr, client_config.arp, 6);
83 add_option_string(packet->options, client_config.clientid);
84 if (client_config.hostname) add_option_string(packet->options, client_config.hostname);
85 add_option_string(packet->options, (unsigned char *) &vendor_id);
86}
87
88
89/* Add a paramater request list for stubborn DHCP servers. Pull the data
90 * from the struct in options.c. Don't do bounds checking here because it
91 * goes towards the head of the packet. */
92static void add_requests(struct dhcpMessage *packet)
93{
94 int end = end_option(packet->options);
95 int i, len = 0;
96
97 packet->options[end + OPT_CODE] = DHCP_PARAM_REQ;
98 for (i = 0; options[i].code; i++)
99 if (options[i].flags & OPTION_REQ)
100 packet->options[end + OPT_DATA + len++] = options[i].code;
101 packet->options[end + OPT_LEN] = len;
102 packet->options[end + OPT_DATA + len] = DHCP_END;
103
104}
105
106
107/* Broadcast a DHCP discover packet to the network, with an optionally requested IP */
108int send_discover(unsigned long xid, unsigned long requested)
109{
110 struct dhcpMessage packet;
111
112 init_packet(&packet, DHCPDISCOVER);
113 packet.xid = xid;
114 if (requested)
115 add_simple_option(packet.options, DHCP_REQUESTED_IP, requested);
116
117 add_requests(&packet);
118 LOG(LOG_DEBUG, "Sending discover...");
119 return raw_packet(&packet, INADDR_ANY, CLIENT_PORT, INADDR_BROADCAST,
120 SERVER_PORT, MAC_BCAST_ADDR, client_config.ifindex);
121}
122
123
124/* Broadcasts a DHCP request message */
125int send_selecting(unsigned long xid, unsigned long server, unsigned long requested)
126{
127 struct dhcpMessage packet;
128 struct in_addr addr;
129
130 init_packet(&packet, DHCPREQUEST);
131 packet.xid = xid;
132
133 add_simple_option(packet.options, DHCP_REQUESTED_IP, requested);
134 add_simple_option(packet.options, DHCP_SERVER_ID, server);
135
136 add_requests(&packet);
137 addr.s_addr = requested;
138 LOG(LOG_DEBUG, "Sending select for %s...", inet_ntoa(addr));
139 return raw_packet(&packet, INADDR_ANY, CLIENT_PORT, INADDR_BROADCAST,
140 SERVER_PORT, MAC_BCAST_ADDR, client_config.ifindex);
141}
142
143
144/* Unicasts or broadcasts a DHCP renew message */
145int send_renew(unsigned long xid, unsigned long server, unsigned long ciaddr)
146{
147 struct dhcpMessage packet;
148 int ret = 0;
149
150 init_packet(&packet, DHCPREQUEST);
151 packet.xid = xid;
152 packet.ciaddr = ciaddr;
153
154 add_requests(&packet);
155 LOG(LOG_DEBUG, "Sending renew...");
156 if (server)
157 ret = kernel_packet(&packet, ciaddr, CLIENT_PORT, server, SERVER_PORT);
158 else ret = raw_packet(&packet, INADDR_ANY, CLIENT_PORT, INADDR_BROADCAST,
159 SERVER_PORT, MAC_BCAST_ADDR, client_config.ifindex);
160 return ret;
161}
162
163
164/* Unicasts a DHCP release message */
165int send_release(unsigned long server, unsigned long ciaddr)
166{
167 struct dhcpMessage packet;
168
169 init_packet(&packet, DHCPRELEASE);
170 packet.xid = random_xid();
171 packet.ciaddr = ciaddr;
172
173 add_simple_option(packet.options, DHCP_REQUESTED_IP, ciaddr);
174 add_simple_option(packet.options, DHCP_SERVER_ID, server);
175
176 LOG(LOG_DEBUG, "Sending release...");
177 return kernel_packet(&packet, ciaddr, CLIENT_PORT, server, SERVER_PORT);
178}
179
180
181/* return -1 on errors that are fatal for the socket, -2 for those that aren't */
182int get_raw_packet(struct dhcpMessage *payload, int fd)
183{
184 int bytes;
185 struct udp_dhcp_packet packet;
186 u_int32_t source, dest;
187 u_int16_t check;
188
189 memset(&packet, 0, sizeof(struct udp_dhcp_packet));
190 bytes = read(fd, &packet, sizeof(struct udp_dhcp_packet));
191 if (bytes < 0) {
192 DEBUG(LOG_INFO, "couldn't read on raw listening socket -- ignoring");
193 usleep(500000); /* possible down interface, looping condition */
194 return -1;
195 }
196
197 if (bytes < (int) (sizeof(struct iphdr) + sizeof(struct udphdr))) {
198 DEBUG(LOG_INFO, "message too short, ignoring");
199 return -2;
200 }
201
202 if (bytes < ntohs(packet.ip.tot_len)) {
203 DEBUG(LOG_INFO, "Truncated packet");
204 return -2;
205 }
206
207 /* ignore any extra garbage bytes */
208 bytes = ntohs(packet.ip.tot_len);
209
210 /* Make sure its the right packet for us, and that it passes sanity checks */
211 if (packet.ip.protocol != IPPROTO_UDP || packet.ip.version != IPVERSION ||
212 packet.ip.ihl != sizeof(packet.ip) >> 2 || packet.udp.dest != htons(CLIENT_PORT) ||
213 bytes > (int) sizeof(struct udp_dhcp_packet) ||
214 ntohs(packet.udp.len) != (short) (bytes - sizeof(packet.ip))) {
215 DEBUG(LOG_INFO, "unrelated/bogus packet");
216 return -2;
217 }
218
219 /* check IP checksum */
220 check = packet.ip.check;
221 packet.ip.check = 0;
222 if (check != checksum(&(packet.ip), sizeof(packet.ip))) {
223 DEBUG(LOG_INFO, "bad IP header checksum, ignoring");
224 return -1;
225 }
226
227 /* verify the UDP checksum by replacing the header with a psuedo header */
228 source = packet.ip.saddr;
229 dest = packet.ip.daddr;
230 check = packet.udp.check;
231 packet.udp.check = 0;
232 memset(&packet.ip, 0, sizeof(packet.ip));
233
234 packet.ip.protocol = IPPROTO_UDP;
235 packet.ip.saddr = source;
236 packet.ip.daddr = dest;
237 packet.ip.tot_len = packet.udp.len; /* cheat on the psuedo-header */
238 if (check && check != checksum(&packet, bytes)) {
239 DEBUG(LOG_ERR, "packet with bad UDP checksum received, ignoring");
240 return -2;
241 }
242
243 memcpy(payload, &(packet.data), bytes - (sizeof(packet.ip) + sizeof(packet.udp)));
244
245 if (ntohl(payload->cookie) != DHCP_MAGIC) {
246 LOG(LOG_ERR, "received bogus message (bad magic) -- ignoring");
247 return -2;
248 }
249 DEBUG(LOG_INFO, "oooooh!!! got some!");
250 return bytes - (sizeof(packet.ip) + sizeof(packet.udp));
251
252}
253