1 /* $OpenBSD: res_send_async.c,v 1.36 2017/03/15 15:54:41 deraadt Exp $ */ 2 /* 3 * Copyright (c) 2012 Eric Faurot <eric@openbsd.org> 4 * 5 * Permission to use, copy, modify, and distribute this software for any 6 * purpose with or without fee is hereby granted, provided that the above 7 * copyright notice and this permission notice appear in all copies. 8 * 9 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES 10 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF 11 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR 12 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES 13 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN 14 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF 15 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. 16 */ 17 18 #include <sys/types.h> 19 #include <sys/socket.h> 20 #include <sys/uio.h> 21 #include <netinet/in.h> 22 #include <arpa/nameser.h> 23 #include <netdb.h> 24 25 #include <asr.h> 26 #include <errno.h> 27 #include <fcntl.h> 28 #include <poll.h> 29 #include <resolv.h> /* for res_random */ 30 #include <stdlib.h> 31 #include <string.h> 32 #include <unistd.h> 33 34 #include "asr_private.h" 35 36 #define OP_QUERY (0) 37 38 static int res_send_async_run(struct asr_query *, struct asr_result *); 39 static int sockaddr_connect(const struct sockaddr *, int); 40 static int udp_send(struct asr_query *); 41 static int udp_recv(struct asr_query *); 42 static int tcp_write(struct asr_query *); 43 static int tcp_read(struct asr_query *); 44 static int validate_packet(struct asr_query *); 45 static int setup_query(struct asr_query *, const char *, const char *, int, int); 46 static int ensure_ibuf(struct asr_query *, size_t); 47 static int iter_ns(struct asr_query *); 48 49 #define AS_NS_SA(p) ((p)->as_ctx->ac_ns[(p)->as.dns.nsidx - 1]) 50 51 52 struct asr_query * 53 res_send_async(const unsigned char *buf, int buflen, void *asr) 54 { 55 struct asr_ctx *ac; 56 struct asr_query *as; 57 struct asr_unpack p; 58 struct asr_dns_header h; 59 struct asr_dns_query q; 60 61 DPRINT_PACKET("asr: res_send_async()", buf, buflen); 62 63 ac = _asr_use_resolver(asr); 64 if ((as = _asr_async_new(ac, ASR_SEND)) == NULL) { 65 _asr_ctx_unref(ac); 66 return (NULL); /* errno set */ 67 } 68 as->as_run = res_send_async_run; 69 70 as->as_flags |= ASYNC_EXTOBUF; 71 as->as.dns.obuf = (unsigned char *)buf; 72 as->as.dns.obuflen = buflen; 73 as->as.dns.obufsize = buflen; 74 75 _asr_unpack_init(&p, buf, buflen); 76 _asr_unpack_header(&p, &h); 77 _asr_unpack_query(&p, &q); 78 if (p.err) { 79 errno = EINVAL; 80 goto err; 81 } 82 as->as.dns.reqid = h.id; 83 as->as.dns.type = q.q_type; 84 as->as.dns.class = q.q_class; 85 as->as.dns.dname = strdup(q.q_dname); 86 if (as->as.dns.dname == NULL) 87 goto err; /* errno set */ 88 89 _asr_ctx_unref(ac); 90 return (as); 91 err: 92 if (as) 93 _asr_async_free(as); 94 _asr_ctx_unref(ac); 95 return (NULL); 96 } 97 DEF_WEAK(res_send_async); 98 99 /* 100 * Unlike res_query(), this version will actually return the packet 101 * if it has received a valid one (errno == 0) even if h_errno is 102 * not NETDB_SUCCESS. So the packet *must* be freed if necessary. 103 */ 104 struct asr_query * 105 res_query_async(const char *name, int class, int type, void *asr) 106 { 107 struct asr_ctx *ac; 108 struct asr_query *as; 109 110 DPRINT("asr: res_query_async(\"%s\", %i, %i)\n", name, class, type); 111 112 ac = _asr_use_resolver(asr); 113 as = _res_query_async_ctx(name, class, type, ac); 114 _asr_ctx_unref(ac); 115 116 return (as); 117 } 118 DEF_WEAK(res_query_async); 119 120 struct asr_query * 121 _res_query_async_ctx(const char *name, int class, int type, struct asr_ctx *a_ctx) 122 { 123 struct asr_query *as; 124 125 DPRINT("asr: res_query_async_ctx(\"%s\", %i, %i)\n", name, class, type); 126 127 if ((as = _asr_async_new(a_ctx, ASR_SEND)) == NULL) 128 return (NULL); /* errno set */ 129 as->as_run = res_send_async_run; 130 131 /* This adds a "." to name if it doesn't already has one. 132 * That's how res_query() behaves (through res_mkquery"). 133 */ 134 if (setup_query(as, name, NULL, class, type) == -1) 135 goto err; /* errno set */ 136 137 return (as); 138 139 err: 140 if (as) 141 _asr_async_free(as); 142 143 return (NULL); 144 } 145 146 static int 147 res_send_async_run(struct asr_query *as, struct asr_result *ar) 148 { 149 next: 150 switch (as->as_state) { 151 152 case ASR_STATE_INIT: 153 154 if (as->as_ctx->ac_nscount == 0) { 155 ar->ar_errno = ECONNREFUSED; 156 async_set_state(as, ASR_STATE_HALT); 157 break; 158 } 159 160 async_set_state(as, ASR_STATE_NEXT_NS); 161 break; 162 163 case ASR_STATE_NEXT_NS: 164 165 if (iter_ns(as) == -1) { 166 ar->ar_errno = ETIMEDOUT; 167 async_set_state(as, ASR_STATE_HALT); 168 break; 169 } 170 171 if (as->as_ctx->ac_options & RES_USEVC || 172 as->as.dns.obuflen > PACKETSZ) 173 async_set_state(as, ASR_STATE_TCP_WRITE); 174 else 175 async_set_state(as, ASR_STATE_UDP_SEND); 176 break; 177 178 case ASR_STATE_UDP_SEND: 179 180 if (udp_send(as) == -1) { 181 async_set_state(as, ASR_STATE_NEXT_NS); 182 break; 183 } 184 async_set_state(as, ASR_STATE_UDP_RECV); 185 ar->ar_cond = ASR_WANT_READ; 186 ar->ar_fd = as->as_fd; 187 ar->ar_timeout = as->as_timeout; 188 return (ASYNC_COND); 189 break; 190 191 case ASR_STATE_UDP_RECV: 192 193 if (udp_recv(as) == -1) { 194 if (errno == ENOMEM) { 195 ar->ar_errno = errno; 196 async_set_state(as, ASR_STATE_HALT); 197 break; 198 } 199 if (errno != EOVERFLOW) { 200 /* Fail or timeout */ 201 async_set_state(as, ASR_STATE_NEXT_NS); 202 break; 203 } 204 if (as->as_ctx->ac_options & RES_IGNTC) 205 async_set_state(as, ASR_STATE_PACKET); 206 else 207 async_set_state(as, ASR_STATE_TCP_WRITE); 208 } else 209 async_set_state(as, ASR_STATE_PACKET); 210 break; 211 212 case ASR_STATE_TCP_WRITE: 213 214 switch (tcp_write(as)) { 215 case -1: /* fail or timeout */ 216 async_set_state(as, ASR_STATE_NEXT_NS); 217 break; 218 case 0: 219 async_set_state(as, ASR_STATE_TCP_READ); 220 ar->ar_cond = ASR_WANT_READ; 221 ar->ar_fd = as->as_fd; 222 ar->ar_timeout = as->as_timeout; 223 return (ASYNC_COND); 224 case 1: 225 ar->ar_cond = ASR_WANT_WRITE; 226 ar->ar_fd = as->as_fd; 227 ar->ar_timeout = as->as_timeout; 228 return (ASYNC_COND); 229 } 230 break; 231 232 case ASR_STATE_TCP_READ: 233 234 switch (tcp_read(as)) { 235 case -1: /* Fail or timeout */ 236 if (errno == ENOMEM) { 237 ar->ar_errno = errno; 238 async_set_state(as, ASR_STATE_HALT); 239 } else 240 async_set_state(as, ASR_STATE_NEXT_NS); 241 break; 242 case 0: 243 async_set_state(as, ASR_STATE_PACKET); 244 break; 245 case 1: 246 ar->ar_cond = ASR_WANT_READ; 247 ar->ar_fd = as->as_fd; 248 ar->ar_timeout = as->as_timeout; 249 return (ASYNC_COND); 250 } 251 break; 252 253 case ASR_STATE_PACKET: 254 255 memmove(&ar->ar_ns, AS_NS_SA(as), AS_NS_SA(as)->sa_len); 256 ar->ar_datalen = as->as.dns.ibuflen; 257 ar->ar_data = as->as.dns.ibuf; 258 as->as.dns.ibuf = NULL; 259 ar->ar_errno = 0; 260 ar->ar_rcode = as->as.dns.rcode; 261 async_set_state(as, ASR_STATE_HALT); 262 break; 263 264 case ASR_STATE_HALT: 265 266 if (ar->ar_errno) { 267 ar->ar_h_errno = TRY_AGAIN; 268 ar->ar_count = 0; 269 ar->ar_datalen = -1; 270 ar->ar_data = NULL; 271 } else if (as->as.dns.ancount) { 272 ar->ar_h_errno = NETDB_SUCCESS; 273 ar->ar_count = as->as.dns.ancount; 274 } else { 275 ar->ar_count = 0; 276 switch (as->as.dns.rcode) { 277 case NXDOMAIN: 278 ar->ar_h_errno = HOST_NOT_FOUND; 279 break; 280 case SERVFAIL: 281 ar->ar_h_errno = TRY_AGAIN; 282 break; 283 case NOERROR: 284 ar->ar_h_errno = NO_DATA; 285 break; 286 default: 287 ar->ar_h_errno = NO_RECOVERY; 288 } 289 } 290 return (ASYNC_DONE); 291 292 default: 293 294 ar->ar_errno = EOPNOTSUPP; 295 ar->ar_h_errno = NETDB_INTERNAL; 296 async_set_state(as, ASR_STATE_HALT); 297 break; 298 } 299 goto next; 300 } 301 302 static int 303 sockaddr_connect(const struct sockaddr *sa, int socktype) 304 { 305 int errno_save, sock; 306 307 if ((sock = socket(sa->sa_family, 308 socktype | SOCK_NONBLOCK | SOCK_DNS, 0)) == -1) 309 goto fail; 310 311 if (connect(sock, sa, sa->sa_len) == -1) { 312 /* 313 * In the TCP case, the caller will be asked to poll for 314 * POLLOUT so that we start writing the packet in tcp_write() 315 * when the connection is established, or fail there on error. 316 */ 317 if (errno == EINPROGRESS) 318 return (sock); 319 goto fail; 320 } 321 322 return (sock); 323 324 fail: 325 326 if (sock != -1) { 327 errno_save = errno; 328 close(sock); 329 errno = errno_save; 330 } 331 332 return (-1); 333 } 334 335 /* 336 * Prepare the DNS packet for the query type "type", class "class" and domain 337 * name created by the concatenation on "name" and "dom". 338 * Return 0 on success, set errno and return -1 on error. 339 */ 340 static int 341 setup_query(struct asr_query *as, const char *name, const char *dom, 342 int class, int type) 343 { 344 struct asr_pack p; 345 struct asr_dns_header h; 346 char fqdn[MAXDNAME]; 347 char dname[MAXDNAME]; 348 349 if (as->as_flags & ASYNC_EXTOBUF) { 350 errno = EINVAL; 351 DPRINT("attempting to write in user packet"); 352 return (-1); 353 } 354 355 if (_asr_make_fqdn(name, dom, fqdn, sizeof(fqdn)) > sizeof(fqdn)) { 356 errno = EINVAL; 357 DPRINT("asr_make_fqdn: name too long\n"); 358 return (-1); 359 } 360 361 if (_asr_dname_from_fqdn(fqdn, dname, sizeof(dname)) == -1) { 362 errno = EINVAL; 363 DPRINT("asr_dname_from_fqdn: invalid\n"); 364 return (-1); 365 } 366 367 if (as->as.dns.obuf == NULL) { 368 as->as.dns.obufsize = PACKETSZ; 369 as->as.dns.obuf = malloc(as->as.dns.obufsize); 370 if (as->as.dns.obuf == NULL) 371 return (-1); /* errno set */ 372 } 373 as->as.dns.obuflen = 0; 374 375 memset(&h, 0, sizeof h); 376 h.id = res_randomid(); 377 if (as->as_ctx->ac_options & RES_RECURSE) 378 h.flags |= RD_MASK; 379 h.qdcount = 1; 380 if (as->as_ctx->ac_options & (RES_USE_EDNS0 | RES_USE_DNSSEC)) 381 h.arcount = 1; 382 383 _asr_pack_init(&p, as->as.dns.obuf, as->as.dns.obufsize); 384 _asr_pack_header(&p, &h); 385 _asr_pack_query(&p, type, class, dname); 386 if (as->as_ctx->ac_options & (RES_USE_EDNS0 | RES_USE_DNSSEC)) 387 _asr_pack_edns0(&p, MAXPACKETSZ, 388 as->as_ctx->ac_options & RES_USE_DNSSEC); 389 if (p.err) { 390 DPRINT("error packing query"); 391 errno = EINVAL; 392 return (-1); 393 } 394 395 /* Remember the parameters. */ 396 as->as.dns.reqid = h.id; 397 as->as.dns.type = type; 398 as->as.dns.class = class; 399 if (as->as.dns.dname) 400 free(as->as.dns.dname); 401 as->as.dns.dname = strdup(dname); 402 if (as->as.dns.dname == NULL) { 403 DPRINT("strdup"); 404 return (-1); /* errno set */ 405 } 406 as->as.dns.obuflen = p.offset; 407 408 DPRINT_PACKET("asr_setup_query", as->as.dns.obuf, as->as.dns.obuflen); 409 410 return (0); 411 } 412 413 /* 414 * Create a connect UDP socket and send the output packet. 415 * 416 * Return 0 on success, or -1 on error (errno set). 417 */ 418 static int 419 udp_send(struct asr_query *as) 420 { 421 ssize_t n; 422 int save_errno; 423 #ifdef DEBUG 424 char buf[256]; 425 #endif 426 427 DPRINT("asr: [%p] connecting to %s UDP\n", as, 428 _asr_print_sockaddr(AS_NS_SA(as), buf, sizeof buf)); 429 430 as->as_fd = sockaddr_connect(AS_NS_SA(as), SOCK_DGRAM); 431 if (as->as_fd == -1) 432 return (-1); /* errno set */ 433 434 n = send(as->as_fd, as->as.dns.obuf, as->as.dns.obuflen, 0); 435 if (n == -1) { 436 save_errno = errno; 437 close(as->as_fd); 438 errno = save_errno; 439 as->as_fd = -1; 440 return (-1); 441 } 442 443 return (0); 444 } 445 446 /* 447 * Try to receive a valid packet from the current UDP socket. 448 * 449 * Return 0 if a full packet could be read, or -1 on error (errno set). 450 */ 451 static int 452 udp_recv(struct asr_query *as) 453 { 454 ssize_t n; 455 int save_errno; 456 457 if (ensure_ibuf(as, MAXPACKETSZ) == -1) { 458 save_errno = errno; 459 close(as->as_fd); 460 errno = save_errno; 461 as->as_fd = -1; 462 return (-1); 463 } 464 465 n = recv(as->as_fd, as->as.dns.ibuf, as->as.dns.ibufsize, 0); 466 save_errno = errno; 467 close(as->as_fd); 468 errno = save_errno; 469 as->as_fd = -1; 470 if (n == -1) 471 return (-1); 472 473 as->as.dns.ibuflen = n; 474 475 DPRINT_PACKET("asr_udp_recv()", as->as.dns.ibuf, as->as.dns.ibuflen); 476 477 if (validate_packet(as) == -1) 478 return (-1); /* errno set */ 479 480 return (0); 481 } 482 483 /* 484 * Write the output packet to the TCP socket. 485 * 486 * Return 0 when all bytes have been sent, 1 there is no buffer space on the 487 * socket or it is not connected yet, or -1 on error (errno set). 488 */ 489 static int 490 tcp_write(struct asr_query *as) 491 { 492 struct msghdr msg; 493 struct iovec iov[2]; 494 uint16_t len; 495 ssize_t n; 496 size_t offset; 497 int i; 498 #ifdef DEBUG 499 char buf[256]; 500 #endif 501 502 /* First try to connect if not already */ 503 if (as->as_fd == -1) { 504 DPRINT("asr: [%p] connecting to %s TCP\n", as, 505 _asr_print_sockaddr(AS_NS_SA(as), buf, sizeof buf)); 506 as->as_fd = sockaddr_connect(AS_NS_SA(as), SOCK_STREAM); 507 if (as->as_fd == -1) 508 return (-1); /* errno set */ 509 as->as.dns.datalen = 0; /* bytes sent */ 510 return (1); 511 } 512 513 i = 0; 514 515 /* Prepend de packet length if not sent already. */ 516 if (as->as.dns.datalen < sizeof(len)) { 517 offset = 0; 518 len = htons(as->as.dns.obuflen); 519 iov[i].iov_base = (char *)(&len) + as->as.dns.datalen; 520 iov[i].iov_len = sizeof(len) - as->as.dns.datalen; 521 i++; 522 } else 523 offset = as->as.dns.datalen - sizeof(len); 524 525 iov[i].iov_base = as->as.dns.obuf + offset; 526 iov[i].iov_len = as->as.dns.obuflen - offset; 527 i++; 528 529 memset(&msg, 0, sizeof msg); 530 msg.msg_iov = iov; 531 msg.msg_iovlen = i; 532 533 send_again: 534 n = sendmsg(as->as_fd, &msg, MSG_NOSIGNAL); 535 if (n == -1) { 536 if (errno == EINTR) 537 goto send_again; 538 goto close; /* errno set */ 539 } 540 541 as->as.dns.datalen += n; 542 543 if (as->as.dns.datalen == as->as.dns.obuflen + sizeof(len)) { 544 /* All sent. Prepare for TCP read */ 545 as->as.dns.datalen = 0; 546 return (0); 547 } 548 549 /* More data to write */ 550 return (1); 551 552 close: 553 close(as->as_fd); 554 as->as_fd = -1; 555 return (-1); 556 } 557 558 /* 559 * Try to read a valid packet from the current TCP socket. 560 * 561 * Return 0 if a full packet could be read, 1 if more data is needed and the 562 * socket must be read again, or -1 on error (errno set). 563 */ 564 static int 565 tcp_read(struct asr_query *as) 566 { 567 ssize_t n; 568 size_t offset, len; 569 char *pos; 570 int save_errno, nfds; 571 struct pollfd pfd; 572 573 /* We must read the packet len first */ 574 if (as->as.dns.datalen < sizeof(as->as.dns.pktlen)) { 575 576 pos = (char *)(&as->as.dns.pktlen) + as->as.dns.datalen; 577 len = sizeof(as->as.dns.pktlen) - as->as.dns.datalen; 578 579 n = read(as->as_fd, pos, len); 580 if (n == -1) 581 goto close; /* errno set */ 582 583 as->as.dns.datalen += n; 584 if (as->as.dns.datalen < sizeof(as->as.dns.pktlen)) 585 return (1); /* need more data */ 586 587 as->as.dns.ibuflen = ntohs(as->as.dns.pktlen); 588 if (ensure_ibuf(as, as->as.dns.ibuflen) == -1) 589 goto close; /* errno set */ 590 591 pfd.fd = as->as_fd; 592 pfd.events = POLLIN; 593 poll_again: 594 nfds = poll(&pfd, 1, 0); 595 if (nfds == -1) { 596 if (errno == EINTR) 597 goto poll_again; 598 goto close; /* errno set */ 599 } 600 if (nfds == 0) 601 return (1); /* no more data available */ 602 } 603 604 offset = as->as.dns.datalen - sizeof(as->as.dns.pktlen); 605 pos = as->as.dns.ibuf + offset; 606 len = as->as.dns.ibuflen - offset; 607 608 read_again: 609 n = read(as->as_fd, pos, len); 610 if (n == -1) { 611 if (errno == EINTR) 612 goto read_again; 613 goto close; /* errno set */ 614 } 615 if (n == 0) { 616 errno = ECONNRESET; 617 goto close; 618 } 619 as->as.dns.datalen += n; 620 621 /* See if we got all the advertised bytes. */ 622 if (as->as.dns.datalen != as->as.dns.ibuflen + sizeof(as->as.dns.pktlen)) 623 return (1); 624 625 DPRINT_PACKET("asr_tcp_read()", as->as.dns.ibuf, as->as.dns.ibuflen); 626 627 if (validate_packet(as) == -1) 628 goto close; /* errno set */ 629 630 errno = 0; 631 close: 632 save_errno = errno; 633 close(as->as_fd); 634 errno = save_errno; 635 as->as_fd = -1; 636 return (errno ? -1 : 0); 637 } 638 639 /* 640 * Make sure the input buffer is at least "n" bytes long, and allocate or 641 * extend it if necessary. Return 0 on success, or set errno and return -1. 642 */ 643 static int 644 ensure_ibuf(struct asr_query *as, size_t n) 645 { 646 char *t; 647 648 if (as->as.dns.ibufsize >= n) 649 return (0); 650 651 t = recallocarray(as->as.dns.ibuf, as->as.dns.ibufsize, n, 1); 652 if (t == NULL) 653 return (-1); /* errno set */ 654 as->as.dns.ibuf = t; 655 as->as.dns.ibufsize = n; 656 657 return (0); 658 } 659 660 /* 661 * Check if the received packet is valid. 662 * Return 0 on success, or set errno and return -1. 663 */ 664 static int 665 validate_packet(struct asr_query *as) 666 { 667 struct asr_unpack p; 668 struct asr_dns_header h; 669 struct asr_dns_query q; 670 struct asr_dns_rr rr; 671 int r; 672 673 _asr_unpack_init(&p, as->as.dns.ibuf, as->as.dns.ibuflen); 674 675 _asr_unpack_header(&p, &h); 676 if (p.err) 677 goto inval; 678 679 if (h.id != as->as.dns.reqid) { 680 DPRINT("incorrect reqid\n"); 681 goto inval; 682 } 683 if (h.qdcount != 1) 684 goto inval; 685 /* Should be zero, we could allow this */ 686 if ((h.flags & Z_MASK) != 0) 687 goto inval; 688 /* Actually, it depends on the request but we only use OP_QUERY */ 689 if (OPCODE(h.flags) != OP_QUERY) 690 goto inval; 691 /* Must be a response */ 692 if ((h.flags & QR_MASK) == 0) 693 goto inval; 694 695 as->as.dns.rcode = RCODE(h.flags); 696 as->as.dns.ancount = h.ancount; 697 698 _asr_unpack_query(&p, &q); 699 if (p.err) 700 goto inval; 701 702 if (q.q_type != as->as.dns.type || 703 q.q_class != as->as.dns.class || 704 strcasecmp(q.q_dname, as->as.dns.dname)) { 705 DPRINT("incorrect type/class/dname '%s' != '%s'\n", 706 q.q_dname, as->as.dns.dname); 707 goto inval; 708 } 709 710 /* Check for truncation */ 711 if (h.flags & TC_MASK && !(as->as_ctx->ac_options & RES_IGNTC)) { 712 DPRINT("truncated\n"); 713 errno = EOVERFLOW; 714 return (-1); 715 } 716 717 /* Validate the rest of the packet */ 718 for (r = h.ancount + h.nscount + h.arcount; r; r--) 719 _asr_unpack_rr(&p, &rr); 720 721 /* Report any error found when unpacking the RRs. */ 722 if (p.err) { 723 DPRINT("unpack: %s\n", strerror(p.err)); 724 errno = p.err; 725 return (-1); 726 } 727 728 if (p.offset != as->as.dns.ibuflen) { 729 DPRINT("trailing garbage\n"); 730 errno = EMSGSIZE; 731 return (-1); 732 } 733 734 return (0); 735 736 inval: 737 errno = EINVAL; 738 return (-1); 739 } 740 741 /* 742 * Set the async context nameserver index to the next nameserver, cycling 743 * over the list until the maximum retry counter is reached. Return 0 on 744 * success, or -1 if all nameservers were used. 745 */ 746 static int 747 iter_ns(struct asr_query *as) 748 { 749 for (;;) { 750 if (as->as.dns.nsloop >= as->as_ctx->ac_nsretries) 751 return (-1); 752 753 as->as.dns.nsidx += 1; 754 if (as->as.dns.nsidx <= as->as_ctx->ac_nscount) 755 break; 756 as->as.dns.nsidx = 0; 757 as->as.dns.nsloop++; 758 DPRINT("asr: iter_ns(): cycle %i\n", as->as.dns.nsloop); 759 } 760 761 as->as_timeout = 1000 * (as->as_ctx->ac_nstimeout << as->as.dns.nsloop); 762 if (as->as.dns.nsloop > 0) 763 as->as_timeout /= as->as_ctx->ac_nscount; 764 if (as->as_timeout < 1000) 765 as->as_timeout = 1000; 766 767 return (0); 768 } 769