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 xsendto(fd, &p, sizeof(p), saddr, sizeof(*saddr));
119 // Currently all callers ignore errors, that's why returns are
125 * Run a script. argv[2] is already NULL.
127 static int run(char *argv[3], const char *intf, struct in_addr *ip)
131 VDBG("%s run %s %s\n", intf, argv[0], argv[1]);
134 char *addr = inet_ntoa(*ip);
135 setenv("ip", addr, 1);
136 bb_info_msg("%s %s %s", argv[1], intf, addr);
139 status = wait4pid(spawn(argv));
141 bb_perror_msg("%s %s", argv[1], intf);
145 bb_error_msg("script %s %s failed, exitcode=%d", argv[0], argv[1], status);
150 * Return milliseconds of random delay, up to "secs" seconds.
152 static unsigned ATTRIBUTE_ALWAYS_INLINE ms_rdelay(unsigned secs)
154 return lrand48() % (secs * 1000);
160 int zcip_main(int argc, char **argv);
161 int zcip_main(int argc, char **argv)
164 struct ether_addr eth_addr;
170 /* Ugly trick, but I want these zeroed in one go */
172 const struct in_addr null_ip;
173 const struct ether_addr null_addr;
174 struct sockaddr saddr;
179 suseconds_t timeout; // milliseconds
186 #define null_ip (L.null_ip )
187 #define null_addr (L.null_addr)
188 #define saddr (L.saddr )
191 #define intf (L.intf )
192 #define script_av (L.script_av)
193 #define timeout (L.timeout )
194 #define conflicts (L.conflicts)
195 #define nprobes (L.nprobes )
196 #define nclaims (L.nclaims )
197 #define ready (L.ready )
198 #define verbose (L.verbose )
200 memset(&L, 0, sizeof(L));
202 #define FOREGROUND (opts & 1)
203 #define QUIT (opts & 2)
204 // parse commandline: prog [options] ifname script
205 // exactly 2 args; -v accumulates and implies -f
206 opt_complementary = "=2:vv:vf";
207 opts = getopt32(argc, argv, "fqr:v", &r_opt, &verbose);
209 /* Do it early, before all bb_xx_msg calls */
210 openlog(applet_name, 0, LOG_DAEMON);
211 logmode |= LOGMODE_SYSLOG;
213 if (opts & 4) { // -r n.n.n.n
214 if (inet_aton(r_opt, &ip) == 0
215 || (ntohl(ip.s_addr) & IN_CLASSB_NET) != LINKLOCAL_ADDR
217 bb_error_msg_and_die("invalid link address");
220 // On NOMMU reexec early (or else we will rerun things twice)
223 bb_daemonize_or_rexec(DAEMON_CHDIR_ROOT, argv);
229 script_av[0] = argv[1];
230 setenv("interface", intf, 1);
232 // initialize the interface (modprobe, ifup, etc)
233 script_av[1] = (char*)"init";
234 if (run(script_av, intf, NULL))
238 //memset(&saddr, 0, sizeof(saddr));
239 safe_strncpy(saddr.sa_data, intf, sizeof(saddr.sa_data));
241 // open an ARP socket
242 fd = xsocket(PF_PACKET, SOCK_PACKET, htons(ETH_P_ARP));
243 // bind to the interface's ARP socket
244 xbind(fd, &saddr, sizeof(saddr));
246 // get the interface's ethernet address
247 //memset(&ifr, 0, sizeof(ifr));
248 strncpy(ifr.ifr_name, intf, sizeof(ifr.ifr_name));
249 if (ioctl(fd, SIOCGIFHWADDR, &ifr) < 0) {
250 bb_perror_msg_and_die("get ethernet address");
252 memcpy(ð_addr, &ifr.ifr_hwaddr.sa_data, ETH_ALEN);
254 // start with some stable ip address, either a function of
255 // the hardware address or else the last address we used.
256 // NOTE: the sequence of addresses we try changes only
257 // depending on when we detect conflicts.
258 // (SVID 3 bogon: who says that "short" is always 16 bits?)
259 seed48( (unsigned short*)&ifr.ifr_hwaddr.sa_data );
263 // FIXME cases to handle:
264 // - zcip already running!
265 // - link already has local address... just defend/update
267 // daemonize now; don't delay system startup
270 bb_daemonize(DAEMON_CHDIR_ROOT);
272 bb_info_msg("start, interface %s", intf);
275 // run the dynamic address negotiation protocol,
276 // restarting after address conflicts:
277 // - start with some address we want to try
278 // - short random delay
279 // - arp probes to see if another host else uses it
280 // - arp announcements that we're claiming it
282 // - defend it, within limits
284 struct pollfd fds[1];
288 int source_ip_conflict = 0;
289 int target_ip_conflict = 0;
292 fds[0].events = POLLIN;
295 // poll, being ready to adjust current timeout
297 timeout = ms_rdelay(PROBE_WAIT);
298 // FIXME setsockopt(fd, SO_ATTACH_FILTER, ...) to
299 // make the kernel filter out all packets except
300 // ones we'd care about.
302 // set tv1 to the point in time when we timeout
303 gettimeofday(&tv1, NULL);
304 tv1.tv_usec += (timeout % 1000) * 1000;
305 while (tv1.tv_usec > 1000000) {
306 tv1.tv_usec -= 1000000;
309 tv1.tv_sec += timeout / 1000;
311 VDBG("...wait %ld %s nprobes=%d, nclaims=%d\n",
312 timeout, intf, nprobes, nclaims);
313 switch (poll(fds, 1, timeout)) {
317 VDBG("state = %d\n", state);
320 // timeouts in the PROBE state mean no conflicting ARP packets
321 // have been received, so we can progress through the states
322 if (nprobes < PROBE_NUM) {
324 VDBG("probe/%d %s@%s\n",
325 nprobes, intf, inet_ntoa(ip));
326 arp(fd, &saddr, ARPOP_REQUEST,
329 timeout = PROBE_MIN * 1000;
330 timeout += ms_rdelay(PROBE_MAX
334 // Switch to announce state.
337 VDBG("announce/%d %s@%s\n",
338 nclaims, intf, inet_ntoa(ip));
339 arp(fd, &saddr, ARPOP_REQUEST,
342 timeout = ANNOUNCE_INTERVAL * 1000;
345 case RATE_LIMIT_PROBE:
346 // timeouts in the RATE_LIMIT_PROBE state mean no conflicting ARP packets
347 // have been received, so we can move immediately to the announce state
350 VDBG("announce/%d %s@%s\n",
351 nclaims, intf, inet_ntoa(ip));
352 arp(fd, &saddr, ARPOP_REQUEST,
355 timeout = ANNOUNCE_INTERVAL * 1000;
358 // timeouts in the ANNOUNCE state mean no conflicting ARP packets
359 // have been received, so we can progress through the states
360 if (nclaims < ANNOUNCE_NUM) {
362 VDBG("announce/%d %s@%s\n",
363 nclaims, intf, inet_ntoa(ip));
364 arp(fd, &saddr, ARPOP_REQUEST,
367 timeout = ANNOUNCE_INTERVAL * 1000;
370 // Switch to monitor state.
372 // link is ok to use earlier
373 // FIXME update filters
374 script_av[1] = (char*)"config";
375 run(script_av, intf, &ip);
378 timeout = -1; // Never timeout in the monitor state.
380 // NOTE: all other exit paths
381 // should deconfig ...
387 // We won! No ARP replies, so just go back to monitor.
393 // Invalid, should never happen. Restart the whole protocol.
401 break; // case 0 (timeout)
404 // We need to adjust the timeout in case we didn't receive
405 // a conflicting packet.
409 gettimeofday(&tv2, NULL);
410 if (timercmp(&tv1, &tv2, <)) {
411 // Current time is greater than the expected timeout time.
412 // Should never happen.
413 VDBG("missed an expected timeout\n");
416 VDBG("adjusting timeout\n");
417 timersub(&tv1, &tv2, &tv1);
418 timeout = 1000 * tv1.tv_sec
419 + tv1.tv_usec / 1000;
423 if ((fds[0].revents & POLLIN) == 0) {
424 if (fds[0].revents & POLLERR) {
425 // FIXME: links routinely go down;
426 // this shouldn't necessarily exit.
427 bb_error_msg("%s: poll error", intf);
429 script_av[1] = (char*)"deconfig";
430 run(script_av, intf, &ip);
438 if (recv(fd, &p, sizeof(p), 0) < 0) {
442 if (p.hdr.ether_type != htons(ETHERTYPE_ARP))
447 struct ether_addr * sha = (struct ether_addr *) p.arp.arp_sha;
448 struct ether_addr * tha = (struct ether_addr *) p.arp.arp_tha;
449 struct in_addr * spa = (struct in_addr *) p.arp.arp_spa;
450 struct in_addr * tpa = (struct in_addr *) p.arp.arp_tpa;
451 VDBG("%s recv arp type=%d, op=%d,\n",
452 intf, ntohs(p.hdr.ether_type),
453 ntohs(p.arp.arp_op));
454 VDBG("\tsource=%s %s\n",
457 VDBG("\ttarget=%s %s\n",
462 if (p.arp.arp_op != htons(ARPOP_REQUEST)
463 && p.arp.arp_op != htons(ARPOP_REPLY))
466 if (memcmp(p.arp.arp_spa, &ip.s_addr, sizeof(struct in_addr)) == 0 &&
467 memcmp(ð_addr, &p.arp.arp_sha, ETH_ALEN) != 0) {
468 source_ip_conflict = 1;
470 if (memcmp(p.arp.arp_tpa, &ip.s_addr, sizeof(struct in_addr)) == 0 &&
471 p.arp.arp_op == htons(ARPOP_REQUEST) &&
472 memcmp(ð_addr, &p.arp.arp_tha, ETH_ALEN) != 0) {
473 target_ip_conflict = 1;
476 VDBG("state = %d, source ip conflict = %d, target ip conflict = %d\n",
477 state, source_ip_conflict, target_ip_conflict);
481 // When probing or announcing, check for source IP conflicts
482 // and other hosts doing ARP probes (target IP conflicts).
483 if (source_ip_conflict || target_ip_conflict) {
485 if (conflicts >= MAX_CONFLICTS) {
486 VDBG("%s ratelimit\n", intf);
487 timeout = RATE_LIMIT_INTERVAL * 1000;
488 state = RATE_LIMIT_PROBE;
491 // restart the whole protocol
499 // If a conflict, we try to defend with a single ARP probe.
500 if (source_ip_conflict) {
501 VDBG("monitor conflict -- defending\n");
503 timeout = DEFEND_INTERVAL * 1000;
511 // Well, we tried. Start over (on conflict).
512 if (source_ip_conflict) {
514 VDBG("defend conflict -- starting over\n");
516 script_av[1] = (char*)"deconfig";
517 run(script_av, intf, &ip);
519 // restart the whole protocol
527 // Invalid, should never happen. Restart the whole protocol.
528 VDBG("invalid state -- starting over\n");
537 break; // case 1 (packets arriving)
544 bb_perror_msg("%s, %s", intf, why);