1 /* $NetBSD: evdns.c,v 1.2 2013/04/11 16:56:41 christos 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 1.2 2013/04/11 16:56:41 christos 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 static void 734 evdns_requests_pump_waiting_queue(struct evdns_base *base) { 735 ASSERT_LOCKED(base); 736 while (base->global_requests_inflight < base->global_max_requests_inflight && 737 base->global_requests_waiting) { 738 struct request *req; 739 /* move a request from the waiting queue to the inflight queue */ 740 EVUTIL_ASSERT(base->req_waiting_head); 741 req = base->req_waiting_head; 742 evdns_request_remove(req, &base->req_waiting_head); 743 744 base->global_requests_waiting--; 745 base->global_requests_inflight++; 746 747 req->ns = nameserver_pick(base); 748 request_trans_id_set(req, transaction_id_pick(base)); 749 750 evdns_request_insert(req, &REQ_HEAD(base, req->trans_id)); 751 evdns_request_transmit(req); 752 evdns_transmit(base); 753 } 754 } 755 756 /* TODO(nickm) document */ 757 struct deferred_reply_callback { 758 struct deferred_cb deferred; 759 struct evdns_request *handle; 760 u8 request_type; 761 u8 have_reply; 762 u32 ttl; 763 u32 err; 764 evdns_callback_type user_callback; 765 struct reply reply; 766 }; 767 768 static void 769 reply_run_callback(struct deferred_cb *d, void *user_pointer) 770 { 771 struct deferred_reply_callback *cb = 772 EVUTIL_UPCAST(d, struct deferred_reply_callback, deferred); 773 774 switch (cb->request_type) { 775 case TYPE_A: 776 if (cb->have_reply) 777 cb->user_callback(DNS_ERR_NONE, DNS_IPv4_A, 778 cb->reply.data.a.addrcount, cb->ttl, 779 cb->reply.data.a.addresses, 780 user_pointer); 781 else 782 cb->user_callback(cb->err, 0, 0, cb->ttl, NULL, user_pointer); 783 break; 784 case TYPE_PTR: 785 if (cb->have_reply) { 786 char *name = cb->reply.data.ptr.name; 787 cb->user_callback(DNS_ERR_NONE, DNS_PTR, 1, cb->ttl, 788 &name, user_pointer); 789 } else { 790 cb->user_callback(cb->err, 0, 0, cb->ttl, NULL, user_pointer); 791 } 792 break; 793 case TYPE_AAAA: 794 if (cb->have_reply) 795 cb->user_callback(DNS_ERR_NONE, DNS_IPv6_AAAA, 796 cb->reply.data.aaaa.addrcount, cb->ttl, 797 cb->reply.data.aaaa.addresses, 798 user_pointer); 799 else 800 cb->user_callback(cb->err, 0, 0, cb->ttl, NULL, user_pointer); 801 break; 802 default: 803 EVUTIL_ASSERT(0); 804 } 805 806 if (cb->handle && cb->handle->pending_cb) { 807 mm_free(cb->handle); 808 } 809 810 mm_free(cb); 811 } 812 813 static void 814 reply_schedule_callback(struct request *const req, u32 ttl, u32 err, struct reply *reply) 815 { 816 struct deferred_reply_callback *d = mm_calloc(1, sizeof(*d)); 817 818 if (!d) { 819 event_warn("%s: Couldn't allocate space for deferred callback.", 820 __func__); 821 return; 822 } 823 824 ASSERT_LOCKED(req->base); 825 826 d->request_type = req->request_type; 827 d->user_callback = req->user_callback; 828 d->ttl = ttl; 829 d->err = err; 830 if (reply) { 831 d->have_reply = 1; 832 memcpy(&d->reply, reply, sizeof(struct reply)); 833 } 834 835 if (req->handle) { 836 req->handle->pending_cb = 1; 837 d->handle = req->handle; 838 } 839 840 event_deferred_cb_init(&d->deferred, reply_run_callback, 841 req->user_pointer); 842 event_deferred_cb_schedule( 843 event_base_get_deferred_cb_queue(req->base->event_base), 844 &d->deferred); 845 } 846 847 /* this processes a parsed reply packet */ 848 static void 849 reply_handle(struct request *const req, u16 flags, u32 ttl, struct reply *reply) { 850 int error; 851 char addrbuf[128]; 852 static const int error_codes[] = { 853 DNS_ERR_FORMAT, DNS_ERR_SERVERFAILED, DNS_ERR_NOTEXIST, 854 DNS_ERR_NOTIMPL, DNS_ERR_REFUSED 855 }; 856 857 ASSERT_LOCKED(req->base); 858 ASSERT_VALID_REQUEST(req); 859 860 if (flags & 0x020f || !reply || !reply->have_answer) { 861 /* there was an error */ 862 if (flags & 0x0200) { 863 error = DNS_ERR_TRUNCATED; 864 } else if (flags & 0x000f) { 865 u16 error_code = (flags & 0x000f) - 1; 866 if (error_code > 4) { 867 error = DNS_ERR_UNKNOWN; 868 } else { 869 error = error_codes[error_code]; 870 } 871 } else if (reply && !reply->have_answer) { 872 error = DNS_ERR_NODATA; 873 } else { 874 error = DNS_ERR_UNKNOWN; 875 } 876 877 switch (error) { 878 case DNS_ERR_NOTIMPL: 879 case DNS_ERR_REFUSED: 880 /* we regard these errors as marking a bad nameserver */ 881 if (req->reissue_count < req->base->global_max_reissues) { 882 char msg[64]; 883 evutil_snprintf(msg, sizeof(msg), "Bad response %d (%s)", 884 error, evdns_err_to_string(error)); 885 nameserver_failed(req->ns, msg); 886 if (!request_reissue(req)) return; 887 } 888 break; 889 case DNS_ERR_SERVERFAILED: 890 /* rcode 2 (servfailed) sometimes means "we 891 * are broken" and sometimes (with some binds) 892 * means "that request was very confusing." 893 * Treat this as a timeout, not a failure. 894 */ 895 log(EVDNS_LOG_DEBUG, "Got a SERVERFAILED from nameserver" 896 "at %s; will allow the request to time out.", 897 evutil_format_sockaddr_port( 898 (struct sockaddr *)&req->ns->address, 899 addrbuf, sizeof(addrbuf))); 900 break; 901 default: 902 /* we got a good reply from the nameserver: it is up. */ 903 if (req->handle == req->ns->probe_request) { 904 /* Avoid double-free */ 905 req->ns->probe_request = NULL; 906 } 907 908 nameserver_up(req->ns); 909 } 910 911 if (req->handle->search_state && 912 req->request_type != TYPE_PTR) { 913 /* if we have a list of domains to search in, 914 * try the next one */ 915 if (!search_try_next(req->handle)) { 916 /* a new request was issued so this 917 * request is finished and */ 918 /* the user callback will be made when 919 * that request (or a */ 920 /* child of it) finishes. */ 921 return; 922 } 923 } 924 925 /* all else failed. Pass the failure up */ 926 reply_schedule_callback(req, ttl, error, NULL); 927 request_finished(req, &REQ_HEAD(req->base, req->trans_id), 1); 928 } else { 929 /* all ok, tell the user */ 930 reply_schedule_callback(req, ttl, 0, reply); 931 if (req->handle == req->ns->probe_request) 932 req->ns->probe_request = NULL; /* Avoid double-free */ 933 nameserver_up(req->ns); 934 request_finished(req, &REQ_HEAD(req->base, req->trans_id), 1); 935 } 936 } 937 938 static int 939 name_parse(u8 *packet, int length, int *idx, char *name_out, int name_out_len) { 940 int name_end = -1; 941 int j = *idx; 942 int ptr_count = 0; 943 #define GET32(x) do { if (j + 4 > length) goto err; memcpy(&_t32, packet + j, 4); j += 4; x = ntohl(_t32); } while (/*CONSTCOND*/0) 944 #define GET16(x) do { if (j + 2 > length) goto err; memcpy(&_t, packet + j, 2); j += 2; x = ntohs(_t); } while (/*CONSTCOND*/0) 945 #define GET8(x) do { if (j >= length) goto err; x = packet[j++]; } while (/*CONSTCOND*/0) 946 947 char *cp = name_out; 948 const char *const end = name_out + name_out_len; 949 950 /* Normally, names are a series of length prefixed strings terminated */ 951 /* with a length of 0 (the lengths are u8's < 63). */ 952 /* However, the length can start with a pair of 1 bits and that */ 953 /* means that the next 14 bits are a pointer within the current */ 954 /* packet. */ 955 956 for (;;) { 957 u8 label_len; 958 if (j >= length) return -1; 959 GET8(label_len); 960 if (!label_len) break; 961 if (label_len & 0xc0) { 962 u8 ptr_low; 963 GET8(ptr_low); 964 if (name_end < 0) name_end = j; 965 j = (((int)label_len & 0x3f) << 8) + ptr_low; 966 /* Make sure that the target offset is in-bounds. */ 967 if (j < 0 || j >= length) return -1; 968 /* If we've jumped more times than there are characters in the 969 * message, we must have a loop. */ 970 if (++ptr_count > length) return -1; 971 continue; 972 } 973 if (label_len > 63) return -1; 974 if (cp != name_out) { 975 if (cp + 1 >= end) return -1; 976 *cp++ = '.'; 977 } 978 if (cp + label_len >= end) return -1; 979 memcpy(cp, packet + j, label_len); 980 cp += label_len; 981 j += label_len; 982 } 983 if (cp >= end) return -1; 984 *cp = '\0'; 985 if (name_end < 0) 986 *idx = j; 987 else 988 *idx = name_end; 989 return 0; 990 err: 991 return -1; 992 } 993 994 /* parses a raw request from a nameserver */ 995 static int 996 reply_parse(struct evdns_base *base, u8 *packet, int length) { 997 int j = 0, k = 0; /* index into packet */ 998 u16 _t; /* used by the macros */ 999 u32 _t32; /* used by the macros */ 1000 char tmp_name[256], cmp_name[256]; /* used by the macros */ 1001 int name_matches = 0; 1002 1003 u16 trans_id, questions, answers, authority, additional, datalength; 1004 u16 flags = 0; 1005 u32 ttl, ttl_r = 0xffffffff; 1006 struct reply reply; 1007 struct request *req = NULL; 1008 unsigned int i; 1009 1010 ASSERT_LOCKED(base); 1011 1012 GET16(trans_id); 1013 GET16(flags); 1014 GET16(questions); 1015 GET16(answers); 1016 GET16(authority); 1017 GET16(additional); 1018 (void) authority; /* suppress "unused variable" warnings. */ 1019 (void) additional; /* suppress "unused variable" warnings. */ 1020 1021 req = request_find_from_trans_id(base, trans_id); 1022 if (!req) return -1; 1023 EVUTIL_ASSERT(req->base == base); 1024 1025 memset(&reply, 0, sizeof(reply)); 1026 1027 /* If it's not an answer, it doesn't correspond to any request. */ 1028 if (!(flags & 0x8000)) return -1; /* must be an answer */ 1029 if ((flags & 0x020f) && (flags & 0x020f) != DNS_ERR_NOTEXIST) { 1030 /* there was an error and it's not NXDOMAIN */ 1031 goto err; 1032 } 1033 /* if (!answers) return; */ /* must have an answer of some form */ 1034 1035 /* This macro skips a name in the DNS reply. */ 1036 #define SKIP_NAME \ 1037 do { tmp_name[0] = '\0'; \ 1038 if (name_parse(packet, length, &j, tmp_name, \ 1039 sizeof(tmp_name))<0) \ 1040 goto err; \ 1041 } while (/*CONSTCOND*/0) 1042 #define TEST_NAME \ 1043 do { tmp_name[0] = '\0'; \ 1044 cmp_name[0] = '\0'; \ 1045 k = j; \ 1046 if (name_parse(packet, length, &j, tmp_name, \ 1047 sizeof(tmp_name))<0) \ 1048 goto err; \ 1049 if (name_parse(req->request, req->request_len, &k, \ 1050 cmp_name, sizeof(cmp_name))<0) \ 1051 goto err; \ 1052 if (base->global_randomize_case) { \ 1053 if (strcmp(tmp_name, cmp_name) == 0) \ 1054 name_matches = 1; \ 1055 } else { \ 1056 if (evutil_ascii_strcasecmp(tmp_name, cmp_name) == 0) \ 1057 name_matches = 1; \ 1058 } \ 1059 } while (/*CONSTCOND*/0) 1060 1061 reply.type = req->request_type; 1062 1063 /* skip over each question in the reply */ 1064 for (i = 0; i < questions; ++i) { 1065 /* the question looks like 1066 * <label:name><u16:type><u16:class> 1067 */ 1068 TEST_NAME; 1069 j += 4; 1070 if (j > length) goto err; 1071 } 1072 1073 if (!name_matches) 1074 goto err; 1075 1076 /* now we have the answer section which looks like 1077 * <label:name><u16:type><u16:class><u32:ttl><u16:len><data...> 1078 */ 1079 1080 for (i = 0; i < answers; ++i) { 1081 u16 type, class; 1082 1083 SKIP_NAME; 1084 GET16(type); 1085 GET16(class); 1086 GET32(ttl); 1087 GET16(datalength); 1088 1089 if (type == TYPE_A && class == CLASS_INET) { 1090 int addrcount, addrtocopy; 1091 if (req->request_type != TYPE_A) { 1092 j += datalength; continue; 1093 } 1094 if ((datalength & 3) != 0) /* not an even number of As. */ 1095 goto err; 1096 addrcount = datalength >> 2; 1097 addrtocopy = MIN(MAX_V4_ADDRS - reply.data.a.addrcount, (unsigned)addrcount); 1098 1099 ttl_r = MIN(ttl_r, ttl); 1100 /* we only bother with the first four addresses. */ 1101 if (j + 4*addrtocopy > length) goto err; 1102 memcpy(&reply.data.a.addresses[reply.data.a.addrcount], 1103 packet + j, 4*addrtocopy); 1104 j += 4*addrtocopy; 1105 reply.data.a.addrcount += addrtocopy; 1106 reply.have_answer = 1; 1107 if (reply.data.a.addrcount == MAX_V4_ADDRS) break; 1108 } else if (type == TYPE_PTR && class == CLASS_INET) { 1109 if (req->request_type != TYPE_PTR) { 1110 j += datalength; continue; 1111 } 1112 if (name_parse(packet, length, &j, reply.data.ptr.name, 1113 sizeof(reply.data.ptr.name))<0) 1114 goto err; 1115 ttl_r = MIN(ttl_r, ttl); 1116 reply.have_answer = 1; 1117 break; 1118 } else if (type == TYPE_CNAME) { 1119 char cname[HOST_NAME_MAX]; 1120 if (!req->put_cname_in_ptr || *req->put_cname_in_ptr) { 1121 j += datalength; continue; 1122 } 1123 if (name_parse(packet, length, &j, cname, 1124 sizeof(cname))<0) 1125 goto err; 1126 *req->put_cname_in_ptr = mm_strdup(cname); 1127 } else if (type == TYPE_AAAA && class == CLASS_INET) { 1128 int addrcount, addrtocopy; 1129 if (req->request_type != TYPE_AAAA) { 1130 j += datalength; continue; 1131 } 1132 if ((datalength & 15) != 0) /* not an even number of AAAAs. */ 1133 goto err; 1134 addrcount = datalength >> 4; /* each address is 16 bytes long */ 1135 addrtocopy = MIN(MAX_V6_ADDRS - reply.data.aaaa.addrcount, (unsigned)addrcount); 1136 ttl_r = MIN(ttl_r, ttl); 1137 1138 /* we only bother with the first four addresses. */ 1139 if (j + 16*addrtocopy > length) goto err; 1140 memcpy(&reply.data.aaaa.addresses[reply.data.aaaa.addrcount], 1141 packet + j, 16*addrtocopy); 1142 reply.data.aaaa.addrcount += addrtocopy; 1143 j += 16*addrtocopy; 1144 reply.have_answer = 1; 1145 if (reply.data.aaaa.addrcount == MAX_V6_ADDRS) break; 1146 } else { 1147 /* skip over any other type of resource */ 1148 j += datalength; 1149 } 1150 } 1151 1152 if (!reply.have_answer) { 1153 for (i = 0; i < authority; ++i) { 1154 u16 type, class; 1155 SKIP_NAME; 1156 GET16(type); 1157 GET16(class); 1158 GET32(ttl); 1159 GET16(datalength); 1160 if (type == TYPE_SOA && class == CLASS_INET) { 1161 u32 serial, refresh, retry, expire, minimum; 1162 SKIP_NAME; 1163 SKIP_NAME; 1164 GET32(serial); 1165 GET32(refresh); 1166 GET32(retry); 1167 GET32(expire); 1168 GET32(minimum); 1169 (void)expire; 1170 (void)retry; 1171 (void)refresh; 1172 (void)serial; 1173 ttl_r = MIN(ttl_r, ttl); 1174 ttl_r = MIN(ttl_r, minimum); 1175 } else { 1176 /* skip over any other type of resource */ 1177 j += datalength; 1178 } 1179 } 1180 } 1181 1182 if (ttl_r == 0xffffffff) 1183 ttl_r = 0; 1184 1185 reply_handle(req, flags, ttl_r, &reply); 1186 return 0; 1187 err: 1188 if (req) 1189 reply_handle(req, flags, 0, NULL); 1190 return -1; 1191 } 1192 1193 /* Parse a raw request (packet,length) sent to a nameserver port (port) from */ 1194 /* a DNS client (addr,addrlen), and if it's well-formed, call the corresponding */ 1195 /* callback. */ 1196 static int 1197 request_parse(u8 *packet, int length, struct evdns_server_port *port, struct sockaddr *addr, ev_socklen_t addrlen) 1198 { 1199 int j = 0; /* index into packet */ 1200 u16 _t; /* used by the macros */ 1201 char tmp_name[256]; /* used by the macros */ 1202 1203 int i; 1204 u16 trans_id, flags, questions, answers, authority, additional; 1205 struct server_request *server_req = NULL; 1206 1207 ASSERT_LOCKED(port); 1208 1209 /* Get the header fields */ 1210 GET16(trans_id); 1211 GET16(flags); 1212 GET16(questions); 1213 GET16(answers); 1214 GET16(authority); 1215 GET16(additional); 1216 (void)answers; 1217 (void)additional; 1218 (void)authority; 1219 1220 if (flags & 0x8000) return -1; /* Must not be an answer. */ 1221 flags &= 0x0110; /* Only RD and CD get preserved. */ 1222 1223 server_req = mm_malloc(sizeof(struct server_request)); 1224 if (server_req == NULL) return -1; 1225 memset(server_req, 0, sizeof(struct server_request)); 1226 1227 server_req->trans_id = trans_id; 1228 memcpy(&server_req->addr, addr, addrlen); 1229 server_req->addrlen = addrlen; 1230 1231 server_req->base.flags = flags; 1232 server_req->base.nquestions = 0; 1233 server_req->base.questions = mm_calloc(sizeof(struct evdns_server_question *), questions); 1234 if (server_req->base.questions == NULL) 1235 goto err; 1236 1237 for (i = 0; i < questions; ++i) { 1238 u16 type, class; 1239 struct evdns_server_question *q; 1240 int namelen; 1241 if (name_parse(packet, length, &j, tmp_name, sizeof(tmp_name))<0) 1242 goto err; 1243 GET16(type); 1244 GET16(class); 1245 namelen = (int)strlen(tmp_name); 1246 q = mm_malloc(sizeof(struct evdns_server_question) + namelen); 1247 if (!q) 1248 goto err; 1249 q->type = type; 1250 q->dns_question_class = class; 1251 memcpy(q->name, tmp_name, namelen+1); 1252 server_req->base.questions[server_req->base.nquestions++] = q; 1253 } 1254 1255 /* Ignore answers, authority, and additional. */ 1256 1257 server_req->port = port; 1258 port->refcnt++; 1259 1260 /* Only standard queries are supported. */ 1261 if (flags & 0x7800) { 1262 evdns_server_request_respond(&(server_req->base), DNS_ERR_NOTIMPL); 1263 return -1; 1264 } 1265 1266 port->user_callback(&(server_req->base), port->user_data); 1267 1268 return 0; 1269 err: 1270 if (server_req) { 1271 if (server_req->base.questions) { 1272 for (i = 0; i < server_req->base.nquestions; ++i) 1273 mm_free(server_req->base.questions[i]); 1274 mm_free(server_req->base.questions); 1275 } 1276 mm_free(server_req); 1277 } 1278 return -1; 1279 1280 #undef SKIP_NAME 1281 #undef GET32 1282 #undef GET16 1283 #undef GET8 1284 } 1285 1286 1287 void 1288 evdns_set_transaction_id_fn(ev_uint16_t (*fn)(void)) 1289 { 1290 } 1291 1292 void 1293 evdns_set_random_bytes_fn(void (*fn)(char *, size_t)) 1294 { 1295 } 1296 1297 /* Try to choose a strong transaction id which isn't already in flight */ 1298 static u16 1299 transaction_id_pick(struct evdns_base *base) { 1300 ASSERT_LOCKED(base); 1301 for (;;) { 1302 u16 trans_id; 1303 evutil_secure_rng_get_bytes(&trans_id, sizeof(trans_id)); 1304 1305 if (trans_id == 0xffff) continue; 1306 /* now check to see if that id is already inflight */ 1307 if (request_find_from_trans_id(base, trans_id) == NULL) 1308 return trans_id; 1309 } 1310 } 1311 1312 /* choose a namesever to use. This function will try to ignore */ 1313 /* nameservers which we think are down and load balance across the rest */ 1314 /* by updating the server_head global each time. */ 1315 static struct nameserver * 1316 nameserver_pick(struct evdns_base *base) { 1317 struct nameserver *started_at = base->server_head, *picked; 1318 ASSERT_LOCKED(base); 1319 if (!base->server_head) return NULL; 1320 1321 /* if we don't have any good nameservers then there's no */ 1322 /* point in trying to find one. */ 1323 if (!base->global_good_nameservers) { 1324 base->server_head = base->server_head->next; 1325 return base->server_head; 1326 } 1327 1328 /* remember that nameservers are in a circular list */ 1329 for (;;) { 1330 if (base->server_head->state) { 1331 /* we think this server is currently good */ 1332 picked = base->server_head; 1333 base->server_head = base->server_head->next; 1334 return picked; 1335 } 1336 1337 base->server_head = base->server_head->next; 1338 if (base->server_head == started_at) { 1339 /* all the nameservers seem to be down */ 1340 /* so we just return this one and hope for the */ 1341 /* best */ 1342 EVUTIL_ASSERT(base->global_good_nameservers == 0); 1343 picked = base->server_head; 1344 base->server_head = base->server_head->next; 1345 return picked; 1346 } 1347 } 1348 } 1349 1350 /* this is called when a namesever socket is ready for reading */ 1351 static void 1352 nameserver_read(struct nameserver *ns) { 1353 struct sockaddr_storage ss; 1354 ev_socklen_t addrlen = sizeof(ss); 1355 u8 packet[1500]; 1356 char addrbuf[128]; 1357 ASSERT_LOCKED(ns->base); 1358 1359 for (;;) { 1360 const int r = recvfrom(ns->socket, (void*)packet, 1361 sizeof(packet), 0, 1362 (struct sockaddr*)&ss, &addrlen); 1363 if (r < 0) { 1364 int err = evutil_socket_geterror(ns->socket); 1365 if (EVUTIL_ERR_RW_RETRIABLE(err)) 1366 return; 1367 nameserver_failed(ns, 1368 evutil_socket_error_to_string(err)); 1369 return; 1370 } 1371 if (evutil_sockaddr_cmp((struct sockaddr*)&ss, 1372 (struct sockaddr*)&ns->address, 0)) { 1373 log(EVDNS_LOG_WARN, "Address mismatch on received " 1374 "DNS packet. Apparent source was %s", 1375 evutil_format_sockaddr_port( 1376 (struct sockaddr *)&ss, 1377 addrbuf, sizeof(addrbuf))); 1378 return; 1379 } 1380 1381 ns->timedout = 0; 1382 reply_parse(ns->base, packet, r); 1383 } 1384 } 1385 1386 /* Read a packet from a DNS client on a server port s, parse it, and */ 1387 /* act accordingly. */ 1388 static void 1389 server_port_read(struct evdns_server_port *s) { 1390 u8 packet[1500]; 1391 struct sockaddr_storage addr; 1392 ev_socklen_t addrlen; 1393 int r; 1394 ASSERT_LOCKED(s); 1395 1396 for (;;) { 1397 addrlen = sizeof(struct sockaddr_storage); 1398 r = recvfrom(s->socket, (void*)packet, sizeof(packet), 0, 1399 (struct sockaddr*) &addr, &addrlen); 1400 if (r < 0) { 1401 int err = evutil_socket_geterror(s->socket); 1402 if (EVUTIL_ERR_RW_RETRIABLE(err)) 1403 return; 1404 log(EVDNS_LOG_WARN, 1405 "Error %s (%d) while reading request.", 1406 evutil_socket_error_to_string(err), err); 1407 return; 1408 } 1409 request_parse(packet, r, s, (struct sockaddr*) &addr, addrlen); 1410 } 1411 } 1412 1413 /* Try to write all pending replies on a given DNS server port. */ 1414 static void 1415 server_port_flush(struct evdns_server_port *port) 1416 { 1417 struct server_request *req = port->pending_replies; 1418 ASSERT_LOCKED(port); 1419 while (req) { 1420 int r = sendto(port->socket, req->response, (int)req->response_len, 0, 1421 (struct sockaddr*) &req->addr, (ev_socklen_t)req->addrlen); 1422 if (r < 0) { 1423 int err = evutil_socket_geterror(port->socket); 1424 if (EVUTIL_ERR_RW_RETRIABLE(err)) 1425 return; 1426 log(EVDNS_LOG_WARN, "Error %s (%d) while writing response to port; dropping", evutil_socket_error_to_string(err), err); 1427 } 1428 if (server_request_free(req)) { 1429 /* we released the last reference to req->port. */ 1430 return; 1431 } else { 1432 EVUTIL_ASSERT(req != port->pending_replies); 1433 req = port->pending_replies; 1434 } 1435 } 1436 1437 /* We have no more pending requests; stop listening for 'writeable' events. */ 1438 (void) event_del(&port->event); 1439 event_assign(&port->event, port->event_base, 1440 port->socket, EV_READ | EV_PERSIST, 1441 server_port_ready_callback, port); 1442 1443 if (event_add(&port->event, NULL) < 0) { 1444 log(EVDNS_LOG_WARN, "Error from libevent when adding event for DNS server."); 1445 /* ???? Do more? */ 1446 } 1447 } 1448 1449 /* set if we are waiting for the ability to write to this server. */ 1450 /* if waiting is true then we ask libevent for EV_WRITE events, otherwise */ 1451 /* we stop these events. */ 1452 static void 1453 nameserver_write_waiting(struct nameserver *ns, char waiting) { 1454 ASSERT_LOCKED(ns->base); 1455 if (ns->write_waiting == waiting) return; 1456 1457 ns->write_waiting = waiting; 1458 (void) event_del(&ns->event); 1459 event_assign(&ns->event, ns->base->event_base, 1460 ns->socket, EV_READ | (waiting ? EV_WRITE : 0) | EV_PERSIST, 1461 nameserver_ready_callback, ns); 1462 if (event_add(&ns->event, NULL) < 0) { 1463 char addrbuf[128]; 1464 log(EVDNS_LOG_WARN, "Error from libevent when adding event for %s", 1465 evutil_format_sockaddr_port( 1466 (struct sockaddr *)&ns->address, 1467 addrbuf, sizeof(addrbuf))); 1468 /* ???? Do more? */ 1469 } 1470 } 1471 1472 /* a callback function. Called by libevent when the kernel says that */ 1473 /* a nameserver socket is ready for writing or reading */ 1474 static void 1475 nameserver_ready_callback(evutil_socket_t fd, short events, void *arg) { 1476 struct nameserver *ns = (struct nameserver *) arg; 1477 (void)fd; 1478 1479 EVDNS_LOCK(ns->base); 1480 if (events & EV_WRITE) { 1481 ns->choked = 0; 1482 if (!evdns_transmit(ns->base)) { 1483 nameserver_write_waiting(ns, 0); 1484 } 1485 } 1486 if (events & EV_READ) { 1487 nameserver_read(ns); 1488 } 1489 EVDNS_UNLOCK(ns->base); 1490 } 1491 1492 /* a callback function. Called by libevent when the kernel says that */ 1493 /* a server socket is ready for writing or reading. */ 1494 static void 1495 server_port_ready_callback(evutil_socket_t fd, short events, void *arg) { 1496 struct evdns_server_port *port = (struct evdns_server_port *) arg; 1497 (void) fd; 1498 1499 EVDNS_LOCK(port); 1500 if (events & EV_WRITE) { 1501 port->choked = 0; 1502 server_port_flush(port); 1503 } 1504 if (events & EV_READ) { 1505 server_port_read(port); 1506 } 1507 EVDNS_UNLOCK(port); 1508 } 1509 1510 /* This is an inefficient representation; only use it via the dnslabel_table_* 1511 * functions, so that is can be safely replaced with something smarter later. */ 1512 #define MAX_LABELS 128 1513 /* Structures used to implement name compression */ 1514 struct dnslabel_entry { char *v; off_t pos; }; 1515 struct dnslabel_table { 1516 int n_labels; /* number of current entries */ 1517 /* map from name to position in message */ 1518 struct dnslabel_entry labels[MAX_LABELS]; 1519 }; 1520 1521 /* Initialize dnslabel_table. */ 1522 static void 1523 dnslabel_table_init(struct dnslabel_table *table) 1524 { 1525 table->n_labels = 0; 1526 } 1527 1528 /* Free all storage held by table, but not the table itself. */ 1529 static void 1530 dnslabel_clear(struct dnslabel_table *table) 1531 { 1532 int i; 1533 for (i = 0; i < table->n_labels; ++i) 1534 mm_free(table->labels[i].v); 1535 table->n_labels = 0; 1536 } 1537 1538 /* return the position of the label in the current message, or -1 if the label */ 1539 /* hasn't been used yet. */ 1540 static int 1541 dnslabel_table_get_pos(const struct dnslabel_table *table, const char *label) 1542 { 1543 int i; 1544 for (i = 0; i < table->n_labels; ++i) { 1545 if (!strcmp(label, table->labels[i].v)) 1546 return table->labels[i].pos; 1547 } 1548 return -1; 1549 } 1550 1551 /* remember that we've used the label at position pos */ 1552 static int 1553 dnslabel_table_add(struct dnslabel_table *table, const char *label, off_t pos) 1554 { 1555 char *v; 1556 int p; 1557 if (table->n_labels == MAX_LABELS) 1558 return (-1); 1559 v = mm_strdup(label); 1560 if (v == NULL) 1561 return (-1); 1562 p = table->n_labels++; 1563 table->labels[p].v = v; 1564 table->labels[p].pos = pos; 1565 1566 return (0); 1567 } 1568 1569 /* Converts a string to a length-prefixed set of DNS labels, starting */ 1570 /* at buf[j]. name and buf must not overlap. name_len should be the length */ 1571 /* of name. table is optional, and is used for compression. */ 1572 /* */ 1573 /* Input: abc.def */ 1574 /* Output: <3>abc<3>def<0> */ 1575 /* */ 1576 /* Returns the first index after the encoded name, or negative on error. */ 1577 /* -1 label was > 63 bytes */ 1578 /* -2 name too long to fit in buffer. */ 1579 /* */ 1580 static off_t 1581 dnsname_to_labels(u8 *const buf, size_t buf_len, off_t j, 1582 const char *name, const size_t name_len, 1583 struct dnslabel_table *table) { 1584 const char *end = name + name_len; 1585 int ref = 0; 1586 u16 _t; 1587 1588 #define APPEND16(x) do { \ 1589 if (j + 2 > (off_t)buf_len) \ 1590 goto overflow; \ 1591 _t = htons(x); \ 1592 memcpy(buf + j, &_t, 2); \ 1593 j += 2; \ 1594 } while (/*CONSTCOND*/0) 1595 #define APPEND32(x) do { \ 1596 if (j + 4 > (off_t)buf_len) \ 1597 goto overflow; \ 1598 _t32 = htonl(x); \ 1599 memcpy(buf + j, &_t32, 4); \ 1600 j += 4; \ 1601 } while (/*CONSTCOND*/0) 1602 1603 if (name_len > 255) return -2; 1604 1605 for (;;) { 1606 const char *const start = name; 1607 if (table && (ref = dnslabel_table_get_pos(table, name)) >= 0) { 1608 APPEND16(ref | 0xc000); 1609 return j; 1610 } 1611 name = strchr(name, '.'); 1612 if (!name) { 1613 const size_t label_len = end - start; 1614 if (label_len > 63) return -1; 1615 if ((size_t)(j+label_len+1) > buf_len) return -2; 1616 if (table) dnslabel_table_add(table, start, j); 1617 buf[j++] = (ev_uint8_t)label_len; 1618 1619 memcpy(buf + j, start, label_len); 1620 j += (int) label_len; 1621 break; 1622 } else { 1623 /* append length of the label. */ 1624 const size_t label_len = name - start; 1625 if (label_len > 63) return -1; 1626 if ((size_t)(j+label_len+1) > buf_len) return -2; 1627 if (table) dnslabel_table_add(table, start, j); 1628 buf[j++] = (ev_uint8_t)label_len; 1629 1630 memcpy(buf + j, start, label_len); 1631 j += (int) label_len; 1632 /* hop over the '.' */ 1633 name++; 1634 } 1635 } 1636 1637 /* the labels must be terminated by a 0. */ 1638 /* It's possible that the name ended in a . */ 1639 /* in which case the zero is already there */ 1640 if (!j || buf[j-1]) buf[j++] = 0; 1641 return j; 1642 overflow: 1643 return (-2); 1644 } 1645 1646 /* Finds the length of a dns request for a DNS name of the given */ 1647 /* length. The actual request may be smaller than the value returned */ 1648 /* here */ 1649 static size_t 1650 evdns_request_len(const size_t name_len) { 1651 return 96 + /* length of the DNS standard header */ 1652 name_len + 2 + 1653 4; /* space for the resource type */ 1654 } 1655 1656 /* build a dns request packet into buf. buf should be at least as long */ 1657 /* as evdns_request_len told you it should be. */ 1658 /* */ 1659 /* Returns the amount of space used. Negative on error. */ 1660 static int 1661 evdns_request_data_build(const char *const name, const size_t name_len, 1662 const u16 trans_id, const u16 type, const u16 class, 1663 u8 *const buf, size_t buf_len) { 1664 off_t j = 0; /* current offset into buf */ 1665 u16 _t; /* used by the macros */ 1666 1667 APPEND16(trans_id); 1668 APPEND16(0x0100); /* standard query, recusion needed */ 1669 APPEND16(1); /* one question */ 1670 APPEND16(0); /* no answers */ 1671 APPEND16(0); /* no authority */ 1672 APPEND16(0); /* no additional */ 1673 1674 j = dnsname_to_labels(buf, buf_len, j, name, name_len, NULL); 1675 if (j < 0) { 1676 return (int)j; 1677 } 1678 1679 APPEND16(type); 1680 APPEND16(class); 1681 1682 return (int)j; 1683 overflow: 1684 return (-1); 1685 } 1686 1687 /* exported function */ 1688 struct evdns_server_port * 1689 evdns_add_server_port_with_base(struct event_base *base, evutil_socket_t sock, int flags, evdns_request_callback_fn_type cb, void *user_data) 1690 { 1691 struct evdns_server_port *port; 1692 if (flags) 1693 return NULL; /* flags not yet implemented */ 1694 if (!(port = mm_malloc(sizeof(struct evdns_server_port)))) 1695 return NULL; 1696 memset(port, 0, sizeof(struct evdns_server_port)); 1697 1698 1699 port->socket = sock; 1700 port->refcnt = 1; 1701 port->choked = 0; 1702 port->closing = 0; 1703 port->user_callback = cb; 1704 port->user_data = user_data; 1705 port->pending_replies = NULL; 1706 port->event_base = base; 1707 1708 event_assign(&port->event, port->event_base, 1709 port->socket, EV_READ | EV_PERSIST, 1710 server_port_ready_callback, port); 1711 if (event_add(&port->event, NULL) < 0) { 1712 mm_free(port); 1713 return NULL; 1714 } 1715 EVTHREAD_ALLOC_LOCK(port->lock, EVTHREAD_LOCKTYPE_RECURSIVE); 1716 return port; 1717 } 1718 1719 struct evdns_server_port * 1720 evdns_add_server_port(evutil_socket_t sock, int flags, evdns_request_callback_fn_type cb, void *user_data) 1721 { 1722 return evdns_add_server_port_with_base(NULL, sock, flags, cb, user_data); 1723 } 1724 1725 /* exported function */ 1726 void 1727 evdns_close_server_port(struct evdns_server_port *port) 1728 { 1729 EVDNS_LOCK(port); 1730 if (--port->refcnt == 0) { 1731 EVDNS_UNLOCK(port); 1732 server_port_free(port); 1733 } else { 1734 port->closing = 1; 1735 } 1736 } 1737 1738 /* exported function */ 1739 int 1740 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) 1741 { 1742 struct server_request *req = TO_SERVER_REQUEST(_req); 1743 struct server_reply_item **itemp, *item; 1744 int *countp; 1745 int result = -1; 1746 1747 EVDNS_LOCK(req->port); 1748 if (req->response) /* have we already answered? */ 1749 goto done; 1750 1751 switch (section) { 1752 case EVDNS_ANSWER_SECTION: 1753 itemp = &req->answer; 1754 countp = &req->n_answer; 1755 break; 1756 case EVDNS_AUTHORITY_SECTION: 1757 itemp = &req->authority; 1758 countp = &req->n_authority; 1759 break; 1760 case EVDNS_ADDITIONAL_SECTION: 1761 itemp = &req->additional; 1762 countp = &req->n_additional; 1763 break; 1764 default: 1765 goto done; 1766 } 1767 while (*itemp) { 1768 itemp = &((*itemp)->next); 1769 } 1770 item = mm_malloc(sizeof(struct server_reply_item)); 1771 if (!item) 1772 goto done; 1773 item->next = NULL; 1774 if (!(item->name = mm_strdup(name))) { 1775 mm_free(item); 1776 goto done; 1777 } 1778 item->type = type; 1779 item->dns_question_class = class; 1780 item->ttl = ttl; 1781 item->is_name = is_name != 0; 1782 item->datalen = 0; 1783 item->data = NULL; 1784 if (data) { 1785 if (item->is_name) { 1786 if (!(item->data = mm_strdup(data))) { 1787 mm_free(item->name); 1788 mm_free(item); 1789 goto done; 1790 } 1791 item->datalen = (u16)-1; 1792 } else { 1793 if (!(item->data = mm_malloc(datalen))) { 1794 mm_free(item->name); 1795 mm_free(item); 1796 goto done; 1797 } 1798 item->datalen = datalen; 1799 memcpy(item->data, data, datalen); 1800 } 1801 } 1802 1803 *itemp = item; 1804 ++(*countp); 1805 result = 0; 1806 done: 1807 EVDNS_UNLOCK(req->port); 1808 return result; 1809 } 1810 1811 /* exported function */ 1812 int 1813 evdns_server_request_add_a_reply(struct evdns_server_request *req, const char *name, int n, const void *addrs, int ttl) 1814 { 1815 return evdns_server_request_add_reply( 1816 req, EVDNS_ANSWER_SECTION, name, TYPE_A, CLASS_INET, 1817 ttl, n*4, 0, addrs); 1818 } 1819 1820 /* exported function */ 1821 int 1822 evdns_server_request_add_aaaa_reply(struct evdns_server_request *req, const char *name, int n, const void *addrs, int ttl) 1823 { 1824 return evdns_server_request_add_reply( 1825 req, EVDNS_ANSWER_SECTION, name, TYPE_AAAA, CLASS_INET, 1826 ttl, n*16, 0, addrs); 1827 } 1828 1829 /* exported function */ 1830 int 1831 evdns_server_request_add_ptr_reply(struct evdns_server_request *req, struct in_addr *in, const char *inaddr_name, const char *hostname, int ttl) 1832 { 1833 u32 a; 1834 char buf[32]; 1835 if (in && inaddr_name) 1836 return -1; 1837 else if (!in && !inaddr_name) 1838 return -1; 1839 if (in) { 1840 a = ntohl(in->s_addr); 1841 evutil_snprintf(buf, sizeof(buf), "%d.%d.%d.%d.in-addr.arpa", 1842 (int)(u8)((a )&0xff), 1843 (int)(u8)((a>>8 )&0xff), 1844 (int)(u8)((a>>16)&0xff), 1845 (int)(u8)((a>>24)&0xff)); 1846 inaddr_name = buf; 1847 } 1848 return evdns_server_request_add_reply( 1849 req, EVDNS_ANSWER_SECTION, inaddr_name, TYPE_PTR, CLASS_INET, 1850 ttl, -1, 1, hostname); 1851 } 1852 1853 /* exported function */ 1854 int 1855 evdns_server_request_add_cname_reply(struct evdns_server_request *req, const char *name, const char *cname, int ttl) 1856 { 1857 return evdns_server_request_add_reply( 1858 req, EVDNS_ANSWER_SECTION, name, TYPE_CNAME, CLASS_INET, 1859 ttl, -1, 1, cname); 1860 } 1861 1862 /* exported function */ 1863 void 1864 evdns_server_request_set_flags(struct evdns_server_request *exreq, int flags) 1865 { 1866 struct server_request *req = TO_SERVER_REQUEST(exreq); 1867 req->base.flags &= ~(EVDNS_FLAGS_AA|EVDNS_FLAGS_RD); 1868 req->base.flags |= flags; 1869 } 1870 1871 static int 1872 evdns_server_request_format_response(struct server_request *req, int err) 1873 { 1874 unsigned char buf[1500]; 1875 size_t buf_len = sizeof(buf); 1876 off_t j = 0, r; 1877 u16 _t; 1878 u32 _t32; 1879 int i; 1880 u16 flags; 1881 struct dnslabel_table table; 1882 1883 if (err < 0 || err > 15) return -1; 1884 1885 /* Set response bit and error code; copy OPCODE and RD fields from 1886 * question; copy RA and AA if set by caller. */ 1887 flags = req->base.flags; 1888 flags |= (0x8000 | err); 1889 1890 dnslabel_table_init(&table); 1891 APPEND16(req->trans_id); 1892 APPEND16(flags); 1893 APPEND16(req->base.nquestions); 1894 APPEND16(req->n_answer); 1895 APPEND16(req->n_authority); 1896 APPEND16(req->n_additional); 1897 1898 /* Add questions. */ 1899 for (i=0; i < req->base.nquestions; ++i) { 1900 const char *s = req->base.questions[i]->name; 1901 j = dnsname_to_labels(buf, buf_len, j, s, strlen(s), &table); 1902 if (j < 0) { 1903 dnslabel_clear(&table); 1904 return (int) j; 1905 } 1906 APPEND16(req->base.questions[i]->type); 1907 APPEND16(req->base.questions[i]->dns_question_class); 1908 } 1909 1910 /* Add answer, authority, and additional sections. */ 1911 for (i=0; i<3; ++i) { 1912 struct server_reply_item *item; 1913 if (i==0) 1914 item = req->answer; 1915 else if (i==1) 1916 item = req->authority; 1917 else 1918 item = req->additional; 1919 while (item) { 1920 r = dnsname_to_labels(buf, buf_len, j, item->name, strlen(item->name), &table); 1921 if (r < 0) 1922 goto overflow; 1923 j = r; 1924 1925 APPEND16(item->type); 1926 APPEND16(item->dns_question_class); 1927 APPEND32(item->ttl); 1928 if (item->is_name) { 1929 off_t len_idx = j, name_start; 1930 j += 2; 1931 name_start = j; 1932 r = dnsname_to_labels(buf, buf_len, j, item->data, strlen(item->data), &table); 1933 if (r < 0) 1934 goto overflow; 1935 j = r; 1936 _t = htons( (short) (j-name_start) ); 1937 memcpy(buf+len_idx, &_t, 2); 1938 } else { 1939 APPEND16(item->datalen); 1940 if (j+item->datalen > (off_t)buf_len) 1941 goto overflow; 1942 memcpy(buf+j, item->data, item->datalen); 1943 j += item->datalen; 1944 } 1945 item = item->next; 1946 } 1947 } 1948 1949 if (j > 512) { 1950 overflow: 1951 j = 512; 1952 buf[2] |= 0x02; /* set the truncated bit. */ 1953 } 1954 1955 req->response_len = j; 1956 1957 if (!(req->response = mm_malloc(req->response_len))) { 1958 server_request_free_answers(req); 1959 dnslabel_clear(&table); 1960 return (-1); 1961 } 1962 memcpy(req->response, buf, req->response_len); 1963 server_request_free_answers(req); 1964 dnslabel_clear(&table); 1965 return (0); 1966 } 1967 1968 /* exported function */ 1969 int 1970 evdns_server_request_respond(struct evdns_server_request *_req, int err) 1971 { 1972 struct server_request *req = TO_SERVER_REQUEST(_req); 1973 struct evdns_server_port *port = req->port; 1974 int r = -1; 1975 1976 EVDNS_LOCK(port); 1977 if (!req->response) { 1978 if ((r = evdns_server_request_format_response(req, err))<0) 1979 goto done; 1980 } 1981 1982 r = sendto(port->socket, req->response, (int)req->response_len, 0, 1983 (struct sockaddr*) &req->addr, (ev_socklen_t)req->addrlen); 1984 if (r<0) { 1985 int sock_err = evutil_socket_geterror(port->socket); 1986 if (EVUTIL_ERR_RW_RETRIABLE(sock_err)) 1987 goto done; 1988 1989 if (port->pending_replies) { 1990 req->prev_pending = port->pending_replies->prev_pending; 1991 req->next_pending = port->pending_replies; 1992 req->prev_pending->next_pending = 1993 req->next_pending->prev_pending = req; 1994 } else { 1995 req->prev_pending = req->next_pending = req; 1996 port->pending_replies = req; 1997 port->choked = 1; 1998 1999 (void) event_del(&port->event); 2000 event_assign(&port->event, port->event_base, port->socket, (port->closing?0:EV_READ) | EV_WRITE | EV_PERSIST, server_port_ready_callback, port); 2001 2002 if (event_add(&port->event, NULL) < 0) { 2003 log(EVDNS_LOG_WARN, "Error from libevent when adding event for DNS server"); 2004 } 2005 2006 } 2007 2008 r = 1; 2009 goto done; 2010 } 2011 if (server_request_free(req)) { 2012 r = 0; 2013 goto done; 2014 } 2015 2016 if (port->pending_replies) 2017 server_port_flush(port); 2018 2019 r = 0; 2020 done: 2021 EVDNS_UNLOCK(port); 2022 return r; 2023 } 2024 2025 /* Free all storage held by RRs in req. */ 2026 static void 2027 server_request_free_answers(struct server_request *req) 2028 { 2029 struct server_reply_item *victim, *next, **list; 2030 int i; 2031 for (i = 0; i < 3; ++i) { 2032 if (i==0) 2033 list = &req->answer; 2034 else if (i==1) 2035 list = &req->authority; 2036 else 2037 list = &req->additional; 2038 2039 victim = *list; 2040 while (victim) { 2041 next = victim->next; 2042 mm_free(victim->name); 2043 if (victim->data) 2044 mm_free(victim->data); 2045 mm_free(victim); 2046 victim = next; 2047 } 2048 *list = NULL; 2049 } 2050 } 2051 2052 /* Free all storage held by req, and remove links to it. */ 2053 /* return true iff we just wound up freeing the server_port. */ 2054 static int 2055 server_request_free(struct server_request *req) 2056 { 2057 int i, rc=1, lock=0; 2058 if (req->base.questions) { 2059 for (i = 0; i < req->base.nquestions; ++i) 2060 mm_free(req->base.questions[i]); 2061 mm_free(req->base.questions); 2062 } 2063 2064 if (req->port) { 2065 EVDNS_LOCK(req->port); 2066 lock=1; 2067 if (req->port->pending_replies == req) { 2068 if (req->next_pending && req->next_pending != req) 2069 req->port->pending_replies = req->next_pending; 2070 else 2071 req->port->pending_replies = NULL; 2072 } 2073 rc = --req->port->refcnt; 2074 } 2075 2076 if (req->response) { 2077 mm_free(req->response); 2078 } 2079 2080 server_request_free_answers(req); 2081 2082 if (req->next_pending && req->next_pending != req) { 2083 req->next_pending->prev_pending = req->prev_pending; 2084 req->prev_pending->next_pending = req->next_pending; 2085 } 2086 2087 if (rc == 0) { 2088 EVDNS_UNLOCK(req->port); /* ????? nickm */ 2089 server_port_free(req->port); 2090 mm_free(req); 2091 return (1); 2092 } 2093 if (lock) 2094 EVDNS_UNLOCK(req->port); 2095 mm_free(req); 2096 return (0); 2097 } 2098 2099 /* Free all storage held by an evdns_server_port. Only called when */ 2100 static void 2101 server_port_free(struct evdns_server_port *port) 2102 { 2103 EVUTIL_ASSERT(port); 2104 EVUTIL_ASSERT(!port->refcnt); 2105 EVUTIL_ASSERT(!port->pending_replies); 2106 if (port->socket > 0) { 2107 evutil_closesocket(port->socket); 2108 port->socket = -1; 2109 } 2110 (void) event_del(&port->event); 2111 event_debug_unassign(&port->event); 2112 EVTHREAD_FREE_LOCK(port->lock, EVTHREAD_LOCKTYPE_RECURSIVE); 2113 mm_free(port); 2114 } 2115 2116 /* exported function */ 2117 int 2118 evdns_server_request_drop(struct evdns_server_request *_req) 2119 { 2120 struct server_request *req = TO_SERVER_REQUEST(_req); 2121 server_request_free(req); 2122 return 0; 2123 } 2124 2125 /* exported function */ 2126 int 2127 evdns_server_request_get_requesting_addr(struct evdns_server_request *_req, struct sockaddr *sa, int addr_len) 2128 { 2129 struct server_request *req = TO_SERVER_REQUEST(_req); 2130 if (addr_len < (int)req->addrlen) 2131 return -1; 2132 memcpy(sa, &(req->addr), req->addrlen); 2133 return req->addrlen; 2134 } 2135 2136 #undef APPEND16 2137 #undef APPEND32 2138 2139 /* this is a libevent callback function which is called when a request */ 2140 /* has timed out. */ 2141 static void 2142 evdns_request_timeout_callback(evutil_socket_t fd, short events, void *arg) { 2143 struct request *const req = (struct request *) arg; 2144 struct evdns_base *base = req->base; 2145 2146 (void) fd; 2147 (void) events; 2148 2149 log(EVDNS_LOG_DEBUG, "Request %p timed out", arg); 2150 EVDNS_LOCK(base); 2151 2152 req->ns->timedout++; 2153 if (req->ns->timedout > req->base->global_max_nameserver_timeout) { 2154 req->ns->timedout = 0; 2155 nameserver_failed(req->ns, "request timed out."); 2156 } 2157 2158 if (req->tx_count >= req->base->global_max_retransmits) { 2159 /* this request has failed */ 2160 log(EVDNS_LOG_DEBUG, "Giving up on request %p; tx_count==%d", 2161 arg, req->tx_count); 2162 reply_schedule_callback(req, 0, DNS_ERR_TIMEOUT, NULL); 2163 request_finished(req, &REQ_HEAD(req->base, req->trans_id), 1); 2164 } else { 2165 /* retransmit it */ 2166 struct nameserver *new_ns; 2167 log(EVDNS_LOG_DEBUG, "Retransmitting request %p; tx_count==%d", 2168 arg, req->tx_count); 2169 (void) evtimer_del(&req->timeout_event); 2170 new_ns = nameserver_pick(base); 2171 if (new_ns) 2172 req->ns = new_ns; 2173 evdns_request_transmit(req); 2174 } 2175 EVDNS_UNLOCK(base); 2176 } 2177 2178 /* try to send a request to a given server. */ 2179 /* */ 2180 /* return: */ 2181 /* 0 ok */ 2182 /* 1 temporary failure */ 2183 /* 2 other failure */ 2184 static int 2185 evdns_request_transmit_to(struct request *req, struct nameserver *server) { 2186 int r; 2187 ASSERT_LOCKED(req->base); 2188 ASSERT_VALID_REQUEST(req); 2189 r = sendto(server->socket, (void*)req->request, req->request_len, 0, 2190 (struct sockaddr *)&server->address, server->addrlen); 2191 if (r < 0) { 2192 int err = evutil_socket_geterror(server->socket); 2193 if (EVUTIL_ERR_RW_RETRIABLE(err)) 2194 return 1; 2195 nameserver_failed(req->ns, evutil_socket_error_to_string(err)); 2196 return 2; 2197 } else if (r != (int)req->request_len) { 2198 return 1; /* short write */ 2199 } else { 2200 return 0; 2201 } 2202 } 2203 2204 /* try to send a request, updating the fields of the request */ 2205 /* as needed */ 2206 /* */ 2207 /* return: */ 2208 /* 0 ok */ 2209 /* 1 failed */ 2210 static int 2211 evdns_request_transmit(struct request *req) { 2212 int retcode = 0, r; 2213 2214 ASSERT_LOCKED(req->base); 2215 ASSERT_VALID_REQUEST(req); 2216 /* if we fail to send this packet then this flag marks it */ 2217 /* for evdns_transmit */ 2218 req->transmit_me = 1; 2219 EVUTIL_ASSERT(req->trans_id != 0xffff); 2220 2221 if (req->ns->choked) { 2222 /* don't bother trying to write to a socket */ 2223 /* which we have had EAGAIN from */ 2224 return 1; 2225 } 2226 2227 r = evdns_request_transmit_to(req, req->ns); 2228 switch (r) { 2229 case 1: 2230 /* temp failure */ 2231 req->ns->choked = 1; 2232 nameserver_write_waiting(req->ns, 1); 2233 return 1; 2234 case 2: 2235 /* failed to transmit the request entirely. */ 2236 retcode = 1; 2237 /* fall through: we'll set a timeout, which will time out, 2238 * and make us retransmit the request anyway. */ 2239 default: 2240 /* all ok */ 2241 log(EVDNS_LOG_DEBUG, 2242 "Setting timeout for request %p, sent to nameserver %p", req, req->ns); 2243 if (evtimer_add(&req->timeout_event, &req->base->global_timeout) < 0) { 2244 log(EVDNS_LOG_WARN, 2245 "Error from libevent when adding timer for request %p", 2246 req); 2247 /* ???? Do more? */ 2248 } 2249 req->tx_count++; 2250 req->transmit_me = 0; 2251 return retcode; 2252 } 2253 } 2254 2255 static void 2256 nameserver_probe_callback(int result, char type, int count, int ttl, void *addresses, void *arg) { 2257 struct nameserver *const ns = (struct nameserver *) arg; 2258 (void) type; 2259 (void) count; 2260 (void) ttl; 2261 (void) addresses; 2262 2263 if (result == DNS_ERR_CANCEL) { 2264 /* We canceled this request because the nameserver came up 2265 * for some other reason. Do not change our opinion about 2266 * the nameserver. */ 2267 return; 2268 } 2269 2270 EVDNS_LOCK(ns->base); 2271 ns->probe_request = NULL; 2272 if (result == DNS_ERR_NONE || result == DNS_ERR_NOTEXIST) { 2273 /* this is a good reply */ 2274 nameserver_up(ns); 2275 } else { 2276 nameserver_probe_failed(ns); 2277 } 2278 EVDNS_UNLOCK(ns->base); 2279 } 2280 2281 static void 2282 nameserver_send_probe(struct nameserver *const ns) { 2283 struct evdns_request *handle; 2284 struct request *req; 2285 char addrbuf[128]; 2286 /* here we need to send a probe to a given nameserver */ 2287 /* in the hope that it is up now. */ 2288 2289 ASSERT_LOCKED(ns->base); 2290 log(EVDNS_LOG_DEBUG, "Sending probe to %s", 2291 evutil_format_sockaddr_port( 2292 (struct sockaddr *)&ns->address, 2293 addrbuf, sizeof(addrbuf))); 2294 handle = mm_calloc(1, sizeof(*handle)); 2295 if (!handle) return; 2296 req = request_new(ns->base, handle, TYPE_A, "google.com", DNS_QUERY_NO_SEARCH, nameserver_probe_callback, ns); 2297 if (!req) { 2298 mm_free(handle); 2299 return; 2300 } 2301 ns->probe_request = handle; 2302 /* we force this into the inflight queue no matter what */ 2303 request_trans_id_set(req, transaction_id_pick(ns->base)); 2304 req->ns = ns; 2305 request_submit(req); 2306 } 2307 2308 /* returns: */ 2309 /* 0 didn't try to transmit anything */ 2310 /* 1 tried to transmit something */ 2311 static int 2312 evdns_transmit(struct evdns_base *base) { 2313 char did_try_to_transmit = 0; 2314 int i; 2315 2316 ASSERT_LOCKED(base); 2317 for (i = 0; i < base->n_req_heads; ++i) { 2318 if (base->req_heads[i]) { 2319 struct request *const started_at = base->req_heads[i], *req = started_at; 2320 /* first transmit all the requests which are currently waiting */ 2321 do { 2322 if (req->transmit_me) { 2323 did_try_to_transmit = 1; 2324 evdns_request_transmit(req); 2325 } 2326 2327 req = req->next; 2328 } while (req != started_at); 2329 } 2330 } 2331 2332 return did_try_to_transmit; 2333 } 2334 2335 /* exported function */ 2336 int 2337 evdns_base_count_nameservers(struct evdns_base *base) 2338 { 2339 const struct nameserver *server; 2340 int n = 0; 2341 2342 EVDNS_LOCK(base); 2343 server = base->server_head; 2344 if (!server) 2345 goto done; 2346 do { 2347 ++n; 2348 server = server->next; 2349 } while (server != base->server_head); 2350 done: 2351 EVDNS_UNLOCK(base); 2352 return n; 2353 } 2354 2355 int 2356 evdns_count_nameservers(void) 2357 { 2358 return evdns_base_count_nameservers(current_base); 2359 } 2360 2361 /* exported function */ 2362 int 2363 evdns_base_clear_nameservers_and_suspend(struct evdns_base *base) 2364 { 2365 struct nameserver *server, *started_at; 2366 int i; 2367 2368 EVDNS_LOCK(base); 2369 server = base->server_head; 2370 started_at = base->server_head; 2371 if (!server) { 2372 EVDNS_UNLOCK(base); 2373 return 0; 2374 } 2375 while (1) { 2376 struct nameserver *next = server->next; 2377 (void) event_del(&server->event); 2378 if (evtimer_initialized(&server->timeout_event)) 2379 (void) evtimer_del(&server->timeout_event); 2380 if (server->probe_request) { 2381 evdns_cancel_request(server->base, server->probe_request); 2382 server->probe_request = NULL; 2383 } 2384 if (server->socket >= 0) 2385 evutil_closesocket(server->socket); 2386 mm_free(server); 2387 if (next == started_at) 2388 break; 2389 server = next; 2390 } 2391 base->server_head = NULL; 2392 base->global_good_nameservers = 0; 2393 2394 for (i = 0; i < base->n_req_heads; ++i) { 2395 struct request *req, *req_started_at; 2396 req = req_started_at = base->req_heads[i]; 2397 while (req) { 2398 struct request *next = req->next; 2399 req->tx_count = req->reissue_count = 0; 2400 req->ns = NULL; 2401 /* ???? What to do about searches? */ 2402 (void) evtimer_del(&req->timeout_event); 2403 req->trans_id = 0; 2404 req->transmit_me = 0; 2405 2406 base->global_requests_waiting++; 2407 evdns_request_insert(req, &base->req_waiting_head); 2408 /* We want to insert these suspended elements at the front of 2409 * the waiting queue, since they were pending before any of 2410 * the waiting entries were added. This is a circular list, 2411 * so we can just shift the start back by one.*/ 2412 base->req_waiting_head = base->req_waiting_head->prev; 2413 2414 if (next == req_started_at) 2415 break; 2416 req = next; 2417 } 2418 base->req_heads[i] = NULL; 2419 } 2420 2421 base->global_requests_inflight = 0; 2422 2423 EVDNS_UNLOCK(base); 2424 return 0; 2425 } 2426 2427 int 2428 evdns_clear_nameservers_and_suspend(void) 2429 { 2430 return evdns_base_clear_nameservers_and_suspend(current_base); 2431 } 2432 2433 2434 /* exported function */ 2435 int 2436 evdns_base_resume(struct evdns_base *base) 2437 { 2438 EVDNS_LOCK(base); 2439 evdns_requests_pump_waiting_queue(base); 2440 EVDNS_UNLOCK(base); 2441 return 0; 2442 } 2443 2444 int 2445 evdns_resume(void) 2446 { 2447 return evdns_base_resume(current_base); 2448 } 2449 2450 static int 2451 _evdns_nameserver_add_impl(struct evdns_base *base, const struct sockaddr *address, int addrlen) { 2452 /* first check to see if we already have this nameserver */ 2453 2454 const struct nameserver *server = base->server_head, *const started_at = base->server_head; 2455 struct nameserver *ns; 2456 int err = 0; 2457 char addrbuf[128]; 2458 2459 ASSERT_LOCKED(base); 2460 if (server) { 2461 do { 2462 if (!evutil_sockaddr_cmp((const struct sockaddr*)&server->address, address, 1)) return 3; 2463 server = server->next; 2464 } while (server != started_at); 2465 } 2466 if (addrlen > (int)sizeof(ns->address)) { 2467 log(EVDNS_LOG_DEBUG, "Addrlen %d too long.", (int)addrlen); 2468 return 2; 2469 } 2470 2471 ns = (struct nameserver *) mm_malloc(sizeof(struct nameserver)); 2472 if (!ns) return -1; 2473 2474 memset(ns, 0, sizeof(struct nameserver)); 2475 ns->base = base; 2476 2477 evtimer_assign(&ns->timeout_event, ns->base->event_base, nameserver_prod_callback, ns); 2478 2479 ns->socket = socket(address->sa_family, SOCK_DGRAM, 0); 2480 if (ns->socket < 0) { err = 1; goto out1; } 2481 evutil_make_socket_closeonexec(ns->socket); 2482 evutil_make_socket_nonblocking(ns->socket); 2483 2484 if (base->global_outgoing_addrlen && 2485 !evutil_sockaddr_is_loopback(address)) { 2486 if (bind(ns->socket, 2487 (struct sockaddr*)&base->global_outgoing_address, 2488 base->global_outgoing_addrlen) < 0) { 2489 log(EVDNS_LOG_WARN,"Couldn't bind to outgoing address"); 2490 err = 2; 2491 goto out2; 2492 } 2493 } 2494 2495 memcpy(&ns->address, address, addrlen); 2496 ns->addrlen = addrlen; 2497 ns->state = 1; 2498 event_assign(&ns->event, ns->base->event_base, ns->socket, EV_READ | EV_PERSIST, nameserver_ready_callback, ns); 2499 if (event_add(&ns->event, NULL) < 0) { 2500 err = 2; 2501 goto out2; 2502 } 2503 2504 log(EVDNS_LOG_DEBUG, "Added nameserver %s as %p", 2505 evutil_format_sockaddr_port(address, addrbuf, sizeof(addrbuf)), ns); 2506 2507 /* insert this nameserver into the list of them */ 2508 if (!base->server_head) { 2509 ns->next = ns->prev = ns; 2510 base->server_head = ns; 2511 } else { 2512 ns->next = base->server_head->next; 2513 ns->prev = base->server_head; 2514 base->server_head->next = ns; 2515 ns->next->prev = ns; 2516 } 2517 2518 base->global_good_nameservers++; 2519 2520 return 0; 2521 2522 out2: 2523 evutil_closesocket(ns->socket); 2524 out1: 2525 event_debug_unassign(&ns->event); 2526 mm_free(ns); 2527 log(EVDNS_LOG_WARN, "Unable to add nameserver %s: error %d", 2528 evutil_format_sockaddr_port(address, addrbuf, sizeof(addrbuf)), err); 2529 return err; 2530 } 2531 2532 /* exported function */ 2533 int 2534 evdns_base_nameserver_add(struct evdns_base *base, unsigned long int address) 2535 { 2536 struct sockaddr_in sin; 2537 int res; 2538 memset(&sin, 0, sizeof(sin)); 2539 sin.sin_addr.s_addr = address; 2540 sin.sin_port = htons(53); 2541 sin.sin_family = AF_INET; 2542 EVDNS_LOCK(base); 2543 res = _evdns_nameserver_add_impl(base, (struct sockaddr*)&sin, sizeof(sin)); 2544 EVDNS_UNLOCK(base); 2545 return res; 2546 } 2547 2548 int 2549 evdns_nameserver_add(unsigned long int address) { 2550 if (!current_base) 2551 current_base = evdns_base_new(NULL, 0); 2552 return evdns_base_nameserver_add(current_base, address); 2553 } 2554 2555 static void 2556 sockaddr_setport(struct sockaddr *sa, ev_uint16_t port) 2557 { 2558 if (sa->sa_family == AF_INET) { 2559 ((struct sockaddr_in *)sa)->sin_port = htons(port); 2560 } else if (sa->sa_family == AF_INET6) { 2561 ((struct sockaddr_in6 *)sa)->sin6_port = htons(port); 2562 } 2563 } 2564 2565 static ev_uint16_t 2566 sockaddr_getport(struct sockaddr *sa) 2567 { 2568 if (sa->sa_family == AF_INET) { 2569 return ntohs(((struct sockaddr_in *)sa)->sin_port); 2570 } else if (sa->sa_family == AF_INET6) { 2571 return ntohs(((struct sockaddr_in6 *)sa)->sin6_port); 2572 } else { 2573 return 0; 2574 } 2575 } 2576 2577 /* exported function */ 2578 int 2579 evdns_base_nameserver_ip_add(struct evdns_base *base, const char *ip_as_string) { 2580 struct sockaddr_storage ss; 2581 struct sockaddr *sa; 2582 int len = sizeof(ss); 2583 int res; 2584 if (evutil_parse_sockaddr_port(ip_as_string, (struct sockaddr *)&ss, 2585 &len)) { 2586 log(EVDNS_LOG_WARN, "Unable to parse nameserver address %s", 2587 ip_as_string); 2588 return 4; 2589 } 2590 sa = (struct sockaddr *) &ss; 2591 if (sockaddr_getport(sa) == 0) 2592 sockaddr_setport(sa, 53); 2593 2594 EVDNS_LOCK(base); 2595 res = _evdns_nameserver_add_impl(base, sa, len); 2596 EVDNS_UNLOCK(base); 2597 return res; 2598 } 2599 2600 int 2601 evdns_nameserver_ip_add(const char *ip_as_string) { 2602 if (!current_base) 2603 current_base = evdns_base_new(NULL, 0); 2604 return evdns_base_nameserver_ip_add(current_base, ip_as_string); 2605 } 2606 2607 int 2608 evdns_base_nameserver_sockaddr_add(struct evdns_base *base, 2609 const struct sockaddr *sa, ev_socklen_t len, unsigned flags) 2610 { 2611 int res; 2612 EVUTIL_ASSERT(base); 2613 EVDNS_LOCK(base); 2614 res = _evdns_nameserver_add_impl(base, sa, len); 2615 EVDNS_UNLOCK(base); 2616 return res; 2617 } 2618 2619 /* remove from the queue */ 2620 static void 2621 evdns_request_remove(struct request *req, struct request **head) 2622 { 2623 ASSERT_LOCKED(req->base); 2624 ASSERT_VALID_REQUEST(req); 2625 2626 #if 0 2627 { 2628 struct request *ptr; 2629 int found = 0; 2630 EVUTIL_ASSERT(*head != NULL); 2631 2632 ptr = *head; 2633 do { 2634 if (ptr == req) { 2635 found = 1; 2636 break; 2637 } 2638 ptr = ptr->next; 2639 } while (ptr != *head); 2640 EVUTIL_ASSERT(found); 2641 2642 EVUTIL_ASSERT(req->next); 2643 } 2644 #endif 2645 2646 if (req->next == req) { 2647 /* only item in the list */ 2648 *head = NULL; 2649 } else { 2650 req->next->prev = req->prev; 2651 req->prev->next = req->next; 2652 if (*head == req) *head = req->next; 2653 } 2654 req->next = req->prev = NULL; 2655 } 2656 2657 /* insert into the tail of the queue */ 2658 static void 2659 evdns_request_insert(struct request *req, struct request **head) { 2660 ASSERT_LOCKED(req->base); 2661 ASSERT_VALID_REQUEST(req); 2662 if (!*head) { 2663 *head = req; 2664 req->next = req->prev = req; 2665 return; 2666 } 2667 2668 req->prev = (*head)->prev; 2669 req->prev->next = req; 2670 req->next = *head; 2671 (*head)->prev = req; 2672 } 2673 2674 static int 2675 string_num_dots(const char *s) { 2676 int count = 0; 2677 while ((s = strchr(s, '.'))) { 2678 s++; 2679 count++; 2680 } 2681 return count; 2682 } 2683 2684 static struct request * 2685 request_new(struct evdns_base *base, struct evdns_request *handle, int type, 2686 const char *name, int flags, evdns_callback_type callback, 2687 void *user_ptr) { 2688 2689 const char issuing_now = 2690 (base->global_requests_inflight < base->global_max_requests_inflight) ? 1 : 0; 2691 2692 const size_t name_len = strlen(name); 2693 const size_t request_max_len = evdns_request_len(name_len); 2694 const u16 trans_id = issuing_now ? transaction_id_pick(base) : 0xffff; 2695 /* the request data is alloced in a single block with the header */ 2696 struct request *const req = 2697 mm_malloc(sizeof(struct request) + request_max_len); 2698 int rlen; 2699 char namebuf[256]; 2700 (void) flags; 2701 2702 ASSERT_LOCKED(base); 2703 2704 if (!req) return NULL; 2705 2706 if (name_len >= sizeof(namebuf)) { 2707 mm_free(req); 2708 return NULL; 2709 } 2710 2711 memset(req, 0, sizeof(struct request)); 2712 req->base = base; 2713 2714 evtimer_assign(&req->timeout_event, req->base->event_base, evdns_request_timeout_callback, req); 2715 2716 if (base->global_randomize_case) { 2717 unsigned i; 2718 char randbits[(sizeof(namebuf)+7)/8]; 2719 strlcpy(namebuf, name, sizeof(namebuf)); 2720 evutil_secure_rng_get_bytes(randbits, (name_len+7)/8); 2721 for (i = 0; i < name_len; ++i) { 2722 if (EVUTIL_ISALPHA(namebuf[i])) { 2723 if ((randbits[i >> 3] & (1<<(i & 7)))) 2724 namebuf[i] |= 0x20; 2725 else 2726 namebuf[i] &= ~0x20; 2727 } 2728 } 2729 name = namebuf; 2730 } 2731 2732 /* request data lives just after the header */ 2733 req->request = ((u8 *) req) + sizeof(struct request); 2734 /* denotes that the request data shouldn't be free()ed */ 2735 req->request_appended = 1; 2736 rlen = evdns_request_data_build(name, name_len, trans_id, 2737 type, CLASS_INET, req->request, request_max_len); 2738 if (rlen < 0) 2739 goto err1; 2740 2741 req->request_len = rlen; 2742 req->trans_id = trans_id; 2743 req->tx_count = 0; 2744 req->request_type = type; 2745 req->user_pointer = user_ptr; 2746 req->user_callback = callback; 2747 req->ns = issuing_now ? nameserver_pick(base) : NULL; 2748 req->next = req->prev = NULL; 2749 req->handle = handle; 2750 if (handle) { 2751 handle->current_req = req; 2752 handle->base = base; 2753 } 2754 2755 return req; 2756 err1: 2757 mm_free(req); 2758 return NULL; 2759 } 2760 2761 static void 2762 request_submit(struct request *const req) { 2763 struct evdns_base *base = req->base; 2764 ASSERT_LOCKED(base); 2765 ASSERT_VALID_REQUEST(req); 2766 if (req->ns) { 2767 /* if it has a nameserver assigned then this is going */ 2768 /* straight into the inflight queue */ 2769 evdns_request_insert(req, &REQ_HEAD(base, req->trans_id)); 2770 base->global_requests_inflight++; 2771 evdns_request_transmit(req); 2772 } else { 2773 evdns_request_insert(req, &base->req_waiting_head); 2774 base->global_requests_waiting++; 2775 } 2776 } 2777 2778 /* exported function */ 2779 void 2780 evdns_cancel_request(struct evdns_base *base, struct evdns_request *handle) 2781 { 2782 struct request *req; 2783 2784 if (!handle->current_req) 2785 return; 2786 2787 if (!base) { 2788 /* This redundancy is silly; can we fix it? (Not for 2.0) XXXX */ 2789 base = handle->base; 2790 if (!base) 2791 base = handle->current_req->base; 2792 } 2793 2794 EVDNS_LOCK(base); 2795 if (handle->pending_cb) { 2796 EVDNS_UNLOCK(base); 2797 return; 2798 } 2799 2800 req = handle->current_req; 2801 ASSERT_VALID_REQUEST(req); 2802 2803 reply_schedule_callback(req, 0, DNS_ERR_CANCEL, NULL); 2804 if (req->ns) { 2805 /* remove from inflight queue */ 2806 request_finished(req, &REQ_HEAD(base, req->trans_id), 1); 2807 } else { 2808 /* remove from global_waiting head */ 2809 request_finished(req, &base->req_waiting_head, 1); 2810 } 2811 EVDNS_UNLOCK(base); 2812 } 2813 2814 /* exported function */ 2815 struct evdns_request * 2816 evdns_base_resolve_ipv4(struct evdns_base *base, const char *name, int flags, 2817 evdns_callback_type callback, void *ptr) { 2818 struct evdns_request *handle; 2819 struct request *req; 2820 log(EVDNS_LOG_DEBUG, "Resolve requested for %s", name); 2821 handle = mm_calloc(1, sizeof(*handle)); 2822 if (handle == NULL) 2823 return NULL; 2824 EVDNS_LOCK(base); 2825 if (flags & DNS_QUERY_NO_SEARCH) { 2826 req = 2827 request_new(base, handle, TYPE_A, name, flags, 2828 callback, ptr); 2829 if (req) 2830 request_submit(req); 2831 } else { 2832 search_request_new(base, handle, TYPE_A, name, flags, 2833 callback, ptr); 2834 } 2835 if (handle->current_req == NULL) { 2836 mm_free(handle); 2837 handle = NULL; 2838 } 2839 EVDNS_UNLOCK(base); 2840 return handle; 2841 } 2842 2843 int evdns_resolve_ipv4(const char *name, int flags, 2844 evdns_callback_type callback, void *ptr) 2845 { 2846 return evdns_base_resolve_ipv4(current_base, name, flags, callback, ptr) 2847 ? 0 : -1; 2848 } 2849 2850 2851 /* exported function */ 2852 struct evdns_request * 2853 evdns_base_resolve_ipv6(struct evdns_base *base, 2854 const char *name, int flags, 2855 evdns_callback_type callback, void *ptr) 2856 { 2857 struct evdns_request *handle; 2858 struct request *req; 2859 log(EVDNS_LOG_DEBUG, "Resolve requested for %s", name); 2860 handle = mm_calloc(1, sizeof(*handle)); 2861 if (handle == NULL) 2862 return NULL; 2863 EVDNS_LOCK(base); 2864 if (flags & DNS_QUERY_NO_SEARCH) { 2865 req = request_new(base, handle, TYPE_AAAA, name, flags, 2866 callback, ptr); 2867 if (req) 2868 request_submit(req); 2869 } else { 2870 search_request_new(base, handle, TYPE_AAAA, name, flags, 2871 callback, ptr); 2872 } 2873 if (handle->current_req == NULL) { 2874 mm_free(handle); 2875 handle = NULL; 2876 } 2877 EVDNS_UNLOCK(base); 2878 return handle; 2879 } 2880 2881 int evdns_resolve_ipv6(const char *name, int flags, 2882 evdns_callback_type callback, void *ptr) { 2883 return evdns_base_resolve_ipv6(current_base, name, flags, callback, ptr) 2884 ? 0 : -1; 2885 } 2886 2887 struct evdns_request * 2888 evdns_base_resolve_reverse(struct evdns_base *base, const struct in_addr *in, int flags, evdns_callback_type callback, void *ptr) { 2889 char buf[32]; 2890 struct evdns_request *handle; 2891 struct request *req; 2892 u32 a; 2893 EVUTIL_ASSERT(in); 2894 a = ntohl(in->s_addr); 2895 evutil_snprintf(buf, sizeof(buf), "%d.%d.%d.%d.in-addr.arpa", 2896 (int)(u8)((a )&0xff), 2897 (int)(u8)((a>>8 )&0xff), 2898 (int)(u8)((a>>16)&0xff), 2899 (int)(u8)((a>>24)&0xff)); 2900 handle = mm_calloc(1, sizeof(*handle)); 2901 if (handle == NULL) 2902 return NULL; 2903 log(EVDNS_LOG_DEBUG, "Resolve requested for %s (reverse)", buf); 2904 EVDNS_LOCK(base); 2905 req = request_new(base, handle, TYPE_PTR, buf, flags, callback, ptr); 2906 if (req) 2907 request_submit(req); 2908 if (handle->current_req == NULL) { 2909 mm_free(handle); 2910 handle = NULL; 2911 } 2912 EVDNS_UNLOCK(base); 2913 return (handle); 2914 } 2915 2916 int evdns_resolve_reverse(const struct in_addr *in, int flags, evdns_callback_type callback, void *ptr) { 2917 return evdns_base_resolve_reverse(current_base, in, flags, callback, ptr) 2918 ? 0 : -1; 2919 } 2920 2921 struct evdns_request * 2922 evdns_base_resolve_reverse_ipv6(struct evdns_base *base, const struct in6_addr *in, int flags, evdns_callback_type callback, void *ptr) { 2923 /* 32 nybbles, 32 periods, "ip6.arpa", NUL. */ 2924 char buf[73]; 2925 char *cp; 2926 struct evdns_request *handle; 2927 struct request *req; 2928 int i; 2929 EVUTIL_ASSERT(in); 2930 cp = buf; 2931 for (i=15; i >= 0; --i) { 2932 u8 byte = in->s6_addr[i]; 2933 *cp++ = "0123456789abcdef"[byte & 0x0f]; 2934 *cp++ = '.'; 2935 *cp++ = "0123456789abcdef"[byte >> 4]; 2936 *cp++ = '.'; 2937 } 2938 EVUTIL_ASSERT(cp + strlen("ip6.arpa") < buf+sizeof(buf)); 2939 memcpy(cp, "ip6.arpa", strlen("ip6.arpa")+1); 2940 handle = mm_calloc(1, sizeof(*handle)); 2941 if (handle == NULL) 2942 return NULL; 2943 log(EVDNS_LOG_DEBUG, "Resolve requested for %s (reverse)", buf); 2944 EVDNS_LOCK(base); 2945 req = request_new(base, handle, TYPE_PTR, buf, flags, callback, ptr); 2946 if (req) 2947 request_submit(req); 2948 if (handle->current_req == NULL) { 2949 mm_free(handle); 2950 handle = NULL; 2951 } 2952 EVDNS_UNLOCK(base); 2953 return (handle); 2954 } 2955 2956 int evdns_resolve_reverse_ipv6(const struct in6_addr *in, int flags, evdns_callback_type callback, void *ptr) { 2957 return evdns_base_resolve_reverse_ipv6(current_base, in, flags, callback, ptr) 2958 ? 0 : -1; 2959 } 2960 2961 /* ================================================================= */ 2962 /* Search support */ 2963 /* */ 2964 /* the libc resolver has support for searching a number of domains */ 2965 /* to find a name. If nothing else then it takes the single domain */ 2966 /* from the gethostname() call. */ 2967 /* */ 2968 /* It can also be configured via the domain and search options in a */ 2969 /* resolv.conf. */ 2970 /* */ 2971 /* The ndots option controls how many dots it takes for the resolver */ 2972 /* to decide that a name is non-local and so try a raw lookup first. */ 2973 2974 struct search_domain { 2975 int len; 2976 struct search_domain *next; 2977 /* the text string is appended to this structure */ 2978 }; 2979 2980 struct search_state { 2981 int refcount; 2982 int ndots; 2983 int num_domains; 2984 struct search_domain *head; 2985 }; 2986 2987 static void 2988 search_state_decref(struct search_state *const state) { 2989 if (!state) return; 2990 state->refcount--; 2991 if (!state->refcount) { 2992 struct search_domain *next, *dom; 2993 for (dom = state->head; dom; dom = next) { 2994 next = dom->next; 2995 mm_free(dom); 2996 } 2997 mm_free(state); 2998 } 2999 } 3000 3001 static struct search_state * 3002 search_state_new(void) { 3003 struct search_state *state = (struct search_state *) mm_malloc(sizeof(struct search_state)); 3004 if (!state) return NULL; 3005 memset(state, 0, sizeof(struct search_state)); 3006 state->refcount = 1; 3007 state->ndots = 1; 3008 3009 return state; 3010 } 3011 3012 static void 3013 search_postfix_clear(struct evdns_base *base) { 3014 search_state_decref(base->global_search_state); 3015 3016 base->global_search_state = search_state_new(); 3017 } 3018 3019 /* exported function */ 3020 void 3021 evdns_base_search_clear(struct evdns_base *base) 3022 { 3023 EVDNS_LOCK(base); 3024 search_postfix_clear(base); 3025 EVDNS_UNLOCK(base); 3026 } 3027 3028 void 3029 evdns_search_clear(void) { 3030 evdns_base_search_clear(current_base); 3031 } 3032 3033 static void 3034 search_postfix_add(struct evdns_base *base, const char *domain) { 3035 size_t domain_len; 3036 struct search_domain *sdomain; 3037 while (domain[0] == '.') domain++; 3038 domain_len = strlen(domain); 3039 3040 ASSERT_LOCKED(base); 3041 if (!base->global_search_state) base->global_search_state = search_state_new(); 3042 if (!base->global_search_state) return; 3043 base->global_search_state->num_domains++; 3044 3045 sdomain = (struct search_domain *) mm_malloc(sizeof(struct search_domain) + domain_len); 3046 if (!sdomain) return; 3047 memcpy( ((u8 *) sdomain) + sizeof(struct search_domain), domain, domain_len); 3048 sdomain->next = base->global_search_state->head; 3049 sdomain->len = (int) domain_len; 3050 3051 base->global_search_state->head = sdomain; 3052 } 3053 3054 /* reverse the order of members in the postfix list. This is needed because, */ 3055 /* when parsing resolv.conf we push elements in the wrong order */ 3056 static void 3057 search_reverse(struct evdns_base *base) { 3058 struct search_domain *cur, *prev = NULL, *next; 3059 ASSERT_LOCKED(base); 3060 cur = base->global_search_state->head; 3061 while (cur) { 3062 next = cur->next; 3063 cur->next = prev; 3064 prev = cur; 3065 cur = next; 3066 } 3067 3068 base->global_search_state->head = prev; 3069 } 3070 3071 /* exported function */ 3072 void 3073 evdns_base_search_add(struct evdns_base *base, const char *domain) { 3074 EVDNS_LOCK(base); 3075 search_postfix_add(base, domain); 3076 EVDNS_UNLOCK(base); 3077 } 3078 void 3079 evdns_search_add(const char *domain) { 3080 evdns_base_search_add(current_base, domain); 3081 } 3082 3083 /* exported function */ 3084 void 3085 evdns_base_search_ndots_set(struct evdns_base *base, const int ndots) { 3086 EVDNS_LOCK(base); 3087 if (!base->global_search_state) base->global_search_state = search_state_new(); 3088 if (base->global_search_state) 3089 base->global_search_state->ndots = ndots; 3090 EVDNS_UNLOCK(base); 3091 } 3092 void 3093 evdns_search_ndots_set(const int ndots) { 3094 evdns_base_search_ndots_set(current_base, ndots); 3095 } 3096 3097 static void 3098 search_set_from_hostname(struct evdns_base *base) { 3099 char hostname[HOST_NAME_MAX + 1], *domainname; 3100 3101 ASSERT_LOCKED(base); 3102 search_postfix_clear(base); 3103 if (gethostname(hostname, sizeof(hostname))) return; 3104 domainname = strchr(hostname, '.'); 3105 if (!domainname) return; 3106 search_postfix_add(base, domainname); 3107 } 3108 3109 /* warning: returns malloced string */ 3110 static char * 3111 search_make_new(const struct search_state *const state, int n, const char *const base_name) { 3112 const size_t base_len = strlen(base_name); 3113 const char need_to_append_dot = base_name[base_len - 1] == '.' ? 0 : 1; 3114 struct search_domain *dom; 3115 3116 for (dom = state->head; dom; dom = dom->next) { 3117 if (!n--) { 3118 /* this is the postfix we want */ 3119 /* the actual postfix string is kept at the end of the structure */ 3120 const u8 *const postfix = ((u8 *) dom) + sizeof(struct search_domain); 3121 const int postfix_len = dom->len; 3122 char *const newname = (char *) mm_malloc(base_len + need_to_append_dot + postfix_len + 1); 3123 if (!newname) return NULL; 3124 memcpy(newname, base_name, base_len); 3125 if (need_to_append_dot) newname[base_len] = '.'; 3126 memcpy(newname + base_len + need_to_append_dot, postfix, postfix_len); 3127 newname[base_len + need_to_append_dot + postfix_len] = 0; 3128 return newname; 3129 } 3130 } 3131 3132 /* we ran off the end of the list and still didn't find the requested string */ 3133 EVUTIL_ASSERT(0); 3134 return NULL; /* unreachable; stops warnings in some compilers. */ 3135 } 3136 3137 static struct request * 3138 search_request_new(struct evdns_base *base, struct evdns_request *handle, 3139 int type, const char *const name, int flags, 3140 evdns_callback_type user_callback, void *user_arg) { 3141 ASSERT_LOCKED(base); 3142 EVUTIL_ASSERT(type == TYPE_A || type == TYPE_AAAA); 3143 EVUTIL_ASSERT(handle->current_req == NULL); 3144 if ( ((flags & DNS_QUERY_NO_SEARCH) == 0) && 3145 base->global_search_state && 3146 base->global_search_state->num_domains) { 3147 /* we have some domains to search */ 3148 struct request *req; 3149 if (string_num_dots(name) >= base->global_search_state->ndots) { 3150 req = request_new(base, handle, type, name, flags, user_callback, user_arg); 3151 if (!req) return NULL; 3152 handle->search_index = -1; 3153 } else { 3154 char *const new_name = search_make_new(base->global_search_state, 0, name); 3155 if (!new_name) return NULL; 3156 req = request_new(base, handle, type, new_name, flags, user_callback, user_arg); 3157 mm_free(new_name); 3158 if (!req) return NULL; 3159 handle->search_index = 0; 3160 } 3161 EVUTIL_ASSERT(handle->search_origname == NULL); 3162 handle->search_origname = mm_strdup(name); 3163 if (handle->search_origname == NULL) { 3164 /* XXX Should we dealloc req? If yes, how? */ 3165 if (req) 3166 mm_free(req); 3167 return NULL; 3168 } 3169 handle->search_state = base->global_search_state; 3170 handle->search_flags = flags; 3171 base->global_search_state->refcount++; 3172 request_submit(req); 3173 return req; 3174 } else { 3175 struct request *const req = request_new(base, handle, type, name, flags, user_callback, user_arg); 3176 if (!req) return NULL; 3177 request_submit(req); 3178 return req; 3179 } 3180 } 3181 3182 /* this is called when a request has failed to find a name. We need to check */ 3183 /* if it is part of a search and, if so, try the next name in the list */ 3184 /* returns: */ 3185 /* 0 another request has been submitted */ 3186 /* 1 no more requests needed */ 3187 static int 3188 search_try_next(struct evdns_request *const handle) { 3189 struct request *req = handle->current_req; 3190 struct evdns_base *base = req->base; 3191 struct request *newreq; 3192 ASSERT_LOCKED(base); 3193 if (handle->search_state) { 3194 /* it is part of a search */ 3195 char *new_name; 3196 handle->search_index++; 3197 if (handle->search_index >= handle->search_state->num_domains) { 3198 /* no more postfixes to try, however we may need to try */ 3199 /* this name without a postfix */ 3200 if (string_num_dots(handle->search_origname) < handle->search_state->ndots) { 3201 /* yep, we need to try it raw */ 3202 newreq = request_new(base, NULL, req->request_type, handle->search_origname, handle->search_flags, req->user_callback, req->user_pointer); 3203 log(EVDNS_LOG_DEBUG, "Search: trying raw query %s", handle->search_origname); 3204 if (newreq) { 3205 search_request_finished(handle); 3206 goto submit_next; 3207 } 3208 } 3209 return 1; 3210 } 3211 3212 new_name = search_make_new(handle->search_state, handle->search_index, handle->search_origname); 3213 if (!new_name) return 1; 3214 log(EVDNS_LOG_DEBUG, "Search: now trying %s (%d)", new_name, handle->search_index); 3215 newreq = request_new(base, NULL, req->request_type, new_name, handle->search_flags, req->user_callback, req->user_pointer); 3216 mm_free(new_name); 3217 if (!newreq) return 1; 3218 goto submit_next; 3219 } 3220 return 1; 3221 3222 submit_next: 3223 request_finished(req, &REQ_HEAD(req->base, req->trans_id), 0); 3224 handle->current_req = newreq; 3225 newreq->handle = handle; 3226 request_submit(newreq); 3227 return 0; 3228 } 3229 3230 static void 3231 search_request_finished(struct evdns_request *const handle) { 3232 ASSERT_LOCKED(handle->current_req->base); 3233 if (handle->search_state) { 3234 search_state_decref(handle->search_state); 3235 handle->search_state = NULL; 3236 } 3237 if (handle->search_origname) { 3238 mm_free(handle->search_origname); 3239 handle->search_origname = NULL; 3240 } 3241 } 3242 3243 /* ================================================================= */ 3244 /* Parsing resolv.conf files */ 3245 3246 static void 3247 evdns_resolv_set_defaults(struct evdns_base *base, int flags) { 3248 /* if the file isn't found then we assume a local resolver */ 3249 ASSERT_LOCKED(base); 3250 if (flags & DNS_OPTION_SEARCH) search_set_from_hostname(base); 3251 if (flags & DNS_OPTION_NAMESERVERS) evdns_base_nameserver_ip_add(base,"127.0.0.1"); 3252 } 3253 3254 #ifndef _EVENT_HAVE_STRTOK_R 3255 static char * 3256 strtok_r(char *s, const char *delim, char **state) { 3257 char *cp, *start; 3258 start = cp = s ? s : *state; 3259 if (!cp) 3260 return NULL; 3261 while (*cp && !strchr(delim, *cp)) 3262 ++cp; 3263 if (!*cp) { 3264 if (cp == start) 3265 return NULL; 3266 *state = NULL; 3267 return start; 3268 } else { 3269 *cp++ = '\0'; 3270 *state = cp; 3271 return start; 3272 } 3273 } 3274 #endif 3275 3276 /* helper version of atoi which returns -1 on error */ 3277 static int 3278 strtoint(const char *const str) 3279 { 3280 char *endptr; 3281 const int r = strtol(str, &endptr, 10); 3282 if (*endptr) return -1; 3283 return r; 3284 } 3285 3286 /* Parse a number of seconds into a timeval; return -1 on error. */ 3287 static int 3288 strtotimeval(const char *const str, struct timeval *out) 3289 { 3290 double d; 3291 char *endptr; 3292 d = strtod(str, &endptr); 3293 if (*endptr) return -1; 3294 if (d < 0) return -1; 3295 out->tv_sec = (int) d; 3296 out->tv_usec = (int) ((d - (int) d)*1000000); 3297 if (out->tv_sec == 0 && out->tv_usec < 1000) /* less than 1 msec */ 3298 return -1; 3299 return 0; 3300 } 3301 3302 /* helper version of atoi that returns -1 on error and clips to bounds. */ 3303 static int 3304 strtoint_clipped(const char *const str, int min, int max) 3305 { 3306 int r = strtoint(str); 3307 if (r == -1) 3308 return r; 3309 else if (r<min) 3310 return min; 3311 else if (r>max) 3312 return max; 3313 else 3314 return r; 3315 } 3316 3317 static int 3318 evdns_base_set_max_requests_inflight(struct evdns_base *base, int maxinflight) 3319 { 3320 int old_n_heads = base->n_req_heads, n_heads; 3321 struct request **old_heads = base->req_heads, **new_heads, *req; 3322 int i; 3323 3324 ASSERT_LOCKED(base); 3325 if (maxinflight < 1) 3326 maxinflight = 1; 3327 n_heads = (maxinflight+4) / 5; 3328 EVUTIL_ASSERT(n_heads > 0); 3329 new_heads = mm_calloc(n_heads, sizeof(struct request*)); 3330 if (!new_heads) 3331 return (-1); 3332 if (old_heads) { 3333 for (i = 0; i < old_n_heads; ++i) { 3334 while (old_heads[i]) { 3335 req = old_heads[i]; 3336 evdns_request_remove(req, &old_heads[i]); 3337 evdns_request_insert(req, &new_heads[req->trans_id % n_heads]); 3338 } 3339 } 3340 mm_free(old_heads); 3341 } 3342 base->req_heads = new_heads; 3343 base->n_req_heads = n_heads; 3344 base->global_max_requests_inflight = maxinflight; 3345 return (0); 3346 } 3347 3348 /* exported function */ 3349 int 3350 evdns_base_set_option(struct evdns_base *base, 3351 const char *option, const char *val) 3352 { 3353 int res; 3354 EVDNS_LOCK(base); 3355 res = evdns_base_set_option_impl(base, option, val, DNS_OPTIONS_ALL); 3356 EVDNS_UNLOCK(base); 3357 return res; 3358 } 3359 3360 static inline int 3361 str_matches_option(const char *s1, const char *optionname) 3362 { 3363 /* Option names are given as "option:" We accept either 'option' in 3364 * s1, or 'option:randomjunk'. The latter form is to implement the 3365 * resolv.conf parser. */ 3366 size_t optlen = strlen(optionname); 3367 size_t slen = strlen(s1); 3368 if (slen == optlen || slen == optlen - 1) 3369 return !strncmp(s1, optionname, slen); 3370 else if (slen > optlen) 3371 return !strncmp(s1, optionname, optlen); 3372 else 3373 return 0; 3374 } 3375 3376 static int 3377 evdns_base_set_option_impl(struct evdns_base *base, 3378 const char *option, const char *val, int flags) 3379 { 3380 ASSERT_LOCKED(base); 3381 if (str_matches_option(option, "ndots:")) { 3382 const int ndots = strtoint(val); 3383 if (ndots == -1) return -1; 3384 if (!(flags & DNS_OPTION_SEARCH)) return 0; 3385 log(EVDNS_LOG_DEBUG, "Setting ndots to %d", ndots); 3386 if (!base->global_search_state) base->global_search_state = search_state_new(); 3387 if (!base->global_search_state) return -1; 3388 base->global_search_state->ndots = ndots; 3389 } else if (str_matches_option(option, "timeout:")) { 3390 struct timeval tv; 3391 if (strtotimeval(val, &tv) == -1) return -1; 3392 if (!(flags & DNS_OPTION_MISC)) return 0; 3393 log(EVDNS_LOG_DEBUG, "Setting timeout to %s", val); 3394 memcpy(&base->global_timeout, &tv, sizeof(struct timeval)); 3395 } else if (str_matches_option(option, "getaddrinfo-allow-skew:")) { 3396 struct timeval tv; 3397 if (strtotimeval(val, &tv) == -1) return -1; 3398 if (!(flags & DNS_OPTION_MISC)) return 0; 3399 log(EVDNS_LOG_DEBUG, "Setting getaddrinfo-allow-skew to %s", 3400 val); 3401 memcpy(&base->global_getaddrinfo_allow_skew, &tv, 3402 sizeof(struct timeval)); 3403 } else if (str_matches_option(option, "max-timeouts:")) { 3404 const int maxtimeout = strtoint_clipped(val, 1, 255); 3405 if (maxtimeout == -1) return -1; 3406 if (!(flags & DNS_OPTION_MISC)) return 0; 3407 log(EVDNS_LOG_DEBUG, "Setting maximum allowed timeouts to %d", 3408 maxtimeout); 3409 base->global_max_nameserver_timeout = maxtimeout; 3410 } else if (str_matches_option(option, "max-inflight:")) { 3411 const int maxinflight = strtoint_clipped(val, 1, 65000); 3412 if (maxinflight == -1) return -1; 3413 if (!(flags & DNS_OPTION_MISC)) return 0; 3414 log(EVDNS_LOG_DEBUG, "Setting maximum inflight requests to %d", 3415 maxinflight); 3416 evdns_base_set_max_requests_inflight(base, maxinflight); 3417 } else if (str_matches_option(option, "attempts:")) { 3418 int retries = strtoint(val); 3419 if (retries == -1) return -1; 3420 if (retries > 255) retries = 255; 3421 if (!(flags & DNS_OPTION_MISC)) return 0; 3422 log(EVDNS_LOG_DEBUG, "Setting retries to %d", retries); 3423 base->global_max_retransmits = retries; 3424 } else if (str_matches_option(option, "randomize-case:")) { 3425 int randcase = strtoint(val); 3426 if (!(flags & DNS_OPTION_MISC)) return 0; 3427 base->global_randomize_case = randcase; 3428 } else if (str_matches_option(option, "bind-to:")) { 3429 /* XXX This only applies to successive nameservers, not 3430 * to already-configured ones. We might want to fix that. */ 3431 int len = sizeof(base->global_outgoing_address); 3432 if (!(flags & DNS_OPTION_NAMESERVERS)) return 0; 3433 if (evutil_parse_sockaddr_port(val, 3434 (struct sockaddr*)&base->global_outgoing_address, &len)) 3435 return -1; 3436 base->global_outgoing_addrlen = len; 3437 } else if (str_matches_option(option, "initial-probe-timeout:")) { 3438 struct timeval tv; 3439 if (strtotimeval(val, &tv) == -1) return -1; 3440 if (tv.tv_sec > 3600) 3441 tv.tv_sec = 3600; 3442 if (!(flags & DNS_OPTION_MISC)) return 0; 3443 log(EVDNS_LOG_DEBUG, "Setting initial probe timeout to %s", 3444 val); 3445 memcpy(&base->global_nameserver_probe_initial_timeout, &tv, 3446 sizeof(tv)); 3447 } 3448 return 0; 3449 } 3450 3451 int 3452 evdns_set_option(const char *option, const char *val, int flags) 3453 { 3454 if (!current_base) 3455 current_base = evdns_base_new(NULL, 0); 3456 return evdns_base_set_option(current_base, option, val); 3457 } 3458 3459 static void 3460 resolv_conf_parse_line(struct evdns_base *base, char *const start, int flags) { 3461 char *strtok_state; 3462 static const char *const delims = " \t"; 3463 #define NEXT_TOKEN strtok_r(NULL, delims, &strtok_state) 3464 3465 3466 char *const first_token = strtok_r(start, delims, &strtok_state); 3467 ASSERT_LOCKED(base); 3468 if (!first_token) return; 3469 3470 if (!strcmp(first_token, "nameserver") && (flags & DNS_OPTION_NAMESERVERS)) { 3471 const char *const nameserver = NEXT_TOKEN; 3472 3473 if (nameserver) 3474 evdns_base_nameserver_ip_add(base, nameserver); 3475 } else if (!strcmp(first_token, "domain") && (flags & DNS_OPTION_SEARCH)) { 3476 const char *const domain = NEXT_TOKEN; 3477 if (domain) { 3478 search_postfix_clear(base); 3479 search_postfix_add(base, domain); 3480 } 3481 } else if (!strcmp(first_token, "search") && (flags & DNS_OPTION_SEARCH)) { 3482 const char *domain; 3483 search_postfix_clear(base); 3484 3485 while ((domain = NEXT_TOKEN)) { 3486 search_postfix_add(base, domain); 3487 } 3488 search_reverse(base); 3489 } else if (!strcmp(first_token, "options")) { 3490 const char *option; 3491 while ((option = NEXT_TOKEN)) { 3492 const char *val = strchr(option, ':'); 3493 evdns_base_set_option_impl(base, option, val ? val+1 : "", flags); 3494 } 3495 } 3496 #undef NEXT_TOKEN 3497 } 3498 3499 /* exported function */ 3500 /* returns: */ 3501 /* 0 no errors */ 3502 /* 1 failed to open file */ 3503 /* 2 failed to stat file */ 3504 /* 3 file too large */ 3505 /* 4 out of memory */ 3506 /* 5 short read from file */ 3507 int 3508 evdns_base_resolv_conf_parse(struct evdns_base *base, int flags, const char *const filename) { 3509 int res; 3510 EVDNS_LOCK(base); 3511 res = evdns_base_resolv_conf_parse_impl(base, flags, filename); 3512 EVDNS_UNLOCK(base); 3513 return res; 3514 } 3515 3516 static char * 3517 evdns_get_default_hosts_filename(void) 3518 { 3519 #ifdef WIN32 3520 /* Windows is a little coy about where it puts its configuration 3521 * files. Sure, they're _usually_ in C:\windows\system32, but 3522 * there's no reason in principle they couldn't be in 3523 * W:\hoboken chicken emergency\ 3524 */ 3525 char path[MAX_PATH+1]; 3526 static const char hostfile[] = "\\drivers\\etc\\hosts"; 3527 char *path_out; 3528 size_t len_out; 3529 3530 if (! SHGetSpecialFolderPathA(NULL, path, CSIDL_SYSTEM, 0)) 3531 return NULL; 3532 len_out = strlen(path)+strlen(hostfile); 3533 path_out = mm_malloc(len_out+1); 3534 evutil_snprintf(path_out, len_out, "%s%s", path, hostfile); 3535 return path_out; 3536 #else 3537 return mm_strdup("/etc/hosts"); 3538 #endif 3539 } 3540 3541 static int 3542 evdns_base_resolv_conf_parse_impl(struct evdns_base *base, int flags, const char *const filename) { 3543 size_t n; 3544 char *resolv; 3545 char *start; 3546 int err = 0; 3547 3548 log(EVDNS_LOG_DEBUG, "Parsing resolv.conf file %s", filename); 3549 3550 if (flags & DNS_OPTION_HOSTSFILE) { 3551 char *fname = evdns_get_default_hosts_filename(); 3552 evdns_base_load_hosts(base, fname); 3553 if (fname) 3554 mm_free(fname); 3555 } 3556 3557 if ((err = evutil_read_file(filename, &resolv, &n, 0)) < 0) { 3558 if (err == -1) { 3559 /* No file. */ 3560 evdns_resolv_set_defaults(base, flags); 3561 return 1; 3562 } else { 3563 return 2; 3564 } 3565 } 3566 3567 start = resolv; 3568 for (;;) { 3569 char *const newline = strchr(start, '\n'); 3570 if (!newline) { 3571 resolv_conf_parse_line(base, start, flags); 3572 break; 3573 } else { 3574 *newline = 0; 3575 resolv_conf_parse_line(base, start, flags); 3576 start = newline + 1; 3577 } 3578 } 3579 3580 if (!base->server_head && (flags & DNS_OPTION_NAMESERVERS)) { 3581 /* no nameservers were configured. */ 3582 evdns_base_nameserver_ip_add(base, "127.0.0.1"); 3583 err = 6; 3584 } 3585 if (flags & DNS_OPTION_SEARCH && (!base->global_search_state || base->global_search_state->num_domains == 0)) { 3586 search_set_from_hostname(base); 3587 } 3588 3589 mm_free(resolv); 3590 return err; 3591 } 3592 3593 int 3594 evdns_resolv_conf_parse(int flags, const char *const filename) { 3595 if (!current_base) 3596 current_base = evdns_base_new(NULL, 0); 3597 return evdns_base_resolv_conf_parse(current_base, flags, filename); 3598 } 3599 3600 3601 #ifdef WIN32 3602 /* Add multiple nameservers from a space-or-comma-separated list. */ 3603 static int 3604 evdns_nameserver_ip_add_line(struct evdns_base *base, const char *ips) { 3605 const char *addr; 3606 char *buf; 3607 int r; 3608 ASSERT_LOCKED(base); 3609 while (*ips) { 3610 while (isspace(*ips) || *ips == ',' || *ips == '\t') 3611 ++ips; 3612 addr = ips; 3613 while (isdigit(*ips) || *ips == '.' || *ips == ':' || 3614 *ips=='[' || *ips==']') 3615 ++ips; 3616 buf = mm_malloc(ips-addr+1); 3617 if (!buf) return 4; 3618 memcpy(buf, addr, ips-addr); 3619 buf[ips-addr] = '\0'; 3620 r = evdns_base_nameserver_ip_add(base, buf); 3621 mm_free(buf); 3622 if (r) return r; 3623 } 3624 return 0; 3625 } 3626 3627 typedef DWORD(WINAPI *GetNetworkParams_fn_t)(FIXED_INFO *, DWORD*); 3628 3629 /* Use the windows GetNetworkParams interface in iphlpapi.dll to */ 3630 /* figure out what our nameservers are. */ 3631 static int 3632 load_nameservers_with_getnetworkparams(struct evdns_base *base) 3633 { 3634 /* Based on MSDN examples and inspection of c-ares code. */ 3635 FIXED_INFO *fixed; 3636 HMODULE handle = 0; 3637 ULONG size = sizeof(FIXED_INFO); 3638 void *buf = NULL; 3639 int status = 0, r, added_any; 3640 IP_ADDR_STRING *ns; 3641 GetNetworkParams_fn_t fn; 3642 3643 ASSERT_LOCKED(base); 3644 if (!(handle = evutil_load_windows_system_library( 3645 TEXT("iphlpapi.dll")))) { 3646 log(EVDNS_LOG_WARN, "Could not open iphlpapi.dll"); 3647 status = -1; 3648 goto done; 3649 } 3650 if (!(fn = (GetNetworkParams_fn_t) GetProcAddress(handle, "GetNetworkParams"))) { 3651 log(EVDNS_LOG_WARN, "Could not get address of function."); 3652 status = -1; 3653 goto done; 3654 } 3655 3656 buf = mm_malloc(size); 3657 if (!buf) { status = 4; goto done; } 3658 fixed = buf; 3659 r = fn(fixed, &size); 3660 if (r != ERROR_SUCCESS && r != ERROR_BUFFER_OVERFLOW) { 3661 status = -1; 3662 goto done; 3663 } 3664 if (r != ERROR_SUCCESS) { 3665 mm_free(buf); 3666 buf = mm_malloc(size); 3667 if (!buf) { status = 4; goto done; } 3668 fixed = buf; 3669 r = fn(fixed, &size); 3670 if (r != ERROR_SUCCESS) { 3671 log(EVDNS_LOG_DEBUG, "fn() failed."); 3672 status = -1; 3673 goto done; 3674 } 3675 } 3676 3677 EVUTIL_ASSERT(fixed); 3678 added_any = 0; 3679 ns = &(fixed->DnsServerList); 3680 while (ns) { 3681 r = evdns_nameserver_ip_add_line(base, ns->IpAddress.String); 3682 if (r) { 3683 log(EVDNS_LOG_DEBUG,"Could not add nameserver %s to list,error: %d", 3684 (ns->IpAddress.String),(int)GetLastError()); 3685 status = r; 3686 } else { 3687 ++added_any; 3688 log(EVDNS_LOG_DEBUG,"Successfully added %s as nameserver",ns->IpAddress.String); 3689 } 3690 3691 ns = ns->Next; 3692 } 3693 3694 if (!added_any) { 3695 log(EVDNS_LOG_DEBUG, "No nameservers added."); 3696 if (status == 0) 3697 status = -1; 3698 } else { 3699 status = 0; 3700 } 3701 3702 done: 3703 if (buf) 3704 mm_free(buf); 3705 if (handle) 3706 FreeLibrary(handle); 3707 return status; 3708 } 3709 3710 static int 3711 config_nameserver_from_reg_key(struct evdns_base *base, HKEY key, const TCHAR *subkey) 3712 { 3713 char *buf; 3714 DWORD bufsz = 0, type = 0; 3715 int status = 0; 3716 3717 ASSERT_LOCKED(base); 3718 if (RegQueryValueEx(key, subkey, 0, &type, NULL, &bufsz) 3719 != ERROR_MORE_DATA) 3720 return -1; 3721 if (!(buf = mm_malloc(bufsz))) 3722 return -1; 3723 3724 if (RegQueryValueEx(key, subkey, 0, &type, (LPBYTE)buf, &bufsz) 3725 == ERROR_SUCCESS && bufsz > 1) { 3726 status = evdns_nameserver_ip_add_line(base,buf); 3727 } 3728 3729 mm_free(buf); 3730 return status; 3731 } 3732 3733 #define SERVICES_KEY TEXT("System\\CurrentControlSet\\Services\\") 3734 #define WIN_NS_9X_KEY SERVICES_KEY TEXT("VxD\\MSTCP") 3735 #define WIN_NS_NT_KEY SERVICES_KEY TEXT("Tcpip\\Parameters") 3736 3737 static int 3738 load_nameservers_from_registry(struct evdns_base *base) 3739 { 3740 int found = 0; 3741 int r; 3742 #define TRY(k, name) \ 3743 if (!found && config_nameserver_from_reg_key(base,k,TEXT(name)) == 0) { \ 3744 log(EVDNS_LOG_DEBUG,"Found nameservers in %s/%s",#k,name); \ 3745 found = 1; \ 3746 } else if (!found) { \ 3747 log(EVDNS_LOG_DEBUG,"Didn't find nameservers in %s/%s", \ 3748 #k,#name); \ 3749 } 3750 3751 ASSERT_LOCKED(base); 3752 3753 if (((int)GetVersion()) > 0) { /* NT */ 3754 HKEY nt_key = 0, interfaces_key = 0; 3755 3756 if (RegOpenKeyEx(HKEY_LOCAL_MACHINE, WIN_NS_NT_KEY, 0, 3757 KEY_READ, &nt_key) != ERROR_SUCCESS) { 3758 log(EVDNS_LOG_DEBUG,"Couldn't open nt key, %d",(int)GetLastError()); 3759 return -1; 3760 } 3761 r = RegOpenKeyEx(nt_key, TEXT("Interfaces"), 0, 3762 KEY_QUERY_VALUE|KEY_ENUMERATE_SUB_KEYS, 3763 &interfaces_key); 3764 if (r != ERROR_SUCCESS) { 3765 log(EVDNS_LOG_DEBUG,"Couldn't open interfaces key, %d",(int)GetLastError()); 3766 return -1; 3767 } 3768 TRY(nt_key, "NameServer"); 3769 TRY(nt_key, "DhcpNameServer"); 3770 TRY(interfaces_key, "NameServer"); 3771 TRY(interfaces_key, "DhcpNameServer"); 3772 RegCloseKey(interfaces_key); 3773 RegCloseKey(nt_key); 3774 } else { 3775 HKEY win_key = 0; 3776 if (RegOpenKeyEx(HKEY_LOCAL_MACHINE, WIN_NS_9X_KEY, 0, 3777 KEY_READ, &win_key) != ERROR_SUCCESS) { 3778 log(EVDNS_LOG_DEBUG, "Couldn't open registry key, %d", (int)GetLastError()); 3779 return -1; 3780 } 3781 TRY(win_key, "NameServer"); 3782 RegCloseKey(win_key); 3783 } 3784 3785 if (found == 0) { 3786 log(EVDNS_LOG_WARN,"Didn't find any nameservers."); 3787 } 3788 3789 return found ? 0 : -1; 3790 #undef TRY 3791 } 3792 3793 int 3794 evdns_base_config_windows_nameservers(struct evdns_base *base) 3795 { 3796 int r; 3797 char *fname; 3798 if (base == NULL) 3799 base = current_base; 3800 if (base == NULL) 3801 return -1; 3802 EVDNS_LOCK(base); 3803 if (load_nameservers_with_getnetworkparams(base) == 0) { 3804 EVDNS_UNLOCK(base); 3805 return 0; 3806 } 3807 r = load_nameservers_from_registry(base); 3808 3809 fname = evdns_get_default_hosts_filename(); 3810 evdns_base_load_hosts(base, fname); 3811 if (fname) 3812 mm_free(fname); 3813 3814 EVDNS_UNLOCK(base); 3815 return r; 3816 } 3817 3818 int 3819 evdns_config_windows_nameservers(void) 3820 { 3821 if (!current_base) { 3822 current_base = evdns_base_new(NULL, 1); 3823 return current_base == NULL ? -1 : 0; 3824 } else { 3825 return evdns_base_config_windows_nameservers(current_base); 3826 } 3827 } 3828 #endif 3829 3830 struct evdns_base * 3831 evdns_base_new(struct event_base *event_base, int initialize_nameservers) 3832 { 3833 struct evdns_base *base; 3834 3835 if (evutil_secure_rng_init() < 0) { 3836 log(EVDNS_LOG_WARN, "Unable to seed random number generator; " 3837 "DNS can't run."); 3838 return NULL; 3839 } 3840 3841 /* Give the evutil library a hook into its evdns-enabled 3842 * functionality. We can't just call evdns_getaddrinfo directly or 3843 * else libevent-core will depend on libevent-extras. */ 3844 evutil_set_evdns_getaddrinfo_fn(evdns_getaddrinfo); 3845 3846 base = mm_malloc(sizeof(struct evdns_base)); 3847 if (base == NULL) 3848 return (NULL); 3849 memset(base, 0, sizeof(struct evdns_base)); 3850 base->req_waiting_head = NULL; 3851 3852 EVTHREAD_ALLOC_LOCK(base->lock, EVTHREAD_LOCKTYPE_RECURSIVE); 3853 EVDNS_LOCK(base); 3854 3855 /* Set max requests inflight and allocate req_heads. */ 3856 base->req_heads = NULL; 3857 3858 evdns_base_set_max_requests_inflight(base, 64); 3859 3860 base->server_head = NULL; 3861 base->event_base = event_base; 3862 base->global_good_nameservers = base->global_requests_inflight = 3863 base->global_requests_waiting = 0; 3864 3865 base->global_timeout.tv_sec = 5; 3866 base->global_timeout.tv_usec = 0; 3867 base->global_max_reissues = 1; 3868 base->global_max_retransmits = 3; 3869 base->global_max_nameserver_timeout = 3; 3870 base->global_search_state = NULL; 3871 base->global_randomize_case = 1; 3872 base->global_getaddrinfo_allow_skew.tv_sec = 3; 3873 base->global_getaddrinfo_allow_skew.tv_usec = 0; 3874 base->global_nameserver_probe_initial_timeout.tv_sec = 10; 3875 base->global_nameserver_probe_initial_timeout.tv_usec = 0; 3876 3877 TAILQ_INIT(&base->hostsdb); 3878 3879 if (initialize_nameservers) { 3880 int r; 3881 #ifdef WIN32 3882 r = evdns_base_config_windows_nameservers(base); 3883 #else 3884 r = evdns_base_resolv_conf_parse(base, DNS_OPTIONS_ALL, "/etc/resolv.conf"); 3885 #endif 3886 if (r == -1) { 3887 evdns_base_free_and_unlock(base, 0); 3888 return NULL; 3889 } 3890 } 3891 EVDNS_UNLOCK(base); 3892 return base; 3893 } 3894 3895 int 3896 evdns_init(void) 3897 { 3898 struct evdns_base *base = evdns_base_new(NULL, 1); 3899 if (base) { 3900 current_base = base; 3901 return 0; 3902 } else { 3903 return -1; 3904 } 3905 } 3906 3907 const char * 3908 evdns_err_to_string(int err) 3909 { 3910 switch (err) { 3911 case DNS_ERR_NONE: return "no error"; 3912 case DNS_ERR_FORMAT: return "misformatted query"; 3913 case DNS_ERR_SERVERFAILED: return "server failed"; 3914 case DNS_ERR_NOTEXIST: return "name does not exist"; 3915 case DNS_ERR_NOTIMPL: return "query not implemented"; 3916 case DNS_ERR_REFUSED: return "refused"; 3917 3918 case DNS_ERR_TRUNCATED: return "reply truncated or ill-formed"; 3919 case DNS_ERR_UNKNOWN: return "unknown"; 3920 case DNS_ERR_TIMEOUT: return "request timed out"; 3921 case DNS_ERR_SHUTDOWN: return "dns subsystem shut down"; 3922 case DNS_ERR_CANCEL: return "dns request canceled"; 3923 case DNS_ERR_NODATA: return "no records in the reply"; 3924 default: return "[Unknown error code]"; 3925 } 3926 } 3927 3928 static void 3929 evdns_nameserver_free(struct nameserver *server) 3930 { 3931 if (server->socket >= 0) 3932 evutil_closesocket(server->socket); 3933 (void) event_del(&server->event); 3934 event_debug_unassign(&server->event); 3935 if (server->state == 0) 3936 (void) event_del(&server->timeout_event); 3937 event_debug_unassign(&server->timeout_event); 3938 mm_free(server); 3939 } 3940 3941 static void 3942 evdns_base_free_and_unlock(struct evdns_base *base, int fail_requests) 3943 { 3944 struct nameserver *server, *server_next; 3945 struct search_domain *dom, *dom_next; 3946 int i; 3947 3948 /* Requires that we hold the lock. */ 3949 3950 /* TODO(nickm) we might need to refcount here. */ 3951 3952 for (i = 0; i < base->n_req_heads; ++i) { 3953 while (base->req_heads[i]) { 3954 if (fail_requests) 3955 reply_schedule_callback(base->req_heads[i], 0, DNS_ERR_SHUTDOWN, NULL); 3956 request_finished(base->req_heads[i], &REQ_HEAD(base, base->req_heads[i]->trans_id), 1); 3957 } 3958 } 3959 while (base->req_waiting_head) { 3960 if (fail_requests) 3961 reply_schedule_callback(base->req_waiting_head, 0, DNS_ERR_SHUTDOWN, NULL); 3962 request_finished(base->req_waiting_head, &base->req_waiting_head, 1); 3963 } 3964 base->global_requests_inflight = base->global_requests_waiting = 0; 3965 3966 for (server = base->server_head; server; server = server_next) { 3967 server_next = server->next; 3968 evdns_nameserver_free(server); 3969 if (server_next == base->server_head) 3970 break; 3971 } 3972 base->server_head = NULL; 3973 base->global_good_nameservers = 0; 3974 3975 if (base->global_search_state) { 3976 for (dom = base->global_search_state->head; dom; dom = dom_next) { 3977 dom_next = dom->next; 3978 mm_free(dom); 3979 } 3980 mm_free(base->global_search_state); 3981 base->global_search_state = NULL; 3982 } 3983 3984 { 3985 struct hosts_entry *victim; 3986 while ((victim = TAILQ_FIRST(&base->hostsdb))) { 3987 TAILQ_REMOVE(&base->hostsdb, victim, next); 3988 mm_free(victim); 3989 } 3990 } 3991 3992 mm_free(base->req_heads); 3993 3994 EVDNS_UNLOCK(base); 3995 EVTHREAD_FREE_LOCK(base->lock, EVTHREAD_LOCKTYPE_RECURSIVE); 3996 3997 mm_free(base); 3998 } 3999 4000 void 4001 evdns_base_free(struct evdns_base *base, int fail_requests) 4002 { 4003 EVDNS_LOCK(base); 4004 evdns_base_free_and_unlock(base, fail_requests); 4005 } 4006 4007 void 4008 evdns_shutdown(int fail_requests) 4009 { 4010 if (current_base) { 4011 struct evdns_base *b = current_base; 4012 current_base = NULL; 4013 evdns_base_free(b, fail_requests); 4014 } 4015 evdns_log_fn = NULL; 4016 } 4017 4018 static int 4019 evdns_base_parse_hosts_line(struct evdns_base *base, char *line) 4020 { 4021 char *strtok_state; 4022 static const char *const delims = " \t"; 4023 char *const addr = strtok_r(line, delims, &strtok_state); 4024 char *hostname, *hash; 4025 struct sockaddr_storage ss; 4026 int socklen = sizeof(ss); 4027 ASSERT_LOCKED(base); 4028 4029 #define NEXT_TOKEN strtok_r(NULL, delims, &strtok_state) 4030 4031 if (!addr || *addr == '#') 4032 return 0; 4033 4034 memset(&ss, 0, sizeof(ss)); 4035 if (evutil_parse_sockaddr_port(addr, (struct sockaddr*)&ss, &socklen)<0) 4036 return -1; 4037 if (socklen > (int)sizeof(struct sockaddr_in6)) 4038 return -1; 4039 4040 if (sockaddr_getport((struct sockaddr*)&ss)) 4041 return -1; 4042 4043 while ((hostname = NEXT_TOKEN)) { 4044 struct hosts_entry *he; 4045 size_t namelen; 4046 if ((hash = strchr(hostname, '#'))) { 4047 if (hash == hostname) 4048 return 0; 4049 *hash = '\0'; 4050 } 4051 4052 namelen = strlen(hostname); 4053 4054 he = mm_calloc(1, sizeof(struct hosts_entry)+namelen); 4055 if (!he) 4056 return -1; 4057 EVUTIL_ASSERT(socklen <= (int)sizeof(he->addr)); 4058 memcpy(&he->addr, &ss, socklen); 4059 memcpy(he->hostname, hostname, namelen+1); 4060 he->addrlen = socklen; 4061 4062 TAILQ_INSERT_TAIL(&base->hostsdb, he, next); 4063 4064 if (hash) 4065 return 0; 4066 } 4067 4068 return 0; 4069 #undef NEXT_TOKEN 4070 } 4071 4072 static int 4073 evdns_base_load_hosts_impl(struct evdns_base *base, const char *hosts_fname) 4074 { 4075 char *str=NULL, *cp, *eol; 4076 size_t len; 4077 int err=0; 4078 4079 ASSERT_LOCKED(base); 4080 4081 if (hosts_fname == NULL || 4082 (err = evutil_read_file(hosts_fname, &str, &len, 0)) < 0) { 4083 char tmp[64]; 4084 strlcpy(tmp, "127.0.0.1 localhost", sizeof(tmp)); 4085 evdns_base_parse_hosts_line(base, tmp); 4086 strlcpy(tmp, "::1 localhost", sizeof(tmp)); 4087 evdns_base_parse_hosts_line(base, tmp); 4088 return err ? -1 : 0; 4089 } 4090 4091 /* This will break early if there is a NUL in the hosts file. 4092 * Probably not a problem.*/ 4093 cp = str; 4094 for (;;) { 4095 eol = strchr(cp, '\n'); 4096 4097 if (eol) { 4098 *eol = '\0'; 4099 evdns_base_parse_hosts_line(base, cp); 4100 cp = eol+1; 4101 } else { 4102 evdns_base_parse_hosts_line(base, cp); 4103 break; 4104 } 4105 } 4106 4107 mm_free(str); 4108 return 0; 4109 } 4110 4111 int 4112 evdns_base_load_hosts(struct evdns_base *base, const char *hosts_fname) 4113 { 4114 int res; 4115 if (!base) 4116 base = current_base; 4117 EVDNS_LOCK(base); 4118 res = evdns_base_load_hosts_impl(base, hosts_fname); 4119 EVDNS_UNLOCK(base); 4120 return res; 4121 } 4122 4123 /* A single request for a getaddrinfo, either v4 or v6. */ 4124 struct getaddrinfo_subrequest { 4125 struct evdns_request *r; 4126 ev_uint32_t type; 4127 }; 4128 4129 /* State data used to implement an in-progress getaddrinfo. */ 4130 struct evdns_getaddrinfo_request { 4131 struct evdns_base *evdns_base; 4132 /* Copy of the modified 'hints' data that we'll use to build 4133 * answers. */ 4134 struct evutil_addrinfo hints; 4135 /* The callback to invoke when we're done */ 4136 evdns_getaddrinfo_cb user_cb; 4137 /* User-supplied data to give to the callback. */ 4138 void *user_data; 4139 /* The port to use when building sockaddrs. */ 4140 ev_uint16_t port; 4141 /* The sub_request for an A record (if any) */ 4142 struct getaddrinfo_subrequest ipv4_request; 4143 /* The sub_request for an AAAA record (if any) */ 4144 struct getaddrinfo_subrequest ipv6_request; 4145 4146 /* The cname result that we were told (if any) */ 4147 char *cname_result; 4148 4149 /* If we have one request answered and one request still inflight, 4150 * then this field holds the answer from the first request... */ 4151 struct evutil_addrinfo *pending_result; 4152 /* And this event is a timeout that will tell us to cancel the second 4153 * request if it's taking a long time. */ 4154 struct event timeout; 4155 4156 /* And this field holds the error code from the first request... */ 4157 int pending_error; 4158 /* If this is set, the user canceled this request. */ 4159 unsigned user_canceled : 1; 4160 /* If this is set, the user can no longer cancel this request; we're 4161 * just waiting for the free. */ 4162 unsigned request_done : 1; 4163 }; 4164 4165 /* Convert an evdns errors to the equivalent getaddrinfo error. */ 4166 static int 4167 evdns_err_to_getaddrinfo_err(int e1) 4168 { 4169 /* XXX Do this better! */ 4170 if (e1 == DNS_ERR_NONE) 4171 return 0; 4172 else if (e1 == DNS_ERR_NOTEXIST) 4173 return EVUTIL_EAI_NONAME; 4174 else 4175 return EVUTIL_EAI_FAIL; 4176 } 4177 4178 /* Return the more informative of two getaddrinfo errors. */ 4179 static int 4180 getaddrinfo_merge_err(int e1, int e2) 4181 { 4182 /* XXXX be cleverer here. */ 4183 if (e1 == 0) 4184 return e2; 4185 else 4186 return e1; 4187 } 4188 4189 static void 4190 free_getaddrinfo_request(struct evdns_getaddrinfo_request *data) 4191 { 4192 /* DO NOT CALL this if either of the requests is pending. Only once 4193 * both callbacks have been invoked is it safe to free the request */ 4194 if (data->pending_result) 4195 evutil_freeaddrinfo(data->pending_result); 4196 if (data->cname_result) 4197 mm_free(data->cname_result); 4198 event_del(&data->timeout); 4199 mm_free(data); 4200 return; 4201 } 4202 4203 static void 4204 add_cname_to_reply(struct evdns_getaddrinfo_request *data, 4205 struct evutil_addrinfo *ai) 4206 { 4207 if (data->cname_result && ai) { 4208 ai->ai_canonname = data->cname_result; 4209 data->cname_result = NULL; 4210 } 4211 } 4212 4213 /* Callback: invoked when one request in a mixed-format A/AAAA getaddrinfo 4214 * request has finished, but the other one took too long to answer. Pass 4215 * along the answer we got, and cancel the other request. 4216 */ 4217 static void 4218 evdns_getaddrinfo_timeout_cb(evutil_socket_t fd, short what, void *ptr) 4219 { 4220 int v4_timedout = 0, v6_timedout = 0; 4221 struct evdns_getaddrinfo_request *data = ptr; 4222 4223 /* Cancel any pending requests, and note which one */ 4224 if (data->ipv4_request.r) { 4225 /* XXXX This does nothing if the request's callback is already 4226 * running (pending_cb is set). */ 4227 evdns_cancel_request(NULL, data->ipv4_request.r); 4228 v4_timedout = 1; 4229 EVDNS_LOCK(data->evdns_base); 4230 ++data->evdns_base->getaddrinfo_ipv4_timeouts; 4231 EVDNS_UNLOCK(data->evdns_base); 4232 } 4233 if (data->ipv6_request.r) { 4234 /* XXXX This does nothing if the request's callback is already 4235 * running (pending_cb is set). */ 4236 evdns_cancel_request(NULL, data->ipv6_request.r); 4237 v6_timedout = 1; 4238 EVDNS_LOCK(data->evdns_base); 4239 ++data->evdns_base->getaddrinfo_ipv6_timeouts; 4240 EVDNS_UNLOCK(data->evdns_base); 4241 } 4242 4243 /* We only use this timeout callback when we have an answer for 4244 * one address. */ 4245 EVUTIL_ASSERT(!v4_timedout || !v6_timedout); 4246 4247 /* Report the outcome of the other request that didn't time out. */ 4248 if (data->pending_result) { 4249 add_cname_to_reply(data, data->pending_result); 4250 data->user_cb(0, data->pending_result, data->user_data); 4251 data->pending_result = NULL; 4252 } else { 4253 int e = data->pending_error; 4254 if (!e) 4255 e = EVUTIL_EAI_AGAIN; 4256 data->user_cb(e, NULL, data->user_data); 4257 } 4258 4259 data->user_cb = NULL; /* prevent double-call if evdns callbacks are 4260 * in-progress. XXXX It would be better if this 4261 * weren't necessary. */ 4262 4263 if (!v4_timedout && !v6_timedout) { 4264 /* should be impossible? XXXX */ 4265 free_getaddrinfo_request(data); 4266 } 4267 } 4268 4269 static int 4270 evdns_getaddrinfo_set_timeout(struct evdns_base *evdns_base, 4271 struct evdns_getaddrinfo_request *data) 4272 { 4273 return event_add(&data->timeout, &evdns_base->global_getaddrinfo_allow_skew); 4274 } 4275 4276 static inline int 4277 evdns_result_is_answer(int result) 4278 { 4279 return (result != DNS_ERR_NOTIMPL && result != DNS_ERR_REFUSED && 4280 result != DNS_ERR_SERVERFAILED && result != DNS_ERR_CANCEL); 4281 } 4282 4283 static void 4284 evdns_getaddrinfo_gotresolve(int result, char type, int count, 4285 int ttl, void *addresses, void *arg) 4286 { 4287 int i; 4288 struct getaddrinfo_subrequest *req = arg; 4289 struct getaddrinfo_subrequest *other_req; 4290 struct evdns_getaddrinfo_request *data; 4291 4292 struct evutil_addrinfo *res; 4293 4294 struct sockaddr_in sin; 4295 struct sockaddr_in6 sin6; 4296 struct sockaddr *sa; 4297 int socklen, addrlen; 4298 void *addrp; 4299 int err; 4300 int user_canceled; 4301 4302 EVUTIL_ASSERT(req->type == DNS_IPv4_A || req->type == DNS_IPv6_AAAA); 4303 if (req->type == DNS_IPv4_A) { 4304 data = EVUTIL_UPCAST(req, struct evdns_getaddrinfo_request, ipv4_request); 4305 other_req = &data->ipv6_request; 4306 } else { 4307 data = EVUTIL_UPCAST(req, struct evdns_getaddrinfo_request, ipv6_request); 4308 other_req = &data->ipv4_request; 4309 } 4310 4311 EVDNS_LOCK(data->evdns_base); 4312 if (evdns_result_is_answer(result)) { 4313 if (req->type == DNS_IPv4_A) 4314 ++data->evdns_base->getaddrinfo_ipv4_answered; 4315 else 4316 ++data->evdns_base->getaddrinfo_ipv6_answered; 4317 } 4318 user_canceled = data->user_canceled; 4319 if (other_req->r == NULL) 4320 data->request_done = 1; 4321 EVDNS_UNLOCK(data->evdns_base); 4322 4323 req->r = NULL; 4324 4325 if (result == DNS_ERR_CANCEL && ! user_canceled) { 4326 /* Internal cancel request from timeout or internal error. 4327 * we already answered the user. */ 4328 if (other_req->r == NULL) 4329 free_getaddrinfo_request(data); 4330 return; 4331 } 4332 4333 if (data->user_cb == NULL) { 4334 /* We already answered. XXXX This shouldn't be needed; see 4335 * comments in evdns_getaddrinfo_timeout_cb */ 4336 free_getaddrinfo_request(data); 4337 return; 4338 } 4339 4340 if (result == DNS_ERR_NONE) { 4341 if (count == 0) 4342 err = EVUTIL_EAI_NODATA; 4343 else 4344 err = 0; 4345 } else { 4346 err = evdns_err_to_getaddrinfo_err(result); 4347 } 4348 4349 if (err) { 4350 /* Looks like we got an error. */ 4351 if (other_req->r) { 4352 /* The other request is still working; maybe it will 4353 * succeed. */ 4354 /* XXXX handle failure from set_timeout */ 4355 evdns_getaddrinfo_set_timeout(data->evdns_base, data); 4356 data->pending_error = err; 4357 return; 4358 } 4359 4360 if (user_canceled) { 4361 data->user_cb(EVUTIL_EAI_CANCEL, NULL, data->user_data); 4362 } else if (data->pending_result) { 4363 /* If we have an answer waiting, and we weren't 4364 * canceled, ignore this error. */ 4365 add_cname_to_reply(data, data->pending_result); 4366 data->user_cb(0, data->pending_result, data->user_data); 4367 data->pending_result = NULL; 4368 } else { 4369 if (data->pending_error) 4370 err = getaddrinfo_merge_err(err, 4371 data->pending_error); 4372 data->user_cb(err, NULL, data->user_data); 4373 } 4374 free_getaddrinfo_request(data); 4375 return; 4376 } else if (user_canceled) { 4377 if (other_req->r) { 4378 /* The other request is still working; let it hit this 4379 * callback with EVUTIL_EAI_CANCEL callback and report 4380 * the failure. */ 4381 return; 4382 } 4383 data->user_cb(EVUTIL_EAI_CANCEL, NULL, data->user_data); 4384 free_getaddrinfo_request(data); 4385 return; 4386 } 4387 4388 /* Looks like we got some answers. We should turn them into addrinfos 4389 * and then either queue those or return them all. */ 4390 EVUTIL_ASSERT(type == DNS_IPv4_A || type == DNS_IPv6_AAAA); 4391 4392 if (type == DNS_IPv4_A) { 4393 memset(&sin, 0, sizeof(sin)); 4394 sin.sin_family = AF_INET; 4395 sin.sin_port = htons(data->port); 4396 4397 sa = (struct sockaddr *)&sin; 4398 socklen = sizeof(sin); 4399 addrlen = 4; 4400 addrp = &sin.sin_addr.s_addr; 4401 } else { 4402 memset(&sin6, 0, sizeof(sin6)); 4403 sin6.sin6_family = AF_INET6; 4404 sin6.sin6_port = htons(data->port); 4405 4406 sa = (struct sockaddr *)&sin6; 4407 socklen = sizeof(sin6); 4408 addrlen = 16; 4409 addrp = &sin6.sin6_addr.s6_addr; 4410 } 4411 4412 res = NULL; 4413 for (i=0; i < count; ++i) { 4414 struct evutil_addrinfo *ai; 4415 memcpy(addrp, ((char*)addresses)+i*addrlen, addrlen); 4416 ai = evutil_new_addrinfo(sa, socklen, &data->hints); 4417 if (!ai) { 4418 if (other_req->r) { 4419 evdns_cancel_request(NULL, other_req->r); 4420 } 4421 data->user_cb(EVUTIL_EAI_MEMORY, NULL, data->user_data); 4422 if (res) 4423 evutil_freeaddrinfo(res); 4424 4425 if (other_req->r == NULL) 4426 free_getaddrinfo_request(data); 4427 return; 4428 } 4429 res = evutil_addrinfo_append(res, ai); 4430 } 4431 4432 if (other_req->r) { 4433 /* The other request is still in progress; wait for it */ 4434 /* XXXX handle failure from set_timeout */ 4435 evdns_getaddrinfo_set_timeout(data->evdns_base, data); 4436 data->pending_result = res; 4437 return; 4438 } else { 4439 /* The other request is done or never started; append its 4440 * results (if any) and return them. */ 4441 if (data->pending_result) { 4442 if (req->type == DNS_IPv4_A) 4443 res = evutil_addrinfo_append(res, 4444 data->pending_result); 4445 else 4446 res = evutil_addrinfo_append( 4447 data->pending_result, res); 4448 data->pending_result = NULL; 4449 } 4450 4451 /* Call the user callback. */ 4452 add_cname_to_reply(data, res); 4453 data->user_cb(0, res, data->user_data); 4454 4455 /* Free data. */ 4456 free_getaddrinfo_request(data); 4457 } 4458 } 4459 4460 static struct hosts_entry * 4461 find_hosts_entry(struct evdns_base *base, const char *hostname, 4462 struct hosts_entry *find_after) 4463 { 4464 struct hosts_entry *e; 4465 4466 if (find_after) 4467 e = TAILQ_NEXT(find_after, next); 4468 else 4469 e = TAILQ_FIRST(&base->hostsdb); 4470 4471 for (; e; e = TAILQ_NEXT(e, next)) { 4472 if (!evutil_ascii_strcasecmp(e->hostname, hostname)) 4473 return e; 4474 } 4475 return NULL; 4476 } 4477 4478 static int 4479 evdns_getaddrinfo_fromhosts(struct evdns_base *base, 4480 const char *nodename, struct evutil_addrinfo *hints, ev_uint16_t port, 4481 struct evutil_addrinfo **res) 4482 { 4483 int n_found = 0; 4484 struct hosts_entry *e; 4485 struct evutil_addrinfo *ai=NULL; 4486 int f = hints->ai_family; 4487 4488 EVDNS_LOCK(base); 4489 for (e = find_hosts_entry(base, nodename, NULL); e; 4490 e = find_hosts_entry(base, nodename, e)) { 4491 struct evutil_addrinfo *ai_new; 4492 ++n_found; 4493 if ((e->addr.sa.sa_family == AF_INET && f == PF_INET6) || 4494 (e->addr.sa.sa_family == AF_INET6 && f == PF_INET)) 4495 continue; 4496 ai_new = evutil_new_addrinfo(&e->addr.sa, e->addrlen, hints); 4497 if (!ai_new) { 4498 n_found = 0; 4499 goto out; 4500 } 4501 sockaddr_setport(ai_new->ai_addr, port); 4502 ai = evutil_addrinfo_append(ai, ai_new); 4503 } 4504 EVDNS_UNLOCK(base); 4505 out: 4506 if (n_found) { 4507 /* Note that we return an empty answer if we found entries for 4508 * this hostname but none were of the right address type. */ 4509 *res = ai; 4510 return 0; 4511 } else { 4512 if (ai) 4513 evutil_freeaddrinfo(ai); 4514 return -1; 4515 } 4516 } 4517 4518 struct evdns_getaddrinfo_request * 4519 evdns_getaddrinfo(struct evdns_base *dns_base, 4520 const char *nodename, const char *servname, 4521 const struct evutil_addrinfo *hints_in, 4522 evdns_getaddrinfo_cb cb, void *arg) 4523 { 4524 struct evdns_getaddrinfo_request *data; 4525 struct evutil_addrinfo hints; 4526 struct evutil_addrinfo *res = NULL; 4527 int err; 4528 int port = 0; 4529 int want_cname = 0; 4530 4531 if (!dns_base) { 4532 dns_base = current_base; 4533 if (!dns_base) { 4534 log(EVDNS_LOG_WARN, 4535 "Call to getaddrinfo_async with no " 4536 "evdns_base configured."); 4537 cb(EVUTIL_EAI_FAIL, NULL, arg); /* ??? better error? */ 4538 return NULL; 4539 } 4540 } 4541 4542 /* If we _must_ answer this immediately, do so. */ 4543 if ((hints_in && (hints_in->ai_flags & EVUTIL_AI_NUMERICHOST))) { 4544 res = NULL; 4545 err = evutil_getaddrinfo(nodename, servname, hints_in, &res); 4546 cb(err, res, arg); 4547 return NULL; 4548 } 4549 4550 if (hints_in) { 4551 memcpy(&hints, hints_in, sizeof(hints)); 4552 } else { 4553 memset(&hints, 0, sizeof(hints)); 4554 hints.ai_family = PF_UNSPEC; 4555 } 4556 4557 evutil_adjust_hints_for_addrconfig(&hints); 4558 4559 /* Now try to see if we _can_ answer immediately. */ 4560 /* (It would be nice to do this by calling getaddrinfo directly, with 4561 * AI_NUMERICHOST, on plaforms that have it, but we can't: there isn't 4562 * a reliable way to distinguish the "that wasn't a numeric host!" case 4563 * from any other EAI_NONAME cases.) */ 4564 err = evutil_getaddrinfo_common(nodename, servname, &hints, &res, &port); 4565 if (err != EVUTIL_EAI_NEED_RESOLVE) { 4566 cb(err, res, arg); 4567 return NULL; 4568 } 4569 4570 /* If there is an entry in the hosts file, we should give it now. */ 4571 if (!evdns_getaddrinfo_fromhosts(dns_base, nodename, &hints, port, &res)) { 4572 cb(0, res, arg); 4573 return NULL; 4574 } 4575 4576 /* Okay, things are serious now. We're going to need to actually 4577 * launch a request. 4578 */ 4579 data = mm_calloc(1,sizeof(struct evdns_getaddrinfo_request)); 4580 if (!data) { 4581 cb(EVUTIL_EAI_MEMORY, NULL, arg); 4582 return NULL; 4583 } 4584 4585 memcpy(&data->hints, &hints, sizeof(data->hints)); 4586 data->port = (ev_uint16_t)port; 4587 data->ipv4_request.type = DNS_IPv4_A; 4588 data->ipv6_request.type = DNS_IPv6_AAAA; 4589 data->user_cb = cb; 4590 data->user_data = arg; 4591 data->evdns_base = dns_base; 4592 4593 want_cname = (hints.ai_flags & EVUTIL_AI_CANONNAME); 4594 4595 /* If we are asked for a PF_UNSPEC address, we launch two requests in 4596 * parallel: one for an A address and one for an AAAA address. We 4597 * can't send just one request, since many servers only answer one 4598 * question per DNS request. 4599 * 4600 * Once we have the answer to one request, we allow for a short 4601 * timeout before we report it, to see if the other one arrives. If 4602 * they both show up in time, then we report both the answers. 4603 * 4604 * If too many addresses of one type time out or fail, we should stop 4605 * launching those requests. (XXX we don't do that yet.) 4606 */ 4607 4608 if (hints.ai_family != PF_INET6) { 4609 log(EVDNS_LOG_DEBUG, "Sending request for %s on ipv4 as %p", 4610 nodename, &data->ipv4_request); 4611 4612 data->ipv4_request.r = evdns_base_resolve_ipv4(dns_base, 4613 nodename, 0, evdns_getaddrinfo_gotresolve, 4614 &data->ipv4_request); 4615 if (want_cname) 4616 data->ipv4_request.r->current_req->put_cname_in_ptr = 4617 &data->cname_result; 4618 } 4619 if (hints.ai_family != PF_INET) { 4620 log(EVDNS_LOG_DEBUG, "Sending request for %s on ipv6 as %p", 4621 nodename, &data->ipv6_request); 4622 4623 data->ipv6_request.r = evdns_base_resolve_ipv6(dns_base, 4624 nodename, 0, evdns_getaddrinfo_gotresolve, 4625 &data->ipv6_request); 4626 if (want_cname) 4627 data->ipv6_request.r->current_req->put_cname_in_ptr = 4628 &data->cname_result; 4629 } 4630 4631 evtimer_assign(&data->timeout, dns_base->event_base, 4632 evdns_getaddrinfo_timeout_cb, data); 4633 4634 if (data->ipv4_request.r || data->ipv6_request.r) { 4635 return data; 4636 } else { 4637 mm_free(data); 4638 cb(EVUTIL_EAI_FAIL, NULL, arg); 4639 return NULL; 4640 } 4641 } 4642 4643 void 4644 evdns_getaddrinfo_cancel(struct evdns_getaddrinfo_request *data) 4645 { 4646 EVDNS_LOCK(data->evdns_base); 4647 if (data->request_done) { 4648 EVDNS_UNLOCK(data->evdns_base); 4649 return; 4650 } 4651 event_del(&data->timeout); 4652 data->user_canceled = 1; 4653 if (data->ipv4_request.r) 4654 evdns_cancel_request(data->evdns_base, data->ipv4_request.r); 4655 if (data->ipv6_request.r) 4656 evdns_cancel_request(data->evdns_base, data->ipv6_request.r); 4657 EVDNS_UNLOCK(data->evdns_base); 4658 } 4659