1/* $NetBSD: dns.h,v 1.6 2020/05/25 20:47:34 christos Exp $ */ 2 3/* 4 * Copyright (c) 2006-2007 Niels Provos <provos@citi.umich.edu> 5 * Copyright (c) 2007-2012 Niels Provos and Nick Mathewson 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 3. The name of the author may not be used to endorse or promote products 16 * derived from this software without specific prior written permission. 17 * 18 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 19 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 20 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 21 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 22 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 23 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 24 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 25 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 26 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 27 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 28 */ 29 30/* 31 * The original DNS code is due to Adam Langley with heavy 32 * modifications by Nick Mathewson. Adam put his DNS software in the 33 * public domain. You can find his original copyright below. Please, 34 * aware that the code as part of Libevent is governed by the 3-clause 35 * BSD license above. 36 * 37 * This software is Public Domain. To view a copy of the public domain dedication, 38 * visit http://creativecommons.org/licenses/publicdomain/ or send a letter to 39 * Creative Commons, 559 Nathan Abbott Way, Stanford, California 94305, USA. 40 * 41 * I ask and expect, but do not require, that all derivative works contain an 42 * attribution similar to: 43 * Parts developed by Adam Langley <agl@imperialviolet.org> 44 * 45 * You may wish to replace the word "Parts" with something else depending on 46 * the amount of original code. 47 * 48 * (Derivative works does not include programs which link against, run or include 49 * the source verbatim in their source distributions) 50 */ 51 52/** @file event2/dns.h 53 * 54 * Welcome, gentle reader 55 * 56 * Async DNS lookups are really a whole lot harder than they should be, 57 * mostly stemming from the fact that the libc resolver has never been 58 * very good at them. Before you use this library you should see if libc 59 * can do the job for you with the modern async call getaddrinfo_a 60 * (see http://www.imperialviolet.org/page25.html#e498). Otherwise, 61 * please continue. 62 * 63 * The library keeps track of the state of nameservers and will avoid 64 * them when they go down. Otherwise it will round robin between them. 65 * 66 * Quick start guide: 67 * #include "evdns.h" 68 * void callback(int result, char type, int count, int ttl, 69 * void *addresses, void *arg); 70 * evdns_resolv_conf_parse(DNS_OPTIONS_ALL, "/etc/resolv.conf"); 71 * evdns_resolve("www.hostname.com", 0, callback, NULL); 72 * 73 * When the lookup is complete the callback function is called. The 74 * first argument will be one of the DNS_ERR_* defines in evdns.h. 75 * Hopefully it will be DNS_ERR_NONE, in which case type will be 76 * DNS_IPv4_A, count will be the number of IP addresses, ttl is the time 77 * which the data can be cached for (in seconds), addresses will point 78 * to an array of uint32_t's and arg will be whatever you passed to 79 * evdns_resolve. 80 * 81 * Searching: 82 * 83 * In order for this library to be a good replacement for glibc's resolver it 84 * supports searching. This involves setting a list of default domains, in 85 * which names will be queried for. The number of dots in the query name 86 * determines the order in which this list is used. 87 * 88 * Searching appears to be a single lookup from the point of view of the API, 89 * although many DNS queries may be generated from a single call to 90 * evdns_resolve. Searching can also drastically slow down the resolution 91 * of names. 92 * 93 * To disable searching: 94 * 1. Never set it up. If you never call evdns_resolv_conf_parse or 95 * evdns_search_add then no searching will occur. 96 * 97 * 2. If you do call evdns_resolv_conf_parse then don't pass 98 * DNS_OPTION_SEARCH (or DNS_OPTIONS_ALL, which implies it). 99 * 100 * 3. When calling evdns_resolve, pass the DNS_QUERY_NO_SEARCH flag. 101 * 102 * The order of searches depends on the number of dots in the name. If the 103 * number is greater than the ndots setting then the names is first tried 104 * globally. Otherwise each search domain is appended in turn. 105 * 106 * The ndots setting can either be set from a resolv.conf, or by calling 107 * evdns_search_ndots_set. 108 * 109 * For example, with ndots set to 1 (the default) and a search domain list of 110 * ["myhome.net"]: 111 * Query: www 112 * Order: www.myhome.net, www. 113 * 114 * Query: www.abc 115 * Order: www.abc., www.abc.myhome.net 116 * 117 * Internals: 118 * 119 * Requests are kept in two queues. The first is the inflight queue. In 120 * this queue requests have an allocated transaction id and nameserver. 121 * They will soon be transmitted if they haven't already been. 122 * 123 * The second is the waiting queue. The size of the inflight ring is 124 * limited and all other requests wait in waiting queue for space. This 125 * bounds the number of concurrent requests so that we don't flood the 126 * nameserver. Several algorithms require a full walk of the inflight 127 * queue and so bounding its size keeps thing going nicely under huge 128 * (many thousands of requests) loads. 129 * 130 * If a nameserver loses too many requests it is considered down and we 131 * try not to use it. After a while we send a probe to that nameserver 132 * (a lookup for google.com) and, if it replies, we consider it working 133 * again. If the nameserver fails a probe we wait longer to try again 134 * with the next probe. 135 */ 136 137#ifndef EVENT2_DNS_H_INCLUDED_ 138#define EVENT2_DNS_H_INCLUDED_ 139 140#include <event2/visibility.h> 141 142#ifdef __cplusplus 143extern "C" { 144#endif 145 146/* For integer types. */ 147#include <event2/util.h> 148 149/** Error codes 0-5 are as described in RFC 1035. */ 150#define DNS_ERR_NONE 0 151/** The name server was unable to interpret the query */ 152#define DNS_ERR_FORMAT 1 153/** The name server was unable to process this query due to a problem with the 154 * name server */ 155#define DNS_ERR_SERVERFAILED 2 156/** The domain name does not exist */ 157#define DNS_ERR_NOTEXIST 3 158/** The name server does not support the requested kind of query */ 159#define DNS_ERR_NOTIMPL 4 160/** The name server refuses to reform the specified operation for policy 161 * reasons */ 162#define DNS_ERR_REFUSED 5 163/** The reply was truncated or ill-formatted */ 164#define DNS_ERR_TRUNCATED 65 165/** An unknown error occurred */ 166#define DNS_ERR_UNKNOWN 66 167/** Communication with the server timed out */ 168#define DNS_ERR_TIMEOUT 67 169/** The request was canceled because the DNS subsystem was shut down. */ 170#define DNS_ERR_SHUTDOWN 68 171/** The request was canceled via a call to evdns_cancel_request */ 172#define DNS_ERR_CANCEL 69 173/** There were no answers and no error condition in the DNS packet. 174 * This can happen when you ask for an address that exists, but a record 175 * type that doesn't. */ 176#define DNS_ERR_NODATA 70 177 178#define DNS_IPv4_A 1 179#define DNS_PTR 2 180#define DNS_IPv6_AAAA 3 181 182#define DNS_QUERY_NO_SEARCH 1 183 184#define DNS_OPTION_SEARCH 1 185#define DNS_OPTION_NAMESERVERS 2 186#define DNS_OPTION_MISC 4 187#define DNS_OPTION_HOSTSFILE 8 188#define DNS_OPTIONS_ALL 15 189 190/* Obsolete name for DNS_QUERY_NO_SEARCH */ 191#define DNS_NO_SEARCH DNS_QUERY_NO_SEARCH 192 193/** 194 * The callback that contains the results from a lookup. 195 * - result is one of the DNS_ERR_* values (DNS_ERR_NONE for success) 196 * - type is either DNS_IPv4_A or DNS_PTR or DNS_IPv6_AAAA 197 * - count contains the number of addresses of form type 198 * - ttl is the number of seconds the resolution may be cached for. 199 * - addresses needs to be cast according to type. It will be an array of 200 * 4-byte sequences for ipv4, or an array of 16-byte sequences for ipv6, 201 * or a nul-terminated string for PTR. 202 */ 203typedef void (*evdns_callback_type) (int result, char type, int count, int ttl, void *addresses, void *arg); 204 205struct evdns_base; 206struct event_base; 207 208/** Flag for evdns_base_new: process resolv.conf. */ 209#define EVDNS_BASE_INITIALIZE_NAMESERVERS 1 210/** Flag for evdns_base_new: Do not prevent the libevent event loop from 211 * exiting when we have no active dns requests. */ 212#define EVDNS_BASE_DISABLE_WHEN_INACTIVE 0x8000 213 214/** 215 Initialize the asynchronous DNS library. 216 217 This function initializes support for non-blocking name resolution by 218 calling evdns_resolv_conf_parse() on UNIX and 219 evdns_config_windows_nameservers() on Windows. 220 221 @param event_base the event base to associate the dns client with 222 @param flags any of EVDNS_BASE_INITIALIZE_NAMESERVERS| 223 EVDNS_BASE_DISABLE_WHEN_INACTIVE 224 @return evdns_base object if successful, or NULL if an error occurred. 225 @see evdns_base_free() 226 */ 227EVENT2_EXPORT_SYMBOL 228struct evdns_base * evdns_base_new(struct event_base *event_base, int initialize_nameservers); 229 230 231/** 232 Shut down the asynchronous DNS resolver and terminate all active requests. 233 234 If the 'fail_requests' option is enabled, all active requests will return 235 an empty result with the error flag set to DNS_ERR_SHUTDOWN. Otherwise, 236 the requests will be silently discarded. 237 238 @param evdns_base the evdns base to free 239 @param fail_requests if zero, active requests will be aborted; if non-zero, 240 active requests will return DNS_ERR_SHUTDOWN. 241 @see evdns_base_new() 242 */ 243EVENT2_EXPORT_SYMBOL 244void evdns_base_free(struct evdns_base *base, int fail_requests); 245 246/** 247 Remove all hosts entries that have been loaded into the event_base via 248 evdns_base_load_hosts or via event_base_resolv_conf_parse. 249 250 @param evdns_base the evdns base to remove outdated host addresses from 251 */ 252EVENT2_EXPORT_SYMBOL 253void evdns_base_clear_host_addresses(struct evdns_base *base); 254 255/** 256 Convert a DNS error code to a string. 257 258 @param err the DNS error code 259 @return a string containing an explanation of the error code 260*/ 261EVENT2_EXPORT_SYMBOL 262const char *evdns_err_to_string(int err); 263 264 265/** 266 Add a nameserver. 267 268 The address should be an IPv4 address in network byte order. 269 The type of address is chosen so that it matches in_addr.s_addr. 270 271 @param base the evdns_base to which to add the name server 272 @param address an IP address in network byte order 273 @return 0 if successful, or -1 if an error occurred 274 @see evdns_base_nameserver_ip_add() 275 */ 276EVENT2_EXPORT_SYMBOL 277int evdns_base_nameserver_add(struct evdns_base *base, 278 unsigned long int address); 279 280/** 281 Get the number of configured nameservers. 282 283 This returns the number of configured nameservers (not necessarily the 284 number of running nameservers). This is useful for double-checking 285 whether our calls to the various nameserver configuration functions 286 have been successful. 287 288 @param base the evdns_base to which to apply this operation 289 @return the number of configured nameservers 290 @see evdns_base_nameserver_add() 291 */ 292EVENT2_EXPORT_SYMBOL 293int evdns_base_count_nameservers(struct evdns_base *base); 294 295/** 296 Remove all configured nameservers, and suspend all pending resolves. 297 298 Resolves will not necessarily be re-attempted until evdns_base_resume() is called. 299 300 @param base the evdns_base to which to apply this operation 301 @return 0 if successful, or -1 if an error occurred 302 @see evdns_base_resume() 303 */ 304EVENT2_EXPORT_SYMBOL 305int evdns_base_clear_nameservers_and_suspend(struct evdns_base *base); 306 307 308/** 309 Resume normal operation and continue any suspended resolve requests. 310 311 Re-attempt resolves left in limbo after an earlier call to 312 evdns_base_clear_nameservers_and_suspend(). 313 314 @param base the evdns_base to which to apply this operation 315 @return 0 if successful, or -1 if an error occurred 316 @see evdns_base_clear_nameservers_and_suspend() 317 */ 318EVENT2_EXPORT_SYMBOL 319int evdns_base_resume(struct evdns_base *base); 320 321/** 322 Add a nameserver by string address. 323 324 This function parses a n IPv4 or IPv6 address from a string and adds it as a 325 nameserver. It supports the following formats: 326 - [IPv6Address]:port 327 - [IPv6Address] 328 - IPv6Address 329 - IPv4Address:port 330 - IPv4Address 331 332 If no port is specified, it defaults to 53. 333 334 @param base the evdns_base to which to apply this operation 335 @return 0 if successful, or -1 if an error occurred 336 @see evdns_base_nameserver_add() 337 */ 338EVENT2_EXPORT_SYMBOL 339int evdns_base_nameserver_ip_add(struct evdns_base *base, 340 const char *ip_as_string); 341 342/** 343 Add a nameserver by sockaddr. 344 **/ 345EVENT2_EXPORT_SYMBOL 346int 347evdns_base_nameserver_sockaddr_add(struct evdns_base *base, 348 const struct sockaddr *sa, ev_socklen_t len, unsigned flags); 349 350struct evdns_request; 351 352/** 353 Lookup an A record for a given name. 354 355 @param base the evdns_base to which to apply this operation 356 @param name a DNS hostname 357 @param flags either 0, or DNS_QUERY_NO_SEARCH to disable searching for this query. 358 @param callback a callback function to invoke when the request is completed 359 @param ptr an argument to pass to the callback function 360 @return an evdns_request object if successful, or NULL if an error occurred. 361 @see evdns_resolve_ipv6(), evdns_resolve_reverse(), evdns_resolve_reverse_ipv6(), evdns_cancel_request() 362 */ 363EVENT2_EXPORT_SYMBOL 364struct evdns_request *evdns_base_resolve_ipv4(struct evdns_base *base, const char *name, int flags, evdns_callback_type callback, void *ptr); 365 366/** 367 Lookup an AAAA record for a given name. 368 369 @param base the evdns_base to which to apply this operation 370 @param name a DNS hostname 371 @param flags either 0, or DNS_QUERY_NO_SEARCH to disable searching for this query. 372 @param callback a callback function to invoke when the request is completed 373 @param ptr an argument to pass to the callback function 374 @return an evdns_request object if successful, or NULL if an error occurred. 375 @see evdns_resolve_ipv4(), evdns_resolve_reverse(), evdns_resolve_reverse_ipv6(), evdns_cancel_request() 376 */ 377EVENT2_EXPORT_SYMBOL 378struct evdns_request *evdns_base_resolve_ipv6(struct evdns_base *base, const char *name, int flags, evdns_callback_type callback, void *ptr); 379 380struct in_addr; 381struct in6_addr; 382 383/** 384 Lookup a PTR record for a given IP address. 385 386 @param base the evdns_base to which to apply this operation 387 @param in an IPv4 address 388 @param flags either 0, or DNS_QUERY_NO_SEARCH to disable searching for this query. 389 @param callback a callback function to invoke when the request is completed 390 @param ptr an argument to pass to the callback function 391 @return an evdns_request object if successful, or NULL if an error occurred. 392 @see evdns_resolve_reverse_ipv6(), evdns_cancel_request() 393 */ 394EVENT2_EXPORT_SYMBOL 395struct evdns_request *evdns_base_resolve_reverse(struct evdns_base *base, const struct in_addr *in, int flags, evdns_callback_type callback, void *ptr); 396 397 398/** 399 Lookup a PTR record for a given IPv6 address. 400 401 @param base the evdns_base to which to apply this operation 402 @param in an IPv6 address 403 @param flags either 0, or DNS_QUERY_NO_SEARCH to disable searching for this query. 404 @param callback a callback function to invoke when the request is completed 405 @param ptr an argument to pass to the callback function 406 @return an evdns_request object if successful, or NULL if an error occurred. 407 @see evdns_resolve_reverse_ipv6(), evdns_cancel_request() 408 */ 409EVENT2_EXPORT_SYMBOL 410struct evdns_request *evdns_base_resolve_reverse_ipv6(struct evdns_base *base, const struct in6_addr *in, int flags, evdns_callback_type callback, void *ptr); 411 412/** 413 Cancels a pending DNS resolution request. 414 415 @param base the evdns_base that was used to make the request 416 @param req the evdns_request that was returned by calling a resolve function 417 @see evdns_base_resolve_ipv4(), evdns_base_resolve_ipv6, evdns_base_resolve_reverse 418*/ 419EVENT2_EXPORT_SYMBOL 420void evdns_cancel_request(struct evdns_base *base, struct evdns_request *req); 421 422/** 423 Set the value of a configuration option. 424 425 The currently available configuration options are: 426 427 ndots, timeout, max-timeouts, max-inflight, attempts, randomize-case, 428 bind-to, initial-probe-timeout, getaddrinfo-allow-skew. 429 430 In versions before Libevent 2.0.3-alpha, the option name needed to end with 431 a colon. 432 433 @param base the evdns_base to which to apply this operation 434 @param option the name of the configuration option to be modified 435 @param val the value to be set 436 @return 0 if successful, or -1 if an error occurred 437 */ 438EVENT2_EXPORT_SYMBOL 439int evdns_base_set_option(struct evdns_base *base, const char *option, const char *val); 440 441 442/** 443 Parse a resolv.conf file. 444 445 The 'flags' parameter determines what information is parsed from the 446 resolv.conf file. See the man page for resolv.conf for the format of this 447 file. 448 449 The following directives are not parsed from the file: sortlist, rotate, 450 no-check-names, inet6, debug. 451 452 If this function encounters an error, the possible return values are: 1 = 453 failed to open file, 2 = failed to stat file, 3 = file too large, 4 = out of 454 memory, 5 = short read from file, 6 = no nameservers listed in the file 455 456 @param base the evdns_base to which to apply this operation 457 @param flags any of DNS_OPTION_NAMESERVERS|DNS_OPTION_SEARCH|DNS_OPTION_MISC| 458 DNS_OPTION_HOSTSFILE|DNS_OPTIONS_ALL 459 @param filename the path to the resolv.conf file 460 @return 0 if successful, or various positive error codes if an error 461 occurred (see above) 462 @see resolv.conf(3), evdns_config_windows_nameservers() 463 */ 464EVENT2_EXPORT_SYMBOL 465int evdns_base_resolv_conf_parse(struct evdns_base *base, int flags, const char *const filename); 466 467/** 468 Load an /etc/hosts-style file from 'hosts_fname' into 'base'. 469 470 If hosts_fname is NULL, add minimal entries for localhost, and nothing 471 else. 472 473 Note that only evdns_getaddrinfo uses the /etc/hosts entries. 474 475 This function does not replace previously loaded hosts entries; to do that, 476 call evdns_base_clear_host_addresses first. 477 478 Return 0 on success, negative on failure. 479*/ 480EVENT2_EXPORT_SYMBOL 481int evdns_base_load_hosts(struct evdns_base *base, const char *hosts_fname); 482 483/** 484 Obtain nameserver information using the Windows API. 485 486 Attempt to configure a set of nameservers based on platform settings on 487 a win32 host. Preferentially tries to use GetNetworkParams; if that fails, 488 looks in the registry. 489 490 @return 0 if successful, or -1 if an error occurred 491 @see evdns_resolv_conf_parse() 492 */ 493#ifdef _WIN32 494EVENT2_EXPORT_SYMBOL 495int evdns_base_config_windows_nameservers(struct evdns_base *); 496#define EVDNS_BASE_CONFIG_WINDOWS_NAMESERVERS_IMPLEMENTED 497#endif 498 499 500/** 501 Clear the list of search domains. 502 */ 503EVENT2_EXPORT_SYMBOL 504void evdns_base_search_clear(struct evdns_base *base); 505 506 507/** 508 Add a domain to the list of search domains 509 510 @param domain the domain to be added to the search list 511 */ 512EVENT2_EXPORT_SYMBOL 513void evdns_base_search_add(struct evdns_base *base, const char *domain); 514 515 516/** 517 Set the 'ndots' parameter for searches. 518 519 Sets the number of dots which, when found in a name, causes 520 the first query to be without any search domain. 521 522 @param ndots the new ndots parameter 523 */ 524EVENT2_EXPORT_SYMBOL 525void evdns_base_search_ndots_set(struct evdns_base *base, const int ndots); 526 527/** 528 A callback that is invoked when a log message is generated 529 530 @param is_warning indicates if the log message is a 'warning' 531 @param msg the content of the log message 532 */ 533typedef void (*evdns_debug_log_fn_type)(int is_warning, const char *msg); 534 535 536/** 537 Set the callback function to handle DNS log messages. If this 538 callback is not set, evdns log messages are handled with the regular 539 Libevent logging system. 540 541 @param fn the callback to be invoked when a log message is generated 542 */ 543EVENT2_EXPORT_SYMBOL 544void evdns_set_log_fn(evdns_debug_log_fn_type fn); 545 546/** 547 Set a callback that will be invoked to generate transaction IDs. By 548 default, we pick transaction IDs based on the current clock time, which 549 is bad for security. 550 551 @param fn the new callback, or NULL to use the default. 552 553 NOTE: This function has no effect in Libevent 2.0.4-alpha and later, 554 since Libevent now provides its own secure RNG. 555 */ 556EVENT2_EXPORT_SYMBOL 557void evdns_set_transaction_id_fn(ev_uint16_t (*fn)(void)); 558 559/** 560 Set a callback used to generate random bytes. By default, we use 561 the same function as passed to evdns_set_transaction_id_fn to generate 562 bytes two at a time. If a function is provided here, it's also used 563 to generate transaction IDs. 564 565 NOTE: This function has no effect in Libevent 2.0.4-alpha and later, 566 since Libevent now provides its own secure RNG. 567*/ 568EVENT2_EXPORT_SYMBOL 569void evdns_set_random_bytes_fn(void (*fn)(char *, size_t)); 570 571/* 572 * Functions used to implement a DNS server. 573 */ 574 575struct evdns_server_request; 576struct evdns_server_question; 577 578/** 579 A callback to implement a DNS server. The callback function receives a DNS 580 request. It should then optionally add a number of answers to the reply 581 using the evdns_server_request_add_*_reply functions, before calling either 582 evdns_server_request_respond to send the reply back, or 583 evdns_server_request_drop to decline to answer the request. 584 585 @param req A newly received request 586 @param user_data A pointer that was passed to 587 evdns_add_server_port_with_base(). 588 */ 589typedef void (*evdns_request_callback_fn_type)(struct evdns_server_request *, void *); 590#define EVDNS_ANSWER_SECTION 0 591#define EVDNS_AUTHORITY_SECTION 1 592#define EVDNS_ADDITIONAL_SECTION 2 593 594#define EVDNS_TYPE_A 1 595#define EVDNS_TYPE_NS 2 596#define EVDNS_TYPE_CNAME 5 597#define EVDNS_TYPE_SOA 6 598#define EVDNS_TYPE_PTR 12 599#define EVDNS_TYPE_MX 15 600#define EVDNS_TYPE_TXT 16 601#define EVDNS_TYPE_AAAA 28 602 603#define EVDNS_QTYPE_AXFR 252 604#define EVDNS_QTYPE_ALL 255 605 606#define EVDNS_CLASS_INET 1 607 608/* flags that can be set in answers; as part of the err parameter */ 609#define EVDNS_FLAGS_AA 0x400 610#define EVDNS_FLAGS_RD 0x080 611 612/** Create a new DNS server port. 613 614 @param base The event base to handle events for the server port. 615 @param socket A UDP socket to accept DNS requests. 616 @param flags Always 0 for now. 617 @param callback A function to invoke whenever we get a DNS request 618 on the socket. 619 @param user_data Data to pass to the callback. 620 @return an evdns_server_port structure for this server port. 621 */ 622EVENT2_EXPORT_SYMBOL 623struct evdns_server_port *evdns_add_server_port_with_base(struct event_base *base, evutil_socket_t socket, int flags, evdns_request_callback_fn_type callback, void *user_data); 624/** Close down a DNS server port, and free associated structures. */ 625EVENT2_EXPORT_SYMBOL 626void evdns_close_server_port(struct evdns_server_port *port); 627 628/** Sets some flags in a reply we're building. 629 Allows setting of the AA or RD flags 630 */ 631EVENT2_EXPORT_SYMBOL 632void evdns_server_request_set_flags(struct evdns_server_request *req, int flags); 633 634/* Functions to add an answer to an in-progress DNS reply. 635 */ 636EVENT2_EXPORT_SYMBOL 637int evdns_server_request_add_reply(struct evdns_server_request *req, int section, const char *name, int type, int dns_class, int ttl, int datalen, int is_name, const char *data); 638EVENT2_EXPORT_SYMBOL 639int evdns_server_request_add_a_reply(struct evdns_server_request *req, const char *name, int n, const void *addrs, int ttl); 640EVENT2_EXPORT_SYMBOL 641int evdns_server_request_add_aaaa_reply(struct evdns_server_request *req, const char *name, int n, const void *addrs, int ttl); 642EVENT2_EXPORT_SYMBOL 643int evdns_server_request_add_ptr_reply(struct evdns_server_request *req, struct in_addr *in, const char *inaddr_name, const char *hostname, int ttl); 644EVENT2_EXPORT_SYMBOL 645int evdns_server_request_add_cname_reply(struct evdns_server_request *req, const char *name, const char *cname, int ttl); 646 647/** 648 Send back a response to a DNS request, and free the request structure. 649*/ 650EVENT2_EXPORT_SYMBOL 651int evdns_server_request_respond(struct evdns_server_request *req, int err); 652/** 653 Free a DNS request without sending back a reply. 654*/ 655EVENT2_EXPORT_SYMBOL 656int evdns_server_request_drop(struct evdns_server_request *req); 657struct sockaddr; 658/** 659 Get the address that made a DNS request. 660 */ 661EVENT2_EXPORT_SYMBOL 662int evdns_server_request_get_requesting_addr(struct evdns_server_request *req, struct sockaddr *sa, int addr_len); 663 664/** Callback for evdns_getaddrinfo. */ 665typedef void (*evdns_getaddrinfo_cb)(int result, struct evutil_addrinfo *res, void *arg); 666 667struct evdns_base; 668struct evdns_getaddrinfo_request; 669/** Make a non-blocking getaddrinfo request using the dns_base in 'dns_base'. 670 * 671 * If we can answer the request immediately (with an error or not!), then we 672 * invoke cb immediately and return NULL. Otherwise we return 673 * an evdns_getaddrinfo_request and invoke cb later. 674 * 675 * When the callback is invoked, we pass as its first argument the error code 676 * that getaddrinfo would return (or 0 for no error). As its second argument, 677 * we pass the evutil_addrinfo structures we found (or NULL on error). We 678 * pass 'arg' as the third argument. 679 * 680 * Limitations: 681 * 682 * - The AI_V4MAPPED and AI_ALL flags are not currently implemented. 683 * - For ai_socktype, we only handle SOCKTYPE_STREAM, SOCKTYPE_UDP, and 0. 684 * - For ai_protocol, we only handle IPPROTO_TCP, IPPROTO_UDP, and 0. 685 */ 686EVENT2_EXPORT_SYMBOL 687struct evdns_getaddrinfo_request *evdns_getaddrinfo( 688 struct evdns_base *dns_base, 689 const char *nodename, const char *servname, 690 const struct evutil_addrinfo *hints_in, 691 evdns_getaddrinfo_cb cb, void *arg); 692 693/* Cancel an in-progress evdns_getaddrinfo. This MUST NOT be called after the 694 * getaddrinfo's callback has been invoked. The resolves will be canceled, 695 * and the callback will be invoked with the error EVUTIL_EAI_CANCEL. */ 696EVENT2_EXPORT_SYMBOL 697void evdns_getaddrinfo_cancel(struct evdns_getaddrinfo_request *req); 698 699/** 700 Retrieve the address of the 'idx'th configured nameserver. 701 702 @param base The evdns_base to examine. 703 @param idx The index of the nameserver to get the address of. 704 @param sa A location to receive the server's address. 705 @param len The number of bytes available at sa. 706 707 @return the number of bytes written into sa on success. On failure, returns 708 -1 if idx is greater than the number of configured nameservers, or a 709 value greater than 'len' if len was not high enough. 710 */ 711EVENT2_EXPORT_SYMBOL 712int evdns_base_get_nameserver_addr(struct evdns_base *base, int idx, 713 struct sockaddr *sa, ev_socklen_t len); 714 715#ifdef __cplusplus 716} 717#endif 718 719#endif /* !EVENT2_DNS_H_INCLUDED_ */ 720