src/odhcp6c.c

   1 /**
   2  * Copyright (C) 2012-2013 Steven Barth <steven@midlink.org>
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License v2 as published by
   6  * the Free Software Foundation.
   7  *
   8  * This program is distributed in the hope that it will be useful,
   9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  11  * GNU General Public License for more details.
  12  *
  13  */
  14
  15 #include <time.h>
  16 #include <errno.h>
  17 #include <ctype.h>
  18 #include <fcntl.h>
  19 #include <stdio.h>
  20 #include <stdlib.h>
  21 #include <stddef.h>
  22 #include <unistd.h>
  23 #include <syslog.h>
  24 #include <signal.h>
  25 #include <string.h>
  26 #include <strings.h>
  27 #include <stdbool.h>
  28
  29 #include <net/if.h>
  30 #include <sys/wait.h>
  31 #include <sys/syscall.h>
  32 #include <arpa/inet.h>
  33 #include <linux/if_addr.h>
  34
  35 #include "odhcp6c.h"
  36 #include "ra.h"
  37
  38 #ifdef EXT_BFD_PING
  39 #include "bfd.h"
  40 #endif
  41
  42 #ifndef IN6_IS_ADDR_UNIQUELOCAL
  43 #define IN6_IS_ADDR_UNIQUELOCAL(a) \
  44         ((((__const uint32_t *) (a))[0] & htonl (0xfe000000)) \
  45          == htonl (0xfc000000))
  46 #endif
  47
  48 static void sighandler(int signal);
  49 static int usage(void);
  50
  51 static uint8_t *state_data[_STATE_MAX] = {NULL};
  52 static size_t state_len[_STATE_MAX] = {0};
  53
  54 static volatile int do_signal = 0;
  55 static int urandom_fd = -1, allow_slaac_only = 0;
  56 static bool bound = false, release = true;
  57 static time_t last_update = 0;
  58 static char *ifname = NULL;
  59
  60 int main(_unused int argc, char* const argv[])
  61 {
  62         // Allocate ressources
  63         const char *pidfile = NULL;
  64         const char *script = "/usr/sbin/odhcp6c-update";
  65         ssize_t l;
  66         uint8_t buf[134];
  67         char *optpos;
  68         uint16_t opttype;
  69         enum odhcp6c_ia_mode ia_na_mode = IA_MODE_TRY;
  70         enum odhcp6c_ia_mode ia_pd_mode = IA_MODE_TRY;
  71         static struct in6_addr ifid = IN6ADDR_ANY_INIT;
  72         int sol_timeout = DHCPV6_SOL_MAX_RT;
  73
  74 #ifdef EXT_BFD_PING
  75         int bfd_interval = 0, bfd_loss = 3;
  76 #endif
  77
  78         bool help = false, daemonize = false;
  79         int logopt = LOG_PID;
  80         int c, request_pd = 0;
  81         while ((c = getopt(argc, argv, "S::N:P:FB:c:i:r:s:kt:hedp:")) != -1) {
  82                 switch (c) {
  83                 case 'S':
  84                         allow_slaac_only = (optarg) ? atoi(optarg) : -1;
  85                         break;
  86
  87                 case 'N':
  88                         if (!strcmp(optarg, "force")) {
  89                                 ia_na_mode = IA_MODE_FORCE;
  90                                 allow_slaac_only = -1;
  91                         } else if (!strcmp(optarg, "none")) {
  92                                 ia_na_mode = IA_MODE_NONE;
  93                         } else if (!strcmp(optarg, "try")) {
  94                                 ia_na_mode = IA_MODE_TRY;
  95                         } else{
  96                                 help = true;
  97                         }
  98                         break;
  99
 100                 case 'P':
 101                         if (allow_slaac_only >= 0 && allow_slaac_only < 10)
 102                                 allow_slaac_only = 10;
 103
 104                         request_pd = strtoul(optarg, NULL, 10);
 105                         if (request_pd == 0)
 106                                 request_pd = -1;
 107
 108                         break;
 109
 110                 case 'F':
 111                         allow_slaac_only = -1;
 112                         ia_pd_mode = IA_MODE_FORCE;
 113                         break;
 114
 115 #ifdef EXT_BFD_PING
 116                 case 'B':
 117                         bfd_interval = atoi(optarg);
 118                         break;
 119 #endif
 120
 121                 case 'c':
 122                         l = script_unhexlify(&buf[4], sizeof(buf) - 4, optarg);
 123                         if (l > 0) {
 124                                 buf[0] = 0;
 125                                 buf[1] = DHCPV6_OPT_CLIENTID;
 126                                 buf[2] = 0;
 127                                 buf[3] = l;
 128                                 odhcp6c_add_state(STATE_CLIENT_ID, buf, l + 4);
 129                         } else {
 130                                 help = true;
 131                         }
 132                         break;
 133
 134                 case 'i':
 135                         if (inet_pton(AF_INET6, optarg, &ifid) != 1)
 136                                 help = true;
 137                         break;
 138
 139                 case 'r':
 140                         optpos = optarg;
 141                         while (optpos[0]) {
 142                                 opttype = htons(strtoul(optarg, &optpos, 10));
 143                                 if (optpos == optarg)
 144                                         break;
 145                                 else if (optpos[0])
 146                                         optarg = &optpos[1];
 147                                 odhcp6c_add_state(STATE_ORO, &opttype, 2);
 148                         }
 149                         break;
 150
 151                 case 's':
 152                         script = optarg;
 153                         break;
 154
 155                 case 'k':
 156                         release = false;
 157                         break;
 158
 159                 case 't':
 160                         sol_timeout = atoi(optarg);
 161                         break;
 162
 163                 case 'e':
 164                         logopt |= LOG_PERROR;
 165                         break;
 166
 167                 case 'd':
 168                         daemonize = true;
 169                         break;
 170
 171                 case 'p':
 172                         pidfile = optarg;
 173                         break;
 174
 175                 default:
 176                         help = true;
 177                         break;
 178                 }
 179         }
 180
 181         openlog("odhcp6c", logopt, LOG_DAEMON);
 182         ifname = argv[optind];
 183
 184         if (help || !ifname)
 185                 return usage();
 186
 187         signal(SIGIO, sighandler);
 188         signal(SIGHUP, sighandler);
 189         signal(SIGINT, sighandler);
 190         signal(SIGCHLD, sighandler);
 191         signal(SIGTERM, sighandler);
 192         signal(SIGUSR1, sighandler);
 193         signal(SIGUSR2, sighandler);
 194
 195         if ((urandom_fd = open("/dev/urandom", O_CLOEXEC | O_RDONLY)) < 0 ||
 196                         init_dhcpv6(ifname, request_pd, sol_timeout) ||
 197                         ra_init(ifname, &ifid) || script_init(script, ifname)) {
 198                 syslog(LOG_ERR, "failed to initialize: %s", strerror(errno));
 199                 return 3;
 200         }
 201
 202         if (daemonize) {
 203                 openlog("odhcp6c", LOG_PID, LOG_DAEMON); // Disable LOG_PERROR
 204                 if (daemon(0, 0)) {
 205                         syslog(LOG_ERR, "Failed to daemonize: %s",
 206                                         strerror(errno));
 207                         return 4;
 208                 }
 209
 210                 char pidbuf[128];
 211                 if (!pidfile) {
 212                         snprintf(pidbuf, sizeof(pidbuf),
 213                                         "/var/run/odhcp6c.%s.pid", ifname);
 214                         pidfile = pidbuf;
 215                 }
 216
 217                 int fd = open(pidfile, O_WRONLY | O_CREAT);
 218                 if (fd >= 0) {
 219                         char buf[8];
 220                         int len = snprintf(buf, sizeof(buf), "%i\n", getpid());
 221                         write(fd, buf, len);
 222                         close(fd);
 223                 }
 224         }
 225
 226         script_call("started");
 227
 228         while (do_signal != SIGTERM) { // Main logic
 229                 odhcp6c_clear_state(STATE_SERVER_ID);
 230                 odhcp6c_clear_state(STATE_IA_NA);
 231                 odhcp6c_clear_state(STATE_IA_PD);
 232                 odhcp6c_clear_state(STATE_SNTP_IP);
 233                 odhcp6c_clear_state(STATE_SNTP_FQDN);
 234                 odhcp6c_clear_state(STATE_SIP_IP);
 235                 odhcp6c_clear_state(STATE_SIP_FQDN);
 236                 dhcpv6_set_ia_mode(ia_na_mode, ia_pd_mode);
 237                 bound = false;
 238
 239                 syslog(LOG_NOTICE, "(re)starting transaction on %s", ifname);
 240
 241                 do_signal = 0;
 242                 int mode = dhcpv6_request(DHCPV6_MSG_SOLICIT);
 243                 odhcp6c_signal_process();
 244
 245                 if (mode < 0)
 246                         continue;
 247
 248                 do {
 249                         int res = dhcpv6_request(mode == DHCPV6_STATELESS ?
 250                                         DHCPV6_MSG_INFO_REQ : DHCPV6_MSG_REQUEST);
 251
 252                         odhcp6c_signal_process();
 253                         if (res > 0)
 254                                 break;
 255                         else if (do_signal > 0) {
 256                                 mode = -1;
 257                                 break;
 258                         }
 259
 260                         mode = dhcpv6_promote_server_cand();
 261                 } while (mode > DHCPV6_UNKNOWN);
 262
 263                 if (mode < 0)
 264                         continue;
 265
 266                 switch (mode) {
 267                 case DHCPV6_STATELESS:
 268                         bound = true;
 269                         syslog(LOG_NOTICE, "entering stateless-mode on %s", ifname);
 270
 271                         while (do_signal == 0 || do_signal == SIGUSR1) {
 272                                 do_signal = 0;
 273                                 script_call("informed");
 274
 275                                 int res = dhcpv6_poll_reconfigure();
 276                                 odhcp6c_signal_process();
 277
 278                                 if (res > 0)
 279                                         continue;
 280
 281                                 if (do_signal == SIGUSR1) {
 282                                         do_signal = 0; // Acknowledged
 283                                         continue;
 284                                 } else if (do_signal > 0)
 285                                         break;
 286
 287                                 res = dhcpv6_request(DHCPV6_MSG_INFO_REQ);
 288                                 odhcp6c_signal_process();
 289                                 if (do_signal == SIGUSR1)
 290                                         continue;
 291                                 else if (res < 0)
 292                                         break;
 293                         }
 294                         break;
 295
 296                 case DHCPV6_STATEFUL:
 297                         script_call("bound");
 298                         bound = true;
 299                         syslog(LOG_NOTICE, "entering stateful-mode on %s", ifname);
 300 #ifdef EXT_BFD_PING
 301                         if (bfd_interval > 0)
 302                                 bfd_start(ifname, bfd_loss, bfd_interval);
 303 #endif
 304
 305                         while (do_signal == 0 || do_signal == SIGUSR1) {
 306                                 // Renew Cycle
 307                                 // Wait for T1 to expire or until we get a reconfigure
 308                                 int res = dhcpv6_poll_reconfigure();
 309                                 odhcp6c_signal_process();
 310                                 if (res > 0) {
 311                                         script_call("updated");
 312                                         continue;
 313                                 }
 314
 315                                 // Handle signal, if necessary
 316                                 if (do_signal == SIGUSR1)
 317                                         do_signal = 0; // Acknowledged
 318                                 else if (do_signal > 0)
 319                                         break; // Other signal type
 320
 321                                 // Send renew as T1 expired
 322                                 res = dhcpv6_request(DHCPV6_MSG_RENEW);
 323                                 odhcp6c_signal_process();
 324                                 if (res > 0) { // Renew was succesfull
 325                                         // Publish updates
 326                                         script_call("updated");
 327                                         continue; // Renew was successful
 328                                 }
 329
 330                                 odhcp6c_clear_state(STATE_SERVER_ID); // Remove binding
 331
 332                                 // If we have IAs, try rebind otherwise restart
 333                                 res = dhcpv6_request(DHCPV6_MSG_REBIND);
 334                                 odhcp6c_signal_process();
 335
 336                                 if (res > 0)
 337                                         script_call("rebound");
 338                                 else {
 339 #ifdef EXT_BFD_PING
 340                                         bfd_stop();
 341 #endif
 342                                         break;
 343                                 }
 344                         }
 345                         break;
 346
 347                 default:
 348                         break;
 349                 }
 350
 351                 size_t ia_pd_len, ia_na_len, server_id_len;
 352                 odhcp6c_get_state(STATE_IA_PD, &ia_pd_len);
 353                 odhcp6c_get_state(STATE_IA_NA, &ia_na_len);
 354                 odhcp6c_get_state(STATE_SERVER_ID, &server_id_len);
 355
 356                 // Add all prefixes to lost prefixes
 357                 bound = false;
 358                 script_call("unbound");
 359
 360                 if (server_id_len > 0 && (ia_pd_len > 0 || ia_na_len > 0) && release)
 361                         dhcpv6_request(DHCPV6_MSG_RELEASE);
 362
 363                 odhcp6c_clear_state(STATE_IA_NA);
 364                 odhcp6c_clear_state(STATE_IA_PD);
 365         }
 366
 367         script_call("stopped");
 368         return 0;
 369 }
 370
 371
 372 static int usage(void)
 373 {
 374         const char buf[] =
 375         "Usage: odhcp6c [options] <interface>\n"
 376         "\nFeature options:\n"
 377         "       -S <time>       Wait at least <time> sec for a DHCP-server (0)\n"
 378         "       -N <mode>       Mode for requesting addresses [try|force|none]\n"
 379         "       -P <length>     Request IPv6-Prefix (0 = auto)\n"
 380         "       -F              Force IPv6-Prefix\n"
 381 #ifdef EXT_BFD_PING
 382         "       -B <interval>   Enable BFD ping check\n"
 383 #endif
 384         "       -c <clientid>   Override client-ID (base-16 encoded)\n"
 385         "       -i <iface-id>   Use a custom interface identifier for RA handling\n"
 386         "       -r <options>    Options to be requested (comma-separated)\n"
 387         "       -s <script>     Status update script (/usr/sbin/odhcp6c-update)\n"
 388         "       -k              Don't send a RELEASE when stopping\n"
 389         "       -t <seconds>    Maximum timeout for DHCPv6-SOLICIT (120)\n"
 390         "\nInvocation options:\n"
 391         "       -p <pidfile>    Set pidfile (/var/run/6relayd.pid)\n"
 392         "       -d              Daemonize\n"
 393         "       -e              Write logmessages to stderr\n"
 394         //"     -v              Increase logging verbosity\n"
 395         "       -h              Show this help\n\n";
 396         write(STDERR_FILENO, buf, sizeof(buf));
 397         return 1;
 398 }
 399
 400
 401 // Don't want to pull-in librt and libpthread just for a monotonic clock...
 402 uint64_t odhcp6c_get_milli_time(void)
 403 {
 404         struct timespec t = {0, 0};
 405         syscall(SYS_clock_gettime, CLOCK_MONOTONIC, &t);
 406         return t.tv_sec * 1000 + t.tv_nsec / 1000000;
 407 }
 408
 409
 410 static uint8_t* odhcp6c_resize_state(enum odhcp6c_state state, ssize_t len)
 411 {
 412         if (len == 0)
 413                 return state_data[state] + state_len[state];
 414         else if (state_len[state] + len > 1024)
 415                 return NULL;
 416
 417         uint8_t *n = realloc(state_data[state], state_len[state] + len);
 418         if (n || state_len[state] + len == 0) {
 419                 state_data[state] = n;
 420                 n += state_len[state];
 421                 state_len[state] += len;
 422         }
 423         return n;
 424 }
 425
 426
 427 bool odhcp6c_signal_process(void)
 428 {
 429         if (do_signal == SIGIO) {
 430                 do_signal = 0;
 431                 bool ra_updated = ra_process();
 432
 433                 if (ra_link_up())
 434                         do_signal = SIGUSR2;
 435
 436                 if (ra_updated && (bound || allow_slaac_only == 0))
 437                         script_call("ra-updated"); // Immediate process urgent events
 438                 else if (ra_updated && !bound && allow_slaac_only > 0)
 439                         script_delay_call("ra-updated", allow_slaac_only);
 440
 441 #ifdef EXT_BFD_PING
 442                 bfd_receive();
 443 #endif
 444         }
 445
 446         return do_signal != 0;
 447 }
 448
 449
 450 void odhcp6c_clear_state(enum odhcp6c_state state)
 451 {
 452         state_len[state] = 0;
 453 }
 454
 455
 456 void odhcp6c_add_state(enum odhcp6c_state state, const void *data, size_t len)
 457 {
 458         uint8_t *n = odhcp6c_resize_state(state, len);
 459         if (n)
 460                 memcpy(n, data, len);
 461 }
 462
 463 void odhcp6c_insert_state(enum odhcp6c_state state, size_t offset, const void *data, size_t len)
 464 {
 465         ssize_t len_after = state_len[state] - offset;
 466         if (len_after < 0)
 467                 return;
 468
 469         uint8_t *n = odhcp6c_resize_state(state, len);
 470         if (n) {
 471                 uint8_t *sdata = state_data[state];
 472
 473                 memmove(sdata + offset + len, sdata + offset, len_after);
 474                 memcpy(sdata + offset, data, len);
 475         }
 476 }
 477
 478 size_t odhcp6c_remove_state(enum odhcp6c_state state, size_t offset, size_t len)
 479 {
 480         uint8_t *data = state_data[state];
 481         ssize_t len_after = state_len[state] - (offset + len);
 482         if (len_after < 0)
 483                 return state_len[state];
 484
 485         memmove(data + offset, data + offset + len, len_after);
 486         return state_len[state] -= len;
 487 }
 488
 489
 490 void* odhcp6c_move_state(enum odhcp6c_state state, size_t *len)
 491 {
 492         *len = state_len[state];
 493         void *data = state_data[state];
 494
 495         state_len[state] = 0;
 496         state_data[state] = NULL;
 497
 498         return data;
 499 }
 500
 501
 502 void* odhcp6c_get_state(enum odhcp6c_state state, size_t *len)
 503 {
 504         *len = state_len[state];
 505         return state_data[state];
 506 }
 507
 508
 509 struct odhcp6c_entry* odhcp6c_find_entry(enum odhcp6c_state state, const struct odhcp6c_entry *new)
 510 {
 511         size_t len, cmplen = offsetof(struct odhcp6c_entry, target) + new->length / 8;
 512         struct odhcp6c_entry *start = odhcp6c_get_state(state, &len);
 513         struct odhcp6c_entry *x = NULL;
 514
 515         for (struct odhcp6c_entry *c = start; !x && c < &start[len/sizeof(*c)]; ++c)
 516                 if (!memcmp(c, new, cmplen))
 517                         return c;
 518
 519         return NULL;
 520 }
 521
 522
 523 bool odhcp6c_update_entry_safe(enum odhcp6c_state state, struct odhcp6c_entry *new, uint32_t safe)
 524 {
 525         size_t len;
 526         struct odhcp6c_entry *x = odhcp6c_find_entry(state, new);
 527         struct odhcp6c_entry *start = odhcp6c_get_state(state, &len);
 528
 529         if (x && x->valid > new->valid && new->valid < safe)
 530                 new->valid = safe;
 531
 532         if (new->valid > 0) {
 533                 if (x) {
 534                         if (new->valid >= x->valid && new->valid - x->valid < 60 &&
 535                                         new->preferred >= x->preferred &&
 536                                         new->preferred - x->preferred < 60 &&
 537                                         x->class == new->class)
 538                                 return false;
 539                         x->valid = new->valid;
 540                         x->preferred = new->preferred;
 541                         x->t1 = new->t1;
 542                         x->t2 = new->t2;
 543                         x->class = new->class;
 544                 } else {
 545                         odhcp6c_add_state(state, new, sizeof(*new));
 546                 }
 547         } else if (x) {
 548                 odhcp6c_remove_state(state, (x - start) * sizeof(*x), sizeof(*x));
 549         }
 550         return true;
 551 }
 552
 553
 554 bool odhcp6c_update_entry(enum odhcp6c_state state, struct odhcp6c_entry *new)
 555 {
 556         return odhcp6c_update_entry_safe(state, new, 0);
 557 }
 558
 559
 560 static void odhcp6c_expire_list(enum odhcp6c_state state, uint32_t elapsed)
 561 {
 562         size_t len;
 563         struct odhcp6c_entry *start = odhcp6c_get_state(state, &len);
 564         for (struct odhcp6c_entry *c = start; c < &start[len / sizeof(*c)]; ++c) {
 565                 if (c->t1 < elapsed)
 566                         c->t1 = 0;
 567                 else if (c->t1 != UINT32_MAX)
 568                         c->t1 -= elapsed;
 569
 570                 if (c->t2 < elapsed)
 571                         c->t2 = 0;
 572                 else if (c->t2 != UINT32_MAX)
 573                         c->t2 -= elapsed;
 574
 575                 if (c->preferred < elapsed)
 576                         c->preferred = 0;
 577                 else if (c->preferred != UINT32_MAX)
 578                         c->preferred -= elapsed;
 579
 580                 if (c->valid < elapsed)
 581                         c->valid = 0;
 582                 else if (c->valid != UINT32_MAX)
 583                         c->valid -= elapsed;
 584
 585                 if (!c->valid)
 586                         odhcp6c_remove_state(state, (c - start) * sizeof(*c), sizeof(*c));
 587         }
 588 }
 589
 590
 591 void odhcp6c_expire(void)
 592 {
 593         time_t now = odhcp6c_get_milli_time() / 1000;
 594         uint32_t elapsed = (last_update > 0) ? now - last_update : 0;
 595         last_update = now;
 596
 597         odhcp6c_expire_list(STATE_RA_PREFIX, elapsed);
 598         odhcp6c_expire_list(STATE_RA_ROUTE, elapsed);
 599         odhcp6c_expire_list(STATE_RA_DNS, elapsed);
 600         odhcp6c_expire_list(STATE_IA_NA, elapsed);
 601         odhcp6c_expire_list(STATE_IA_PD, elapsed);
 602 }
 603
 604
 605 uint32_t odhcp6c_elapsed(void)
 606 {
 607         return odhcp6c_get_milli_time() / 1000 - last_update;
 608 }
 609
 610
 611 void odhcp6c_random(void *buf, size_t len)
 612 {
 613         read(urandom_fd, buf, len);
 614 }
 615
 616
 617 bool odhcp6c_is_bound(void)
 618 {
 619         return bound;
 620 }
 621
 622
 623 bool odhcp6c_addr_in_scope(const struct in6_addr *addr)
 624 {
 625         FILE *fd = fopen("/proc/net/if_inet6", "r");
 626         int len;
 627         char buf[256];
 628
 629         if (fd == NULL)
 630                 return false;
 631
 632         while (fgets(buf, sizeof(buf), fd)) {
 633                 struct in6_addr inet6_addr;
 634                 uint32_t flags, dummy;
 635                 unsigned int i;
 636                 char name[8], addr_buf[32];
 637
 638                 len = strlen(buf);
 639
 640                 if ((len <= 0) || buf[len - 1] != '\n')
 641                         return false;
 642
 643                 buf[--len] = '\0';
 644
 645                 if (sscanf(buf, "%s %x %x %x %x %s",
 646                                 addr_buf, &dummy, &dummy, &dummy, &flags, name) != 6)
 647                         return false;
 648
 649                 if (strcmp(name, ifname) ||
 650                         (flags & (IFA_F_DADFAILED | IFA_F_TENTATIVE | IFA_F_DEPRECATED)))
 651                         continue;
 652
 653                 for (i = 0; i < sizeof(addr_buf); i++) {
 654                         if (!isxdigit(addr_buf[i]) || isupper(addr_buf[i]))
 655                                 return false;
 656                 }
 657
 658                 memset(&inet6_addr, 0, sizeof(inet6_addr));
 659                 for (i = 0; i < (sizeof(addr_buf) / 2); i++) {
 660                         unsigned char byte;
 661                         static const char hex[] = "0123456789abcdef";
 662                         byte = ((index(hex, addr_buf[i * 2]) - hex) << 4) |
 663                                 (index(hex, addr_buf[i * 2 + 1]) - hex);
 664                         inet6_addr.s6_addr[i] = byte;
 665                 }
 666
 667                 if ((IN6_IS_ADDR_LINKLOCAL(&inet6_addr) == IN6_IS_ADDR_LINKLOCAL(addr)) &&
 668                         (IN6_IS_ADDR_UNIQUELOCAL(&inet6_addr) == IN6_IS_ADDR_UNIQUELOCAL(addr)))
 669                         return true;
 670         }
 671         return false;
 672 }
 673
 674 static void sighandler(int signal)
 675 {
 676         if (signal == SIGCHLD)
 677                 while (waitpid(-1, NULL, WNOHANG) > 0);
 678         else if (signal == SIGUSR1)
 679                 do_signal = SIGUSR1;
 680         else if (signal == SIGUSR2)
 681                 do_signal = SIGUSR2;
 682         else if (signal == SIGIO)
 683                 do_signal = SIGIO;
 684         else
 685                 do_signal = SIGTERM;
 686 }