1 /* $NetBSD: evdns.c,v 1.1.1.1 2013/12/27 23:31:26 christos Exp $ */ 2 3 /* Copyright 2006-2007 Niels Provos 4 * Copyright 2007-2012 Nick Mathewson and Niels Provos 5 * 6 * Redistribution and use in source and binary forms, with or without 7 * modification, are permitted provided that the following conditions 8 * are met: 9 * 1. Redistributions of source code must retain the above copyright 10 * notice, this list of conditions and the following disclaimer. 11 * 2. Redistributions in binary form must reproduce the above copyright 12 * notice, this list of conditions and the following disclaimer in the 13 * documentation and/or other materials provided with the distribution. 14 * 3. The name of the author may not be used to endorse or promote products 15 * derived from this software without specific prior written permission. 16 * 17 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 18 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 19 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 20 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 21 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 22 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 23 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 24 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 26 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 27 */ 28 29 /* Based on software by Adam Langly. Adam's original message: 30 * 31 * Async DNS Library 32 * Adam Langley <agl@imperialviolet.org> 33 * http://www.imperialviolet.org/eventdns.html 34 * Public Domain code 35 * 36 * This software is Public Domain. To view a copy of the public domain dedication, 37 * visit http://creativecommons.org/licenses/publicdomain/ or send a letter to 38 * Creative Commons, 559 Nathan Abbott Way, Stanford, California 94305, USA. 39 * 40 * I ask and expect, but do not require, that all derivative works contain an 41 * attribution similar to: 42 * Parts developed by Adam Langley <agl@imperialviolet.org> 43 * 44 * You may wish to replace the word "Parts" with something else depending on 45 * the amount of original code. 46 * 47 * (Derivative works does not include programs which link against, run or include 48 * the source verbatim in their source distributions) 49 * 50 * Version: 0.1b 51 */ 52 53 #include "event2/event-config.h" 54 #include "evconfig-private.h" 55 56 #include <sys/types.h> 57 58 #ifndef _FORTIFY_SOURCE 59 #define _FORTIFY_SOURCE 3 60 #endif 61 62 #include <string.h> 63 #include <fcntl.h> 64 #ifdef EVENT__HAVE_SYS_TIME_H 65 #include <sys/time.h> 66 #endif 67 #ifdef EVENT__HAVE_STDINT_H 68 #include <stdint.h> 69 #endif 70 #include <stdlib.h> 71 #include <string.h> 72 #include <errno.h> 73 #ifdef EVENT__HAVE_UNISTD_H 74 #include <unistd.h> 75 #endif 76 #include <limits.h> 77 #include <sys/stat.h> 78 #include <stdio.h> 79 #include <stdarg.h> 80 #ifdef _WIN32 81 #include <winsock2.h> 82 #include <ws2tcpip.h> 83 #ifndef _WIN32_IE 84 #define _WIN32_IE 0x400 85 #endif 86 #include <shlobj.h> 87 #endif 88 89 #include "event2/dns.h" 90 #include "event2/dns_struct.h" 91 #include "event2/dns_compat.h" 92 #include "event2/util.h" 93 #include "event2/event.h" 94 #include "event2/event_struct.h" 95 #include "event2/thread.h" 96 97 #include "event2/bufferevent.h" 98 #include "event2/bufferevent_struct.h" 99 #include "bufferevent-internal.h" 100 101 #include "defer-internal.h" 102 #include "log-internal.h" 103 #include "mm-internal.h" 104 #include "strlcpy-internal.h" 105 #include "ipv6-internal.h" 106 #include "util-internal.h" 107 #include "evthread-internal.h" 108 #ifdef _WIN32 109 #include <ctype.h> 110 #include <winsock2.h> 111 #include <windows.h> 112 #include <iphlpapi.h> 113 #include <io.h> 114 #else 115 #include <sys/socket.h> 116 #include <netinet/in.h> 117 #include <arpa/inet.h> 118 #endif 119 120 #ifdef EVENT__HAVE_NETINET_IN6_H 121 #include <netinet/in6.h> 122 #endif 123 124 #define EVDNS_LOG_DEBUG 0 125 #define EVDNS_LOG_WARN 1 126 #define EVDNS_LOG_MSG 2 127 128 #ifndef HOST_NAME_MAX 129 #define HOST_NAME_MAX 255 130 #endif 131 132 #include <stdio.h> 133 134 #undef MIN 135 #define MIN(a,b) ((a)<(b)?(a):(b)) 136 137 #define ASSERT_VALID_REQUEST(req) \ 138 EVUTIL_ASSERT((req)->handle && (req)->handle->current_req == (req)) 139 140 #define u64 ev_uint64_t 141 #define u32 ev_uint32_t 142 #define u16 ev_uint16_t 143 #define u8 ev_uint8_t 144 145 /* maximum number of addresses from a single packet */ 146 /* that we bother recording */ 147 #define MAX_V4_ADDRS 32 148 #define MAX_V6_ADDRS 32 149 150 151 #define TYPE_A EVDNS_TYPE_A 152 #define TYPE_CNAME 5 153 #define TYPE_PTR EVDNS_TYPE_PTR 154 #define TYPE_SOA EVDNS_TYPE_SOA 155 #define TYPE_AAAA EVDNS_TYPE_AAAA 156 157 #define CLASS_INET EVDNS_CLASS_INET 158 159 /* Persistent handle. We keep this separate from 'struct request' since we 160 * need some object to last for as long as an evdns_request is outstanding so 161 * that it can be canceled, whereas a search request can lead to multiple 162 * 'struct request' instances being created over its lifetime. */ 163 struct evdns_request { 164 struct request *current_req; 165 struct evdns_base *base; 166 167 int pending_cb; /* Waiting for its callback to be invoked; not 168 * owned by event base any more. */ 169 170 /* elements used by the searching code */ 171 int search_index; 172 struct search_state *search_state; 173 char *search_origname; /* needs to be free()ed */ 174 int search_flags; 175 }; 176 177 struct request { 178 u8 *request; /* the dns packet data */ 179 u8 request_type; /* TYPE_PTR or TYPE_A or TYPE_AAAA */ 180 unsigned int request_len; 181 int reissue_count; 182 int tx_count; /* the number of times that this packet has been sent */ 183 void *user_pointer; /* the pointer given to us for this request */ 184 evdns_callback_type user_callback; 185 struct nameserver *ns; /* the server which we last sent it */ 186 187 /* these objects are kept in a circular list */ 188 /* XXX We could turn this into a CIRCLEQ. */ 189 struct request *next, *prev; 190 191 struct event timeout_event; 192 193 u16 trans_id; /* the transaction id */ 194 unsigned request_appended :1; /* true if the request pointer is data which follows this struct */ 195 unsigned transmit_me :1; /* needs to be transmitted */ 196 197 /* XXXX This is a horrible hack. */ 198 char **put_cname_in_ptr; /* store the cname here if we get one. */ 199 200 struct evdns_base *base; 201 202 struct evdns_request *handle; 203 }; 204 205 struct reply { 206 unsigned int type; 207 unsigned int have_answer : 1; 208 union { 209 struct { 210 u32 addrcount; 211 u32 addresses[MAX_V4_ADDRS]; 212 } a; 213 struct { 214 u32 addrcount; 215 struct in6_addr addresses[MAX_V6_ADDRS]; 216 } aaaa; 217 struct { 218 char name[HOST_NAME_MAX]; 219 } ptr; 220 } data; 221 }; 222 223 struct nameserver { 224 evutil_socket_t socket; /* a connected UDP socket */ 225 struct sockaddr_storage address; 226 ev_socklen_t addrlen; 227 int failed_times; /* number of times which we have given this server a chance */ 228 int timedout; /* number of times in a row a request has timed out */ 229 struct event event; 230 /* these objects are kept in a circular list */ 231 struct nameserver *next, *prev; 232 struct event timeout_event; /* used to keep the timeout for */ 233 /* when we next probe this server. */ 234 /* Valid if state == 0 */ 235 /* Outstanding probe request for this nameserver, if any */ 236 struct evdns_request *probe_request; 237 char state; /* zero if we think that this server is down */ 238 char choked; /* true if we have an EAGAIN from this server's socket */ 239 char write_waiting; /* true if we are waiting for EV_WRITE events */ 240 struct evdns_base *base; 241 }; 242 243 244 /* Represents a local port where we're listening for DNS requests. Right now, */ 245 /* only UDP is supported. */ 246 struct evdns_server_port { 247 evutil_socket_t socket; /* socket we use to read queries and write replies. */ 248 int refcnt; /* reference count. */ 249 char choked; /* Are we currently blocked from writing? */ 250 char closing; /* Are we trying to close this port, pending writes? */ 251 evdns_request_callback_fn_type user_callback; /* Fn to handle requests */ 252 void *user_data; /* Opaque pointer passed to user_callback */ 253 struct event event; /* Read/write event */ 254 /* circular list of replies that we want to write. */ 255 struct server_request *pending_replies; 256 struct event_base *event_base; 257 258 #ifndef EVENT__DISABLE_THREAD_SUPPORT 259 void *lock; 260 #endif 261 }; 262 263 /* Represents part of a reply being built. (That is, a single RR.) */ 264 struct server_reply_item { 265 struct server_reply_item *next; /* next item in sequence. */ 266 char *name; /* name part of the RR */ 267 u16 type; /* The RR type */ 268 u16 class; /* The RR class (usually CLASS_INET) */ 269 u32 ttl; /* The RR TTL */ 270 char is_name; /* True iff data is a label */ 271 u16 datalen; /* Length of data; -1 if data is a label */ 272 void *data; /* The contents of the RR */ 273 }; 274 275 /* Represents a request that we've received as a DNS server, and holds */ 276 /* the components of the reply as we're constructing it. */ 277 struct server_request { 278 /* Pointers to the next and previous entries on the list of replies */ 279 /* that we're waiting to write. Only set if we have tried to respond */ 280 /* and gotten EAGAIN. */ 281 struct server_request *next_pending; 282 struct server_request *prev_pending; 283 284 u16 trans_id; /* Transaction id. */ 285 struct evdns_server_port *port; /* Which port received this request on? */ 286 struct sockaddr_storage addr; /* Where to send the response */ 287 ev_socklen_t addrlen; /* length of addr */ 288 289 int n_answer; /* how many answer RRs have been set? */ 290 int n_authority; /* how many authority RRs have been set? */ 291 int n_additional; /* how many additional RRs have been set? */ 292 293 struct server_reply_item *answer; /* linked list of answer RRs */ 294 struct server_reply_item *authority; /* linked list of authority RRs */ 295 struct server_reply_item *additional; /* linked list of additional RRs */ 296 297 /* Constructed response. Only set once we're ready to send a reply. */ 298 /* Once this is set, the RR fields are cleared, and no more should be set. */ 299 char *response; 300 size_t response_len; 301 302 /* Caller-visible fields: flags, questions. */ 303 struct evdns_server_request base; 304 }; 305 306 struct evdns_base { 307 /* An array of n_req_heads circular lists for inflight requests. 308 * Each inflight request req is in req_heads[req->trans_id % n_req_heads]. 309 */ 310 struct request **req_heads; 311 /* A circular list of requests that we're waiting to send, but haven't 312 * sent yet because there are too many requests inflight */ 313 struct request *req_waiting_head; 314 /* A circular list of nameservers. */ 315 struct nameserver *server_head; 316 int n_req_heads; 317 318 struct event_base *event_base; 319 320 /* The number of good nameservers that we have */ 321 int global_good_nameservers; 322 323 /* inflight requests are contained in the req_head list */ 324 /* and are actually going out across the network */ 325 int global_requests_inflight; 326 /* requests which aren't inflight are in the waiting list */ 327 /* and are counted here */ 328 int global_requests_waiting; 329 330 int global_max_requests_inflight; 331 332 struct timeval global_timeout; /* 5 seconds by default */ 333 int global_max_reissues; /* a reissue occurs when we get some errors from the server */ 334 int global_max_retransmits; /* number of times we'll retransmit a request which timed out */ 335 /* number of timeouts in a row before we consider this server to be down */ 336 int global_max_nameserver_timeout; 337 /* true iff we will use the 0x20 hack to prevent poisoning attacks. */ 338 int global_randomize_case; 339 340 /* The first time that a nameserver fails, how long do we wait before 341 * probing to see if it has returned? */ 342 struct timeval global_nameserver_probe_initial_timeout; 343 344 /** Port to bind to for outgoing DNS packets. */ 345 struct sockaddr_storage global_outgoing_address; 346 /** ev_socklen_t for global_outgoing_address. 0 if it isn't set. */ 347 ev_socklen_t global_outgoing_addrlen; 348 349 struct timeval global_getaddrinfo_allow_skew; 350 351 int getaddrinfo_ipv4_timeouts; 352 int getaddrinfo_ipv6_timeouts; 353 int getaddrinfo_ipv4_answered; 354 int getaddrinfo_ipv6_answered; 355 356 struct search_state *global_search_state; 357 358 TAILQ_HEAD(hosts_list, hosts_entry) hostsdb; 359 360 #ifndef EVENT__DISABLE_THREAD_SUPPORT 361 void *lock; 362 #endif 363 }; 364 365 struct hosts_entry { 366 TAILQ_ENTRY(hosts_entry) next; 367 union { 368 struct sockaddr sa; 369 struct sockaddr_in sin; 370 struct sockaddr_in6 sin6; 371 } addr; 372 int addrlen; 373 char hostname[1]; 374 }; 375 376 static struct evdns_base *current_base = NULL; 377 378 struct evdns_base * 379 evdns_get_global_base(void) 380 { 381 return current_base; 382 } 383 384 /* Given a pointer to an evdns_server_request, get the corresponding */ 385 /* server_request. */ 386 #define TO_SERVER_REQUEST(base_ptr) \ 387 ((struct server_request*) \ 388 (((char*)(base_ptr) - evutil_offsetof(struct server_request, base)))) 389 390 #define REQ_HEAD(base, id) ((base)->req_heads[id % (base)->n_req_heads]) 391 392 static struct nameserver *nameserver_pick(struct evdns_base *base); 393 static void evdns_request_insert(struct request *req, struct request **head); 394 static void evdns_request_remove(struct request *req, struct request **head); 395 static void nameserver_ready_callback(evutil_socket_t fd, short events, void *arg); 396 static int evdns_transmit(struct evdns_base *base); 397 static int evdns_request_transmit(struct request *req); 398 static void nameserver_send_probe(struct nameserver *const ns); 399 static void search_request_finished(struct evdns_request *const); 400 static int search_try_next(struct evdns_request *const req); 401 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); 402 static void evdns_requests_pump_waiting_queue(struct evdns_base *base); 403 static u16 transaction_id_pick(struct evdns_base *base); 404 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); 405 static void request_submit(struct request *const req); 406 407 static int server_request_free(struct server_request *req); 408 static void server_request_free_answers(struct server_request *req); 409 static void server_port_free(struct evdns_server_port *port); 410 static void server_port_ready_callback(evutil_socket_t fd, short events, void *arg); 411 static int evdns_base_resolv_conf_parse_impl(struct evdns_base *base, int flags, const char *const filename); 412 static int evdns_base_set_option_impl(struct evdns_base *base, 413 const char *option, const char *val, int flags); 414 static void evdns_base_free_and_unlock(struct evdns_base *base, int fail_requests); 415 416 static int strtoint(const char *const str); 417 418 #ifdef EVENT__DISABLE_THREAD_SUPPORT 419 #define EVDNS_LOCK(base) EVUTIL_NIL_STMT_ 420 #define EVDNS_UNLOCK(base) EVUTIL_NIL_STMT_ 421 #define ASSERT_LOCKED(base) EVUTIL_NIL_STMT_ 422 #else 423 #define EVDNS_LOCK(base) \ 424 EVLOCK_LOCK((base)->lock, 0) 425 #define EVDNS_UNLOCK(base) \ 426 EVLOCK_UNLOCK((base)->lock, 0) 427 #define ASSERT_LOCKED(base) \ 428 EVLOCK_ASSERT_LOCKED((base)->lock) 429 #endif 430 431 static void 432 default_evdns_log_fn(int warning, const char *buf) 433 { 434 if (warning == EVDNS_LOG_WARN) 435 event_warnx("[evdns] %s", buf); 436 else if (warning == EVDNS_LOG_MSG) 437 event_msgx("[evdns] %s", buf); 438 else 439 event_debug(("[evdns] %s", buf)); 440 } 441 442 static evdns_debug_log_fn_type evdns_log_fn = NULL; 443 444 void 445 evdns_set_log_fn(evdns_debug_log_fn_type fn) 446 { 447 evdns_log_fn = fn; 448 } 449 450 #ifdef __GNUC__ 451 #define EVDNS_LOG_CHECK __attribute__ ((format(printf, 2, 3))) 452 #else 453 #define EVDNS_LOG_CHECK 454 #endif 455 456 static void evdns_log_(int warn, const char *fmt, ...) EVDNS_LOG_CHECK; 457 static void 458 evdns_log_(int warn, const char *fmt, ...) 459 { 460 va_list args; 461 char buf[512]; 462 if (!evdns_log_fn) 463 return; 464 va_start(args,fmt); 465 evutil_vsnprintf(buf, sizeof(buf), fmt, args); 466 va_end(args); 467 if (evdns_log_fn) { 468 if (warn == EVDNS_LOG_MSG) 469 warn = EVDNS_LOG_WARN; 470 evdns_log_fn(warn, buf); 471 } else { 472 default_evdns_log_fn(warn, buf); 473 } 474 475 } 476 477 #define log evdns_log_ 478 479 /* This walks the list of inflight requests to find the */ 480 /* one with a matching transaction id. Returns NULL on */ 481 /* failure */ 482 static struct request * 483 request_find_from_trans_id(struct evdns_base *base, u16 trans_id) { 484 struct request *req = REQ_HEAD(base, trans_id); 485 struct request *const started_at = req; 486 487 ASSERT_LOCKED(base); 488 489 if (req) { 490 do { 491 if (req->trans_id == trans_id) return req; 492 req = req->next; 493 } while (req != started_at); 494 } 495 496 return NULL; 497 } 498 499 /* a libevent callback function which is called when a nameserver */ 500 /* has gone down and we want to test if it has came back to life yet */ 501 static void 502 nameserver_prod_callback(evutil_socket_t fd, short events, void *arg) { 503 struct nameserver *const ns = (struct nameserver *) arg; 504 (void)fd; 505 (void)events; 506 507 EVDNS_LOCK(ns->base); 508 nameserver_send_probe(ns); 509 EVDNS_UNLOCK(ns->base); 510 } 511 512 /* a libevent callback which is called when a nameserver probe (to see if */ 513 /* it has come back to life) times out. We increment the count of failed_times */ 514 /* and wait longer to send the next probe packet. */ 515 static void 516 nameserver_probe_failed(struct nameserver *const ns) { 517 struct timeval timeout; 518 int i; 519 520 ASSERT_LOCKED(ns->base); 521 (void) evtimer_del(&ns->timeout_event); 522 if (ns->state == 1) { 523 /* This can happen if the nameserver acts in a way which makes us mark */ 524 /* it as bad and then starts sending good replies. */ 525 return; 526 } 527 528 #define MAX_PROBE_TIMEOUT 3600 529 #define TIMEOUT_BACKOFF_FACTOR 3 530 531 memcpy(&timeout, &ns->base->global_nameserver_probe_initial_timeout, 532 sizeof(struct timeval)); 533 for (i=ns->failed_times; i > 0 && timeout.tv_sec < MAX_PROBE_TIMEOUT; --i) { 534 timeout.tv_sec *= TIMEOUT_BACKOFF_FACTOR; 535 timeout.tv_usec *= TIMEOUT_BACKOFF_FACTOR; 536 if (timeout.tv_usec > 1000000) { 537 timeout.tv_sec += timeout.tv_usec / 1000000; 538 timeout.tv_usec %= 1000000; 539 } 540 } 541 if (timeout.tv_sec > MAX_PROBE_TIMEOUT) { 542 timeout.tv_sec = MAX_PROBE_TIMEOUT; 543 timeout.tv_usec = 0; 544 } 545 546 ns->failed_times++; 547 548 if (evtimer_add(&ns->timeout_event, &timeout) < 0) { 549 char addrbuf[128]; 550 log(EVDNS_LOG_WARN, 551 "Error from libevent when adding timer event for %s", 552 evutil_format_sockaddr_port_( 553 (struct sockaddr *)&ns->address, 554 addrbuf, sizeof(addrbuf))); 555 } 556 } 557 558 /* called when a nameserver has been deemed to have failed. For example, too */ 559 /* many packets have timed out etc */ 560 static void 561 nameserver_failed(struct nameserver *const ns, const char *msg) { 562 struct request *req, *started_at; 563 struct evdns_base *base = ns->base; 564 int i; 565 char addrbuf[128]; 566 567 ASSERT_LOCKED(base); 568 /* if this nameserver has already been marked as failed */ 569 /* then don't do anything */ 570 if (!ns->state) return; 571 572 log(EVDNS_LOG_MSG, "Nameserver %s has failed: %s", 573 evutil_format_sockaddr_port_( 574 (struct sockaddr *)&ns->address, 575 addrbuf, sizeof(addrbuf)), 576 msg); 577 578 base->global_good_nameservers--; 579 EVUTIL_ASSERT(base->global_good_nameservers >= 0); 580 if (base->global_good_nameservers == 0) { 581 log(EVDNS_LOG_MSG, "All nameservers have failed"); 582 } 583 584 ns->state = 0; 585 ns->failed_times = 1; 586 587 if (evtimer_add(&ns->timeout_event, 588 &base->global_nameserver_probe_initial_timeout) < 0) { 589 log(EVDNS_LOG_WARN, 590 "Error from libevent when adding timer event for %s", 591 evutil_format_sockaddr_port_( 592 (struct sockaddr *)&ns->address, 593 addrbuf, sizeof(addrbuf))); 594 /* ???? Do more? */ 595 } 596 597 /* walk the list of inflight requests to see if any can be reassigned to */ 598 /* a different server. Requests in the waiting queue don't have a */ 599 /* nameserver assigned yet */ 600 601 /* if we don't have *any* good nameservers then there's no point */ 602 /* trying to reassign requests to one */ 603 if (!base->global_good_nameservers) return; 604 605 for (i = 0; i < base->n_req_heads; ++i) { 606 req = started_at = base->req_heads[i]; 607 if (req) { 608 do { 609 if (req->tx_count == 0 && req->ns == ns) { 610 /* still waiting to go out, can be moved */ 611 /* to another server */ 612 req->ns = nameserver_pick(base); 613 } 614 req = req->next; 615 } while (req != started_at); 616 } 617 } 618 } 619 620 static void 621 nameserver_up(struct nameserver *const ns) 622 { 623 char addrbuf[128]; 624 ASSERT_LOCKED(ns->base); 625 if (ns->state) return; 626 log(EVDNS_LOG_MSG, "Nameserver %s is back up", 627 evutil_format_sockaddr_port_( 628 (struct sockaddr *)&ns->address, 629 addrbuf, sizeof(addrbuf))); 630 evtimer_del(&ns->timeout_event); 631 if (ns->probe_request) { 632 evdns_cancel_request(ns->base, ns->probe_request); 633 ns->probe_request = NULL; 634 } 635 ns->state = 1; 636 ns->failed_times = 0; 637 ns->timedout = 0; 638 ns->base->global_good_nameservers++; 639 } 640 641 static void 642 request_trans_id_set(struct request *const req, const u16 trans_id) { 643 req->trans_id = trans_id; 644 *((u16 *) req->request) = htons(trans_id); 645 } 646 647 /* Called to remove a request from a list and dealloc it. */ 648 /* head is a pointer to the head of the list it should be */ 649 /* removed from or NULL if the request isn't in a list. */ 650 /* when free_handle is one, free the handle as well. */ 651 static void 652 request_finished(struct request *const req, struct request **head, int free_handle) { 653 struct evdns_base *base = req->base; 654 int was_inflight = (head != &base->req_waiting_head); 655 EVDNS_LOCK(base); 656 ASSERT_VALID_REQUEST(req); 657 658 if (head) 659 evdns_request_remove(req, head); 660 661 log(EVDNS_LOG_DEBUG, "Removing timeout for request %p", req); 662 if (was_inflight) { 663 evtimer_del(&req->timeout_event); 664 base->global_requests_inflight--; 665 } else { 666 base->global_requests_waiting--; 667 } 668 /* it was initialized during request_new / evtimer_assign */ 669 event_debug_unassign(&req->timeout_event); 670 671 if (!req->request_appended) { 672 /* need to free the request data on it's own */ 673 mm_free(req->request); 674 } else { 675 /* the request data is appended onto the header */ 676 /* so everything gets free()ed when we: */ 677 } 678 679 if (req->handle) { 680 EVUTIL_ASSERT(req->handle->current_req == req); 681 682 if (free_handle) { 683 search_request_finished(req->handle); 684 req->handle->current_req = NULL; 685 if (! req->handle->pending_cb) { 686 /* If we're planning to run the callback, 687 * don't free the handle until later. */ 688 mm_free(req->handle); 689 } 690 req->handle = NULL; /* If we have a bug, let's crash 691 * early */ 692 } else { 693 req->handle->current_req = NULL; 694 } 695 } 696 697 mm_free(req); 698 699 evdns_requests_pump_waiting_queue(base); 700 EVDNS_UNLOCK(base); 701 } 702 703 /* This is called when a server returns a funny error code. */ 704 /* We try the request again with another server. */ 705 /* */ 706 /* return: */ 707 /* 0 ok */ 708 /* 1 failed/reissue is pointless */ 709 static int 710 request_reissue(struct request *req) { 711 const struct nameserver *const last_ns = req->ns; 712 ASSERT_LOCKED(req->base); 713 ASSERT_VALID_REQUEST(req); 714 /* the last nameserver should have been marked as failing */ 715 /* by the caller of this function, therefore pick will try */ 716 /* not to return it */ 717 req->ns = nameserver_pick(req->base); 718 if (req->ns == last_ns) { 719 /* ... but pick did return it */ 720 /* not a lot of point in trying again with the */ 721 /* same server */ 722 return 1; 723 } 724 725 req->reissue_count++; 726 req->tx_count = 0; 727 req->transmit_me = 1; 728 729 return 0; 730 } 731 732 /* this function looks for space on the inflight queue and promotes */ 733 /* requests from the waiting queue if it can. */ 734 static void 735 evdns_requests_pump_waiting_queue(struct evdns_base *base) { 736 ASSERT_LOCKED(base); 737 while (base->global_requests_inflight < base->global_max_requests_inflight && 738 base->global_requests_waiting) { 739 struct request *req; 740 /* move a request from the waiting queue to the inflight queue */ 741 EVUTIL_ASSERT(base->req_waiting_head); 742 req = base->req_waiting_head; 743 evdns_request_remove(req, &base->req_waiting_head); 744 745 base->global_requests_waiting--; 746 base->global_requests_inflight++; 747 748 req->ns = nameserver_pick(base); 749 request_trans_id_set(req, transaction_id_pick(base)); 750 751 evdns_request_insert(req, &REQ_HEAD(base, req->trans_id)); 752 evdns_request_transmit(req); 753 evdns_transmit(base); 754 } 755 } 756 757 /* TODO(nickm) document */ 758 struct deferred_reply_callback { 759 struct event_callback deferred; 760 struct evdns_request *handle; 761 u8 request_type; 762 u8 have_reply; 763 u32 ttl; 764 u32 err; 765 evdns_callback_type user_callback; 766 struct reply reply; 767 }; 768 769 static void 770 reply_run_callback(struct event_callback *d, void *user_pointer) 771 { 772 struct deferred_reply_callback *cb = 773 EVUTIL_UPCAST(d, struct deferred_reply_callback, deferred); 774 775 switch (cb->request_type) { 776 case TYPE_A: 777 if (cb->have_reply) 778 cb->user_callback(DNS_ERR_NONE, DNS_IPv4_A, 779 cb->reply.data.a.addrcount, cb->ttl, 780 cb->reply.data.a.addresses, 781 user_pointer); 782 else 783 cb->user_callback(cb->err, 0, 0, cb->ttl, NULL, user_pointer); 784 break; 785 case TYPE_PTR: 786 if (cb->have_reply) { 787 char *name = cb->reply.data.ptr.name; 788 cb->user_callback(DNS_ERR_NONE, DNS_PTR, 1, cb->ttl, 789 &name, user_pointer); 790 } else { 791 cb->user_callback(cb->err, 0, 0, cb->ttl, NULL, user_pointer); 792 } 793 break; 794 case TYPE_AAAA: 795 if (cb->have_reply) 796 cb->user_callback(DNS_ERR_NONE, DNS_IPv6_AAAA, 797 cb->reply.data.aaaa.addrcount, cb->ttl, 798 cb->reply.data.aaaa.addresses, 799 user_pointer); 800 else 801 cb->user_callback(cb->err, 0, 0, cb->ttl, NULL, user_pointer); 802 break; 803 default: 804 EVUTIL_ASSERT(0); 805 } 806 807 if (cb->handle && cb->handle->pending_cb) { 808 mm_free(cb->handle); 809 } 810 811 mm_free(cb); 812 } 813 814 static void 815 reply_schedule_callback(struct request *const req, u32 ttl, u32 err, struct reply *reply) 816 { 817 struct deferred_reply_callback *d = mm_calloc(1, sizeof(*d)); 818 819 if (!d) { 820 event_warn("%s: Couldn't allocate space for deferred callback.", 821 __func__); 822 return; 823 } 824 825 ASSERT_LOCKED(req->base); 826 827 d->request_type = req->request_type; 828 d->user_callback = req->user_callback; 829 d->ttl = ttl; 830 d->err = err; 831 if (reply) { 832 d->have_reply = 1; 833 memcpy(&d->reply, reply, sizeof(struct reply)); 834 } 835 836 if (req->handle) { 837 req->handle->pending_cb = 1; 838 d->handle = req->handle; 839 } 840 841 event_deferred_cb_init_( 842 &d->deferred, 843 event_get_priority(&req->timeout_event), 844 reply_run_callback, 845 req->user_pointer); 846 event_deferred_cb_schedule_( 847 req->base->event_base, 848 &d->deferred); 849 } 850 851 /* this processes a parsed reply packet */ 852 static void 853 reply_handle(struct request *const req, u16 flags, u32 ttl, struct reply *reply) { 854 int error; 855 char addrbuf[128]; 856 static const int error_codes[] = { 857 DNS_ERR_FORMAT, DNS_ERR_SERVERFAILED, DNS_ERR_NOTEXIST, 858 DNS_ERR_NOTIMPL, DNS_ERR_REFUSED 859 }; 860 861 ASSERT_LOCKED(req->base); 862 ASSERT_VALID_REQUEST(req); 863 864 if (flags & 0x020f || !reply || !reply->have_answer) { 865 /* there was an error */ 866 if (flags & 0x0200) { 867 error = DNS_ERR_TRUNCATED; 868 } else if (flags & 0x000f) { 869 u16 error_code = (flags & 0x000f) - 1; 870 if (error_code > 4) { 871 error = DNS_ERR_UNKNOWN; 872 } else { 873 error = error_codes[error_code]; 874 } 875 } else if (reply && !reply->have_answer) { 876 error = DNS_ERR_NODATA; 877 } else { 878 error = DNS_ERR_UNKNOWN; 879 } 880 881 switch (error) { 882 case DNS_ERR_NOTIMPL: 883 case DNS_ERR_REFUSED: 884 /* we regard these errors as marking a bad nameserver */ 885 if (req->reissue_count < req->base->global_max_reissues) { 886 char msg[64]; 887 evutil_snprintf(msg, sizeof(msg), "Bad response %d (%s)", 888 error, evdns_err_to_string(error)); 889 nameserver_failed(req->ns, msg); 890 if (!request_reissue(req)) return; 891 } 892 break; 893 case DNS_ERR_SERVERFAILED: 894 /* rcode 2 (servfailed) sometimes means "we 895 * are broken" and sometimes (with some binds) 896 * means "that request was very confusing." 897 * Treat this as a timeout, not a failure. 898 */ 899 log(EVDNS_LOG_DEBUG, "Got a SERVERFAILED from nameserver" 900 "at %s; will allow the request to time out.", 901 evutil_format_sockaddr_port_( 902 (struct sockaddr *)&req->ns->address, 903 addrbuf, sizeof(addrbuf))); 904 break; 905 default: 906 /* we got a good reply from the nameserver: it is up. */ 907 if (req->handle == req->ns->probe_request) { 908 /* Avoid double-free */ 909 req->ns->probe_request = NULL; 910 } 911 912 nameserver_up(req->ns); 913 } 914 915 if (req->handle->search_state && 916 req->request_type != TYPE_PTR) { 917 /* if we have a list of domains to search in, 918 * try the next one */ 919 if (!search_try_next(req->handle)) { 920 /* a new request was issued so this 921 * request is finished and */ 922 /* the user callback will be made when 923 * that request (or a */ 924 /* child of it) finishes. */ 925 return; 926 } 927 } 928 929 /* all else failed. Pass the failure up */ 930 reply_schedule_callback(req, ttl, error, NULL); 931 request_finished(req, &REQ_HEAD(req->base, req->trans_id), 1); 932 } else { 933 /* all ok, tell the user */ 934 reply_schedule_callback(req, ttl, 0, reply); 935 if (req->handle == req->ns->probe_request) 936 req->ns->probe_request = NULL; /* Avoid double-free */ 937 nameserver_up(req->ns); 938 request_finished(req, &REQ_HEAD(req->base, req->trans_id), 1); 939 } 940 } 941 942 static int 943 name_parse(u8 *packet, int length, int *idx, char *name_out, int name_out_len) { 944 int name_end = -1; 945 int j = *idx; 946 int ptr_count = 0; 947 #define GET32(x) do { if (j + 4 > length) goto err; memcpy(&t32_, packet + j, 4); j += 4; x = ntohl(t32_); } while (0) 948 #define GET16(x) do { if (j + 2 > length) goto err; memcpy(&t_, packet + j, 2); j += 2; x = ntohs(t_); } while (0) 949 #define GET8(x) do { if (j >= length) goto err; x = packet[j++]; } while (0) 950 951 char *cp = name_out; 952 const char *const end = name_out + name_out_len; 953 954 /* Normally, names are a series of length prefixed strings terminated */ 955 /* with a length of 0 (the lengths are u8's < 63). */ 956 /* However, the length can start with a pair of 1 bits and that */ 957 /* means that the next 14 bits are a pointer within the current */ 958 /* packet. */ 959 960 for (;;) { 961 u8 label_len; 962 if (j >= length) return -1; 963 GET8(label_len); 964 if (!label_len) break; 965 if (label_len & 0xc0) { 966 u8 ptr_low; 967 GET8(ptr_low); 968 if (name_end < 0) name_end = j; 969 j = (((int)label_len & 0x3f) << 8) + ptr_low; 970 /* Make sure that the target offset is in-bounds. */ 971 if (j < 0 || j >= length) return -1; 972 /* If we've jumped more times than there are characters in the 973 * message, we must have a loop. */ 974 if (++ptr_count > length) return -1; 975 continue; 976 } 977 if (label_len > 63) return -1; 978 if (cp != name_out) { 979 if (cp + 1 >= end) return -1; 980 *cp++ = '.'; 981 } 982 if (cp + label_len >= end) return -1; 983 memcpy(cp, packet + j, label_len); 984 cp += label_len; 985 j += label_len; 986 } 987 if (cp >= end) return -1; 988 *cp = '\0'; 989 if (name_end < 0) 990 *idx = j; 991 else 992 *idx = name_end; 993 return 0; 994 err: 995 return -1; 996 } 997 998 /* parses a raw request from a nameserver */ 999 static int 1000 reply_parse(struct evdns_base *base, u8 *packet, int length) { 1001 int j = 0, k = 0; /* index into packet */ 1002 u16 t_; /* used by the macros */ 1003 u32 t32_; /* used by the macros */ 1004 char tmp_name[256], cmp_name[256]; /* used by the macros */ 1005 int name_matches = 0; 1006 1007 u16 trans_id, questions, answers, authority, additional, datalength; 1008 u16 flags = 0; 1009 u32 ttl, ttl_r = 0xffffffff; 1010 struct reply reply; 1011 struct request *req = NULL; 1012 unsigned int i; 1013 1014 ASSERT_LOCKED(base); 1015 1016 GET16(trans_id); 1017 GET16(flags); 1018 GET16(questions); 1019 GET16(answers); 1020 GET16(authority); 1021 GET16(additional); 1022 (void) authority; /* suppress "unused variable" warnings. */ 1023 (void) additional; /* suppress "unused variable" warnings. */ 1024 1025 req = request_find_from_trans_id(base, trans_id); 1026 if (!req) return -1; 1027 EVUTIL_ASSERT(req->base == base); 1028 1029 memset(&reply, 0, sizeof(reply)); 1030 1031 /* If it's not an answer, it doesn't correspond to any request. */ 1032 if (!(flags & 0x8000)) return -1; /* must be an answer */ 1033 if ((flags & 0x020f) && (flags & 0x020f) != DNS_ERR_NOTEXIST) { 1034 /* there was an error and it's not NXDOMAIN */ 1035 goto err; 1036 } 1037 /* if (!answers) return; */ /* must have an answer of some form */ 1038 1039 /* This macro skips a name in the DNS reply. */ 1040 #define SKIP_NAME \ 1041 do { tmp_name[0] = '\0'; \ 1042 if (name_parse(packet, length, &j, tmp_name, \ 1043 sizeof(tmp_name))<0) \ 1044 goto err; \ 1045 } while (0) 1046 #define TEST_NAME \ 1047 do { tmp_name[0] = '\0'; \ 1048 cmp_name[0] = '\0'; \ 1049 k = j; \ 1050 if (name_parse(packet, length, &j, tmp_name, \ 1051 sizeof(tmp_name))<0) \ 1052 goto err; \ 1053 if (name_parse(req->request, req->request_len, &k, \ 1054 cmp_name, sizeof(cmp_name))<0) \ 1055 goto err; \ 1056 if (base->global_randomize_case) { \ 1057 if (strcmp(tmp_name, cmp_name) == 0) \ 1058 name_matches = 1; \ 1059 } else { \ 1060 if (evutil_ascii_strcasecmp(tmp_name, cmp_name) == 0) \ 1061 name_matches = 1; \ 1062 } \ 1063 } while (0) 1064 1065 reply.type = req->request_type; 1066 1067 /* skip over each question in the reply */ 1068 for (i = 0; i < questions; ++i) { 1069 /* the question looks like 1070 * <label:name><u16:type><u16:class> 1071 */ 1072 TEST_NAME; 1073 j += 4; 1074 if (j > length) goto err; 1075 } 1076 1077 if (!name_matches) 1078 goto err; 1079 1080 /* now we have the answer section which looks like 1081 * <label:name><u16:type><u16:class><u32:ttl><u16:len><data...> 1082 */ 1083 1084 for (i = 0; i < answers; ++i) { 1085 u16 type, class; 1086 1087 SKIP_NAME; 1088 GET16(type); 1089 GET16(class); 1090 GET32(ttl); 1091 GET16(datalength); 1092 1093 if (type == TYPE_A && class == CLASS_INET) { 1094 int addrcount, addrtocopy; 1095 if (req->request_type != TYPE_A) { 1096 j += datalength; continue; 1097 } 1098 if ((datalength & 3) != 0) /* not an even number of As. */ 1099 goto err; 1100 addrcount = datalength >> 2; 1101 addrtocopy = MIN(MAX_V4_ADDRS - reply.data.a.addrcount, (unsigned)addrcount); 1102 1103 ttl_r = MIN(ttl_r, ttl); 1104 /* we only bother with the first four addresses. */ 1105 if (j + 4*addrtocopy > length) goto err; 1106 memcpy(&reply.data.a.addresses[reply.data.a.addrcount], 1107 packet + j, 4*addrtocopy); 1108 j += 4*addrtocopy; 1109 reply.data.a.addrcount += addrtocopy; 1110 reply.have_answer = 1; 1111 if (reply.data.a.addrcount == MAX_V4_ADDRS) break; 1112 } else if (type == TYPE_PTR && class == CLASS_INET) { 1113 if (req->request_type != TYPE_PTR) { 1114 j += datalength; continue; 1115 } 1116 if (name_parse(packet, length, &j, reply.data.ptr.name, 1117 sizeof(reply.data.ptr.name))<0) 1118 goto err; 1119 ttl_r = MIN(ttl_r, ttl); 1120 reply.have_answer = 1; 1121 break; 1122 } else if (type == TYPE_CNAME) { 1123 char cname[HOST_NAME_MAX]; 1124 if (!req->put_cname_in_ptr || *req->put_cname_in_ptr) { 1125 j += datalength; continue; 1126 } 1127 if (name_parse(packet, length, &j, cname, 1128 sizeof(cname))<0) 1129 goto err; 1130 *req->put_cname_in_ptr = mm_strdup(cname); 1131 } else if (type == TYPE_AAAA && class == CLASS_INET) { 1132 int addrcount, addrtocopy; 1133 if (req->request_type != TYPE_AAAA) { 1134 j += datalength; continue; 1135 } 1136 if ((datalength & 15) != 0) /* not an even number of AAAAs. */ 1137 goto err; 1138 addrcount = datalength >> 4; /* each address is 16 bytes long */ 1139 addrtocopy = MIN(MAX_V6_ADDRS - reply.data.aaaa.addrcount, (unsigned)addrcount); 1140 ttl_r = MIN(ttl_r, ttl); 1141 1142 /* we only bother with the first four addresses. */ 1143 if (j + 16*addrtocopy > length) goto err; 1144 memcpy(&reply.data.aaaa.addresses[reply.data.aaaa.addrcount], 1145 packet + j, 16*addrtocopy); 1146 reply.data.aaaa.addrcount += addrtocopy; 1147 j += 16*addrtocopy; 1148 reply.have_answer = 1; 1149 if (reply.data.aaaa.addrcount == MAX_V6_ADDRS) break; 1150 } else { 1151 /* skip over any other type of resource */ 1152 j += datalength; 1153 } 1154 } 1155 1156 if (!reply.have_answer) { 1157 for (i = 0; i < authority; ++i) { 1158 u16 type, class; 1159 SKIP_NAME; 1160 GET16(type); 1161 GET16(class); 1162 GET32(ttl); 1163 GET16(datalength); 1164 if (type == TYPE_SOA && class == CLASS_INET) { 1165 u32 serial, refresh, retry, expire, minimum; 1166 SKIP_NAME; 1167 SKIP_NAME; 1168 GET32(serial); 1169 GET32(refresh); 1170 GET32(retry); 1171 GET32(expire); 1172 GET32(minimum); 1173 (void)expire; 1174 (void)retry; 1175 (void)refresh; 1176 (void)serial; 1177 ttl_r = MIN(ttl_r, ttl); 1178 ttl_r = MIN(ttl_r, minimum); 1179 } else { 1180 /* skip over any other type of resource */ 1181 j += datalength; 1182 } 1183 } 1184 } 1185 1186 if (ttl_r == 0xffffffff) 1187 ttl_r = 0; 1188 1189 reply_handle(req, flags, ttl_r, &reply); 1190 return 0; 1191 err: 1192 if (req) 1193 reply_handle(req, flags, 0, NULL); 1194 return -1; 1195 } 1196 1197 /* Parse a raw request (packet,length) sent to a nameserver port (port) from */ 1198 /* a DNS client (addr,addrlen), and if it's well-formed, call the corresponding */ 1199 /* callback. */ 1200 static int 1201 request_parse(u8 *packet, int length, struct evdns_server_port *port, struct sockaddr *addr, ev_socklen_t addrlen) 1202 { 1203 int j = 0; /* index into packet */ 1204 u16 t_; /* used by the macros */ 1205 char tmp_name[256]; /* used by the macros */ 1206 1207 int i; 1208 u16 trans_id, flags, questions, answers, authority, additional; 1209 struct server_request *server_req = NULL; 1210 1211 ASSERT_LOCKED(port); 1212 1213 /* Get the header fields */ 1214 GET16(trans_id); 1215 GET16(flags); 1216 GET16(questions); 1217 GET16(answers); 1218 GET16(authority); 1219 GET16(additional); 1220 (void)answers; 1221 (void)additional; 1222 (void)authority; 1223 1224 if (flags & 0x8000) return -1; /* Must not be an answer. */ 1225 flags &= 0x0110; /* Only RD and CD get preserved. */ 1226 1227 server_req = mm_malloc(sizeof(struct server_request)); 1228 if (server_req == NULL) return -1; 1229 memset(server_req, 0, sizeof(struct server_request)); 1230 1231 server_req->trans_id = trans_id; 1232 memcpy(&server_req->addr, addr, addrlen); 1233 server_req->addrlen = addrlen; 1234 1235 server_req->base.flags = flags; 1236 server_req->base.nquestions = 0; 1237 server_req->base.questions = mm_calloc(sizeof(struct evdns_server_question *), questions); 1238 if (server_req->base.questions == NULL) 1239 goto err; 1240 1241 for (i = 0; i < questions; ++i) { 1242 u16 type, class; 1243 struct evdns_server_question *q; 1244 int namelen; 1245 if (name_parse(packet, length, &j, tmp_name, sizeof(tmp_name))<0) 1246 goto err; 1247 GET16(type); 1248 GET16(class); 1249 namelen = (int)strlen(tmp_name); 1250 q = mm_malloc(sizeof(struct evdns_server_question) + namelen); 1251 if (!q) 1252 goto err; 1253 q->type = type; 1254 q->dns_question_class = class; 1255 memcpy(q->name, tmp_name, namelen+1); 1256 server_req->base.questions[server_req->base.nquestions++] = q; 1257 } 1258 1259 /* Ignore answers, authority, and additional. */ 1260 1261 server_req->port = port; 1262 port->refcnt++; 1263 1264 /* Only standard queries are supported. */ 1265 if (flags & 0x7800) { 1266 evdns_server_request_respond(&(server_req->base), DNS_ERR_NOTIMPL); 1267 return -1; 1268 } 1269 1270 port->user_callback(&(server_req->base), port->user_data); 1271 1272 return 0; 1273 err: 1274 if (server_req) { 1275 if (server_req->base.questions) { 1276 for (i = 0; i < server_req->base.nquestions; ++i) 1277 mm_free(server_req->base.questions[i]); 1278 mm_free(server_req->base.questions); 1279 } 1280 mm_free(server_req); 1281 } 1282 return -1; 1283 1284 #undef SKIP_NAME 1285 #undef GET32 1286 #undef GET16 1287 #undef GET8 1288 } 1289 1290 1291 void 1292 evdns_set_transaction_id_fn(ev_uint16_t (*fn)(void)) 1293 { 1294 } 1295 1296 void 1297 evdns_set_random_bytes_fn(void (*fn)(char *, size_t)) 1298 { 1299 } 1300 1301 /* Try to choose a strong transaction id which isn't already in flight */ 1302 static u16 1303 transaction_id_pick(struct evdns_base *base) { 1304 ASSERT_LOCKED(base); 1305 for (;;) { 1306 u16 trans_id; 1307 evutil_secure_rng_get_bytes(&trans_id, sizeof(trans_id)); 1308 1309 if (trans_id == 0xffff) continue; 1310 /* now check to see if that id is already inflight */ 1311 if (request_find_from_trans_id(base, trans_id) == NULL) 1312 return trans_id; 1313 } 1314 } 1315 1316 /* choose a namesever to use. This function will try to ignore */ 1317 /* nameservers which we think are down and load balance across the rest */ 1318 /* by updating the server_head global each time. */ 1319 static struct nameserver * 1320 nameserver_pick(struct evdns_base *base) { 1321 struct nameserver *started_at = base->server_head, *picked; 1322 ASSERT_LOCKED(base); 1323 if (!base->server_head) return NULL; 1324 1325 /* if we don't have any good nameservers then there's no */ 1326 /* point in trying to find one. */ 1327 if (!base->global_good_nameservers) { 1328 base->server_head = base->server_head->next; 1329 return base->server_head; 1330 } 1331 1332 /* remember that nameservers are in a circular list */ 1333 for (;;) { 1334 if (base->server_head->state) { 1335 /* we think this server is currently good */ 1336 picked = base->server_head; 1337 base->server_head = base->server_head->next; 1338 return picked; 1339 } 1340 1341 base->server_head = base->server_head->next; 1342 if (base->server_head == started_at) { 1343 /* all the nameservers seem to be down */ 1344 /* so we just return this one and hope for the */ 1345 /* best */ 1346 EVUTIL_ASSERT(base->global_good_nameservers == 0); 1347 picked = base->server_head; 1348 base->server_head = base->server_head->next; 1349 return picked; 1350 } 1351 } 1352 } 1353 1354 /* this is called when a namesever socket is ready for reading */ 1355 static void 1356 nameserver_read(struct nameserver *ns) { 1357 struct sockaddr_storage ss; 1358 ev_socklen_t addrlen = sizeof(ss); 1359 u8 packet[1500]; 1360 char addrbuf[128]; 1361 ASSERT_LOCKED(ns->base); 1362 1363 for (;;) { 1364 const int r = recvfrom(ns->socket, (void*)packet, 1365 sizeof(packet), 0, 1366 (struct sockaddr*)&ss, &addrlen); 1367 if (r < 0) { 1368 int err = evutil_socket_geterror(ns->socket); 1369 if (EVUTIL_ERR_RW_RETRIABLE(err)) 1370 return; 1371 nameserver_failed(ns, 1372 evutil_socket_error_to_string(err)); 1373 return; 1374 } 1375 if (evutil_sockaddr_cmp((struct sockaddr*)&ss, 1376 (struct sockaddr*)&ns->address, 0)) { 1377 log(EVDNS_LOG_WARN, "Address mismatch on received " 1378 "DNS packet. Apparent source was %s", 1379 evutil_format_sockaddr_port_( 1380 (struct sockaddr *)&ss, 1381 addrbuf, sizeof(addrbuf))); 1382 return; 1383 } 1384 1385 ns->timedout = 0; 1386 reply_parse(ns->base, packet, r); 1387 } 1388 } 1389 1390 /* Read a packet from a DNS client on a server port s, parse it, and */ 1391 /* act accordingly. */ 1392 static void 1393 server_port_read(struct evdns_server_port *s) { 1394 u8 packet[1500]; 1395 struct sockaddr_storage addr; 1396 ev_socklen_t addrlen; 1397 int r; 1398 ASSERT_LOCKED(s); 1399 1400 for (;;) { 1401 addrlen = sizeof(struct sockaddr_storage); 1402 r = recvfrom(s->socket, (void*)packet, sizeof(packet), 0, 1403 (struct sockaddr*) &addr, &addrlen); 1404 if (r < 0) { 1405 int err = evutil_socket_geterror(s->socket); 1406 if (EVUTIL_ERR_RW_RETRIABLE(err)) 1407 return; 1408 log(EVDNS_LOG_WARN, 1409 "Error %s (%d) while reading request.", 1410 evutil_socket_error_to_string(err), err); 1411 return; 1412 } 1413 request_parse(packet, r, s, (struct sockaddr*) &addr, addrlen); 1414 } 1415 } 1416 1417 /* Try to write all pending replies on a given DNS server port. */ 1418 static void 1419 server_port_flush(struct evdns_server_port *port) 1420 { 1421 struct server_request *req = port->pending_replies; 1422 ASSERT_LOCKED(port); 1423 while (req) { 1424 int r = sendto(port->socket, req->response, (int)req->response_len, 0, 1425 (struct sockaddr*) &req->addr, (ev_socklen_t)req->addrlen); 1426 if (r < 0) { 1427 int err = evutil_socket_geterror(port->socket); 1428 if (EVUTIL_ERR_RW_RETRIABLE(err)) 1429 return; 1430 log(EVDNS_LOG_WARN, "Error %s (%d) while writing response to port; dropping", evutil_socket_error_to_string(err), err); 1431 } 1432 if (server_request_free(req)) { 1433 /* we released the last reference to req->port. */ 1434 return; 1435 } else { 1436 EVUTIL_ASSERT(req != port->pending_replies); 1437 req = port->pending_replies; 1438 } 1439 } 1440 1441 /* We have no more pending requests; stop listening for 'writeable' events. */ 1442 (void) event_del(&port->event); 1443 event_assign(&port->event, port->event_base, 1444 port->socket, EV_READ | EV_PERSIST, 1445 server_port_ready_callback, port); 1446 1447 if (event_add(&port->event, NULL) < 0) { 1448 log(EVDNS_LOG_WARN, "Error from libevent when adding event for DNS server."); 1449 /* ???? Do more? */ 1450 } 1451 } 1452 1453 /* set if we are waiting for the ability to write to this server. */ 1454 /* if waiting is true then we ask libevent for EV_WRITE events, otherwise */ 1455 /* we stop these events. */ 1456 static void 1457 nameserver_write_waiting(struct nameserver *ns, char waiting) { 1458 ASSERT_LOCKED(ns->base); 1459 if (ns->write_waiting == waiting) return; 1460 1461 ns->write_waiting = waiting; 1462 (void) event_del(&ns->event); 1463 event_assign(&ns->event, ns->base->event_base, 1464 ns->socket, EV_READ | (waiting ? EV_WRITE : 0) | EV_PERSIST, 1465 nameserver_ready_callback, ns); 1466 if (event_add(&ns->event, NULL) < 0) { 1467 char addrbuf[128]; 1468 log(EVDNS_LOG_WARN, "Error from libevent when adding event for %s", 1469 evutil_format_sockaddr_port_( 1470 (struct sockaddr *)&ns->address, 1471 addrbuf, sizeof(addrbuf))); 1472 /* ???? Do more? */ 1473 } 1474 } 1475 1476 /* a callback function. Called by libevent when the kernel says that */ 1477 /* a nameserver socket is ready for writing or reading */ 1478 static void 1479 nameserver_ready_callback(evutil_socket_t fd, short events, void *arg) { 1480 struct nameserver *ns = (struct nameserver *) arg; 1481 (void)fd; 1482 1483 EVDNS_LOCK(ns->base); 1484 if (events & EV_WRITE) { 1485 ns->choked = 0; 1486 if (!evdns_transmit(ns->base)) { 1487 nameserver_write_waiting(ns, 0); 1488 } 1489 } 1490 if (events & EV_READ) { 1491 nameserver_read(ns); 1492 } 1493 EVDNS_UNLOCK(ns->base); 1494 } 1495 1496 /* a callback function. Called by libevent when the kernel says that */ 1497 /* a server socket is ready for writing or reading. */ 1498 static void 1499 server_port_ready_callback(evutil_socket_t fd, short events, void *arg) { 1500 struct evdns_server_port *port = (struct evdns_server_port *) arg; 1501 (void) fd; 1502 1503 EVDNS_LOCK(port); 1504 if (events & EV_WRITE) { 1505 port->choked = 0; 1506 server_port_flush(port); 1507 } 1508 if (events & EV_READ) { 1509 server_port_read(port); 1510 } 1511 EVDNS_UNLOCK(port); 1512 } 1513 1514 /* This is an inefficient representation; only use it via the dnslabel_table_* 1515 * functions, so that is can be safely replaced with something smarter later. */ 1516 #define MAX_LABELS 128 1517 /* Structures used to implement name compression */ 1518 struct dnslabel_entry { char *v; off_t pos; }; 1519 struct dnslabel_table { 1520 int n_labels; /* number of current entries */ 1521 /* map from name to position in message */ 1522 struct dnslabel_entry labels[MAX_LABELS]; 1523 }; 1524 1525 /* Initialize dnslabel_table. */ 1526 static void 1527 dnslabel_table_init(struct dnslabel_table *table) 1528 { 1529 table->n_labels = 0; 1530 } 1531 1532 /* Free all storage held by table, but not the table itself. */ 1533 static void 1534 dnslabel_clear(struct dnslabel_table *table) 1535 { 1536 int i; 1537 for (i = 0; i < table->n_labels; ++i) 1538 mm_free(table->labels[i].v); 1539 table->n_labels = 0; 1540 } 1541 1542 /* return the position of the label in the current message, or -1 if the label */ 1543 /* hasn't been used yet. */ 1544 static int 1545 dnslabel_table_get_pos(const struct dnslabel_table *table, const char *label) 1546 { 1547 int i; 1548 for (i = 0; i < table->n_labels; ++i) { 1549 if (!strcmp(label, table->labels[i].v)) 1550 return table->labels[i].pos; 1551 } 1552 return -1; 1553 } 1554 1555 /* remember that we've used the label at position pos */ 1556 static int 1557 dnslabel_table_add(struct dnslabel_table *table, const char *label, off_t pos) 1558 { 1559 char *v; 1560 int p; 1561 if (table->n_labels == MAX_LABELS) 1562 return (-1); 1563 v = mm_strdup(label); 1564 if (v == NULL) 1565 return (-1); 1566 p = table->n_labels++; 1567 table->labels[p].v = v; 1568 table->labels[p].pos = pos; 1569 1570 return (0); 1571 } 1572 1573 /* Converts a string to a length-prefixed set of DNS labels, starting */ 1574 /* at buf[j]. name and buf must not overlap. name_len should be the length */ 1575 /* of name. table is optional, and is used for compression. */ 1576 /* */ 1577 /* Input: abc.def */ 1578 /* Output: <3>abc<3>def<0> */ 1579 /* */ 1580 /* Returns the first index after the encoded name, or negative on error. */ 1581 /* -1 label was > 63 bytes */ 1582 /* -2 name too long to fit in buffer. */ 1583 /* */ 1584 static off_t 1585 dnsname_to_labels(u8 *const buf, size_t buf_len, off_t j, 1586 const char *name, const size_t name_len, 1587 struct dnslabel_table *table) { 1588 const char *end = name + name_len; 1589 int ref = 0; 1590 u16 t_; 1591 1592 #define APPEND16(x) do { \ 1593 if (j + 2 > (off_t)buf_len) \ 1594 goto overflow; \ 1595 t_ = htons(x); \ 1596 memcpy(buf + j, &t_, 2); \ 1597 j += 2; \ 1598 } while (0) 1599 #define APPEND32(x) do { \ 1600 if (j + 4 > (off_t)buf_len) \ 1601 goto overflow; \ 1602 t32_ = htonl(x); \ 1603 memcpy(buf + j, &t32_, 4); \ 1604 j += 4; \ 1605 } while (0) 1606 1607 if (name_len > 255) return -2; 1608 1609 for (;;) { 1610 const char *const start = name; 1611 if (table && (ref = dnslabel_table_get_pos(table, name)) >= 0) { 1612 APPEND16(ref | 0xc000); 1613 return j; 1614 } 1615 name = strchr(name, '.'); 1616 if (!name) { 1617 const size_t label_len = end - start; 1618 if (label_len > 63) return -1; 1619 if ((size_t)(j+label_len+1) > buf_len) return -2; 1620 if (table) dnslabel_table_add(table, start, j); 1621 buf[j++] = (ev_uint8_t)label_len; 1622 1623 memcpy(buf + j, start, label_len); 1624 j += (int) label_len; 1625 break; 1626 } else { 1627 /* append length of the label. */ 1628 const size_t label_len = name - start; 1629 if (label_len > 63) return -1; 1630 if ((size_t)(j+label_len+1) > buf_len) return -2; 1631 if (table) dnslabel_table_add(table, start, j); 1632 buf[j++] = (ev_uint8_t)label_len; 1633 1634 memcpy(buf + j, start, label_len); 1635 j += (int) label_len; 1636 /* hop over the '.' */ 1637 name++; 1638 } 1639 } 1640 1641 /* the labels must be terminated by a 0. */ 1642 /* It's possible that the name ended in a . */ 1643 /* in which case the zero is already there */ 1644 if (!j || buf[j-1]) buf[j++] = 0; 1645 return j; 1646 overflow: 1647 return (-2); 1648 } 1649 1650 /* Finds the length of a dns request for a DNS name of the given */ 1651 /* length. The actual request may be smaller than the value returned */ 1652 /* here */ 1653 static size_t 1654 evdns_request_len(const size_t name_len) { 1655 return 96 + /* length of the DNS standard header */ 1656 name_len + 2 + 1657 4; /* space for the resource type */ 1658 } 1659 1660 /* build a dns request packet into buf. buf should be at least as long */ 1661 /* as evdns_request_len told you it should be. */ 1662 /* */ 1663 /* Returns the amount of space used. Negative on error. */ 1664 static int 1665 evdns_request_data_build(const char *const name, const size_t name_len, 1666 const u16 trans_id, const u16 type, const u16 class, 1667 u8 *const buf, size_t buf_len) { 1668 off_t j = 0; /* current offset into buf */ 1669 u16 t_; /* used by the macros */ 1670 1671 APPEND16(trans_id); 1672 APPEND16(0x0100); /* standard query, recusion needed */ 1673 APPEND16(1); /* one question */ 1674 APPEND16(0); /* no answers */ 1675 APPEND16(0); /* no authority */ 1676 APPEND16(0); /* no additional */ 1677 1678 j = dnsname_to_labels(buf, buf_len, j, name, name_len, NULL); 1679 if (j < 0) { 1680 return (int)j; 1681 } 1682 1683 APPEND16(type); 1684 APPEND16(class); 1685 1686 return (int)j; 1687 overflow: 1688 return (-1); 1689 } 1690 1691 /* exported function */ 1692 struct evdns_server_port * 1693 evdns_add_server_port_with_base(struct event_base *base, evutil_socket_t socket, int flags, evdns_request_callback_fn_type cb, void *user_data) 1694 { 1695 struct evdns_server_port *port; 1696 if (flags) 1697 return NULL; /* flags not yet implemented */ 1698 if (!(port = mm_malloc(sizeof(struct evdns_server_port)))) 1699 return NULL; 1700 memset(port, 0, sizeof(struct evdns_server_port)); 1701 1702 1703 port->socket = socket; 1704 port->refcnt = 1; 1705 port->choked = 0; 1706 port->closing = 0; 1707 port->user_callback = cb; 1708 port->user_data = user_data; 1709 port->pending_replies = NULL; 1710 port->event_base = base; 1711 1712 event_assign(&port->event, port->event_base, 1713 port->socket, EV_READ | EV_PERSIST, 1714 server_port_ready_callback, port); 1715 if (event_add(&port->event, NULL) < 0) { 1716 mm_free(port); 1717 return NULL; 1718 } 1719 EVTHREAD_ALLOC_LOCK(port->lock, EVTHREAD_LOCKTYPE_RECURSIVE); 1720 return port; 1721 } 1722 1723 struct evdns_server_port * 1724 evdns_add_server_port(evutil_socket_t socket, int flags, evdns_request_callback_fn_type cb, void *user_data) 1725 { 1726 return evdns_add_server_port_with_base(NULL, socket, flags, cb, user_data); 1727 } 1728 1729 /* exported function */ 1730 void 1731 evdns_close_server_port(struct evdns_server_port *port) 1732 { 1733 EVDNS_LOCK(port); 1734 if (--port->refcnt == 0) { 1735 EVDNS_UNLOCK(port); 1736 server_port_free(port); 1737 } else { 1738 port->closing = 1; 1739 } 1740 } 1741 1742 /* exported function */ 1743 int 1744 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) 1745 { 1746 struct server_request *req = TO_SERVER_REQUEST(req_); 1747 struct server_reply_item **itemp, *item; 1748 int *countp; 1749 int result = -1; 1750 1751 EVDNS_LOCK(req->port); 1752 if (req->response) /* have we already answered? */ 1753 goto done; 1754 1755 switch (section) { 1756 case EVDNS_ANSWER_SECTION: 1757 itemp = &req->answer; 1758 countp = &req->n_answer; 1759 break; 1760 case EVDNS_AUTHORITY_SECTION: 1761 itemp = &req->authority; 1762 countp = &req->n_authority; 1763 break; 1764 case EVDNS_ADDITIONAL_SECTION: 1765 itemp = &req->additional; 1766 countp = &req->n_additional; 1767 break; 1768 default: 1769 goto done; 1770 } 1771 while (*itemp) { 1772 itemp = &((*itemp)->next); 1773 } 1774 item = mm_malloc(sizeof(struct server_reply_item)); 1775 if (!item) 1776 goto done; 1777 item->next = NULL; 1778 if (!(item->name = mm_strdup(name))) { 1779 mm_free(item); 1780 goto done; 1781 } 1782 item->type = type; 1783 item->dns_question_class = class; 1784 item->ttl = ttl; 1785 item->is_name = is_name != 0; 1786 item->datalen = 0; 1787 item->data = NULL; 1788 if (data) { 1789 if (item->is_name) { 1790 if (!(item->data = mm_strdup(data))) { 1791 mm_free(item->name); 1792 mm_free(item); 1793 goto done; 1794 } 1795 item->datalen = (u16)-1; 1796 } else { 1797 if (!(item->data = mm_malloc(datalen))) { 1798 mm_free(item->name); 1799 mm_free(item); 1800 goto done; 1801 } 1802 item->datalen = datalen; 1803 memcpy(item->data, data, datalen); 1804 } 1805 } 1806 1807 *itemp = item; 1808 ++(*countp); 1809 result = 0; 1810 done: 1811 EVDNS_UNLOCK(req->port); 1812 return result; 1813 } 1814 1815 /* exported function */ 1816 int 1817 evdns_server_request_add_a_reply(struct evdns_server_request *req, const char *name, int n, const void *addrs, int ttl) 1818 { 1819 return evdns_server_request_add_reply( 1820 req, EVDNS_ANSWER_SECTION, name, TYPE_A, CLASS_INET, 1821 ttl, n*4, 0, addrs); 1822 } 1823 1824 /* exported function */ 1825 int 1826 evdns_server_request_add_aaaa_reply(struct evdns_server_request *req, const char *name, int n, const void *addrs, int ttl) 1827 { 1828 return evdns_server_request_add_reply( 1829 req, EVDNS_ANSWER_SECTION, name, TYPE_AAAA, CLASS_INET, 1830 ttl, n*16, 0, addrs); 1831 } 1832 1833 /* exported function */ 1834 int 1835 evdns_server_request_add_ptr_reply(struct evdns_server_request *req, struct in_addr *in, const char *inaddr_name, const char *hostname, int ttl) 1836 { 1837 u32 a; 1838 char buf[32]; 1839 if (in && inaddr_name) 1840 return -1; 1841 else if (!in && !inaddr_name) 1842 return -1; 1843 if (in) { 1844 a = ntohl(in->s_addr); 1845 evutil_snprintf(buf, sizeof(buf), "%d.%d.%d.%d.in-addr.arpa", 1846 (int)(u8)((a )&0xff), 1847 (int)(u8)((a>>8 )&0xff), 1848 (int)(u8)((a>>16)&0xff), 1849 (int)(u8)((a>>24)&0xff)); 1850 inaddr_name = buf; 1851 } 1852 return evdns_server_request_add_reply( 1853 req, EVDNS_ANSWER_SECTION, inaddr_name, TYPE_PTR, CLASS_INET, 1854 ttl, -1, 1, hostname); 1855 } 1856 1857 /* exported function */ 1858 int 1859 evdns_server_request_add_cname_reply(struct evdns_server_request *req, const char *name, const char *cname, int ttl) 1860 { 1861 return evdns_server_request_add_reply( 1862 req, EVDNS_ANSWER_SECTION, name, TYPE_CNAME, CLASS_INET, 1863 ttl, -1, 1, cname); 1864 } 1865 1866 /* exported function */ 1867 void 1868 evdns_server_request_set_flags(struct evdns_server_request *exreq, int flags) 1869 { 1870 struct server_request *req = TO_SERVER_REQUEST(exreq); 1871 req->base.flags &= ~(EVDNS_FLAGS_AA|EVDNS_FLAGS_RD); 1872 req->base.flags |= flags; 1873 } 1874 1875 static int 1876 evdns_server_request_format_response(struct server_request *req, int err) 1877 { 1878 unsigned char buf[1500]; 1879 size_t buf_len = sizeof(buf); 1880 off_t j = 0, r; 1881 u16 t_; 1882 u32 t32_; 1883 int i; 1884 u16 flags; 1885 struct dnslabel_table table; 1886 1887 if (err < 0 || err > 15) return -1; 1888 1889 /* Set response bit and error code; copy OPCODE and RD fields from 1890 * question; copy RA and AA if set by caller. */ 1891 flags = req->base.flags; 1892 flags |= (0x8000 | err); 1893 1894 dnslabel_table_init(&table); 1895 APPEND16(req->trans_id); 1896 APPEND16(flags); 1897 APPEND16(req->base.nquestions); 1898 APPEND16(req->n_answer); 1899 APPEND16(req->n_authority); 1900 APPEND16(req->n_additional); 1901 1902 /* Add questions. */ 1903 for (i=0; i < req->base.nquestions; ++i) { 1904 const char *s = req->base.questions[i]->name; 1905 j = dnsname_to_labels(buf, buf_len, j, s, strlen(s), &table); 1906 if (j < 0) { 1907 dnslabel_clear(&table); 1908 return (int) j; 1909 } 1910 APPEND16(req->base.questions[i]->type); 1911 APPEND16(req->base.questions[i]->dns_question_class); 1912 } 1913 1914 /* Add answer, authority, and additional sections. */ 1915 for (i=0; i<3; ++i) { 1916 struct server_reply_item *item; 1917 if (i==0) 1918 item = req->answer; 1919 else if (i==1) 1920 item = req->authority; 1921 else 1922 item = req->additional; 1923 while (item) { 1924 r = dnsname_to_labels(buf, buf_len, j, item->name, strlen(item->name), &table); 1925 if (r < 0) 1926 goto overflow; 1927 j = r; 1928 1929 APPEND16(item->type); 1930 APPEND16(item->dns_question_class); 1931 APPEND32(item->ttl); 1932 if (item->is_name) { 1933 off_t len_idx = j, name_start; 1934 j += 2; 1935 name_start = j; 1936 r = dnsname_to_labels(buf, buf_len, j, item->data, strlen(item->data), &table); 1937 if (r < 0) 1938 goto overflow; 1939 j = r; 1940 t_ = htons( (short) (j-name_start) ); 1941 memcpy(buf+len_idx, &t_, 2); 1942 } else { 1943 APPEND16(item->datalen); 1944 if (j+item->datalen > (off_t)buf_len) 1945 goto overflow; 1946 memcpy(buf+j, item->data, item->datalen); 1947 j += item->datalen; 1948 } 1949 item = item->next; 1950 } 1951 } 1952 1953 if (j > 512) { 1954 overflow: 1955 j = 512; 1956 buf[2] |= 0x02; /* set the truncated bit. */ 1957 } 1958 1959 req->response_len = j; 1960 1961 if (!(req->response = mm_malloc(req->response_len))) { 1962 server_request_free_answers(req); 1963 dnslabel_clear(&table); 1964 return (-1); 1965 } 1966 memcpy(req->response, buf, req->response_len); 1967 server_request_free_answers(req); 1968 dnslabel_clear(&table); 1969 return (0); 1970 } 1971 1972 /* exported function */ 1973 int 1974 evdns_server_request_respond(struct evdns_server_request *req_, int err) 1975 { 1976 struct server_request *req = TO_SERVER_REQUEST(req_); 1977 struct evdns_server_port *port = req->port; 1978 int r = -1; 1979 1980 EVDNS_LOCK(port); 1981 if (!req->response) { 1982 if ((r = evdns_server_request_format_response(req, err))<0) 1983 goto done; 1984 } 1985 1986 r = sendto(port->socket, req->response, (int)req->response_len, 0, 1987 (struct sockaddr*) &req->addr, (ev_socklen_t)req->addrlen); 1988 if (r<0) { 1989 int sock_err = evutil_socket_geterror(port->socket); 1990 if (EVUTIL_ERR_RW_RETRIABLE(sock_err)) 1991 goto done; 1992 1993 if (port->pending_replies) { 1994 req->prev_pending = port->pending_replies->prev_pending; 1995 req->next_pending = port->pending_replies; 1996 req->prev_pending->next_pending = 1997 req->next_pending->prev_pending = req; 1998 } else { 1999 req->prev_pending = req->next_pending = req; 2000 port->pending_replies = req; 2001 port->choked = 1; 2002 2003 (void) event_del(&port->event); 2004 event_assign(&port->event, port->event_base, port->socket, (port->closing?0:EV_READ) | EV_WRITE | EV_PERSIST, server_port_ready_callback, port); 2005 2006 if (event_add(&port->event, NULL) < 0) { 2007 log(EVDNS_LOG_WARN, "Error from libevent when adding event for DNS server"); 2008 } 2009 2010 } 2011 2012 r = 1; 2013 goto done; 2014 } 2015 if (server_request_free(req)) { 2016 r = 0; 2017 goto done; 2018 } 2019 2020 if (port->pending_replies) 2021 server_port_flush(port); 2022 2023 r = 0; 2024 done: 2025 EVDNS_UNLOCK(port); 2026 return r; 2027 } 2028 2029 /* Free all storage held by RRs in req. */ 2030 static void 2031 server_request_free_answers(struct server_request *req) 2032 { 2033 struct server_reply_item *victim, *next, **list; 2034 int i; 2035 for (i = 0; i < 3; ++i) { 2036 if (i==0) 2037 list = &req->answer; 2038 else if (i==1) 2039 list = &req->authority; 2040 else 2041 list = &req->additional; 2042 2043 victim = *list; 2044 while (victim) { 2045 next = victim->next; 2046 mm_free(victim->name); 2047 if (victim->data) 2048 mm_free(victim->data); 2049 mm_free(victim); 2050 victim = next; 2051 } 2052 *list = NULL; 2053 } 2054 } 2055 2056 /* Free all storage held by req, and remove links to it. */ 2057 /* return true iff we just wound up freeing the server_port. */ 2058 static int 2059 server_request_free(struct server_request *req) 2060 { 2061 int i, rc=1, lock=0; 2062 if (req->base.questions) { 2063 for (i = 0; i < req->base.nquestions; ++i) 2064 mm_free(req->base.questions[i]); 2065 mm_free(req->base.questions); 2066 } 2067 2068 if (req->port) { 2069 EVDNS_LOCK(req->port); 2070 lock=1; 2071 if (req->port->pending_replies == req) { 2072 if (req->next_pending && req->next_pending != req) 2073 req->port->pending_replies = req->next_pending; 2074 else 2075 req->port->pending_replies = NULL; 2076 } 2077 rc = --req->port->refcnt; 2078 } 2079 2080 if (req->response) { 2081 mm_free(req->response); 2082 } 2083 2084 server_request_free_answers(req); 2085 2086 if (req->next_pending && req->next_pending != req) { 2087 req->next_pending->prev_pending = req->prev_pending; 2088 req->prev_pending->next_pending = req->next_pending; 2089 } 2090 2091 if (rc == 0) { 2092 EVDNS_UNLOCK(req->port); /* ????? nickm */ 2093 server_port_free(req->port); 2094 mm_free(req); 2095 return (1); 2096 } 2097 if (lock) 2098 EVDNS_UNLOCK(req->port); 2099 mm_free(req); 2100 return (0); 2101 } 2102 2103 /* Free all storage held by an evdns_server_port. Only called when */ 2104 static void 2105 server_port_free(struct evdns_server_port *port) 2106 { 2107 EVUTIL_ASSERT(port); 2108 EVUTIL_ASSERT(!port->refcnt); 2109 EVUTIL_ASSERT(!port->pending_replies); 2110 if (port->socket > 0) { 2111 evutil_closesocket(port->socket); 2112 port->socket = -1; 2113 } 2114 (void) event_del(&port->event); 2115 event_debug_unassign(&port->event); 2116 EVTHREAD_FREE_LOCK(port->lock, EVTHREAD_LOCKTYPE_RECURSIVE); 2117 mm_free(port); 2118 } 2119 2120 /* exported function */ 2121 int 2122 evdns_server_request_drop(struct evdns_server_request *req_) 2123 { 2124 struct server_request *req = TO_SERVER_REQUEST(req_); 2125 server_request_free(req); 2126 return 0; 2127 } 2128 2129 /* exported function */ 2130 int 2131 evdns_server_request_get_requesting_addr(struct evdns_server_request *req_, struct sockaddr *sa, int addr_len) 2132 { 2133 struct server_request *req = TO_SERVER_REQUEST(req_); 2134 if (addr_len < (int)req->addrlen) 2135 return -1; 2136 memcpy(sa, &(req->addr), req->addrlen); 2137 return req->addrlen; 2138 } 2139 2140 #undef APPEND16 2141 #undef APPEND32 2142 2143 /* this is a libevent callback function which is called when a request */ 2144 /* has timed out. */ 2145 static void 2146 evdns_request_timeout_callback(evutil_socket_t fd, short events, void *arg) { 2147 struct request *const req = (struct request *) arg; 2148 struct evdns_base *base = req->base; 2149 2150 (void) fd; 2151 (void) events; 2152 2153 log(EVDNS_LOG_DEBUG, "Request %p timed out", arg); 2154 EVDNS_LOCK(base); 2155 2156 req->ns->timedout++; 2157 if (req->ns->timedout > req->base->global_max_nameserver_timeout) { 2158 req->ns->timedout = 0; 2159 nameserver_failed(req->ns, "request timed out."); 2160 } 2161 2162 if (req->tx_count >= req->base->global_max_retransmits) { 2163 /* this request has failed */ 2164 log(EVDNS_LOG_DEBUG, "Giving up on request %p; tx_count==%d", 2165 arg, req->tx_count); 2166 reply_schedule_callback(req, 0, DNS_ERR_TIMEOUT, NULL); 2167 request_finished(req, &REQ_HEAD(req->base, req->trans_id), 1); 2168 } else { 2169 /* retransmit it */ 2170 struct nameserver *new_ns; 2171 log(EVDNS_LOG_DEBUG, "Retransmitting request %p; tx_count==%d", 2172 arg, req->tx_count); 2173 (void) evtimer_del(&req->timeout_event); 2174 new_ns = nameserver_pick(base); 2175 if (new_ns) 2176 req->ns = new_ns; 2177 evdns_request_transmit(req); 2178 } 2179 EVDNS_UNLOCK(base); 2180 } 2181 2182 /* try to send a request to a given server. */ 2183 /* */ 2184 /* return: */ 2185 /* 0 ok */ 2186 /* 1 temporary failure */ 2187 /* 2 other failure */ 2188 static int 2189 evdns_request_transmit_to(struct request *req, struct nameserver *server) { 2190 int r; 2191 ASSERT_LOCKED(req->base); 2192 ASSERT_VALID_REQUEST(req); 2193 r = sendto(server->socket, (void*)req->request, req->request_len, 0, 2194 (struct sockaddr *)&server->address, server->addrlen); 2195 if (r < 0) { 2196 int err = evutil_socket_geterror(server->socket); 2197 if (EVUTIL_ERR_RW_RETRIABLE(err)) 2198 return 1; 2199 nameserver_failed(req->ns, evutil_socket_error_to_string(err)); 2200 return 2; 2201 } else if (r != (int)req->request_len) { 2202 return 1; /* short write */ 2203 } else { 2204 return 0; 2205 } 2206 } 2207 2208 /* try to send a request, updating the fields of the request */ 2209 /* as needed */ 2210 /* */ 2211 /* return: */ 2212 /* 0 ok */ 2213 /* 1 failed */ 2214 static int 2215 evdns_request_transmit(struct request *req) { 2216 int retcode = 0, r; 2217 2218 ASSERT_LOCKED(req->base); 2219 ASSERT_VALID_REQUEST(req); 2220 /* if we fail to send this packet then this flag marks it */ 2221 /* for evdns_transmit */ 2222 req->transmit_me = 1; 2223 EVUTIL_ASSERT(req->trans_id != 0xffff); 2224 2225 if (req->ns->choked) { 2226 /* don't bother trying to write to a socket */ 2227 /* which we have had EAGAIN from */ 2228 return 1; 2229 } 2230 2231 r = evdns_request_transmit_to(req, req->ns); 2232 switch (r) { 2233 case 1: 2234 /* temp failure */ 2235 req->ns->choked = 1; 2236 nameserver_write_waiting(req->ns, 1); 2237 return 1; 2238 case 2: 2239 /* failed to transmit the request entirely. */ 2240 retcode = 1; 2241 /* fall through: we'll set a timeout, which will time out, 2242 * and make us retransmit the request anyway. */ 2243 default: 2244 /* all ok */ 2245 log(EVDNS_LOG_DEBUG, 2246 "Setting timeout for request %p, sent to nameserver %p", req, req->ns); 2247 if (evtimer_add(&req->timeout_event, &req->base->global_timeout) < 0) { 2248 log(EVDNS_LOG_WARN, 2249 "Error from libevent when adding timer for request %p", 2250 req); 2251 /* ???? Do more? */ 2252 } 2253 req->tx_count++; 2254 req->transmit_me = 0; 2255 return retcode; 2256 } 2257 } 2258 2259 static void 2260 nameserver_probe_callback(int result, char type, int count, int ttl, void *addresses, void *arg) { 2261 struct nameserver *const ns = (struct nameserver *) arg; 2262 (void) type; 2263 (void) count; 2264 (void) ttl; 2265 (void) addresses; 2266 2267 if (result == DNS_ERR_CANCEL) { 2268 /* We canceled this request because the nameserver came up 2269 * for some other reason. Do not change our opinion about 2270 * the nameserver. */ 2271 return; 2272 } 2273 2274 EVDNS_LOCK(ns->base); 2275 ns->probe_request = NULL; 2276 if (result == DNS_ERR_NONE || result == DNS_ERR_NOTEXIST) { 2277 /* this is a good reply */ 2278 nameserver_up(ns); 2279 } else { 2280 nameserver_probe_failed(ns); 2281 } 2282 EVDNS_UNLOCK(ns->base); 2283 } 2284 2285 static void 2286 nameserver_send_probe(struct nameserver *const ns) { 2287 struct evdns_request *handle; 2288 struct request *req; 2289 char addrbuf[128]; 2290 /* here we need to send a probe to a given nameserver */ 2291 /* in the hope that it is up now. */ 2292 2293 ASSERT_LOCKED(ns->base); 2294 log(EVDNS_LOG_DEBUG, "Sending probe to %s", 2295 evutil_format_sockaddr_port_( 2296 (struct sockaddr *)&ns->address, 2297 addrbuf, sizeof(addrbuf))); 2298 handle = mm_calloc(1, sizeof(*handle)); 2299 if (!handle) return; 2300 req = request_new(ns->base, handle, TYPE_A, "google.com", DNS_QUERY_NO_SEARCH, nameserver_probe_callback, ns); 2301 if (!req) { 2302 mm_free(handle); 2303 return; 2304 } 2305 ns->probe_request = handle; 2306 /* we force this into the inflight queue no matter what */ 2307 request_trans_id_set(req, transaction_id_pick(ns->base)); 2308 req->ns = ns; 2309 request_submit(req); 2310 } 2311 2312 /* returns: */ 2313 /* 0 didn't try to transmit anything */ 2314 /* 1 tried to transmit something */ 2315 static int 2316 evdns_transmit(struct evdns_base *base) { 2317 char did_try_to_transmit = 0; 2318 int i; 2319 2320 ASSERT_LOCKED(base); 2321 for (i = 0; i < base->n_req_heads; ++i) { 2322 if (base->req_heads[i]) { 2323 struct request *const started_at = base->req_heads[i], *req = started_at; 2324 /* first transmit all the requests which are currently waiting */ 2325 do { 2326 if (req->transmit_me) { 2327 did_try_to_transmit = 1; 2328 evdns_request_transmit(req); 2329 } 2330 2331 req = req->next; 2332 } while (req != started_at); 2333 } 2334 } 2335 2336 return did_try_to_transmit; 2337 } 2338 2339 /* exported function */ 2340 int 2341 evdns_base_count_nameservers(struct evdns_base *base) 2342 { 2343 const struct nameserver *server; 2344 int n = 0; 2345 2346 EVDNS_LOCK(base); 2347 server = base->server_head; 2348 if (!server) 2349 goto done; 2350 do { 2351 ++n; 2352 server = server->next; 2353 } while (server != base->server_head); 2354 done: 2355 EVDNS_UNLOCK(base); 2356 return n; 2357 } 2358 2359 int 2360 evdns_count_nameservers(void) 2361 { 2362 return evdns_base_count_nameservers(current_base); 2363 } 2364 2365 /* exported function */ 2366 int 2367 evdns_base_clear_nameservers_and_suspend(struct evdns_base *base) 2368 { 2369 struct nameserver *server, *started_at; 2370 int i; 2371 2372 EVDNS_LOCK(base); 2373 server = base->server_head; 2374 started_at = base->server_head; 2375 if (!server) { 2376 EVDNS_UNLOCK(base); 2377 return 0; 2378 } 2379 while (1) { 2380 struct nameserver *next = server->next; 2381 (void) event_del(&server->event); 2382 if (evtimer_initialized(&server->timeout_event)) 2383 (void) evtimer_del(&server->timeout_event); 2384 if (server->probe_request) { 2385 evdns_cancel_request(server->base, server->probe_request); 2386 server->probe_request = NULL; 2387 } 2388 if (server->socket >= 0) 2389 evutil_closesocket(server->socket); 2390 mm_free(server); 2391 if (next == started_at) 2392 break; 2393 server = next; 2394 } 2395 base->server_head = NULL; 2396 base->global_good_nameservers = 0; 2397 2398 for (i = 0; i < base->n_req_heads; ++i) { 2399 struct request *req, *req_started_at; 2400 req = req_started_at = base->req_heads[i]; 2401 while (req) { 2402 struct request *next = req->next; 2403 req->tx_count = req->reissue_count = 0; 2404 req->ns = NULL; 2405 /* ???? What to do about searches? */ 2406 (void) evtimer_del(&req->timeout_event); 2407 req->trans_id = 0; 2408 req->transmit_me = 0; 2409 2410 base->global_requests_waiting++; 2411 evdns_request_insert(req, &base->req_waiting_head); 2412 /* We want to insert these suspended elements at the front of 2413 * the waiting queue, since they were pending before any of 2414 * the waiting entries were added. This is a circular list, 2415 * so we can just shift the start back by one.*/ 2416 base->req_waiting_head = base->req_waiting_head->prev; 2417 2418 if (next == req_started_at) 2419 break; 2420 req = next; 2421 } 2422 base->req_heads[i] = NULL; 2423 } 2424 2425 base->global_requests_inflight = 0; 2426 2427 EVDNS_UNLOCK(base); 2428 return 0; 2429 } 2430 2431 int 2432 evdns_clear_nameservers_and_suspend(void) 2433 { 2434 return evdns_base_clear_nameservers_and_suspend(current_base); 2435 } 2436 2437 2438 /* exported function */ 2439 int 2440 evdns_base_resume(struct evdns_base *base) 2441 { 2442 EVDNS_LOCK(base); 2443 evdns_requests_pump_waiting_queue(base); 2444 EVDNS_UNLOCK(base); 2445 return 0; 2446 } 2447 2448 int 2449 evdns_resume(void) 2450 { 2451 return evdns_base_resume(current_base); 2452 } 2453 2454 static int 2455 evdns_nameserver_add_impl_(struct evdns_base *base, const struct sockaddr *address, int addrlen) { 2456 /* first check to see if we already have this nameserver */ 2457 2458 const struct nameserver *server = base->server_head, *const started_at = base->server_head; 2459 struct nameserver *ns; 2460 int err = 0; 2461 char addrbuf[128]; 2462 2463 ASSERT_LOCKED(base); 2464 if (server) { 2465 do { 2466 if (!evutil_sockaddr_cmp((struct sockaddr*)&server->address, address, 1)) return 3; 2467 server = server->next; 2468 } while (server != started_at); 2469 } 2470 if (addrlen > (int)sizeof(ns->address)) { 2471 log(EVDNS_LOG_DEBUG, "Addrlen %d too long.", (int)addrlen); 2472 return 2; 2473 } 2474 2475 ns = (struct nameserver *) mm_malloc(sizeof(struct nameserver)); 2476 if (!ns) return -1; 2477 2478 memset(ns, 0, sizeof(struct nameserver)); 2479 ns->base = base; 2480 2481 evtimer_assign(&ns->timeout_event, ns->base->event_base, nameserver_prod_callback, ns); 2482 2483 ns->socket = evutil_socket_(address->sa_family, 2484 SOCK_DGRAM|EVUTIL_SOCK_NONBLOCK|EVUTIL_SOCK_CLOEXEC, 0); 2485 if (ns->socket < 0) { err = 1; goto out1; } 2486 2487 if (base->global_outgoing_addrlen && 2488 !evutil_sockaddr_is_loopback_(address)) { 2489 if (bind(ns->socket, 2490 (struct sockaddr*)&base->global_outgoing_address, 2491 base->global_outgoing_addrlen) < 0) { 2492 log(EVDNS_LOG_WARN,"Couldn't bind to outgoing address"); 2493 err = 2; 2494 goto out2; 2495 } 2496 } 2497 2498 memcpy(&ns->address, address, addrlen); 2499 ns->addrlen = addrlen; 2500 ns->state = 1; 2501 event_assign(&ns->event, ns->base->event_base, ns->socket, EV_READ | EV_PERSIST, nameserver_ready_callback, ns); 2502 if (event_add(&ns->event, NULL) < 0) { 2503 err = 2; 2504 goto out2; 2505 } 2506 2507 log(EVDNS_LOG_DEBUG, "Added nameserver %s as %p", 2508 evutil_format_sockaddr_port_(address, addrbuf, sizeof(addrbuf)), ns); 2509 2510 /* insert this nameserver into the list of them */ 2511 if (!base->server_head) { 2512 ns->next = ns->prev = ns; 2513 base->server_head = ns; 2514 } else { 2515 ns->next = base->server_head->next; 2516 ns->prev = base->server_head; 2517 base->server_head->next = ns; 2518 ns->next->prev = ns; 2519 } 2520 2521 base->global_good_nameservers++; 2522 2523 return 0; 2524 2525 out2: 2526 evutil_closesocket(ns->socket); 2527 out1: 2528 event_debug_unassign(&ns->event); 2529 mm_free(ns); 2530 log(EVDNS_LOG_WARN, "Unable to add nameserver %s: error %d", 2531 evutil_format_sockaddr_port_(address, addrbuf, sizeof(addrbuf)), err); 2532 return err; 2533 } 2534 2535 /* exported function */ 2536 int 2537 evdns_base_nameserver_add(struct evdns_base *base, unsigned long int address) 2538 { 2539 struct sockaddr_in sin; 2540 int res; 2541 memset(&sin, 0, sizeof(sin)); 2542 sin.sin_addr.s_addr = address; 2543 sin.sin_port = htons(53); 2544 sin.sin_family = AF_INET; 2545 EVDNS_LOCK(base); 2546 res = evdns_nameserver_add_impl_(base, (struct sockaddr*)&sin, sizeof(sin)); 2547 EVDNS_UNLOCK(base); 2548 return res; 2549 } 2550 2551 int 2552 evdns_nameserver_add(unsigned long int address) { 2553 if (!current_base) 2554 current_base = evdns_base_new(NULL, 0); 2555 return evdns_base_nameserver_add(current_base, address); 2556 } 2557 2558 static void 2559 sockaddr_setport(struct sockaddr *sa, ev_uint16_t port) 2560 { 2561 if (sa->sa_family == AF_INET) { 2562 ((struct sockaddr_in *)sa)->sin_port = htons(port); 2563 } else if (sa->sa_family == AF_INET6) { 2564 ((struct sockaddr_in6 *)sa)->sin6_port = htons(port); 2565 } 2566 } 2567 2568 static ev_uint16_t 2569 sockaddr_getport(struct sockaddr *sa) 2570 { 2571 if (sa->sa_family == AF_INET) { 2572 return ntohs(((struct sockaddr_in *)sa)->sin_port); 2573 } else if (sa->sa_family == AF_INET6) { 2574 return ntohs(((struct sockaddr_in6 *)sa)->sin6_port); 2575 } else { 2576 return 0; 2577 } 2578 } 2579 2580 /* exported function */ 2581 int 2582 evdns_base_nameserver_ip_add(struct evdns_base *base, const char *ip_as_string) { 2583 struct sockaddr_storage ss; 2584 struct sockaddr *sa; 2585 int len = sizeof(ss); 2586 int res; 2587 if (evutil_parse_sockaddr_port(ip_as_string, (struct sockaddr *)&ss, 2588 &len)) { 2589 log(EVDNS_LOG_WARN, "Unable to parse nameserver address %s", 2590 ip_as_string); 2591 return 4; 2592 } 2593 sa = (struct sockaddr *) &ss; 2594 if (sockaddr_getport(sa) == 0) 2595 sockaddr_setport(sa, 53); 2596 2597 EVDNS_LOCK(base); 2598 res = evdns_nameserver_add_impl_(base, sa, len); 2599 EVDNS_UNLOCK(base); 2600 return res; 2601 } 2602 2603 int 2604 evdns_nameserver_ip_add(const char *ip_as_string) { 2605 if (!current_base) 2606 current_base = evdns_base_new(NULL, 0); 2607 return evdns_base_nameserver_ip_add(current_base, ip_as_string); 2608 } 2609 2610 int 2611 evdns_base_nameserver_sockaddr_add(struct evdns_base *base, 2612 const struct sockaddr *sa, ev_socklen_t len, unsigned flags) 2613 { 2614 int res; 2615 EVUTIL_ASSERT(base); 2616 EVDNS_LOCK(base); 2617 res = evdns_nameserver_add_impl_(base, sa, len); 2618 EVDNS_UNLOCK(base); 2619 return res; 2620 } 2621 2622 /* remove from the queue */ 2623 static void 2624 evdns_request_remove(struct request *req, struct request **head) 2625 { 2626 ASSERT_LOCKED(req->base); 2627 ASSERT_VALID_REQUEST(req); 2628 2629 #if 0 2630 { 2631 struct request *ptr; 2632 int found = 0; 2633 EVUTIL_ASSERT(*head != NULL); 2634 2635 ptr = *head; 2636 do { 2637 if (ptr == req) { 2638 found = 1; 2639 break; 2640 } 2641 ptr = ptr->next; 2642 } while (ptr != *head); 2643 EVUTIL_ASSERT(found); 2644 2645 EVUTIL_ASSERT(req->next); 2646 } 2647 #endif 2648 2649 if (req->next == req) { 2650 /* only item in the list */ 2651 *head = NULL; 2652 } else { 2653 req->next->prev = req->prev; 2654 req->prev->next = req->next; 2655 if (*head == req) *head = req->next; 2656 } 2657 req->next = req->prev = NULL; 2658 } 2659 2660 /* insert into the tail of the queue */ 2661 static void 2662 evdns_request_insert(struct request *req, struct request **head) { 2663 ASSERT_LOCKED(req->base); 2664 ASSERT_VALID_REQUEST(req); 2665 if (!*head) { 2666 *head = req; 2667 req->next = req->prev = req; 2668 return; 2669 } 2670 2671 req->prev = (*head)->prev; 2672 req->prev->next = req; 2673 req->next = *head; 2674 (*head)->prev = req; 2675 } 2676 2677 static int 2678 string_num_dots(const char *s) { 2679 int count = 0; 2680 while ((s = strchr(s, '.'))) { 2681 s++; 2682 count++; 2683 } 2684 return count; 2685 } 2686 2687 static struct request * 2688 request_new(struct evdns_base *base, struct evdns_request *handle, int type, 2689 const char *name, int flags, evdns_callback_type callback, 2690 void *user_ptr) { 2691 2692 const char issuing_now = 2693 (base->global_requests_inflight < base->global_max_requests_inflight) ? 1 : 0; 2694 2695 const size_t name_len = strlen(name); 2696 const size_t request_max_len = evdns_request_len(name_len); 2697 const u16 trans_id = issuing_now ? transaction_id_pick(base) : 0xffff; 2698 /* the request data is alloced in a single block with the header */ 2699 struct request *const req = 2700 mm_malloc(sizeof(struct request) + request_max_len); 2701 int rlen; 2702 char namebuf[256]; 2703 (void) flags; 2704 2705 ASSERT_LOCKED(base); 2706 2707 if (!req) return NULL; 2708 2709 if (name_len >= sizeof(namebuf)) { 2710 mm_free(req); 2711 return NULL; 2712 } 2713 2714 memset(req, 0, sizeof(struct request)); 2715 req->base = base; 2716 2717 evtimer_assign(&req->timeout_event, req->base->event_base, evdns_request_timeout_callback, req); 2718 2719 if (base->global_randomize_case) { 2720 unsigned i; 2721 char randbits[(sizeof(namebuf)+7)/8]; 2722 strlcpy(namebuf, name, sizeof(namebuf)); 2723 evutil_secure_rng_get_bytes(randbits, (name_len+7)/8); 2724 for (i = 0; i < name_len; ++i) { 2725 if (EVUTIL_ISALPHA_(namebuf[i])) { 2726 if ((randbits[i >> 3] & (1<<(i & 7)))) 2727 namebuf[i] |= 0x20; 2728 else 2729 namebuf[i] &= ~0x20; 2730 } 2731 } 2732 name = namebuf; 2733 } 2734 2735 /* request data lives just after the header */ 2736 req->request = ((u8 *) req) + sizeof(struct request); 2737 /* denotes that the request data shouldn't be free()ed */ 2738 req->request_appended = 1; 2739 rlen = evdns_request_data_build(name, name_len, trans_id, 2740 type, CLASS_INET, req->request, request_max_len); 2741 if (rlen < 0) 2742 goto err1; 2743 2744 req->request_len = rlen; 2745 req->trans_id = trans_id; 2746 req->tx_count = 0; 2747 req->request_type = type; 2748 req->user_pointer = user_ptr; 2749 req->user_callback = callback; 2750 req->ns = issuing_now ? nameserver_pick(base) : NULL; 2751 req->next = req->prev = NULL; 2752 req->handle = handle; 2753 if (handle) { 2754 handle->current_req = req; 2755 handle->base = base; 2756 } 2757 2758 return req; 2759 err1: 2760 mm_free(req); 2761 return NULL; 2762 } 2763 2764 static void 2765 request_submit(struct request *const req) { 2766 struct evdns_base *base = req->base; 2767 ASSERT_LOCKED(base); 2768 ASSERT_VALID_REQUEST(req); 2769 if (req->ns) { 2770 /* if it has a nameserver assigned then this is going */ 2771 /* straight into the inflight queue */ 2772 evdns_request_insert(req, &REQ_HEAD(base, req->trans_id)); 2773 base->global_requests_inflight++; 2774 evdns_request_transmit(req); 2775 } else { 2776 evdns_request_insert(req, &base->req_waiting_head); 2777 base->global_requests_waiting++; 2778 } 2779 } 2780 2781 /* exported function */ 2782 void 2783 evdns_cancel_request(struct evdns_base *base, struct evdns_request *handle) 2784 { 2785 struct request *req; 2786 2787 if (!handle->current_req) 2788 return; 2789 2790 if (!base) { 2791 /* This redundancy is silly; can we fix it? (Not for 2.0) XXXX */ 2792 base = handle->base; 2793 if (!base) 2794 base = handle->current_req->base; 2795 } 2796 2797 EVDNS_LOCK(base); 2798 if (handle->pending_cb) { 2799 EVDNS_UNLOCK(base); 2800 return; 2801 } 2802 2803 req = handle->current_req; 2804 ASSERT_VALID_REQUEST(req); 2805 2806 reply_schedule_callback(req, 0, DNS_ERR_CANCEL, NULL); 2807 if (req->ns) { 2808 /* remove from inflight queue */ 2809 request_finished(req, &REQ_HEAD(base, req->trans_id), 1); 2810 } else { 2811 /* remove from global_waiting head */ 2812 request_finished(req, &base->req_waiting_head, 1); 2813 } 2814 EVDNS_UNLOCK(base); 2815 } 2816 2817 /* exported function */ 2818 struct evdns_request * 2819 evdns_base_resolve_ipv4(struct evdns_base *base, const char *name, int flags, 2820 evdns_callback_type callback, void *ptr) { 2821 struct evdns_request *handle; 2822 struct request *req; 2823 log(EVDNS_LOG_DEBUG, "Resolve requested for %s", name); 2824 handle = mm_calloc(1, sizeof(*handle)); 2825 if (handle == NULL) 2826 return NULL; 2827 EVDNS_LOCK(base); 2828 if (flags & DNS_QUERY_NO_SEARCH) { 2829 req = 2830 request_new(base, handle, TYPE_A, name, flags, 2831 callback, ptr); 2832 if (req) 2833 request_submit(req); 2834 } else { 2835 search_request_new(base, handle, TYPE_A, name, flags, 2836 callback, ptr); 2837 } 2838 if (handle->current_req == NULL) { 2839 mm_free(handle); 2840 handle = NULL; 2841 } 2842 EVDNS_UNLOCK(base); 2843 return handle; 2844 } 2845 2846 int evdns_resolve_ipv4(const char *name, int flags, 2847 evdns_callback_type callback, void *ptr) 2848 { 2849 return evdns_base_resolve_ipv4(current_base, name, flags, callback, ptr) 2850 ? 0 : -1; 2851 } 2852 2853 2854 /* exported function */ 2855 struct evdns_request * 2856 evdns_base_resolve_ipv6(struct evdns_base *base, 2857 const char *name, int flags, 2858 evdns_callback_type callback, void *ptr) 2859 { 2860 struct evdns_request *handle; 2861 struct request *req; 2862 log(EVDNS_LOG_DEBUG, "Resolve requested for %s", name); 2863 handle = mm_calloc(1, sizeof(*handle)); 2864 if (handle == NULL) 2865 return NULL; 2866 EVDNS_LOCK(base); 2867 if (flags & DNS_QUERY_NO_SEARCH) { 2868 req = request_new(base, handle, TYPE_AAAA, name, flags, 2869 callback, ptr); 2870 if (req) 2871 request_submit(req); 2872 } else { 2873 search_request_new(base, handle, TYPE_AAAA, name, flags, 2874 callback, ptr); 2875 } 2876 if (handle->current_req == NULL) { 2877 mm_free(handle); 2878 handle = NULL; 2879 } 2880 EVDNS_UNLOCK(base); 2881 return handle; 2882 } 2883 2884 int evdns_resolve_ipv6(const char *name, int flags, 2885 evdns_callback_type callback, void *ptr) { 2886 return evdns_base_resolve_ipv6(current_base, name, flags, callback, ptr) 2887 ? 0 : -1; 2888 } 2889 2890 struct evdns_request * 2891 evdns_base_resolve_reverse(struct evdns_base *base, const struct in_addr *in, int flags, evdns_callback_type callback, void *ptr) { 2892 char buf[32]; 2893 struct evdns_request *handle; 2894 struct request *req; 2895 u32 a; 2896 EVUTIL_ASSERT(in); 2897 a = ntohl(in->s_addr); 2898 evutil_snprintf(buf, sizeof(buf), "%d.%d.%d.%d.in-addr.arpa", 2899 (int)(u8)((a )&0xff), 2900 (int)(u8)((a>>8 )&0xff), 2901 (int)(u8)((a>>16)&0xff), 2902 (int)(u8)((a>>24)&0xff)); 2903 handle = mm_calloc(1, sizeof(*handle)); 2904 if (handle == NULL) 2905 return NULL; 2906 log(EVDNS_LOG_DEBUG, "Resolve requested for %s (reverse)", buf); 2907 EVDNS_LOCK(base); 2908 req = request_new(base, handle, TYPE_PTR, buf, flags, callback, ptr); 2909 if (req) 2910 request_submit(req); 2911 if (handle->current_req == NULL) { 2912 mm_free(handle); 2913 handle = NULL; 2914 } 2915 EVDNS_UNLOCK(base); 2916 return (handle); 2917 } 2918 2919 int evdns_resolve_reverse(const struct in_addr *in, int flags, evdns_callback_type callback, void *ptr) { 2920 return evdns_base_resolve_reverse(current_base, in, flags, callback, ptr) 2921 ? 0 : -1; 2922 } 2923 2924 struct evdns_request * 2925 evdns_base_resolve_reverse_ipv6(struct evdns_base *base, const struct in6_addr *in, int flags, evdns_callback_type callback, void *ptr) { 2926 /* 32 nybbles, 32 periods, "ip6.arpa", NUL. */ 2927 char buf[73]; 2928 char *cp; 2929 struct evdns_request *handle; 2930 struct request *req; 2931 int i; 2932 EVUTIL_ASSERT(in); 2933 cp = buf; 2934 for (i=15; i >= 0; --i) { 2935 u8 byte = in->s6_addr[i]; 2936 *cp++ = "0123456789abcdef"[byte & 0x0f]; 2937 *cp++ = '.'; 2938 *cp++ = "0123456789abcdef"[byte >> 4]; 2939 *cp++ = '.'; 2940 } 2941 EVUTIL_ASSERT(cp + strlen("ip6.arpa") < buf+sizeof(buf)); 2942 memcpy(cp, "ip6.arpa", strlen("ip6.arpa")+1); 2943 handle = mm_calloc(1, sizeof(*handle)); 2944 if (handle == NULL) 2945 return NULL; 2946 log(EVDNS_LOG_DEBUG, "Resolve requested for %s (reverse)", buf); 2947 EVDNS_LOCK(base); 2948 req = request_new(base, handle, TYPE_PTR, buf, flags, callback, ptr); 2949 if (req) 2950 request_submit(req); 2951 if (handle->current_req == NULL) { 2952 mm_free(handle); 2953 handle = NULL; 2954 } 2955 EVDNS_UNLOCK(base); 2956 return (handle); 2957 } 2958 2959 int evdns_resolve_reverse_ipv6(const struct in6_addr *in, int flags, evdns_callback_type callback, void *ptr) { 2960 return evdns_base_resolve_reverse_ipv6(current_base, in, flags, callback, ptr) 2961 ? 0 : -1; 2962 } 2963 2964 /* ================================================================= */ 2965 /* Search support */ 2966 /* */ 2967 /* the libc resolver has support for searching a number of domains */ 2968 /* to find a name. If nothing else then it takes the single domain */ 2969 /* from the gethostname() call. */ 2970 /* */ 2971 /* It can also be configured via the domain and search options in a */ 2972 /* resolv.conf. */ 2973 /* */ 2974 /* The ndots option controls how many dots it takes for the resolver */ 2975 /* to decide that a name is non-local and so try a raw lookup first. */ 2976 2977 struct search_domain { 2978 int len; 2979 struct search_domain *next; 2980 /* the text string is appended to this structure */ 2981 }; 2982 2983 struct search_state { 2984 int refcount; 2985 int ndots; 2986 int num_domains; 2987 struct search_domain *head; 2988 }; 2989 2990 static void 2991 search_state_decref(struct search_state *const state) { 2992 if (!state) return; 2993 state->refcount--; 2994 if (!state->refcount) { 2995 struct search_domain *next, *dom; 2996 for (dom = state->head; dom; dom = next) { 2997 next = dom->next; 2998 mm_free(dom); 2999 } 3000 mm_free(state); 3001 } 3002 } 3003 3004 static struct search_state * 3005 search_state_new(void) { 3006 struct search_state *state = (struct search_state *) mm_malloc(sizeof(struct search_state)); 3007 if (!state) return NULL; 3008 memset(state, 0, sizeof(struct search_state)); 3009 state->refcount = 1; 3010 state->ndots = 1; 3011 3012 return state; 3013 } 3014 3015 static void 3016 search_postfix_clear(struct evdns_base *base) { 3017 search_state_decref(base->global_search_state); 3018 3019 base->global_search_state = search_state_new(); 3020 } 3021 3022 /* exported function */ 3023 void 3024 evdns_base_search_clear(struct evdns_base *base) 3025 { 3026 EVDNS_LOCK(base); 3027 search_postfix_clear(base); 3028 EVDNS_UNLOCK(base); 3029 } 3030 3031 void 3032 evdns_search_clear(void) { 3033 evdns_base_search_clear(current_base); 3034 } 3035 3036 static void 3037 search_postfix_add(struct evdns_base *base, const char *domain) { 3038 size_t domain_len; 3039 struct search_domain *sdomain; 3040 while (domain[0] == '.') domain++; 3041 domain_len = strlen(domain); 3042 3043 ASSERT_LOCKED(base); 3044 if (!base->global_search_state) base->global_search_state = search_state_new(); 3045 if (!base->global_search_state) return; 3046 base->global_search_state->num_domains++; 3047 3048 sdomain = (struct search_domain *) mm_malloc(sizeof(struct search_domain) + domain_len); 3049 if (!sdomain) return; 3050 memcpy( ((u8 *) sdomain) + sizeof(struct search_domain), domain, domain_len); 3051 sdomain->next = base->global_search_state->head; 3052 sdomain->len = (int) domain_len; 3053 3054 base->global_search_state->head = sdomain; 3055 } 3056 3057 /* reverse the order of members in the postfix list. This is needed because, */ 3058 /* when parsing resolv.conf we push elements in the wrong order */ 3059 static void 3060 search_reverse(struct evdns_base *base) { 3061 struct search_domain *cur, *prev = NULL, *next; 3062 ASSERT_LOCKED(base); 3063 cur = base->global_search_state->head; 3064 while (cur) { 3065 next = cur->next; 3066 cur->next = prev; 3067 prev = cur; 3068 cur = next; 3069 } 3070 3071 base->global_search_state->head = prev; 3072 } 3073 3074 /* exported function */ 3075 void 3076 evdns_base_search_add(struct evdns_base *base, const char *domain) { 3077 EVDNS_LOCK(base); 3078 search_postfix_add(base, domain); 3079 EVDNS_UNLOCK(base); 3080 } 3081 void 3082 evdns_search_add(const char *domain) { 3083 evdns_base_search_add(current_base, domain); 3084 } 3085 3086 /* exported function */ 3087 void 3088 evdns_base_search_ndots_set(struct evdns_base *base, const int ndots) { 3089 EVDNS_LOCK(base); 3090 if (!base->global_search_state) base->global_search_state = search_state_new(); 3091 if (base->global_search_state) 3092 base->global_search_state->ndots = ndots; 3093 EVDNS_UNLOCK(base); 3094 } 3095 void 3096 evdns_search_ndots_set(const int ndots) { 3097 evdns_base_search_ndots_set(current_base, ndots); 3098 } 3099 3100 static void 3101 search_set_from_hostname(struct evdns_base *base) { 3102 char hostname[HOST_NAME_MAX + 1], *domainname; 3103 3104 ASSERT_LOCKED(base); 3105 search_postfix_clear(base); 3106 if (gethostname(hostname, sizeof(hostname))) return; 3107 domainname = strchr(hostname, '.'); 3108 if (!domainname) return; 3109 search_postfix_add(base, domainname); 3110 } 3111 3112 /* warning: returns malloced string */ 3113 static char * 3114 search_make_new(const struct search_state *const state, int n, const char *const base_name) { 3115 const size_t base_len = strlen(base_name); 3116 const char need_to_append_dot = base_name[base_len - 1] == '.' ? 0 : 1; 3117 struct search_domain *dom; 3118 3119 for (dom = state->head; dom; dom = dom->next) { 3120 if (!n--) { 3121 /* this is the postfix we want */ 3122 /* the actual postfix string is kept at the end of the structure */ 3123 const u8 *const postfix = ((u8 *) dom) + sizeof(struct search_domain); 3124 const int postfix_len = dom->len; 3125 char *const newname = (char *) mm_malloc(base_len + need_to_append_dot + postfix_len + 1); 3126 if (!newname) return NULL; 3127 memcpy(newname, base_name, base_len); 3128 if (need_to_append_dot) newname[base_len] = '.'; 3129 memcpy(newname + base_len + need_to_append_dot, postfix, postfix_len); 3130 newname[base_len + need_to_append_dot + postfix_len] = 0; 3131 return newname; 3132 } 3133 } 3134 3135 /* we ran off the end of the list and still didn't find the requested string */ 3136 EVUTIL_ASSERT(0); 3137 return NULL; /* unreachable; stops warnings in some compilers. */ 3138 } 3139 3140 static struct request * 3141 search_request_new(struct evdns_base *base, struct evdns_request *handle, 3142 int type, const char *const name, int flags, 3143 evdns_callback_type user_callback, void *user_arg) { 3144 ASSERT_LOCKED(base); 3145 EVUTIL_ASSERT(type == TYPE_A || type == TYPE_AAAA); 3146 EVUTIL_ASSERT(handle->current_req == NULL); 3147 if ( ((flags & DNS_QUERY_NO_SEARCH) == 0) && 3148 base->global_search_state && 3149 base->global_search_state->num_domains) { 3150 /* we have some domains to search */ 3151 struct request *req; 3152 if (string_num_dots(name) >= base->global_search_state->ndots) { 3153 req = request_new(base, handle, type, name, flags, user_callback, user_arg); 3154 if (!req) return NULL; 3155 handle->search_index = -1; 3156 } else { 3157 char *const new_name = search_make_new(base->global_search_state, 0, name); 3158 if (!new_name) return NULL; 3159 req = request_new(base, handle, type, new_name, flags, user_callback, user_arg); 3160 mm_free(new_name); 3161 if (!req) return NULL; 3162 handle->search_index = 0; 3163 } 3164 EVUTIL_ASSERT(handle->search_origname == NULL); 3165 handle->search_origname = mm_strdup(name); 3166 if (handle->search_origname == NULL) { 3167 /* XXX Should we dealloc req? If yes, how? */ 3168 if (req) 3169 mm_free(req); 3170 return NULL; 3171 } 3172 handle->search_state = base->global_search_state; 3173 handle->search_flags = flags; 3174 base->global_search_state->refcount++; 3175 request_submit(req); 3176 return req; 3177 } else { 3178 struct request *const req = request_new(base, handle, type, name, flags, user_callback, user_arg); 3179 if (!req) return NULL; 3180 request_submit(req); 3181 return req; 3182 } 3183 } 3184 3185 /* this is called when a request has failed to find a name. We need to check */ 3186 /* if it is part of a search and, if so, try the next name in the list */ 3187 /* returns: */ 3188 /* 0 another request has been submitted */ 3189 /* 1 no more requests needed */ 3190 static int 3191 search_try_next(struct evdns_request *const handle) { 3192 struct request *req = handle->current_req; 3193 struct evdns_base *base = req->base; 3194 struct request *newreq; 3195 ASSERT_LOCKED(base); 3196 if (handle->search_state) { 3197 /* it is part of a search */ 3198 char *new_name; 3199 handle->search_index++; 3200 if (handle->search_index >= handle->search_state->num_domains) { 3201 /* no more postfixes to try, however we may need to try */ 3202 /* this name without a postfix */ 3203 if (string_num_dots(handle->search_origname) < handle->search_state->ndots) { 3204 /* yep, we need to try it raw */ 3205 newreq = request_new(base, NULL, req->request_type, handle->search_origname, handle->search_flags, req->user_callback, req->user_pointer); 3206 log(EVDNS_LOG_DEBUG, "Search: trying raw query %s", handle->search_origname); 3207 if (newreq) { 3208 search_request_finished(handle); 3209 goto submit_next; 3210 } 3211 } 3212 return 1; 3213 } 3214 3215 new_name = search_make_new(handle->search_state, handle->search_index, handle->search_origname); 3216 if (!new_name) return 1; 3217 log(EVDNS_LOG_DEBUG, "Search: now trying %s (%d)", new_name, handle->search_index); 3218 newreq = request_new(base, NULL, req->request_type, new_name, handle->search_flags, req->user_callback, req->user_pointer); 3219 mm_free(new_name); 3220 if (!newreq) return 1; 3221 goto submit_next; 3222 } 3223 return 1; 3224 3225 submit_next: 3226 request_finished(req, &REQ_HEAD(req->base, req->trans_id), 0); 3227 handle->current_req = newreq; 3228 newreq->handle = handle; 3229 request_submit(newreq); 3230 return 0; 3231 } 3232 3233 static void 3234 search_request_finished(struct evdns_request *const handle) { 3235 ASSERT_LOCKED(handle->current_req->base); 3236 if (handle->search_state) { 3237 search_state_decref(handle->search_state); 3238 handle->search_state = NULL; 3239 } 3240 if (handle->search_origname) { 3241 mm_free(handle->search_origname); 3242 handle->search_origname = NULL; 3243 } 3244 } 3245 3246 /* ================================================================= */ 3247 /* Parsing resolv.conf files */ 3248 3249 static void 3250 evdns_resolv_set_defaults(struct evdns_base *base, int flags) { 3251 /* if the file isn't found then we assume a local resolver */ 3252 ASSERT_LOCKED(base); 3253 if (flags & DNS_OPTION_SEARCH) search_set_from_hostname(base); 3254 if (flags & DNS_OPTION_NAMESERVERS) evdns_base_nameserver_ip_add(base,"127.0.0.1"); 3255 } 3256 3257 #ifndef EVENT__HAVE_STRTOK_R 3258 static char * 3259 strtok_r(char *s, const char *delim, char **state) { 3260 char *cp, *start; 3261 start = cp = s ? s : *state; 3262 if (!cp) 3263 return NULL; 3264 while (*cp && !strchr(delim, *cp)) 3265 ++cp; 3266 if (!*cp) { 3267 if (cp == start) 3268 return NULL; 3269 *state = NULL; 3270 return start; 3271 } else { 3272 *cp++ = '\0'; 3273 *state = cp; 3274 return start; 3275 } 3276 } 3277 #endif 3278 3279 /* helper version of atoi which returns -1 on error */ 3280 static int 3281 strtoint(const char *const str) 3282 { 3283 char *endptr; 3284 const int r = strtol(str, &endptr, 10); 3285 if (*endptr) return -1; 3286 return r; 3287 } 3288 3289 /* Parse a number of seconds into a timeval; return -1 on error. */ 3290 static int 3291 strtotimeval(const char *const str, struct timeval *out) 3292 { 3293 double d; 3294 char *endptr; 3295 d = strtod(str, &endptr); 3296 if (*endptr) return -1; 3297 if (d < 0) return -1; 3298 out->tv_sec = (int) d; 3299 out->tv_usec = (int) ((d - (int) d)*1000000); 3300 if (out->tv_sec == 0 && out->tv_usec < 1000) /* less than 1 msec */ 3301 return -1; 3302 return 0; 3303 } 3304 3305 /* helper version of atoi that returns -1 on error and clips to bounds. */ 3306 static int 3307 strtoint_clipped(const char *const str, int min, int max) 3308 { 3309 int r = strtoint(str); 3310 if (r == -1) 3311 return r; 3312 else if (r<min) 3313 return min; 3314 else if (r>max) 3315 return max; 3316 else 3317 return r; 3318 } 3319 3320 static int 3321 evdns_base_set_max_requests_inflight(struct evdns_base *base, int maxinflight) 3322 { 3323 int old_n_heads = base->n_req_heads, n_heads; 3324 struct request **old_heads = base->req_heads, **new_heads, *req; 3325 int i; 3326 3327 ASSERT_LOCKED(base); 3328 if (maxinflight < 1) 3329 maxinflight = 1; 3330 n_heads = (maxinflight+4) / 5; 3331 EVUTIL_ASSERT(n_heads > 0); 3332 new_heads = mm_calloc(n_heads, sizeof(struct request*)); 3333 if (!new_heads) 3334 return (-1); 3335 if (old_heads) { 3336 for (i = 0; i < old_n_heads; ++i) { 3337 while (old_heads[i]) { 3338 req = old_heads[i]; 3339 evdns_request_remove(req, &old_heads[i]); 3340 evdns_request_insert(req, &new_heads[req->trans_id % n_heads]); 3341 } 3342 } 3343 mm_free(old_heads); 3344 } 3345 base->req_heads = new_heads; 3346 base->n_req_heads = n_heads; 3347 base->global_max_requests_inflight = maxinflight; 3348 return (0); 3349 } 3350 3351 /* exported function */ 3352 int 3353 evdns_base_set_option(struct evdns_base *base, 3354 const char *option, const char *val) 3355 { 3356 int res; 3357 EVDNS_LOCK(base); 3358 res = evdns_base_set_option_impl(base, option, val, DNS_OPTIONS_ALL); 3359 EVDNS_UNLOCK(base); 3360 return res; 3361 } 3362 3363 static inline int 3364 str_matches_option(const char *s1, const char *optionname) 3365 { 3366 /* Option names are given as "option:" We accept either 'option' in 3367 * s1, or 'option:randomjunk'. The latter form is to implement the 3368 * resolv.conf parser. */ 3369 size_t optlen = strlen(optionname); 3370 size_t slen = strlen(s1); 3371 if (slen == optlen || slen == optlen - 1) 3372 return !strncmp(s1, optionname, slen); 3373 else if (slen > optlen) 3374 return !strncmp(s1, optionname, optlen); 3375 else 3376 return 0; 3377 } 3378 3379 static int 3380 evdns_base_set_option_impl(struct evdns_base *base, 3381 const char *option, const char *val, int flags) 3382 { 3383 ASSERT_LOCKED(base); 3384 if (str_matches_option(option, "ndots:")) { 3385 const int ndots = strtoint(val); 3386 if (ndots == -1) return -1; 3387 if (!(flags & DNS_OPTION_SEARCH)) return 0; 3388 log(EVDNS_LOG_DEBUG, "Setting ndots to %d", ndots); 3389 if (!base->global_search_state) base->global_search_state = search_state_new(); 3390 if (!base->global_search_state) return -1; 3391 base->global_search_state->ndots = ndots; 3392 } else if (str_matches_option(option, "timeout:")) { 3393 struct timeval tv; 3394 if (strtotimeval(val, &tv) == -1) return -1; 3395 if (!(flags & DNS_OPTION_MISC)) return 0; 3396 log(EVDNS_LOG_DEBUG, "Setting timeout to %s", val); 3397 memcpy(&base->global_timeout, &tv, sizeof(struct timeval)); 3398 } else if (str_matches_option(option, "getaddrinfo-allow-skew:")) { 3399 struct timeval tv; 3400 if (strtotimeval(val, &tv) == -1) return -1; 3401 if (!(flags & DNS_OPTION_MISC)) return 0; 3402 log(EVDNS_LOG_DEBUG, "Setting getaddrinfo-allow-skew to %s", 3403 val); 3404 memcpy(&base->global_getaddrinfo_allow_skew, &tv, 3405 sizeof(struct timeval)); 3406 } else if (str_matches_option(option, "max-timeouts:")) { 3407 const int maxtimeout = strtoint_clipped(val, 1, 255); 3408 if (maxtimeout == -1) return -1; 3409 if (!(flags & DNS_OPTION_MISC)) return 0; 3410 log(EVDNS_LOG_DEBUG, "Setting maximum allowed timeouts to %d", 3411 maxtimeout); 3412 base->global_max_nameserver_timeout = maxtimeout; 3413 } else if (str_matches_option(option, "max-inflight:")) { 3414 const int maxinflight = strtoint_clipped(val, 1, 65000); 3415 if (maxinflight == -1) return -1; 3416 if (!(flags & DNS_OPTION_MISC)) return 0; 3417 log(EVDNS_LOG_DEBUG, "Setting maximum inflight requests to %d", 3418 maxinflight); 3419 evdns_base_set_max_requests_inflight(base, maxinflight); 3420 } else if (str_matches_option(option, "attempts:")) { 3421 int retries = strtoint(val); 3422 if (retries == -1) return -1; 3423 if (retries > 255) retries = 255; 3424 if (!(flags & DNS_OPTION_MISC)) return 0; 3425 log(EVDNS_LOG_DEBUG, "Setting retries to %d", retries); 3426 base->global_max_retransmits = retries; 3427 } else if (str_matches_option(option, "randomize-case:")) { 3428 int randcase = strtoint(val); 3429 if (!(flags & DNS_OPTION_MISC)) return 0; 3430 base->global_randomize_case = randcase; 3431 } else if (str_matches_option(option, "bind-to:")) { 3432 /* XXX This only applies to successive nameservers, not 3433 * to already-configured ones. We might want to fix that. */ 3434 int len = sizeof(base->global_outgoing_address); 3435 if (!(flags & DNS_OPTION_NAMESERVERS)) return 0; 3436 if (evutil_parse_sockaddr_port(val, 3437 (struct sockaddr*)&base->global_outgoing_address, &len)) 3438 return -1; 3439 base->global_outgoing_addrlen = len; 3440 } else if (str_matches_option(option, "initial-probe-timeout:")) { 3441 struct timeval tv; 3442 if (strtotimeval(val, &tv) == -1) return -1; 3443 if (tv.tv_sec > 3600) 3444 tv.tv_sec = 3600; 3445 if (!(flags & DNS_OPTION_MISC)) return 0; 3446 log(EVDNS_LOG_DEBUG, "Setting initial probe timeout to %s", 3447 val); 3448 memcpy(&base->global_nameserver_probe_initial_timeout, &tv, 3449 sizeof(tv)); 3450 } 3451 return 0; 3452 } 3453 3454 int 3455 evdns_set_option(const char *option, const char *val, int flags) 3456 { 3457 if (!current_base) 3458 current_base = evdns_base_new(NULL, 0); 3459 return evdns_base_set_option(current_base, option, val); 3460 } 3461 3462 static void 3463 resolv_conf_parse_line(struct evdns_base *base, char *const start, int flags) { 3464 char *strtok_state; 3465 static const char *const delims = " \t"; 3466 #define NEXT_TOKEN strtok_r(NULL, delims, &strtok_state) 3467 3468 3469 char *const first_token = strtok_r(start, delims, &strtok_state); 3470 ASSERT_LOCKED(base); 3471 if (!first_token) return; 3472 3473 if (!strcmp(first_token, "nameserver") && (flags & DNS_OPTION_NAMESERVERS)) { 3474 const char *const nameserver = NEXT_TOKEN; 3475 3476 if (nameserver) 3477 evdns_base_nameserver_ip_add(base, nameserver); 3478 } else if (!strcmp(first_token, "domain") && (flags & DNS_OPTION_SEARCH)) { 3479 const char *const domain = NEXT_TOKEN; 3480 if (domain) { 3481 search_postfix_clear(base); 3482 search_postfix_add(base, domain); 3483 } 3484 } else if (!strcmp(first_token, "search") && (flags & DNS_OPTION_SEARCH)) { 3485 const char *domain; 3486 search_postfix_clear(base); 3487 3488 while ((domain = NEXT_TOKEN)) { 3489 search_postfix_add(base, domain); 3490 } 3491 search_reverse(base); 3492 } else if (!strcmp(first_token, "options")) { 3493 const char *option; 3494 while ((option = NEXT_TOKEN)) { 3495 const char *val = strchr(option, ':'); 3496 evdns_base_set_option_impl(base, option, val ? val+1 : "", flags); 3497 } 3498 } 3499 #undef NEXT_TOKEN 3500 } 3501 3502 /* exported function */ 3503 /* returns: */ 3504 /* 0 no errors */ 3505 /* 1 failed to open file */ 3506 /* 2 failed to stat file */ 3507 /* 3 file too large */ 3508 /* 4 out of memory */ 3509 /* 5 short read from file */ 3510 int 3511 evdns_base_resolv_conf_parse(struct evdns_base *base, int flags, const char *const filename) { 3512 int res; 3513 EVDNS_LOCK(base); 3514 res = evdns_base_resolv_conf_parse_impl(base, flags, filename); 3515 EVDNS_UNLOCK(base); 3516 return res; 3517 } 3518 3519 static char * 3520 evdns_get_default_hosts_filename(void) 3521 { 3522 #ifdef _WIN32 3523 /* Windows is a little coy about where it puts its configuration 3524 * files. Sure, they're _usually_ in C:\windows\system32, but 3525 * there's no reason in principle they couldn't be in 3526 * W:\hoboken chicken emergency\ 3527 */ 3528 char path[MAX_PATH+1]; 3529 static const char hostfile[] = "\\drivers\\etc\\hosts"; 3530 char *path_out; 3531 size_t len_out; 3532 3533 if (! SHGetSpecialFolderPathA(NULL, path, CSIDL_SYSTEM, 0)) 3534 return NULL; 3535 len_out = strlen(path)+strlen(hostfile); 3536 path_out = mm_malloc(len_out+1); 3537 evutil_snprintf(path_out, len_out, "%s%s", path, hostfile); 3538 return path_out; 3539 #else 3540 return mm_strdup("/etc/hosts"); 3541 #endif 3542 } 3543 3544 static int 3545 evdns_base_resolv_conf_parse_impl(struct evdns_base *base, int flags, const char *const filename) { 3546 size_t n; 3547 char *resolv; 3548 char *start; 3549 int err = 0; 3550 3551 log(EVDNS_LOG_DEBUG, "Parsing resolv.conf file %s", filename); 3552 3553 if (flags & DNS_OPTION_HOSTSFILE) { 3554 char *fname = evdns_get_default_hosts_filename(); 3555 evdns_base_load_hosts(base, fname); 3556 if (fname) 3557 mm_free(fname); 3558 } 3559 3560 if ((err = evutil_read_file_(filename, &resolv, &n, 0)) < 0) { 3561 if (err == -1) { 3562 /* No file. */ 3563 evdns_resolv_set_defaults(base, flags); 3564 return 1; 3565 } else { 3566 return 2; 3567 } 3568 } 3569 3570 start = resolv; 3571 for (;;) { 3572 char *const newline = strchr(start, '\n'); 3573 if (!newline) { 3574 resolv_conf_parse_line(base, start, flags); 3575 break; 3576 } else { 3577 *newline = 0; 3578 resolv_conf_parse_line(base, start, flags); 3579 start = newline + 1; 3580 } 3581 } 3582 3583 if (!base->server_head && (flags & DNS_OPTION_NAMESERVERS)) { 3584 /* no nameservers were configured. */ 3585 evdns_base_nameserver_ip_add(base, "127.0.0.1"); 3586 err = 6; 3587 } 3588 if (flags & DNS_OPTION_SEARCH && (!base->global_search_state || base->global_search_state->num_domains == 0)) { 3589 search_set_from_hostname(base); 3590 } 3591 3592 mm_free(resolv); 3593 return err; 3594 } 3595 3596 int 3597 evdns_resolv_conf_parse(int flags, const char *const filename) { 3598 if (!current_base) 3599 current_base = evdns_base_new(NULL, 0); 3600 return evdns_base_resolv_conf_parse(current_base, flags, filename); 3601 } 3602 3603 3604 #ifdef _WIN32 3605 /* Add multiple nameservers from a space-or-comma-separated list. */ 3606 static int 3607 evdns_nameserver_ip_add_line(struct evdns_base *base, const char *ips) { 3608 const char *addr; 3609 char *buf; 3610 int r; 3611 ASSERT_LOCKED(base); 3612 while (*ips) { 3613 while (isspace(*ips) || *ips == ',' || *ips == '\t') 3614 ++ips; 3615 addr = ips; 3616 while (isdigit(*ips) || *ips == '.' || *ips == ':' || 3617 *ips=='[' || *ips==']') 3618 ++ips; 3619 buf = mm_malloc(ips-addr+1); 3620 if (!buf) return 4; 3621 memcpy(buf, addr, ips-addr); 3622 buf[ips-addr] = '\0'; 3623 r = evdns_base_nameserver_ip_add(base, buf); 3624 mm_free(buf); 3625 if (r) return r; 3626 } 3627 return 0; 3628 } 3629 3630 typedef DWORD(WINAPI *GetNetworkParams_fn_t)(FIXED_INFO *, DWORD*); 3631 3632 /* Use the windows GetNetworkParams interface in iphlpapi.dll to */ 3633 /* figure out what our nameservers are. */ 3634 static int 3635 load_nameservers_with_getnetworkparams(struct evdns_base *base) 3636 { 3637 /* Based on MSDN examples and inspection of c-ares code. */ 3638 FIXED_INFO *fixed; 3639 HMODULE handle = 0; 3640 ULONG size = sizeof(FIXED_INFO); 3641 void *buf = NULL; 3642 int status = 0, r, added_any; 3643 IP_ADDR_STRING *ns; 3644 GetNetworkParams_fn_t fn; 3645 3646 ASSERT_LOCKED(base); 3647 if (!(handle = evutil_load_windows_system_library_( 3648 TEXT("iphlpapi.dll")))) { 3649 log(EVDNS_LOG_WARN, "Could not open iphlpapi.dll"); 3650 status = -1; 3651 goto done; 3652 } 3653 if (!(fn = (GetNetworkParams_fn_t) GetProcAddress(handle, "GetNetworkParams"))) { 3654 log(EVDNS_LOG_WARN, "Could not get address of function."); 3655 status = -1; 3656 goto done; 3657 } 3658 3659 buf = mm_malloc(size); 3660 if (!buf) { status = 4; goto done; } 3661 fixed = buf; 3662 r = fn(fixed, &size); 3663 if (r != ERROR_SUCCESS && r != ERROR_BUFFER_OVERFLOW) { 3664 status = -1; 3665 goto done; 3666 } 3667 if (r != ERROR_SUCCESS) { 3668 mm_free(buf); 3669 buf = mm_malloc(size); 3670 if (!buf) { status = 4; goto done; } 3671 fixed = buf; 3672 r = fn(fixed, &size); 3673 if (r != ERROR_SUCCESS) { 3674 log(EVDNS_LOG_DEBUG, "fn() failed."); 3675 status = -1; 3676 goto done; 3677 } 3678 } 3679 3680 EVUTIL_ASSERT(fixed); 3681 added_any = 0; 3682 ns = &(fixed->DnsServerList); 3683 while (ns) { 3684 r = evdns_nameserver_ip_add_line(base, ns->IpAddress.String); 3685 if (r) { 3686 log(EVDNS_LOG_DEBUG,"Could not add nameserver %s to list,error: %d", 3687 (ns->IpAddress.String),(int)GetLastError()); 3688 status = r; 3689 } else { 3690 ++added_any; 3691 log(EVDNS_LOG_DEBUG,"Successfully added %s as nameserver",ns->IpAddress.String); 3692 } 3693 3694 ns = ns->Next; 3695 } 3696 3697 if (!added_any) { 3698 log(EVDNS_LOG_DEBUG, "No nameservers added."); 3699 if (status == 0) 3700 status = -1; 3701 } else { 3702 status = 0; 3703 } 3704 3705 done: 3706 if (buf) 3707 mm_free(buf); 3708 if (handle) 3709 FreeLibrary(handle); 3710 return status; 3711 } 3712 3713 static int 3714 config_nameserver_from_reg_key(struct evdns_base *base, HKEY key, const TCHAR *subkey) 3715 { 3716 char *buf; 3717 DWORD bufsz = 0, type = 0; 3718 int status = 0; 3719 3720 ASSERT_LOCKED(base); 3721 if (RegQueryValueEx(key, subkey, 0, &type, NULL, &bufsz) 3722 != ERROR_MORE_DATA) 3723 return -1; 3724 if (!(buf = mm_malloc(bufsz))) 3725 return -1; 3726 3727 if (RegQueryValueEx(key, subkey, 0, &type, (LPBYTE)buf, &bufsz) 3728 == ERROR_SUCCESS && bufsz > 1) { 3729 status = evdns_nameserver_ip_add_line(base,buf); 3730 } 3731 3732 mm_free(buf); 3733 return status; 3734 } 3735 3736 #define SERVICES_KEY TEXT("System\\CurrentControlSet\\Services\\") 3737 #define WIN_NS_9X_KEY SERVICES_KEY TEXT("VxD\\MSTCP") 3738 #define WIN_NS_NT_KEY SERVICES_KEY TEXT("Tcpip\\Parameters") 3739 3740 static int 3741 load_nameservers_from_registry(struct evdns_base *base) 3742 { 3743 int found = 0; 3744 int r; 3745 #define TRY(k, name) \ 3746 if (!found && config_nameserver_from_reg_key(base,k,TEXT(name)) == 0) { \ 3747 log(EVDNS_LOG_DEBUG,"Found nameservers in %s/%s",#k,name); \ 3748 found = 1; \ 3749 } else if (!found) { \ 3750 log(EVDNS_LOG_DEBUG,"Didn't find nameservers in %s/%s", \ 3751 #k,#name); \ 3752 } 3753 3754 ASSERT_LOCKED(base); 3755 3756 if (((int)GetVersion()) > 0) { /* NT */ 3757 HKEY nt_key = 0, interfaces_key = 0; 3758 3759 if (RegOpenKeyEx(HKEY_LOCAL_MACHINE, WIN_NS_NT_KEY, 0, 3760 KEY_READ, &nt_key) != ERROR_SUCCESS) { 3761 log(EVDNS_LOG_DEBUG,"Couldn't open nt key, %d",(int)GetLastError()); 3762 return -1; 3763 } 3764 r = RegOpenKeyEx(nt_key, TEXT("Interfaces"), 0, 3765 KEY_QUERY_VALUE|KEY_ENUMERATE_SUB_KEYS, 3766 &interfaces_key); 3767 if (r != ERROR_SUCCESS) { 3768 log(EVDNS_LOG_DEBUG,"Couldn't open interfaces key, %d",(int)GetLastError()); 3769 return -1; 3770 } 3771 TRY(nt_key, "NameServer"); 3772 TRY(nt_key, "DhcpNameServer"); 3773 TRY(interfaces_key, "NameServer"); 3774 TRY(interfaces_key, "DhcpNameServer"); 3775 RegCloseKey(interfaces_key); 3776 RegCloseKey(nt_key); 3777 } else { 3778 HKEY win_key = 0; 3779 if (RegOpenKeyEx(HKEY_LOCAL_MACHINE, WIN_NS_9X_KEY, 0, 3780 KEY_READ, &win_key) != ERROR_SUCCESS) { 3781 log(EVDNS_LOG_DEBUG, "Couldn't open registry key, %d", (int)GetLastError()); 3782 return -1; 3783 } 3784 TRY(win_key, "NameServer"); 3785 RegCloseKey(win_key); 3786 } 3787 3788 if (found == 0) { 3789 log(EVDNS_LOG_WARN,"Didn't find any nameservers."); 3790 } 3791 3792 return found ? 0 : -1; 3793 #undef TRY 3794 } 3795 3796 int 3797 evdns_base_config_windows_nameservers(struct evdns_base *base) 3798 { 3799 int r; 3800 char *fname; 3801 if (base == NULL) 3802 base = current_base; 3803 if (base == NULL) 3804 return -1; 3805 EVDNS_LOCK(base); 3806 if (load_nameservers_with_getnetworkparams(base) == 0) { 3807 EVDNS_UNLOCK(base); 3808 return 0; 3809 } 3810 r = load_nameservers_from_registry(base); 3811 3812 fname = evdns_get_default_hosts_filename(); 3813 evdns_base_load_hosts(base, fname); 3814 if (fname) 3815 mm_free(fname); 3816 3817 EVDNS_UNLOCK(base); 3818 return r; 3819 } 3820 3821 int 3822 evdns_config_windows_nameservers(void) 3823 { 3824 if (!current_base) { 3825 current_base = evdns_base_new(NULL, 1); 3826 return current_base == NULL ? -1 : 0; 3827 } else { 3828 return evdns_base_config_windows_nameservers(current_base); 3829 } 3830 } 3831 #endif 3832 3833 struct evdns_base * 3834 evdns_base_new(struct event_base *event_base, int initialize_nameservers) 3835 { 3836 struct evdns_base *base; 3837 3838 if (evutil_secure_rng_init() < 0) { 3839 log(EVDNS_LOG_WARN, "Unable to seed random number generator; " 3840 "DNS can't run."); 3841 return NULL; 3842 } 3843 3844 /* Give the evutil library a hook into its evdns-enabled 3845 * functionality. We can't just call evdns_getaddrinfo directly or 3846 * else libevent-core will depend on libevent-extras. */ 3847 evutil_set_evdns_getaddrinfo_fn_(evdns_getaddrinfo); 3848 3849 base = mm_malloc(sizeof(struct evdns_base)); 3850 if (base == NULL) 3851 return (NULL); 3852 memset(base, 0, sizeof(struct evdns_base)); 3853 base->req_waiting_head = NULL; 3854 3855 EVTHREAD_ALLOC_LOCK(base->lock, EVTHREAD_LOCKTYPE_RECURSIVE); 3856 EVDNS_LOCK(base); 3857 3858 /* Set max requests inflight and allocate req_heads. */ 3859 base->req_heads = NULL; 3860 3861 evdns_base_set_max_requests_inflight(base, 64); 3862 3863 base->server_head = NULL; 3864 base->event_base = event_base; 3865 base->global_good_nameservers = base->global_requests_inflight = 3866 base->global_requests_waiting = 0; 3867 3868 base->global_timeout.tv_sec = 5; 3869 base->global_timeout.tv_usec = 0; 3870 base->global_max_reissues = 1; 3871 base->global_max_retransmits = 3; 3872 base->global_max_nameserver_timeout = 3; 3873 base->global_search_state = NULL; 3874 base->global_randomize_case = 1; 3875 base->global_getaddrinfo_allow_skew.tv_sec = 3; 3876 base->global_getaddrinfo_allow_skew.tv_usec = 0; 3877 base->global_nameserver_probe_initial_timeout.tv_sec = 10; 3878 base->global_nameserver_probe_initial_timeout.tv_usec = 0; 3879 3880 TAILQ_INIT(&base->hostsdb); 3881 3882 if (initialize_nameservers) { 3883 int r; 3884 #ifdef _WIN32 3885 r = evdns_base_config_windows_nameservers(base); 3886 #else 3887 r = evdns_base_resolv_conf_parse(base, DNS_OPTIONS_ALL, "/etc/resolv.conf"); 3888 #endif 3889 if (r == -1) { 3890 evdns_base_free_and_unlock(base, 0); 3891 return NULL; 3892 } 3893 } 3894 EVDNS_UNLOCK(base); 3895 return base; 3896 } 3897 3898 int 3899 evdns_init(void) 3900 { 3901 struct evdns_base *base = evdns_base_new(NULL, 1); 3902 if (base) { 3903 current_base = base; 3904 return 0; 3905 } else { 3906 return -1; 3907 } 3908 } 3909 3910 const char * 3911 evdns_err_to_string(int err) 3912 { 3913 switch (err) { 3914 case DNS_ERR_NONE: return "no error"; 3915 case DNS_ERR_FORMAT: return "misformatted query"; 3916 case DNS_ERR_SERVERFAILED: return "server failed"; 3917 case DNS_ERR_NOTEXIST: return "name does not exist"; 3918 case DNS_ERR_NOTIMPL: return "query not implemented"; 3919 case DNS_ERR_REFUSED: return "refused"; 3920 3921 case DNS_ERR_TRUNCATED: return "reply truncated or ill-formed"; 3922 case DNS_ERR_UNKNOWN: return "unknown"; 3923 case DNS_ERR_TIMEOUT: return "request timed out"; 3924 case DNS_ERR_SHUTDOWN: return "dns subsystem shut down"; 3925 case DNS_ERR_CANCEL: return "dns request canceled"; 3926 case DNS_ERR_NODATA: return "no records in the reply"; 3927 default: return "[Unknown error code]"; 3928 } 3929 } 3930 3931 static void 3932 evdns_nameserver_free(struct nameserver *server) 3933 { 3934 if (server->socket >= 0) 3935 evutil_closesocket(server->socket); 3936 (void) event_del(&server->event); 3937 event_debug_unassign(&server->event); 3938 if (server->state == 0) 3939 (void) event_del(&server->timeout_event); 3940 event_debug_unassign(&server->timeout_event); 3941 mm_free(server); 3942 } 3943 3944 static void 3945 evdns_base_free_and_unlock(struct evdns_base *base, int fail_requests) 3946 { 3947 struct nameserver *server, *server_next; 3948 struct search_domain *dom, *dom_next; 3949 int i; 3950 3951 /* Requires that we hold the lock. */ 3952 3953 /* TODO(nickm) we might need to refcount here. */ 3954 3955 for (i = 0; i < base->n_req_heads; ++i) { 3956 while (base->req_heads[i]) { 3957 if (fail_requests) 3958 reply_schedule_callback(base->req_heads[i], 0, DNS_ERR_SHUTDOWN, NULL); 3959 request_finished(base->req_heads[i], &REQ_HEAD(base, base->req_heads[i]->trans_id), 1); 3960 } 3961 } 3962 while (base->req_waiting_head) { 3963 if (fail_requests) 3964 reply_schedule_callback(base->req_waiting_head, 0, DNS_ERR_SHUTDOWN, NULL); 3965 request_finished(base->req_waiting_head, &base->req_waiting_head, 1); 3966 } 3967 base->global_requests_inflight = base->global_requests_waiting = 0; 3968 3969 for (server = base->server_head; server; server = server_next) { 3970 server_next = server->next; 3971 evdns_nameserver_free(server); 3972 if (server_next == base->server_head) 3973 break; 3974 } 3975 base->server_head = NULL; 3976 base->global_good_nameservers = 0; 3977 3978 if (base->global_search_state) { 3979 for (dom = base->global_search_state->head; dom; dom = dom_next) { 3980 dom_next = dom->next; 3981 mm_free(dom); 3982 } 3983 mm_free(base->global_search_state); 3984 base->global_search_state = NULL; 3985 } 3986 3987 { 3988 struct hosts_entry *victim; 3989 while ((victim = TAILQ_FIRST(&base->hostsdb))) { 3990 TAILQ_REMOVE(&base->hostsdb, victim, next); 3991 mm_free(victim); 3992 } 3993 } 3994 3995 mm_free(base->req_heads); 3996 3997 EVDNS_UNLOCK(base); 3998 EVTHREAD_FREE_LOCK(base->lock, EVTHREAD_LOCKTYPE_RECURSIVE); 3999 4000 mm_free(base); 4001 } 4002 4003 void 4004 evdns_base_free(struct evdns_base *base, int fail_requests) 4005 { 4006 EVDNS_LOCK(base); 4007 evdns_base_free_and_unlock(base, fail_requests); 4008 } 4009 4010 void 4011 evdns_shutdown(int fail_requests) 4012 { 4013 if (current_base) { 4014 struct evdns_base *b = current_base; 4015 current_base = NULL; 4016 evdns_base_free(b, fail_requests); 4017 } 4018 evdns_log_fn = NULL; 4019 } 4020 4021 static int 4022 evdns_base_parse_hosts_line(struct evdns_base *base, char *line) 4023 { 4024 char *strtok_state; 4025 static const char *const delims = " \t"; 4026 char *const addr = strtok_r(line, delims, &strtok_state); 4027 char *hostname, *hash; 4028 struct sockaddr_storage ss; 4029 int socklen = sizeof(ss); 4030 ASSERT_LOCKED(base); 4031 4032 #define NEXT_TOKEN strtok_r(NULL, delims, &strtok_state) 4033 4034 if (!addr || *addr == '#') 4035 return 0; 4036 4037 memset(&ss, 0, sizeof(ss)); 4038 if (evutil_parse_sockaddr_port(addr, (struct sockaddr*)&ss, &socklen)<0) 4039 return -1; 4040 if (socklen > (int)sizeof(struct sockaddr_in6)) 4041 return -1; 4042 4043 if (sockaddr_getport((struct sockaddr*)&ss)) 4044 return -1; 4045 4046 while ((hostname = NEXT_TOKEN)) { 4047 struct hosts_entry *he; 4048 size_t namelen; 4049 if ((hash = strchr(hostname, '#'))) { 4050 if (hash == hostname) 4051 return 0; 4052 *hash = '\0'; 4053 } 4054 4055 namelen = strlen(hostname); 4056 4057 he = mm_calloc(1, sizeof(struct hosts_entry)+namelen); 4058 if (!he) 4059 return -1; 4060 EVUTIL_ASSERT(socklen <= (int)sizeof(he->addr)); 4061 memcpy(&he->addr, &ss, socklen); 4062 memcpy(he->hostname, hostname, namelen+1); 4063 he->addrlen = socklen; 4064 4065 TAILQ_INSERT_TAIL(&base->hostsdb, he, next); 4066 4067 if (hash) 4068 return 0; 4069 } 4070 4071 return 0; 4072 #undef NEXT_TOKEN 4073 } 4074 4075 static int 4076 evdns_base_load_hosts_impl(struct evdns_base *base, const char *hosts_fname) 4077 { 4078 char *str=NULL, *cp, *eol; 4079 size_t len; 4080 int err=0; 4081 4082 ASSERT_LOCKED(base); 4083 4084 if (hosts_fname == NULL || 4085 (err = evutil_read_file_(hosts_fname, &str, &len, 0)) < 0) { 4086 char tmp[64]; 4087 strlcpy(tmp, "127.0.0.1 localhost", sizeof(tmp)); 4088 evdns_base_parse_hosts_line(base, tmp); 4089 strlcpy(tmp, "::1 localhost", sizeof(tmp)); 4090 evdns_base_parse_hosts_line(base, tmp); 4091 return err ? -1 : 0; 4092 } 4093 4094 /* This will break early if there is a NUL in the hosts file. 4095 * Probably not a problem.*/ 4096 cp = str; 4097 for (;;) { 4098 eol = strchr(cp, '\n'); 4099 4100 if (eol) { 4101 *eol = '\0'; 4102 evdns_base_parse_hosts_line(base, cp); 4103 cp = eol+1; 4104 } else { 4105 evdns_base_parse_hosts_line(base, cp); 4106 break; 4107 } 4108 } 4109 4110 mm_free(str); 4111 return 0; 4112 } 4113 4114 int 4115 evdns_base_load_hosts(struct evdns_base *base, const char *hosts_fname) 4116 { 4117 int res; 4118 if (!base) 4119 base = current_base; 4120 EVDNS_LOCK(base); 4121 res = evdns_base_load_hosts_impl(base, hosts_fname); 4122 EVDNS_UNLOCK(base); 4123 return res; 4124 } 4125 4126 /* A single request for a getaddrinfo, either v4 or v6. */ 4127 struct getaddrinfo_subrequest { 4128 struct evdns_request *r; 4129 ev_uint32_t type; 4130 }; 4131 4132 /* State data used to implement an in-progress getaddrinfo. */ 4133 struct evdns_getaddrinfo_request { 4134 struct evdns_base *evdns_base; 4135 /* Copy of the modified 'hints' data that we'll use to build 4136 * answers. */ 4137 struct evutil_addrinfo hints; 4138 /* The callback to invoke when we're done */ 4139 evdns_getaddrinfo_cb user_cb; 4140 /* User-supplied data to give to the callback. */ 4141 void *user_data; 4142 /* The port to use when building sockaddrs. */ 4143 ev_uint16_t port; 4144 /* The sub_request for an A record (if any) */ 4145 struct getaddrinfo_subrequest ipv4_request; 4146 /* The sub_request for an AAAA record (if any) */ 4147 struct getaddrinfo_subrequest ipv6_request; 4148 4149 /* The cname result that we were told (if any) */ 4150 char *cname_result; 4151 4152 /* If we have one request answered and one request still inflight, 4153 * then this field holds the answer from the first request... */ 4154 struct evutil_addrinfo *pending_result; 4155 /* And this event is a timeout that will tell us to cancel the second 4156 * request if it's taking a long time. */ 4157 struct event timeout; 4158 4159 /* And this field holds the error code from the first request... */ 4160 int pending_error; 4161 /* If this is set, the user canceled this request. */ 4162 unsigned user_canceled : 1; 4163 /* If this is set, the user can no longer cancel this request; we're 4164 * just waiting for the free. */ 4165 unsigned request_done : 1; 4166 }; 4167 4168 /* Convert an evdns errors to the equivalent getaddrinfo error. */ 4169 static int 4170 evdns_err_to_getaddrinfo_err(int e1) 4171 { 4172 /* XXX Do this better! */ 4173 if (e1 == DNS_ERR_NONE) 4174 return 0; 4175 else if (e1 == DNS_ERR_NOTEXIST) 4176 return EVUTIL_EAI_NONAME; 4177 else 4178 return EVUTIL_EAI_FAIL; 4179 } 4180 4181 /* Return the more informative of two getaddrinfo errors. */ 4182 static int 4183 getaddrinfo_merge_err(int e1, int e2) 4184 { 4185 /* XXXX be cleverer here. */ 4186 if (e1 == 0) 4187 return e2; 4188 else 4189 return e1; 4190 } 4191 4192 static void 4193 free_getaddrinfo_request(struct evdns_getaddrinfo_request *data) 4194 { 4195 /* DO NOT CALL this if either of the requests is pending. Only once 4196 * both callbacks have been invoked is it safe to free the request */ 4197 if (data->pending_result) 4198 evutil_freeaddrinfo(data->pending_result); 4199 if (data->cname_result) 4200 mm_free(data->cname_result); 4201 event_del(&data->timeout); 4202 mm_free(data); 4203 return; 4204 } 4205 4206 static void 4207 add_cname_to_reply(struct evdns_getaddrinfo_request *data, 4208 struct evutil_addrinfo *ai) 4209 { 4210 if (data->cname_result && ai) { 4211 ai->ai_canonname = data->cname_result; 4212 data->cname_result = NULL; 4213 } 4214 } 4215 4216 /* Callback: invoked when one request in a mixed-format A/AAAA getaddrinfo 4217 * request has finished, but the other one took too long to answer. Pass 4218 * along the answer we got, and cancel the other request. 4219 */ 4220 static void 4221 evdns_getaddrinfo_timeout_cb(evutil_socket_t fd, short what, void *ptr) 4222 { 4223 int v4_timedout = 0, v6_timedout = 0; 4224 struct evdns_getaddrinfo_request *data = ptr; 4225 4226 /* Cancel any pending requests, and note which one */ 4227 if (data->ipv4_request.r) { 4228 /* XXXX This does nothing if the request's callback is already 4229 * running (pending_cb is set). */ 4230 evdns_cancel_request(NULL, data->ipv4_request.r); 4231 v4_timedout = 1; 4232 EVDNS_LOCK(data->evdns_base); 4233 ++data->evdns_base->getaddrinfo_ipv4_timeouts; 4234 EVDNS_UNLOCK(data->evdns_base); 4235 } 4236 if (data->ipv6_request.r) { 4237 /* XXXX This does nothing if the request's callback is already 4238 * running (pending_cb is set). */ 4239 evdns_cancel_request(NULL, data->ipv6_request.r); 4240 v6_timedout = 1; 4241 EVDNS_LOCK(data->evdns_base); 4242 ++data->evdns_base->getaddrinfo_ipv6_timeouts; 4243 EVDNS_UNLOCK(data->evdns_base); 4244 } 4245 4246 /* We only use this timeout callback when we have an answer for 4247 * one address. */ 4248 EVUTIL_ASSERT(!v4_timedout || !v6_timedout); 4249 4250 /* Report the outcome of the other request that didn't time out. */ 4251 if (data->pending_result) { 4252 add_cname_to_reply(data, data->pending_result); 4253 data->user_cb(0, data->pending_result, data->user_data); 4254 data->pending_result = NULL; 4255 } else { 4256 int e = data->pending_error; 4257 if (!e) 4258 e = EVUTIL_EAI_AGAIN; 4259 data->user_cb(e, NULL, data->user_data); 4260 } 4261 4262 data->user_cb = NULL; /* prevent double-call if evdns callbacks are 4263 * in-progress. XXXX It would be better if this 4264 * weren't necessary. */ 4265 4266 if (!v4_timedout && !v6_timedout) { 4267 /* should be impossible? XXXX */ 4268 free_getaddrinfo_request(data); 4269 } 4270 } 4271 4272 static int 4273 evdns_getaddrinfo_set_timeout(struct evdns_base *evdns_base, 4274 struct evdns_getaddrinfo_request *data) 4275 { 4276 return event_add(&data->timeout, &evdns_base->global_getaddrinfo_allow_skew); 4277 } 4278 4279 static inline int 4280 evdns_result_is_answer(int result) 4281 { 4282 return (result != DNS_ERR_NOTIMPL && result != DNS_ERR_REFUSED && 4283 result != DNS_ERR_SERVERFAILED && result != DNS_ERR_CANCEL); 4284 } 4285 4286 static void 4287 evdns_getaddrinfo_gotresolve(int result, char type, int count, 4288 int ttl, void *addresses, void *arg) 4289 { 4290 int i; 4291 struct getaddrinfo_subrequest *req = arg; 4292 struct getaddrinfo_subrequest *other_req; 4293 struct evdns_getaddrinfo_request *data; 4294 4295 struct evutil_addrinfo *res; 4296 4297 struct sockaddr_in sin; 4298 struct sockaddr_in6 sin6; 4299 struct sockaddr *sa; 4300 int socklen, addrlen; 4301 void *addrp; 4302 int err; 4303 int user_canceled; 4304 4305 EVUTIL_ASSERT(req->type == DNS_IPv4_A || req->type == DNS_IPv6_AAAA); 4306 if (req->type == DNS_IPv4_A) { 4307 data = EVUTIL_UPCAST(req, struct evdns_getaddrinfo_request, ipv4_request); 4308 other_req = &data->ipv6_request; 4309 } else { 4310 data = EVUTIL_UPCAST(req, struct evdns_getaddrinfo_request, ipv6_request); 4311 other_req = &data->ipv4_request; 4312 } 4313 4314 EVDNS_LOCK(data->evdns_base); 4315 if (evdns_result_is_answer(result)) { 4316 if (req->type == DNS_IPv4_A) 4317 ++data->evdns_base->getaddrinfo_ipv4_answered; 4318 else 4319 ++data->evdns_base->getaddrinfo_ipv6_answered; 4320 } 4321 user_canceled = data->user_canceled; 4322 if (other_req->r == NULL) 4323 data->request_done = 1; 4324 EVDNS_UNLOCK(data->evdns_base); 4325 4326 req->r = NULL; 4327 4328 if (result == DNS_ERR_CANCEL && ! user_canceled) { 4329 /* Internal cancel request from timeout or internal error. 4330 * we already answered the user. */ 4331 if (other_req->r == NULL) 4332 free_getaddrinfo_request(data); 4333 return; 4334 } 4335 4336 if (data->user_cb == NULL) { 4337 /* We already answered. XXXX This shouldn't be needed; see 4338 * comments in evdns_getaddrinfo_timeout_cb */ 4339 free_getaddrinfo_request(data); 4340 return; 4341 } 4342 4343 if (result == DNS_ERR_NONE) { 4344 if (count == 0) 4345 err = EVUTIL_EAI_NODATA; 4346 else 4347 err = 0; 4348 } else { 4349 err = evdns_err_to_getaddrinfo_err(result); 4350 } 4351 4352 if (err) { 4353 /* Looks like we got an error. */ 4354 if (other_req->r) { 4355 /* The other request is still working; maybe it will 4356 * succeed. */ 4357 /* XXXX handle failure from set_timeout */ 4358 evdns_getaddrinfo_set_timeout(data->evdns_base, data); 4359 data->pending_error = err; 4360 return; 4361 } 4362 4363 if (user_canceled) { 4364 data->user_cb(EVUTIL_EAI_CANCEL, NULL, data->user_data); 4365 } else if (data->pending_result) { 4366 /* If we have an answer waiting, and we weren't 4367 * canceled, ignore this error. */ 4368 add_cname_to_reply(data, data->pending_result); 4369 data->user_cb(0, data->pending_result, data->user_data); 4370 data->pending_result = NULL; 4371 } else { 4372 if (data->pending_error) 4373 err = getaddrinfo_merge_err(err, 4374 data->pending_error); 4375 data->user_cb(err, NULL, data->user_data); 4376 } 4377 free_getaddrinfo_request(data); 4378 return; 4379 } else if (user_canceled) { 4380 if (other_req->r) { 4381 /* The other request is still working; let it hit this 4382 * callback with EVUTIL_EAI_CANCEL callback and report 4383 * the failure. */ 4384 return; 4385 } 4386 data->user_cb(EVUTIL_EAI_CANCEL, NULL, data->user_data); 4387 free_getaddrinfo_request(data); 4388 return; 4389 } 4390 4391 /* Looks like we got some answers. We should turn them into addrinfos 4392 * and then either queue those or return them all. */ 4393 EVUTIL_ASSERT(type == DNS_IPv4_A || type == DNS_IPv6_AAAA); 4394 4395 if (type == DNS_IPv4_A) { 4396 memset(&sin, 0, sizeof(sin)); 4397 sin.sin_family = AF_INET; 4398 sin.sin_port = htons(data->port); 4399 4400 sa = (struct sockaddr *)&sin; 4401 socklen = sizeof(sin); 4402 addrlen = 4; 4403 addrp = &sin.sin_addr.s_addr; 4404 } else { 4405 memset(&sin6, 0, sizeof(sin6)); 4406 sin6.sin6_family = AF_INET6; 4407 sin6.sin6_port = htons(data->port); 4408 4409 sa = (struct sockaddr *)&sin6; 4410 socklen = sizeof(sin6); 4411 addrlen = 16; 4412 addrp = &sin6.sin6_addr.s6_addr; 4413 } 4414 4415 res = NULL; 4416 for (i=0; i < count; ++i) { 4417 struct evutil_addrinfo *ai; 4418 memcpy(addrp, ((char*)addresses)+i*addrlen, addrlen); 4419 ai = evutil_new_addrinfo_(sa, socklen, &data->hints); 4420 if (!ai) { 4421 if (other_req->r) { 4422 evdns_cancel_request(NULL, other_req->r); 4423 } 4424 data->user_cb(EVUTIL_EAI_MEMORY, NULL, data->user_data); 4425 if (res) 4426 evutil_freeaddrinfo(res); 4427 4428 if (other_req->r == NULL) 4429 free_getaddrinfo_request(data); 4430 return; 4431 } 4432 res = evutil_addrinfo_append_(res, ai); 4433 } 4434 4435 if (other_req->r) { 4436 /* The other request is still in progress; wait for it */ 4437 /* XXXX handle failure from set_timeout */ 4438 evdns_getaddrinfo_set_timeout(data->evdns_base, data); 4439 data->pending_result = res; 4440 return; 4441 } else { 4442 /* The other request is done or never started; append its 4443 * results (if any) and return them. */ 4444 if (data->pending_result) { 4445 if (req->type == DNS_IPv4_A) 4446 res = evutil_addrinfo_append_(res, 4447 data->pending_result); 4448 else 4449 res = evutil_addrinfo_append_( 4450 data->pending_result, res); 4451 data->pending_result = NULL; 4452 } 4453 4454 /* Call the user callback. */ 4455 add_cname_to_reply(data, res); 4456 data->user_cb(0, res, data->user_data); 4457 4458 /* Free data. */ 4459 free_getaddrinfo_request(data); 4460 } 4461 } 4462 4463 static struct hosts_entry * 4464 find_hosts_entry(struct evdns_base *base, const char *hostname, 4465 struct hosts_entry *find_after) 4466 { 4467 struct hosts_entry *e; 4468 4469 if (find_after) 4470 e = TAILQ_NEXT(find_after, next); 4471 else 4472 e = TAILQ_FIRST(&base->hostsdb); 4473 4474 for (; e; e = TAILQ_NEXT(e, next)) { 4475 if (!evutil_ascii_strcasecmp(e->hostname, hostname)) 4476 return e; 4477 } 4478 return NULL; 4479 } 4480 4481 static int 4482 evdns_getaddrinfo_fromhosts(struct evdns_base *base, 4483 const char *nodename, struct evutil_addrinfo *hints, ev_uint16_t port, 4484 struct evutil_addrinfo **res) 4485 { 4486 int n_found = 0; 4487 struct hosts_entry *e; 4488 struct evutil_addrinfo *ai=NULL; 4489 int f = hints->ai_family; 4490 4491 EVDNS_LOCK(base); 4492 for (e = find_hosts_entry(base, nodename, NULL); e; 4493 e = find_hosts_entry(base, nodename, e)) { 4494 struct evutil_addrinfo *ai_new; 4495 ++n_found; 4496 if ((e->addr.sa.sa_family == AF_INET && f == PF_INET6) || 4497 (e->addr.sa.sa_family == AF_INET6 && f == PF_INET)) 4498 continue; 4499 ai_new = evutil_new_addrinfo_(&e->addr.sa, e->addrlen, hints); 4500 if (!ai_new) { 4501 n_found = 0; 4502 goto out; 4503 } 4504 sockaddr_setport(ai_new->ai_addr, port); 4505 ai = evutil_addrinfo_append_(ai, ai_new); 4506 } 4507 EVDNS_UNLOCK(base); 4508 out: 4509 if (n_found) { 4510 /* Note that we return an empty answer if we found entries for 4511 * this hostname but none were of the right address type. */ 4512 *res = ai; 4513 return 0; 4514 } else { 4515 if (ai) 4516 evutil_freeaddrinfo(ai); 4517 return -1; 4518 } 4519 } 4520 4521 struct evdns_getaddrinfo_request * 4522 evdns_getaddrinfo(struct evdns_base *dns_base, 4523 const char *nodename, const char *servname, 4524 const struct evutil_addrinfo *hints_in, 4525 evdns_getaddrinfo_cb cb, void *arg) 4526 { 4527 struct evdns_getaddrinfo_request *data; 4528 struct evutil_addrinfo hints; 4529 struct evutil_addrinfo *res = NULL; 4530 int err; 4531 int port = 0; 4532 int want_cname = 0; 4533 4534 if (!dns_base) { 4535 dns_base = current_base; 4536 if (!dns_base) { 4537 log(EVDNS_LOG_WARN, 4538 "Call to getaddrinfo_async with no " 4539 "evdns_base configured."); 4540 cb(EVUTIL_EAI_FAIL, NULL, arg); /* ??? better error? */ 4541 return NULL; 4542 } 4543 } 4544 4545 /* If we _must_ answer this immediately, do so. */ 4546 if ((hints_in && (hints_in->ai_flags & EVUTIL_AI_NUMERICHOST))) { 4547 res = NULL; 4548 err = evutil_getaddrinfo(nodename, servname, hints_in, &res); 4549 cb(err, res, arg); 4550 return NULL; 4551 } 4552 4553 if (hints_in) { 4554 memcpy(&hints, hints_in, sizeof(hints)); 4555 } else { 4556 memset(&hints, 0, sizeof(hints)); 4557 hints.ai_family = PF_UNSPEC; 4558 } 4559 4560 evutil_adjust_hints_for_addrconfig_(&hints); 4561 4562 /* Now try to see if we _can_ answer immediately. */ 4563 /* (It would be nice to do this by calling getaddrinfo directly, with 4564 * AI_NUMERICHOST, on plaforms that have it, but we can't: there isn't 4565 * a reliable way to distinguish the "that wasn't a numeric host!" case 4566 * from any other EAI_NONAME cases.) */ 4567 err = evutil_getaddrinfo_common_(nodename, servname, &hints, &res, &port); 4568 if (err != EVUTIL_EAI_NEED_RESOLVE) { 4569 cb(err, res, arg); 4570 return NULL; 4571 } 4572 4573 /* If there is an entry in the hosts file, we should give it now. */ 4574 if (!evdns_getaddrinfo_fromhosts(dns_base, nodename, &hints, port, &res)) { 4575 cb(0, res, arg); 4576 return NULL; 4577 } 4578 4579 /* Okay, things are serious now. We're going to need to actually 4580 * launch a request. 4581 */ 4582 data = mm_calloc(1,sizeof(struct evdns_getaddrinfo_request)); 4583 if (!data) { 4584 cb(EVUTIL_EAI_MEMORY, NULL, arg); 4585 return NULL; 4586 } 4587 4588 memcpy(&data->hints, &hints, sizeof(data->hints)); 4589 data->port = (ev_uint16_t)port; 4590 data->ipv4_request.type = DNS_IPv4_A; 4591 data->ipv6_request.type = DNS_IPv6_AAAA; 4592 data->user_cb = cb; 4593 data->user_data = arg; 4594 data->evdns_base = dns_base; 4595 4596 want_cname = (hints.ai_flags & EVUTIL_AI_CANONNAME); 4597 4598 /* If we are asked for a PF_UNSPEC address, we launch two requests in 4599 * parallel: one for an A address and one for an AAAA address. We 4600 * can't send just one request, since many servers only answer one 4601 * question per DNS request. 4602 * 4603 * Once we have the answer to one request, we allow for a short 4604 * timeout before we report it, to see if the other one arrives. If 4605 * they both show up in time, then we report both the answers. 4606 * 4607 * If too many addresses of one type time out or fail, we should stop 4608 * launching those requests. (XXX we don't do that yet.) 4609 */ 4610 4611 if (hints.ai_family != PF_INET6) { 4612 log(EVDNS_LOG_DEBUG, "Sending request for %s on ipv4 as %p", 4613 nodename, &data->ipv4_request); 4614 4615 data->ipv4_request.r = evdns_base_resolve_ipv4(dns_base, 4616 nodename, 0, evdns_getaddrinfo_gotresolve, 4617 &data->ipv4_request); 4618 if (want_cname) 4619 data->ipv4_request.r->current_req->put_cname_in_ptr = 4620 &data->cname_result; 4621 } 4622 if (hints.ai_family != PF_INET) { 4623 log(EVDNS_LOG_DEBUG, "Sending request for %s on ipv6 as %p", 4624 nodename, &data->ipv6_request); 4625 4626 data->ipv6_request.r = evdns_base_resolve_ipv6(dns_base, 4627 nodename, 0, evdns_getaddrinfo_gotresolve, 4628 &data->ipv6_request); 4629 if (want_cname) 4630 data->ipv6_request.r->current_req->put_cname_in_ptr = 4631 &data->cname_result; 4632 } 4633 4634 evtimer_assign(&data->timeout, dns_base->event_base, 4635 evdns_getaddrinfo_timeout_cb, data); 4636 4637 if (data->ipv4_request.r || data->ipv6_request.r) { 4638 return data; 4639 } else { 4640 mm_free(data); 4641 cb(EVUTIL_EAI_FAIL, NULL, arg); 4642 return NULL; 4643 } 4644 } 4645 4646 void 4647 evdns_getaddrinfo_cancel(struct evdns_getaddrinfo_request *data) 4648 { 4649 EVDNS_LOCK(data->evdns_base); 4650 if (data->request_done) { 4651 EVDNS_UNLOCK(data->evdns_base); 4652 return; 4653 } 4654 event_del(&data->timeout); 4655 data->user_canceled = 1; 4656 if (data->ipv4_request.r) 4657 evdns_cancel_request(data->evdns_base, data->ipv4_request.r); 4658 if (data->ipv6_request.r) 4659 evdns_cancel_request(data->evdns_base, data->ipv6_request.r); 4660 EVDNS_UNLOCK(data->evdns_base); 4661 } 4662