1 /*
2 * RFC3927 ZeroConf IPv4 Link-Local addressing
3 * (see <http://www.zeroconf.org/>)
4 *
5 * Copied from BusyBox - networking/zcip.c
6 *
7 * Copyright (C) 2003 by Arthur van Hoff (avh@strangeberry.com)
8 * Copyright (C) 2004 by David Brownell
9 * Copyright (C) 2010 by Joe Hershberger
10 *
11 * Licensed under the GPL v2 or later
12 */
13
14 #include <common.h>
15 #include <env.h>
16 #include <log.h>
17 #include <net.h>
18 #include <rand.h>
19 #include "arp.h"
20 #include "net_rand.h"
21
22 /* We don't need more than 32 bits of the counter */
23 #define MONOTONIC_MS() ((unsigned)get_timer(0) * (1000 / CONFIG_SYS_HZ))
24
25 enum {
26 /* 169.254.0.0 */
27 LINKLOCAL_ADDR = 0xa9fe0000,
28
29 IN_CLASSB_NET = 0xffff0000,
30 IN_CLASSB_HOST = 0x0000ffff,
31
32 /* protocol timeout parameters, specified in seconds */
33 PROBE_WAIT = 1,
34 PROBE_MIN = 1,
35 PROBE_MAX = 2,
36 PROBE_NUM = 3,
37 MAX_CONFLICTS = 10,
38 RATE_LIMIT_INTERVAL = 60,
39 ANNOUNCE_WAIT = 2,
40 ANNOUNCE_NUM = 2,
41 ANNOUNCE_INTERVAL = 2,
42 DEFEND_INTERVAL = 10
43 };
44
45 /* States during the configuration process. */
46 static enum ll_state_t {
47 PROBE = 0,
48 RATE_LIMIT_PROBE,
49 ANNOUNCE,
50 MONITOR,
51 DEFEND,
52 DISABLED
53 } state = DISABLED;
54
55 static struct in_addr ip;
56 static int timeout_ms = -1;
57 static unsigned deadline_ms;
58 static unsigned conflicts;
59 static unsigned nprobes;
60 static unsigned nclaims;
61 static int ready;
62 static unsigned int seed;
63
64 static void link_local_timeout(void);
65
66 /**
67 * Pick a random link local IP address on 169.254/16, except that
68 * the first and last 256 addresses are reserved.
69 */
pick(void)70 static struct in_addr pick(void)
71 {
72 unsigned tmp;
73 struct in_addr ip;
74
75 do {
76 tmp = rand_r(&seed) & IN_CLASSB_HOST;
77 } while (tmp > (IN_CLASSB_HOST - 0x0200));
78 ip.s_addr = htonl((LINKLOCAL_ADDR + 0x0100) + tmp);
79 return ip;
80 }
81
82 /**
83 * Return milliseconds of random delay, up to "secs" seconds.
84 */
random_delay_ms(unsigned secs)85 static inline unsigned random_delay_ms(unsigned secs)
86 {
87 return rand_r(&seed) % (secs * 1000);
88 }
89
configure_wait(void)90 static void configure_wait(void)
91 {
92 if (timeout_ms == -1)
93 return;
94
95 /* poll, being ready to adjust current timeout */
96 if (!timeout_ms)
97 timeout_ms = random_delay_ms(PROBE_WAIT);
98
99 /* set deadline_ms to the point in time when we timeout */
100 deadline_ms = MONOTONIC_MS() + timeout_ms;
101
102 debug_cond(DEBUG_DEV_PKT, "...wait %d %s nprobes=%u, nclaims=%u\n",
103 timeout_ms, eth_get_name(), nprobes, nclaims);
104
105 net_set_timeout_handler(timeout_ms, link_local_timeout);
106 }
107
link_local_start(void)108 void link_local_start(void)
109 {
110 ip = env_get_ip("llipaddr");
111 if (ip.s_addr != 0 &&
112 (ntohl(ip.s_addr) & IN_CLASSB_NET) != LINKLOCAL_ADDR) {
113 puts("invalid link address");
114 net_set_state(NETLOOP_FAIL);
115 return;
116 }
117 net_netmask.s_addr = htonl(IN_CLASSB_NET);
118
119 seed = seed_mac();
120 if (ip.s_addr == 0)
121 ip = pick();
122
123 state = PROBE;
124 timeout_ms = 0;
125 conflicts = 0;
126 nprobes = 0;
127 nclaims = 0;
128 ready = 0;
129
130 configure_wait();
131 }
132
link_local_timeout(void)133 static void link_local_timeout(void)
134 {
135 switch (state) {
136 case PROBE:
137 /* timeouts in the PROBE state mean no conflicting ARP packets
138 have been received, so we can progress through the states */
139 if (nprobes < PROBE_NUM) {
140 struct in_addr zero_ip = {.s_addr = 0};
141
142 nprobes++;
143 debug_cond(DEBUG_LL_STATE, "probe/%u %s@%pI4\n",
144 nprobes, eth_get_name(), &ip);
145 arp_raw_request(zero_ip, net_null_ethaddr, ip);
146 timeout_ms = PROBE_MIN * 1000;
147 timeout_ms += random_delay_ms(PROBE_MAX - PROBE_MIN);
148 } else {
149 /* Switch to announce state */
150 state = ANNOUNCE;
151 nclaims = 0;
152 debug_cond(DEBUG_LL_STATE, "announce/%u %s@%pI4\n",
153 nclaims, eth_get_name(), &ip);
154 arp_raw_request(ip, net_ethaddr, ip);
155 timeout_ms = ANNOUNCE_INTERVAL * 1000;
156 }
157 break;
158 case RATE_LIMIT_PROBE:
159 /* timeouts in the RATE_LIMIT_PROBE state mean no conflicting
160 ARP packets have been received, so we can move immediately
161 to the announce state */
162 state = ANNOUNCE;
163 nclaims = 0;
164 debug_cond(DEBUG_LL_STATE, "announce/%u %s@%pI4\n",
165 nclaims, eth_get_name(), &ip);
166 arp_raw_request(ip, net_ethaddr, ip);
167 timeout_ms = ANNOUNCE_INTERVAL * 1000;
168 break;
169 case ANNOUNCE:
170 /* timeouts in the ANNOUNCE state mean no conflicting ARP
171 packets have been received, so we can progress through
172 the states */
173 if (nclaims < ANNOUNCE_NUM) {
174 nclaims++;
175 debug_cond(DEBUG_LL_STATE, "announce/%u %s@%pI4\n",
176 nclaims, eth_get_name(), &ip);
177 arp_raw_request(ip, net_ethaddr, ip);
178 timeout_ms = ANNOUNCE_INTERVAL * 1000;
179 } else {
180 /* Switch to monitor state */
181 state = MONITOR;
182 printf("Successfully assigned %pI4\n", &ip);
183 net_copy_ip(&net_ip, &ip);
184 ready = 1;
185 conflicts = 0;
186 timeout_ms = -1;
187 /* Never timeout in the monitor state */
188 net_set_timeout_handler(0, NULL);
189
190 /* NOTE: all other exit paths should deconfig ... */
191 net_set_state(NETLOOP_SUCCESS);
192 return;
193 }
194 break;
195 case DEFEND:
196 /* We won! No ARP replies, so just go back to monitor */
197 state = MONITOR;
198 timeout_ms = -1;
199 conflicts = 0;
200 break;
201 default:
202 /* Invalid, should never happen. Restart the whole protocol */
203 state = PROBE;
204 ip = pick();
205 timeout_ms = 0;
206 nprobes = 0;
207 nclaims = 0;
208 break;
209 }
210 configure_wait();
211 }
212
link_local_receive_arp(struct arp_hdr * arp,int len)213 void link_local_receive_arp(struct arp_hdr *arp, int len)
214 {
215 int source_ip_conflict;
216 int target_ip_conflict;
217 struct in_addr null_ip = {.s_addr = 0};
218
219 if (state == DISABLED)
220 return;
221
222 /* We need to adjust the timeout in case we didn't receive a
223 conflicting packet. */
224 if (timeout_ms > 0) {
225 unsigned diff = deadline_ms - MONOTONIC_MS();
226 if ((int)(diff) < 0) {
227 /* Current time is greater than the expected timeout
228 time. This should never happen */
229 debug_cond(DEBUG_LL_STATE,
230 "missed an expected timeout\n");
231 timeout_ms = 0;
232 } else {
233 debug_cond(DEBUG_INT_STATE, "adjusting timeout\n");
234 timeout_ms = diff | 1; /* never 0 */
235 }
236 }
237 #if 0
238 /* XXX Don't bother with ethernet link just yet */
239 if ((fds[0].revents & POLLIN) == 0) {
240 if (fds[0].revents & POLLERR) {
241 /*
242 * FIXME: links routinely go down;
243 */
244 bb_error_msg("iface %s is down", eth_get_name());
245 if (ready)
246 run(argv, "deconfig", &ip);
247 return EXIT_FAILURE;
248 }
249 continue;
250 }
251 #endif
252
253 debug_cond(DEBUG_INT_STATE, "%s recv arp type=%d, op=%d,\n",
254 eth_get_name(), ntohs(arp->ar_pro),
255 ntohs(arp->ar_op));
256 debug_cond(DEBUG_INT_STATE, "\tsource=%pM %pI4\n",
257 &arp->ar_sha,
258 &arp->ar_spa);
259 debug_cond(DEBUG_INT_STATE, "\ttarget=%pM %pI4\n",
260 &arp->ar_tha,
261 &arp->ar_tpa);
262
263 if (arp->ar_op != htons(ARPOP_REQUEST) &&
264 arp->ar_op != htons(ARPOP_REPLY)) {
265 configure_wait();
266 return;
267 }
268
269 source_ip_conflict = 0;
270 target_ip_conflict = 0;
271
272 if (memcmp(&arp->ar_spa, &ip, ARP_PLEN) == 0 &&
273 memcmp(&arp->ar_sha, net_ethaddr, ARP_HLEN) != 0)
274 source_ip_conflict = 1;
275
276 /*
277 * According to RFC 3927, section 2.2.1:
278 * Check if packet is an ARP probe by checking for a null source IP
279 * then check that target IP is equal to ours and source hw addr
280 * is not equal to ours. This condition should cause a conflict only
281 * during probe.
282 */
283 if (arp->ar_op == htons(ARPOP_REQUEST) &&
284 memcmp(&arp->ar_spa, &null_ip, ARP_PLEN) == 0 &&
285 memcmp(&arp->ar_tpa, &ip, ARP_PLEN) == 0 &&
286 memcmp(&arp->ar_sha, net_ethaddr, ARP_HLEN) != 0) {
287 target_ip_conflict = 1;
288 }
289
290 debug_cond(DEBUG_NET_PKT,
291 "state = %d, source ip conflict = %d, target ip conflict = "
292 "%d\n", state, source_ip_conflict, target_ip_conflict);
293 switch (state) {
294 case PROBE:
295 case ANNOUNCE:
296 /* When probing or announcing, check for source IP conflicts
297 and other hosts doing ARP probes (target IP conflicts). */
298 if (source_ip_conflict || target_ip_conflict) {
299 conflicts++;
300 state = PROBE;
301 if (conflicts >= MAX_CONFLICTS) {
302 debug("%s ratelimit\n", eth_get_name());
303 timeout_ms = RATE_LIMIT_INTERVAL * 1000;
304 state = RATE_LIMIT_PROBE;
305 }
306
307 /* restart the whole protocol */
308 ip = pick();
309 timeout_ms = 0;
310 nprobes = 0;
311 nclaims = 0;
312 }
313 break;
314 case MONITOR:
315 /* If a conflict, we try to defend with a single ARP probe */
316 if (source_ip_conflict) {
317 debug("monitor conflict -- defending\n");
318 state = DEFEND;
319 timeout_ms = DEFEND_INTERVAL * 1000;
320 arp_raw_request(ip, net_ethaddr, ip);
321 }
322 break;
323 case DEFEND:
324 /* Well, we tried. Start over (on conflict) */
325 if (source_ip_conflict) {
326 state = PROBE;
327 debug("defend conflict -- starting over\n");
328 ready = 0;
329 net_ip.s_addr = 0;
330
331 /* restart the whole protocol */
332 ip = pick();
333 timeout_ms = 0;
334 nprobes = 0;
335 nclaims = 0;
336 }
337 break;
338 default:
339 /* Invalid, should never happen. Restart the whole protocol */
340 debug("invalid state -- starting over\n");
341 state = PROBE;
342 ip = pick();
343 timeout_ms = 0;
344 nprobes = 0;
345 nclaims = 0;
346 break;
347 }
348 configure_wait();
349 }
350