dns.h revision 1.1.1.3
1/* $NetBSD: dns.h,v 1.1.1.3 2017/01/31 21:14:53 christos Exp $ */ 2/* 3 * Copyright (c) 2006-2007 Niels Provos <provos@citi.umich.edu> 4 * Copyright (c) 2007-2012 Niels Provos and Nick Mathewson 5 * 6 * Redistribution and use in source and binary forms, with or without 7 * modification, are permitted provided that the following conditions 8 * are met: 9 * 1. Redistributions of source code must retain the above copyright 10 * notice, this list of conditions and the following disclaimer. 11 * 2. Redistributions in binary form must reproduce the above copyright 12 * notice, this list of conditions and the following disclaimer in the 13 * documentation and/or other materials provided with the distribution. 14 * 3. The name of the author may not be used to endorse or promote products 15 * derived from this software without specific prior written permission. 16 * 17 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 18 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 19 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 20 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 21 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 22 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 23 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 24 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 26 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 27 */ 28 29/* 30 * The original DNS code is due to Adam Langley with heavy 31 * modifications by Nick Mathewson. Adam put his DNS software in the 32 * public domain. You can find his original copyright below. Please, 33 * aware that the code as part of Libevent is governed by the 3-clause 34 * BSD license above. 35 * 36 * This software is Public Domain. To view a copy of the public domain dedication, 37 * visit http://creativecommons.org/licenses/publicdomain/ or send a letter to 38 * Creative Commons, 559 Nathan Abbott Way, Stanford, California 94305, USA. 39 * 40 * I ask and expect, but do not require, that all derivative works contain an 41 * attribution similar to: 42 * Parts developed by Adam Langley <agl@imperialviolet.org> 43 * 44 * You may wish to replace the word "Parts" with something else depending on 45 * the amount of original code. 46 * 47 * (Derivative works does not include programs which link against, run or include 48 * the source verbatim in their source distributions) 49 */ 50 51/** @file event2/dns.h 52 * 53 * Welcome, gentle reader 54 * 55 * Async DNS lookups are really a whole lot harder than they should be, 56 * mostly stemming from the fact that the libc resolver has never been 57 * very good at them. Before you use this library you should see if libc 58 * can do the job for you with the modern async call getaddrinfo_a 59 * (see http://www.imperialviolet.org/page25.html#e498). Otherwise, 60 * please continue. 61 * 62 * The library keeps track of the state of nameservers and will avoid 63 * them when they go down. Otherwise it will round robin between them. 64 * 65 * Quick start guide: 66 * #include "evdns.h" 67 * void callback(int result, char type, int count, int ttl, 68 * void *addresses, void *arg); 69 * evdns_resolv_conf_parse(DNS_OPTIONS_ALL, "/etc/resolv.conf"); 70 * evdns_resolve("www.hostname.com", 0, callback, NULL); 71 * 72 * When the lookup is complete the callback function is called. The 73 * first argument will be one of the DNS_ERR_* defines in evdns.h. 74 * Hopefully it will be DNS_ERR_NONE, in which case type will be 75 * DNS_IPv4_A, count will be the number of IP addresses, ttl is the time 76 * which the data can be cached for (in seconds), addresses will point 77 * to an array of uint32_t's and arg will be whatever you passed to 78 * evdns_resolve. 79 * 80 * Searching: 81 * 82 * In order for this library to be a good replacement for glibc's resolver it 83 * supports searching. This involves setting a list of default domains, in 84 * which names will be queried for. The number of dots in the query name 85 * determines the order in which this list is used. 86 * 87 * Searching appears to be a single lookup from the point of view of the API, 88 * although many DNS queries may be generated from a single call to 89 * evdns_resolve. Searching can also drastically slow down the resolution 90 * of names. 91 * 92 * To disable searching: 93 * 1. Never set it up. If you never call evdns_resolv_conf_parse or 94 * evdns_search_add then no searching will occur. 95 * 96 * 2. If you do call evdns_resolv_conf_parse then don't pass 97 * DNS_OPTION_SEARCH (or DNS_OPTIONS_ALL, which implies it). 98 * 99 * 3. When calling evdns_resolve, pass the DNS_QUERY_NO_SEARCH flag. 100 * 101 * The order of searches depends on the number of dots in the name. If the 102 * number is greater than the ndots setting then the names is first tried 103 * globally. Otherwise each search domain is appended in turn. 104 * 105 * The ndots setting can either be set from a resolv.conf, or by calling 106 * evdns_search_ndots_set. 107 * 108 * For example, with ndots set to 1 (the default) and a search domain list of 109 * ["myhome.net"]: 110 * Query: www 111 * Order: www.myhome.net, www. 112 * 113 * Query: www.abc 114 * Order: www.abc., www.abc.myhome.net 115 * 116 * Internals: 117 * 118 * Requests are kept in two queues. The first is the inflight queue. In 119 * this queue requests have an allocated transaction id and nameserver. 120 * They will soon be transmitted if they haven't already been. 121 * 122 * The second is the waiting queue. The size of the inflight ring is 123 * limited and all other requests wait in waiting queue for space. This 124 * bounds the number of concurrent requests so that we don't flood the 125 * nameserver. Several algorithms require a full walk of the inflight 126 * queue and so bounding its size keeps thing going nicely under huge 127 * (many thousands of requests) loads. 128 * 129 * If a nameserver loses too many requests it is considered down and we 130 * try not to use it. After a while we send a probe to that nameserver 131 * (a lookup for google.com) and, if it replies, we consider it working 132 * again. If the nameserver fails a probe we wait longer to try again 133 * with the next probe. 134 */ 135 136#ifndef EVENT2_DNS_H_INCLUDED_ 137#define EVENT2_DNS_H_INCLUDED_ 138 139#include <event2/visibility.h> 140 141#ifdef __cplusplus 142extern "C" { 143#endif 144 145/* For integer types. */ 146#include <event2/util.h> 147 148/** Error codes 0-5 are as described in RFC 1035. */ 149#define DNS_ERR_NONE 0 150/** The name server was unable to interpret the query */ 151#define DNS_ERR_FORMAT 1 152/** The name server was unable to process this query due to a problem with the 153 * name server */ 154#define DNS_ERR_SERVERFAILED 2 155/** The domain name does not exist */ 156#define DNS_ERR_NOTEXIST 3 157/** The name server does not support the requested kind of query */ 158#define DNS_ERR_NOTIMPL 4 159/** The name server refuses to reform the specified operation for policy 160 * reasons */ 161#define DNS_ERR_REFUSED 5 162/** The reply was truncated or ill-formatted */ 163#define DNS_ERR_TRUNCATED 65 164/** An unknown error occurred */ 165#define DNS_ERR_UNKNOWN 66 166/** Communication with the server timed out */ 167#define DNS_ERR_TIMEOUT 67 168/** The request was canceled because the DNS subsystem was shut down. */ 169#define DNS_ERR_SHUTDOWN 68 170/** The request was canceled via a call to evdns_cancel_request */ 171#define DNS_ERR_CANCEL 69 172/** There were no answers and no error condition in the DNS packet. 173 * This can happen when you ask for an address that exists, but a record 174 * type that doesn't. */ 175#define DNS_ERR_NODATA 70 176 177#define DNS_IPv4_A 1 178#define DNS_PTR 2 179#define DNS_IPv6_AAAA 3 180 181#define DNS_QUERY_NO_SEARCH 1 182 183#define DNS_OPTION_SEARCH 1 184#define DNS_OPTION_NAMESERVERS 2 185#define DNS_OPTION_MISC 4 186#define DNS_OPTION_HOSTSFILE 8 187#define DNS_OPTIONS_ALL 15 188 189/* Obsolete name for DNS_QUERY_NO_SEARCH */ 190#define DNS_NO_SEARCH DNS_QUERY_NO_SEARCH 191 192/** 193 * The callback that contains the results from a lookup. 194 * - result is one of the DNS_ERR_* values (DNS_ERR_NONE for success) 195 * - type is either DNS_IPv4_A or DNS_PTR or DNS_IPv6_AAAA 196 * - count contains the number of addresses of form type 197 * - ttl is the number of seconds the resolution may be cached for. 198 * - addresses needs to be cast according to type. It will be an array of 199 * 4-byte sequences for ipv4, or an array of 16-byte sequences for ipv6, 200 * or a nul-terminated string for PTR. 201 */ 202typedef void (*evdns_callback_type) (int result, char type, int count, int ttl, void *addresses, void *arg); 203 204struct evdns_base; 205struct event_base; 206 207/** Flag for evdns_base_new: process resolv.conf. */ 208#define EVDNS_BASE_INITIALIZE_NAMESERVERS 1 209/** Flag for evdns_base_new: Do not prevent the libevent event loop from 210 * exiting when we have no active dns requests. */ 211#define EVDNS_BASE_DISABLE_WHEN_INACTIVE 0x8000 212 213/** 214 Initialize the asynchronous DNS library. 215 216 This function initializes support for non-blocking name resolution by 217 calling evdns_resolv_conf_parse() on UNIX and 218 evdns_config_windows_nameservers() on Windows. 219 220 @param event_base the event base to associate the dns client with 221 @param flags any of EVDNS_BASE_INITIALIZE_NAMESERVERS| 222 EVDNS_BASE_DISABLE_WHEN_INACTIVE 223 @return evdns_base object if successful, or NULL if an error occurred. 224 @see evdns_base_free() 225 */ 226EVENT2_EXPORT_SYMBOL 227struct evdns_base * evdns_base_new(struct event_base *event_base, int initialize_nameservers); 228 229 230/** 231 Shut down the asynchronous DNS resolver and terminate all active requests. 232 233 If the 'fail_requests' option is enabled, all active requests will return 234 an empty result with the error flag set to DNS_ERR_SHUTDOWN. Otherwise, 235 the requests will be silently discarded. 236 237 @param evdns_base the evdns base to free 238 @param fail_requests if zero, active requests will be aborted; if non-zero, 239 active requests will return DNS_ERR_SHUTDOWN. 240 @see evdns_base_new() 241 */ 242EVENT2_EXPORT_SYMBOL 243void evdns_base_free(struct evdns_base *base, int fail_requests); 244 245/** 246 Remove all hosts entries that have been loaded into the event_base via 247 evdns_base_load_hosts or via event_base_resolv_conf_parse. 248 249 @param evdns_base the evdns base to remove outdated host addresses from 250 */ 251EVENT2_EXPORT_SYMBOL 252void evdns_base_clear_host_addresses(struct evdns_base *base); 253 254/** 255 Convert a DNS error code to a string. 256 257 @param err the DNS error code 258 @return a string containing an explanation of the error code 259*/ 260EVENT2_EXPORT_SYMBOL 261const char *evdns_err_to_string(int err); 262 263 264/** 265 Add a nameserver. 266 267 The address should be an IPv4 address in network byte order. 268 The type of address is chosen so that it matches in_addr.s_addr. 269 270 @param base the evdns_base to which to add the name server 271 @param address an IP address in network byte order 272 @return 0 if successful, or -1 if an error occurred 273 @see evdns_base_nameserver_ip_add() 274 */ 275EVENT2_EXPORT_SYMBOL 276int evdns_base_nameserver_add(struct evdns_base *base, 277 unsigned long int address); 278 279/** 280 Get the number of configured nameservers. 281 282 This returns the number of configured nameservers (not necessarily the 283 number of running nameservers). This is useful for double-checking 284 whether our calls to the various nameserver configuration functions 285 have been successful. 286 287 @param base the evdns_base to which to apply this operation 288 @return the number of configured nameservers 289 @see evdns_base_nameserver_add() 290 */ 291EVENT2_EXPORT_SYMBOL 292int evdns_base_count_nameservers(struct evdns_base *base); 293 294/** 295 Remove all configured nameservers, and suspend all pending resolves. 296 297 Resolves will not necessarily be re-attempted until evdns_base_resume() is called. 298 299 @param base the evdns_base to which to apply this operation 300 @return 0 if successful, or -1 if an error occurred 301 @see evdns_base_resume() 302 */ 303EVENT2_EXPORT_SYMBOL 304int evdns_base_clear_nameservers_and_suspend(struct evdns_base *base); 305 306 307/** 308 Resume normal operation and continue any suspended resolve requests. 309 310 Re-attempt resolves left in limbo after an earlier call to 311 evdns_base_clear_nameservers_and_suspend(). 312 313 @param base the evdns_base to which to apply this operation 314 @return 0 if successful, or -1 if an error occurred 315 @see evdns_base_clear_nameservers_and_suspend() 316 */ 317EVENT2_EXPORT_SYMBOL 318int evdns_base_resume(struct evdns_base *base); 319 320/** 321 Add a nameserver by string address. 322 323 This function parses a n IPv4 or IPv6 address from a string and adds it as a 324 nameserver. It supports the following formats: 325 - [IPv6Address]:port 326 - [IPv6Address] 327 - IPv6Address 328 - IPv4Address:port 329 - IPv4Address 330 331 If no port is specified, it defaults to 53. 332 333 @param base the evdns_base to which to apply this operation 334 @return 0 if successful, or -1 if an error occurred 335 @see evdns_base_nameserver_add() 336 */ 337EVENT2_EXPORT_SYMBOL 338int evdns_base_nameserver_ip_add(struct evdns_base *base, 339 const char *ip_as_string); 340 341/** 342 Add a nameserver by sockaddr. 343 **/ 344EVENT2_EXPORT_SYMBOL 345int 346evdns_base_nameserver_sockaddr_add(struct evdns_base *base, 347 const struct sockaddr *sa, ev_socklen_t len, unsigned flags); 348 349struct evdns_request; 350 351/** 352 Lookup an A record for a given name. 353 354 @param base the evdns_base to which to apply this operation 355 @param name a DNS hostname 356 @param flags either 0, or DNS_QUERY_NO_SEARCH to disable searching for this query. 357 @param callback a callback function to invoke when the request is completed 358 @param ptr an argument to pass to the callback function 359 @return an evdns_request object if successful, or NULL if an error occurred. 360 @see evdns_resolve_ipv6(), evdns_resolve_reverse(), evdns_resolve_reverse_ipv6(), evdns_cancel_request() 361 */ 362EVENT2_EXPORT_SYMBOL 363struct evdns_request *evdns_base_resolve_ipv4(struct evdns_base *base, const char *name, int flags, evdns_callback_type callback, void *ptr); 364 365/** 366 Lookup an AAAA record for a given name. 367 368 @param base the evdns_base to which to apply this operation 369 @param name a DNS hostname 370 @param flags either 0, or DNS_QUERY_NO_SEARCH to disable searching for this query. 371 @param callback a callback function to invoke when the request is completed 372 @param ptr an argument to pass to the callback function 373 @return an evdns_request object if successful, or NULL if an error occurred. 374 @see evdns_resolve_ipv4(), evdns_resolve_reverse(), evdns_resolve_reverse_ipv6(), evdns_cancel_request() 375 */ 376EVENT2_EXPORT_SYMBOL 377struct evdns_request *evdns_base_resolve_ipv6(struct evdns_base *base, const char *name, int flags, evdns_callback_type callback, void *ptr); 378 379struct in_addr; 380struct in6_addr; 381 382/** 383 Lookup a PTR record for a given IP address. 384 385 @param base the evdns_base to which to apply this operation 386 @param in an IPv4 address 387 @param flags either 0, or DNS_QUERY_NO_SEARCH to disable searching for this query. 388 @param callback a callback function to invoke when the request is completed 389 @param ptr an argument to pass to the callback function 390 @return an evdns_request object if successful, or NULL if an error occurred. 391 @see evdns_resolve_reverse_ipv6(), evdns_cancel_request() 392 */ 393EVENT2_EXPORT_SYMBOL 394struct evdns_request *evdns_base_resolve_reverse(struct evdns_base *base, const struct in_addr *in, int flags, evdns_callback_type callback, void *ptr); 395 396 397/** 398 Lookup a PTR record for a given IPv6 address. 399 400 @param base the evdns_base to which to apply this operation 401 @param in an IPv6 address 402 @param flags either 0, or DNS_QUERY_NO_SEARCH to disable searching for this query. 403 @param callback a callback function to invoke when the request is completed 404 @param ptr an argument to pass to the callback function 405 @return an evdns_request object if successful, or NULL if an error occurred. 406 @see evdns_resolve_reverse_ipv6(), evdns_cancel_request() 407 */ 408EVENT2_EXPORT_SYMBOL 409struct evdns_request *evdns_base_resolve_reverse_ipv6(struct evdns_base *base, const struct in6_addr *in, int flags, evdns_callback_type callback, void *ptr); 410 411/** 412 Cancels a pending DNS resolution request. 413 414 @param base the evdns_base that was used to make the request 415 @param req the evdns_request that was returned by calling a resolve function 416 @see evdns_base_resolve_ipv4(), evdns_base_resolve_ipv6, evdns_base_resolve_reverse 417*/ 418EVENT2_EXPORT_SYMBOL 419void evdns_cancel_request(struct evdns_base *base, struct evdns_request *req); 420 421/** 422 Set the value of a configuration option. 423 424 The currently available configuration options are: 425 426 ndots, timeout, max-timeouts, max-inflight, attempts, randomize-case, 427 bind-to, initial-probe-timeout, getaddrinfo-allow-skew. 428 429 In versions before Libevent 2.0.3-alpha, the option name needed to end with 430 a colon. 431 432 @param base the evdns_base to which to apply this operation 433 @param option the name of the configuration option to be modified 434 @param val the value to be set 435 @return 0 if successful, or -1 if an error occurred 436 */ 437EVENT2_EXPORT_SYMBOL 438int evdns_base_set_option(struct evdns_base *base, const char *option, const char *val); 439 440 441/** 442 Parse a resolv.conf file. 443 444 The 'flags' parameter determines what information is parsed from the 445 resolv.conf file. See the man page for resolv.conf for the format of this 446 file. 447 448 The following directives are not parsed from the file: sortlist, rotate, 449 no-check-names, inet6, debug. 450 451 If this function encounters an error, the possible return values are: 1 = 452 failed to open file, 2 = failed to stat file, 3 = file too large, 4 = out of 453 memory, 5 = short read from file, 6 = no nameservers listed in the file 454 455 @param base the evdns_base to which to apply this operation 456 @param flags any of DNS_OPTION_NAMESERVERS|DNS_OPTION_SEARCH|DNS_OPTION_MISC| 457 DNS_OPTION_HOSTSFILE|DNS_OPTIONS_ALL 458 @param filename the path to the resolv.conf file 459 @return 0 if successful, or various positive error codes if an error 460 occurred (see above) 461 @see resolv.conf(3), evdns_config_windows_nameservers() 462 */ 463EVENT2_EXPORT_SYMBOL 464int evdns_base_resolv_conf_parse(struct evdns_base *base, int flags, const char *const filename); 465 466/** 467 Load an /etc/hosts-style file from 'hosts_fname' into 'base'. 468 469 If hosts_fname is NULL, add minimal entries for localhost, and nothing 470 else. 471 472 Note that only evdns_getaddrinfo uses the /etc/hosts entries. 473 474 This function does not replace previously loaded hosts entries; to do that, 475 call evdns_base_clear_host_addresses first. 476 477 Return 0 on success, negative on failure. 478*/ 479EVENT2_EXPORT_SYMBOL 480int evdns_base_load_hosts(struct evdns_base *base, const char *hosts_fname); 481 482/** 483 Obtain nameserver information using the Windows API. 484 485 Attempt to configure a set of nameservers based on platform settings on 486 a win32 host. Preferentially tries to use GetNetworkParams; if that fails, 487 looks in the registry. 488 489 @return 0 if successful, or -1 if an error occurred 490 @see evdns_resolv_conf_parse() 491 */ 492#ifdef _WIN32 493EVENT2_EXPORT_SYMBOL 494int evdns_base_config_windows_nameservers(struct evdns_base *); 495#define EVDNS_BASE_CONFIG_WINDOWS_NAMESERVERS_IMPLEMENTED 496#endif 497 498 499/** 500 Clear the list of search domains. 501 */ 502EVENT2_EXPORT_SYMBOL 503void evdns_base_search_clear(struct evdns_base *base); 504 505 506/** 507 Add a domain to the list of search domains 508 509 @param domain the domain to be added to the search list 510 */ 511EVENT2_EXPORT_SYMBOL 512void evdns_base_search_add(struct evdns_base *base, const char *domain); 513 514 515/** 516 Set the 'ndots' parameter for searches. 517 518 Sets the number of dots which, when found in a name, causes 519 the first query to be without any search domain. 520 521 @param ndots the new ndots parameter 522 */ 523EVENT2_EXPORT_SYMBOL 524void evdns_base_search_ndots_set(struct evdns_base *base, const int ndots); 525 526/** 527 A callback that is invoked when a log message is generated 528 529 @param is_warning indicates if the log message is a 'warning' 530 @param msg the content of the log message 531 */ 532typedef void (*evdns_debug_log_fn_type)(int is_warning, const char *msg); 533 534 535/** 536 Set the callback function to handle DNS log messages. If this 537 callback is not set, evdns log messages are handled with the regular 538 Libevent logging system. 539 540 @param fn the callback to be invoked when a log message is generated 541 */ 542EVENT2_EXPORT_SYMBOL 543void evdns_set_log_fn(evdns_debug_log_fn_type fn); 544 545/** 546 Set a callback that will be invoked to generate transaction IDs. By 547 default, we pick transaction IDs based on the current clock time, which 548 is bad for security. 549 550 @param fn the new callback, or NULL to use the default. 551 552 NOTE: This function has no effect in Libevent 2.0.4-alpha and later, 553 since Libevent now provides its own secure RNG. 554 */ 555EVENT2_EXPORT_SYMBOL 556void evdns_set_transaction_id_fn(ev_uint16_t (*fn)(void)); 557 558/** 559 Set a callback used to generate random bytes. By default, we use 560 the same function as passed to evdns_set_transaction_id_fn to generate 561 bytes two at a time. If a function is provided here, it's also used 562 to generate transaction IDs. 563 564 NOTE: This function has no effect in Libevent 2.0.4-alpha and later, 565 since Libevent now provides its own secure RNG. 566*/ 567EVENT2_EXPORT_SYMBOL 568void evdns_set_random_bytes_fn(void (*fn)(char *, size_t)); 569 570/* 571 * Functions used to implement a DNS server. 572 */ 573 574struct evdns_server_request; 575struct evdns_server_question; 576 577/** 578 A callback to implement a DNS server. The callback function receives a DNS 579 request. It should then optionally add a number of answers to the reply 580 using the evdns_server_request_add_*_reply functions, before calling either 581 evdns_server_request_respond to send the reply back, or 582 evdns_server_request_drop to decline to answer the request. 583 584 @param req A newly received request 585 @param user_data A pointer that was passed to 586 evdns_add_server_port_with_base(). 587 */ 588typedef void (*evdns_request_callback_fn_type)(struct evdns_server_request *, void *); 589#define EVDNS_ANSWER_SECTION 0 590#define EVDNS_AUTHORITY_SECTION 1 591#define EVDNS_ADDITIONAL_SECTION 2 592 593#define EVDNS_TYPE_A 1 594#define EVDNS_TYPE_NS 2 595#define EVDNS_TYPE_CNAME 5 596#define EVDNS_TYPE_SOA 6 597#define EVDNS_TYPE_PTR 12 598#define EVDNS_TYPE_MX 15 599#define EVDNS_TYPE_TXT 16 600#define EVDNS_TYPE_AAAA 28 601 602#define EVDNS_QTYPE_AXFR 252 603#define EVDNS_QTYPE_ALL 255 604 605#define EVDNS_CLASS_INET 1 606 607/* flags that can be set in answers; as part of the err parameter */ 608#define EVDNS_FLAGS_AA 0x400 609#define EVDNS_FLAGS_RD 0x080 610 611/** Create a new DNS server port. 612 613 @param base The event base to handle events for the server port. 614 @param socket A UDP socket to accept DNS requests. 615 @param flags Always 0 for now. 616 @param callback A function to invoke whenever we get a DNS request 617 on the socket. 618 @param user_data Data to pass to the callback. 619 @return an evdns_server_port structure for this server port. 620 */ 621EVENT2_EXPORT_SYMBOL 622struct 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); 623/** Close down a DNS server port, and free associated structures. */ 624EVENT2_EXPORT_SYMBOL 625void evdns_close_server_port(struct evdns_server_port *port); 626 627/** Sets some flags in a reply we're building. 628 Allows setting of the AA or RD flags 629 */ 630EVENT2_EXPORT_SYMBOL 631void evdns_server_request_set_flags(struct evdns_server_request *req, int flags); 632 633/* Functions to add an answer to an in-progress DNS reply. 634 */ 635EVENT2_EXPORT_SYMBOL 636int 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); 637EVENT2_EXPORT_SYMBOL 638int evdns_server_request_add_a_reply(struct evdns_server_request *req, const char *name, int n, const void *addrs, int ttl); 639EVENT2_EXPORT_SYMBOL 640int evdns_server_request_add_aaaa_reply(struct evdns_server_request *req, const char *name, int n, const void *addrs, int ttl); 641EVENT2_EXPORT_SYMBOL 642int evdns_server_request_add_ptr_reply(struct evdns_server_request *req, struct in_addr *in, const char *inaddr_name, const char *hostname, int ttl); 643EVENT2_EXPORT_SYMBOL 644int evdns_server_request_add_cname_reply(struct evdns_server_request *req, const char *name, const char *cname, int ttl); 645 646/** 647 Send back a response to a DNS request, and free the request structure. 648*/ 649EVENT2_EXPORT_SYMBOL 650int evdns_server_request_respond(struct evdns_server_request *req, int err); 651/** 652 Free a DNS request without sending back a reply. 653*/ 654EVENT2_EXPORT_SYMBOL 655int evdns_server_request_drop(struct evdns_server_request *req); 656struct sockaddr; 657/** 658 Get the address that made a DNS request. 659 */ 660EVENT2_EXPORT_SYMBOL 661int evdns_server_request_get_requesting_addr(struct evdns_server_request *req, struct sockaddr *sa, int addr_len); 662 663/** Callback for evdns_getaddrinfo. */ 664typedef void (*evdns_getaddrinfo_cb)(int result, struct evutil_addrinfo *res, void *arg); 665 666struct evdns_base; 667struct evdns_getaddrinfo_request; 668/** Make a non-blocking getaddrinfo request using the dns_base in 'dns_base'. 669 * 670 * If we can answer the request immediately (with an error or not!), then we 671 * invoke cb immediately and return NULL. Otherwise we return 672 * an evdns_getaddrinfo_request and invoke cb later. 673 * 674 * When the callback is invoked, we pass as its first argument the error code 675 * that getaddrinfo would return (or 0 for no error). As its second argument, 676 * we pass the evutil_addrinfo structures we found (or NULL on error). We 677 * pass 'arg' as the third argument. 678 * 679 * Limitations: 680 * 681 * - The AI_V4MAPPED and AI_ALL flags are not currently implemented. 682 * - For ai_socktype, we only handle SOCKTYPE_STREAM, SOCKTYPE_UDP, and 0. 683 * - For ai_protocol, we only handle IPPROTO_TCP, IPPROTO_UDP, and 0. 684 */ 685EVENT2_EXPORT_SYMBOL 686struct evdns_getaddrinfo_request *evdns_getaddrinfo( 687 struct evdns_base *dns_base, 688 const char *nodename, const char *servname, 689 const struct evutil_addrinfo *hints_in, 690 evdns_getaddrinfo_cb cb, void *arg); 691 692/* Cancel an in-progress evdns_getaddrinfo. This MUST NOT be called after the 693 * getaddrinfo's callback has been invoked. The resolves will be canceled, 694 * and the callback will be invoked with the error EVUTIL_EAI_CANCEL. */ 695EVENT2_EXPORT_SYMBOL 696void evdns_getaddrinfo_cancel(struct evdns_getaddrinfo_request *req); 697 698/** 699 Retrieve the address of the 'idx'th configured nameserver. 700 701 @param base The evdns_base to examine. 702 @param idx The index of the nameserver to get the address of. 703 @param sa A location to receive the server's address. 704 @param len The number of bytes available at sa. 705 706 @return the number of bytes written into sa on success. On failure, returns 707 -1 if idx is greater than the number of configured nameservers, or a 708 value greater than 'len' if len was not high enough. 709 */ 710EVENT2_EXPORT_SYMBOL 711int evdns_base_get_nameserver_addr(struct evdns_base *base, int idx, 712 struct sockaddr *sa, ev_socklen_t len); 713 714#ifdef __cplusplus 715} 716#endif 717 718#endif /* !EVENT2_DNS_H_INCLUDED_ */ 719