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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 <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 | */ | |
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 | */ | |
82 | static inline unsigned random_delay_ms(unsigned secs) | |
83 | { | |
84 | return rand_r(&seed) % (secs * 1000); | |
85 | } | |
86 | ||
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 | ||
105 | void link_local_start(void) | |
106 | { | |
107 | ip = getenv_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 | ||
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 | ||
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 | } |