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)
29 #include <netinet/ether.h>
30 #include <net/ethernet.h>
32 #include <net/if_arp.h>
33 #include <linux/if_packet.h>
34 #include <linux/sockios.h>
38 /* We don't need more than 32 bits of the counter */
39 #define MONOTONIC_US() ((unsigned)monotonic_us())
42 struct ether_header hdr;
48 LINKLOCAL_ADDR = 0xa9fe0000,
50 /* protocol timeout parameters, specified in seconds */
56 RATE_LIMIT_INTERVAL = 60,
59 ANNOUNCE_INTERVAL = 2,
63 /* States during the configuration process. */
72 #define VDBG(fmt,args...) \
76 * Pick a random link local IP address on 169.254/16, except that
77 * the first and last 256 addresses are reserved.
79 static void pick(struct in_addr *ip)
84 tmp = rand() & IN_CLASSB_HOST;
85 } while (tmp > (IN_CLASSB_HOST - 0x0200));
86 ip->s_addr = htonl((LINKLOCAL_ADDR + 0x0100) + tmp);
90 * Broadcast an ARP packet.
92 static void arp(int fd, struct sockaddr *saddr, int op,
93 const struct ether_addr *source_addr, struct in_addr source_ip,
94 const struct ether_addr *target_addr, struct in_addr target_ip)
97 memset(&p, 0, sizeof(p));
100 p.hdr.ether_type = htons(ETHERTYPE_ARP);
101 memcpy(p.hdr.ether_shost, source_addr, ETH_ALEN);
102 memset(p.hdr.ether_dhost, 0xff, ETH_ALEN);
105 p.arp.arp_hrd = htons(ARPHRD_ETHER);
106 p.arp.arp_pro = htons(ETHERTYPE_IP);
107 p.arp.arp_hln = ETH_ALEN;
109 p.arp.arp_op = htons(op);
110 memcpy(&p.arp.arp_sha, source_addr, ETH_ALEN);
111 memcpy(&p.arp.arp_spa, &source_ip, sizeof(p.arp.arp_spa));
112 memcpy(&p.arp.arp_tha, target_addr, ETH_ALEN);
113 memcpy(&p.arp.arp_tpa, &target_ip, sizeof(p.arp.arp_tpa));
116 xsendto(fd, &p, sizeof(p), saddr, sizeof(*saddr));
118 // Currently all callers ignore errors, that's why returns are
124 * Run a script. argv[2] is already NULL.
126 static int run(char *argv[3], const char *intf, struct in_addr *ip)
130 VDBG("%s run %s %s\n", intf, argv[0], argv[1]);
133 char *addr = inet_ntoa(*ip);
134 setenv("ip", addr, 1);
135 bb_info_msg("%s %s %s", argv[1], intf, addr);
138 status = wait4pid(spawn(argv));
140 bb_perror_msg("%s %s", argv[1], intf);
144 bb_error_msg("script %s %s failed, exitcode=%d", argv[0], argv[1], status);
149 * Return milliseconds of random delay, up to "secs" seconds.
151 static unsigned ALWAYS_INLINE ms_rdelay(unsigned secs)
153 return rand() % (secs * 1000);
159 int zcip_main(int argc, char **argv);
160 int zcip_main(int argc, char **argv)
163 struct ether_addr eth_addr;
169 /* Ugly trick, but I want these zeroed in one go */
171 const struct in_addr null_ip;
172 const struct ether_addr null_addr;
173 struct sockaddr saddr;
178 int timeout_ms; /* must be signed */
185 #define null_ip (L.null_ip )
186 #define null_addr (L.null_addr )
187 #define saddr (L.saddr )
190 #define intf (L.intf )
191 #define script_av (L.script_av )
192 #define timeout_ms (L.timeout_ms)
193 #define conflicts (L.conflicts )
194 #define nprobes (L.nprobes )
195 #define nclaims (L.nclaims )
196 #define ready (L.ready )
197 #define verbose (L.verbose )
199 memset(&L, 0, sizeof(L));
201 srand(MONOTONIC_US());
203 #define FOREGROUND (opts & 1)
204 #define QUIT (opts & 2)
205 // parse commandline: prog [options] ifname script
206 // exactly 2 args; -v accumulates and implies -f
207 opt_complementary = "=2:vv:vf";
208 opts = getopt32(argc, argv, "fqr:v", &r_opt, &verbose);
210 /* Do it early, before all bb_xx_msg calls */
211 openlog(applet_name, 0, LOG_DAEMON);
212 logmode |= LOGMODE_SYSLOG;
214 if (opts & 4) { // -r n.n.n.n
215 if (inet_aton(r_opt, &ip) == 0
216 || (ntohl(ip.s_addr) & IN_CLASSB_NET) != LINKLOCAL_ADDR
218 bb_error_msg_and_die("invalid link address");
221 // On NOMMU reexec early (or else we will rerun things twice)
224 bb_daemonize_or_rexec(DAEMON_CHDIR_ROOT, argv);
230 script_av[0] = argv[1];
231 setenv("interface", intf, 1);
233 // initialize the interface (modprobe, ifup, etc)
234 script_av[1] = (char*)"init";
235 if (run(script_av, intf, NULL))
239 //memset(&saddr, 0, sizeof(saddr));
240 safe_strncpy(saddr.sa_data, intf, sizeof(saddr.sa_data));
242 // open an ARP socket
243 fd = xsocket(PF_PACKET, SOCK_PACKET, htons(ETH_P_ARP));
244 // bind to the interface's ARP socket
245 xbind(fd, &saddr, sizeof(saddr));
247 // get the interface's ethernet address
248 //memset(&ifr, 0, sizeof(ifr));
249 strncpy(ifr.ifr_name, intf, sizeof(ifr.ifr_name));
250 if (ioctl(fd, SIOCGIFHWADDR, &ifr) < 0) {
251 bb_perror_msg_and_die("get ethernet address");
253 memcpy(ð_addr, &ifr.ifr_hwaddr.sa_data, ETH_ALEN);
255 // start with some stable ip address, either a function of
256 // the hardware address or else the last address we used.
257 // NOTE: the sequence of addresses we try changes only
258 // depending on when we detect conflicts.
259 // (SVID 3 bogon: who says that "short" is always 16 bits?)
260 seed48( (unsigned short*)&ifr.ifr_hwaddr.sa_data );
264 // FIXME cases to handle:
265 // - zcip already running!
266 // - link already has local address... just defend/update
268 // daemonize now; don't delay system startup
271 bb_daemonize(DAEMON_CHDIR_ROOT);
273 bb_info_msg("start, interface %s", intf);
276 // run the dynamic address negotiation protocol,
277 // restarting after address conflicts:
278 // - start with some address we want to try
279 // - short random delay
280 // - arp probes to see if another host else uses it
281 // - arp announcements that we're claiming it
283 // - defend it, within limits
285 struct pollfd fds[1];
286 unsigned deadline_us;
289 int source_ip_conflict = 0;
290 int target_ip_conflict = 0;
293 fds[0].events = POLLIN;
296 // poll, being ready to adjust current timeout
298 timeout_ms = ms_rdelay(PROBE_WAIT);
299 // FIXME setsockopt(fd, SO_ATTACH_FILTER, ...) to
300 // make the kernel filter out all packets except
301 // ones we'd care about.
303 // set deadline_us to the point in time when we timeout
304 deadline_us = MONOTONIC_US() + timeout_ms * 1000;
306 VDBG("...wait %d %s nprobes=%u, nclaims=%u\n",
307 timeout_ms, intf, nprobes, nclaims);
308 switch (poll(fds, 1, timeout_ms)) {
312 VDBG("state = %d\n", state);
315 // timeouts in the PROBE state mean no conflicting ARP packets
316 // have been received, so we can progress through the states
317 if (nprobes < PROBE_NUM) {
319 VDBG("probe/%u %s@%s\n",
320 nprobes, intf, inet_ntoa(ip));
321 arp(fd, &saddr, ARPOP_REQUEST,
324 timeout_ms = PROBE_MIN * 1000;
325 timeout_ms += ms_rdelay(PROBE_MAX - PROBE_MIN);
328 // Switch to announce state.
331 VDBG("announce/%u %s@%s\n",
332 nclaims, intf, inet_ntoa(ip));
333 arp(fd, &saddr, ARPOP_REQUEST,
336 timeout_ms = ANNOUNCE_INTERVAL * 1000;
339 case RATE_LIMIT_PROBE:
340 // timeouts in the RATE_LIMIT_PROBE state mean no conflicting ARP packets
341 // have been received, so we can move immediately to the announce state
344 VDBG("announce/%u %s@%s\n",
345 nclaims, intf, inet_ntoa(ip));
346 arp(fd, &saddr, ARPOP_REQUEST,
349 timeout_ms = ANNOUNCE_INTERVAL * 1000;
352 // timeouts in the ANNOUNCE state mean no conflicting ARP packets
353 // have been received, so we can progress through the states
354 if (nclaims < ANNOUNCE_NUM) {
356 VDBG("announce/%u %s@%s\n",
357 nclaims, intf, inet_ntoa(ip));
358 arp(fd, &saddr, ARPOP_REQUEST,
361 timeout_ms = ANNOUNCE_INTERVAL * 1000;
364 // Switch to monitor state.
366 // link is ok to use earlier
367 // FIXME update filters
368 script_av[1] = (char*)"config";
369 run(script_av, intf, &ip);
372 timeout_ms = -1; // Never timeout in the monitor state.
374 // NOTE: all other exit paths
375 // should deconfig ...
381 // We won! No ARP replies, so just go back to monitor.
387 // Invalid, should never happen. Restart the whole protocol.
395 break; // case 0 (timeout)
398 // We need to adjust the timeout in case we didn't receive
399 // a conflicting packet.
400 if (timeout_ms > 0) {
401 unsigned diff = deadline_us - MONOTONIC_US();
402 if ((int)(diff) < 0) {
403 // Current time is greater than the expected timeout time.
404 // Should never happen.
405 VDBG("missed an expected timeout\n");
408 VDBG("adjusting timeout\n");
409 timeout_ms = diff / 1000;
410 if (!timeout_ms) timeout_ms = 1;
414 if ((fds[0].revents & POLLIN) == 0) {
415 if (fds[0].revents & POLLERR) {
416 // FIXME: links routinely go down;
417 // this shouldn't necessarily exit.
418 bb_error_msg("%s: poll error", intf);
420 script_av[1] = (char*)"deconfig";
421 run(script_av, intf, &ip);
429 if (recv(fd, &p, sizeof(p), 0) < 0) {
433 if (p.hdr.ether_type != htons(ETHERTYPE_ARP))
438 struct ether_addr * sha = (struct ether_addr *) p.arp.arp_sha;
439 struct ether_addr * tha = (struct ether_addr *) p.arp.arp_tha;
440 struct in_addr * spa = (struct in_addr *) p.arp.arp_spa;
441 struct in_addr * tpa = (struct in_addr *) p.arp.arp_tpa;
442 VDBG("%s recv arp type=%d, op=%d,\n",
443 intf, ntohs(p.hdr.ether_type),
444 ntohs(p.arp.arp_op));
445 VDBG("\tsource=%s %s\n",
448 VDBG("\ttarget=%s %s\n",
453 if (p.arp.arp_op != htons(ARPOP_REQUEST)
454 && p.arp.arp_op != htons(ARPOP_REPLY))
457 if (memcmp(p.arp.arp_spa, &ip.s_addr, sizeof(struct in_addr)) == 0 &&
458 memcmp(ð_addr, &p.arp.arp_sha, ETH_ALEN) != 0) {
459 source_ip_conflict = 1;
461 if (memcmp(p.arp.arp_tpa, &ip.s_addr, sizeof(struct in_addr)) == 0 &&
462 p.arp.arp_op == htons(ARPOP_REQUEST) &&
463 memcmp(ð_addr, &p.arp.arp_tha, ETH_ALEN) != 0) {
464 target_ip_conflict = 1;
467 VDBG("state = %d, source ip conflict = %d, target ip conflict = %d\n",
468 state, source_ip_conflict, target_ip_conflict);
472 // When probing or announcing, check for source IP conflicts
473 // and other hosts doing ARP probes (target IP conflicts).
474 if (source_ip_conflict || target_ip_conflict) {
476 if (conflicts >= MAX_CONFLICTS) {
477 VDBG("%s ratelimit\n", intf);
478 timeout_ms = RATE_LIMIT_INTERVAL * 1000;
479 state = RATE_LIMIT_PROBE;
482 // restart the whole protocol
490 // If a conflict, we try to defend with a single ARP probe.
491 if (source_ip_conflict) {
492 VDBG("monitor conflict -- defending\n");
494 timeout_ms = DEFEND_INTERVAL * 1000;
502 // Well, we tried. Start over (on conflict).
503 if (source_ip_conflict) {
505 VDBG("defend conflict -- starting over\n");
507 script_av[1] = (char*)"deconfig";
508 run(script_av, intf, &ip);
510 // restart the whole protocol
518 // Invalid, should never happen. Restart the whole protocol.
519 VDBG("invalid state -- starting over\n");
528 break; // case 1 (packets arriving)
535 bb_perror_msg("%s, %s", intf, why);