1 /* 2 * Copyright (c) 2006-2007 Niels Provos <provos@citi.umich.edu> 3 * Copyright (c) 2007-2012 Niels Provos and Nick Mathewson 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 3. The name of the author may not be used to endorse or promote products 14 * derived from this software without specific prior written permission. 15 * 16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 17 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 18 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 19 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 21 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 22 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 23 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 24 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 25 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 26 */ 27 28 /* 29 * The original DNS code is due to Adam Langley with heavy 30 * modifications by Nick Mathewson. Adam put his DNS software in the 31 * public domain. You can find his original copyright below. Please, 32 * aware that the code as part of Libevent is governed by the 3-clause 33 * BSD license above. 34 * 35 * This software is Public Domain. To view a copy of the public domain dedication, 36 * visit http://creativecommons.org/licenses/publicdomain/ or send a letter to 37 * Creative Commons, 559 Nathan Abbott Way, Stanford, California 94305, USA. 38 * 39 * I ask and expect, but do not require, that all derivative works contain an 40 * attribution similar to: 41 * Parts developed by Adam Langley <agl@imperialviolet.org> 42 * 43 * You may wish to replace the word "Parts" with something else depending on 44 * the amount of original code. 45 * 46 * (Derivative works does not include programs which link against, run or include 47 * the source verbatim in their source distributions) 48 */ 49 50 /** @file event2/dns.h 51 * 52 * Welcome, gentle reader 53 * 54 * Async DNS lookups are really a whole lot harder than they should be, 55 * mostly stemming from the fact that the libc resolver has never been 56 * very good at them. Before you use this library you should see if libc 57 * can do the job for you with the modern async call getaddrinfo_a 58 * (see http://www.imperialviolet.org/page25.html#e498). Otherwise, 59 * please continue. 60 * 61 * The library keeps track of the state of nameservers and will avoid 62 * them when they go down. Otherwise it will round robin between them. 63 * 64 * Quick start guide: 65 * #include "evdns.h" 66 * void callback(int result, char type, int count, int ttl, 67 * void *addresses, void *arg); 68 * evdns_resolv_conf_parse(DNS_OPTIONS_ALL, "/etc/resolv.conf"); 69 * evdns_resolve("www.hostname.com", 0, callback, NULL); 70 * 71 * When the lookup is complete the callback function is called. The 72 * first argument will be one of the DNS_ERR_* defines in evdns.h. 73 * Hopefully it will be DNS_ERR_NONE, in which case type will be 74 * DNS_IPv4_A, count will be the number of IP addresses, ttl is the time 75 * which the data can be cached for (in seconds), addresses will point 76 * to an array of uint32_t's and arg will be whatever you passed to 77 * evdns_resolve. 78 * 79 * Searching: 80 * 81 * In order for this library to be a good replacement for glibc's resolver it 82 * supports searching. This involves setting a list of default domains, in 83 * which names will be queried for. The number of dots in the query name 84 * determines the order in which this list is used. 85 * 86 * Searching appears to be a single lookup from the point of view of the API, 87 * although many DNS queries may be generated from a single call to 88 * evdns_resolve. Searching can also drastically slow down the resolution 89 * of names. 90 * 91 * To disable searching: 92 * 1. Never set it up. If you never call evdns_resolv_conf_parse or 93 * evdns_search_add then no searching will occur. 94 * 95 * 2. If you do call evdns_resolv_conf_parse then don't pass 96 * DNS_OPTION_SEARCH (or DNS_OPTIONS_ALL, which implies it). 97 * 98 * 3. When calling evdns_resolve, pass the DNS_QUERY_NO_SEARCH flag. 99 * 100 * The order of searches depends on the number of dots in the name. If the 101 * number is greater than the ndots setting then the names is first tried 102 * globally. Otherwise each search domain is appended in turn. 103 * 104 * The ndots setting can either be set from a resolv.conf, or by calling 105 * evdns_search_ndots_set. 106 * 107 * For example, with ndots set to 1 (the default) and a search domain list of 108 * ["myhome.net"]: 109 * Query: www 110 * Order: www.myhome.net, www. 111 * 112 * Query: www.abc 113 * Order: www.abc., www.abc.myhome.net 114 * 115 * Internals: 116 * 117 * Requests are kept in two queues. The first is the inflight queue. In 118 * this queue requests have an allocated transaction id and nameserver. 119 * They will soon be transmitted if they haven't already been. 120 * 121 * The second is the waiting queue. The size of the inflight ring is 122 * limited and all other requests wait in waiting queue for space. This 123 * bounds the number of concurrent requests so that we don't flood the 124 * nameserver. Several algorithms require a full walk of the inflight 125 * queue and so bounding its size keeps thing going nicely under huge 126 * (many thousands of requests) loads. 127 * 128 * If a nameserver loses too many requests it is considered down and we 129 * try not to use it. After a while we send a probe to that nameserver 130 * (a lookup for google.com) and, if it replies, we consider it working 131 * again. If the nameserver fails a probe we wait longer to try again 132 * with the next probe. 133 */ 134 135 #ifndef _EVENT2_DNS_H_ 136 #define _EVENT2_DNS_H_ 137 138 #ifdef __cplusplus 139 extern "C" { 140 #endif 141 142 /* For integer types. */ 143 #include <event2/util.h> 144 145 /** Error codes 0-5 are as described in RFC 1035. */ 146 #define DNS_ERR_NONE 0 147 /** The name server was unable to interpret the query */ 148 #define DNS_ERR_FORMAT 1 149 /** The name server was unable to process this query due to a problem with the 150 * name server */ 151 #define DNS_ERR_SERVERFAILED 2 152 /** The domain name does not exist */ 153 #define DNS_ERR_NOTEXIST 3 154 /** The name server does not support the requested kind of query */ 155 #define DNS_ERR_NOTIMPL 4 156 /** The name server refuses to reform the specified operation for policy 157 * reasons */ 158 #define DNS_ERR_REFUSED 5 159 /** The reply was truncated or ill-formatted */ 160 #define DNS_ERR_TRUNCATED 65 161 /** An unknown error occurred */ 162 #define DNS_ERR_UNKNOWN 66 163 /** Communication with the server timed out */ 164 #define DNS_ERR_TIMEOUT 67 165 /** The request was canceled because the DNS subsystem was shut down. */ 166 #define DNS_ERR_SHUTDOWN 68 167 /** The request was canceled via a call to evdns_cancel_request */ 168 #define DNS_ERR_CANCEL 69 169 /** There were no answers and no error condition in the DNS packet. 170 * This can happen when you ask for an address that exists, but a record 171 * type that doesn't. */ 172 #define DNS_ERR_NODATA 70 173 174 #define DNS_IPv4_A 1 175 #define DNS_PTR 2 176 #define DNS_IPv6_AAAA 3 177 178 #define DNS_QUERY_NO_SEARCH 1 179 180 #define DNS_OPTION_SEARCH 1 181 #define DNS_OPTION_NAMESERVERS 2 182 #define DNS_OPTION_MISC 4 183 #define DNS_OPTION_HOSTSFILE 8 184 #define DNS_OPTIONS_ALL 15 185 186 /* Obsolete name for DNS_QUERY_NO_SEARCH */ 187 #define DNS_NO_SEARCH DNS_QUERY_NO_SEARCH 188 189 /** 190 * The callback that contains the results from a lookup. 191 * - result is one of the DNS_ERR_* values (DNS_ERR_NONE for success) 192 * - type is either DNS_IPv4_A or DNS_PTR or DNS_IPv6_AAAA 193 * - count contains the number of addresses of form type 194 * - ttl is the number of seconds the resolution may be cached for. 195 * - addresses needs to be cast according to type. It will be an array of 196 * 4-byte sequences for ipv4, or an array of 16-byte sequences for ipv6, 197 * or a nul-terminated string for PTR. 198 */ 199 typedef void (*evdns_callback_type) (int result, char type, int count, int ttl, void *addresses, void *arg); 200 201 struct evdns_base; 202 struct event_base; 203 204 /** 205 Initialize the asynchronous DNS library. 206 207 This function initializes support for non-blocking name resolution by 208 calling evdns_resolv_conf_parse() on UNIX and 209 evdns_config_windows_nameservers() on Windows. 210 211 @param event_base the event base to associate the dns client with 212 @param initialize_nameservers 1 if resolve.conf processing should occur 213 @return evdns_base object if successful, or NULL if an error occurred. 214 @see evdns_base_free() 215 */ 216 struct evdns_base * evdns_base_new(struct event_base *event_base, int initialize_nameservers); 217 218 219 /** 220 Shut down the asynchronous DNS resolver and terminate all active requests. 221 222 If the 'fail_requests' option is enabled, all active requests will return 223 an empty result with the error flag set to DNS_ERR_SHUTDOWN. Otherwise, 224 the requests will be silently discarded. 225 226 @param evdns_base the evdns base to free 227 @param fail_requests if zero, active requests will be aborted; if non-zero, 228 active requests will return DNS_ERR_SHUTDOWN. 229 @see evdns_base_new() 230 */ 231 void evdns_base_free(struct evdns_base *base, int fail_requests); 232 233 /** 234 Convert a DNS error code to a string. 235 236 @param err the DNS error code 237 @return a string containing an explanation of the error code 238 */ 239 const char *evdns_err_to_string(int err); 240 241 242 /** 243 Add a nameserver. 244 245 The address should be an IPv4 address in network byte order. 246 The type of address is chosen so that it matches in_addr.s_addr. 247 248 @param base the evdns_base to which to add the name server 249 @param address an IP address in network byte order 250 @return 0 if successful, or -1 if an error occurred 251 @see evdns_base_nameserver_ip_add() 252 */ 253 int evdns_base_nameserver_add(struct evdns_base *base, 254 unsigned long int address); 255 256 /** 257 Get the number of configured nameservers. 258 259 This returns the number of configured nameservers (not necessarily the 260 number of running nameservers). This is useful for double-checking 261 whether our calls to the various nameserver configuration functions 262 have been successful. 263 264 @param base the evdns_base to which to apply this operation 265 @return the number of configured nameservers 266 @see evdns_base_nameserver_add() 267 */ 268 int evdns_base_count_nameservers(struct evdns_base *base); 269 270 /** 271 Remove all configured nameservers, and suspend all pending resolves. 272 273 Resolves will not necessarily be re-attempted until evdns_base_resume() is called. 274 275 @param base the evdns_base to which to apply this operation 276 @return 0 if successful, or -1 if an error occurred 277 @see evdns_base_resume() 278 */ 279 int evdns_base_clear_nameservers_and_suspend(struct evdns_base *base); 280 281 282 /** 283 Resume normal operation and continue any suspended resolve requests. 284 285 Re-attempt resolves left in limbo after an earlier call to 286 evdns_base_clear_nameservers_and_suspend(). 287 288 @param base the evdns_base to which to apply this operation 289 @return 0 if successful, or -1 if an error occurred 290 @see evdns_base_clear_nameservers_and_suspend() 291 */ 292 int evdns_base_resume(struct evdns_base *base); 293 294 /** 295 Add a nameserver by string address. 296 297 This function parses a n IPv4 or IPv6 address from a string and adds it as a 298 nameserver. It supports the following formats: 299 - [IPv6Address]:port 300 - [IPv6Address] 301 - IPv6Address 302 - IPv4Address:port 303 - IPv4Address 304 305 If no port is specified, it defaults to 53. 306 307 @param base the evdns_base to which to apply this operation 308 @return 0 if successful, or -1 if an error occurred 309 @see evdns_base_nameserver_add() 310 */ 311 int evdns_base_nameserver_ip_add(struct evdns_base *base, 312 const char *ip_as_string); 313 314 /** 315 Add a nameserver by sockaddr. 316 **/ 317 int 318 evdns_base_nameserver_sockaddr_add(struct evdns_base *base, 319 const struct sockaddr *sa, ev_socklen_t len, unsigned flags); 320 321 struct evdns_request; 322 323 /** 324 Lookup an A record for a given name. 325 326 @param base the evdns_base to which to apply this operation 327 @param name a DNS hostname 328 @param flags either 0, or DNS_QUERY_NO_SEARCH to disable searching for this query. 329 @param callback a callback function to invoke when the request is completed 330 @param ptr an argument to pass to the callback function 331 @return an evdns_request object if successful, or NULL if an error occurred. 332 @see evdns_resolve_ipv6(), evdns_resolve_reverse(), evdns_resolve_reverse_ipv6(), evdns_cancel_request() 333 */ 334 struct evdns_request *evdns_base_resolve_ipv4(struct evdns_base *base, const char *name, int flags, evdns_callback_type callback, void *ptr); 335 336 /** 337 Lookup an AAAA record for a given name. 338 339 @param base the evdns_base to which to apply this operation 340 @param name a DNS hostname 341 @param flags either 0, or DNS_QUERY_NO_SEARCH to disable searching for this query. 342 @param callback a callback function to invoke when the request is completed 343 @param ptr an argument to pass to the callback function 344 @return an evdns_request object if successful, or NULL if an error occurred. 345 @see evdns_resolve_ipv4(), evdns_resolve_reverse(), evdns_resolve_reverse_ipv6(), evdns_cancel_request() 346 */ 347 struct evdns_request *evdns_base_resolve_ipv6(struct evdns_base *base, const char *name, int flags, evdns_callback_type callback, void *ptr); 348 349 struct in_addr; 350 struct in6_addr; 351 352 /** 353 Lookup a PTR record for a given IP address. 354 355 @param base the evdns_base to which to apply this operation 356 @param in an IPv4 address 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_reverse_ipv6(), evdns_cancel_request() 362 */ 363 struct evdns_request *evdns_base_resolve_reverse(struct evdns_base *base, const struct in_addr *in, int flags, evdns_callback_type callback, void *ptr); 364 365 366 /** 367 Lookup a PTR record for a given IPv6 address. 368 369 @param base the evdns_base to which to apply this operation 370 @param in an IPv6 address 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_reverse_ipv6(), evdns_cancel_request() 376 */ 377 struct evdns_request *evdns_base_resolve_reverse_ipv6(struct evdns_base *base, const struct in6_addr *in, int flags, evdns_callback_type callback, void *ptr); 378 379 /** 380 Cancels a pending DNS resolution request. 381 382 @param base the evdns_base that was used to make the request 383 @param req the evdns_request that was returned by calling a resolve function 384 @see evdns_base_resolve_ipv4(), evdns_base_resolve_ipv6, evdns_base_resolve_reverse 385 */ 386 void evdns_cancel_request(struct evdns_base *base, struct evdns_request *req); 387 388 /** 389 Set the value of a configuration option. 390 391 The currently available configuration options are: 392 393 ndots, timeout, max-timeouts, max-inflight, attempts, randomize-case, 394 bind-to, initial-probe-timeout, getaddrinfo-allow-skew. 395 396 In versions before Libevent 2.0.3-alpha, the option name needed to end with 397 a colon. 398 399 @param base the evdns_base to which to apply this operation 400 @param option the name of the configuration option to be modified 401 @param val the value to be set 402 @return 0 if successful, or -1 if an error occurred 403 */ 404 int evdns_base_set_option(struct evdns_base *base, const char *option, const char *val); 405 406 407 /** 408 Parse a resolv.conf file. 409 410 The 'flags' parameter determines what information is parsed from the 411 resolv.conf file. See the man page for resolv.conf for the format of this 412 file. 413 414 The following directives are not parsed from the file: sortlist, rotate, 415 no-check-names, inet6, debug. 416 417 If this function encounters an error, the possible return values are: 1 = 418 failed to open file, 2 = failed to stat file, 3 = file too large, 4 = out of 419 memory, 5 = short read from file, 6 = no nameservers listed in the file 420 421 @param base the evdns_base to which to apply this operation 422 @param flags any of DNS_OPTION_NAMESERVERS|DNS_OPTION_SEARCH|DNS_OPTION_MISC| 423 DNS_OPTION_HOSTSFILE|DNS_OPTIONS_ALL 424 @param filename the path to the resolv.conf file 425 @return 0 if successful, or various positive error codes if an error 426 occurred (see above) 427 @see resolv.conf(3), evdns_config_windows_nameservers() 428 */ 429 int evdns_base_resolv_conf_parse(struct evdns_base *base, int flags, const char *const filename); 430 431 /** 432 Load an /etc/hosts-style file from 'hosts_fname' into 'base'. 433 434 If hosts_fname is NULL, add minimal entries for localhost, and nothing 435 else. 436 437 Note that only evdns_getaddrinfo uses the /etc/hosts entries. 438 439 Return 0 on success, negative on failure. 440 */ 441 int evdns_base_load_hosts(struct evdns_base *base, const char *hosts_fname); 442 443 /** 444 Obtain nameserver information using the Windows API. 445 446 Attempt to configure a set of nameservers based on platform settings on 447 a win32 host. Preferentially tries to use GetNetworkParams; if that fails, 448 looks in the registry. 449 450 @return 0 if successful, or -1 if an error occurred 451 @see evdns_resolv_conf_parse() 452 */ 453 #ifdef WIN32 454 int evdns_base_config_windows_nameservers(struct evdns_base *); 455 #define EVDNS_BASE_CONFIG_WINDOWS_NAMESERVERS_IMPLEMENTED 456 #endif 457 458 459 /** 460 Clear the list of search domains. 461 */ 462 void evdns_base_search_clear(struct evdns_base *base); 463 464 465 /** 466 Add a domain to the list of search domains 467 468 @param domain the domain to be added to the search list 469 */ 470 void evdns_base_search_add(struct evdns_base *base, const char *domain); 471 472 473 /** 474 Set the 'ndots' parameter for searches. 475 476 Sets the number of dots which, when found in a name, causes 477 the first query to be without any search domain. 478 479 @param ndots the new ndots parameter 480 */ 481 void evdns_base_search_ndots_set(struct evdns_base *base, const int ndots); 482 483 /** 484 A callback that is invoked when a log message is generated 485 486 @param is_warning indicates if the log message is a 'warning' 487 @param msg the content of the log message 488 */ 489 typedef void (*evdns_debug_log_fn_type)(int is_warning, const char *msg); 490 491 492 /** 493 Set the callback function to handle DNS log messages. If this 494 callback is not set, evdns log messages are handled with the regular 495 Libevent logging system. 496 497 @param fn the callback to be invoked when a log message is generated 498 */ 499 void evdns_set_log_fn(evdns_debug_log_fn_type fn); 500 501 /** 502 Set a callback that will be invoked to generate transaction IDs. By 503 default, we pick transaction IDs based on the current clock time, which 504 is bad for security. 505 506 @param fn the new callback, or NULL to use the default. 507 508 NOTE: This function has no effect in Libevent 2.0.4-alpha and later, 509 since Libevent now provides its own secure RNG. 510 */ 511 void evdns_set_transaction_id_fn(ev_uint16_t (*fn)(void)); 512 513 /** 514 Set a callback used to generate random bytes. By default, we use 515 the same function as passed to evdns_set_transaction_id_fn to generate 516 bytes two at a time. If a function is provided here, it's also used 517 to generate transaction IDs. 518 519 NOTE: This function has no effect in Libevent 2.0.4-alpha and later, 520 since Libevent now provides its own secure RNG. 521 */ 522 void evdns_set_random_bytes_fn(void (*fn)(char *, size_t)); 523 524 /* 525 * Functions used to implement a DNS server. 526 */ 527 528 struct evdns_server_request; 529 struct evdns_server_question; 530 531 /** 532 A callback to implement a DNS server. The callback function receives a DNS 533 request. It should then optionally add a number of answers to the reply 534 using the evdns_server_request_add_*_reply functions, before calling either 535 evdns_server_request_respond to send the reply back, or 536 evdns_server_request_drop to decline to answer the request. 537 538 @param req A newly received request 539 @param user_data A pointer that was passed to 540 evdns_add_server_port_with_base(). 541 */ 542 typedef void (*evdns_request_callback_fn_type)(struct evdns_server_request *, void *); 543 #define EVDNS_ANSWER_SECTION 0 544 #define EVDNS_AUTHORITY_SECTION 1 545 #define EVDNS_ADDITIONAL_SECTION 2 546 547 #define EVDNS_TYPE_A 1 548 #define EVDNS_TYPE_NS 2 549 #define EVDNS_TYPE_CNAME 5 550 #define EVDNS_TYPE_SOA 6 551 #define EVDNS_TYPE_PTR 12 552 #define EVDNS_TYPE_MX 15 553 #define EVDNS_TYPE_TXT 16 554 #define EVDNS_TYPE_AAAA 28 555 556 #define EVDNS_QTYPE_AXFR 252 557 #define EVDNS_QTYPE_ALL 255 558 559 #define EVDNS_CLASS_INET 1 560 561 /* flags that can be set in answers; as part of the err parameter */ 562 #define EVDNS_FLAGS_AA 0x400 563 #define EVDNS_FLAGS_RD 0x080 564 565 /** Create a new DNS server port. 566 567 @param base The event base to handle events for the server port. 568 @param socket A UDP socket to accept DNS requests. 569 @param flags Always 0 for now. 570 @param callback A function to invoke whenever we get a DNS request 571 on the socket. 572 @param user_data Data to pass to the callback. 573 @return an evdns_server_port structure for this server port. 574 */ 575 struct 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); 576 /** Close down a DNS server port, and free associated structures. */ 577 void evdns_close_server_port(struct evdns_server_port *port); 578 579 /** Sets some flags in a reply we're building. 580 Allows setting of the AA or RD flags 581 */ 582 void evdns_server_request_set_flags(struct evdns_server_request *req, int flags); 583 584 /* Functions to add an answer to an in-progress DNS reply. 585 */ 586 int 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); 587 int evdns_server_request_add_a_reply(struct evdns_server_request *req, const char *name, int n, const void *addrs, int ttl); 588 int evdns_server_request_add_aaaa_reply(struct evdns_server_request *req, const char *name, int n, const void *addrs, int ttl); 589 int evdns_server_request_add_ptr_reply(struct evdns_server_request *req, struct in_addr *in, const char *inaddr_name, const char *hostname, int ttl); 590 int evdns_server_request_add_cname_reply(struct evdns_server_request *req, const char *name, const char *cname, int ttl); 591 592 /** 593 Send back a response to a DNS request, and free the request structure. 594 */ 595 int evdns_server_request_respond(struct evdns_server_request *req, int err); 596 /** 597 Free a DNS request without sending back a reply. 598 */ 599 int evdns_server_request_drop(struct evdns_server_request *req); 600 struct sockaddr; 601 /** 602 Get the address that made a DNS request. 603 */ 604 int evdns_server_request_get_requesting_addr(struct evdns_server_request *_req, struct sockaddr *sa, int addr_len); 605 606 /** Callback for evdns_getaddrinfo. */ 607 typedef void (*evdns_getaddrinfo_cb)(int result, struct evutil_addrinfo *res, void *arg); 608 609 struct evdns_base; 610 struct evdns_getaddrinfo_request; 611 /** Make a non-blocking getaddrinfo request using the dns_base in 'dns_base'. 612 * 613 * If we can answer the request immediately (with an error or not!), then we 614 * invoke cb immediately and return NULL. Otherwise we return 615 * an evdns_getaddrinfo_request and invoke cb later. 616 * 617 * When the callback is invoked, we pass as its first argument the error code 618 * that getaddrinfo would return (or 0 for no error). As its second argument, 619 * we pass the evutil_addrinfo structures we found (or NULL on error). We 620 * pass 'arg' as the third argument. 621 * 622 * Limitations: 623 * 624 * - The AI_V4MAPPED and AI_ALL flags are not currently implemented. 625 * - For ai_socktype, we only handle SOCKTYPE_STREAM, SOCKTYPE_UDP, and 0. 626 * - For ai_protocol, we only handle IPPROTO_TCP, IPPROTO_UDP, and 0. 627 */ 628 struct evdns_getaddrinfo_request *evdns_getaddrinfo( 629 struct evdns_base *dns_base, 630 const char *nodename, const char *servname, 631 const struct evutil_addrinfo *hints_in, 632 evdns_getaddrinfo_cb cb, void *arg); 633 634 /* Cancel an in-progress evdns_getaddrinfo. This MUST NOT be called after the 635 * getaddrinfo's callback has been invoked. The resolves will be canceled, 636 * and the callback will be invoked with the error EVUTIL_EAI_CANCEL. */ 637 void evdns_getaddrinfo_cancel(struct evdns_getaddrinfo_request *req); 638 639 #ifdef __cplusplus 640 } 641 #endif 642 643 #endif /* !_EVENT2_DNS_H_ */ 644