source: MondoRescue/branches/3.0/mindi-busybox/networking/zcip.c@ 2899

Last change on this file since 2899 was 2725, checked in by Bruno Cornec, 13 years ago
  • Update mindi-busybox to 1.18.3 to avoid problems with the tar command which is now failing on recent versions with busybox 1.7.3
File size: 15.0 KB
Line 
1/* vi: set sw=4 ts=4: */
2/*
3 * RFC3927 ZeroConf IPv4 Link-Local addressing
4 * (see <http://www.zeroconf.org/>)
5 *
6 * Copyright (C) 2003 by Arthur van Hoff (avh@strangeberry.com)
7 * Copyright (C) 2004 by David Brownell
8 *
9 * Licensed under GPLv2 or later, see file LICENSE in this source tree.
10 */
11
12/*
13 * ZCIP just manages the 169.254.*.* addresses. That network is not
14 * routed at the IP level, though various proxies or bridges can
15 * certainly be used. Its naming is built over multicast DNS.
16 */
17
18//#define DEBUG
19
20// TODO:
21// - more real-world usage/testing, especially daemon mode
22// - kernel packet filters to reduce scheduling noise
23// - avoid silent script failures, especially under load...
24// - link status monitoring (restart on link-up; stop on link-down)
25
26#include <netinet/ether.h>
27#include <net/ethernet.h>
28#include <net/if.h>
29#include <net/if_arp.h>
30#include <linux/if_packet.h>
31#include <linux/sockios.h>
32
33#include "libbb.h"
34#include <syslog.h>
35
36/* We don't need more than 32 bits of the counter */
37#define MONOTONIC_US() ((unsigned)monotonic_us())
38
39struct arp_packet {
40 struct ether_header eth;
41 struct ether_arp arp;
42} PACKED;
43
44enum {
45/* 169.254.0.0 */
46 LINKLOCAL_ADDR = 0xa9fe0000,
47
48/* protocol timeout parameters, specified in seconds */
49 PROBE_WAIT = 1,
50 PROBE_MIN = 1,
51 PROBE_MAX = 2,
52 PROBE_NUM = 3,
53 MAX_CONFLICTS = 10,
54 RATE_LIMIT_INTERVAL = 60,
55 ANNOUNCE_WAIT = 2,
56 ANNOUNCE_NUM = 2,
57 ANNOUNCE_INTERVAL = 2,
58 DEFEND_INTERVAL = 10
59};
60
61/* States during the configuration process. */
62enum {
63 PROBE = 0,
64 RATE_LIMIT_PROBE,
65 ANNOUNCE,
66 MONITOR,
67 DEFEND
68};
69
70#define VDBG(...) do { } while (0)
71
72
73enum {
74 sock_fd = 3
75};
76
77struct globals {
78 struct sockaddr saddr;
79 struct ether_addr eth_addr;
80} FIX_ALIASING;
81#define G (*(struct globals*)&bb_common_bufsiz1)
82#define saddr (G.saddr )
83#define eth_addr (G.eth_addr)
84
85
86/**
87 * Pick a random link local IP address on 169.254/16, except that
88 * the first and last 256 addresses are reserved.
89 */
90static uint32_t pick(void)
91{
92 unsigned tmp;
93
94 do {
95 tmp = rand() & IN_CLASSB_HOST;
96 } while (tmp > (IN_CLASSB_HOST - 0x0200));
97 return htonl((LINKLOCAL_ADDR + 0x0100) + tmp);
98}
99
100/**
101 * Broadcast an ARP packet.
102 */
103static void arp(
104 /* int op, - always ARPOP_REQUEST */
105 /* const struct ether_addr *source_eth, - always &eth_addr */
106 struct in_addr source_ip,
107 const struct ether_addr *target_eth, struct in_addr target_ip)
108{
109 enum { op = ARPOP_REQUEST };
110#define source_eth (&eth_addr)
111
112 struct arp_packet p;
113 memset(&p, 0, sizeof(p));
114
115 // ether header
116 p.eth.ether_type = htons(ETHERTYPE_ARP);
117 memcpy(p.eth.ether_shost, source_eth, ETH_ALEN);
118 memset(p.eth.ether_dhost, 0xff, ETH_ALEN);
119
120 // arp request
121 p.arp.arp_hrd = htons(ARPHRD_ETHER);
122 p.arp.arp_pro = htons(ETHERTYPE_IP);
123 p.arp.arp_hln = ETH_ALEN;
124 p.arp.arp_pln = 4;
125 p.arp.arp_op = htons(op);
126 memcpy(&p.arp.arp_sha, source_eth, ETH_ALEN);
127 memcpy(&p.arp.arp_spa, &source_ip, sizeof(p.arp.arp_spa));
128 memcpy(&p.arp.arp_tha, target_eth, ETH_ALEN);
129 memcpy(&p.arp.arp_tpa, &target_ip, sizeof(p.arp.arp_tpa));
130
131 // send it
132 // Even though sock_fd is already bound to saddr, just send()
133 // won't work, because "socket is not connected"
134 // (and connect() won't fix that, "operation not supported").
135 // Thus we sendto() to saddr. I wonder which sockaddr
136 // (from bind() or from sendto()?) kernel actually uses
137 // to determine iface to emit the packet from...
138 xsendto(sock_fd, &p, sizeof(p), &saddr, sizeof(saddr));
139#undef source_eth
140}
141
142/**
143 * Run a script.
144 * argv[0]:intf argv[1]:script_name argv[2]:junk argv[3]:NULL
145 */
146static int run(char *argv[3], const char *param, struct in_addr *ip)
147{
148 int status;
149 char *addr = addr; /* for gcc */
150 const char *fmt = "%s %s %s" + 3;
151
152 argv[2] = (char*)param;
153
154 VDBG("%s run %s %s\n", argv[0], argv[1], argv[2]);
155
156 if (ip) {
157 addr = inet_ntoa(*ip);
158 xsetenv("ip", addr);
159 fmt -= 3;
160 }
161 bb_info_msg(fmt, argv[2], argv[0], addr);
162
163 status = spawn_and_wait(argv + 1);
164 if (status < 0) {
165 bb_perror_msg("%s %s %s" + 3, argv[2], argv[0]);
166 return -errno;
167 }
168 if (status != 0)
169 bb_error_msg("script %s %s failed, exitcode=%d", argv[1], argv[2], status & 0xff);
170 return status;
171}
172
173/**
174 * Return milliseconds of random delay, up to "secs" seconds.
175 */
176static ALWAYS_INLINE unsigned random_delay_ms(unsigned secs)
177{
178 return rand() % (secs * 1000);
179}
180
181/**
182 * main program
183 */
184int zcip_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
185int zcip_main(int argc UNUSED_PARAM, char **argv)
186{
187 int state;
188 char *r_opt;
189 unsigned opts;
190
191 // ugly trick, but I want these zeroed in one go
192 struct {
193 const struct in_addr null_ip;
194 const struct ether_addr null_addr;
195 struct in_addr ip;
196 struct ifreq ifr;
197 int timeout_ms; /* must be signed */
198 unsigned conflicts;
199 unsigned nprobes;
200 unsigned nclaims;
201 int ready;
202 int verbose;
203 } L;
204#define null_ip (L.null_ip )
205#define null_addr (L.null_addr )
206#define ip (L.ip )
207#define ifr (L.ifr )
208#define timeout_ms (L.timeout_ms)
209#define conflicts (L.conflicts )
210#define nprobes (L.nprobes )
211#define nclaims (L.nclaims )
212#define ready (L.ready )
213#define verbose (L.verbose )
214
215 memset(&L, 0, sizeof(L));
216
217#define FOREGROUND (opts & 1)
218#define QUIT (opts & 2)
219 // parse commandline: prog [options] ifname script
220 // exactly 2 args; -v accumulates and implies -f
221 opt_complementary = "=2:vv:vf";
222 opts = getopt32(argv, "fqr:v", &r_opt, &verbose);
223#if !BB_MMU
224 // on NOMMU reexec early (or else we will rerun things twice)
225 if (!FOREGROUND)
226 bb_daemonize_or_rexec(0 /*was: DAEMON_CHDIR_ROOT*/, argv);
227#endif
228 // open an ARP socket
229 // (need to do it before openlog to prevent openlog from taking
230 // fd 3 (sock_fd==3))
231 xmove_fd(xsocket(AF_PACKET, SOCK_PACKET, htons(ETH_P_ARP)), sock_fd);
232 if (!FOREGROUND) {
233 // do it before all bb_xx_msg calls
234 openlog(applet_name, 0, LOG_DAEMON);
235 logmode |= LOGMODE_SYSLOG;
236 }
237 if (opts & 4) { // -r n.n.n.n
238 if (inet_aton(r_opt, &ip) == 0
239 || (ntohl(ip.s_addr) & IN_CLASSB_NET) != LINKLOCAL_ADDR
240 ) {
241 bb_error_msg_and_die("invalid link address");
242 }
243 }
244 argv += optind - 1;
245
246 /* Now: argv[0]:junk argv[1]:intf argv[2]:script argv[3]:NULL */
247 /* We need to make space for script argument: */
248 argv[0] = argv[1];
249 argv[1] = argv[2];
250 /* Now: argv[0]:intf argv[1]:script argv[2]:junk argv[3]:NULL */
251#define argv_intf (argv[0])
252
253 xsetenv("interface", argv_intf);
254
255 // initialize the interface (modprobe, ifup, etc)
256 if (run(argv, "init", NULL))
257 return EXIT_FAILURE;
258
259 // initialize saddr
260 // saddr is: { u16 sa_family; u8 sa_data[14]; }
261 //memset(&saddr, 0, sizeof(saddr));
262 //TODO: are we leaving sa_family == 0 (AF_UNSPEC)?!
263 safe_strncpy(saddr.sa_data, argv_intf, sizeof(saddr.sa_data));
264
265 // bind to the interface's ARP socket
266 xbind(sock_fd, &saddr, sizeof(saddr));
267
268 // get the interface's ethernet address
269 //memset(&ifr, 0, sizeof(ifr));
270 strncpy_IFNAMSIZ(ifr.ifr_name, argv_intf);
271 xioctl(sock_fd, SIOCGIFHWADDR, &ifr);
272 memcpy(&eth_addr, &ifr.ifr_hwaddr.sa_data, ETH_ALEN);
273
274 // start with some stable ip address, either a function of
275 // the hardware address or else the last address we used.
276 // we are taking low-order four bytes, as top-order ones
277 // aren't random enough.
278 // NOTE: the sequence of addresses we try changes only
279 // depending on when we detect conflicts.
280 {
281 uint32_t t;
282 move_from_unaligned32(t, ((char *)&eth_addr + 2));
283 srand(t);
284 }
285 if (ip.s_addr == 0)
286 ip.s_addr = pick();
287
288 // FIXME cases to handle:
289 // - zcip already running!
290 // - link already has local address... just defend/update
291
292 // daemonize now; don't delay system startup
293 if (!FOREGROUND) {
294#if BB_MMU
295 bb_daemonize(0 /*was: DAEMON_CHDIR_ROOT*/);
296#endif
297 bb_info_msg("start, interface %s", argv_intf);
298 }
299
300 // run the dynamic address negotiation protocol,
301 // restarting after address conflicts:
302 // - start with some address we want to try
303 // - short random delay
304 // - arp probes to see if another host uses it
305 // - arp announcements that we're claiming it
306 // - use it
307 // - defend it, within limits
308 // exit if:
309 // - address is successfully obtained and -q was given:
310 // run "<script> config", then exit with exitcode 0
311 // - poll error (when does this happen?)
312 // - read error (when does this happen?)
313 // - sendto error (in arp()) (when does this happen?)
314 // - revents & POLLERR (link down). run "<script> deconfig" first
315 state = PROBE;
316 while (1) {
317 struct pollfd fds[1];
318 unsigned deadline_us;
319 struct arp_packet p;
320 int source_ip_conflict;
321 int target_ip_conflict;
322
323 fds[0].fd = sock_fd;
324 fds[0].events = POLLIN;
325 fds[0].revents = 0;
326
327 // poll, being ready to adjust current timeout
328 if (!timeout_ms) {
329 timeout_ms = random_delay_ms(PROBE_WAIT);
330 // FIXME setsockopt(sock_fd, SO_ATTACH_FILTER, ...) to
331 // make the kernel filter out all packets except
332 // ones we'd care about.
333 }
334 // set deadline_us to the point in time when we timeout
335 deadline_us = MONOTONIC_US() + timeout_ms * 1000;
336
337 VDBG("...wait %d %s nprobes=%u, nclaims=%u\n",
338 timeout_ms, argv_intf, nprobes, nclaims);
339
340 switch (safe_poll(fds, 1, timeout_ms)) {
341
342 default:
343 //bb_perror_msg("poll"); - done in safe_poll
344 return EXIT_FAILURE;
345
346 // timeout
347 case 0:
348 VDBG("state = %d\n", state);
349 switch (state) {
350 case PROBE:
351 // timeouts in the PROBE state mean no conflicting ARP packets
352 // have been received, so we can progress through the states
353 if (nprobes < PROBE_NUM) {
354 nprobes++;
355 VDBG("probe/%u %s@%s\n",
356 nprobes, argv_intf, inet_ntoa(ip));
357 arp(/* ARPOP_REQUEST, */
358 /* &eth_addr, */ null_ip,
359 &null_addr, ip);
360 timeout_ms = PROBE_MIN * 1000;
361 timeout_ms += random_delay_ms(PROBE_MAX - PROBE_MIN);
362 }
363 else {
364 // Switch to announce state.
365 state = ANNOUNCE;
366 nclaims = 0;
367 VDBG("announce/%u %s@%s\n",
368 nclaims, argv_intf, inet_ntoa(ip));
369 arp(/* ARPOP_REQUEST, */
370 /* &eth_addr, */ ip,
371 &eth_addr, ip);
372 timeout_ms = ANNOUNCE_INTERVAL * 1000;
373 }
374 break;
375 case RATE_LIMIT_PROBE:
376 // timeouts in the RATE_LIMIT_PROBE state mean no conflicting ARP packets
377 // have been received, so we can move immediately to the announce state
378 state = ANNOUNCE;
379 nclaims = 0;
380 VDBG("announce/%u %s@%s\n",
381 nclaims, argv_intf, inet_ntoa(ip));
382 arp(/* ARPOP_REQUEST, */
383 /* &eth_addr, */ ip,
384 &eth_addr, ip);
385 timeout_ms = ANNOUNCE_INTERVAL * 1000;
386 break;
387 case ANNOUNCE:
388 // timeouts in the ANNOUNCE state mean no conflicting ARP packets
389 // have been received, so we can progress through the states
390 if (nclaims < ANNOUNCE_NUM) {
391 nclaims++;
392 VDBG("announce/%u %s@%s\n",
393 nclaims, argv_intf, inet_ntoa(ip));
394 arp(/* ARPOP_REQUEST, */
395 /* &eth_addr, */ ip,
396 &eth_addr, ip);
397 timeout_ms = ANNOUNCE_INTERVAL * 1000;
398 }
399 else {
400 // Switch to monitor state.
401 state = MONITOR;
402 // link is ok to use earlier
403 // FIXME update filters
404 run(argv, "config", &ip);
405 ready = 1;
406 conflicts = 0;
407 timeout_ms = -1; // Never timeout in the monitor state.
408
409 // NOTE: all other exit paths
410 // should deconfig ...
411 if (QUIT)
412 return EXIT_SUCCESS;
413 }
414 break;
415 case DEFEND:
416 // We won! No ARP replies, so just go back to monitor.
417 state = MONITOR;
418 timeout_ms = -1;
419 conflicts = 0;
420 break;
421 default:
422 // Invalid, should never happen. Restart the whole protocol.
423 state = PROBE;
424 ip.s_addr = pick();
425 timeout_ms = 0;
426 nprobes = 0;
427 nclaims = 0;
428 break;
429 } // switch (state)
430 break; // case 0 (timeout)
431
432 // packets arriving, or link went down
433 case 1:
434 // We need to adjust the timeout in case we didn't receive
435 // a conflicting packet.
436 if (timeout_ms > 0) {
437 unsigned diff = deadline_us - MONOTONIC_US();
438 if ((int)(diff) < 0) {
439 // Current time is greater than the expected timeout time.
440 // Should never happen.
441 VDBG("missed an expected timeout\n");
442 timeout_ms = 0;
443 } else {
444 VDBG("adjusting timeout\n");
445 timeout_ms = (diff / 1000) | 1; /* never 0 */
446 }
447 }
448
449 if ((fds[0].revents & POLLIN) == 0) {
450 if (fds[0].revents & POLLERR) {
451 // FIXME: links routinely go down;
452 // this shouldn't necessarily exit.
453 bb_error_msg("iface %s is down", argv_intf);
454 if (ready) {
455 run(argv, "deconfig", &ip);
456 }
457 return EXIT_FAILURE;
458 }
459 continue;
460 }
461
462 // read ARP packet
463 if (safe_read(sock_fd, &p, sizeof(p)) < 0) {
464 bb_perror_msg_and_die(bb_msg_read_error);
465 }
466 if (p.eth.ether_type != htons(ETHERTYPE_ARP))
467 continue;
468#ifdef DEBUG
469 {
470 struct ether_addr *sha = (struct ether_addr *) p.arp.arp_sha;
471 struct ether_addr *tha = (struct ether_addr *) p.arp.arp_tha;
472 struct in_addr *spa = (struct in_addr *) p.arp.arp_spa;
473 struct in_addr *tpa = (struct in_addr *) p.arp.arp_tpa;
474 VDBG("%s recv arp type=%d, op=%d,\n",
475 argv_intf, ntohs(p.eth.ether_type),
476 ntohs(p.arp.arp_op));
477 VDBG("\tsource=%s %s\n",
478 ether_ntoa(sha),
479 inet_ntoa(*spa));
480 VDBG("\ttarget=%s %s\n",
481 ether_ntoa(tha),
482 inet_ntoa(*tpa));
483 }
484#endif
485 if (p.arp.arp_op != htons(ARPOP_REQUEST)
486 && p.arp.arp_op != htons(ARPOP_REPLY))
487 continue;
488
489 source_ip_conflict = 0;
490 target_ip_conflict = 0;
491
492 if (memcmp(p.arp.arp_spa, &ip.s_addr, sizeof(struct in_addr)) == 0
493 && memcmp(&p.arp.arp_sha, &eth_addr, ETH_ALEN) != 0
494 ) {
495 source_ip_conflict = 1;
496 }
497 if (p.arp.arp_op == htons(ARPOP_REQUEST)
498 && memcmp(p.arp.arp_tpa, &ip.s_addr, sizeof(struct in_addr)) == 0
499 && memcmp(&p.arp.arp_tha, &eth_addr, ETH_ALEN) != 0
500 ) {
501 target_ip_conflict = 1;
502 }
503
504 VDBG("state = %d, source ip conflict = %d, target ip conflict = %d\n",
505 state, source_ip_conflict, target_ip_conflict);
506 switch (state) {
507 case PROBE:
508 case ANNOUNCE:
509 // When probing or announcing, check for source IP conflicts
510 // and other hosts doing ARP probes (target IP conflicts).
511 if (source_ip_conflict || target_ip_conflict) {
512 conflicts++;
513 if (conflicts >= MAX_CONFLICTS) {
514 VDBG("%s ratelimit\n", argv_intf);
515 timeout_ms = RATE_LIMIT_INTERVAL * 1000;
516 state = RATE_LIMIT_PROBE;
517 }
518
519 // restart the whole protocol
520 ip.s_addr = pick();
521 timeout_ms = 0;
522 nprobes = 0;
523 nclaims = 0;
524 }
525 break;
526 case MONITOR:
527 // If a conflict, we try to defend with a single ARP probe.
528 if (source_ip_conflict) {
529 VDBG("monitor conflict -- defending\n");
530 state = DEFEND;
531 timeout_ms = DEFEND_INTERVAL * 1000;
532 arp(/* ARPOP_REQUEST, */
533 /* &eth_addr, */ ip,
534 &eth_addr, ip);
535 }
536 break;
537 case DEFEND:
538 // Well, we tried. Start over (on conflict).
539 if (source_ip_conflict) {
540 state = PROBE;
541 VDBG("defend conflict -- starting over\n");
542 ready = 0;
543 run(argv, "deconfig", &ip);
544
545 // restart the whole protocol
546 ip.s_addr = pick();
547 timeout_ms = 0;
548 nprobes = 0;
549 nclaims = 0;
550 }
551 break;
552 default:
553 // Invalid, should never happen. Restart the whole protocol.
554 VDBG("invalid state -- starting over\n");
555 state = PROBE;
556 ip.s_addr = pick();
557 timeout_ms = 0;
558 nprobes = 0;
559 nclaims = 0;
560 break;
561 } // switch state
562 break; // case 1 (packets arriving)
563 } // switch poll
564 } // while (1)
565#undef argv_intf
566}
Note: See TracBrowser for help on using the repository browser.