1 /* $NetBSD: evdns.c,v 1.3 2015/01/29 07:26:02 spz Exp $ */ 2 /* Copyright 2006-2007 Niels Provos 3 * Copyright 2007-2012 Nick Mathewson and Niels Provos 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 3. The name of the author may not be used to endorse or promote products 14 * derived from this software without specific prior written permission. 15 * 16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 17 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 18 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 19 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 21 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 22 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 23 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 24 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 25 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 26 */ 27 28 /* Based on software by Adam Langly. Adam's original message: 29 * 30 * Async DNS Library 31 * Adam Langley <agl@imperialviolet.org> 32 * http://www.imperialviolet.org/eventdns.html 33 * Public Domain code 34 * 35 * This software is Public Domain. To view a copy of the public domain dedication, 36 * visit http://creativecommons.org/licenses/publicdomain/ or send a letter to 37 * Creative Commons, 559 Nathan Abbott Way, Stanford, California 94305, USA. 38 * 39 * I ask and expect, but do not require, that all derivative works contain an 40 * attribution similar to: 41 * Parts developed by Adam Langley <agl@imperialviolet.org> 42 * 43 * You may wish to replace the word "Parts" with something else depending on 44 * the amount of original code. 45 * 46 * (Derivative works does not include programs which link against, run or include 47 * the source verbatim in their source distributions) 48 * 49 * Version: 0.1b 50 */ 51 52 #include <sys/types.h> 53 #include "event2/event-config.h" 54 #include <sys/cdefs.h> 55 __RCSID("$NetBSD: evdns.c,v 1.3 2015/01/29 07:26:02 spz Exp $"); 56 57 #ifndef _FORTIFY_SOURCE 58 #define _FORTIFY_SOURCE 3 59 #endif 60 61 #include <string.h> 62 #include <fcntl.h> 63 #ifdef _EVENT_HAVE_SYS_TIME_H 64 #include <sys/time.h> 65 #endif 66 #ifdef _EVENT_HAVE_STDINT_H 67 #include <stdint.h> 68 #endif 69 #include <stdlib.h> 70 #include <string.h> 71 #include <errno.h> 72 #ifdef _EVENT_HAVE_UNISTD_H 73 #include <unistd.h> 74 #endif 75 #include <limits.h> 76 #include <sys/stat.h> 77 #include <stdio.h> 78 #include <stdarg.h> 79 #ifdef WIN32 80 #include <winsock2.h> 81 #include <ws2tcpip.h> 82 #ifndef _WIN32_IE 83 #define _WIN32_IE 0x400 84 #endif 85 #include <shlobj.h> 86 #endif 87 88 #include "event2/dns.h" 89 #include "event2/dns_struct.h" 90 #include "event2/dns_compat.h" 91 #include "event2/util.h" 92 #include "event2/event.h" 93 #include "event2/event_struct.h" 94 #include "event2/thread.h" 95 96 #include "event2/bufferevent.h" 97 #include "event2/bufferevent_struct.h" 98 #include "bufferevent-internal.h" 99 100 #include "defer-internal.h" 101 #include "log-internal.h" 102 #include "mm-internal.h" 103 #include "strlcpy-internal.h" 104 #include "ipv6-internal.h" 105 #include "util-internal.h" 106 #include "evthread-internal.h" 107 #ifdef WIN32 108 #include <ctype.h> 109 #include <winsock2.h> 110 #include <windows.h> 111 #include <iphlpapi.h> 112 #include <io.h> 113 #else 114 #include <sys/socket.h> 115 #include <netinet/in.h> 116 #include <arpa/inet.h> 117 #endif 118 119 #ifdef _EVENT_HAVE_NETINET_IN6_H 120 #include <netinet/in6.h> 121 #endif 122 123 #define EVDNS_LOG_DEBUG 0 124 #define EVDNS_LOG_WARN 1 125 #define EVDNS_LOG_MSG 2 126 127 #ifndef HOST_NAME_MAX 128 #define HOST_NAME_MAX 255 129 #endif 130 131 #include <stdio.h> 132 133 #undef MIN 134 #define MIN(a,b) ((a)<(b)?(a):(b)) 135 136 #define ASSERT_VALID_REQUEST(req) \ 137 EVUTIL_ASSERT((req)->handle && (req)->handle->current_req == (req)) 138 139 #define u64 ev_uint64_t 140 #define u32 ev_uint32_t 141 #define u16 ev_uint16_t 142 #define u8 ev_uint8_t 143 144 /* maximum number of addresses from a single packet */ 145 /* that we bother recording */ 146 #define MAX_V4_ADDRS 32 147 #define MAX_V6_ADDRS 32 148 149 150 #define TYPE_A EVDNS_TYPE_A 151 #define TYPE_CNAME 5 152 #define TYPE_PTR EVDNS_TYPE_PTR 153 #define TYPE_SOA EVDNS_TYPE_SOA 154 #define TYPE_AAAA EVDNS_TYPE_AAAA 155 156 #define CLASS_INET EVDNS_CLASS_INET 157 158 /* Persistent handle. We keep this separate from 'struct request' since we 159 * need some object to last for as long as an evdns_request is outstanding so 160 * that it can be canceled, whereas a search request can lead to multiple 161 * 'struct request' instances being created over its lifetime. */ 162 struct evdns_request { 163 struct request *current_req; 164 struct evdns_base *base; 165 166 int pending_cb; /* Waiting for its callback to be invoked; not 167 * owned by event base any more. */ 168 169 /* elements used by the searching code */ 170 int search_index; 171 struct search_state *search_state; 172 char *search_origname; /* needs to be free()ed */ 173 int search_flags; 174 }; 175 176 struct request { 177 u8 *request; /* the dns packet data */ 178 u8 request_type; /* TYPE_PTR or TYPE_A or TYPE_AAAA */ 179 unsigned int request_len; 180 int reissue_count; 181 int tx_count; /* the number of times that this packet has been sent */ 182 void *user_pointer; /* the pointer given to us for this request */ 183 evdns_callback_type user_callback; 184 struct nameserver *ns; /* the server which we last sent it */ 185 186 /* these objects are kept in a circular list */ 187 /* XXX We could turn this into a CIRCLEQ. */ 188 struct request *next, *prev; 189 190 struct event timeout_event; 191 192 u16 trans_id; /* the transaction id */ 193 unsigned request_appended :1; /* true if the request pointer is data which follows this struct */ 194 unsigned transmit_me :1; /* needs to be transmitted */ 195 196 /* XXXX This is a horrible hack. */ 197 char **put_cname_in_ptr; /* store the cname here if we get one. */ 198 199 struct evdns_base *base; 200 201 struct evdns_request *handle; 202 }; 203 204 struct reply { 205 unsigned int type; 206 unsigned int have_answer : 1; 207 union { 208 struct { 209 u32 addrcount; 210 u32 addresses[MAX_V4_ADDRS]; 211 } a; 212 struct { 213 u32 addrcount; 214 struct in6_addr addresses[MAX_V6_ADDRS]; 215 } aaaa; 216 struct { 217 char name[HOST_NAME_MAX]; 218 } ptr; 219 } data; 220 }; 221 222 struct nameserver { 223 evutil_socket_t socket; /* a connected UDP socket */ 224 struct sockaddr_storage address; 225 ev_socklen_t addrlen; 226 int failed_times; /* number of times which we have given this server a chance */ 227 int timedout; /* number of times in a row a request has timed out */ 228 struct event event; 229 /* these objects are kept in a circular list */ 230 struct nameserver *next, *prev; 231 struct event timeout_event; /* used to keep the timeout for */ 232 /* when we next probe this server. */ 233 /* Valid if state == 0 */ 234 /* Outstanding probe request for this nameserver, if any */ 235 struct evdns_request *probe_request; 236 char state; /* zero if we think that this server is down */ 237 char choked; /* true if we have an EAGAIN from this server's socket */ 238 char write_waiting; /* true if we are waiting for EV_WRITE events */ 239 struct evdns_base *base; 240 }; 241 242 243 /* Represents a local port where we're listening for DNS requests. Right now, */ 244 /* only UDP is supported. */ 245 struct evdns_server_port { 246 evutil_socket_t socket; /* socket we use to read queries and write replies. */ 247 int refcnt; /* reference count. */ 248 char choked; /* Are we currently blocked from writing? */ 249 char closing; /* Are we trying to close this port, pending writes? */ 250 evdns_request_callback_fn_type user_callback; /* Fn to handle requests */ 251 void *user_data; /* Opaque pointer passed to user_callback */ 252 struct event event; /* Read/write event */ 253 /* circular list of replies that we want to write. */ 254 struct server_request *pending_replies; 255 struct event_base *event_base; 256 257 #ifndef _EVENT_DISABLE_THREAD_SUPPORT 258 void *lock; 259 #endif 260 }; 261 262 /* Represents part of a reply being built. (That is, a single RR.) */ 263 struct server_reply_item { 264 struct server_reply_item *next; /* next item in sequence. */ 265 char *name; /* name part of the RR */ 266 u16 type; /* The RR type */ 267 u16 class; /* The RR class (usually CLASS_INET) */ 268 u32 ttl; /* The RR TTL */ 269 char is_name; /* True iff data is a label */ 270 u16 datalen; /* Length of data; -1 if data is a label */ 271 void *data; /* The contents of the RR */ 272 }; 273 274 /* Represents a request that we've received as a DNS server, and holds */ 275 /* the components of the reply as we're constructing it. */ 276 struct server_request { 277 /* Pointers to the next and previous entries on the list of replies */ 278 /* that we're waiting to write. Only set if we have tried to respond */ 279 /* and gotten EAGAIN. */ 280 struct server_request *next_pending; 281 struct server_request *prev_pending; 282 283 u16 trans_id; /* Transaction id. */ 284 struct evdns_server_port *port; /* Which port received this request on? */ 285 struct sockaddr_storage addr; /* Where to send the response */ 286 ev_socklen_t addrlen; /* length of addr */ 287 288 int n_answer; /* how many answer RRs have been set? */ 289 int n_authority; /* how many authority RRs have been set? */ 290 int n_additional; /* how many additional RRs have been set? */ 291 292 struct server_reply_item *answer; /* linked list of answer RRs */ 293 struct server_reply_item *authority; /* linked list of authority RRs */ 294 struct server_reply_item *additional; /* linked list of additional RRs */ 295 296 /* Constructed response. Only set once we're ready to send a reply. */ 297 /* Once this is set, the RR fields are cleared, and no more should be set. */ 298 char *response; 299 size_t response_len; 300 301 /* Caller-visible fields: flags, questions. */ 302 struct evdns_server_request base; 303 }; 304 305 struct evdns_base { 306 /* An array of n_req_heads circular lists for inflight requests. 307 * Each inflight request req is in req_heads[req->trans_id % n_req_heads]. 308 */ 309 struct request **req_heads; 310 /* A circular list of requests that we're waiting to send, but haven't 311 * sent yet because there are too many requests inflight */ 312 struct request *req_waiting_head; 313 /* A circular list of nameservers. */ 314 struct nameserver *server_head; 315 int n_req_heads; 316 317 struct event_base *event_base; 318 319 /* The number of good nameservers that we have */ 320 int global_good_nameservers; 321 322 /* inflight requests are contained in the req_head list */ 323 /* and are actually going out across the network */ 324 int global_requests_inflight; 325 /* requests which aren't inflight are in the waiting list */ 326 /* and are counted here */ 327 int global_requests_waiting; 328 329 int global_max_requests_inflight; 330 331 struct timeval global_timeout; /* 5 seconds by default */ 332 int global_max_reissues; /* a reissue occurs when we get some errors from the server */ 333 int global_max_retransmits; /* number of times we'll retransmit a request which timed out */ 334 /* number of timeouts in a row before we consider this server to be down */ 335 int global_max_nameserver_timeout; 336 /* true iff we will use the 0x20 hack to prevent poisoning attacks. */ 337 int global_randomize_case; 338 339 /* The first time that a nameserver fails, how long do we wait before 340 * probing to see if it has returned? */ 341 struct timeval global_nameserver_probe_initial_timeout; 342 343 /** Port to bind to for outgoing DNS packets. */ 344 struct sockaddr_storage global_outgoing_address; 345 /** ev_socklen_t for global_outgoing_address. 0 if it isn't set. */ 346 ev_socklen_t global_outgoing_addrlen; 347 348 struct timeval global_getaddrinfo_allow_skew; 349 350 int getaddrinfo_ipv4_timeouts; 351 int getaddrinfo_ipv6_timeouts; 352 int getaddrinfo_ipv4_answered; 353 int getaddrinfo_ipv6_answered; 354 355 struct search_state *global_search_state; 356 357 TAILQ_HEAD(hosts_list, hosts_entry) hostsdb; 358 359 #ifndef _EVENT_DISABLE_THREAD_SUPPORT 360 void *lock; 361 #endif 362 }; 363 364 struct hosts_entry { 365 TAILQ_ENTRY(hosts_entry) next; 366 union { 367 struct sockaddr sa; 368 struct sockaddr_in sin; 369 struct sockaddr_in6 sin6; 370 } addr; 371 int addrlen; 372 char hostname[1]; 373 }; 374 375 static struct evdns_base *current_base = NULL; 376 377 struct evdns_base * 378 evdns_get_global_base(void) 379 { 380 return current_base; 381 } 382 383 /* Given a pointer to an evdns_server_request, get the corresponding */ 384 /* server_request. */ 385 #define TO_SERVER_REQUEST(base_ptr) \ 386 ((struct server_request*) \ 387 (((char*)(base_ptr) - evutil_offsetof(struct server_request, base)))) 388 389 #define REQ_HEAD(base, id) ((base)->req_heads[id % (base)->n_req_heads]) 390 391 static struct nameserver *nameserver_pick(struct evdns_base *base); 392 static void evdns_request_insert(struct request *req, struct request **head); 393 static void evdns_request_remove(struct request *req, struct request **head); 394 static void nameserver_ready_callback(evutil_socket_t fd, short events, void *arg); 395 static int evdns_transmit(struct evdns_base *base); 396 static int evdns_request_transmit(struct request *req); 397 static void nameserver_send_probe(struct nameserver *const ns); 398 static void search_request_finished(struct evdns_request *const); 399 static int search_try_next(struct evdns_request *const req); 400 static struct request *search_request_new(struct evdns_base *base, struct evdns_request *handle, int type, const char *const name, int flags, evdns_callback_type user_callback, void *user_arg); 401 static void evdns_requests_pump_waiting_queue(struct evdns_base *base); 402 static u16 transaction_id_pick(struct evdns_base *base); 403 static struct request *request_new(struct evdns_base *base, struct evdns_request *handle, int type, const char *name, int flags, evdns_callback_type callback, void *ptr); 404 static void request_submit(struct request *const req); 405 406 static int server_request_free(struct server_request *req); 407 static void server_request_free_answers(struct server_request *req); 408 static void server_port_free(struct evdns_server_port *port); 409 static void server_port_ready_callback(evutil_socket_t fd, short events, void *arg); 410 static int evdns_base_resolv_conf_parse_impl(struct evdns_base *base, int flags, const char *const filename); 411 static int evdns_base_set_option_impl(struct evdns_base *base, 412 const char *option, const char *val, int flags); 413 static void evdns_base_free_and_unlock(struct evdns_base *base, int fail_requests); 414 415 static int strtoint(const char *const str); 416 417 #ifdef _EVENT_DISABLE_THREAD_SUPPORT 418 #define EVDNS_LOCK(base) _EVUTIL_NIL_STMT 419 #define EVDNS_UNLOCK(base) _EVUTIL_NIL_STMT 420 #define ASSERT_LOCKED(base) _EVUTIL_NIL_STMT 421 #else 422 #define EVDNS_LOCK(base) \ 423 EVLOCK_LOCK((base)->lock, 0) 424 #define EVDNS_UNLOCK(base) \ 425 EVLOCK_UNLOCK((base)->lock, 0) 426 #define ASSERT_LOCKED(base) \ 427 EVLOCK_ASSERT_LOCKED((base)->lock) 428 #endif 429 430 static void 431 default_evdns_log_fn(int warning, const char *buf) 432 { 433 if (warning == EVDNS_LOG_WARN) 434 event_warnx("[evdns] %s", buf); 435 else if (warning == EVDNS_LOG_MSG) 436 event_msgx("[evdns] %s", buf); 437 else 438 event_debug(("[evdns] %s", buf)); 439 } 440 441 static evdns_debug_log_fn_type evdns_log_fn = NULL; 442 443 void 444 evdns_set_log_fn(evdns_debug_log_fn_type fn) 445 { 446 evdns_log_fn = fn; 447 } 448 449 #ifdef __GNUC__ 450 #define EVDNS_LOG_CHECK __attribute__ ((format(printf, 2, 3))) 451 #else 452 #define EVDNS_LOG_CHECK 453 #endif 454 455 static void _evdns_log(int warn, const char *fmt, ...) EVDNS_LOG_CHECK; 456 static void 457 _evdns_log(int warn, const char *fmt, ...) 458 { 459 va_list args; 460 char buf[512]; 461 if (!evdns_log_fn) 462 return; 463 va_start(args,fmt); 464 evutil_vsnprintf(buf, sizeof(buf), fmt, args); 465 va_end(args); 466 if (evdns_log_fn) { 467 if (warn == EVDNS_LOG_MSG) 468 warn = EVDNS_LOG_WARN; 469 evdns_log_fn(warn, buf); 470 } else { 471 default_evdns_log_fn(warn, buf); 472 } 473 474 } 475 476 #define log _evdns_log 477 478 /* This walks the list of inflight requests to find the */ 479 /* one with a matching transaction id. Returns NULL on */ 480 /* failure */ 481 static struct request * 482 request_find_from_trans_id(struct evdns_base *base, u16 trans_id) { 483 struct request *req = REQ_HEAD(base, trans_id); 484 struct request *const started_at = req; 485 486 ASSERT_LOCKED(base); 487 488 if (req) { 489 do { 490 if (req->trans_id == trans_id) return req; 491 req = req->next; 492 } while (req != started_at); 493 } 494 495 return NULL; 496 } 497 498 /* a libevent callback function which is called when a nameserver */ 499 /* has gone down and we want to test if it has came back to life yet */ 500 static void 501 nameserver_prod_callback(evutil_socket_t fd, short events, void *arg) { 502 struct nameserver *const ns = (struct nameserver *) arg; 503 (void)fd; 504 (void)events; 505 506 EVDNS_LOCK(ns->base); 507 nameserver_send_probe(ns); 508 EVDNS_UNLOCK(ns->base); 509 } 510 511 /* a libevent callback which is called when a nameserver probe (to see if */ 512 /* it has come back to life) times out. We increment the count of failed_times */ 513 /* and wait longer to send the next probe packet. */ 514 static void 515 nameserver_probe_failed(struct nameserver *const ns) { 516 struct timeval timeout; 517 int i; 518 519 ASSERT_LOCKED(ns->base); 520 (void) evtimer_del(&ns->timeout_event); 521 if (ns->state == 1) { 522 /* This can happen if the nameserver acts in a way which makes us mark */ 523 /* it as bad and then starts sending good replies. */ 524 return; 525 } 526 527 #define MAX_PROBE_TIMEOUT 3600 528 #define TIMEOUT_BACKOFF_FACTOR 3 529 530 memcpy(&timeout, &ns->base->global_nameserver_probe_initial_timeout, 531 sizeof(struct timeval)); 532 for (i=ns->failed_times; i > 0 && timeout.tv_sec < MAX_PROBE_TIMEOUT; --i) { 533 timeout.tv_sec *= TIMEOUT_BACKOFF_FACTOR; 534 timeout.tv_usec *= TIMEOUT_BACKOFF_FACTOR; 535 if (timeout.tv_usec > 1000000) { 536 timeout.tv_sec += timeout.tv_usec / 1000000; 537 timeout.tv_usec %= 1000000; 538 } 539 } 540 if (timeout.tv_sec > MAX_PROBE_TIMEOUT) { 541 timeout.tv_sec = MAX_PROBE_TIMEOUT; 542 timeout.tv_usec = 0; 543 } 544 545 ns->failed_times++; 546 547 if (evtimer_add(&ns->timeout_event, &timeout) < 0) { 548 char addrbuf[128]; 549 log(EVDNS_LOG_WARN, 550 "Error from libevent when adding timer event for %s", 551 evutil_format_sockaddr_port( 552 (struct sockaddr *)&ns->address, 553 addrbuf, sizeof(addrbuf))); 554 } 555 } 556 557 /* called when a nameserver has been deemed to have failed. For example, too */ 558 /* many packets have timed out etc */ 559 static void 560 nameserver_failed(struct nameserver *const ns, const char *msg) { 561 struct request *req, *started_at; 562 struct evdns_base *base = ns->base; 563 int i; 564 char addrbuf[128]; 565 566 ASSERT_LOCKED(base); 567 /* if this nameserver has already been marked as failed */ 568 /* then don't do anything */ 569 if (!ns->state) return; 570 571 log(EVDNS_LOG_MSG, "Nameserver %s has failed: %s", 572 evutil_format_sockaddr_port( 573 (struct sockaddr *)&ns->address, 574 addrbuf, sizeof(addrbuf)), 575 msg); 576 577 base->global_good_nameservers--; 578 EVUTIL_ASSERT(base->global_good_nameservers >= 0); 579 if (base->global_good_nameservers == 0) { 580 log(EVDNS_LOG_MSG, "All nameservers have failed"); 581 } 582 583 ns->state = 0; 584 ns->failed_times = 1; 585 586 if (evtimer_add(&ns->timeout_event, 587 &base->global_nameserver_probe_initial_timeout) < 0) { 588 log(EVDNS_LOG_WARN, 589 "Error from libevent when adding timer event for %s", 590 evutil_format_sockaddr_port( 591 (struct sockaddr *)&ns->address, 592 addrbuf, sizeof(addrbuf))); 593 /* ???? Do more? */ 594 } 595 596 /* walk the list of inflight requests to see if any can be reassigned to */ 597 /* a different server. Requests in the waiting queue don't have a */ 598 /* nameserver assigned yet */ 599 600 /* if we don't have *any* good nameservers then there's no point */ 601 /* trying to reassign requests to one */ 602 if (!base->global_good_nameservers) return; 603 604 for (i = 0; i < base->n_req_heads; ++i) { 605 req = started_at = base->req_heads[i]; 606 if (req) { 607 do { 608 if (req->tx_count == 0 && req->ns == ns) { 609 /* still waiting to go out, can be moved */ 610 /* to another server */ 611 req->ns = nameserver_pick(base); 612 } 613 req = req->next; 614 } while (req != started_at); 615 } 616 } 617 } 618 619 static void 620 nameserver_up(struct nameserver *const ns) 621 { 622 char addrbuf[128]; 623 ASSERT_LOCKED(ns->base); 624 if (ns->state) return; 625 log(EVDNS_LOG_MSG, "Nameserver %s is back up", 626 evutil_format_sockaddr_port( 627 (struct sockaddr *)&ns->address, 628 addrbuf, sizeof(addrbuf))); 629 evtimer_del(&ns->timeout_event); 630 if (ns->probe_request) { 631 evdns_cancel_request(ns->base, ns->probe_request); 632 ns->probe_request = NULL; 633 } 634 ns->state = 1; 635 ns->failed_times = 0; 636 ns->timedout = 0; 637 ns->base->global_good_nameservers++; 638 } 639 640 static void 641 request_trans_id_set(struct request *const req, const u16 trans_id) { 642 req->trans_id = trans_id; 643 *((u16 *) req->request) = htons(trans_id); 644 } 645 646 /* Called to remove a request from a list and dealloc it. */ 647 /* head is a pointer to the head of the list it should be */ 648 /* removed from or NULL if the request isn't in a list. */ 649 /* when free_handle is one, free the handle as well. */ 650 static void 651 request_finished(struct request *const req, struct request **head, int free_handle) { 652 struct evdns_base *base = req->base; 653 int was_inflight = (head != &base->req_waiting_head); 654 EVDNS_LOCK(base); 655 ASSERT_VALID_REQUEST(req); 656 657 if (head) 658 evdns_request_remove(req, head); 659 660 log(EVDNS_LOG_DEBUG, "Removing timeout for request %p", req); 661 if (was_inflight) { 662 evtimer_del(&req->timeout_event); 663 base->global_requests_inflight--; 664 } else { 665 base->global_requests_waiting--; 666 } 667 /* it was initialized during request_new / evtimer_assign */ 668 event_debug_unassign(&req->timeout_event); 669 670 if (!req->request_appended) { 671 /* need to free the request data on it's own */ 672 mm_free(req->request); 673 } else { 674 /* the request data is appended onto the header */ 675 /* so everything gets free()ed when we: */ 676 } 677 678 if (req->handle) { 679 EVUTIL_ASSERT(req->handle->current_req == req); 680 681 if (free_handle) { 682 search_request_finished(req->handle); 683 req->handle->current_req = NULL; 684 if (! req->handle->pending_cb) { 685 /* If we're planning to run the callback, 686 * don't free the handle until later. */ 687 mm_free(req->handle); 688 } 689 req->handle = NULL; /* If we have a bug, let's crash 690 * early */ 691 } else { 692 req->handle->current_req = NULL; 693 } 694 } 695 696 mm_free(req); 697 698 evdns_requests_pump_waiting_queue(base); 699 EVDNS_UNLOCK(base); 700 } 701 702 /* This is called when a server returns a funny error code. */ 703 /* We try the request again with another server. */ 704 /* */ 705 /* return: */ 706 /* 0 ok */ 707 /* 1 failed/reissue is pointless */ 708 static int 709 request_reissue(struct request *req) { 710 const struct nameserver *const last_ns = req->ns; 711 ASSERT_LOCKED(req->base); 712 ASSERT_VALID_REQUEST(req); 713 /* the last nameserver should have been marked as failing */ 714 /* by the caller of this function, therefore pick will try */ 715 /* not to return it */ 716 req->ns = nameserver_pick(req->base); 717 if (req->ns == last_ns) { 718 /* ... but pick did return it */ 719 /* not a lot of point in trying again with the */ 720 /* same server */ 721 return 1; 722 } 723 724 req->reissue_count++; 725 req->tx_count = 0; 726 req->transmit_me = 1; 727 728 return 0; 729 } 730 731 /* this function looks for space on the inflight queue and promotes */ 732 /* requests from the waiting queue if it can. */ 733 /* */ 734 /* TODO: */ 735 /* add return code, see at nameserver_pick() and other functions. */ 736 static void 737 evdns_requests_pump_waiting_queue(struct evdns_base *base) { 738 ASSERT_LOCKED(base); 739 while (base->global_requests_inflight < base->global_max_requests_inflight && 740 base->global_requests_waiting) { 741 struct request *req; 742 743 EVUTIL_ASSERT(base->req_waiting_head); 744 req = base->req_waiting_head; 745 746 req->ns = nameserver_pick(base); 747 if (!req->ns) 748 return; 749 750 /* move a request from the waiting queue to the inflight queue */ 751 evdns_request_remove(req, &base->req_waiting_head); 752 753 base->global_requests_waiting--; 754 base->global_requests_inflight++; 755 756 request_trans_id_set(req, transaction_id_pick(base)); 757 758 evdns_request_insert(req, &REQ_HEAD(base, req->trans_id)); 759 evdns_request_transmit(req); 760 evdns_transmit(base); 761 } 762 } 763 764 /* TODO(nickm) document */ 765 struct deferred_reply_callback { 766 struct deferred_cb deferred; 767 struct evdns_request *handle; 768 u8 request_type; 769 u8 have_reply; 770 u32 ttl; 771 u32 err; 772 evdns_callback_type user_callback; 773 struct reply reply; 774 }; 775 776 static void 777 reply_run_callback(struct deferred_cb *d, void *user_pointer) 778 { 779 struct deferred_reply_callback *cb = 780 EVUTIL_UPCAST(d, struct deferred_reply_callback, deferred); 781 782 switch (cb->request_type) { 783 case TYPE_A: 784 if (cb->have_reply) 785 cb->user_callback(DNS_ERR_NONE, DNS_IPv4_A, 786 cb->reply.data.a.addrcount, cb->ttl, 787 cb->reply.data.a.addresses, 788 user_pointer); 789 else 790 cb->user_callback(cb->err, 0, 0, cb->ttl, NULL, user_pointer); 791 break; 792 case TYPE_PTR: 793 if (cb->have_reply) { 794 char *name = cb->reply.data.ptr.name; 795 cb->user_callback(DNS_ERR_NONE, DNS_PTR, 1, cb->ttl, 796 &name, user_pointer); 797 } else { 798 cb->user_callback(cb->err, 0, 0, cb->ttl, NULL, user_pointer); 799 } 800 break; 801 case TYPE_AAAA: 802 if (cb->have_reply) 803 cb->user_callback(DNS_ERR_NONE, DNS_IPv6_AAAA, 804 cb->reply.data.aaaa.addrcount, cb->ttl, 805 cb->reply.data.aaaa.addresses, 806 user_pointer); 807 else 808 cb->user_callback(cb->err, 0, 0, cb->ttl, NULL, user_pointer); 809 break; 810 default: 811 EVUTIL_ASSERT(0); 812 } 813 814 if (cb->handle && cb->handle->pending_cb) { 815 mm_free(cb->handle); 816 } 817 818 mm_free(cb); 819 } 820 821 static void 822 reply_schedule_callback(struct request *const req, u32 ttl, u32 err, struct reply *reply) 823 { 824 struct deferred_reply_callback *d = mm_calloc(1, sizeof(*d)); 825 826 if (!d) { 827 event_warn("%s: Couldn't allocate space for deferred callback.", 828 __func__); 829 return; 830 } 831 832 ASSERT_LOCKED(req->base); 833 834 d->request_type = req->request_type; 835 d->user_callback = req->user_callback; 836 d->ttl = ttl; 837 d->err = err; 838 if (reply) { 839 d->have_reply = 1; 840 memcpy(&d->reply, reply, sizeof(struct reply)); 841 } 842 843 if (req->handle) { 844 req->handle->pending_cb = 1; 845 d->handle = req->handle; 846 } 847 848 event_deferred_cb_init(&d->deferred, reply_run_callback, 849 req->user_pointer); 850 event_deferred_cb_schedule( 851 event_base_get_deferred_cb_queue(req->base->event_base), 852 &d->deferred); 853 } 854 855 /* this processes a parsed reply packet */ 856 static void 857 reply_handle(struct request *const req, u16 flags, u32 ttl, struct reply *reply) { 858 int error; 859 char addrbuf[128]; 860 static const int error_codes[] = { 861 DNS_ERR_FORMAT, DNS_ERR_SERVERFAILED, DNS_ERR_NOTEXIST, 862 DNS_ERR_NOTIMPL, DNS_ERR_REFUSED 863 }; 864 865 ASSERT_LOCKED(req->base); 866 ASSERT_VALID_REQUEST(req); 867 868 if (flags & 0x020f || !reply || !reply->have_answer) { 869 /* there was an error */ 870 if (flags & 0x0200) { 871 error = DNS_ERR_TRUNCATED; 872 } else if (flags & 0x000f) { 873 u16 error_code = (flags & 0x000f) - 1; 874 if (error_code > 4) { 875 error = DNS_ERR_UNKNOWN; 876 } else { 877 error = error_codes[error_code]; 878 } 879 } else if (reply && !reply->have_answer) { 880 error = DNS_ERR_NODATA; 881 } else { 882 error = DNS_ERR_UNKNOWN; 883 } 884 885 switch (error) { 886 case DNS_ERR_NOTIMPL: 887 case DNS_ERR_REFUSED: 888 /* we regard these errors as marking a bad nameserver */ 889 if (req->reissue_count < req->base->global_max_reissues) { 890 char msg[64]; 891 evutil_snprintf(msg, sizeof(msg), "Bad response %d (%s)", 892 error, evdns_err_to_string(error)); 893 nameserver_failed(req->ns, msg); 894 if (!request_reissue(req)) return; 895 } 896 break; 897 case DNS_ERR_SERVERFAILED: 898 /* rcode 2 (servfailed) sometimes means "we 899 * are broken" and sometimes (with some binds) 900 * means "that request was very confusing." 901 * Treat this as a timeout, not a failure. 902 */ 903 log(EVDNS_LOG_DEBUG, "Got a SERVERFAILED from nameserver" 904 "at %s; will allow the request to time out.", 905 evutil_format_sockaddr_port( 906 (struct sockaddr *)&req->ns->address, 907 addrbuf, sizeof(addrbuf))); 908 break; 909 default: 910 /* we got a good reply from the nameserver: it is up. */ 911 if (req->handle == req->ns->probe_request) { 912 /* Avoid double-free */ 913 req->ns->probe_request = NULL; 914 } 915 916 nameserver_up(req->ns); 917 } 918 919 if (req->handle->search_state && 920 req->request_type != TYPE_PTR) { 921 /* if we have a list of domains to search in, 922 * try the next one */ 923 if (!search_try_next(req->handle)) { 924 /* a new request was issued so this 925 * request is finished and */ 926 /* the user callback will be made when 927 * that request (or a */ 928 /* child of it) finishes. */ 929 return; 930 } 931 } 932 933 /* all else failed. Pass the failure up */ 934 reply_schedule_callback(req, ttl, error, NULL); 935 request_finished(req, &REQ_HEAD(req->base, req->trans_id), 1); 936 } else { 937 /* all ok, tell the user */ 938 reply_schedule_callback(req, ttl, 0, reply); 939 if (req->handle == req->ns->probe_request) 940 req->ns->probe_request = NULL; /* Avoid double-free */ 941 nameserver_up(req->ns); 942 request_finished(req, &REQ_HEAD(req->base, req->trans_id), 1); 943 } 944 } 945 946 static int 947 name_parse(u8 *packet, int length, int *idx, char *name_out, int name_out_len) { 948 int name_end = -1; 949 int j = *idx; 950 int ptr_count = 0; 951 #define GET32(x) do { if (j + 4 > length) goto err; memcpy(&_t32, packet + j, 4); j += 4; x = ntohl(_t32); } while (/*CONSTCOND*/0) 952 #define GET16(x) do { if (j + 2 > length) goto err; memcpy(&_t, packet + j, 2); j += 2; x = ntohs(_t); } while (/*CONSTCOND*/0) 953 #define GET8(x) do { if (j >= length) goto err; x = packet[j++]; } while (/*CONSTCOND*/0) 954 955 char *cp = name_out; 956 const char *const end = name_out + name_out_len; 957 958 /* Normally, names are a series of length prefixed strings terminated */ 959 /* with a length of 0 (the lengths are u8's < 63). */ 960 /* However, the length can start with a pair of 1 bits and that */ 961 /* means that the next 14 bits are a pointer within the current */ 962 /* packet. */ 963 964 for (;;) { 965 u8 label_len; 966 if (j >= length) return -1; 967 GET8(label_len); 968 if (!label_len) break; 969 if (label_len & 0xc0) { 970 u8 ptr_low; 971 GET8(ptr_low); 972 if (name_end < 0) name_end = j; 973 j = (((int)label_len & 0x3f) << 8) + ptr_low; 974 /* Make sure that the target offset is in-bounds. */ 975 if (j < 0 || j >= length) return -1; 976 /* If we've jumped more times than there are characters in the 977 * message, we must have a loop. */ 978 if (++ptr_count > length) return -1; 979 continue; 980 } 981 if (label_len > 63) return -1; 982 if (cp != name_out) { 983 if (cp + 1 >= end) return -1; 984 *cp++ = '.'; 985 } 986 if (cp + label_len >= end) return -1; 987 memcpy(cp, packet + j, label_len); 988 cp += label_len; 989 j += label_len; 990 } 991 if (cp >= end) return -1; 992 *cp = '\0'; 993 if (name_end < 0) 994 *idx = j; 995 else 996 *idx = name_end; 997 return 0; 998 err: 999 return -1; 1000 } 1001 1002 /* parses a raw request from a nameserver */ 1003 static int 1004 reply_parse(struct evdns_base *base, u8 *packet, int length) { 1005 int j = 0, k = 0; /* index into packet */ 1006 u16 _t; /* used by the macros */ 1007 u32 _t32; /* used by the macros */ 1008 char tmp_name[256], cmp_name[256]; /* used by the macros */ 1009 int name_matches = 0; 1010 1011 u16 trans_id, questions, answers, authority, additional, datalength; 1012 u16 flags = 0; 1013 u32 ttl, ttl_r = 0xffffffff; 1014 struct reply reply; 1015 struct request *req = NULL; 1016 unsigned int i; 1017 1018 ASSERT_LOCKED(base); 1019 1020 GET16(trans_id); 1021 GET16(flags); 1022 GET16(questions); 1023 GET16(answers); 1024 GET16(authority); 1025 GET16(additional); 1026 (void) authority; /* suppress "unused variable" warnings. */ 1027 (void) additional; /* suppress "unused variable" warnings. */ 1028 1029 req = request_find_from_trans_id(base, trans_id); 1030 if (!req) return -1; 1031 EVUTIL_ASSERT(req->base == base); 1032 1033 memset(&reply, 0, sizeof(reply)); 1034 1035 /* If it's not an answer, it doesn't correspond to any request. */ 1036 if (!(flags & 0x8000)) return -1; /* must be an answer */ 1037 if ((flags & 0x020f) && (flags & 0x020f) != DNS_ERR_NOTEXIST) { 1038 /* there was an error and it's not NXDOMAIN */ 1039 goto err; 1040 } 1041 /* if (!answers) return; */ /* must have an answer of some form */ 1042 1043 /* This macro skips a name in the DNS reply. */ 1044 #define SKIP_NAME \ 1045 do { tmp_name[0] = '\0'; \ 1046 if (name_parse(packet, length, &j, tmp_name, \ 1047 sizeof(tmp_name))<0) \ 1048 goto err; \ 1049 } while (/*CONSTCOND*/0) 1050 #define TEST_NAME \ 1051 do { tmp_name[0] = '\0'; \ 1052 cmp_name[0] = '\0'; \ 1053 k = j; \ 1054 if (name_parse(packet, length, &j, tmp_name, \ 1055 sizeof(tmp_name))<0) \ 1056 goto err; \ 1057 if (name_parse(req->request, req->request_len, &k, \ 1058 cmp_name, sizeof(cmp_name))<0) \ 1059 goto err; \ 1060 if (base->global_randomize_case) { \ 1061 if (strcmp(tmp_name, cmp_name) == 0) \ 1062 name_matches = 1; \ 1063 } else { \ 1064 if (evutil_ascii_strcasecmp(tmp_name, cmp_name) == 0) \ 1065 name_matches = 1; \ 1066 } \ 1067 } while (/*CONSTCOND*/0) 1068 1069 reply.type = req->request_type; 1070 1071 /* skip over each question in the reply */ 1072 for (i = 0; i < questions; ++i) { 1073 /* the question looks like 1074 * <label:name><u16:type><u16:class> 1075 */ 1076 TEST_NAME; 1077 j += 4; 1078 if (j > length) goto err; 1079 } 1080 1081 if (!name_matches) 1082 goto err; 1083 1084 /* now we have the answer section which looks like 1085 * <label:name><u16:type><u16:class><u32:ttl><u16:len><data...> 1086 */ 1087 1088 for (i = 0; i < answers; ++i) { 1089 u16 type, class; 1090 1091 SKIP_NAME; 1092 GET16(type); 1093 GET16(class); 1094 GET32(ttl); 1095 GET16(datalength); 1096 1097 if (type == TYPE_A && class == CLASS_INET) { 1098 int addrcount, addrtocopy; 1099 if (req->request_type != TYPE_A) { 1100 j += datalength; continue; 1101 } 1102 if ((datalength & 3) != 0) /* not an even number of As. */ 1103 goto err; 1104 addrcount = datalength >> 2; 1105 addrtocopy = MIN(MAX_V4_ADDRS - reply.data.a.addrcount, (unsigned)addrcount); 1106 1107 ttl_r = MIN(ttl_r, ttl); 1108 /* we only bother with the first four addresses. */ 1109 if (j + 4*addrtocopy > length) goto err; 1110 memcpy(&reply.data.a.addresses[reply.data.a.addrcount], 1111 packet + j, 4*addrtocopy); 1112 j += 4*addrtocopy; 1113 reply.data.a.addrcount += addrtocopy; 1114 reply.have_answer = 1; 1115 if (reply.data.a.addrcount == MAX_V4_ADDRS) break; 1116 } else if (type == TYPE_PTR && class == CLASS_INET) { 1117 if (req->request_type != TYPE_PTR) { 1118 j += datalength; continue; 1119 } 1120 if (name_parse(packet, length, &j, reply.data.ptr.name, 1121 sizeof(reply.data.ptr.name))<0) 1122 goto err; 1123 ttl_r = MIN(ttl_r, ttl); 1124 reply.have_answer = 1; 1125 break; 1126 } else if (type == TYPE_CNAME) { 1127 char cname[HOST_NAME_MAX]; 1128 if (!req->put_cname_in_ptr || *req->put_cname_in_ptr) { 1129 j += datalength; continue; 1130 } 1131 if (name_parse(packet, length, &j, cname, 1132 sizeof(cname))<0) 1133 goto err; 1134 *req->put_cname_in_ptr = mm_strdup(cname); 1135 } else if (type == TYPE_AAAA && class == CLASS_INET) { 1136 int addrcount, addrtocopy; 1137 if (req->request_type != TYPE_AAAA) { 1138 j += datalength; continue; 1139 } 1140 if ((datalength & 15) != 0) /* not an even number of AAAAs. */ 1141 goto err; 1142 addrcount = datalength >> 4; /* each address is 16 bytes long */ 1143 addrtocopy = MIN(MAX_V6_ADDRS - reply.data.aaaa.addrcount, (unsigned)addrcount); 1144 ttl_r = MIN(ttl_r, ttl); 1145 1146 /* we only bother with the first four addresses. */ 1147 if (j + 16*addrtocopy > length) goto err; 1148 memcpy(&reply.data.aaaa.addresses[reply.data.aaaa.addrcount], 1149 packet + j, 16*addrtocopy); 1150 reply.data.aaaa.addrcount += addrtocopy; 1151 j += 16*addrtocopy; 1152 reply.have_answer = 1; 1153 if (reply.data.aaaa.addrcount == MAX_V6_ADDRS) break; 1154 } else { 1155 /* skip over any other type of resource */ 1156 j += datalength; 1157 } 1158 } 1159 1160 if (!reply.have_answer) { 1161 for (i = 0; i < authority; ++i) { 1162 u16 type, class; 1163 SKIP_NAME; 1164 GET16(type); 1165 GET16(class); 1166 GET32(ttl); 1167 GET16(datalength); 1168 if (type == TYPE_SOA && class == CLASS_INET) { 1169 u32 serial, refresh, retry, expire, minimum; 1170 SKIP_NAME; 1171 SKIP_NAME; 1172 GET32(serial); 1173 GET32(refresh); 1174 GET32(retry); 1175 GET32(expire); 1176 GET32(minimum); 1177 (void)expire; 1178 (void)retry; 1179 (void)refresh; 1180 (void)serial; 1181 ttl_r = MIN(ttl_r, ttl); 1182 ttl_r = MIN(ttl_r, minimum); 1183 } else { 1184 /* skip over any other type of resource */ 1185 j += datalength; 1186 } 1187 } 1188 } 1189 1190 if (ttl_r == 0xffffffff) 1191 ttl_r = 0; 1192 1193 reply_handle(req, flags, ttl_r, &reply); 1194 return 0; 1195 err: 1196 if (req) 1197 reply_handle(req, flags, 0, NULL); 1198 return -1; 1199 } 1200 1201 /* Parse a raw request (packet,length) sent to a nameserver port (port) from */ 1202 /* a DNS client (addr,addrlen), and if it's well-formed, call the corresponding */ 1203 /* callback. */ 1204 static int 1205 request_parse(u8 *packet, int length, struct evdns_server_port *port, struct sockaddr *addr, ev_socklen_t addrlen) 1206 { 1207 int j = 0; /* index into packet */ 1208 u16 _t; /* used by the macros */ 1209 char tmp_name[256]; /* used by the macros */ 1210 1211 int i; 1212 u16 trans_id, flags, questions, answers, authority, additional; 1213 struct server_request *server_req = NULL; 1214 1215 ASSERT_LOCKED(port); 1216 1217 /* Get the header fields */ 1218 GET16(trans_id); 1219 GET16(flags); 1220 GET16(questions); 1221 GET16(answers); 1222 GET16(authority); 1223 GET16(additional); 1224 (void)answers; 1225 (void)additional; 1226 (void)authority; 1227 1228 if (flags & 0x8000) return -1; /* Must not be an answer. */ 1229 flags &= 0x0110; /* Only RD and CD get preserved. */ 1230 1231 server_req = mm_malloc(sizeof(struct server_request)); 1232 if (server_req == NULL) return -1; 1233 memset(server_req, 0, sizeof(struct server_request)); 1234 1235 server_req->trans_id = trans_id; 1236 memcpy(&server_req->addr, addr, addrlen); 1237 server_req->addrlen = addrlen; 1238 1239 server_req->base.flags = flags; 1240 server_req->base.nquestions = 0; 1241 server_req->base.questions = mm_calloc(sizeof(struct evdns_server_question *), questions); 1242 if (server_req->base.questions == NULL) 1243 goto err; 1244 1245 for (i = 0; i < questions; ++i) { 1246 u16 type, class; 1247 struct evdns_server_question *q; 1248 int namelen; 1249 if (name_parse(packet, length, &j, tmp_name, sizeof(tmp_name))<0) 1250 goto err; 1251 GET16(type); 1252 GET16(class); 1253 namelen = (int)strlen(tmp_name); 1254 q = mm_malloc(sizeof(struct evdns_server_question) + namelen); 1255 if (!q) 1256 goto err; 1257 q->type = type; 1258 q->dns_question_class = class; 1259 memcpy(q->name, tmp_name, namelen+1); 1260 server_req->base.questions[server_req->base.nquestions++] = q; 1261 } 1262 1263 /* Ignore answers, authority, and additional. */ 1264 1265 server_req->port = port; 1266 port->refcnt++; 1267 1268 /* Only standard queries are supported. */ 1269 if (flags & 0x7800) { 1270 evdns_server_request_respond(&(server_req->base), DNS_ERR_NOTIMPL); 1271 return -1; 1272 } 1273 1274 port->user_callback(&(server_req->base), port->user_data); 1275 1276 return 0; 1277 err: 1278 if (server_req) { 1279 if (server_req->base.questions) { 1280 for (i = 0; i < server_req->base.nquestions; ++i) 1281 mm_free(server_req->base.questions[i]); 1282 mm_free(server_req->base.questions); 1283 } 1284 mm_free(server_req); 1285 } 1286 return -1; 1287 1288 #undef SKIP_NAME 1289 #undef GET32 1290 #undef GET16 1291 #undef GET8 1292 } 1293 1294 1295 void 1296 evdns_set_transaction_id_fn(ev_uint16_t (*fn)(void)) 1297 { 1298 } 1299 1300 void 1301 evdns_set_random_bytes_fn(void (*fn)(char *, size_t)) 1302 { 1303 } 1304 1305 /* Try to choose a strong transaction id which isn't already in flight */ 1306 static u16 1307 transaction_id_pick(struct evdns_base *base) { 1308 ASSERT_LOCKED(base); 1309 for (;;) { 1310 u16 trans_id; 1311 evutil_secure_rng_get_bytes(&trans_id, sizeof(trans_id)); 1312 1313 if (trans_id == 0xffff) continue; 1314 /* now check to see if that id is already inflight */ 1315 if (request_find_from_trans_id(base, trans_id) == NULL) 1316 return trans_id; 1317 } 1318 } 1319 1320 /* choose a namesever to use. This function will try to ignore */ 1321 /* nameservers which we think are down and load balance across the rest */ 1322 /* by updating the server_head global each time. */ 1323 static struct nameserver * 1324 nameserver_pick(struct evdns_base *base) { 1325 struct nameserver *started_at = base->server_head, *picked; 1326 ASSERT_LOCKED(base); 1327 if (!base->server_head) return NULL; 1328 1329 /* if we don't have any good nameservers then there's no */ 1330 /* point in trying to find one. */ 1331 if (!base->global_good_nameservers) { 1332 base->server_head = base->server_head->next; 1333 return base->server_head; 1334 } 1335 1336 /* remember that nameservers are in a circular list */ 1337 for (;;) { 1338 if (base->server_head->state) { 1339 /* we think this server is currently good */ 1340 picked = base->server_head; 1341 base->server_head = base->server_head->next; 1342 return picked; 1343 } 1344 1345 base->server_head = base->server_head->next; 1346 if (base->server_head == started_at) { 1347 /* all the nameservers seem to be down */ 1348 /* so we just return this one and hope for the */ 1349 /* best */ 1350 EVUTIL_ASSERT(base->global_good_nameservers == 0); 1351 picked = base->server_head; 1352 base->server_head = base->server_head->next; 1353 return picked; 1354 } 1355 } 1356 } 1357 1358 /* this is called when a namesever socket is ready for reading */ 1359 static void 1360 nameserver_read(struct nameserver *ns) { 1361 struct sockaddr_storage ss; 1362 ev_socklen_t addrlen = sizeof(ss); 1363 u8 packet[1500]; 1364 char addrbuf[128]; 1365 ASSERT_LOCKED(ns->base); 1366 1367 for (;;) { 1368 const int r = recvfrom(ns->socket, (void*)packet, 1369 sizeof(packet), 0, 1370 (struct sockaddr*)&ss, &addrlen); 1371 if (r < 0) { 1372 int err = evutil_socket_geterror(ns->socket); 1373 if (EVUTIL_ERR_RW_RETRIABLE(err)) 1374 return; 1375 nameserver_failed(ns, 1376 evutil_socket_error_to_string(err)); 1377 return; 1378 } 1379 if (evutil_sockaddr_cmp((struct sockaddr*)&ss, 1380 (struct sockaddr*)&ns->address, 0)) { 1381 log(EVDNS_LOG_WARN, "Address mismatch on received " 1382 "DNS packet. Apparent source was %s", 1383 evutil_format_sockaddr_port( 1384 (struct sockaddr *)&ss, 1385 addrbuf, sizeof(addrbuf))); 1386 return; 1387 } 1388 1389 ns->timedout = 0; 1390 reply_parse(ns->base, packet, r); 1391 } 1392 } 1393 1394 /* Read a packet from a DNS client on a server port s, parse it, and */ 1395 /* act accordingly. */ 1396 static void 1397 server_port_read(struct evdns_server_port *s) { 1398 u8 packet[1500]; 1399 struct sockaddr_storage addr; 1400 ev_socklen_t addrlen; 1401 int r; 1402 ASSERT_LOCKED(s); 1403 1404 for (;;) { 1405 addrlen = sizeof(struct sockaddr_storage); 1406 r = recvfrom(s->socket, (void*)packet, sizeof(packet), 0, 1407 (struct sockaddr*) &addr, &addrlen); 1408 if (r < 0) { 1409 int err = evutil_socket_geterror(s->socket); 1410 if (EVUTIL_ERR_RW_RETRIABLE(err)) 1411 return; 1412 log(EVDNS_LOG_WARN, 1413 "Error %s (%d) while reading request.", 1414 evutil_socket_error_to_string(err), err); 1415 return; 1416 } 1417 request_parse(packet, r, s, (struct sockaddr*) &addr, addrlen); 1418 } 1419 } 1420 1421 /* Try to write all pending replies on a given DNS server port. */ 1422 static void 1423 server_port_flush(struct evdns_server_port *port) 1424 { 1425 struct server_request *req = port->pending_replies; 1426 ASSERT_LOCKED(port); 1427 while (req) { 1428 int r = sendto(port->socket, req->response, (int)req->response_len, 0, 1429 (struct sockaddr*) &req->addr, (ev_socklen_t)req->addrlen); 1430 if (r < 0) { 1431 int err = evutil_socket_geterror(port->socket); 1432 if (EVUTIL_ERR_RW_RETRIABLE(err)) 1433 return; 1434 log(EVDNS_LOG_WARN, "Error %s (%d) while writing response to port; dropping", evutil_socket_error_to_string(err), err); 1435 } 1436 if (server_request_free(req)) { 1437 /* we released the last reference to req->port. */ 1438 return; 1439 } else { 1440 EVUTIL_ASSERT(req != port->pending_replies); 1441 req = port->pending_replies; 1442 } 1443 } 1444 1445 /* We have no more pending requests; stop listening for 'writeable' events. */ 1446 (void) event_del(&port->event); 1447 event_assign(&port->event, port->event_base, 1448 port->socket, EV_READ | EV_PERSIST, 1449 server_port_ready_callback, port); 1450 1451 if (event_add(&port->event, NULL) < 0) { 1452 log(EVDNS_LOG_WARN, "Error from libevent when adding event for DNS server."); 1453 /* ???? Do more? */ 1454 } 1455 } 1456 1457 /* set if we are waiting for the ability to write to this server. */ 1458 /* if waiting is true then we ask libevent for EV_WRITE events, otherwise */ 1459 /* we stop these events. */ 1460 static void 1461 nameserver_write_waiting(struct nameserver *ns, char waiting) { 1462 ASSERT_LOCKED(ns->base); 1463 if (ns->write_waiting == waiting) return; 1464 1465 ns->write_waiting = waiting; 1466 (void) event_del(&ns->event); 1467 event_assign(&ns->event, ns->base->event_base, 1468 ns->socket, EV_READ | (waiting ? EV_WRITE : 0) | EV_PERSIST, 1469 nameserver_ready_callback, ns); 1470 if (event_add(&ns->event, NULL) < 0) { 1471 char addrbuf[128]; 1472 log(EVDNS_LOG_WARN, "Error from libevent when adding event for %s", 1473 evutil_format_sockaddr_port( 1474 (struct sockaddr *)&ns->address, 1475 addrbuf, sizeof(addrbuf))); 1476 /* ???? Do more? */ 1477 } 1478 } 1479 1480 /* a callback function. Called by libevent when the kernel says that */ 1481 /* a nameserver socket is ready for writing or reading */ 1482 static void 1483 nameserver_ready_callback(evutil_socket_t fd, short events, void *arg) { 1484 struct nameserver *ns = (struct nameserver *) arg; 1485 (void)fd; 1486 1487 EVDNS_LOCK(ns->base); 1488 if (events & EV_WRITE) { 1489 ns->choked = 0; 1490 if (!evdns_transmit(ns->base)) { 1491 nameserver_write_waiting(ns, 0); 1492 } 1493 } 1494 if (events & EV_READ) { 1495 nameserver_read(ns); 1496 } 1497 EVDNS_UNLOCK(ns->base); 1498 } 1499 1500 /* a callback function. Called by libevent when the kernel says that */ 1501 /* a server socket is ready for writing or reading. */ 1502 static void 1503 server_port_ready_callback(evutil_socket_t fd, short events, void *arg) { 1504 struct evdns_server_port *port = (struct evdns_server_port *) arg; 1505 (void) fd; 1506 1507 EVDNS_LOCK(port); 1508 if (events & EV_WRITE) { 1509 port->choked = 0; 1510 server_port_flush(port); 1511 } 1512 if (events & EV_READ) { 1513 server_port_read(port); 1514 } 1515 EVDNS_UNLOCK(port); 1516 } 1517 1518 /* This is an inefficient representation; only use it via the dnslabel_table_* 1519 * functions, so that is can be safely replaced with something smarter later. */ 1520 #define MAX_LABELS 128 1521 /* Structures used to implement name compression */ 1522 struct dnslabel_entry { char *v; off_t pos; }; 1523 struct dnslabel_table { 1524 int n_labels; /* number of current entries */ 1525 /* map from name to position in message */ 1526 struct dnslabel_entry labels[MAX_LABELS]; 1527 }; 1528 1529 /* Initialize dnslabel_table. */ 1530 static void 1531 dnslabel_table_init(struct dnslabel_table *table) 1532 { 1533 table->n_labels = 0; 1534 } 1535 1536 /* Free all storage held by table, but not the table itself. */ 1537 static void 1538 dnslabel_clear(struct dnslabel_table *table) 1539 { 1540 int i; 1541 for (i = 0; i < table->n_labels; ++i) 1542 mm_free(table->labels[i].v); 1543 table->n_labels = 0; 1544 } 1545 1546 /* return the position of the label in the current message, or -1 if the label */ 1547 /* hasn't been used yet. */ 1548 static int 1549 dnslabel_table_get_pos(const struct dnslabel_table *table, const char *label) 1550 { 1551 int i; 1552 for (i = 0; i < table->n_labels; ++i) { 1553 if (!strcmp(label, table->labels[i].v)) 1554 return table->labels[i].pos; 1555 } 1556 return -1; 1557 } 1558 1559 /* remember that we've used the label at position pos */ 1560 static int 1561 dnslabel_table_add(struct dnslabel_table *table, const char *label, off_t pos) 1562 { 1563 char *v; 1564 int p; 1565 if (table->n_labels == MAX_LABELS) 1566 return (-1); 1567 v = mm_strdup(label); 1568 if (v == NULL) 1569 return (-1); 1570 p = table->n_labels++; 1571 table->labels[p].v = v; 1572 table->labels[p].pos = pos; 1573 1574 return (0); 1575 } 1576 1577 /* Converts a string to a length-prefixed set of DNS labels, starting */ 1578 /* at buf[j]. name and buf must not overlap. name_len should be the length */ 1579 /* of name. table is optional, and is used for compression. */ 1580 /* */ 1581 /* Input: abc.def */ 1582 /* Output: <3>abc<3>def<0> */ 1583 /* */ 1584 /* Returns the first index after the encoded name, or negative on error. */ 1585 /* -1 label was > 63 bytes */ 1586 /* -2 name too long to fit in buffer. */ 1587 /* */ 1588 static off_t 1589 dnsname_to_labels(u8 *const buf, size_t buf_len, off_t j, 1590 const char *name, const size_t name_len, 1591 struct dnslabel_table *table) { 1592 const char *end = name + name_len; 1593 int ref = 0; 1594 u16 _t; 1595 1596 #define APPEND16(x) do { \ 1597 if (j + 2 > (off_t)buf_len) \ 1598 goto overflow; \ 1599 _t = htons(x); \ 1600 memcpy(buf + j, &_t, 2); \ 1601 j += 2; \ 1602 } while (/*CONSTCOND*/0) 1603 #define APPEND32(x) do { \ 1604 if (j + 4 > (off_t)buf_len) \ 1605 goto overflow; \ 1606 _t32 = htonl(x); \ 1607 memcpy(buf + j, &_t32, 4); \ 1608 j += 4; \ 1609 } while (/*CONSTCOND*/0) 1610 1611 if (name_len > 255) return -2; 1612 1613 for (;;) { 1614 const char *const start = name; 1615 if (table && (ref = dnslabel_table_get_pos(table, name)) >= 0) { 1616 APPEND16(ref | 0xc000); 1617 return j; 1618 } 1619 name = strchr(name, '.'); 1620 if (!name) { 1621 const size_t label_len = end - start; 1622 if (label_len > 63) return -1; 1623 if ((size_t)(j+label_len+1) > buf_len) return -2; 1624 if (table) dnslabel_table_add(table, start, j); 1625 buf[j++] = (ev_uint8_t)label_len; 1626 1627 memcpy(buf + j, start, label_len); 1628 j += (int) label_len; 1629 break; 1630 } else { 1631 /* append length of the label. */ 1632 const size_t label_len = name - start; 1633 if (label_len > 63) return -1; 1634 if ((size_t)(j+label_len+1) > buf_len) return -2; 1635 if (table) dnslabel_table_add(table, start, j); 1636 buf[j++] = (ev_uint8_t)label_len; 1637 1638 memcpy(buf + j, start, label_len); 1639 j += (int) label_len; 1640 /* hop over the '.' */ 1641 name++; 1642 } 1643 } 1644 1645 /* the labels must be terminated by a 0. */ 1646 /* It's possible that the name ended in a . */ 1647 /* in which case the zero is already there */ 1648 if (!j || buf[j-1]) buf[j++] = 0; 1649 return j; 1650 overflow: 1651 return (-2); 1652 } 1653 1654 /* Finds the length of a dns request for a DNS name of the given */ 1655 /* length. The actual request may be smaller than the value returned */ 1656 /* here */ 1657 static size_t 1658 evdns_request_len(const size_t name_len) { 1659 return 96 + /* length of the DNS standard header */ 1660 name_len + 2 + 1661 4; /* space for the resource type */ 1662 } 1663 1664 /* build a dns request packet into buf. buf should be at least as long */ 1665 /* as evdns_request_len told you it should be. */ 1666 /* */ 1667 /* Returns the amount of space used. Negative on error. */ 1668 static int 1669 evdns_request_data_build(const char *const name, const size_t name_len, 1670 const u16 trans_id, const u16 type, const u16 class, 1671 u8 *const buf, size_t buf_len) { 1672 off_t j = 0; /* current offset into buf */ 1673 u16 _t; /* used by the macros */ 1674 1675 APPEND16(trans_id); 1676 APPEND16(0x0100); /* standard query, recusion needed */ 1677 APPEND16(1); /* one question */ 1678 APPEND16(0); /* no answers */ 1679 APPEND16(0); /* no authority */ 1680 APPEND16(0); /* no additional */ 1681 1682 j = dnsname_to_labels(buf, buf_len, j, name, name_len, NULL); 1683 if (j < 0) { 1684 return (int)j; 1685 } 1686 1687 APPEND16(type); 1688 APPEND16(class); 1689 1690 return (int)j; 1691 overflow: 1692 return (-1); 1693 } 1694 1695 /* exported function */ 1696 struct evdns_server_port * 1697 evdns_add_server_port_with_base(struct event_base *base, evutil_socket_t socket, int flags, evdns_request_callback_fn_type cb, void *user_data) 1698 { 1699 struct evdns_server_port *port; 1700 if (flags) 1701 return NULL; /* flags not yet implemented */ 1702 if (!(port = mm_malloc(sizeof(struct evdns_server_port)))) 1703 return NULL; 1704 memset(port, 0, sizeof(struct evdns_server_port)); 1705 1706 1707 port->socket = socket; 1708 port->refcnt = 1; 1709 port->choked = 0; 1710 port->closing = 0; 1711 port->user_callback = cb; 1712 port->user_data = user_data; 1713 port->pending_replies = NULL; 1714 port->event_base = base; 1715 1716 event_assign(&port->event, port->event_base, 1717 port->socket, EV_READ | EV_PERSIST, 1718 server_port_ready_callback, port); 1719 if (event_add(&port->event, NULL) < 0) { 1720 mm_free(port); 1721 return NULL; 1722 } 1723 EVTHREAD_ALLOC_LOCK(port->lock, EVTHREAD_LOCKTYPE_RECURSIVE); 1724 return port; 1725 } 1726 1727 struct evdns_server_port * 1728 evdns_add_server_port(evutil_socket_t socket, int flags, evdns_request_callback_fn_type cb, void *user_data) 1729 { 1730 return evdns_add_server_port_with_base(NULL, socket, flags, cb, user_data); 1731 } 1732 1733 /* exported function */ 1734 void 1735 evdns_close_server_port(struct evdns_server_port *port) 1736 { 1737 EVDNS_LOCK(port); 1738 if (--port->refcnt == 0) { 1739 EVDNS_UNLOCK(port); 1740 server_port_free(port); 1741 } else { 1742 port->closing = 1; 1743 } 1744 } 1745 1746 /* exported function */ 1747 int 1748 evdns_server_request_add_reply(struct evdns_server_request *_req, int section, const char *name, int type, int class, int ttl, int datalen, int is_name, const char *data) 1749 { 1750 struct server_request *req = TO_SERVER_REQUEST(_req); 1751 struct server_reply_item **itemp, *item; 1752 int *countp; 1753 int result = -1; 1754 1755 EVDNS_LOCK(req->port); 1756 if (req->response) /* have we already answered? */ 1757 goto done; 1758 1759 switch (section) { 1760 case EVDNS_ANSWER_SECTION: 1761 itemp = &req->answer; 1762 countp = &req->n_answer; 1763 break; 1764 case EVDNS_AUTHORITY_SECTION: 1765 itemp = &req->authority; 1766 countp = &req->n_authority; 1767 break; 1768 case EVDNS_ADDITIONAL_SECTION: 1769 itemp = &req->additional; 1770 countp = &req->n_additional; 1771 break; 1772 default: 1773 goto done; 1774 } 1775 while (*itemp) { 1776 itemp = &((*itemp)->next); 1777 } 1778 item = mm_malloc(sizeof(struct server_reply_item)); 1779 if (!item) 1780 goto done; 1781 item->next = NULL; 1782 if (!(item->name = mm_strdup(name))) { 1783 mm_free(item); 1784 goto done; 1785 } 1786 item->type = type; 1787 item->dns_question_class = class; 1788 item->ttl = ttl; 1789 item->is_name = is_name != 0; 1790 item->datalen = 0; 1791 item->data = NULL; 1792 if (data) { 1793 if (item->is_name) { 1794 if (!(item->data = mm_strdup(data))) { 1795 mm_free(item->name); 1796 mm_free(item); 1797 goto done; 1798 } 1799 item->datalen = (u16)-1; 1800 } else { 1801 if (!(item->data = mm_malloc(datalen))) { 1802 mm_free(item->name); 1803 mm_free(item); 1804 goto done; 1805 } 1806 item->datalen = datalen; 1807 memcpy(item->data, data, datalen); 1808 } 1809 } 1810 1811 *itemp = item; 1812 ++(*countp); 1813 result = 0; 1814 done: 1815 EVDNS_UNLOCK(req->port); 1816 return result; 1817 } 1818 1819 /* exported function */ 1820 int 1821 evdns_server_request_add_a_reply(struct evdns_server_request *req, const char *name, int n, const void *addrs, int ttl) 1822 { 1823 return evdns_server_request_add_reply( 1824 req, EVDNS_ANSWER_SECTION, name, TYPE_A, CLASS_INET, 1825 ttl, n*4, 0, addrs); 1826 } 1827 1828 /* exported function */ 1829 int 1830 evdns_server_request_add_aaaa_reply(struct evdns_server_request *req, const char *name, int n, const void *addrs, int ttl) 1831 { 1832 return evdns_server_request_add_reply( 1833 req, EVDNS_ANSWER_SECTION, name, TYPE_AAAA, CLASS_INET, 1834 ttl, n*16, 0, addrs); 1835 } 1836 1837 /* exported function */ 1838 int 1839 evdns_server_request_add_ptr_reply(struct evdns_server_request *req, struct in_addr *in, const char *inaddr_name, const char *hostname, int ttl) 1840 { 1841 u32 a; 1842 char buf[32]; 1843 if (in && inaddr_name) 1844 return -1; 1845 else if (!in && !inaddr_name) 1846 return -1; 1847 if (in) { 1848 a = ntohl(in->s_addr); 1849 evutil_snprintf(buf, sizeof(buf), "%d.%d.%d.%d.in-addr.arpa", 1850 (int)(u8)((a )&0xff), 1851 (int)(u8)((a>>8 )&0xff), 1852 (int)(u8)((a>>16)&0xff), 1853 (int)(u8)((a>>24)&0xff)); 1854 inaddr_name = buf; 1855 } 1856 return evdns_server_request_add_reply( 1857 req, EVDNS_ANSWER_SECTION, inaddr_name, TYPE_PTR, CLASS_INET, 1858 ttl, -1, 1, hostname); 1859 } 1860 1861 /* exported function */ 1862 int 1863 evdns_server_request_add_cname_reply(struct evdns_server_request *req, const char *name, const char *cname, int ttl) 1864 { 1865 return evdns_server_request_add_reply( 1866 req, EVDNS_ANSWER_SECTION, name, TYPE_CNAME, CLASS_INET, 1867 ttl, -1, 1, cname); 1868 } 1869 1870 /* exported function */ 1871 void 1872 evdns_server_request_set_flags(struct evdns_server_request *exreq, int flags) 1873 { 1874 struct server_request *req = TO_SERVER_REQUEST(exreq); 1875 req->base.flags &= ~(EVDNS_FLAGS_AA|EVDNS_FLAGS_RD); 1876 req->base.flags |= flags; 1877 } 1878 1879 static int 1880 evdns_server_request_format_response(struct server_request *req, int err) 1881 { 1882 unsigned char buf[1500]; 1883 size_t buf_len = sizeof(buf); 1884 off_t j = 0, r; 1885 u16 _t; 1886 u32 _t32; 1887 int i; 1888 u16 flags; 1889 struct dnslabel_table table; 1890 1891 if (err < 0 || err > 15) return -1; 1892 1893 /* Set response bit and error code; copy OPCODE and RD fields from 1894 * question; copy RA and AA if set by caller. */ 1895 flags = req->base.flags; 1896 flags |= (0x8000 | err); 1897 1898 dnslabel_table_init(&table); 1899 APPEND16(req->trans_id); 1900 APPEND16(flags); 1901 APPEND16(req->base.nquestions); 1902 APPEND16(req->n_answer); 1903 APPEND16(req->n_authority); 1904 APPEND16(req->n_additional); 1905 1906 /* Add questions. */ 1907 for (i=0; i < req->base.nquestions; ++i) { 1908 const char *s = req->base.questions[i]->name; 1909 j = dnsname_to_labels(buf, buf_len, j, s, strlen(s), &table); 1910 if (j < 0) { 1911 dnslabel_clear(&table); 1912 return (int) j; 1913 } 1914 APPEND16(req->base.questions[i]->type); 1915 APPEND16(req->base.questions[i]->dns_question_class); 1916 } 1917 1918 /* Add answer, authority, and additional sections. */ 1919 for (i=0; i<3; ++i) { 1920 struct server_reply_item *item; 1921 if (i==0) 1922 item = req->answer; 1923 else if (i==1) 1924 item = req->authority; 1925 else 1926 item = req->additional; 1927 while (item) { 1928 r = dnsname_to_labels(buf, buf_len, j, item->name, strlen(item->name), &table); 1929 if (r < 0) 1930 goto overflow; 1931 j = r; 1932 1933 APPEND16(item->type); 1934 APPEND16(item->dns_question_class); 1935 APPEND32(item->ttl); 1936 if (item->is_name) { 1937 off_t len_idx = j, name_start; 1938 j += 2; 1939 name_start = j; 1940 r = dnsname_to_labels(buf, buf_len, j, item->data, strlen(item->data), &table); 1941 if (r < 0) 1942 goto overflow; 1943 j = r; 1944 _t = htons( (short) (j-name_start) ); 1945 memcpy(buf+len_idx, &_t, 2); 1946 } else { 1947 APPEND16(item->datalen); 1948 if (j+item->datalen > (off_t)buf_len) 1949 goto overflow; 1950 memcpy(buf+j, item->data, item->datalen); 1951 j += item->datalen; 1952 } 1953 item = item->next; 1954 } 1955 } 1956 1957 if (j > 512) { 1958 overflow: 1959 j = 512; 1960 buf[2] |= 0x02; /* set the truncated bit. */ 1961 } 1962 1963 req->response_len = j; 1964 1965 if (!(req->response = mm_malloc(req->response_len))) { 1966 server_request_free_answers(req); 1967 dnslabel_clear(&table); 1968 return (-1); 1969 } 1970 memcpy(req->response, buf, req->response_len); 1971 server_request_free_answers(req); 1972 dnslabel_clear(&table); 1973 return (0); 1974 } 1975 1976 /* exported function */ 1977 int 1978 evdns_server_request_respond(struct evdns_server_request *_req, int err) 1979 { 1980 struct server_request *req = TO_SERVER_REQUEST(_req); 1981 struct evdns_server_port *port = req->port; 1982 int r = -1; 1983 1984 EVDNS_LOCK(port); 1985 if (!req->response) { 1986 if ((r = evdns_server_request_format_response(req, err))<0) 1987 goto done; 1988 } 1989 1990 r = sendto(port->socket, req->response, (int)req->response_len, 0, 1991 (struct sockaddr*) &req->addr, (ev_socklen_t)req->addrlen); 1992 if (r<0) { 1993 int sock_err = evutil_socket_geterror(port->socket); 1994 if (EVUTIL_ERR_RW_RETRIABLE(sock_err)) 1995 goto done; 1996 1997 if (port->pending_replies) { 1998 req->prev_pending = port->pending_replies->prev_pending; 1999 req->next_pending = port->pending_replies; 2000 req->prev_pending->next_pending = 2001 req->next_pending->prev_pending = req; 2002 } else { 2003 req->prev_pending = req->next_pending = req; 2004 port->pending_replies = req; 2005 port->choked = 1; 2006 2007 (void) event_del(&port->event); 2008 event_assign(&port->event, port->event_base, port->socket, (port->closing?0:EV_READ) | EV_WRITE | EV_PERSIST, server_port_ready_callback, port); 2009 2010 if (event_add(&port->event, NULL) < 0) { 2011 log(EVDNS_LOG_WARN, "Error from libevent when adding event for DNS server"); 2012 } 2013 2014 } 2015 2016 r = 1; 2017 goto done; 2018 } 2019 if (server_request_free(req)) { 2020 r = 0; 2021 goto done; 2022 } 2023 2024 if (port->pending_replies) 2025 server_port_flush(port); 2026 2027 r = 0; 2028 done: 2029 EVDNS_UNLOCK(port); 2030 return r; 2031 } 2032 2033 /* Free all storage held by RRs in req. */ 2034 static void 2035 server_request_free_answers(struct server_request *req) 2036 { 2037 struct server_reply_item *victim, *next, **list; 2038 int i; 2039 for (i = 0; i < 3; ++i) { 2040 if (i==0) 2041 list = &req->answer; 2042 else if (i==1) 2043 list = &req->authority; 2044 else 2045 list = &req->additional; 2046 2047 victim = *list; 2048 while (victim) { 2049 next = victim->next; 2050 mm_free(victim->name); 2051 if (victim->data) 2052 mm_free(victim->data); 2053 mm_free(victim); 2054 victim = next; 2055 } 2056 *list = NULL; 2057 } 2058 } 2059 2060 /* Free all storage held by req, and remove links to it. */ 2061 /* return true iff we just wound up freeing the server_port. */ 2062 static int 2063 server_request_free(struct server_request *req) 2064 { 2065 int i, rc=1, lock=0; 2066 if (req->base.questions) { 2067 for (i = 0; i < req->base.nquestions; ++i) 2068 mm_free(req->base.questions[i]); 2069 mm_free(req->base.questions); 2070 } 2071 2072 if (req->port) { 2073 EVDNS_LOCK(req->port); 2074 lock=1; 2075 if (req->port->pending_replies == req) { 2076 if (req->next_pending && req->next_pending != req) 2077 req->port->pending_replies = req->next_pending; 2078 else 2079 req->port->pending_replies = NULL; 2080 } 2081 rc = --req->port->refcnt; 2082 } 2083 2084 if (req->response) { 2085 mm_free(req->response); 2086 } 2087 2088 server_request_free_answers(req); 2089 2090 if (req->next_pending && req->next_pending != req) { 2091 req->next_pending->prev_pending = req->prev_pending; 2092 req->prev_pending->next_pending = req->next_pending; 2093 } 2094 2095 if (rc == 0) { 2096 EVDNS_UNLOCK(req->port); /* ????? nickm */ 2097 server_port_free(req->port); 2098 mm_free(req); 2099 return (1); 2100 } 2101 if (lock) 2102 EVDNS_UNLOCK(req->port); 2103 mm_free(req); 2104 return (0); 2105 } 2106 2107 /* Free all storage held by an evdns_server_port. Only called when */ 2108 static void 2109 server_port_free(struct evdns_server_port *port) 2110 { 2111 EVUTIL_ASSERT(port); 2112 EVUTIL_ASSERT(!port->refcnt); 2113 EVUTIL_ASSERT(!port->pending_replies); 2114 if (port->socket > 0) { 2115 evutil_closesocket(port->socket); 2116 port->socket = -1; 2117 } 2118 (void) event_del(&port->event); 2119 event_debug_unassign(&port->event); 2120 EVTHREAD_FREE_LOCK(port->lock, EVTHREAD_LOCKTYPE_RECURSIVE); 2121 mm_free(port); 2122 } 2123 2124 /* exported function */ 2125 int 2126 evdns_server_request_drop(struct evdns_server_request *_req) 2127 { 2128 struct server_request *req = TO_SERVER_REQUEST(_req); 2129 server_request_free(req); 2130 return 0; 2131 } 2132 2133 /* exported function */ 2134 int 2135 evdns_server_request_get_requesting_addr(struct evdns_server_request *_req, struct sockaddr *sa, int addr_len) 2136 { 2137 struct server_request *req = TO_SERVER_REQUEST(_req); 2138 if (addr_len < (int)req->addrlen) 2139 return -1; 2140 memcpy(sa, &(req->addr), req->addrlen); 2141 return req->addrlen; 2142 } 2143 2144 #undef APPEND16 2145 #undef APPEND32 2146 2147 /* this is a libevent callback function which is called when a request */ 2148 /* has timed out. */ 2149 static void 2150 evdns_request_timeout_callback(evutil_socket_t fd, short events, void *arg) { 2151 struct request *const req = (struct request *) arg; 2152 struct evdns_base *base = req->base; 2153 2154 (void) fd; 2155 (void) events; 2156 2157 log(EVDNS_LOG_DEBUG, "Request %p timed out", arg); 2158 EVDNS_LOCK(base); 2159 2160 req->ns->timedout++; 2161 if (req->ns->timedout > req->base->global_max_nameserver_timeout) { 2162 req->ns->timedout = 0; 2163 nameserver_failed(req->ns, "request timed out."); 2164 } 2165 2166 if (req->tx_count >= req->base->global_max_retransmits) { 2167 /* this request has failed */ 2168 log(EVDNS_LOG_DEBUG, "Giving up on request %p; tx_count==%d", 2169 arg, req->tx_count); 2170 reply_schedule_callback(req, 0, DNS_ERR_TIMEOUT, NULL); 2171 request_finished(req, &REQ_HEAD(req->base, req->trans_id), 1); 2172 } else { 2173 /* retransmit it */ 2174 struct nameserver *new_ns; 2175 log(EVDNS_LOG_DEBUG, "Retransmitting request %p; tx_count==%d", 2176 arg, req->tx_count); 2177 (void) evtimer_del(&req->timeout_event); 2178 new_ns = nameserver_pick(base); 2179 if (new_ns) 2180 req->ns = new_ns; 2181 evdns_request_transmit(req); 2182 } 2183 EVDNS_UNLOCK(base); 2184 } 2185 2186 /* try to send a request to a given server. */ 2187 /* */ 2188 /* return: */ 2189 /* 0 ok */ 2190 /* 1 temporary failure */ 2191 /* 2 other failure */ 2192 static int 2193 evdns_request_transmit_to(struct request *req, struct nameserver *server) { 2194 int r; 2195 ASSERT_LOCKED(req->base); 2196 ASSERT_VALID_REQUEST(req); 2197 r = sendto(server->socket, (void*)req->request, req->request_len, 0, 2198 (struct sockaddr *)&server->address, server->addrlen); 2199 if (r < 0) { 2200 int err = evutil_socket_geterror(server->socket); 2201 if (EVUTIL_ERR_RW_RETRIABLE(err)) 2202 return 1; 2203 nameserver_failed(req->ns, evutil_socket_error_to_string(err)); 2204 return 2; 2205 } else if (r != (int)req->request_len) { 2206 return 1; /* short write */ 2207 } else { 2208 return 0; 2209 } 2210 } 2211 2212 /* try to send a request, updating the fields of the request */ 2213 /* as needed */ 2214 /* */ 2215 /* return: */ 2216 /* 0 ok */ 2217 /* 1 failed */ 2218 static int 2219 evdns_request_transmit(struct request *req) { 2220 int retcode = 0, r; 2221 2222 ASSERT_LOCKED(req->base); 2223 ASSERT_VALID_REQUEST(req); 2224 /* if we fail to send this packet then this flag marks it */ 2225 /* for evdns_transmit */ 2226 req->transmit_me = 1; 2227 EVUTIL_ASSERT(req->trans_id != 0xffff); 2228 2229 if (!req->ns) 2230 { 2231 /* unable to transmit request if no nameservers */ 2232 return 1; 2233 } 2234 2235 if (req->ns->choked) { 2236 /* don't bother trying to write to a socket */ 2237 /* which we have had EAGAIN from */ 2238 return 1; 2239 } 2240 2241 r = evdns_request_transmit_to(req, req->ns); 2242 switch (r) { 2243 case 1: 2244 /* temp failure */ 2245 req->ns->choked = 1; 2246 nameserver_write_waiting(req->ns, 1); 2247 return 1; 2248 case 2: 2249 /* failed to transmit the request entirely. */ 2250 retcode = 1; 2251 /* fall through: we'll set a timeout, which will time out, 2252 * and make us retransmit the request anyway. */ 2253 default: 2254 /* all ok */ 2255 log(EVDNS_LOG_DEBUG, 2256 "Setting timeout for request %p, sent to nameserver %p", req, req->ns); 2257 if (evtimer_add(&req->timeout_event, &req->base->global_timeout) < 0) { 2258 log(EVDNS_LOG_WARN, 2259 "Error from libevent when adding timer for request %p", 2260 req); 2261 /* ???? Do more? */ 2262 } 2263 req->tx_count++; 2264 req->transmit_me = 0; 2265 return retcode; 2266 } 2267 } 2268 2269 static void 2270 nameserver_probe_callback(int result, char type, int count, int ttl, void *addresses, void *arg) { 2271 struct nameserver *const ns = (struct nameserver *) arg; 2272 (void) type; 2273 (void) count; 2274 (void) ttl; 2275 (void) addresses; 2276 2277 if (result == DNS_ERR_CANCEL) { 2278 /* We canceled this request because the nameserver came up 2279 * for some other reason. Do not change our opinion about 2280 * the nameserver. */ 2281 return; 2282 } 2283 2284 EVDNS_LOCK(ns->base); 2285 ns->probe_request = NULL; 2286 if (result == DNS_ERR_NONE || result == DNS_ERR_NOTEXIST) { 2287 /* this is a good reply */ 2288 nameserver_up(ns); 2289 } else { 2290 nameserver_probe_failed(ns); 2291 } 2292 EVDNS_UNLOCK(ns->base); 2293 } 2294 2295 static void 2296 nameserver_send_probe(struct nameserver *const ns) { 2297 struct evdns_request *handle; 2298 struct request *req; 2299 char addrbuf[128]; 2300 /* here we need to send a probe to a given nameserver */ 2301 /* in the hope that it is up now. */ 2302 2303 ASSERT_LOCKED(ns->base); 2304 log(EVDNS_LOG_DEBUG, "Sending probe to %s", 2305 evutil_format_sockaddr_port( 2306 (struct sockaddr *)&ns->address, 2307 addrbuf, sizeof(addrbuf))); 2308 handle = mm_calloc(1, sizeof(*handle)); 2309 if (!handle) return; 2310 req = request_new(ns->base, handle, TYPE_A, "google.com", DNS_QUERY_NO_SEARCH, nameserver_probe_callback, ns); 2311 if (!req) { 2312 mm_free(handle); 2313 return; 2314 } 2315 ns->probe_request = handle; 2316 /* we force this into the inflight queue no matter what */ 2317 request_trans_id_set(req, transaction_id_pick(ns->base)); 2318 req->ns = ns; 2319 request_submit(req); 2320 } 2321 2322 /* returns: */ 2323 /* 0 didn't try to transmit anything */ 2324 /* 1 tried to transmit something */ 2325 static int 2326 evdns_transmit(struct evdns_base *base) { 2327 char did_try_to_transmit = 0; 2328 int i; 2329 2330 ASSERT_LOCKED(base); 2331 for (i = 0; i < base->n_req_heads; ++i) { 2332 if (base->req_heads[i]) { 2333 struct request *const started_at = base->req_heads[i], *req = started_at; 2334 /* first transmit all the requests which are currently waiting */ 2335 do { 2336 if (req->transmit_me) { 2337 did_try_to_transmit = 1; 2338 evdns_request_transmit(req); 2339 } 2340 2341 req = req->next; 2342 } while (req != started_at); 2343 } 2344 } 2345 2346 return did_try_to_transmit; 2347 } 2348 2349 /* exported function */ 2350 int 2351 evdns_base_count_nameservers(struct evdns_base *base) 2352 { 2353 const struct nameserver *server; 2354 int n = 0; 2355 2356 EVDNS_LOCK(base); 2357 server = base->server_head; 2358 if (!server) 2359 goto done; 2360 do { 2361 ++n; 2362 server = server->next; 2363 } while (server != base->server_head); 2364 done: 2365 EVDNS_UNLOCK(base); 2366 return n; 2367 } 2368 2369 int 2370 evdns_count_nameservers(void) 2371 { 2372 return evdns_base_count_nameservers(current_base); 2373 } 2374 2375 /* exported function */ 2376 int 2377 evdns_base_clear_nameservers_and_suspend(struct evdns_base *base) 2378 { 2379 struct nameserver *server, *started_at; 2380 int i; 2381 2382 EVDNS_LOCK(base); 2383 server = base->server_head; 2384 started_at = base->server_head; 2385 if (!server) { 2386 EVDNS_UNLOCK(base); 2387 return 0; 2388 } 2389 while (1) { 2390 struct nameserver *next = server->next; 2391 (void) event_del(&server->event); 2392 if (evtimer_initialized(&server->timeout_event)) 2393 (void) evtimer_del(&server->timeout_event); 2394 if (server->probe_request) { 2395 evdns_cancel_request(server->base, server->probe_request); 2396 server->probe_request = NULL; 2397 } 2398 if (server->socket >= 0) 2399 evutil_closesocket(server->socket); 2400 mm_free(server); 2401 if (next == started_at) 2402 break; 2403 server = next; 2404 } 2405 base->server_head = NULL; 2406 base->global_good_nameservers = 0; 2407 2408 for (i = 0; i < base->n_req_heads; ++i) { 2409 struct request *req, *req_started_at; 2410 req = req_started_at = base->req_heads[i]; 2411 while (req) { 2412 struct request *next = req->next; 2413 req->tx_count = req->reissue_count = 0; 2414 req->ns = NULL; 2415 /* ???? What to do about searches? */ 2416 (void) evtimer_del(&req->timeout_event); 2417 req->trans_id = 0; 2418 req->transmit_me = 0; 2419 2420 base->global_requests_waiting++; 2421 evdns_request_insert(req, &base->req_waiting_head); 2422 /* We want to insert these suspended elements at the front of 2423 * the waiting queue, since they were pending before any of 2424 * the waiting entries were added. This is a circular list, 2425 * so we can just shift the start back by one.*/ 2426 base->req_waiting_head = base->req_waiting_head->prev; 2427 2428 if (next == req_started_at) 2429 break; 2430 req = next; 2431 } 2432 base->req_heads[i] = NULL; 2433 } 2434 2435 base->global_requests_inflight = 0; 2436 2437 EVDNS_UNLOCK(base); 2438 return 0; 2439 } 2440 2441 int 2442 evdns_clear_nameservers_and_suspend(void) 2443 { 2444 return evdns_base_clear_nameservers_and_suspend(current_base); 2445 } 2446 2447 2448 /* exported function */ 2449 int 2450 evdns_base_resume(struct evdns_base *base) 2451 { 2452 EVDNS_LOCK(base); 2453 evdns_requests_pump_waiting_queue(base); 2454 EVDNS_UNLOCK(base); 2455 2456 return 0; 2457 } 2458 2459 int 2460 evdns_resume(void) 2461 { 2462 return evdns_base_resume(current_base); 2463 } 2464 2465 static int 2466 _evdns_nameserver_add_impl(struct evdns_base *base, const struct sockaddr *address, int addrlen) { 2467 /* first check to see if we already have this nameserver */ 2468 2469 const struct nameserver *server = base->server_head, *const started_at = base->server_head; 2470 struct nameserver *ns; 2471 int err = 0; 2472 char addrbuf[128]; 2473 2474 ASSERT_LOCKED(base); 2475 if (server) { 2476 do { 2477 if (!evutil_sockaddr_cmp((const struct sockaddr*)&server->address, address, 1)) return 3; 2478 server = server->next; 2479 } while (server != started_at); 2480 } 2481 if (addrlen > (int)sizeof(ns->address)) { 2482 log(EVDNS_LOG_DEBUG, "Addrlen %d too long.", (int)addrlen); 2483 return 2; 2484 } 2485 2486 ns = (struct nameserver *) mm_malloc(sizeof(struct nameserver)); 2487 if (!ns) return -1; 2488 2489 memset(ns, 0, sizeof(struct nameserver)); 2490 ns->base = base; 2491 2492 evtimer_assign(&ns->timeout_event, ns->base->event_base, nameserver_prod_callback, ns); 2493 2494 ns->socket = socket(address->sa_family, SOCK_DGRAM, 0); 2495 if (ns->socket < 0) { err = 1; goto out1; } 2496 evutil_make_socket_closeonexec(ns->socket); 2497 evutil_make_socket_nonblocking(ns->socket); 2498 2499 if (base->global_outgoing_addrlen && 2500 !evutil_sockaddr_is_loopback(address)) { 2501 if (bind(ns->socket, 2502 (struct sockaddr*)&base->global_outgoing_address, 2503 base->global_outgoing_addrlen) < 0) { 2504 log(EVDNS_LOG_WARN,"Couldn't bind to outgoing address"); 2505 err = 2; 2506 goto out2; 2507 } 2508 } 2509 2510 memcpy(&ns->address, address, addrlen); 2511 ns->addrlen = addrlen; 2512 ns->state = 1; 2513 event_assign(&ns->event, ns->base->event_base, ns->socket, EV_READ | EV_PERSIST, nameserver_ready_callback, ns); 2514 if (event_add(&ns->event, NULL) < 0) { 2515 err = 2; 2516 goto out2; 2517 } 2518 2519 log(EVDNS_LOG_DEBUG, "Added nameserver %s as %p", 2520 evutil_format_sockaddr_port(address, addrbuf, sizeof(addrbuf)), ns); 2521 2522 /* insert this nameserver into the list of them */ 2523 if (!base->server_head) { 2524 ns->next = ns->prev = ns; 2525 base->server_head = ns; 2526 } else { 2527 ns->next = base->server_head->next; 2528 ns->prev = base->server_head; 2529 base->server_head->next = ns; 2530 ns->next->prev = ns; 2531 } 2532 2533 base->global_good_nameservers++; 2534 2535 return 0; 2536 2537 out2: 2538 evutil_closesocket(ns->socket); 2539 out1: 2540 event_debug_unassign(&ns->event); 2541 mm_free(ns); 2542 log(EVDNS_LOG_WARN, "Unable to add nameserver %s: error %d", 2543 evutil_format_sockaddr_port(address, addrbuf, sizeof(addrbuf)), err); 2544 return err; 2545 } 2546 2547 /* exported function */ 2548 int 2549 evdns_base_nameserver_add(struct evdns_base *base, unsigned long int address) 2550 { 2551 struct sockaddr_in sin; 2552 int res; 2553 memset(&sin, 0, sizeof(sin)); 2554 sin.sin_addr.s_addr = address; 2555 sin.sin_port = htons(53); 2556 sin.sin_family = AF_INET; 2557 EVDNS_LOCK(base); 2558 res = _evdns_nameserver_add_impl(base, (struct sockaddr*)&sin, sizeof(sin)); 2559 EVDNS_UNLOCK(base); 2560 return res; 2561 } 2562 2563 int 2564 evdns_nameserver_add(unsigned long int address) { 2565 if (!current_base) 2566 current_base = evdns_base_new(NULL, 0); 2567 return evdns_base_nameserver_add(current_base, address); 2568 } 2569 2570 static void 2571 sockaddr_setport(struct sockaddr *sa, ev_uint16_t port) 2572 { 2573 if (sa->sa_family == AF_INET) { 2574 ((struct sockaddr_in *)sa)->sin_port = htons(port); 2575 } else if (sa->sa_family == AF_INET6) { 2576 ((struct sockaddr_in6 *)sa)->sin6_port = htons(port); 2577 } 2578 } 2579 2580 static ev_uint16_t 2581 sockaddr_getport(struct sockaddr *sa) 2582 { 2583 if (sa->sa_family == AF_INET) { 2584 return ntohs(((struct sockaddr_in *)sa)->sin_port); 2585 } else if (sa->sa_family == AF_INET6) { 2586 return ntohs(((struct sockaddr_in6 *)sa)->sin6_port); 2587 } else { 2588 return 0; 2589 } 2590 } 2591 2592 /* exported function */ 2593 int 2594 evdns_base_nameserver_ip_add(struct evdns_base *base, const char *ip_as_string) { 2595 struct sockaddr_storage ss; 2596 struct sockaddr *sa; 2597 int len = sizeof(ss); 2598 int res; 2599 if (evutil_parse_sockaddr_port(ip_as_string, (struct sockaddr *)&ss, 2600 &len)) { 2601 log(EVDNS_LOG_WARN, "Unable to parse nameserver address %s", 2602 ip_as_string); 2603 return 4; 2604 } 2605 sa = (struct sockaddr *) &ss; 2606 if (sockaddr_getport(sa) == 0) 2607 sockaddr_setport(sa, 53); 2608 2609 EVDNS_LOCK(base); 2610 res = _evdns_nameserver_add_impl(base, sa, len); 2611 EVDNS_UNLOCK(base); 2612 return res; 2613 } 2614 2615 int 2616 evdns_nameserver_ip_add(const char *ip_as_string) { 2617 if (!current_base) 2618 current_base = evdns_base_new(NULL, 0); 2619 return evdns_base_nameserver_ip_add(current_base, ip_as_string); 2620 } 2621 2622 int 2623 evdns_base_nameserver_sockaddr_add(struct evdns_base *base, 2624 const struct sockaddr *sa, ev_socklen_t len, unsigned flags) 2625 { 2626 int res; 2627 EVUTIL_ASSERT(base); 2628 EVDNS_LOCK(base); 2629 res = _evdns_nameserver_add_impl(base, sa, len); 2630 EVDNS_UNLOCK(base); 2631 return res; 2632 } 2633 2634 /* remove from the queue */ 2635 static void 2636 evdns_request_remove(struct request *req, struct request **head) 2637 { 2638 ASSERT_LOCKED(req->base); 2639 ASSERT_VALID_REQUEST(req); 2640 2641 #if 0 2642 { 2643 struct request *ptr; 2644 int found = 0; 2645 EVUTIL_ASSERT(*head != NULL); 2646 2647 ptr = *head; 2648 do { 2649 if (ptr == req) { 2650 found = 1; 2651 break; 2652 } 2653 ptr = ptr->next; 2654 } while (ptr != *head); 2655 EVUTIL_ASSERT(found); 2656 2657 EVUTIL_ASSERT(req->next); 2658 } 2659 #endif 2660 2661 if (req->next == req) { 2662 /* only item in the list */ 2663 *head = NULL; 2664 } else { 2665 req->next->prev = req->prev; 2666 req->prev->next = req->next; 2667 if (*head == req) *head = req->next; 2668 } 2669 req->next = req->prev = NULL; 2670 } 2671 2672 /* insert into the tail of the queue */ 2673 static void 2674 evdns_request_insert(struct request *req, struct request **head) { 2675 ASSERT_LOCKED(req->base); 2676 ASSERT_VALID_REQUEST(req); 2677 if (!*head) { 2678 *head = req; 2679 req->next = req->prev = req; 2680 return; 2681 } 2682 2683 req->prev = (*head)->prev; 2684 req->prev->next = req; 2685 req->next = *head; 2686 (*head)->prev = req; 2687 } 2688 2689 static int 2690 string_num_dots(const char *s) { 2691 int count = 0; 2692 while ((s = strchr(s, '.'))) { 2693 s++; 2694 count++; 2695 } 2696 return count; 2697 } 2698 2699 static struct request * 2700 request_new(struct evdns_base *base, struct evdns_request *handle, int type, 2701 const char *name, int flags, evdns_callback_type callback, 2702 void *user_ptr) { 2703 2704 const char issuing_now = 2705 (base->global_requests_inflight < base->global_max_requests_inflight) ? 1 : 0; 2706 2707 const size_t name_len = strlen(name); 2708 const size_t request_max_len = evdns_request_len(name_len); 2709 const u16 trans_id = issuing_now ? transaction_id_pick(base) : 0xffff; 2710 /* the request data is alloced in a single block with the header */ 2711 struct request *const req = 2712 mm_malloc(sizeof(struct request) + request_max_len); 2713 int rlen; 2714 char namebuf[256]; 2715 (void) flags; 2716 2717 ASSERT_LOCKED(base); 2718 2719 if (!req) return NULL; 2720 2721 if (name_len >= sizeof(namebuf)) { 2722 mm_free(req); 2723 return NULL; 2724 } 2725 2726 memset(req, 0, sizeof(struct request)); 2727 req->base = base; 2728 2729 evtimer_assign(&req->timeout_event, req->base->event_base, evdns_request_timeout_callback, req); 2730 2731 if (base->global_randomize_case) { 2732 unsigned i; 2733 char randbits[(sizeof(namebuf)+7)/8]; 2734 strlcpy(namebuf, name, sizeof(namebuf)); 2735 evutil_secure_rng_get_bytes(randbits, (name_len+7)/8); 2736 for (i = 0; i < name_len; ++i) { 2737 if (EVUTIL_ISALPHA(namebuf[i])) { 2738 if ((randbits[i >> 3] & (1<<(i & 7)))) 2739 namebuf[i] |= 0x20; 2740 else 2741 namebuf[i] &= ~0x20; 2742 } 2743 } 2744 name = namebuf; 2745 } 2746 2747 /* request data lives just after the header */ 2748 req->request = ((u8 *) req) + sizeof(struct request); 2749 /* denotes that the request data shouldn't be free()ed */ 2750 req->request_appended = 1; 2751 rlen = evdns_request_data_build(name, name_len, trans_id, 2752 type, CLASS_INET, req->request, request_max_len); 2753 if (rlen < 0) 2754 goto err1; 2755 2756 req->request_len = rlen; 2757 req->trans_id = trans_id; 2758 req->tx_count = 0; 2759 req->request_type = type; 2760 req->user_pointer = user_ptr; 2761 req->user_callback = callback; 2762 req->ns = issuing_now ? nameserver_pick(base) : NULL; 2763 req->next = req->prev = NULL; 2764 req->handle = handle; 2765 if (handle) { 2766 handle->current_req = req; 2767 handle->base = base; 2768 } 2769 2770 return req; 2771 err1: 2772 mm_free(req); 2773 return NULL; 2774 } 2775 2776 static void 2777 request_submit(struct request *const req) { 2778 struct evdns_base *base = req->base; 2779 ASSERT_LOCKED(base); 2780 ASSERT_VALID_REQUEST(req); 2781 if (req->ns) { 2782 /* if it has a nameserver assigned then this is going */ 2783 /* straight into the inflight queue */ 2784 evdns_request_insert(req, &REQ_HEAD(base, req->trans_id)); 2785 base->global_requests_inflight++; 2786 evdns_request_transmit(req); 2787 } else { 2788 evdns_request_insert(req, &base->req_waiting_head); 2789 base->global_requests_waiting++; 2790 } 2791 } 2792 2793 /* exported function */ 2794 void 2795 evdns_cancel_request(struct evdns_base *base, struct evdns_request *handle) 2796 { 2797 struct request *req; 2798 2799 if (!handle->current_req) 2800 return; 2801 2802 if (!base) { 2803 /* This redundancy is silly; can we fix it? (Not for 2.0) XXXX */ 2804 base = handle->base; 2805 if (!base) 2806 base = handle->current_req->base; 2807 } 2808 2809 EVDNS_LOCK(base); 2810 if (handle->pending_cb) { 2811 EVDNS_UNLOCK(base); 2812 return; 2813 } 2814 2815 req = handle->current_req; 2816 ASSERT_VALID_REQUEST(req); 2817 2818 reply_schedule_callback(req, 0, DNS_ERR_CANCEL, NULL); 2819 if (req->ns) { 2820 /* remove from inflight queue */ 2821 request_finished(req, &REQ_HEAD(base, req->trans_id), 1); 2822 } else { 2823 /* remove from global_waiting head */ 2824 request_finished(req, &base->req_waiting_head, 1); 2825 } 2826 EVDNS_UNLOCK(base); 2827 } 2828 2829 /* exported function */ 2830 struct evdns_request * 2831 evdns_base_resolve_ipv4(struct evdns_base *base, const char *name, int flags, 2832 evdns_callback_type callback, void *ptr) { 2833 struct evdns_request *handle; 2834 struct request *req; 2835 log(EVDNS_LOG_DEBUG, "Resolve requested for %s", name); 2836 handle = mm_calloc(1, sizeof(*handle)); 2837 if (handle == NULL) 2838 return NULL; 2839 EVDNS_LOCK(base); 2840 if (flags & DNS_QUERY_NO_SEARCH) { 2841 req = 2842 request_new(base, handle, TYPE_A, name, flags, 2843 callback, ptr); 2844 if (req) 2845 request_submit(req); 2846 } else { 2847 search_request_new(base, handle, TYPE_A, name, flags, 2848 callback, ptr); 2849 } 2850 if (handle->current_req == NULL) { 2851 mm_free(handle); 2852 handle = NULL; 2853 } 2854 EVDNS_UNLOCK(base); 2855 return handle; 2856 } 2857 2858 int evdns_resolve_ipv4(const char *name, int flags, 2859 evdns_callback_type callback, void *ptr) 2860 { 2861 return evdns_base_resolve_ipv4(current_base, name, flags, callback, ptr) 2862 ? 0 : -1; 2863 } 2864 2865 2866 /* exported function */ 2867 struct evdns_request * 2868 evdns_base_resolve_ipv6(struct evdns_base *base, 2869 const char *name, int flags, 2870 evdns_callback_type callback, void *ptr) 2871 { 2872 struct evdns_request *handle; 2873 struct request *req; 2874 log(EVDNS_LOG_DEBUG, "Resolve requested for %s", name); 2875 handle = mm_calloc(1, sizeof(*handle)); 2876 if (handle == NULL) 2877 return NULL; 2878 EVDNS_LOCK(base); 2879 if (flags & DNS_QUERY_NO_SEARCH) { 2880 req = request_new(base, handle, TYPE_AAAA, name, flags, 2881 callback, ptr); 2882 if (req) 2883 request_submit(req); 2884 } else { 2885 search_request_new(base, handle, TYPE_AAAA, name, flags, 2886 callback, ptr); 2887 } 2888 if (handle->current_req == NULL) { 2889 mm_free(handle); 2890 handle = NULL; 2891 } 2892 EVDNS_UNLOCK(base); 2893 return handle; 2894 } 2895 2896 int evdns_resolve_ipv6(const char *name, int flags, 2897 evdns_callback_type callback, void *ptr) { 2898 return evdns_base_resolve_ipv6(current_base, name, flags, callback, ptr) 2899 ? 0 : -1; 2900 } 2901 2902 struct evdns_request * 2903 evdns_base_resolve_reverse(struct evdns_base *base, const struct in_addr *in, int flags, evdns_callback_type callback, void *ptr) { 2904 char buf[32]; 2905 struct evdns_request *handle; 2906 struct request *req; 2907 u32 a; 2908 EVUTIL_ASSERT(in); 2909 a = ntohl(in->s_addr); 2910 evutil_snprintf(buf, sizeof(buf), "%d.%d.%d.%d.in-addr.arpa", 2911 (int)(u8)((a )&0xff), 2912 (int)(u8)((a>>8 )&0xff), 2913 (int)(u8)((a>>16)&0xff), 2914 (int)(u8)((a>>24)&0xff)); 2915 handle = mm_calloc(1, sizeof(*handle)); 2916 if (handle == NULL) 2917 return NULL; 2918 log(EVDNS_LOG_DEBUG, "Resolve requested for %s (reverse)", buf); 2919 EVDNS_LOCK(base); 2920 req = request_new(base, handle, TYPE_PTR, buf, flags, callback, ptr); 2921 if (req) 2922 request_submit(req); 2923 if (handle->current_req == NULL) { 2924 mm_free(handle); 2925 handle = NULL; 2926 } 2927 EVDNS_UNLOCK(base); 2928 return (handle); 2929 } 2930 2931 int evdns_resolve_reverse(const struct in_addr *in, int flags, evdns_callback_type callback, void *ptr) { 2932 return evdns_base_resolve_reverse(current_base, in, flags, callback, ptr) 2933 ? 0 : -1; 2934 } 2935 2936 struct evdns_request * 2937 evdns_base_resolve_reverse_ipv6(struct evdns_base *base, const struct in6_addr *in, int flags, evdns_callback_type callback, void *ptr) { 2938 /* 32 nybbles, 32 periods, "ip6.arpa", NUL. */ 2939 char buf[73]; 2940 char *cp; 2941 struct evdns_request *handle; 2942 struct request *req; 2943 int i; 2944 EVUTIL_ASSERT(in); 2945 cp = buf; 2946 for (i=15; i >= 0; --i) { 2947 u8 byte = in->s6_addr[i]; 2948 *cp++ = "0123456789abcdef"[byte & 0x0f]; 2949 *cp++ = '.'; 2950 *cp++ = "0123456789abcdef"[byte >> 4]; 2951 *cp++ = '.'; 2952 } 2953 EVUTIL_ASSERT(cp + strlen("ip6.arpa") < buf+sizeof(buf)); 2954 memcpy(cp, "ip6.arpa", strlen("ip6.arpa")+1); 2955 handle = mm_calloc(1, sizeof(*handle)); 2956 if (handle == NULL) 2957 return NULL; 2958 log(EVDNS_LOG_DEBUG, "Resolve requested for %s (reverse)", buf); 2959 EVDNS_LOCK(base); 2960 req = request_new(base, handle, TYPE_PTR, buf, flags, callback, ptr); 2961 if (req) 2962 request_submit(req); 2963 if (handle->current_req == NULL) { 2964 mm_free(handle); 2965 handle = NULL; 2966 } 2967 EVDNS_UNLOCK(base); 2968 return (handle); 2969 } 2970 2971 int evdns_resolve_reverse_ipv6(const struct in6_addr *in, int flags, evdns_callback_type callback, void *ptr) { 2972 return evdns_base_resolve_reverse_ipv6(current_base, in, flags, callback, ptr) 2973 ? 0 : -1; 2974 } 2975 2976 /* ================================================================= */ 2977 /* Search support */ 2978 /* */ 2979 /* the libc resolver has support for searching a number of domains */ 2980 /* to find a name. If nothing else then it takes the single domain */ 2981 /* from the gethostname() call. */ 2982 /* */ 2983 /* It can also be configured via the domain and search options in a */ 2984 /* resolv.conf. */ 2985 /* */ 2986 /* The ndots option controls how many dots it takes for the resolver */ 2987 /* to decide that a name is non-local and so try a raw lookup first. */ 2988 2989 struct search_domain { 2990 int len; 2991 struct search_domain *next; 2992 /* the text string is appended to this structure */ 2993 }; 2994 2995 struct search_state { 2996 int refcount; 2997 int ndots; 2998 int num_domains; 2999 struct search_domain *head; 3000 }; 3001 3002 static void 3003 search_state_decref(struct search_state *const state) { 3004 if (!state) return; 3005 state->refcount--; 3006 if (!state->refcount) { 3007 struct search_domain *next, *dom; 3008 for (dom = state->head; dom; dom = next) { 3009 next = dom->next; 3010 mm_free(dom); 3011 } 3012 mm_free(state); 3013 } 3014 } 3015 3016 static struct search_state * 3017 search_state_new(void) { 3018 struct search_state *state = (struct search_state *) mm_malloc(sizeof(struct search_state)); 3019 if (!state) return NULL; 3020 memset(state, 0, sizeof(struct search_state)); 3021 state->refcount = 1; 3022 state->ndots = 1; 3023 3024 return state; 3025 } 3026 3027 static void 3028 search_postfix_clear(struct evdns_base *base) { 3029 search_state_decref(base->global_search_state); 3030 3031 base->global_search_state = search_state_new(); 3032 } 3033 3034 /* exported function */ 3035 void 3036 evdns_base_search_clear(struct evdns_base *base) 3037 { 3038 EVDNS_LOCK(base); 3039 search_postfix_clear(base); 3040 EVDNS_UNLOCK(base); 3041 } 3042 3043 void 3044 evdns_search_clear(void) { 3045 evdns_base_search_clear(current_base); 3046 } 3047 3048 static void 3049 search_postfix_add(struct evdns_base *base, const char *domain) { 3050 size_t domain_len; 3051 struct search_domain *sdomain; 3052 while (domain[0] == '.') domain++; 3053 domain_len = strlen(domain); 3054 3055 ASSERT_LOCKED(base); 3056 if (!base->global_search_state) base->global_search_state = search_state_new(); 3057 if (!base->global_search_state) return; 3058 base->global_search_state->num_domains++; 3059 3060 sdomain = (struct search_domain *) mm_malloc(sizeof(struct search_domain) + domain_len); 3061 if (!sdomain) return; 3062 memcpy( ((u8 *) sdomain) + sizeof(struct search_domain), domain, domain_len); 3063 sdomain->next = base->global_search_state->head; 3064 sdomain->len = (int) domain_len; 3065 3066 base->global_search_state->head = sdomain; 3067 } 3068 3069 /* reverse the order of members in the postfix list. This is needed because, */ 3070 /* when parsing resolv.conf we push elements in the wrong order */ 3071 static void 3072 search_reverse(struct evdns_base *base) { 3073 struct search_domain *cur, *prev = NULL, *next; 3074 ASSERT_LOCKED(base); 3075 cur = base->global_search_state->head; 3076 while (cur) { 3077 next = cur->next; 3078 cur->next = prev; 3079 prev = cur; 3080 cur = next; 3081 } 3082 3083 base->global_search_state->head = prev; 3084 } 3085 3086 /* exported function */ 3087 void 3088 evdns_base_search_add(struct evdns_base *base, const char *domain) { 3089 EVDNS_LOCK(base); 3090 search_postfix_add(base, domain); 3091 EVDNS_UNLOCK(base); 3092 } 3093 void 3094 evdns_search_add(const char *domain) { 3095 evdns_base_search_add(current_base, domain); 3096 } 3097 3098 /* exported function */ 3099 void 3100 evdns_base_search_ndots_set(struct evdns_base *base, const int ndots) { 3101 EVDNS_LOCK(base); 3102 if (!base->global_search_state) base->global_search_state = search_state_new(); 3103 if (base->global_search_state) 3104 base->global_search_state->ndots = ndots; 3105 EVDNS_UNLOCK(base); 3106 } 3107 void 3108 evdns_search_ndots_set(const int ndots) { 3109 evdns_base_search_ndots_set(current_base, ndots); 3110 } 3111 3112 static void 3113 search_set_from_hostname(struct evdns_base *base) { 3114 char hostname[HOST_NAME_MAX + 1], *domainname; 3115 3116 ASSERT_LOCKED(base); 3117 search_postfix_clear(base); 3118 if (gethostname(hostname, sizeof(hostname))) return; 3119 domainname = strchr(hostname, '.'); 3120 if (!domainname) return; 3121 search_postfix_add(base, domainname); 3122 } 3123 3124 /* warning: returns malloced string */ 3125 static char * 3126 search_make_new(const struct search_state *const state, int n, const char *const base_name) { 3127 const size_t base_len = strlen(base_name); 3128 const char need_to_append_dot = base_name[base_len - 1] == '.' ? 0 : 1; 3129 struct search_domain *dom; 3130 3131 for (dom = state->head; dom; dom = dom->next) { 3132 if (!n--) { 3133 /* this is the postfix we want */ 3134 /* the actual postfix string is kept at the end of the structure */ 3135 const u8 *const postfix = ((u8 *) dom) + sizeof(struct search_domain); 3136 const int postfix_len = dom->len; 3137 char *const newname = (char *) mm_malloc(base_len + need_to_append_dot + postfix_len + 1); 3138 if (!newname) return NULL; 3139 memcpy(newname, base_name, base_len); 3140 if (need_to_append_dot) newname[base_len] = '.'; 3141 memcpy(newname + base_len + need_to_append_dot, postfix, postfix_len); 3142 newname[base_len + need_to_append_dot + postfix_len] = 0; 3143 return newname; 3144 } 3145 } 3146 3147 /* we ran off the end of the list and still didn't find the requested string */ 3148 EVUTIL_ASSERT(0); 3149 return NULL; /* unreachable; stops warnings in some compilers. */ 3150 } 3151 3152 static struct request * 3153 search_request_new(struct evdns_base *base, struct evdns_request *handle, 3154 int type, const char *const name, int flags, 3155 evdns_callback_type user_callback, void *user_arg) { 3156 ASSERT_LOCKED(base); 3157 EVUTIL_ASSERT(type == TYPE_A || type == TYPE_AAAA); 3158 EVUTIL_ASSERT(handle->current_req == NULL); 3159 if ( ((flags & DNS_QUERY_NO_SEARCH) == 0) && 3160 base->global_search_state && 3161 base->global_search_state->num_domains) { 3162 /* we have some domains to search */ 3163 struct request *req; 3164 if (string_num_dots(name) >= base->global_search_state->ndots) { 3165 req = request_new(base, handle, type, name, flags, user_callback, user_arg); 3166 if (!req) return NULL; 3167 handle->search_index = -1; 3168 } else { 3169 char *const new_name = search_make_new(base->global_search_state, 0, name); 3170 if (!new_name) return NULL; 3171 req = request_new(base, handle, type, new_name, flags, user_callback, user_arg); 3172 mm_free(new_name); 3173 if (!req) return NULL; 3174 handle->search_index = 0; 3175 } 3176 EVUTIL_ASSERT(handle->search_origname == NULL); 3177 handle->search_origname = mm_strdup(name); 3178 if (handle->search_origname == NULL) { 3179 /* XXX Should we dealloc req? If yes, how? */ 3180 if (req) 3181 mm_free(req); 3182 return NULL; 3183 } 3184 handle->search_state = base->global_search_state; 3185 handle->search_flags = flags; 3186 base->global_search_state->refcount++; 3187 request_submit(req); 3188 return req; 3189 } else { 3190 struct request *const req = request_new(base, handle, type, name, flags, user_callback, user_arg); 3191 if (!req) return NULL; 3192 request_submit(req); 3193 return req; 3194 } 3195 } 3196 3197 /* this is called when a request has failed to find a name. We need to check */ 3198 /* if it is part of a search and, if so, try the next name in the list */ 3199 /* returns: */ 3200 /* 0 another request has been submitted */ 3201 /* 1 no more requests needed */ 3202 static int 3203 search_try_next(struct evdns_request *const handle) { 3204 struct request *req = handle->current_req; 3205 struct evdns_base *base = req->base; 3206 struct request *newreq; 3207 ASSERT_LOCKED(base); 3208 if (handle->search_state) { 3209 /* it is part of a search */ 3210 char *new_name; 3211 handle->search_index++; 3212 if (handle->search_index >= handle->search_state->num_domains) { 3213 /* no more postfixes to try, however we may need to try */ 3214 /* this name without a postfix */ 3215 if (string_num_dots(handle->search_origname) < handle->search_state->ndots) { 3216 /* yep, we need to try it raw */ 3217 newreq = request_new(base, NULL, req->request_type, handle->search_origname, handle->search_flags, req->user_callback, req->user_pointer); 3218 log(EVDNS_LOG_DEBUG, "Search: trying raw query %s", handle->search_origname); 3219 if (newreq) { 3220 search_request_finished(handle); 3221 goto submit_next; 3222 } 3223 } 3224 return 1; 3225 } 3226 3227 new_name = search_make_new(handle->search_state, handle->search_index, handle->search_origname); 3228 if (!new_name) return 1; 3229 log(EVDNS_LOG_DEBUG, "Search: now trying %s (%d)", new_name, handle->search_index); 3230 newreq = request_new(base, NULL, req->request_type, new_name, handle->search_flags, req->user_callback, req->user_pointer); 3231 mm_free(new_name); 3232 if (!newreq) return 1; 3233 goto submit_next; 3234 } 3235 return 1; 3236 3237 submit_next: 3238 request_finished(req, &REQ_HEAD(req->base, req->trans_id), 0); 3239 handle->current_req = newreq; 3240 newreq->handle = handle; 3241 request_submit(newreq); 3242 return 0; 3243 } 3244 3245 static void 3246 search_request_finished(struct evdns_request *const handle) { 3247 ASSERT_LOCKED(handle->current_req->base); 3248 if (handle->search_state) { 3249 search_state_decref(handle->search_state); 3250 handle->search_state = NULL; 3251 } 3252 if (handle->search_origname) { 3253 mm_free(handle->search_origname); 3254 handle->search_origname = NULL; 3255 } 3256 } 3257 3258 /* ================================================================= */ 3259 /* Parsing resolv.conf files */ 3260 3261 static void 3262 evdns_resolv_set_defaults(struct evdns_base *base, int flags) { 3263 /* if the file isn't found then we assume a local resolver */ 3264 ASSERT_LOCKED(base); 3265 if (flags & DNS_OPTION_SEARCH) search_set_from_hostname(base); 3266 if (flags & DNS_OPTION_NAMESERVERS) evdns_base_nameserver_ip_add(base,"127.0.0.1"); 3267 } 3268 3269 #ifndef _EVENT_HAVE_STRTOK_R 3270 static char * 3271 strtok_r(char *s, const char *delim, char **state) { 3272 char *cp, *start; 3273 start = cp = s ? s : *state; 3274 if (!cp) 3275 return NULL; 3276 while (*cp && !strchr(delim, *cp)) 3277 ++cp; 3278 if (!*cp) { 3279 if (cp == start) 3280 return NULL; 3281 *state = NULL; 3282 return start; 3283 } else { 3284 *cp++ = '\0'; 3285 *state = cp; 3286 return start; 3287 } 3288 } 3289 #endif 3290 3291 /* helper version of atoi which returns -1 on error */ 3292 static int 3293 strtoint(const char *const str) 3294 { 3295 char *endptr; 3296 const int r = strtol(str, &endptr, 10); 3297 if (*endptr) return -1; 3298 return r; 3299 } 3300 3301 /* Parse a number of seconds into a timeval; return -1 on error. */ 3302 static int 3303 strtotimeval(const char *const str, struct timeval *out) 3304 { 3305 double d; 3306 char *endptr; 3307 d = strtod(str, &endptr); 3308 if (*endptr) return -1; 3309 if (d < 0) return -1; 3310 out->tv_sec = (int) d; 3311 out->tv_usec = (int) ((d - (int) d)*1000000); 3312 if (out->tv_sec == 0 && out->tv_usec < 1000) /* less than 1 msec */ 3313 return -1; 3314 return 0; 3315 } 3316 3317 /* helper version of atoi that returns -1 on error and clips to bounds. */ 3318 static int 3319 strtoint_clipped(const char *const str, int min, int max) 3320 { 3321 int r = strtoint(str); 3322 if (r == -1) 3323 return r; 3324 else if (r<min) 3325 return min; 3326 else if (r>max) 3327 return max; 3328 else 3329 return r; 3330 } 3331 3332 static int 3333 evdns_base_set_max_requests_inflight(struct evdns_base *base, int maxinflight) 3334 { 3335 int old_n_heads = base->n_req_heads, n_heads; 3336 struct request **old_heads = base->req_heads, **new_heads, *req; 3337 int i; 3338 3339 ASSERT_LOCKED(base); 3340 if (maxinflight < 1) 3341 maxinflight = 1; 3342 n_heads = (maxinflight+4) / 5; 3343 EVUTIL_ASSERT(n_heads > 0); 3344 new_heads = mm_calloc(n_heads, sizeof(struct request*)); 3345 if (!new_heads) 3346 return (-1); 3347 if (old_heads) { 3348 for (i = 0; i < old_n_heads; ++i) { 3349 while (old_heads[i]) { 3350 req = old_heads[i]; 3351 evdns_request_remove(req, &old_heads[i]); 3352 evdns_request_insert(req, &new_heads[req->trans_id % n_heads]); 3353 } 3354 } 3355 mm_free(old_heads); 3356 } 3357 base->req_heads = new_heads; 3358 base->n_req_heads = n_heads; 3359 base->global_max_requests_inflight = maxinflight; 3360 return (0); 3361 } 3362 3363 /* exported function */ 3364 int 3365 evdns_base_set_option(struct evdns_base *base, 3366 const char *option, const char *val) 3367 { 3368 int res; 3369 EVDNS_LOCK(base); 3370 res = evdns_base_set_option_impl(base, option, val, DNS_OPTIONS_ALL); 3371 EVDNS_UNLOCK(base); 3372 return res; 3373 } 3374 3375 static inline int 3376 str_matches_option(const char *s1, const char *optionname) 3377 { 3378 /* Option names are given as "option:" We accept either 'option' in 3379 * s1, or 'option:randomjunk'. The latter form is to implement the 3380 * resolv.conf parser. */ 3381 size_t optlen = strlen(optionname); 3382 size_t slen = strlen(s1); 3383 if (slen == optlen || slen == optlen - 1) 3384 return !strncmp(s1, optionname, slen); 3385 else if (slen > optlen) 3386 return !strncmp(s1, optionname, optlen); 3387 else 3388 return 0; 3389 } 3390 3391 static int 3392 evdns_base_set_option_impl(struct evdns_base *base, 3393 const char *option, const char *val, int flags) 3394 { 3395 ASSERT_LOCKED(base); 3396 if (str_matches_option(option, "ndots:")) { 3397 const int ndots = strtoint(val); 3398 if (ndots == -1) return -1; 3399 if (!(flags & DNS_OPTION_SEARCH)) return 0; 3400 log(EVDNS_LOG_DEBUG, "Setting ndots to %d", ndots); 3401 if (!base->global_search_state) base->global_search_state = search_state_new(); 3402 if (!base->global_search_state) return -1; 3403 base->global_search_state->ndots = ndots; 3404 } else if (str_matches_option(option, "timeout:")) { 3405 struct timeval tv; 3406 if (strtotimeval(val, &tv) == -1) return -1; 3407 if (!(flags & DNS_OPTION_MISC)) return 0; 3408 log(EVDNS_LOG_DEBUG, "Setting timeout to %s", val); 3409 memcpy(&base->global_timeout, &tv, sizeof(struct timeval)); 3410 } else if (str_matches_option(option, "getaddrinfo-allow-skew:")) { 3411 struct timeval tv; 3412 if (strtotimeval(val, &tv) == -1) return -1; 3413 if (!(flags & DNS_OPTION_MISC)) return 0; 3414 log(EVDNS_LOG_DEBUG, "Setting getaddrinfo-allow-skew to %s", 3415 val); 3416 memcpy(&base->global_getaddrinfo_allow_skew, &tv, 3417 sizeof(struct timeval)); 3418 } else if (str_matches_option(option, "max-timeouts:")) { 3419 const int maxtimeout = strtoint_clipped(val, 1, 255); 3420 if (maxtimeout == -1) return -1; 3421 if (!(flags & DNS_OPTION_MISC)) return 0; 3422 log(EVDNS_LOG_DEBUG, "Setting maximum allowed timeouts to %d", 3423 maxtimeout); 3424 base->global_max_nameserver_timeout = maxtimeout; 3425 } else if (str_matches_option(option, "max-inflight:")) { 3426 const int maxinflight = strtoint_clipped(val, 1, 65000); 3427 if (maxinflight == -1) return -1; 3428 if (!(flags & DNS_OPTION_MISC)) return 0; 3429 log(EVDNS_LOG_DEBUG, "Setting maximum inflight requests to %d", 3430 maxinflight); 3431 evdns_base_set_max_requests_inflight(base, maxinflight); 3432 } else if (str_matches_option(option, "attempts:")) { 3433 int retries = strtoint(val); 3434 if (retries == -1) return -1; 3435 if (retries > 255) retries = 255; 3436 if (!(flags & DNS_OPTION_MISC)) return 0; 3437 log(EVDNS_LOG_DEBUG, "Setting retries to %d", retries); 3438 base->global_max_retransmits = retries; 3439 } else if (str_matches_option(option, "randomize-case:")) { 3440 int randcase = strtoint(val); 3441 if (!(flags & DNS_OPTION_MISC)) return 0; 3442 base->global_randomize_case = randcase; 3443 } else if (str_matches_option(option, "bind-to:")) { 3444 /* XXX This only applies to successive nameservers, not 3445 * to already-configured ones. We might want to fix that. */ 3446 int len = sizeof(base->global_outgoing_address); 3447 if (!(flags & DNS_OPTION_NAMESERVERS)) return 0; 3448 if (evutil_parse_sockaddr_port(val, 3449 (struct sockaddr*)&base->global_outgoing_address, &len)) 3450 return -1; 3451 base->global_outgoing_addrlen = len; 3452 } else if (str_matches_option(option, "initial-probe-timeout:")) { 3453 struct timeval tv; 3454 if (strtotimeval(val, &tv) == -1) return -1; 3455 if (tv.tv_sec > 3600) 3456 tv.tv_sec = 3600; 3457 if (!(flags & DNS_OPTION_MISC)) return 0; 3458 log(EVDNS_LOG_DEBUG, "Setting initial probe timeout to %s", 3459 val); 3460 memcpy(&base->global_nameserver_probe_initial_timeout, &tv, 3461 sizeof(tv)); 3462 } 3463 return 0; 3464 } 3465 3466 int 3467 evdns_set_option(const char *option, const char *val, int flags) 3468 { 3469 if (!current_base) 3470 current_base = evdns_base_new(NULL, 0); 3471 return evdns_base_set_option(current_base, option, val); 3472 } 3473 3474 static void 3475 resolv_conf_parse_line(struct evdns_base *base, char *const start, int flags) { 3476 char *strtok_state; 3477 static const char *const delims = " \t"; 3478 #define NEXT_TOKEN strtok_r(NULL, delims, &strtok_state) 3479 3480 3481 char *const first_token = strtok_r(start, delims, &strtok_state); 3482 ASSERT_LOCKED(base); 3483 if (!first_token) return; 3484 3485 if (!strcmp(first_token, "nameserver") && (flags & DNS_OPTION_NAMESERVERS)) { 3486 const char *const nameserver = NEXT_TOKEN; 3487 3488 if (nameserver) 3489 evdns_base_nameserver_ip_add(base, nameserver); 3490 } else if (!strcmp(first_token, "domain") && (flags & DNS_OPTION_SEARCH)) { 3491 const char *const domain = NEXT_TOKEN; 3492 if (domain) { 3493 search_postfix_clear(base); 3494 search_postfix_add(base, domain); 3495 } 3496 } else if (!strcmp(first_token, "search") && (flags & DNS_OPTION_SEARCH)) { 3497 const char *domain; 3498 search_postfix_clear(base); 3499 3500 while ((domain = NEXT_TOKEN)) { 3501 search_postfix_add(base, domain); 3502 } 3503 search_reverse(base); 3504 } else if (!strcmp(first_token, "options")) { 3505 const char *option; 3506 while ((option = NEXT_TOKEN)) { 3507 const char *val = strchr(option, ':'); 3508 evdns_base_set_option_impl(base, option, val ? val+1 : "", flags); 3509 } 3510 } 3511 #undef NEXT_TOKEN 3512 } 3513 3514 /* exported function */ 3515 /* returns: */ 3516 /* 0 no errors */ 3517 /* 1 failed to open file */ 3518 /* 2 failed to stat file */ 3519 /* 3 file too large */ 3520 /* 4 out of memory */ 3521 /* 5 short read from file */ 3522 int 3523 evdns_base_resolv_conf_parse(struct evdns_base *base, int flags, const char *const filename) { 3524 int res; 3525 EVDNS_LOCK(base); 3526 res = evdns_base_resolv_conf_parse_impl(base, flags, filename); 3527 EVDNS_UNLOCK(base); 3528 return res; 3529 } 3530 3531 static char * 3532 evdns_get_default_hosts_filename(void) 3533 { 3534 #ifdef WIN32 3535 /* Windows is a little coy about where it puts its configuration 3536 * files. Sure, they're _usually_ in C:\windows\system32, but 3537 * there's no reason in principle they couldn't be in 3538 * W:\hoboken chicken emergency\ 3539 */ 3540 char path[MAX_PATH+1]; 3541 static const char hostfile[] = "\\drivers\\etc\\hosts"; 3542 char *path_out; 3543 size_t len_out; 3544 3545 if (! SHGetSpecialFolderPathA(NULL, path, CSIDL_SYSTEM, 0)) 3546 return NULL; 3547 len_out = strlen(path)+strlen(hostfile); 3548 path_out = mm_malloc(len_out+1); 3549 evutil_snprintf(path_out, len_out, "%s%s", path, hostfile); 3550 return path_out; 3551 #else 3552 return mm_strdup("/etc/hosts"); 3553 #endif 3554 } 3555 3556 static int 3557 evdns_base_resolv_conf_parse_impl(struct evdns_base *base, int flags, const char *const filename) { 3558 size_t n; 3559 char *resolv; 3560 char *start; 3561 int err = 0; 3562 3563 log(EVDNS_LOG_DEBUG, "Parsing resolv.conf file %s", filename); 3564 3565 if (flags & DNS_OPTION_HOSTSFILE) { 3566 char *fname = evdns_get_default_hosts_filename(); 3567 evdns_base_load_hosts(base, fname); 3568 if (fname) 3569 mm_free(fname); 3570 } 3571 3572 if ((err = evutil_read_file(filename, &resolv, &n, 0)) < 0) { 3573 if (err == -1) { 3574 /* No file. */ 3575 evdns_resolv_set_defaults(base, flags); 3576 return 1; 3577 } else { 3578 return 2; 3579 } 3580 } 3581 3582 start = resolv; 3583 for (;;) { 3584 char *const newline = strchr(start, '\n'); 3585 if (!newline) { 3586 resolv_conf_parse_line(base, start, flags); 3587 break; 3588 } else { 3589 *newline = 0; 3590 resolv_conf_parse_line(base, start, flags); 3591 start = newline + 1; 3592 } 3593 } 3594 3595 if (!base->server_head && (flags & DNS_OPTION_NAMESERVERS)) { 3596 /* no nameservers were configured. */ 3597 evdns_base_nameserver_ip_add(base, "127.0.0.1"); 3598 err = 6; 3599 } 3600 if (flags & DNS_OPTION_SEARCH && (!base->global_search_state || base->global_search_state->num_domains == 0)) { 3601 search_set_from_hostname(base); 3602 } 3603 3604 mm_free(resolv); 3605 return err; 3606 } 3607 3608 int 3609 evdns_resolv_conf_parse(int flags, const char *const filename) { 3610 if (!current_base) 3611 current_base = evdns_base_new(NULL, 0); 3612 return evdns_base_resolv_conf_parse(current_base, flags, filename); 3613 } 3614 3615 3616 #ifdef WIN32 3617 /* Add multiple nameservers from a space-or-comma-separated list. */ 3618 static int 3619 evdns_nameserver_ip_add_line(struct evdns_base *base, const char *ips) { 3620 const char *addr; 3621 char *buf; 3622 int r; 3623 ASSERT_LOCKED(base); 3624 while (*ips) { 3625 while (isspace(*ips) || *ips == ',' || *ips == '\t') 3626 ++ips; 3627 addr = ips; 3628 while (isdigit(*ips) || *ips == '.' || *ips == ':' || 3629 *ips=='[' || *ips==']') 3630 ++ips; 3631 buf = mm_malloc(ips-addr+1); 3632 if (!buf) return 4; 3633 memcpy(buf, addr, ips-addr); 3634 buf[ips-addr] = '\0'; 3635 r = evdns_base_nameserver_ip_add(base, buf); 3636 mm_free(buf); 3637 if (r) return r; 3638 } 3639 return 0; 3640 } 3641 3642 typedef DWORD(WINAPI *GetNetworkParams_fn_t)(FIXED_INFO *, DWORD*); 3643 3644 /* Use the windows GetNetworkParams interface in iphlpapi.dll to */ 3645 /* figure out what our nameservers are. */ 3646 static int 3647 load_nameservers_with_getnetworkparams(struct evdns_base *base) 3648 { 3649 /* Based on MSDN examples and inspection of c-ares code. */ 3650 FIXED_INFO *fixed; 3651 HMODULE handle = 0; 3652 ULONG size = sizeof(FIXED_INFO); 3653 void *buf = NULL; 3654 int status = 0, r, added_any; 3655 IP_ADDR_STRING *ns; 3656 GetNetworkParams_fn_t fn; 3657 3658 ASSERT_LOCKED(base); 3659 if (!(handle = evutil_load_windows_system_library( 3660 TEXT("iphlpapi.dll")))) { 3661 log(EVDNS_LOG_WARN, "Could not open iphlpapi.dll"); 3662 status = -1; 3663 goto done; 3664 } 3665 if (!(fn = (GetNetworkParams_fn_t) GetProcAddress(handle, "GetNetworkParams"))) { 3666 log(EVDNS_LOG_WARN, "Could not get address of function."); 3667 status = -1; 3668 goto done; 3669 } 3670 3671 buf = mm_malloc(size); 3672 if (!buf) { status = 4; goto done; } 3673 fixed = buf; 3674 r = fn(fixed, &size); 3675 if (r != ERROR_SUCCESS && r != ERROR_BUFFER_OVERFLOW) { 3676 status = -1; 3677 goto done; 3678 } 3679 if (r != ERROR_SUCCESS) { 3680 mm_free(buf); 3681 buf = mm_malloc(size); 3682 if (!buf) { status = 4; goto done; } 3683 fixed = buf; 3684 r = fn(fixed, &size); 3685 if (r != ERROR_SUCCESS) { 3686 log(EVDNS_LOG_DEBUG, "fn() failed."); 3687 status = -1; 3688 goto done; 3689 } 3690 } 3691 3692 EVUTIL_ASSERT(fixed); 3693 added_any = 0; 3694 ns = &(fixed->DnsServerList); 3695 while (ns) { 3696 r = evdns_nameserver_ip_add_line(base, ns->IpAddress.String); 3697 if (r) { 3698 log(EVDNS_LOG_DEBUG,"Could not add nameserver %s to list,error: %d", 3699 (ns->IpAddress.String),(int)GetLastError()); 3700 status = r; 3701 } else { 3702 ++added_any; 3703 log(EVDNS_LOG_DEBUG,"Successfully added %s as nameserver",ns->IpAddress.String); 3704 } 3705 3706 ns = ns->Next; 3707 } 3708 3709 if (!added_any) { 3710 log(EVDNS_LOG_DEBUG, "No nameservers added."); 3711 if (status == 0) 3712 status = -1; 3713 } else { 3714 status = 0; 3715 } 3716 3717 done: 3718 if (buf) 3719 mm_free(buf); 3720 if (handle) 3721 FreeLibrary(handle); 3722 return status; 3723 } 3724 3725 static int 3726 config_nameserver_from_reg_key(struct evdns_base *base, HKEY key, const TCHAR *subkey) 3727 { 3728 char *buf; 3729 DWORD bufsz = 0, type = 0; 3730 int status = 0; 3731 3732 ASSERT_LOCKED(base); 3733 if (RegQueryValueEx(key, subkey, 0, &type, NULL, &bufsz) 3734 != ERROR_MORE_DATA) 3735 return -1; 3736 if (!(buf = mm_malloc(bufsz))) 3737 return -1; 3738 3739 if (RegQueryValueEx(key, subkey, 0, &type, (LPBYTE)buf, &bufsz) 3740 == ERROR_SUCCESS && bufsz > 1) { 3741 status = evdns_nameserver_ip_add_line(base,buf); 3742 } 3743 3744 mm_free(buf); 3745 return status; 3746 } 3747 3748 #define SERVICES_KEY TEXT("System\\CurrentControlSet\\Services\\") 3749 #define WIN_NS_9X_KEY SERVICES_KEY TEXT("VxD\\MSTCP") 3750 #define WIN_NS_NT_KEY SERVICES_KEY TEXT("Tcpip\\Parameters") 3751 3752 static int 3753 load_nameservers_from_registry(struct evdns_base *base) 3754 { 3755 int found = 0; 3756 int r; 3757 #define TRY(k, name) \ 3758 if (!found && config_nameserver_from_reg_key(base,k,TEXT(name)) == 0) { \ 3759 log(EVDNS_LOG_DEBUG,"Found nameservers in %s/%s",#k,name); \ 3760 found = 1; \ 3761 } else if (!found) { \ 3762 log(EVDNS_LOG_DEBUG,"Didn't find nameservers in %s/%s", \ 3763 #k,#name); \ 3764 } 3765 3766 ASSERT_LOCKED(base); 3767 3768 if (((int)GetVersion()) > 0) { /* NT */ 3769 HKEY nt_key = 0, interfaces_key = 0; 3770 3771 if (RegOpenKeyEx(HKEY_LOCAL_MACHINE, WIN_NS_NT_KEY, 0, 3772 KEY_READ, &nt_key) != ERROR_SUCCESS) { 3773 log(EVDNS_LOG_DEBUG,"Couldn't open nt key, %d",(int)GetLastError()); 3774 return -1; 3775 } 3776 r = RegOpenKeyEx(nt_key, TEXT("Interfaces"), 0, 3777 KEY_QUERY_VALUE|KEY_ENUMERATE_SUB_KEYS, 3778 &interfaces_key); 3779 if (r != ERROR_SUCCESS) { 3780 log(EVDNS_LOG_DEBUG,"Couldn't open interfaces key, %d",(int)GetLastError()); 3781 return -1; 3782 } 3783 TRY(nt_key, "NameServer"); 3784 TRY(nt_key, "DhcpNameServer"); 3785 TRY(interfaces_key, "NameServer"); 3786 TRY(interfaces_key, "DhcpNameServer"); 3787 RegCloseKey(interfaces_key); 3788 RegCloseKey(nt_key); 3789 } else { 3790 HKEY win_key = 0; 3791 if (RegOpenKeyEx(HKEY_LOCAL_MACHINE, WIN_NS_9X_KEY, 0, 3792 KEY_READ, &win_key) != ERROR_SUCCESS) { 3793 log(EVDNS_LOG_DEBUG, "Couldn't open registry key, %d", (int)GetLastError()); 3794 return -1; 3795 } 3796 TRY(win_key, "NameServer"); 3797 RegCloseKey(win_key); 3798 } 3799 3800 if (found == 0) { 3801 log(EVDNS_LOG_WARN,"Didn't find any nameservers."); 3802 } 3803 3804 return found ? 0 : -1; 3805 #undef TRY 3806 } 3807 3808 int 3809 evdns_base_config_windows_nameservers(struct evdns_base *base) 3810 { 3811 int r; 3812 char *fname; 3813 if (base == NULL) 3814 base = current_base; 3815 if (base == NULL) 3816 return -1; 3817 EVDNS_LOCK(base); 3818 if (load_nameservers_with_getnetworkparams(base) == 0) { 3819 EVDNS_UNLOCK(base); 3820 return 0; 3821 } 3822 r = load_nameservers_from_registry(base); 3823 3824 fname = evdns_get_default_hosts_filename(); 3825 evdns_base_load_hosts(base, fname); 3826 if (fname) 3827 mm_free(fname); 3828 3829 EVDNS_UNLOCK(base); 3830 return r; 3831 } 3832 3833 int 3834 evdns_config_windows_nameservers(void) 3835 { 3836 if (!current_base) { 3837 current_base = evdns_base_new(NULL, 1); 3838 return current_base == NULL ? -1 : 0; 3839 } else { 3840 return evdns_base_config_windows_nameservers(current_base); 3841 } 3842 } 3843 #endif 3844 3845 struct evdns_base * 3846 evdns_base_new(struct event_base *event_base, int initialize_nameservers) 3847 { 3848 struct evdns_base *base; 3849 3850 if (evutil_secure_rng_init() < 0) { 3851 log(EVDNS_LOG_WARN, "Unable to seed random number generator; " 3852 "DNS can't run."); 3853 return NULL; 3854 } 3855 3856 /* Give the evutil library a hook into its evdns-enabled 3857 * functionality. We can't just call evdns_getaddrinfo directly or 3858 * else libevent-core will depend on libevent-extras. */ 3859 evutil_set_evdns_getaddrinfo_fn(evdns_getaddrinfo); 3860 3861 base = mm_malloc(sizeof(struct evdns_base)); 3862 if (base == NULL) 3863 return (NULL); 3864 memset(base, 0, sizeof(struct evdns_base)); 3865 base->req_waiting_head = NULL; 3866 3867 EVTHREAD_ALLOC_LOCK(base->lock, EVTHREAD_LOCKTYPE_RECURSIVE); 3868 EVDNS_LOCK(base); 3869 3870 /* Set max requests inflight and allocate req_heads. */ 3871 base->req_heads = NULL; 3872 3873 evdns_base_set_max_requests_inflight(base, 64); 3874 3875 base->server_head = NULL; 3876 base->event_base = event_base; 3877 base->global_good_nameservers = base->global_requests_inflight = 3878 base->global_requests_waiting = 0; 3879 3880 base->global_timeout.tv_sec = 5; 3881 base->global_timeout.tv_usec = 0; 3882 base->global_max_reissues = 1; 3883 base->global_max_retransmits = 3; 3884 base->global_max_nameserver_timeout = 3; 3885 base->global_search_state = NULL; 3886 base->global_randomize_case = 1; 3887 base->global_getaddrinfo_allow_skew.tv_sec = 3; 3888 base->global_getaddrinfo_allow_skew.tv_usec = 0; 3889 base->global_nameserver_probe_initial_timeout.tv_sec = 10; 3890 base->global_nameserver_probe_initial_timeout.tv_usec = 0; 3891 3892 TAILQ_INIT(&base->hostsdb); 3893 3894 if (initialize_nameservers) { 3895 int r; 3896 #ifdef WIN32 3897 r = evdns_base_config_windows_nameservers(base); 3898 #else 3899 r = evdns_base_resolv_conf_parse(base, DNS_OPTIONS_ALL, "/etc/resolv.conf"); 3900 #endif 3901 if (r == -1) { 3902 evdns_base_free_and_unlock(base, 0); 3903 return NULL; 3904 } 3905 } 3906 EVDNS_UNLOCK(base); 3907 return base; 3908 } 3909 3910 int 3911 evdns_init(void) 3912 { 3913 struct evdns_base *base = evdns_base_new(NULL, 1); 3914 if (base) { 3915 current_base = base; 3916 return 0; 3917 } else { 3918 return -1; 3919 } 3920 } 3921 3922 const char * 3923 evdns_err_to_string(int err) 3924 { 3925 switch (err) { 3926 case DNS_ERR_NONE: return "no error"; 3927 case DNS_ERR_FORMAT: return "misformatted query"; 3928 case DNS_ERR_SERVERFAILED: return "server failed"; 3929 case DNS_ERR_NOTEXIST: return "name does not exist"; 3930 case DNS_ERR_NOTIMPL: return "query not implemented"; 3931 case DNS_ERR_REFUSED: return "refused"; 3932 3933 case DNS_ERR_TRUNCATED: return "reply truncated or ill-formed"; 3934 case DNS_ERR_UNKNOWN: return "unknown"; 3935 case DNS_ERR_TIMEOUT: return "request timed out"; 3936 case DNS_ERR_SHUTDOWN: return "dns subsystem shut down"; 3937 case DNS_ERR_CANCEL: return "dns request canceled"; 3938 case DNS_ERR_NODATA: return "no records in the reply"; 3939 default: return "[Unknown error code]"; 3940 } 3941 } 3942 3943 static void 3944 evdns_nameserver_free(struct nameserver *server) 3945 { 3946 if (server->socket >= 0) 3947 evutil_closesocket(server->socket); 3948 (void) event_del(&server->event); 3949 event_debug_unassign(&server->event); 3950 if (server->state == 0) 3951 (void) event_del(&server->timeout_event); 3952 if (server->probe_request) { 3953 evdns_cancel_request(server->base, server->probe_request); 3954 server->probe_request = NULL; 3955 } 3956 event_debug_unassign(&server->timeout_event); 3957 mm_free(server); 3958 } 3959 3960 static void 3961 evdns_base_free_and_unlock(struct evdns_base *base, int fail_requests) 3962 { 3963 struct nameserver *server, *server_next; 3964 struct search_domain *dom, *dom_next; 3965 int i; 3966 3967 /* Requires that we hold the lock. */ 3968 3969 /* TODO(nickm) we might need to refcount here. */ 3970 3971 for (server = base->server_head; server; server = server_next) { 3972 server_next = server->next; 3973 evdns_nameserver_free(server); 3974 if (server_next == base->server_head) 3975 break; 3976 } 3977 base->server_head = NULL; 3978 base->global_good_nameservers = 0; 3979 3980 for (i = 0; i < base->n_req_heads; ++i) { 3981 while (base->req_heads[i]) { 3982 if (fail_requests) 3983 reply_schedule_callback(base->req_heads[i], 0, DNS_ERR_SHUTDOWN, NULL); 3984 request_finished(base->req_heads[i], &REQ_HEAD(base, base->req_heads[i]->trans_id), 1); 3985 } 3986 } 3987 while (base->req_waiting_head) { 3988 if (fail_requests) 3989 reply_schedule_callback(base->req_waiting_head, 0, DNS_ERR_SHUTDOWN, NULL); 3990 request_finished(base->req_waiting_head, &base->req_waiting_head, 1); 3991 } 3992 base->global_requests_inflight = base->global_requests_waiting = 0; 3993 3994 3995 if (base->global_search_state) { 3996 for (dom = base->global_search_state->head; dom; dom = dom_next) { 3997 dom_next = dom->next; 3998 mm_free(dom); 3999 } 4000 mm_free(base->global_search_state); 4001 base->global_search_state = NULL; 4002 } 4003 4004 { 4005 struct hosts_entry *victim; 4006 while ((victim = TAILQ_FIRST(&base->hostsdb))) { 4007 TAILQ_REMOVE(&base->hostsdb, victim, next); 4008 mm_free(victim); 4009 } 4010 } 4011 4012 mm_free(base->req_heads); 4013 4014 EVDNS_UNLOCK(base); 4015 EVTHREAD_FREE_LOCK(base->lock, EVTHREAD_LOCKTYPE_RECURSIVE); 4016 4017 mm_free(base); 4018 } 4019 4020 void 4021 evdns_base_free(struct evdns_base *base, int fail_requests) 4022 { 4023 EVDNS_LOCK(base); 4024 evdns_base_free_and_unlock(base, fail_requests); 4025 } 4026 4027 void 4028 evdns_shutdown(int fail_requests) 4029 { 4030 if (current_base) { 4031 struct evdns_base *b = current_base; 4032 current_base = NULL; 4033 evdns_base_free(b, fail_requests); 4034 } 4035 evdns_log_fn = NULL; 4036 } 4037 4038 static int 4039 evdns_base_parse_hosts_line(struct evdns_base *base, char *line) 4040 { 4041 char *strtok_state; 4042 static const char *const delims = " \t"; 4043 char *const addr = strtok_r(line, delims, &strtok_state); 4044 char *hostname, *hash; 4045 struct sockaddr_storage ss; 4046 int socklen = sizeof(ss); 4047 ASSERT_LOCKED(base); 4048 4049 #define NEXT_TOKEN strtok_r(NULL, delims, &strtok_state) 4050 4051 if (!addr || *addr == '#') 4052 return 0; 4053 4054 memset(&ss, 0, sizeof(ss)); 4055 if (evutil_parse_sockaddr_port(addr, (struct sockaddr*)&ss, &socklen)<0) 4056 return -1; 4057 if (socklen > (int)sizeof(struct sockaddr_in6)) 4058 return -1; 4059 4060 if (sockaddr_getport((struct sockaddr*)&ss)) 4061 return -1; 4062 4063 while ((hostname = NEXT_TOKEN)) { 4064 struct hosts_entry *he; 4065 size_t namelen; 4066 if ((hash = strchr(hostname, '#'))) { 4067 if (hash == hostname) 4068 return 0; 4069 *hash = '\0'; 4070 } 4071 4072 namelen = strlen(hostname); 4073 4074 he = mm_calloc(1, sizeof(struct hosts_entry)+namelen); 4075 if (!he) 4076 return -1; 4077 EVUTIL_ASSERT(socklen <= (int)sizeof(he->addr)); 4078 memcpy(&he->addr, &ss, socklen); 4079 memcpy(he->hostname, hostname, namelen+1); 4080 he->addrlen = socklen; 4081 4082 TAILQ_INSERT_TAIL(&base->hostsdb, he, next); 4083 4084 if (hash) 4085 return 0; 4086 } 4087 4088 return 0; 4089 #undef NEXT_TOKEN 4090 } 4091 4092 static int 4093 evdns_base_load_hosts_impl(struct evdns_base *base, const char *hosts_fname) 4094 { 4095 char *str=NULL, *cp, *eol; 4096 size_t len; 4097 int err=0; 4098 4099 ASSERT_LOCKED(base); 4100 4101 if (hosts_fname == NULL || 4102 (err = evutil_read_file(hosts_fname, &str, &len, 0)) < 0) { 4103 char tmp[64]; 4104 strlcpy(tmp, "127.0.0.1 localhost", sizeof(tmp)); 4105 evdns_base_parse_hosts_line(base, tmp); 4106 strlcpy(tmp, "::1 localhost", sizeof(tmp)); 4107 evdns_base_parse_hosts_line(base, tmp); 4108 return err ? -1 : 0; 4109 } 4110 4111 /* This will break early if there is a NUL in the hosts file. 4112 * Probably not a problem.*/ 4113 cp = str; 4114 for (;;) { 4115 eol = strchr(cp, '\n'); 4116 4117 if (eol) { 4118 *eol = '\0'; 4119 evdns_base_parse_hosts_line(base, cp); 4120 cp = eol+1; 4121 } else { 4122 evdns_base_parse_hosts_line(base, cp); 4123 break; 4124 } 4125 } 4126 4127 mm_free(str); 4128 return 0; 4129 } 4130 4131 int 4132 evdns_base_load_hosts(struct evdns_base *base, const char *hosts_fname) 4133 { 4134 int res; 4135 if (!base) 4136 base = current_base; 4137 EVDNS_LOCK(base); 4138 res = evdns_base_load_hosts_impl(base, hosts_fname); 4139 EVDNS_UNLOCK(base); 4140 return res; 4141 } 4142 4143 /* A single request for a getaddrinfo, either v4 or v6. */ 4144 struct getaddrinfo_subrequest { 4145 struct evdns_request *r; 4146 ev_uint32_t type; 4147 }; 4148 4149 /* State data used to implement an in-progress getaddrinfo. */ 4150 struct evdns_getaddrinfo_request { 4151 struct evdns_base *evdns_base; 4152 /* Copy of the modified 'hints' data that we'll use to build 4153 * answers. */ 4154 struct evutil_addrinfo hints; 4155 /* The callback to invoke when we're done */ 4156 evdns_getaddrinfo_cb user_cb; 4157 /* User-supplied data to give to the callback. */ 4158 void *user_data; 4159 /* The port to use when building sockaddrs. */ 4160 ev_uint16_t port; 4161 /* The sub_request for an A record (if any) */ 4162 struct getaddrinfo_subrequest ipv4_request; 4163 /* The sub_request for an AAAA record (if any) */ 4164 struct getaddrinfo_subrequest ipv6_request; 4165 4166 /* The cname result that we were told (if any) */ 4167 char *cname_result; 4168 4169 /* If we have one request answered and one request still inflight, 4170 * then this field holds the answer from the first request... */ 4171 struct evutil_addrinfo *pending_result; 4172 /* And this event is a timeout that will tell us to cancel the second 4173 * request if it's taking a long time. */ 4174 struct event timeout; 4175 4176 /* And this field holds the error code from the first request... */ 4177 int pending_error; 4178 /* If this is set, the user canceled this request. */ 4179 unsigned user_canceled : 1; 4180 /* If this is set, the user can no longer cancel this request; we're 4181 * just waiting for the free. */ 4182 unsigned request_done : 1; 4183 }; 4184 4185 /* Convert an evdns errors to the equivalent getaddrinfo error. */ 4186 static int 4187 evdns_err_to_getaddrinfo_err(int e1) 4188 { 4189 /* XXX Do this better! */ 4190 if (e1 == DNS_ERR_NONE) 4191 return 0; 4192 else if (e1 == DNS_ERR_NOTEXIST) 4193 return EVUTIL_EAI_NONAME; 4194 else 4195 return EVUTIL_EAI_FAIL; 4196 } 4197 4198 /* Return the more informative of two getaddrinfo errors. */ 4199 static int 4200 getaddrinfo_merge_err(int e1, int e2) 4201 { 4202 /* XXXX be cleverer here. */ 4203 if (e1 == 0) 4204 return e2; 4205 else 4206 return e1; 4207 } 4208 4209 static void 4210 free_getaddrinfo_request(struct evdns_getaddrinfo_request *data) 4211 { 4212 /* DO NOT CALL this if either of the requests is pending. Only once 4213 * both callbacks have been invoked is it safe to free the request */ 4214 if (data->pending_result) 4215 evutil_freeaddrinfo(data->pending_result); 4216 if (data->cname_result) 4217 mm_free(data->cname_result); 4218 event_del(&data->timeout); 4219 mm_free(data); 4220 return; 4221 } 4222 4223 static void 4224 add_cname_to_reply(struct evdns_getaddrinfo_request *data, 4225 struct evutil_addrinfo *ai) 4226 { 4227 if (data->cname_result && ai) { 4228 ai->ai_canonname = data->cname_result; 4229 data->cname_result = NULL; 4230 } 4231 } 4232 4233 /* Callback: invoked when one request in a mixed-format A/AAAA getaddrinfo 4234 * request has finished, but the other one took too long to answer. Pass 4235 * along the answer we got, and cancel the other request. 4236 */ 4237 static void 4238 evdns_getaddrinfo_timeout_cb(evutil_socket_t fd, short what, void *ptr) 4239 { 4240 int v4_timedout = 0, v6_timedout = 0; 4241 struct evdns_getaddrinfo_request *data = ptr; 4242 4243 /* Cancel any pending requests, and note which one */ 4244 if (data->ipv4_request.r) { 4245 /* XXXX This does nothing if the request's callback is already 4246 * running (pending_cb is set). */ 4247 evdns_cancel_request(NULL, data->ipv4_request.r); 4248 v4_timedout = 1; 4249 EVDNS_LOCK(data->evdns_base); 4250 ++data->evdns_base->getaddrinfo_ipv4_timeouts; 4251 EVDNS_UNLOCK(data->evdns_base); 4252 } 4253 if (data->ipv6_request.r) { 4254 /* XXXX This does nothing if the request's callback is already 4255 * running (pending_cb is set). */ 4256 evdns_cancel_request(NULL, data->ipv6_request.r); 4257 v6_timedout = 1; 4258 EVDNS_LOCK(data->evdns_base); 4259 ++data->evdns_base->getaddrinfo_ipv6_timeouts; 4260 EVDNS_UNLOCK(data->evdns_base); 4261 } 4262 4263 /* We only use this timeout callback when we have an answer for 4264 * one address. */ 4265 EVUTIL_ASSERT(!v4_timedout || !v6_timedout); 4266 4267 /* Report the outcome of the other request that didn't time out. */ 4268 if (data->pending_result) { 4269 add_cname_to_reply(data, data->pending_result); 4270 data->user_cb(0, data->pending_result, data->user_data); 4271 data->pending_result = NULL; 4272 } else { 4273 int e = data->pending_error; 4274 if (!e) 4275 e = EVUTIL_EAI_AGAIN; 4276 data->user_cb(e, NULL, data->user_data); 4277 } 4278 4279 data->user_cb = NULL; /* prevent double-call if evdns callbacks are 4280 * in-progress. XXXX It would be better if this 4281 * weren't necessary. */ 4282 4283 if (!v4_timedout && !v6_timedout) { 4284 /* should be impossible? XXXX */ 4285 free_getaddrinfo_request(data); 4286 } 4287 } 4288 4289 static int 4290 evdns_getaddrinfo_set_timeout(struct evdns_base *evdns_base, 4291 struct evdns_getaddrinfo_request *data) 4292 { 4293 return event_add(&data->timeout, &evdns_base->global_getaddrinfo_allow_skew); 4294 } 4295 4296 static inline int 4297 evdns_result_is_answer(int result) 4298 { 4299 return (result != DNS_ERR_NOTIMPL && result != DNS_ERR_REFUSED && 4300 result != DNS_ERR_SERVERFAILED && result != DNS_ERR_CANCEL); 4301 } 4302 4303 static void 4304 evdns_getaddrinfo_gotresolve(int result, char type, int count, 4305 int ttl, void *addresses, void *arg) 4306 { 4307 int i; 4308 struct getaddrinfo_subrequest *req = arg; 4309 struct getaddrinfo_subrequest *other_req; 4310 struct evdns_getaddrinfo_request *data; 4311 4312 struct evutil_addrinfo *res; 4313 4314 struct sockaddr_in sin; 4315 struct sockaddr_in6 sin6; 4316 struct sockaddr *sa; 4317 int socklen, addrlen; 4318 void *addrp; 4319 int err; 4320 int user_canceled; 4321 4322 EVUTIL_ASSERT(req->type == DNS_IPv4_A || req->type == DNS_IPv6_AAAA); 4323 if (req->type == DNS_IPv4_A) { 4324 data = EVUTIL_UPCAST(req, struct evdns_getaddrinfo_request, ipv4_request); 4325 other_req = &data->ipv6_request; 4326 } else { 4327 data = EVUTIL_UPCAST(req, struct evdns_getaddrinfo_request, ipv6_request); 4328 other_req = &data->ipv4_request; 4329 } 4330 4331 EVDNS_LOCK(data->evdns_base); 4332 if (evdns_result_is_answer(result)) { 4333 if (req->type == DNS_IPv4_A) 4334 ++data->evdns_base->getaddrinfo_ipv4_answered; 4335 else 4336 ++data->evdns_base->getaddrinfo_ipv6_answered; 4337 } 4338 user_canceled = data->user_canceled; 4339 if (other_req->r == NULL) 4340 data->request_done = 1; 4341 EVDNS_UNLOCK(data->evdns_base); 4342 4343 req->r = NULL; 4344 4345 if (result == DNS_ERR_CANCEL && ! user_canceled) { 4346 /* Internal cancel request from timeout or internal error. 4347 * we already answered the user. */ 4348 if (other_req->r == NULL) 4349 free_getaddrinfo_request(data); 4350 return; 4351 } 4352 4353 if (data->user_cb == NULL) { 4354 /* We already answered. XXXX This shouldn't be needed; see 4355 * comments in evdns_getaddrinfo_timeout_cb */ 4356 free_getaddrinfo_request(data); 4357 return; 4358 } 4359 4360 if (result == DNS_ERR_NONE) { 4361 if (count == 0) 4362 err = EVUTIL_EAI_NODATA; 4363 else 4364 err = 0; 4365 } else { 4366 err = evdns_err_to_getaddrinfo_err(result); 4367 } 4368 4369 if (err) { 4370 /* Looks like we got an error. */ 4371 if (other_req->r) { 4372 /* The other request is still working; maybe it will 4373 * succeed. */ 4374 /* XXXX handle failure from set_timeout */ 4375 evdns_getaddrinfo_set_timeout(data->evdns_base, data); 4376 data->pending_error = err; 4377 return; 4378 } 4379 4380 if (user_canceled) { 4381 data->user_cb(EVUTIL_EAI_CANCEL, NULL, data->user_data); 4382 } else if (data->pending_result) { 4383 /* If we have an answer waiting, and we weren't 4384 * canceled, ignore this error. */ 4385 add_cname_to_reply(data, data->pending_result); 4386 data->user_cb(0, data->pending_result, data->user_data); 4387 data->pending_result = NULL; 4388 } else { 4389 if (data->pending_error) 4390 err = getaddrinfo_merge_err(err, 4391 data->pending_error); 4392 data->user_cb(err, NULL, data->user_data); 4393 } 4394 free_getaddrinfo_request(data); 4395 return; 4396 } else if (user_canceled) { 4397 if (other_req->r) { 4398 /* The other request is still working; let it hit this 4399 * callback with EVUTIL_EAI_CANCEL callback and report 4400 * the failure. */ 4401 return; 4402 } 4403 data->user_cb(EVUTIL_EAI_CANCEL, NULL, data->user_data); 4404 free_getaddrinfo_request(data); 4405 return; 4406 } 4407 4408 /* Looks like we got some answers. We should turn them into addrinfos 4409 * and then either queue those or return them all. */ 4410 EVUTIL_ASSERT(type == DNS_IPv4_A || type == DNS_IPv6_AAAA); 4411 4412 if (type == DNS_IPv4_A) { 4413 memset(&sin, 0, sizeof(sin)); 4414 sin.sin_family = AF_INET; 4415 sin.sin_port = htons(data->port); 4416 4417 sa = (struct sockaddr *)&sin; 4418 socklen = sizeof(sin); 4419 addrlen = 4; 4420 addrp = &sin.sin_addr.s_addr; 4421 } else { 4422 memset(&sin6, 0, sizeof(sin6)); 4423 sin6.sin6_family = AF_INET6; 4424 sin6.sin6_port = htons(data->port); 4425 4426 sa = (struct sockaddr *)&sin6; 4427 socklen = sizeof(sin6); 4428 addrlen = 16; 4429 addrp = &sin6.sin6_addr.s6_addr; 4430 } 4431 4432 res = NULL; 4433 for (i=0; i < count; ++i) { 4434 struct evutil_addrinfo *ai; 4435 memcpy(addrp, ((char*)addresses)+i*addrlen, addrlen); 4436 ai = evutil_new_addrinfo(sa, socklen, &data->hints); 4437 if (!ai) { 4438 if (other_req->r) { 4439 evdns_cancel_request(NULL, other_req->r); 4440 } 4441 data->user_cb(EVUTIL_EAI_MEMORY, NULL, data->user_data); 4442 if (res) 4443 evutil_freeaddrinfo(res); 4444 4445 if (other_req->r == NULL) 4446 free_getaddrinfo_request(data); 4447 return; 4448 } 4449 res = evutil_addrinfo_append(res, ai); 4450 } 4451 4452 if (other_req->r) { 4453 /* The other request is still in progress; wait for it */ 4454 /* XXXX handle failure from set_timeout */ 4455 evdns_getaddrinfo_set_timeout(data->evdns_base, data); 4456 data->pending_result = res; 4457 return; 4458 } else { 4459 /* The other request is done or never started; append its 4460 * results (if any) and return them. */ 4461 if (data->pending_result) { 4462 if (req->type == DNS_IPv4_A) 4463 res = evutil_addrinfo_append(res, 4464 data->pending_result); 4465 else 4466 res = evutil_addrinfo_append( 4467 data->pending_result, res); 4468 data->pending_result = NULL; 4469 } 4470 4471 /* Call the user callback. */ 4472 add_cname_to_reply(data, res); 4473 data->user_cb(0, res, data->user_data); 4474 4475 /* Free data. */ 4476 free_getaddrinfo_request(data); 4477 } 4478 } 4479 4480 static struct hosts_entry * 4481 find_hosts_entry(struct evdns_base *base, const char *hostname, 4482 struct hosts_entry *find_after) 4483 { 4484 struct hosts_entry *e; 4485 4486 if (find_after) 4487 e = TAILQ_NEXT(find_after, next); 4488 else 4489 e = TAILQ_FIRST(&base->hostsdb); 4490 4491 for (; e; e = TAILQ_NEXT(e, next)) { 4492 if (!evutil_ascii_strcasecmp(e->hostname, hostname)) 4493 return e; 4494 } 4495 return NULL; 4496 } 4497 4498 static int 4499 evdns_getaddrinfo_fromhosts(struct evdns_base *base, 4500 const char *nodename, struct evutil_addrinfo *hints, ev_uint16_t port, 4501 struct evutil_addrinfo **res) 4502 { 4503 int n_found = 0; 4504 struct hosts_entry *e; 4505 struct evutil_addrinfo *ai=NULL; 4506 int f = hints->ai_family; 4507 4508 EVDNS_LOCK(base); 4509 for (e = find_hosts_entry(base, nodename, NULL); e; 4510 e = find_hosts_entry(base, nodename, e)) { 4511 struct evutil_addrinfo *ai_new; 4512 ++n_found; 4513 if ((e->addr.sa.sa_family == AF_INET && f == PF_INET6) || 4514 (e->addr.sa.sa_family == AF_INET6 && f == PF_INET)) 4515 continue; 4516 ai_new = evutil_new_addrinfo(&e->addr.sa, e->addrlen, hints); 4517 if (!ai_new) { 4518 n_found = 0; 4519 goto out; 4520 } 4521 sockaddr_setport(ai_new->ai_addr, port); 4522 ai = evutil_addrinfo_append(ai, ai_new); 4523 } 4524 EVDNS_UNLOCK(base); 4525 out: 4526 if (n_found) { 4527 /* Note that we return an empty answer if we found entries for 4528 * this hostname but none were of the right address type. */ 4529 *res = ai; 4530 return 0; 4531 } else { 4532 if (ai) 4533 evutil_freeaddrinfo(ai); 4534 return -1; 4535 } 4536 } 4537 4538 struct evdns_getaddrinfo_request * 4539 evdns_getaddrinfo(struct evdns_base *dns_base, 4540 const char *nodename, const char *servname, 4541 const struct evutil_addrinfo *hints_in, 4542 evdns_getaddrinfo_cb cb, void *arg) 4543 { 4544 struct evdns_getaddrinfo_request *data; 4545 struct evutil_addrinfo hints; 4546 struct evutil_addrinfo *res = NULL; 4547 int err; 4548 int port = 0; 4549 int want_cname = 0; 4550 4551 if (!dns_base) { 4552 dns_base = current_base; 4553 if (!dns_base) { 4554 log(EVDNS_LOG_WARN, 4555 "Call to getaddrinfo_async with no " 4556 "evdns_base configured."); 4557 cb(EVUTIL_EAI_FAIL, NULL, arg); /* ??? better error? */ 4558 return NULL; 4559 } 4560 } 4561 4562 /* If we _must_ answer this immediately, do so. */ 4563 if ((hints_in && (hints_in->ai_flags & EVUTIL_AI_NUMERICHOST))) { 4564 res = NULL; 4565 err = evutil_getaddrinfo(nodename, servname, hints_in, &res); 4566 cb(err, res, arg); 4567 return NULL; 4568 } 4569 4570 if (hints_in) { 4571 memcpy(&hints, hints_in, sizeof(hints)); 4572 } else { 4573 memset(&hints, 0, sizeof(hints)); 4574 hints.ai_family = PF_UNSPEC; 4575 } 4576 4577 evutil_adjust_hints_for_addrconfig(&hints); 4578 4579 /* Now try to see if we _can_ answer immediately. */ 4580 /* (It would be nice to do this by calling getaddrinfo directly, with 4581 * AI_NUMERICHOST, on plaforms that have it, but we can't: there isn't 4582 * a reliable way to distinguish the "that wasn't a numeric host!" case 4583 * from any other EAI_NONAME cases.) */ 4584 err = evutil_getaddrinfo_common(nodename, servname, &hints, &res, &port); 4585 if (err != EVUTIL_EAI_NEED_RESOLVE) { 4586 cb(err, res, arg); 4587 return NULL; 4588 } 4589 4590 /* If there is an entry in the hosts file, we should give it now. */ 4591 if (!evdns_getaddrinfo_fromhosts(dns_base, nodename, &hints, port, &res)) { 4592 cb(0, res, arg); 4593 return NULL; 4594 } 4595 4596 /* Okay, things are serious now. We're going to need to actually 4597 * launch a request. 4598 */ 4599 data = mm_calloc(1,sizeof(struct evdns_getaddrinfo_request)); 4600 if (!data) { 4601 cb(EVUTIL_EAI_MEMORY, NULL, arg); 4602 return NULL; 4603 } 4604 4605 memcpy(&data->hints, &hints, sizeof(data->hints)); 4606 data->port = (ev_uint16_t)port; 4607 data->ipv4_request.type = DNS_IPv4_A; 4608 data->ipv6_request.type = DNS_IPv6_AAAA; 4609 data->user_cb = cb; 4610 data->user_data = arg; 4611 data->evdns_base = dns_base; 4612 4613 want_cname = (hints.ai_flags & EVUTIL_AI_CANONNAME); 4614 4615 /* If we are asked for a PF_UNSPEC address, we launch two requests in 4616 * parallel: one for an A address and one for an AAAA address. We 4617 * can't send just one request, since many servers only answer one 4618 * question per DNS request. 4619 * 4620 * Once we have the answer to one request, we allow for a short 4621 * timeout before we report it, to see if the other one arrives. If 4622 * they both show up in time, then we report both the answers. 4623 * 4624 * If too many addresses of one type time out or fail, we should stop 4625 * launching those requests. (XXX we don't do that yet.) 4626 */ 4627 4628 if (hints.ai_family != PF_INET6) { 4629 log(EVDNS_LOG_DEBUG, "Sending request for %s on ipv4 as %p", 4630 nodename, &data->ipv4_request); 4631 4632 data->ipv4_request.r = evdns_base_resolve_ipv4(dns_base, 4633 nodename, 0, evdns_getaddrinfo_gotresolve, 4634 &data->ipv4_request); 4635 if (want_cname) 4636 data->ipv4_request.r->current_req->put_cname_in_ptr = 4637 &data->cname_result; 4638 } 4639 if (hints.ai_family != PF_INET) { 4640 log(EVDNS_LOG_DEBUG, "Sending request for %s on ipv6 as %p", 4641 nodename, &data->ipv6_request); 4642 4643 data->ipv6_request.r = evdns_base_resolve_ipv6(dns_base, 4644 nodename, 0, evdns_getaddrinfo_gotresolve, 4645 &data->ipv6_request); 4646 if (want_cname) 4647 data->ipv6_request.r->current_req->put_cname_in_ptr = 4648 &data->cname_result; 4649 } 4650 4651 evtimer_assign(&data->timeout, dns_base->event_base, 4652 evdns_getaddrinfo_timeout_cb, data); 4653 4654 if (data->ipv4_request.r || data->ipv6_request.r) { 4655 return data; 4656 } else { 4657 mm_free(data); 4658 cb(EVUTIL_EAI_FAIL, NULL, arg); 4659 return NULL; 4660 } 4661 } 4662 4663 void 4664 evdns_getaddrinfo_cancel(struct evdns_getaddrinfo_request *data) 4665 { 4666 EVDNS_LOCK(data->evdns_base); 4667 if (data->request_done) { 4668 EVDNS_UNLOCK(data->evdns_base); 4669 return; 4670 } 4671 event_del(&data->timeout); 4672 data->user_canceled = 1; 4673 if (data->ipv4_request.r) 4674 evdns_cancel_request(data->evdns_base, data->ipv4_request.r); 4675 if (data->ipv6_request.r) 4676 evdns_cancel_request(data->evdns_base, data->ipv6_request.r); 4677 EVDNS_UNLOCK(data->evdns_base); 4678 } 4679