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