networking/zcip.c

   1 /* vi: set sw=4 ts=4: */
   2 /*
   3  * RFC3927 ZeroConf IPv4 Link-Local addressing
   4  * (see <http://www.zeroconf.org/>)
   5  *
   6  * Copyright (C) 2003 by Arthur van Hoff (avh@strangeberry.com)
   7  * Copyright (C) 2004 by David Brownell
   8  *
   9  * Licensed under GPLv2 or later, see file LICENSE in this source tree.
  10  */
  11
  12 /*
  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.
  16  */
  17
  18 //#define DEBUG
  19
  20 // TODO:
  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)
  25
  26 //usage:#define zcip_trivial_usage
  27 //usage:       "[OPTIONS] IFACE SCRIPT"
  28 //usage:#define zcip_full_usage "\n\n"
  29 //usage:       "Manage a ZeroConf IPv4 link-local address\n"
  30 //usage:     "\n        -f              Run in foreground"
  31 //usage:     "\n        -q              Quit after obtaining address"
  32 //usage:     "\n        -r 169.254.x.x  Request this address first"
  33 //usage:     "\n        -l x.x.0.0      Use this range instead of 169.254"
  34 //usage:     "\n        -v              Verbose"
  35 //usage:     "\n"
  36 //usage:     "\n$LOGGING=none           Suppress logging"
  37 //usage:     "\n$LOGGING=syslog         Log to syslog"
  38 //usage:     "\n"
  39 //usage:     "\nWith no -q, runs continuously monitoring for ARP conflicts,"
  40 //usage:     "\nexits only on I/O errors (link down etc)"
  41
  42 #include "libbb.h"
  43 #include <netinet/ether.h>
  44 #include <net/if.h>
  45 #include <net/if_arp.h>
  46 #include <linux/sockios.h>
  47
  48 #include <syslog.h>
  49
  50 /* We don't need more than 32 bits of the counter */
  51 #define MONOTONIC_US() ((unsigned)monotonic_us())
  52
  53 struct arp_packet {
  54         struct ether_header eth;
  55         struct ether_arp arp;
  56 } PACKED;
  57
  58 enum {
  59 /* 169.254.0.0 */
  60         LINKLOCAL_ADDR = 0xa9fe0000,
  61
  62 /* protocol timeout parameters, specified in seconds */
  63         PROBE_WAIT = 1,
  64         PROBE_MIN = 1,
  65         PROBE_MAX = 2,
  66         PROBE_NUM = 3,
  67         MAX_CONFLICTS = 10,
  68         RATE_LIMIT_INTERVAL = 60,
  69         ANNOUNCE_WAIT = 2,
  70         ANNOUNCE_NUM = 2,
  71         ANNOUNCE_INTERVAL = 2,
  72         DEFEND_INTERVAL = 10
  73 };
  74
  75 /* States during the configuration process. */
  76 enum {
  77         PROBE = 0,
  78         RATE_LIMIT_PROBE,
  79         ANNOUNCE,
  80         MONITOR,
  81         DEFEND
  82 };
  83
  84 #define VDBG(...) do { } while (0)
  85
  86
  87 enum {
  88         sock_fd = 3
  89 };
  90
  91 struct globals {
  92         struct sockaddr saddr;
  93         struct ether_addr eth_addr;
  94         uint32_t localnet_ip;
  95 } FIX_ALIASING;
  96 #define G (*(struct globals*)&bb_common_bufsiz1)
  97 #define saddr    (G.saddr   )
  98 #define eth_addr (G.eth_addr)
  99 #define INIT_G() do { } while (0)
 100
 101
 102 /**
 103  * Pick a random link local IP address on 169.254/16, except that
 104  * the first and last 256 addresses are reserved.
 105  */
 106 static uint32_t pick_nip(void)
 107 {
 108         unsigned tmp;
 109
 110         do {
 111                 tmp = rand() & IN_CLASSB_HOST;
 112         } while (tmp > (IN_CLASSB_HOST - 0x0200));
 113         return htonl((G.localnet_ip + 0x0100) + tmp);
 114 }
 115
 116 /**
 117  * Broadcast an ARP packet.
 118  */
 119 static void arp(
 120         /* int op, - always ARPOP_REQUEST */
 121         /* const struct ether_addr *source_eth, - always &eth_addr */
 122                                         struct in_addr source_ip,
 123         const struct ether_addr *target_eth, struct in_addr target_ip)
 124 {
 125         enum { op = ARPOP_REQUEST };
 126 #define source_eth (&eth_addr)
 127
 128         struct arp_packet p;
 129         memset(&p, 0, sizeof(p));
 130
 131         // ether header
 132         p.eth.ether_type = htons(ETHERTYPE_ARP);
 133         memcpy(p.eth.ether_shost, source_eth, ETH_ALEN);
 134         memset(p.eth.ether_dhost, 0xff, ETH_ALEN);
 135
 136         // arp request
 137         p.arp.arp_hrd = htons(ARPHRD_ETHER);
 138         p.arp.arp_pro = htons(ETHERTYPE_IP);
 139         p.arp.arp_hln = ETH_ALEN;
 140         p.arp.arp_pln = 4;
 141         p.arp.arp_op = htons(op);
 142         memcpy(&p.arp.arp_sha, source_eth, ETH_ALEN);
 143         memcpy(&p.arp.arp_spa, &source_ip, sizeof(p.arp.arp_spa));
 144         memcpy(&p.arp.arp_tha, target_eth, ETH_ALEN);
 145         memcpy(&p.arp.arp_tpa, &target_ip, sizeof(p.arp.arp_tpa));
 146
 147         // send it
 148         // Even though sock_fd is already bound to saddr, just send()
 149         // won't work, because "socket is not connected"
 150         // (and connect() won't fix that, "operation not supported").
 151         // Thus we sendto() to saddr. I wonder which sockaddr
 152         // (from bind() or from sendto()?) kernel actually uses
 153         // to determine iface to emit the packet from...
 154         xsendto(sock_fd, &p, sizeof(p), &saddr, sizeof(saddr));
 155 #undef source_eth
 156 }
 157
 158 /**
 159  * Run a script.
 160  * argv[0]:intf argv[1]:script_name argv[2]:junk argv[3]:NULL
 161  */
 162 static int run(char *argv[3], const char *param, struct in_addr *ip)
 163 {
 164         int status;
 165         char *addr = addr; /* for gcc */
 166         const char *fmt = "%s %s %s" + 3;
 167
 168         argv[2] = (char*)param;
 169
 170         VDBG("%s run %s %s\n", argv[0], argv[1], argv[2]);
 171
 172         if (ip) {
 173                 addr = inet_ntoa(*ip);
 174                 xsetenv("ip", addr);
 175                 fmt -= 3;
 176         }
 177         bb_info_msg(fmt, argv[2], argv[0], addr);
 178
 179         status = spawn_and_wait(argv + 1);
 180         if (status < 0) {
 181                 bb_perror_msg("%s %s %s" + 3, argv[2], argv[0]);
 182                 return -errno;
 183         }
 184         if (status != 0)
 185                 bb_error_msg("script %s %s failed, exitcode=%d", argv[1], argv[2], status & 0xff);
 186         return status;
 187 }
 188
 189 /**
 190  * Return milliseconds of random delay, up to "secs" seconds.
 191  */
 192 static ALWAYS_INLINE unsigned random_delay_ms(unsigned secs)
 193 {
 194         return rand() % (secs * 1000);
 195 }
 196
 197 /**
 198  * main program
 199  */
 200 int zcip_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 201 int zcip_main(int argc UNUSED_PARAM, char **argv)
 202 {
 203         int state;
 204         char *r_opt;
 205         const char *l_opt = "169.254.0.0";
 206         unsigned opts;
 207
 208         // ugly trick, but I want these zeroed in one go
 209         struct {
 210                 const struct in_addr null_ip;
 211                 const struct ether_addr null_addr;
 212                 struct in_addr ip;
 213                 struct ifreq ifr;
 214                 int timeout_ms; /* must be signed */
 215                 unsigned conflicts;
 216                 unsigned nprobes;
 217                 unsigned nclaims;
 218                 int ready;
 219                 int verbose;
 220         } L;
 221 #define null_ip    (L.null_ip   )
 222 #define null_addr  (L.null_addr )
 223 #define ip         (L.ip        )
 224 #define ifr        (L.ifr       )
 225 #define timeout_ms (L.timeout_ms)
 226 #define conflicts  (L.conflicts )
 227 #define nprobes    (L.nprobes   )
 228 #define nclaims    (L.nclaims   )
 229 #define ready      (L.ready     )
 230 #define verbose    (L.verbose   )
 231
 232         memset(&L, 0, sizeof(L));
 233         INIT_G();
 234
 235 #define FOREGROUND (opts & 1)
 236 #define QUIT       (opts & 2)
 237         // parse commandline: prog [options] ifname script
 238         // exactly 2 args; -v accumulates and implies -f
 239         opt_complementary = "=2:vv:vf";
 240         opts = getopt32(argv, "fqr:l:v", &r_opt, &l_opt, &verbose);
 241 #if !BB_MMU
 242         // on NOMMU reexec early (or else we will rerun things twice)
 243         if (!FOREGROUND)
 244                 bb_daemonize_or_rexec(0 /*was: DAEMON_CHDIR_ROOT*/, argv);
 245 #endif
 246         // open an ARP socket
 247         // (need to do it before openlog to prevent openlog from taking
 248         // fd 3 (sock_fd==3))
 249         xmove_fd(xsocket(AF_PACKET, SOCK_PACKET, htons(ETH_P_ARP)), sock_fd);
 250         if (!FOREGROUND) {
 251                 // do it before all bb_xx_msg calls
 252                 openlog(applet_name, 0, LOG_DAEMON);
 253                 logmode |= LOGMODE_SYSLOG;
 254         }
 255         bb_logenv_override();
 256
 257         { // -l n.n.n.n
 258                 struct in_addr net;
 259                 if (inet_aton(l_opt, &net) == 0
 260                  || (net.s_addr & htonl(IN_CLASSB_NET)) != net.s_addr
 261                 ) {
 262                         bb_error_msg_and_die("invalid network address");
 263                 }
 264                 G.localnet_ip = ntohl(net.s_addr);
 265         }
 266         if (opts & 4) { // -r n.n.n.n
 267                 if (inet_aton(r_opt, &ip) == 0
 268                  || (ntohl(ip.s_addr) & IN_CLASSB_NET) != G.localnet_ip
 269                 ) {
 270                         bb_error_msg_and_die("invalid link address");
 271                 }
 272         }
 273         argv += optind - 1;
 274
 275         /* Now: argv[0]:junk argv[1]:intf argv[2]:script argv[3]:NULL */
 276         /* We need to make space for script argument: */
 277         argv[0] = argv[1];
 278         argv[1] = argv[2];
 279         /* Now: argv[0]:intf argv[1]:script argv[2]:junk argv[3]:NULL */
 280 #define argv_intf (argv[0])
 281
 282         xsetenv("interface", argv_intf);
 283
 284         // initialize the interface (modprobe, ifup, etc)
 285         if (run(argv, "init", NULL))
 286                 return EXIT_FAILURE;
 287
 288         // initialize saddr
 289         // saddr is: { u16 sa_family; u8 sa_data[14]; }
 290         //memset(&saddr, 0, sizeof(saddr));
 291         //TODO: are we leaving sa_family == 0 (AF_UNSPEC)?!
 292         safe_strncpy(saddr.sa_data, argv_intf, sizeof(saddr.sa_data));
 293
 294         // bind to the interface's ARP socket
 295         xbind(sock_fd, &saddr, sizeof(saddr));
 296
 297         // get the interface's ethernet address
 298         //memset(&ifr, 0, sizeof(ifr));
 299         strncpy_IFNAMSIZ(ifr.ifr_name, argv_intf);
 300         xioctl(sock_fd, SIOCGIFHWADDR, &ifr);
 301         memcpy(&eth_addr, &ifr.ifr_hwaddr.sa_data, ETH_ALEN);
 302
 303         // start with some stable ip address, either a function of
 304         // the hardware address or else the last address we used.
 305         // we are taking low-order four bytes, as top-order ones
 306         // aren't random enough.
 307         // NOTE: the sequence of addresses we try changes only
 308         // depending on when we detect conflicts.
 309         {
 310                 uint32_t t;
 311                 move_from_unaligned32(t, ((char *)&eth_addr + 2));
 312                 srand(t);
 313         }
 314         if (ip.s_addr == 0)
 315                 ip.s_addr = pick_nip();
 316
 317         // FIXME cases to handle:
 318         //  - zcip already running!
 319         //  - link already has local address... just defend/update
 320
 321         // daemonize now; don't delay system startup
 322         if (!FOREGROUND) {
 323 #if BB_MMU
 324                 bb_daemonize(0 /*was: DAEMON_CHDIR_ROOT*/);
 325 #endif
 326                 bb_info_msg("start, interface %s", argv_intf);
 327         }
 328
 329         // run the dynamic address negotiation protocol,
 330         // restarting after address conflicts:
 331         //  - start with some address we want to try
 332         //  - short random delay
 333         //  - arp probes to see if another host uses it
 334         //  - arp announcements that we're claiming it
 335         //  - use it
 336         //  - defend it, within limits
 337         // exit if:
 338         // - address is successfully obtained and -q was given:
 339         //   run "<script> config", then exit with exitcode 0
 340         // - poll error (when does this happen?)
 341         // - read error (when does this happen?)
 342         // - sendto error (in arp()) (when does this happen?)
 343         // - revents & POLLERR (link down). run "<script> deconfig" first
 344         state = PROBE;
 345         while (1) {
 346                 struct pollfd fds[1];
 347                 unsigned deadline_us;
 348                 struct arp_packet p;
 349                 int source_ip_conflict;
 350                 int target_ip_conflict;
 351
 352                 fds[0].fd = sock_fd;
 353                 fds[0].events = POLLIN;
 354                 fds[0].revents = 0;
 355
 356                 // poll, being ready to adjust current timeout
 357                 if (!timeout_ms) {
 358                         timeout_ms = random_delay_ms(PROBE_WAIT);
 359                         // FIXME setsockopt(sock_fd, SO_ATTACH_FILTER, ...) to
 360                         // make the kernel filter out all packets except
 361                         // ones we'd care about.
 362                 }
 363                 // set deadline_us to the point in time when we timeout
 364                 deadline_us = MONOTONIC_US() + timeout_ms * 1000;
 365
 366                 VDBG("...wait %d %s nprobes=%u, nclaims=%u\n",
 367                                 timeout_ms, argv_intf, nprobes, nclaims);
 368
 369                 switch (safe_poll(fds, 1, timeout_ms)) {
 370
 371                 default:
 372                         //bb_perror_msg("poll"); - done in safe_poll
 373                         return EXIT_FAILURE;
 374
 375                 // timeout
 376                 case 0:
 377                         VDBG("state = %d\n", state);
 378                         switch (state) {
 379                         case PROBE:
 380                                 // timeouts in the PROBE state mean no conflicting ARP packets
 381                                 // have been received, so we can progress through the states
 382                                 if (nprobes < PROBE_NUM) {
 383                                         nprobes++;
 384                                         VDBG("probe/%u %s@%s\n",
 385                                                         nprobes, argv_intf, inet_ntoa(ip));
 386                                         timeout_ms = PROBE_MIN * 1000;
 387                                         timeout_ms += random_delay_ms(PROBE_MAX - PROBE_MIN);
 388                                         arp(/* ARPOP_REQUEST, */
 389                                                         /* &eth_addr, */ null_ip,
 390                                                         &null_addr, ip);
 391                                 }
 392                                 else {
 393                                         // Switch to announce state.
 394                                         state = ANNOUNCE;
 395                                         nclaims = 0;
 396                                         VDBG("announce/%u %s@%s\n",
 397                                                         nclaims, argv_intf, inet_ntoa(ip));
 398                                         timeout_ms = ANNOUNCE_INTERVAL * 1000;
 399                                         arp(/* ARPOP_REQUEST, */
 400                                                         /* &eth_addr, */ ip,
 401                                                         &eth_addr, ip);
 402                                 }
 403                                 break;
 404                         case RATE_LIMIT_PROBE:
 405                                 // timeouts in the RATE_LIMIT_PROBE state mean no conflicting ARP packets
 406                                 // have been received, so we can move immediately to the announce state
 407                                 state = ANNOUNCE;
 408                                 nclaims = 0;
 409                                 VDBG("announce/%u %s@%s\n",
 410                                                 nclaims, argv_intf, inet_ntoa(ip));
 411                                 timeout_ms = ANNOUNCE_INTERVAL * 1000;
 412                                 arp(/* ARPOP_REQUEST, */
 413                                                 /* &eth_addr, */ ip,
 414                                                 &eth_addr, ip);
 415                                 break;
 416                         case ANNOUNCE:
 417                                 // timeouts in the ANNOUNCE state mean no conflicting ARP packets
 418                                 // have been received, so we can progress through the states
 419                                 if (nclaims < ANNOUNCE_NUM) {
 420                                         nclaims++;
 421                                         VDBG("announce/%u %s@%s\n",
 422                                                         nclaims, argv_intf, inet_ntoa(ip));
 423                                         timeout_ms = ANNOUNCE_INTERVAL * 1000;
 424                                         arp(/* ARPOP_REQUEST, */
 425                                                         /* &eth_addr, */ ip,
 426                                                         &eth_addr, ip);
 427                                 }
 428                                 else {
 429                                         // Switch to monitor state.
 430                                         state = MONITOR;
 431                                         // link is ok to use earlier
 432                                         // FIXME update filters
 433                                         run(argv, "config", &ip);
 434                                         ready = 1;
 435                                         conflicts = 0;
 436                                         timeout_ms = -1; // Never timeout in the monitor state.
 437
 438                                         // NOTE: all other exit paths
 439                                         // should deconfig ...
 440                                         if (QUIT)
 441                                                 return EXIT_SUCCESS;
 442                                 }
 443                                 break;
 444                         case DEFEND:
 445                                 // We won!  No ARP replies, so just go back to monitor.
 446                                 state = MONITOR;
 447                                 timeout_ms = -1;
 448                                 conflicts = 0;
 449                                 break;
 450                         default:
 451                                 // Invalid, should never happen.  Restart the whole protocol.
 452                                 state = PROBE;
 453                                 ip.s_addr = pick_nip();
 454                                 timeout_ms = 0;
 455                                 nprobes = 0;
 456                                 nclaims = 0;
 457                                 break;
 458                         } // switch (state)
 459                         break; // case 0 (timeout)
 460
 461                 // packets arriving, or link went down
 462                 case 1:
 463                         // We need to adjust the timeout in case we didn't receive
 464                         // a conflicting packet.
 465                         if (timeout_ms > 0) {
 466                                 unsigned diff = deadline_us - MONOTONIC_US();
 467                                 if ((int)(diff) < 0) {
 468                                         // Current time is greater than the expected timeout time.
 469                                         // Should never happen.
 470                                         VDBG("missed an expected timeout\n");
 471                                         timeout_ms = 0;
 472                                 } else {
 473                                         VDBG("adjusting timeout\n");
 474                                         timeout_ms = (diff / 1000) | 1; /* never 0 */
 475                                 }
 476                         }
 477
 478                         if ((fds[0].revents & POLLIN) == 0) {
 479                                 if (fds[0].revents & POLLERR) {
 480                                         // FIXME: links routinely go down;
 481                                         // this shouldn't necessarily exit.
 482                                         bb_error_msg("iface %s is down", argv_intf);
 483                                         if (ready) {
 484                                                 run(argv, "deconfig", &ip);
 485                                         }
 486                                         return EXIT_FAILURE;
 487                                 }
 488                                 continue;
 489                         }
 490
 491                         // read ARP packet
 492                         if (safe_read(sock_fd, &p, sizeof(p)) < 0) {
 493                                 bb_perror_msg_and_die(bb_msg_read_error);
 494                         }
 495                         if (p.eth.ether_type != htons(ETHERTYPE_ARP))
 496                                 continue;
 497 #ifdef DEBUG
 498                         {
 499                                 struct ether_addr *sha = (struct ether_addr *) p.arp.arp_sha;
 500                                 struct ether_addr *tha = (struct ether_addr *) p.arp.arp_tha;
 501                                 struct in_addr *spa = (struct in_addr *) p.arp.arp_spa;
 502                                 struct in_addr *tpa = (struct in_addr *) p.arp.arp_tpa;
 503                                 VDBG("%s recv arp type=%d, op=%d,\n",
 504                                         argv_intf, ntohs(p.eth.ether_type),
 505                                         ntohs(p.arp.arp_op));
 506                                 VDBG("\tsource=%s %s\n",
 507                                         ether_ntoa(sha),
 508                                         inet_ntoa(*spa));
 509                                 VDBG("\ttarget=%s %s\n",
 510                                         ether_ntoa(tha),
 511                                         inet_ntoa(*tpa));
 512                         }
 513 #endif
 514                         if (p.arp.arp_op != htons(ARPOP_REQUEST)
 515                          && p.arp.arp_op != htons(ARPOP_REPLY)
 516                         ) {
 517                                 continue;
 518                         }
 519
 520                         source_ip_conflict = 0;
 521                         target_ip_conflict = 0;
 522
 523                         if (memcmp(&p.arp.arp_sha, &eth_addr, ETH_ALEN) != 0) {
 524                                 if (memcmp(p.arp.arp_spa, &ip.s_addr, sizeof(struct in_addr))) {
 525                                         /* A probe or reply with source_ip == chosen ip */
 526                                         source_ip_conflict = 1;
 527                                 }
 528                                 if (p.arp.arp_op == htons(ARPOP_REQUEST)
 529                                  && memcmp(p.arp.arp_spa, &null_ip, sizeof(struct in_addr)) == 0
 530                                  && memcmp(p.arp.arp_tpa, &ip.s_addr, sizeof(struct in_addr)) == 0
 531                                 ) {
 532                                         /* A probe with source_ip == 0.0.0.0, target_ip == chosen ip:
 533                                          * another host trying to claim this ip!
 534                                          */
 535                                         target_ip_conflict = 1;
 536                                 }
 537                         }
 538
 539                         VDBG("state = %d, source ip conflict = %d, target ip conflict = %d\n",
 540                                 state, source_ip_conflict, target_ip_conflict);
 541                         switch (state) {
 542                         case PROBE:
 543                         case ANNOUNCE:
 544                                 // When probing or announcing, check for source IP conflicts
 545                                 // and other hosts doing ARP probes (target IP conflicts).
 546                                 if (source_ip_conflict || target_ip_conflict) {
 547                                         conflicts++;
 548                                         if (conflicts >= MAX_CONFLICTS) {
 549                                                 VDBG("%s ratelimit\n", argv_intf);
 550                                                 timeout_ms = RATE_LIMIT_INTERVAL * 1000;
 551                                                 state = RATE_LIMIT_PROBE;
 552                                         }
 553
 554                                         // restart the whole protocol
 555                                         ip.s_addr = pick_nip();
 556                                         timeout_ms = 0;
 557                                         nprobes = 0;
 558                                         nclaims = 0;
 559                                 }
 560                                 break;
 561                         case MONITOR:
 562                                 // If a conflict, we try to defend with a single ARP probe.
 563                                 if (source_ip_conflict) {
 564                                         VDBG("monitor conflict -- defending\n");
 565                                         state = DEFEND;
 566                                         timeout_ms = DEFEND_INTERVAL * 1000;
 567                                         arp(/* ARPOP_REQUEST, */
 568                                                 /* &eth_addr, */ ip,
 569                                                 &eth_addr, ip);
 570                                 }
 571                                 break;
 572                         case DEFEND:
 573                                 // Well, we tried.  Start over (on conflict).
 574                                 if (source_ip_conflict) {
 575                                         state = PROBE;
 576                                         VDBG("defend conflict -- starting over\n");
 577                                         ready = 0;
 578                                         run(argv, "deconfig", &ip);
 579
 580                                         // restart the whole protocol
 581                                         ip.s_addr = pick_nip();
 582                                         timeout_ms = 0;
 583                                         nprobes = 0;
 584                                         nclaims = 0;
 585                                 }
 586                                 break;
 587                         default:
 588                                 // Invalid, should never happen.  Restart the whole protocol.
 589                                 VDBG("invalid state -- starting over\n");
 590                                 state = PROBE;
 591                                 ip.s_addr = pick_nip();
 592                                 timeout_ms = 0;
 593                                 nprobes = 0;
 594                                 nclaims = 0;
 595                                 break;
 596                         } // switch state
 597                         break; // case 1 (packets arriving)
 598                 } // switch poll
 599         } // while (1)
 600 #undef argv_intf
 601 }