1 /* vi: set sw=4 ts=4: */
3 * RFC3927 ZeroConf IPv4 Link-Local addressing
4 * (see <http://www.zeroconf.org/>)
6 * Copyright (C) 2003 by Arthur van Hoff (avh@strangeberry.com)
7 * Copyright (C) 2004 by David Brownell
9 * Licensed under the GPL v2 or later, see the file LICENSE in this tarball.
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.
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)
30 #include <netinet/ether.h>
31 #include <net/ethernet.h>
33 #include <net/if_arp.h>
35 #include <linux/if_packet.h>
36 #include <linux/sockios.h>
40 struct ether_header hdr;
46 LINKLOCAL_ADDR = 0xa9fe0000,
48 /* protocol timeout parameters, specified in seconds */
54 RATE_LIMIT_INTERVAL = 60,
57 ANNOUNCE_INTERVAL = 2,
61 /* States during the configuration process. */
70 #define VDBG(fmt,args...) \
74 * Pick a random link local IP address on 169.254/16, except that
75 * the first and last 256 addresses are reserved.
77 static void pick(struct in_addr *ip)
81 /* use cheaper math than lrand48() mod N */
83 tmp = (lrand48() >> 16) & IN_CLASSB_HOST;
84 } while (tmp > (IN_CLASSB_HOST - 0x0200));
85 ip->s_addr = htonl((LINKLOCAL_ADDR + 0x0100) + tmp);
88 /* TODO: we need a flag to direct bb_[p]error_msg output to stderr. */
91 * Broadcast an ARP packet.
93 static void arp(int fd, struct sockaddr *saddr, int op,
94 const struct ether_addr *source_addr, struct in_addr source_ip,
95 const struct ether_addr *target_addr, struct in_addr target_ip)
98 memset(&p, 0, sizeof(p));
101 p.hdr.ether_type = htons(ETHERTYPE_ARP);
102 memcpy(p.hdr.ether_shost, source_addr, ETH_ALEN);
103 memset(p.hdr.ether_dhost, 0xff, ETH_ALEN);
106 p.arp.arp_hrd = htons(ARPHRD_ETHER);
107 p.arp.arp_pro = htons(ETHERTYPE_IP);
108 p.arp.arp_hln = ETH_ALEN;
110 p.arp.arp_op = htons(op);
111 memcpy(&p.arp.arp_sha, source_addr, ETH_ALEN);
112 memcpy(&p.arp.arp_spa, &source_ip, sizeof(p.arp.arp_spa));
113 memcpy(&p.arp.arp_tha, target_addr, ETH_ALEN);
114 memcpy(&p.arp.arp_tpa, &target_ip, sizeof(p.arp.arp_tpa));
117 if (sendto(fd, &p, sizeof(p), 0, saddr, sizeof(*saddr)) < 0) {
118 bb_perror_msg("sendto");
121 // Currently all callers ignore errors, that's why returns are
127 * Run a script. argv[2] is already NULL.
129 static int run(char *argv[3], const char *intf, struct in_addr *ip)
133 VDBG("%s run %s %s\n", intf, argv[0], argv[1]);
136 char *addr = inet_ntoa(*ip);
137 setenv("ip", addr, 1);
138 bb_info_msg("%s %s %s", argv[1], intf, addr);
141 status = wait4pid(spawn(argv));
143 bb_perror_msg("%s %s", argv[1], intf);
147 bb_error_msg("script %s %s failed, exitcode=%d", argv[0], argv[1], status);
152 * Return milliseconds of random delay, up to "secs" seconds.
154 static unsigned ATTRIBUTE_ALWAYS_INLINE ms_rdelay(unsigned secs)
156 return lrand48() % (secs * 1000);
162 int zcip_main(int argc, char **argv);
163 int zcip_main(int argc, char **argv)
166 struct ether_addr eth_addr;
172 /* Ugly trick, but I want these zeroed in one go */
174 const struct in_addr null_ip;
175 const struct ether_addr null_addr;
176 struct sockaddr saddr;
181 suseconds_t timeout; // milliseconds
188 #define null_ip (L.null_ip )
189 #define null_addr (L.null_addr)
190 #define saddr (L.saddr )
193 #define intf (L.intf )
194 #define script_av (L.script_av)
195 #define timeout (L.timeout )
196 #define conflicts (L.conflicts)
197 #define nprobes (L.nprobes )
198 #define nclaims (L.nclaims )
199 #define ready (L.ready )
200 #define verbose (L.verbose )
202 memset(&L, 0, sizeof(L));
204 #define FOREGROUND (opts & 1)
205 #define QUIT (opts & 2)
206 // parse commandline: prog [options] ifname script
207 // exactly 2 args; -v accumulates and implies -f
208 opt_complementary = "=2:vv:vf";
209 opts = getopt32(argc, argv, "fqr:v", &r_opt, &verbose);
211 /* Do it early, before all bb_xx_msg calls */
212 openlog(applet_name, 0, LOG_DAEMON);
213 logmode |= LOGMODE_SYSLOG;
215 if (opts & 4) { // -r n.n.n.n
216 if (inet_aton(r_opt, &ip) == 0
217 || (ntohl(ip.s_addr) & IN_CLASSB_NET) != LINKLOCAL_ADDR
219 bb_error_msg_and_die("invalid link address");
222 // On NOMMU reexec early (or else we will rerun things twice)
225 bb_daemonize_or_rexec(DAEMON_CHDIR_ROOT, argv);
231 script_av[0] = argv[1];
232 setenv("interface", intf, 1);
234 // initialize the interface (modprobe, ifup, etc)
235 script_av[1] = (char*)"init";
236 if (run(script_av, intf, NULL))
240 //memset(&saddr, 0, sizeof(saddr));
241 safe_strncpy(saddr.sa_data, intf, sizeof(saddr.sa_data));
243 // open an ARP socket
244 fd = xsocket(PF_PACKET, SOCK_PACKET, htons(ETH_P_ARP));
245 // bind to the interface's ARP socket
246 xbind(fd, &saddr, sizeof(saddr));
248 // get the interface's ethernet address
249 //memset(&ifr, 0, sizeof(ifr));
250 strncpy(ifr.ifr_name, intf, sizeof(ifr.ifr_name));
251 if (ioctl(fd, SIOCGIFHWADDR, &ifr) < 0) {
252 bb_perror_msg_and_die("get ethernet address");
254 memcpy(ð_addr, &ifr.ifr_hwaddr.sa_data, ETH_ALEN);
256 // start with some stable ip address, either a function of
257 // the hardware address or else the last address we used.
258 // NOTE: the sequence of addresses we try changes only
259 // depending on when we detect conflicts.
260 // (SVID 3 bogon: who says that "short" is always 16 bits?)
261 seed48( (unsigned short*)&ifr.ifr_hwaddr.sa_data );
265 // FIXME cases to handle:
266 // - zcip already running!
267 // - link already has local address... just defend/update
269 // daemonize now; don't delay system startup
272 bb_daemonize(DAEMON_CHDIR_ROOT);
274 bb_info_msg("start, interface %s", intf);
277 // run the dynamic address negotiation protocol,
278 // restarting after address conflicts:
279 // - start with some address we want to try
280 // - short random delay
281 // - arp probes to see if another host else uses it
282 // - arp announcements that we're claiming it
284 // - defend it, within limits
286 struct pollfd fds[1];
290 int source_ip_conflict = 0;
291 int target_ip_conflict = 0;
294 fds[0].events = POLLIN;
297 // poll, being ready to adjust current timeout
299 timeout = ms_rdelay(PROBE_WAIT);
300 // FIXME setsockopt(fd, SO_ATTACH_FILTER, ...) to
301 // make the kernel filter out all packets except
302 // ones we'd care about.
304 // set tv1 to the point in time when we timeout
305 gettimeofday(&tv1, NULL);
306 tv1.tv_usec += (timeout % 1000) * 1000;
307 while (tv1.tv_usec > 1000000) {
308 tv1.tv_usec -= 1000000;
311 tv1.tv_sec += timeout / 1000;
313 VDBG("...wait %ld %s nprobes=%d, nclaims=%d\n",
314 timeout, intf, nprobes, nclaims);
315 switch (poll(fds, 1, timeout)) {
319 VDBG("state = %d\n", state);
322 // timeouts in the PROBE state mean no conflicting ARP packets
323 // have been received, so we can progress through the states
324 if (nprobes < PROBE_NUM) {
326 VDBG("probe/%d %s@%s\n",
327 nprobes, intf, inet_ntoa(ip));
328 arp(fd, &saddr, ARPOP_REQUEST,
331 timeout = PROBE_MIN * 1000;
332 timeout += ms_rdelay(PROBE_MAX
336 // Switch to announce state.
339 VDBG("announce/%d %s@%s\n",
340 nclaims, intf, inet_ntoa(ip));
341 arp(fd, &saddr, ARPOP_REQUEST,
344 timeout = ANNOUNCE_INTERVAL * 1000;
347 case RATE_LIMIT_PROBE:
348 // timeouts in the RATE_LIMIT_PROBE state mean no conflicting ARP packets
349 // have been received, so we can move immediately to the announce state
352 VDBG("announce/%d %s@%s\n",
353 nclaims, intf, inet_ntoa(ip));
354 arp(fd, &saddr, ARPOP_REQUEST,
357 timeout = ANNOUNCE_INTERVAL * 1000;
360 // timeouts in the ANNOUNCE state mean no conflicting ARP packets
361 // have been received, so we can progress through the states
362 if (nclaims < ANNOUNCE_NUM) {
364 VDBG("announce/%d %s@%s\n",
365 nclaims, intf, inet_ntoa(ip));
366 arp(fd, &saddr, ARPOP_REQUEST,
369 timeout = ANNOUNCE_INTERVAL * 1000;
372 // Switch to monitor state.
374 // link is ok to use earlier
375 // FIXME update filters
376 script_av[1] = (char*)"config";
377 run(script_av, intf, &ip);
380 timeout = -1; // Never timeout in the monitor state.
382 // NOTE: all other exit paths
383 // should deconfig ...
389 // We won! No ARP replies, so just go back to monitor.
395 // Invalid, should never happen. Restart the whole protocol.
403 break; // case 0 (timeout)
406 // We need to adjust the timeout in case we didn't receive
407 // a conflicting packet.
411 gettimeofday(&tv2, NULL);
412 if (timercmp(&tv1, &tv2, <)) {
413 // Current time is greater than the expected timeout time.
414 // Should never happen.
415 VDBG("missed an expected timeout\n");
418 VDBG("adjusting timeout\n");
419 timersub(&tv1, &tv2, &tv1);
420 timeout = 1000 * tv1.tv_sec
421 + tv1.tv_usec / 1000;
425 if ((fds[0].revents & POLLIN) == 0) {
426 if (fds[0].revents & POLLERR) {
427 // FIXME: links routinely go down;
428 // this shouldn't necessarily exit.
429 bb_error_msg("%s: poll error", intf);
431 script_av[1] = (char*)"deconfig";
432 run(script_av, intf, &ip);
440 if (recv(fd, &p, sizeof(p), 0) < 0) {
444 if (p.hdr.ether_type != htons(ETHERTYPE_ARP))
449 struct ether_addr * sha = (struct ether_addr *) p.arp.arp_sha;
450 struct ether_addr * tha = (struct ether_addr *) p.arp.arp_tha;
451 struct in_addr * spa = (struct in_addr *) p.arp.arp_spa;
452 struct in_addr * tpa = (struct in_addr *) p.arp.arp_tpa;
453 VDBG("%s recv arp type=%d, op=%d,\n",
454 intf, ntohs(p.hdr.ether_type),
455 ntohs(p.arp.arp_op));
456 VDBG("\tsource=%s %s\n",
459 VDBG("\ttarget=%s %s\n",
464 if (p.arp.arp_op != htons(ARPOP_REQUEST)
465 && p.arp.arp_op != htons(ARPOP_REPLY))
468 if (memcmp(p.arp.arp_spa, &ip.s_addr, sizeof(struct in_addr)) == 0 &&
469 memcmp(ð_addr, &p.arp.arp_sha, ETH_ALEN) != 0) {
470 source_ip_conflict = 1;
472 if (memcmp(p.arp.arp_tpa, &ip.s_addr, sizeof(struct in_addr)) == 0 &&
473 p.arp.arp_op == htons(ARPOP_REQUEST) &&
474 memcmp(ð_addr, &p.arp.arp_tha, ETH_ALEN) != 0) {
475 target_ip_conflict = 1;
478 VDBG("state = %d, source ip conflict = %d, target ip conflict = %d\n",
479 state, source_ip_conflict, target_ip_conflict);
483 // When probing or announcing, check for source IP conflicts
484 // and other hosts doing ARP probes (target IP conflicts).
485 if (source_ip_conflict || target_ip_conflict) {
487 if (conflicts >= MAX_CONFLICTS) {
488 VDBG("%s ratelimit\n", intf);
489 timeout = RATE_LIMIT_INTERVAL * 1000;
490 state = RATE_LIMIT_PROBE;
493 // restart the whole protocol
501 // If a conflict, we try to defend with a single ARP probe.
502 if (source_ip_conflict) {
503 VDBG("monitor conflict -- defending\n");
505 timeout = DEFEND_INTERVAL * 1000;
513 // Well, we tried. Start over (on conflict).
514 if (source_ip_conflict) {
516 VDBG("defend conflict -- starting over\n");
518 script_av[1] = (char*)"deconfig";
519 run(script_av, intf, &ip);
521 // restart the whole protocol
529 // Invalid, should never happen. Restart the whole protocol.
530 VDBG("invalid state -- starting over\n");
539 break; // case 1 (packets arriving)
546 bb_perror_msg("%s, %s", intf, why);