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-rw-r--r--networking/udhcp/clientpacket.c239
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diff --git a/networking/udhcp/clientpacket.c b/networking/udhcp/clientpacket.c
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1/* 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>
38
39
40#include "dhcpd.h"
41#include "packet.h"
42#include "options.h"
43#include "dhcpc.h"
44#include "debug.h"
45
46
47/* Create a random xid */
48unsigned long random_xid(void)
49{
50 static int initialized;
51 if (!initialized) {
52 srand(time(0));
53 initialized++;
54 }
55 return rand();
56}
57
58
59/* initialize a packet with the proper defaults */
60static void init_packet(struct dhcpMessage *packet, char type)
61{
62 struct vendor {
63 char vendor, length;
64 char str[sizeof("udhcp "VERSION)];
65 } vendor_id = { DHCP_VENDOR, sizeof("udhcp "VERSION) - 1, "udhcp "VERSION};
66
67 init_header(packet, type);
68 memcpy(packet->chaddr, client_config.arp, 6);
69 add_option_string(packet->options, client_config.clientid);
70 if (client_config.hostname) add_option_string(packet->options, client_config.hostname);
71 add_option_string(packet->options, (unsigned char *) &vendor_id);
72}
73
74
75/* Add a paramater request list for stubborn DHCP servers. Pull the data
76 * from the struct in options.c. Don't do bounds checking here because it
77 * goes towards the head of the packet. */
78static void add_requests(struct dhcpMessage *packet)
79{
80 int end = end_option(packet->options);
81 int i, len = 0;
82
83 packet->options[end + OPT_CODE] = DHCP_PARAM_REQ;
84 for (i = 0; options[i].code; i++)
85 if (options[i].flags & OPTION_REQ)
86 packet->options[end + OPT_DATA + len++] = options[i].code;
87 packet->options[end + OPT_LEN] = len;
88 packet->options[end + OPT_DATA + len] = DHCP_END;
89
90}
91
92
93/* Broadcast a DHCP discover packet to the network, with an optionally requested IP */
94int send_discover(unsigned long xid, unsigned long requested)
95{
96 struct dhcpMessage packet;
97
98 init_packet(&packet, DHCPDISCOVER);
99 packet.xid = xid;
100 if (requested)
101 add_simple_option(packet.options, DHCP_REQUESTED_IP, requested);
102
103 add_requests(&packet);
104 LOG(LOG_DEBUG, "Sending discover...");
105 return raw_packet(&packet, INADDR_ANY, CLIENT_PORT, INADDR_BROADCAST,
106 SERVER_PORT, MAC_BCAST_ADDR, client_config.ifindex);
107}
108
109
110/* Broadcasts a DHCP request message */
111int send_selecting(unsigned long xid, unsigned long server, unsigned long requested)
112{
113 struct dhcpMessage packet;
114 struct in_addr addr;
115
116 init_packet(&packet, DHCPREQUEST);
117 packet.xid = xid;
118
119 add_simple_option(packet.options, DHCP_REQUESTED_IP, requested);
120 add_simple_option(packet.options, DHCP_SERVER_ID, server);
121
122 add_requests(&packet);
123 addr.s_addr = requested;
124 LOG(LOG_DEBUG, "Sending select for %s...", inet_ntoa(addr));
125 return raw_packet(&packet, INADDR_ANY, CLIENT_PORT, INADDR_BROADCAST,
126 SERVER_PORT, MAC_BCAST_ADDR, client_config.ifindex);
127}
128
129
130/* Unicasts or broadcasts a DHCP renew message */
131int send_renew(unsigned long xid, unsigned long server, unsigned long ciaddr)
132{
133 struct dhcpMessage packet;
134 int ret = 0;
135
136 init_packet(&packet, DHCPREQUEST);
137 packet.xid = xid;
138 packet.ciaddr = ciaddr;
139
140 add_requests(&packet);
141 LOG(LOG_DEBUG, "Sending renew...");
142 if (server)
143 ret = kernel_packet(&packet, ciaddr, CLIENT_PORT, server, SERVER_PORT);
144 else ret = raw_packet(&packet, INADDR_ANY, CLIENT_PORT, INADDR_BROADCAST,
145 SERVER_PORT, MAC_BCAST_ADDR, client_config.ifindex);
146 return ret;
147}
148
149
150/* Unicasts a DHCP release message */
151int send_release(unsigned long server, unsigned long ciaddr)
152{
153 struct dhcpMessage packet;
154
155 init_packet(&packet, DHCPRELEASE);
156 packet.xid = random_xid();
157 packet.ciaddr = ciaddr;
158
159 add_simple_option(packet.options, DHCP_REQUESTED_IP, ciaddr);
160 add_simple_option(packet.options, DHCP_SERVER_ID, server);
161
162 LOG(LOG_DEBUG, "Sending release...");
163 return kernel_packet(&packet, ciaddr, CLIENT_PORT, server, SERVER_PORT);
164}
165
166
167/* return -1 on errors that are fatal for the socket, -2 for those that aren't */
168int get_raw_packet(struct dhcpMessage *payload, int fd)
169{
170 int bytes;
171 struct udp_dhcp_packet packet;
172 u_int32_t source, dest;
173 u_int16_t check;
174
175 memset(&packet, 0, sizeof(struct udp_dhcp_packet));
176 bytes = read(fd, &packet, sizeof(struct udp_dhcp_packet));
177 if (bytes < 0) {
178 DEBUG(LOG_INFO, "couldn't read on raw listening socket -- ignoring");
179 usleep(500000); /* possible down interface, looping condition */
180 return -1;
181 }
182
183 if (bytes < (int) (sizeof(struct iphdr) + sizeof(struct udphdr))) {
184 DEBUG(LOG_INFO, "message too short, ignoring");
185 return -2;
186 }
187
188 if (bytes < ntohs(packet.ip.tot_len)) {
189 DEBUG(LOG_INFO, "Truncated packet");
190 return -2;
191 }
192
193 /* ignore any extra garbage bytes */
194 bytes = ntohs(packet.ip.tot_len);
195
196 /* Make sure its the right packet for us, and that it passes sanity checks */
197 if (packet.ip.protocol != IPPROTO_UDP || packet.ip.version != IPVERSION ||
198 packet.ip.ihl != sizeof(packet.ip) >> 2 || packet.udp.dest != htons(CLIENT_PORT) ||
199 bytes > (int) sizeof(struct udp_dhcp_packet) ||
200 ntohs(packet.udp.len) != (short) (bytes - sizeof(packet.ip))) {
201 DEBUG(LOG_INFO, "unrelated/bogus packet");
202 return -2;
203 }
204
205 /* check IP checksum */
206 check = packet.ip.check;
207 packet.ip.check = 0;
208 if (check != checksum(&(packet.ip), sizeof(packet.ip))) {
209 DEBUG(LOG_INFO, "bad IP header checksum, ignoring");
210 return -1;
211 }
212
213 /* verify the UDP checksum by replacing the header with a psuedo header */
214 source = packet.ip.saddr;
215 dest = packet.ip.daddr;
216 check = packet.udp.check;
217 packet.udp.check = 0;
218 memset(&packet.ip, 0, sizeof(packet.ip));
219
220 packet.ip.protocol = IPPROTO_UDP;
221 packet.ip.saddr = source;
222 packet.ip.daddr = dest;
223 packet.ip.tot_len = packet.udp.len; /* cheat on the psuedo-header */
224 if (check && check != checksum(&packet, bytes)) {
225 DEBUG(LOG_ERR, "packet with bad UDP checksum received, ignoring");
226 return -2;
227 }
228
229 memcpy(payload, &(packet.data), bytes - (sizeof(packet.ip) + sizeof(packet.udp)));
230
231 if (ntohl(payload->cookie) != DHCP_MAGIC) {
232 LOG(LOG_ERR, "received bogus message (bad magic) -- ignoring");
233 return -2;
234 }
235 DEBUG(LOG_INFO, "oooooh!!! got some!");
236 return bytes - (sizeof(packet.ip) + sizeof(packet.udp));
237
238}
239