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 #define FOREGROUND (opts & 1)
75 #define QUIT (opts & 2)
78 * Pick a random link local IP address on 169.254/16, except that
79 * the first and last 256 addresses are reserved.
81 static void pick(struct in_addr *ip)
85 /* use cheaper math than lrand48() mod N */
87 tmp = (lrand48() >> 16) & IN_CLASSB_HOST;
88 } while (tmp > (IN_CLASSB_HOST - 0x0200));
89 ip->s_addr = htonl((LINKLOCAL_ADDR + 0x0100) + tmp);
92 /* TODO: we need a flag to direct bb_[p]error_msg output to stderr. */
95 * Broadcast an ARP packet.
97 static void arp(int fd, struct sockaddr *saddr, int op,
98 const struct ether_addr *source_addr, struct in_addr source_ip,
99 const struct ether_addr *target_addr, struct in_addr target_ip)
102 memset(&p, 0, sizeof(p));
105 p.hdr.ether_type = htons(ETHERTYPE_ARP);
106 memcpy(p.hdr.ether_shost, source_addr, ETH_ALEN);
107 memset(p.hdr.ether_dhost, 0xff, ETH_ALEN);
110 p.arp.arp_hrd = htons(ARPHRD_ETHER);
111 p.arp.arp_pro = htons(ETHERTYPE_IP);
112 p.arp.arp_hln = ETH_ALEN;
114 p.arp.arp_op = htons(op);
115 memcpy(&p.arp.arp_sha, source_addr, ETH_ALEN);
116 memcpy(&p.arp.arp_spa, &source_ip, sizeof(p.arp.arp_spa));
117 memcpy(&p.arp.arp_tha, target_addr, ETH_ALEN);
118 memcpy(&p.arp.arp_tpa, &target_ip, sizeof(p.arp.arp_tpa));
121 if (sendto(fd, &p, sizeof(p), 0, saddr, sizeof(*saddr)) < 0) {
122 bb_perror_msg("sendto");
125 // Currently all callers ignore errors, that's why returns are
133 static int run(const char *script, const char *arg, const char *intf, struct in_addr *ip)
138 if(1) { //always true: if (script != NULL)
139 VDBG("%s run %s %s\n", intf, script, arg);
141 char *addr = inet_ntoa(*ip);
142 setenv("ip", addr, 1);
143 bb_info_msg("%s %s %s", arg, intf, addr);
147 if (pid < 0) { // error
150 } else if (pid == 0) { // child
151 execl(script, script, arg, NULL);
152 bb_perror_msg("execl");
156 if (waitpid(pid, &status, 0) <= 0) {
160 if (WEXITSTATUS(status) != 0) {
161 bb_error_msg("script %s failed, exit=%d",
162 script, WEXITSTATUS(status));
169 bb_perror_msg("%s %s, %s", arg, intf, why);
175 * Return milliseconds of random delay, up to "secs" seconds.
177 static unsigned ATTRIBUTE_ALWAYS_INLINE ms_rdelay(unsigned secs)
179 return lrand48() % (secs * 1000);
186 /* Used to be auto variables on main() stack, but
187 * most of them were zero-inited. Moving them to bss
188 * is more space-efficient.
190 static const struct in_addr null_ip; // = { 0 };
191 static const struct ether_addr null_addr; // = { {0, 0, 0, 0, 0, 0} };
193 static struct sockaddr saddr; // memset(0);
194 static struct in_addr ip; // = { 0 };
195 static struct ifreq ifr; //memset(0);
197 static char *intf; // = NULL;
198 static char *script; // = NULL;
199 static suseconds_t timeout; // = 0; // milliseconds
200 static unsigned conflicts; // = 0;
201 static unsigned nprobes; // = 0;
202 static unsigned nclaims; // = 0;
203 static int ready; // = 0;
204 static int verbose; // = 0;
205 static int state = PROBE;
207 int zcip_main(int argc, char *argv[]);
208 int zcip_main(int argc, char *argv[])
210 struct ether_addr eth_addr;
214 // parse commandline: prog [options] ifname script
216 opt_complementary = "vv:vf"; // -v accumulates and implies -f
217 opts = getopt32(argc, argv, "fqr:v", &r_opt, &verbose);
219 /* Do it early, before all bb_xx_msg calls */
220 logmode = LOGMODE_SYSLOG;
221 openlog(applet_name, 0, LOG_DAEMON);
223 if (opts & 4) { // -r n.n.n.n
224 if (inet_aton(r_opt, &ip) == 0
225 || (ntohl(ip.s_addr) & IN_CLASSB_NET) != LINKLOCAL_ADDR
227 bb_error_msg_and_die("invalid link address");
236 setenv("interface", intf, 1);
238 // initialize the interface (modprobe, ifup, etc)
239 if (run(script, "init", intf, NULL) < 0)
243 //memset(&saddr, 0, sizeof(saddr));
244 safe_strncpy(saddr.sa_data, intf, sizeof(saddr.sa_data));
246 // open an ARP socket
247 fd = xsocket(PF_PACKET, SOCK_PACKET, htons(ETH_P_ARP));
248 // bind to the interface's ARP socket
249 xbind(fd, &saddr, sizeof(saddr));
251 // get the interface's ethernet address
252 //memset(&ifr, 0, sizeof(ifr));
253 strncpy(ifr.ifr_name, intf, sizeof(ifr.ifr_name));
254 if (ioctl(fd, SIOCGIFHWADDR, &ifr) < 0) {
255 bb_perror_msg_and_die("get ethernet address");
257 memcpy(ð_addr, &ifr.ifr_hwaddr.sa_data, ETH_ALEN);
259 // start with some stable ip address, either a function of
260 // the hardware address or else the last address we used.
261 // NOTE: the sequence of addresses we try changes only
262 // depending on when we detect conflicts.
263 // (SVID 3 bogon: who says that "short" is always 16 bits?)
264 seed48( (unsigned short*)&ifr.ifr_hwaddr.sa_data );
268 // FIXME cases to handle:
269 // - zcip already running!
270 // - link already has local address... just defend/update
272 // daemonize now; don't delay system startup
275 bb_daemonize(DAEMON_CHDIR_ROOT);
276 bb_info_msg("start, interface %s", intf);
279 // run the dynamic address negotiation protocol,
280 // restarting after address conflicts:
281 // - start with some address we want to try
282 // - short random delay
283 // - arp probes to see if another host else uses it
284 // - arp announcements that we're claiming it
286 // - defend it, within limits
288 struct pollfd fds[1];
292 int source_ip_conflict = 0;
293 int target_ip_conflict = 0;
296 fds[0].events = POLLIN;
299 // poll, being ready to adjust current timeout
301 timeout = ms_rdelay(PROBE_WAIT);
302 // FIXME setsockopt(fd, SO_ATTACH_FILTER, ...) to
303 // make the kernel filter out all packets except
304 // ones we'd care about.
306 // set tv1 to the point in time when we timeout
307 gettimeofday(&tv1, NULL);
308 tv1.tv_usec += (timeout % 1000) * 1000;
309 while (tv1.tv_usec > 1000000) {
310 tv1.tv_usec -= 1000000;
313 tv1.tv_sec += timeout / 1000;
315 VDBG("...wait %ld %s nprobes=%d, nclaims=%d\n",
316 timeout, intf, nprobes, nclaims);
317 switch (poll(fds, 1, timeout)) {
321 VDBG("state = %d\n", state);
324 // timeouts in the PROBE state mean no conflicting ARP packets
325 // have been received, so we can progress through the states
326 if (nprobes < PROBE_NUM) {
328 VDBG("probe/%d %s@%s\n",
329 nprobes, intf, inet_ntoa(ip));
330 arp(fd, &saddr, ARPOP_REQUEST,
333 timeout = PROBE_MIN * 1000;
334 timeout += ms_rdelay(PROBE_MAX
338 // Switch to announce state.
341 VDBG("announce/%d %s@%s\n",
342 nclaims, intf, inet_ntoa(ip));
343 arp(fd, &saddr, ARPOP_REQUEST,
346 timeout = ANNOUNCE_INTERVAL * 1000;
349 case RATE_LIMIT_PROBE:
350 // timeouts in the RATE_LIMIT_PROBE state mean no conflicting ARP packets
351 // have been received, so we can move immediately to the announce state
354 VDBG("announce/%d %s@%s\n",
355 nclaims, intf, inet_ntoa(ip));
356 arp(fd, &saddr, ARPOP_REQUEST,
359 timeout = ANNOUNCE_INTERVAL * 1000;
362 // timeouts in the ANNOUNCE state mean no conflicting ARP packets
363 // have been received, so we can progress through the states
364 if (nclaims < ANNOUNCE_NUM) {
366 VDBG("announce/%d %s@%s\n",
367 nclaims, intf, inet_ntoa(ip));
368 arp(fd, &saddr, ARPOP_REQUEST,
371 timeout = ANNOUNCE_INTERVAL * 1000;
374 // Switch to monitor state.
376 // link is ok to use earlier
377 // FIXME update filters
378 run(script, "config", intf, &ip);
381 timeout = -1; // Never timeout in the monitor state.
383 // NOTE: all other exit paths
384 // should deconfig ...
390 // We won! No ARP replies, so just go back to monitor.
396 // Invalid, should never happen. Restart the whole protocol.
404 break; // case 0 (timeout)
407 // We need to adjust the timeout in case we didn't receive
408 // a conflicting packet.
412 gettimeofday(&tv2, NULL);
413 if (timercmp(&tv1, &tv2, <)) {
414 // Current time is greater than the expected timeout time.
415 // Should never happen.
416 VDBG("missed an expected timeout\n");
419 VDBG("adjusting timeout\n");
420 timersub(&tv1, &tv2, &tv1);
421 timeout = 1000 * tv1.tv_sec
422 + tv1.tv_usec / 1000;
426 if ((fds[0].revents & POLLIN) == 0) {
427 if (fds[0].revents & POLLERR) {
428 // FIXME: links routinely go down;
429 // this shouldn't necessarily exit.
430 bb_error_msg("%s: poll error", intf);
432 run(script, "deconfig",
441 if (recv(fd, &p, sizeof(p), 0) < 0) {
445 if (p.hdr.ether_type != htons(ETHERTYPE_ARP))
450 struct ether_addr * sha = (struct ether_addr *) p.arp.arp_sha;
451 struct ether_addr * tha = (struct ether_addr *) p.arp.arp_tha;
452 struct in_addr * spa = (struct in_addr *) p.arp.arp_spa;
453 struct in_addr * tpa = (struct in_addr *) p.arp.arp_tpa;
454 VDBG("%s recv arp type=%d, op=%d,\n",
455 intf, ntohs(p.hdr.ether_type),
456 ntohs(p.arp.arp_op));
457 VDBG("\tsource=%s %s\n",
460 VDBG("\ttarget=%s %s\n",
465 if (p.arp.arp_op != htons(ARPOP_REQUEST)
466 && p.arp.arp_op != htons(ARPOP_REPLY))
469 if (memcmp(p.arp.arp_spa, &ip.s_addr, sizeof(struct in_addr)) == 0 &&
470 memcmp(ð_addr, &p.arp.arp_sha, ETH_ALEN) != 0) {
471 source_ip_conflict = 1;
473 if (memcmp(p.arp.arp_tpa, &ip.s_addr, sizeof(struct in_addr)) == 0 &&
474 p.arp.arp_op == htons(ARPOP_REQUEST) &&
475 memcmp(ð_addr, &p.arp.arp_tha, ETH_ALEN) != 0) {
476 target_ip_conflict = 1;
479 VDBG("state = %d, source ip conflict = %d, target ip conflict = %d\n",
480 state, source_ip_conflict, target_ip_conflict);
484 // When probing or announcing, check for source IP conflicts
485 // and other hosts doing ARP probes (target IP conflicts).
486 if (source_ip_conflict || target_ip_conflict) {
488 if (conflicts >= MAX_CONFLICTS) {
489 VDBG("%s ratelimit\n", intf);
490 timeout = RATE_LIMIT_INTERVAL * 1000;
491 state = RATE_LIMIT_PROBE;
494 // restart the whole protocol
502 // If a conflict, we try to defend with a single ARP probe.
503 if (source_ip_conflict) {
504 VDBG("monitor conflict -- defending\n");
506 timeout = DEFEND_INTERVAL * 1000;
514 // Well, we tried. Start over (on conflict).
515 if (source_ip_conflict) {
517 VDBG("defend conflict -- starting over\n");
519 run(script, "deconfig", 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);