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