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