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 <env.h>
  15 #include <log.h>
  16 #include <net.h>
  17 #include <rand.h>
  18 #include "arp.h"
  19 #include "net_rand.h"
  20
  21 /* We don't need more than 32 bits of the counter */
  22 #define MONOTONIC_MS() ((unsigned)get_timer(0) * (1000 / CONFIG_SYS_HZ))
  23
  24 enum {
  25 /* 169.254.0.0 */
  26         LINKLOCAL_ADDR = 0xa9fe0000,
  27
  28         IN_CLASSB_NET = 0xffff0000,
  29         IN_CLASSB_HOST = 0x0000ffff,
  30
  31 /* protocol timeout parameters, specified in seconds */
  32         PROBE_WAIT = 1,
  33         PROBE_MIN = 1,
  34         PROBE_MAX = 2,
  35         PROBE_NUM = 3,
  36         MAX_CONFLICTS = 10,
  37         RATE_LIMIT_INTERVAL = 60,
  38         ANNOUNCE_WAIT = 2,
  39         ANNOUNCE_NUM = 2,
  40         ANNOUNCE_INTERVAL = 2,
  41         DEFEND_INTERVAL = 10
  42 };
  43
  44 /* States during the configuration process. */
  45 static enum ll_state_t {
  46         PROBE = 0,
  47         RATE_LIMIT_PROBE,
  48         ANNOUNCE,
  49         MONITOR,
  50         DEFEND,
  51         DISABLED
  52 } state = DISABLED;
  53
  54 static struct in_addr ip;
  55 static int timeout_ms = -1;
  56 static unsigned deadline_ms;
  57 static unsigned conflicts;
  58 static unsigned nprobes;
  59 static unsigned nclaims;
  60 static int ready;
  61 static unsigned int seed;
  62
  63 static void link_local_timeout(void);
  64
  65 /**
  66  * Pick a random link local IP address on 169.254/16, except that
  67  * the first and last 256 addresses are reserved.
  68  */
  69 static struct in_addr pick(void)
  70 {
  71         unsigned tmp;
  72         struct in_addr ip;
  73
  74         do {
  75                 tmp = rand_r(&seed) & IN_CLASSB_HOST;
  76         } while (tmp > (IN_CLASSB_HOST - 0x0200));
  77         ip.s_addr = htonl((LINKLOCAL_ADDR + 0x0100) + tmp);
  78         return ip;
  79 }
  80
  81 /**
  82  * Return milliseconds of random delay, up to "secs" seconds.
  83  */
  84 static inline unsigned random_delay_ms(unsigned secs)
  85 {
  86         return rand_r(&seed) % (secs * 1000);
  87 }
  88
  89 static void configure_wait(void)
  90 {
  91         if (timeout_ms == -1)
  92                 return;
  93
  94         /* poll, being ready to adjust current timeout */
  95         if (!timeout_ms)
  96                 timeout_ms = random_delay_ms(PROBE_WAIT);
  97
  98         /* set deadline_ms to the point in time when we timeout */
  99         deadline_ms = MONOTONIC_MS() + timeout_ms;
 100
 101         debug_cond(DEBUG_DEV_PKT, "...wait %d %s nprobes=%u, nclaims=%u\n",
 102                    timeout_ms, eth_get_name(), nprobes, nclaims);
 103
 104         net_set_timeout_handler(timeout_ms, link_local_timeout);
 105 }
 106
 107 void link_local_start(void)
 108 {
 109         ip = env_get_ip("llipaddr");
 110         if (ip.s_addr != 0 &&
 111             (ntohl(ip.s_addr) & IN_CLASSB_NET) != LINKLOCAL_ADDR) {
 112                 puts("invalid link address");
 113                 net_set_state(NETLOOP_FAIL);
 114                 return;
 115         }
 116         net_netmask.s_addr = htonl(IN_CLASSB_NET);
 117
 118         seed = seed_mac();
 119         if (ip.s_addr == 0)
 120                 ip = pick();
 121
 122         state = PROBE;
 123         timeout_ms = 0;
 124         conflicts = 0;
 125         nprobes = 0;
 126         nclaims = 0;
 127         ready = 0;
 128
 129         configure_wait();
 130 }
 131
 132 static void link_local_timeout(void)
 133 {
 134         switch (state) {
 135         case PROBE:
 136                 /* timeouts in the PROBE state mean no conflicting ARP packets
 137                    have been received, so we can progress through the states */
 138                 if (nprobes < PROBE_NUM) {
 139                         struct in_addr zero_ip = {.s_addr = 0};
 140
 141                         nprobes++;
 142                         debug_cond(DEBUG_LL_STATE, "probe/%u %s@%pI4\n",
 143                                    nprobes, eth_get_name(), &ip);
 144                         arp_raw_request(zero_ip, net_null_ethaddr, ip);
 145                         timeout_ms = PROBE_MIN * 1000;
 146                         timeout_ms += random_delay_ms(PROBE_MAX - PROBE_MIN);
 147                 } else {
 148                         /* Switch to announce state */
 149                         state = ANNOUNCE;
 150                         nclaims = 0;
 151                         debug_cond(DEBUG_LL_STATE, "announce/%u %s@%pI4\n",
 152                                    nclaims, eth_get_name(), &ip);
 153                         arp_raw_request(ip, net_ethaddr, ip);
 154                         timeout_ms = ANNOUNCE_INTERVAL * 1000;
 155                 }
 156                 break;
 157         case RATE_LIMIT_PROBE:
 158                 /* timeouts in the RATE_LIMIT_PROBE state mean no conflicting
 159                    ARP packets have been received, so we can move immediately
 160                    to the announce state */
 161                 state = ANNOUNCE;
 162                 nclaims = 0;
 163                 debug_cond(DEBUG_LL_STATE, "announce/%u %s@%pI4\n",
 164                            nclaims, eth_get_name(), &ip);
 165                 arp_raw_request(ip, net_ethaddr, ip);
 166                 timeout_ms = ANNOUNCE_INTERVAL * 1000;
 167                 break;
 168         case ANNOUNCE:
 169                 /* timeouts in the ANNOUNCE state mean no conflicting ARP
 170                    packets have been received, so we can progress through
 171                    the states */
 172                 if (nclaims < ANNOUNCE_NUM) {
 173                         nclaims++;
 174                         debug_cond(DEBUG_LL_STATE, "announce/%u %s@%pI4\n",
 175                                    nclaims, eth_get_name(), &ip);
 176                         arp_raw_request(ip, net_ethaddr, ip);
 177                         timeout_ms = ANNOUNCE_INTERVAL * 1000;
 178                 } else {
 179                         /* Switch to monitor state */
 180                         state = MONITOR;
 181                         printf("Successfully assigned %pI4\n", &ip);
 182                         net_copy_ip(&net_ip, &ip);
 183                         ready = 1;
 184                         conflicts = 0;
 185                         timeout_ms = -1;
 186                         /* Never timeout in the monitor state */
 187                         net_set_timeout_handler(0, NULL);
 188
 189                         /* NOTE: all other exit paths should deconfig ... */
 190                         net_set_state(NETLOOP_SUCCESS);
 191                         return;
 192                 }
 193                 break;
 194         case DEFEND:
 195                 /* We won!  No ARP replies, so just go back to monitor */
 196                 state = MONITOR;
 197                 timeout_ms = -1;
 198                 conflicts = 0;
 199                 break;
 200         default:
 201                 /* Invalid, should never happen.  Restart the whole protocol */
 202                 state = PROBE;
 203                 ip = pick();
 204                 timeout_ms = 0;
 205                 nprobes = 0;
 206                 nclaims = 0;
 207                 break;
 208         }
 209         configure_wait();
 210 }
 211
 212 void link_local_receive_arp(struct arp_hdr *arp, int len)
 213 {
 214         int source_ip_conflict;
 215         int target_ip_conflict;
 216         struct in_addr null_ip = {.s_addr = 0};
 217
 218         if (state == DISABLED)
 219                 return;
 220
 221         /* We need to adjust the timeout in case we didn't receive a
 222            conflicting packet. */
 223         if (timeout_ms > 0) {
 224                 unsigned diff = deadline_ms - MONOTONIC_MS();
 225                 if ((int)(diff) < 0) {
 226                         /* Current time is greater than the expected timeout
 227                            time. This should never happen */
 228                         debug_cond(DEBUG_LL_STATE,
 229                                    "missed an expected timeout\n");
 230                         timeout_ms = 0;
 231                 } else {
 232                         debug_cond(DEBUG_INT_STATE, "adjusting timeout\n");
 233                         timeout_ms = diff | 1; /* never 0 */
 234                 }
 235         }
 236 #if 0
 237  /* XXX Don't bother with ethernet link just yet */
 238         if ((fds[0].revents & POLLIN) == 0) {
 239                 if (fds[0].revents & POLLERR) {
 240                         /*
 241                          * FIXME: links routinely go down;
 242                          */
 243                         bb_error_msg("iface %s is down", eth_get_name());
 244                         if (ready)
 245                                 run(argv, "deconfig", &ip);
 246                         return EXIT_FAILURE;
 247                 }
 248                 continue;
 249         }
 250 #endif
 251
 252         debug_cond(DEBUG_INT_STATE, "%s recv arp type=%d, op=%d,\n",
 253                    eth_get_name(), ntohs(arp->ar_pro),
 254                    ntohs(arp->ar_op));
 255         debug_cond(DEBUG_INT_STATE, "\tsource=%pM %pI4\n",
 256                    &arp->ar_sha,
 257                    &arp->ar_spa);
 258         debug_cond(DEBUG_INT_STATE, "\ttarget=%pM %pI4\n",
 259                    &arp->ar_tha,
 260                    &arp->ar_tpa);
 261
 262         if (arp->ar_op != htons(ARPOP_REQUEST) &&
 263             arp->ar_op != htons(ARPOP_REPLY)) {
 264                 configure_wait();
 265                 return;
 266         }
 267
 268         source_ip_conflict = 0;
 269         target_ip_conflict = 0;
 270
 271         if (memcmp(&arp->ar_spa, &ip, ARP_PLEN) == 0 &&
 272             memcmp(&arp->ar_sha, net_ethaddr, ARP_HLEN) != 0)
 273                 source_ip_conflict = 1;
 274
 275         /*
 276          * According to RFC 3927, section 2.2.1:
 277          * Check if packet is an ARP probe by checking for a null source IP
 278          * then check that target IP is equal to ours and source hw addr
 279          * is not equal to ours. This condition should cause a conflict only
 280          * during probe.
 281          */
 282         if (arp->ar_op == htons(ARPOP_REQUEST) &&
 283             memcmp(&arp->ar_spa, &null_ip, ARP_PLEN) == 0 &&
 284             memcmp(&arp->ar_tpa, &ip, ARP_PLEN) == 0 &&
 285             memcmp(&arp->ar_sha, net_ethaddr, ARP_HLEN) != 0) {
 286                 target_ip_conflict = 1;
 287         }
 288
 289         debug_cond(DEBUG_NET_PKT,
 290                    "state = %d, source ip conflict = %d, target ip conflict = "
 291                    "%d\n", state, source_ip_conflict, target_ip_conflict);
 292         switch (state) {
 293         case PROBE:
 294         case ANNOUNCE:
 295                 /* When probing or announcing, check for source IP conflicts
 296                    and other hosts doing ARP probes (target IP conflicts). */
 297                 if (source_ip_conflict || target_ip_conflict) {
 298                         conflicts++;
 299                         state = PROBE;
 300                         if (conflicts >= MAX_CONFLICTS) {
 301                                 debug("%s ratelimit\n", eth_get_name());
 302                                 timeout_ms = RATE_LIMIT_INTERVAL * 1000;
 303                                 state = RATE_LIMIT_PROBE;
 304                         }
 305
 306                         /* restart the whole protocol */
 307                         ip = pick();
 308                         timeout_ms = 0;
 309                         nprobes = 0;
 310                         nclaims = 0;
 311                 }
 312                 break;
 313         case MONITOR:
 314                 /* If a conflict, we try to defend with a single ARP probe */
 315                 if (source_ip_conflict) {
 316                         debug("monitor conflict -- defending\n");
 317                         state = DEFEND;
 318                         timeout_ms = DEFEND_INTERVAL * 1000;
 319                         arp_raw_request(ip, net_ethaddr, ip);
 320                 }
 321                 break;
 322         case DEFEND:
 323                 /* Well, we tried.  Start over (on conflict) */
 324                 if (source_ip_conflict) {
 325                         state = PROBE;
 326                         debug("defend conflict -- starting over\n");
 327                         ready = 0;
 328                         net_ip.s_addr = 0;
 329
 330                         /* restart the whole protocol */
 331                         ip = pick();
 332                         timeout_ms = 0;
 333                         nprobes = 0;
 334                         nclaims = 0;
 335                 }
 336                 break;
 337         default:
 338                 /* Invalid, should never happen.  Restart the whole protocol */
 339                 debug("invalid state -- starting over\n");
 340                 state = PROBE;
 341                 ip = pick();
 342                 timeout_ms = 0;
 343                 nprobes = 0;
 344                 nclaims = 0;
 345                 break;
 346         }
 347         configure_wait();
 348 }