1 /*
2 * dhcpcd - DHCP client daemon
3 * Copyright (c) 2006-2008 Roy Marples <roy@marples.name>
4 * All rights reserved
5
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
8 * are met:
9 * 1. Redistributions of source code must retain the above copyright
10 * notice, this list of conditions and the following disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 * notice, this list of conditions and the following disclaimer in the
13 * documentation and/or other materials provided with the distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
16 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
17 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
18 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
19 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
20 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
21 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
22 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
23 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
24 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
25 * SUCH DAMAGE.
26 */
27
28 #include <errno.h>
29 #include <signal.h>
30 #include <stdlib.h>
31 #include <string.h>
32 #include <syslog.h>
33 #include <unistd.h>
34
35 #include "arp.h"
36 #include "bind.h"
37 #include "common.h"
38 #include "dhcpcd.h"
39 #include "eloop.h"
40 #include "if-options.h"
41 #include "ipv4ll.h"
42 #include "net.h"
43
44 #define ARP_LEN \
45 (sizeof(struct arphdr) + (2 * sizeof(uint32_t)) + (2 * HWADDR_LEN))
46
47 static int
send_arp(const struct interface * iface,int op,in_addr_t sip,in_addr_t tip)48 send_arp(const struct interface *iface, int op, in_addr_t sip, in_addr_t tip)
49 {
50 uint8_t arp_buffer[ARP_LEN];
51 struct arphdr ar;
52 size_t len;
53 uint8_t *p;
54 int retval;
55
56 ar.ar_hrd = htons(iface->family);
57 ar.ar_pro = htons(ETHERTYPE_IP);
58 ar.ar_hln = iface->hwlen;
59 ar.ar_pln = sizeof(sip);
60 ar.ar_op = htons(op);
61 memcpy(arp_buffer, &ar, sizeof(ar));
62 p = arp_buffer + sizeof(ar);
63 memcpy(p, iface->hwaddr, iface->hwlen);
64 p += iface->hwlen;
65 memcpy(p, &sip, sizeof(sip));
66 p += sizeof(sip);
67 /* ARP requests should ignore this */
68 retval = iface->hwlen;
69 while (retval--)
70 *p++ = '\0';
71 memcpy(p, &tip, sizeof(tip));
72 p += sizeof(tip);
73 len = p - arp_buffer;
74 retval = send_raw_packet(iface, ETHERTYPE_ARP, arp_buffer, len);
75 return retval;
76 }
77
78 static void
handle_arp_failure(struct interface * iface)79 handle_arp_failure(struct interface *iface)
80 {
81
82 /* If we failed without a magic cookie then we need to try
83 * and defend our IPv4LL address. */
84 if ((iface->state->offer != NULL &&
85 iface->state->offer->cookie != htonl(MAGIC_COOKIE)) ||
86 (iface->state->new != NULL &&
87 iface->state->new->cookie != htonl(MAGIC_COOKIE)))
88 {
89 handle_ipv4ll_failure(iface);
90 return;
91 }
92
93 unlink(iface->leasefile);
94 if (!iface->state->lease.frominfo)
95 send_decline(iface);
96 close_sockets(iface);
97 delete_timeout(NULL, iface);
98 if (iface->state->lease.frominfo)
99 start_interface(iface);
100 else
101 add_timeout_sec(DHCP_ARP_FAIL, start_interface, iface);
102 }
103
104 static void
handle_arp_packet(void * arg)105 handle_arp_packet(void *arg)
106 {
107 struct interface *iface = arg;
108 uint8_t arp_buffer[ARP_LEN];
109 struct arphdr ar;
110 uint32_t reply_s;
111 uint32_t reply_t;
112 uint8_t *hw_s, *hw_t;
113 ssize_t bytes;
114 struct if_state *state = iface->state;
115 struct if_options *opts = state->options;
116 const char *hwaddr;
117 struct in_addr ina;
118
119 state->fail.s_addr = 0;
120 for(;;) {
121 bytes = get_raw_packet(iface, ETHERTYPE_ARP,
122 arp_buffer, sizeof(arp_buffer));
123 if (bytes == 0 || bytes == -1)
124 return;
125 /* We must have a full ARP header */
126 if ((size_t)bytes < sizeof(ar))
127 continue;
128 memcpy(&ar, arp_buffer, sizeof(ar));
129 /* Protocol must be IP. */
130 if (ar.ar_pro != htons(ETHERTYPE_IP))
131 continue;
132 if (ar.ar_pln != sizeof(reply_s))
133 continue;
134 /* Only these types are recognised */
135 if (ar.ar_op != htons(ARPOP_REPLY) &&
136 ar.ar_op != htons(ARPOP_REQUEST))
137 continue;
138
139 /* Get pointers to the hardware addreses */
140 hw_s = arp_buffer + sizeof(ar);
141 hw_t = hw_s + ar.ar_hln + ar.ar_pln;
142 /* Ensure we got all the data */
143 if ((hw_t + ar.ar_hln + ar.ar_pln) - arp_buffer > bytes)
144 continue;
145 /* Ignore messages from ourself */
146 if (ar.ar_hln == iface->hwlen &&
147 memcmp(hw_s, iface->hwaddr, iface->hwlen) == 0)
148 continue;
149 /* Copy out the IP addresses */
150 memcpy(&reply_s, hw_s + ar.ar_hln, ar.ar_pln);
151 memcpy(&reply_t, hw_t + ar.ar_hln, ar.ar_pln);
152
153 /* Check for arping */
154 if (state->arping_index &&
155 state->arping_index <= opts->arping_len &&
156 (reply_s == opts->arping[state->arping_index - 1] ||
157 (reply_s == 0 &&
158 reply_t == opts->arping[state->arping_index - 1])))
159 {
160 ina.s_addr = reply_s;
161 hwaddr = hwaddr_ntoa((unsigned char *)hw_s,
162 (size_t)ar.ar_hln);
163 syslog(LOG_INFO,
164 "%s: found %s on hardware address %s",
165 iface->name, inet_ntoa(ina), hwaddr);
166 if (select_profile(iface, hwaddr) == -1 &&
167 errno == ENOENT)
168 select_profile(iface, inet_ntoa(ina));
169 close_sockets(iface);
170 delete_timeout(NULL, iface);
171 start_interface(iface);
172 return;
173 }
174
175 /* Check for conflict */
176 if (state->offer &&
177 (reply_s == state->offer->yiaddr ||
178 (reply_s == 0 && reply_t == state->offer->yiaddr)))
179 state->fail.s_addr = state->offer->yiaddr;
180
181 /* Handle IPv4LL conflicts */
182 if (IN_LINKLOCAL(htonl(iface->addr.s_addr)) &&
183 (reply_s == iface->addr.s_addr ||
184 (reply_s == 0 && reply_t == iface->addr.s_addr)))
185 state->fail.s_addr = iface->addr.s_addr;
186
187 if (state->fail.s_addr) {
188 syslog(LOG_ERR, "%s: hardware address %s claims %s",
189 iface->name,
190 hwaddr_ntoa((unsigned char *)hw_s,
191 (size_t)ar.ar_hln),
192 inet_ntoa(state->fail));
193 errno = EEXIST;
194 handle_arp_failure(iface);
195 return;
196 }
197 }
198 }
199
200 void
send_arp_announce(void * arg)201 send_arp_announce(void *arg)
202 {
203 struct interface *iface = arg;
204 struct if_state *state = iface->state;
205 struct timeval tv;
206
207 if (iface->arp_fd == -1) {
208 open_socket(iface, ETHERTYPE_ARP);
209 add_event(iface->arp_fd, handle_arp_packet, iface);
210 }
211 if (++state->claims < ANNOUNCE_NUM)
212 syslog(LOG_DEBUG,
213 "%s: sending ARP announce (%d of %d), "
214 "next in %d.00 seconds",
215 iface->name, state->claims, ANNOUNCE_NUM, ANNOUNCE_WAIT);
216 else
217 syslog(LOG_DEBUG,
218 "%s: sending ARP announce (%d of %d)",
219 iface->name, state->claims, ANNOUNCE_NUM);
220 if (send_arp(iface, ARPOP_REQUEST,
221 state->new->yiaddr, state->new->yiaddr) == -1)
222 syslog(LOG_ERR, "send_arp: %m");
223 if (state->claims < ANNOUNCE_NUM) {
224 add_timeout_sec(ANNOUNCE_WAIT, send_arp_announce, iface);
225 return;
226 }
227 if (state->new->cookie != htonl(MAGIC_COOKIE)) {
228 /* We should pretend to be at the end
229 * of the DHCP negotation cycle unless we rebooted */
230 if (state->interval != 0)
231 state->interval = 64;
232 state->probes = 0;
233 state->claims = 0;
234 tv.tv_sec = state->interval - DHCP_RAND_MIN;
235 tv.tv_usec = arc4random() % (DHCP_RAND_MAX_U - DHCP_RAND_MIN_U);
236 timernorm(&tv);
237 add_timeout_tv(&tv, start_discover, iface);
238 } else {
239 delete_event(iface->arp_fd);
240 close(iface->arp_fd);
241 iface->arp_fd = -1;
242 }
243 }
244
245 void
send_arp_probe(void * arg)246 send_arp_probe(void *arg)
247 {
248 struct interface *iface = arg;
249 struct if_state *state = iface->state;
250 struct in_addr addr;
251 struct timeval tv;
252 int arping = 0;
253
254 if (state->arping_index < state->options->arping_len) {
255 addr.s_addr = state->options->arping[state->arping_index];
256 arping = 1;
257 } else if (state->offer) {
258 if (state->offer->yiaddr)
259 addr.s_addr = state->offer->yiaddr;
260 else
261 addr.s_addr = state->offer->ciaddr;
262 } else
263 addr.s_addr = iface->addr.s_addr;
264
265 if (iface->arp_fd == -1) {
266 open_socket(iface, ETHERTYPE_ARP);
267 add_event(iface->arp_fd, handle_arp_packet, iface);
268 }
269 if (state->probes == 0) {
270 if (arping)
271 syslog(LOG_INFO, "%s: searching for %s",
272 iface->name, inet_ntoa(addr));
273 else
274 syslog(LOG_INFO, "%s: checking for %s",
275 iface->name, inet_ntoa(addr));
276 }
277 if (++state->probes < PROBE_NUM) {
278 tv.tv_sec = PROBE_MIN;
279 tv.tv_usec = arc4random() % (PROBE_MAX_U - PROBE_MIN_U);
280 timernorm(&tv);
281 add_timeout_tv(&tv, send_arp_probe, iface);
282 } else {
283 tv.tv_sec = ANNOUNCE_WAIT;
284 tv.tv_usec = 0;
285 if (arping) {
286 state->probes = 0;
287 if (++state->arping_index < state->options->arping_len)
288 add_timeout_tv(&tv, send_arp_probe, iface);
289 else
290 add_timeout_tv(&tv, start_interface, iface);
291 } else
292 add_timeout_tv(&tv, bind_interface, iface);
293 }
294 syslog(LOG_DEBUG,
295 "%s: sending ARP probe (%d of %d), next in %0.2f seconds",
296 iface->name, state->probes ? state->probes : PROBE_NUM, PROBE_NUM,
297 timeval_to_double(&tv));
298 if (send_arp(iface, ARPOP_REQUEST, 0, addr.s_addr) == -1)
299 syslog(LOG_ERR, "send_arp: %m");
300 }
301
302 void
start_arping(struct interface * iface)303 start_arping(struct interface *iface)
304 {
305 iface->state->probes = 0;
306 iface->state->arping_index = 0;
307 send_arp_probe(iface);
308 }
309