net/link_local.c

   1 /*
   2  * RFC3927 ZeroConf IPv4 Link-Local addressing
   3  * (see <http://www.zeroconf.org/>)
   4  *
   5  * Copied from BusyBox - networking/zcip.c
   6  *
   7  * Copyright (C) 2003 by Arthur van Hoff (avh@strangeberry.com)
   8  * Copyright (C) 2004 by David Brownell
   9  * Copyright (C) 2010 by Joe Hershberger
  10  *
  11  * Licensed under the GPL v2 or later
  12  */
  13
  14 #include <common.h>
  15 #include <net.h>
  16 #include "arp.h"
  17 #include "net_rand.h"
  18
  19 /* We don't need more than 32 bits of the counter */
  20 #define MONOTONIC_MS() ((unsigned)get_timer(0) * (1000 / CONFIG_SYS_HZ))
  21
  22 enum {
  23 /* 169.254.0.0 */
  24         LINKLOCAL_ADDR = 0xa9fe0000,
  25
  26         IN_CLASSB_NET = 0xffff0000,
  27         IN_CLASSB_HOST = 0x0000ffff,
  28
  29 /* protocol timeout parameters, specified in seconds */
  30         PROBE_WAIT = 1,
  31         PROBE_MIN = 1,
  32         PROBE_MAX = 2,
  33         PROBE_NUM = 3,
  34         MAX_CONFLICTS = 10,
  35         RATE_LIMIT_INTERVAL = 60,
  36         ANNOUNCE_WAIT = 2,
  37         ANNOUNCE_NUM = 2,
  38         ANNOUNCE_INTERVAL = 2,
  39         DEFEND_INTERVAL = 10
  40 };
  41
  42 /* States during the configuration process. */
  43 static enum ll_state_t {
  44         PROBE = 0,
  45         RATE_LIMIT_PROBE,
  46         ANNOUNCE,
  47         MONITOR,
  48         DEFEND,
  49         DISABLED
  50 } state = DISABLED;
  51
  52 static struct in_addr ip;
  53 static int timeout_ms = -1;
  54 static unsigned deadline_ms;
  55 static unsigned conflicts;
  56 static unsigned nprobes;
  57 static unsigned nclaims;
  58 static int ready;
  59 static unsigned int seed;
  60
  61 static void link_local_timeout(void);
  62
  63 /**
  64  * Pick a random link local IP address on 169.254/16, except that
  65  * the first and last 256 addresses are reserved.
  66  */
  67 static struct in_addr pick(void)
  68 {
  69         unsigned tmp;
  70         struct in_addr ip;
  71
  72         do {
  73                 tmp = rand_r(&seed) & IN_CLASSB_HOST;
  74         } while (tmp > (IN_CLASSB_HOST - 0x0200));
  75         ip.s_addr = htonl((LINKLOCAL_ADDR + 0x0100) + tmp);
  76         return ip;
  77 }
  78
  79 /**
  80  * Return milliseconds of random delay, up to "secs" seconds.
  81  */
  82 static inline unsigned random_delay_ms(unsigned secs)
  83 {
  84         return rand_r(&seed) % (secs * 1000);
  85 }
  86
  87 static void configure_wait(void)
  88 {
  89         if (timeout_ms == -1)
  90                 return;
  91
  92         /* poll, being ready to adjust current timeout */
  93         if (!timeout_ms)
  94                 timeout_ms = random_delay_ms(PROBE_WAIT);
  95
  96         /* set deadline_ms to the point in time when we timeout */
  97         deadline_ms = MONOTONIC_MS() + timeout_ms;
  98
  99         debug_cond(DEBUG_DEV_PKT, "...wait %d %s nprobes=%u, nclaims=%u\n",
 100                    timeout_ms, eth_get_name(), nprobes, nclaims);
 101
 102         net_set_timeout_handler(timeout_ms, link_local_timeout);
 103 }
 104
 105 void link_local_start(void)
 106 {
 107         ip = getenv_ip("llipaddr");
 108         if (ip.s_addr != 0 &&
 109             (ntohl(ip.s_addr) & IN_CLASSB_NET) != LINKLOCAL_ADDR) {
 110                 puts("invalid link address");
 111                 net_set_state(NETLOOP_FAIL);
 112                 return;
 113         }
 114         net_netmask.s_addr = IN_CLASSB_NET;
 115
 116         seed = seed_mac();
 117         if (ip.s_addr == 0)
 118                 ip = pick();
 119
 120         state = PROBE;
 121         timeout_ms = 0;
 122         conflicts = 0;
 123         nprobes = 0;
 124         nclaims = 0;
 125         ready = 0;
 126
 127         configure_wait();
 128 }
 129
 130 static void link_local_timeout(void)
 131 {
 132         switch (state) {
 133         case PROBE:
 134                 /* timeouts in the PROBE state mean no conflicting ARP packets
 135                    have been received, so we can progress through the states */
 136                 if (nprobes < PROBE_NUM) {
 137                         struct in_addr zero_ip = {.s_addr = 0};
 138
 139                         nprobes++;
 140                         debug_cond(DEBUG_LL_STATE, "probe/%u %s@%pI4\n",
 141                                    nprobes, eth_get_name(), &ip);
 142                         arp_raw_request(zero_ip, net_null_ethaddr, ip);
 143                         timeout_ms = PROBE_MIN * 1000;
 144                         timeout_ms += random_delay_ms(PROBE_MAX - PROBE_MIN);
 145                 } else {
 146                         /* Switch to announce state */
 147                         state = ANNOUNCE;
 148                         nclaims = 0;
 149                         debug_cond(DEBUG_LL_STATE, "announce/%u %s@%pI4\n",
 150                                    nclaims, eth_get_name(), &ip);
 151                         arp_raw_request(ip, net_ethaddr, ip);
 152                         timeout_ms = ANNOUNCE_INTERVAL * 1000;
 153                 }
 154                 break;
 155         case RATE_LIMIT_PROBE:
 156                 /* timeouts in the RATE_LIMIT_PROBE state mean no conflicting
 157                    ARP packets have been received, so we can move immediately
 158                    to the announce state */
 159                 state = ANNOUNCE;
 160                 nclaims = 0;
 161                 debug_cond(DEBUG_LL_STATE, "announce/%u %s@%pI4\n",
 162                            nclaims, eth_get_name(), &ip);
 163                 arp_raw_request(ip, net_ethaddr, ip);
 164                 timeout_ms = ANNOUNCE_INTERVAL * 1000;
 165                 break;
 166         case ANNOUNCE:
 167                 /* timeouts in the ANNOUNCE state mean no conflicting ARP
 168                    packets have been received, so we can progress through
 169                    the states */
 170                 if (nclaims < ANNOUNCE_NUM) {
 171                         nclaims++;
 172                         debug_cond(DEBUG_LL_STATE, "announce/%u %s@%pI4\n",
 173                                    nclaims, eth_get_name(), &ip);
 174                         arp_raw_request(ip, net_ethaddr, ip);
 175                         timeout_ms = ANNOUNCE_INTERVAL * 1000;
 176                 } else {
 177                         /* Switch to monitor state */
 178                         state = MONITOR;
 179                         printf("Successfully assigned %pI4\n", &ip);
 180                         net_copy_ip(&net_ip, &ip);
 181                         ready = 1;
 182                         conflicts = 0;
 183                         timeout_ms = -1;
 184                         /* Never timeout in the monitor state */
 185                         net_set_timeout_handler(0, NULL);
 186
 187                         /* NOTE: all other exit paths should deconfig ... */
 188                         net_set_state(NETLOOP_SUCCESS);
 189                         return;
 190                 }
 191                 break;
 192         case DEFEND:
 193                 /* We won!  No ARP replies, so just go back to monitor */
 194                 state = MONITOR;
 195                 timeout_ms = -1;
 196                 conflicts = 0;
 197                 break;
 198         default:
 199                 /* Invalid, should never happen.  Restart the whole protocol */
 200                 state = PROBE;
 201                 ip = pick();
 202                 timeout_ms = 0;
 203                 nprobes = 0;
 204                 nclaims = 0;
 205                 break;
 206         }
 207         configure_wait();
 208 }
 209
 210 void link_local_receive_arp(struct arp_hdr *arp, int len)
 211 {
 212         int source_ip_conflict;
 213         int target_ip_conflict;
 214         struct in_addr null_ip = {.s_addr = 0};
 215
 216         if (state == DISABLED)
 217                 return;
 218
 219         /* We need to adjust the timeout in case we didn't receive a
 220            conflicting packet. */
 221         if (timeout_ms > 0) {
 222                 unsigned diff = deadline_ms - MONOTONIC_MS();
 223                 if ((int)(diff) < 0) {
 224                         /* Current time is greater than the expected timeout
 225                            time. This should never happen */
 226                         debug_cond(DEBUG_LL_STATE,
 227                                    "missed an expected timeout\n");
 228                         timeout_ms = 0;
 229                 } else {
 230                         debug_cond(DEBUG_INT_STATE, "adjusting timeout\n");
 231                         timeout_ms = diff | 1; /* never 0 */
 232                 }
 233         }
 234 #if 0
 235  /* XXX Don't bother with ethernet link just yet */
 236         if ((fds[0].revents & POLLIN) == 0) {
 237                 if (fds[0].revents & POLLERR) {
 238                         /*
 239                          * FIXME: links routinely go down;
 240                          */
 241                         bb_error_msg("iface %s is down", eth_get_name());
 242                         if (ready)
 243                                 run(argv, "deconfig", &ip);
 244                         return EXIT_FAILURE;
 245                 }
 246                 continue;
 247         }
 248 #endif
 249
 250         debug_cond(DEBUG_INT_STATE, "%s recv arp type=%d, op=%d,\n",
 251                    eth_get_name(), ntohs(arp->ar_pro),
 252                    ntohs(arp->ar_op));
 253         debug_cond(DEBUG_INT_STATE, "\tsource=%pM %pI4\n",
 254                    &arp->ar_sha,
 255                    &arp->ar_spa);
 256         debug_cond(DEBUG_INT_STATE, "\ttarget=%pM %pI4\n",
 257                    &arp->ar_tha,
 258                    &arp->ar_tpa);
 259
 260         if (arp->ar_op != htons(ARPOP_REQUEST) &&
 261             arp->ar_op != htons(ARPOP_REPLY)) {
 262                 configure_wait();
 263                 return;
 264         }
 265
 266         source_ip_conflict = 0;
 267         target_ip_conflict = 0;
 268
 269         if (memcmp(&arp->ar_spa, &ip, ARP_PLEN) == 0 &&
 270             memcmp(&arp->ar_sha, net_ethaddr, ARP_HLEN) != 0)
 271                 source_ip_conflict = 1;
 272
 273         /*
 274          * According to RFC 3927, section 2.2.1:
 275          * Check if packet is an ARP probe by checking for a null source IP
 276          * then check that target IP is equal to ours and source hw addr
 277          * is not equal to ours. This condition should cause a conflict only
 278          * during probe.
 279          */
 280         if (arp->ar_op == htons(ARPOP_REQUEST) &&
 281             memcmp(&arp->ar_spa, &null_ip, ARP_PLEN) == 0 &&
 282             memcmp(&arp->ar_tpa, &ip, ARP_PLEN) == 0 &&
 283             memcmp(&arp->ar_sha, net_ethaddr, ARP_HLEN) != 0) {
 284                 target_ip_conflict = 1;
 285         }
 286
 287         debug_cond(DEBUG_NET_PKT,
 288                    "state = %d, source ip conflict = %d, target ip conflict = "
 289                    "%d\n", state, source_ip_conflict, target_ip_conflict);
 290         switch (state) {
 291         case PROBE:
 292         case ANNOUNCE:
 293                 /* When probing or announcing, check for source IP conflicts
 294                    and other hosts doing ARP probes (target IP conflicts). */
 295                 if (source_ip_conflict || target_ip_conflict) {
 296                         conflicts++;
 297                         state = PROBE;
 298                         if (conflicts >= MAX_CONFLICTS) {
 299                                 debug("%s ratelimit\n", eth_get_name());
 300                                 timeout_ms = RATE_LIMIT_INTERVAL * 1000;
 301                                 state = RATE_LIMIT_PROBE;
 302                         }
 303
 304                         /* restart the whole protocol */
 305                         ip = pick();
 306                         timeout_ms = 0;
 307                         nprobes = 0;
 308                         nclaims = 0;
 309                 }
 310                 break;
 311         case MONITOR:
 312                 /* If a conflict, we try to defend with a single ARP probe */
 313                 if (source_ip_conflict) {
 314                         debug("monitor conflict -- defending\n");
 315                         state = DEFEND;
 316                         timeout_ms = DEFEND_INTERVAL * 1000;
 317                         arp_raw_request(ip, net_ethaddr, ip);
 318                 }
 319                 break;
 320         case DEFEND:
 321                 /* Well, we tried.  Start over (on conflict) */
 322                 if (source_ip_conflict) {
 323                         state = PROBE;
 324                         debug("defend conflict -- starting over\n");
 325                         ready = 0;
 326                         net_ip.s_addr = 0;
 327
 328                         /* restart the whole protocol */
 329                         ip = pick();
 330                         timeout_ms = 0;
 331                         nprobes = 0;
 332                         nclaims = 0;
 333                 }
 334                 break;
 335         default:
 336                 /* Invalid, should never happen.  Restart the whole protocol */
 337                 debug("invalid state -- starting over\n");
 338                 state = PROBE;
 339                 ip = pick();
 340                 timeout_ms = 0;
 341                 nprobes = 0;
 342                 nclaims = 0;
 343                 break;
 344         }
 345         configure_wait();
 346 }