1 /* $NetBSD: dns.h,v 1.1.1.4 2021/04/07 02:43:14 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 142 extern "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 /* Allow searching */ 184 #define DNS_OPTION_SEARCH 1 185 /* Parse "nameserver" and add default if no such section */ 186 #define DNS_OPTION_NAMESERVERS 2 187 /* Parse additional options like: 188 * - timeout: 189 * - getaddrinfo-allow-skew: 190 * - max-timeouts: 191 * - max-inflight: 192 * - attempts: 193 * - randomize-case: 194 * - initial-probe-timeout: 195 */ 196 #define DNS_OPTION_MISC 4 197 /* Load hosts file (i.e. "/etc/hosts") */ 198 #define DNS_OPTION_HOSTSFILE 8 199 /** 200 * All above: 201 * - DNS_OPTION_SEARCH 202 * - DNS_OPTION_NAMESERVERS 203 * - DNS_OPTION_MISC 204 * - DNS_OPTION_HOSTSFILE 205 */ 206 #define DNS_OPTIONS_ALL ( \ 207 DNS_OPTION_SEARCH | \ 208 DNS_OPTION_NAMESERVERS | \ 209 DNS_OPTION_MISC | \ 210 DNS_OPTION_HOSTSFILE | \ 211 0 \ 212 ) 213 /* Do not "default" nameserver (i.e. "127.0.0.1:53") if there is no nameservers 214 * in resolv.conf, (iff DNS_OPTION_NAMESERVERS is set) */ 215 #define DNS_OPTION_NAMESERVERS_NO_DEFAULT 16 216 217 /* Obsolete name for DNS_QUERY_NO_SEARCH */ 218 #define DNS_NO_SEARCH DNS_QUERY_NO_SEARCH 219 220 /** 221 * The callback that contains the results from a lookup. 222 * - result is one of the DNS_ERR_* values (DNS_ERR_NONE for success) 223 * - type is either DNS_IPv4_A or DNS_PTR or DNS_IPv6_AAAA 224 * - count contains the number of addresses of form type 225 * - ttl is the number of seconds the resolution may be cached for. 226 * - addresses needs to be cast according to type. It will be an array of 227 * 4-byte sequences for ipv4, or an array of 16-byte sequences for ipv6, 228 * or a nul-terminated string for PTR. 229 */ 230 typedef void (*evdns_callback_type) (int result, char type, int count, int ttl, void *addresses, void *arg); 231 232 struct evdns_base; 233 struct event_base; 234 235 /** Flag for evdns_base_new: process resolv.conf. */ 236 #define EVDNS_BASE_INITIALIZE_NAMESERVERS 1 237 /** Flag for evdns_base_new: Do not prevent the libevent event loop from 238 * exiting when we have no active dns requests. */ 239 #define EVDNS_BASE_DISABLE_WHEN_INACTIVE 0x8000 240 /** Flag for evdns_base_new: If EVDNS_BASE_INITIALIZE_NAMESERVERS isset, do not 241 * add default nameserver if there are no nameservers in resolv.conf 242 * @see DNS_OPTION_NAMESERVERS_NO_DEFAULT */ 243 #define EVDNS_BASE_NAMESERVERS_NO_DEFAULT 0x10000 244 245 /** 246 Initialize the asynchronous DNS library. 247 248 This function initializes support for non-blocking name resolution by 249 calling evdns_resolv_conf_parse() on UNIX and 250 evdns_config_windows_nameservers() on Windows. 251 252 @param event_base the event base to associate the dns client with 253 @param flags any of EVDNS_BASE_INITIALIZE_NAMESERVERS| 254 EVDNS_BASE_DISABLE_WHEN_INACTIVE|EVDNS_BASE_NAMESERVERS_NO_DEFAULT 255 @return evdns_base object if successful, or NULL if an error occurred. 256 @see evdns_base_free() 257 */ 258 EVENT2_EXPORT_SYMBOL 259 struct evdns_base * evdns_base_new(struct event_base *event_base, int initialize_nameservers); 260 261 262 /** 263 Shut down the asynchronous DNS resolver and terminate all active requests. 264 265 If the 'fail_requests' option is enabled, all active requests will return 266 an empty result with the error flag set to DNS_ERR_SHUTDOWN. Otherwise, 267 the requests will be silently discarded. 268 269 @param evdns_base the evdns base to free 270 @param fail_requests if zero, active requests will be aborted; if non-zero, 271 active requests will return DNS_ERR_SHUTDOWN. 272 @see evdns_base_new() 273 */ 274 EVENT2_EXPORT_SYMBOL 275 void evdns_base_free(struct evdns_base *base, int fail_requests); 276 277 /** 278 Remove all hosts entries that have been loaded into the event_base via 279 evdns_base_load_hosts or via event_base_resolv_conf_parse. 280 281 @param evdns_base the evdns base to remove outdated host addresses from 282 */ 283 EVENT2_EXPORT_SYMBOL 284 void evdns_base_clear_host_addresses(struct evdns_base *base); 285 286 /** 287 Convert a DNS error code to a string. 288 289 @param err the DNS error code 290 @return a string containing an explanation of the error code 291 */ 292 EVENT2_EXPORT_SYMBOL 293 const char *evdns_err_to_string(int err); 294 295 296 /** 297 Add a nameserver. 298 299 The address should be an IPv4 address in network byte order. 300 The type of address is chosen so that it matches in_addr.s_addr. 301 302 @param base the evdns_base to which to add the name server 303 @param address an IP address in network byte order 304 @return 0 if successful, or -1 if an error occurred 305 @see evdns_base_nameserver_ip_add() 306 */ 307 EVENT2_EXPORT_SYMBOL 308 int evdns_base_nameserver_add(struct evdns_base *base, 309 unsigned long int address); 310 311 /** 312 Get the number of configured nameservers. 313 314 This returns the number of configured nameservers (not necessarily the 315 number of running nameservers). This is useful for double-checking 316 whether our calls to the various nameserver configuration functions 317 have been successful. 318 319 @param base the evdns_base to which to apply this operation 320 @return the number of configured nameservers 321 @see evdns_base_nameserver_add() 322 */ 323 EVENT2_EXPORT_SYMBOL 324 int evdns_base_count_nameservers(struct evdns_base *base); 325 326 /** 327 Remove all configured nameservers, and suspend all pending resolves. 328 329 Resolves will not necessarily be re-attempted until evdns_base_resume() is called. 330 331 @param base the evdns_base to which to apply this operation 332 @return 0 if successful, or -1 if an error occurred 333 @see evdns_base_resume() 334 */ 335 EVENT2_EXPORT_SYMBOL 336 int evdns_base_clear_nameservers_and_suspend(struct evdns_base *base); 337 338 339 /** 340 Resume normal operation and continue any suspended resolve requests. 341 342 Re-attempt resolves left in limbo after an earlier call to 343 evdns_base_clear_nameservers_and_suspend(). 344 345 @param base the evdns_base to which to apply this operation 346 @return 0 if successful, or -1 if an error occurred 347 @see evdns_base_clear_nameservers_and_suspend() 348 */ 349 EVENT2_EXPORT_SYMBOL 350 int evdns_base_resume(struct evdns_base *base); 351 352 /** 353 Add a nameserver by string address. 354 355 This function parses a n IPv4 or IPv6 address from a string and adds it as a 356 nameserver. It supports the following formats: 357 - [IPv6Address]:port 358 - [IPv6Address] 359 - IPv6Address 360 - IPv4Address:port 361 - IPv4Address 362 363 If no port is specified, it defaults to 53. 364 365 @param base the evdns_base to which to apply this operation 366 @return 0 if successful, or -1 if an error occurred 367 @see evdns_base_nameserver_add() 368 */ 369 EVENT2_EXPORT_SYMBOL 370 int evdns_base_nameserver_ip_add(struct evdns_base *base, 371 const char *ip_as_string); 372 373 /** 374 Add a nameserver by sockaddr. 375 **/ 376 EVENT2_EXPORT_SYMBOL 377 int 378 evdns_base_nameserver_sockaddr_add(struct evdns_base *base, 379 const struct sockaddr *sa, ev_socklen_t len, unsigned flags); 380 381 struct evdns_request; 382 383 /** 384 Lookup an A record for a given name. 385 386 @param base the evdns_base to which to apply this operation 387 @param name a DNS hostname 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_ipv6(), evdns_resolve_reverse(), evdns_resolve_reverse_ipv6(), evdns_cancel_request() 393 */ 394 EVENT2_EXPORT_SYMBOL 395 struct evdns_request *evdns_base_resolve_ipv4(struct evdns_base *base, const char *name, int flags, evdns_callback_type callback, void *ptr); 396 397 /** 398 Lookup an AAAA record for a given name. 399 400 @param base the evdns_base to which to apply this operation 401 @param name a DNS hostname 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_ipv4(), evdns_resolve_reverse(), evdns_resolve_reverse_ipv6(), evdns_cancel_request() 407 */ 408 EVENT2_EXPORT_SYMBOL 409 struct evdns_request *evdns_base_resolve_ipv6(struct evdns_base *base, const char *name, int flags, evdns_callback_type callback, void *ptr); 410 411 struct in_addr; 412 struct in6_addr; 413 414 /** 415 Lookup a PTR record for a given IP address. 416 417 @param base the evdns_base to which to apply this operation 418 @param in an IPv4 address 419 @param flags either 0, or DNS_QUERY_NO_SEARCH to disable searching for this query. 420 @param callback a callback function to invoke when the request is completed 421 @param ptr an argument to pass to the callback function 422 @return an evdns_request object if successful, or NULL if an error occurred. 423 @see evdns_resolve_reverse_ipv6(), evdns_cancel_request() 424 */ 425 EVENT2_EXPORT_SYMBOL 426 struct evdns_request *evdns_base_resolve_reverse(struct evdns_base *base, const struct in_addr *in, int flags, evdns_callback_type callback, void *ptr); 427 428 429 /** 430 Lookup a PTR record for a given IPv6 address. 431 432 @param base the evdns_base to which to apply this operation 433 @param in an IPv6 address 434 @param flags either 0, or DNS_QUERY_NO_SEARCH to disable searching for this query. 435 @param callback a callback function to invoke when the request is completed 436 @param ptr an argument to pass to the callback function 437 @return an evdns_request object if successful, or NULL if an error occurred. 438 @see evdns_resolve_reverse_ipv6(), evdns_cancel_request() 439 */ 440 EVENT2_EXPORT_SYMBOL 441 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); 442 443 /** 444 Cancels a pending DNS resolution request. 445 446 @param base the evdns_base that was used to make the request 447 @param req the evdns_request that was returned by calling a resolve function 448 @see evdns_base_resolve_ipv4(), evdns_base_resolve_ipv6, evdns_base_resolve_reverse 449 */ 450 EVENT2_EXPORT_SYMBOL 451 void evdns_cancel_request(struct evdns_base *base, struct evdns_request *req); 452 453 /** 454 Set the value of a configuration option. 455 456 The currently available configuration options are: 457 458 ndots, timeout, max-timeouts, max-inflight, attempts, randomize-case, 459 bind-to, initial-probe-timeout, getaddrinfo-allow-skew, 460 so-rcvbuf, so-sndbuf. 461 462 In versions before Libevent 2.0.3-alpha, the option name needed to end with 463 a colon. 464 465 @param base the evdns_base to which to apply this operation 466 @param option the name of the configuration option to be modified 467 @param val the value to be set 468 @return 0 if successful, or -1 if an error occurred 469 */ 470 EVENT2_EXPORT_SYMBOL 471 int evdns_base_set_option(struct evdns_base *base, const char *option, const char *val); 472 473 474 /** 475 Parse a resolv.conf file. 476 477 The 'flags' parameter determines what information is parsed from the 478 resolv.conf file. See the man page for resolv.conf for the format of this 479 file. 480 481 The following directives are not parsed from the file: sortlist, rotate, 482 no-check-names, inet6, debug. 483 484 If this function encounters an error, the possible return values are: 1 = 485 failed to open file, 2 = failed to stat file, 3 = file too large, 4 = out of 486 memory, 5 = short read from file, 6 = no nameservers listed in the file 487 488 @param base the evdns_base to which to apply this operation 489 @param flags any of DNS_OPTION_NAMESERVERS|DNS_OPTION_SEARCH|DNS_OPTION_MISC| 490 DNS_OPTION_HOSTSFILE|DNS_OPTIONS_ALL|DNS_OPTION_NAMESERVERS_NO_DEFAULT 491 @param filename the path to the resolv.conf file 492 @return 0 if successful, or various positive error codes if an error 493 occurred (see above) 494 @see resolv.conf(3), evdns_config_windows_nameservers() 495 */ 496 EVENT2_EXPORT_SYMBOL 497 int evdns_base_resolv_conf_parse(struct evdns_base *base, int flags, const char *const filename); 498 499 /** 500 Load an /etc/hosts-style file from 'hosts_fname' into 'base'. 501 502 If hosts_fname is NULL, add minimal entries for localhost, and nothing 503 else. 504 505 Note that only evdns_getaddrinfo uses the /etc/hosts entries. 506 507 This function does not replace previously loaded hosts entries; to do that, 508 call evdns_base_clear_host_addresses first. 509 510 Return 0 on success, negative on failure. 511 */ 512 EVENT2_EXPORT_SYMBOL 513 int evdns_base_load_hosts(struct evdns_base *base, const char *hosts_fname); 514 515 #if defined(EVENT_IN_DOXYGEN_) || defined(_WIN32) 516 /** 517 Obtain nameserver information using the Windows API. 518 519 Attempt to configure a set of nameservers based on platform settings on 520 a win32 host. Preferentially tries to use GetNetworkParams; if that fails, 521 looks in the registry. 522 523 @return 0 if successful, or -1 if an error occurred 524 @see evdns_resolv_conf_parse() 525 */ 526 EVENT2_EXPORT_SYMBOL 527 int evdns_base_config_windows_nameservers(struct evdns_base *); 528 #define EVDNS_BASE_CONFIG_WINDOWS_NAMESERVERS_IMPLEMENTED 529 #endif 530 531 532 /** 533 Clear the list of search domains. 534 */ 535 EVENT2_EXPORT_SYMBOL 536 void evdns_base_search_clear(struct evdns_base *base); 537 538 539 /** 540 Add a domain to the list of search domains 541 542 @param domain the domain to be added to the search list 543 */ 544 EVENT2_EXPORT_SYMBOL 545 void evdns_base_search_add(struct evdns_base *base, const char *domain); 546 547 548 /** 549 Set the 'ndots' parameter for searches. 550 551 Sets the number of dots which, when found in a name, causes 552 the first query to be without any search domain. 553 554 @param ndots the new ndots parameter 555 */ 556 EVENT2_EXPORT_SYMBOL 557 void evdns_base_search_ndots_set(struct evdns_base *base, const int ndots); 558 559 /** 560 A callback that is invoked when a log message is generated 561 562 @param is_warning indicates if the log message is a 'warning' 563 @param msg the content of the log message 564 */ 565 typedef void (*evdns_debug_log_fn_type)(int is_warning, const char *msg); 566 567 568 /** 569 Set the callback function to handle DNS log messages. If this 570 callback is not set, evdns log messages are handled with the regular 571 Libevent logging system. 572 573 @param fn the callback to be invoked when a log message is generated 574 */ 575 EVENT2_EXPORT_SYMBOL 576 void evdns_set_log_fn(evdns_debug_log_fn_type fn); 577 578 /** 579 Set a callback that will be invoked to generate transaction IDs. By 580 default, we pick transaction IDs based on the current clock time, which 581 is bad for security. 582 583 @param fn the new callback, or NULL to use the default. 584 585 NOTE: This function has no effect in Libevent 2.0.4-alpha and later, 586 since Libevent now provides its own secure RNG. 587 */ 588 EVENT2_EXPORT_SYMBOL 589 void evdns_set_transaction_id_fn(ev_uint16_t (*fn)(void)); 590 591 /** 592 Set a callback used to generate random bytes. By default, we use 593 the same function as passed to evdns_set_transaction_id_fn to generate 594 bytes two at a time. If a function is provided here, it's also used 595 to generate transaction IDs. 596 597 NOTE: This function has no effect in Libevent 2.0.4-alpha and later, 598 since Libevent now provides its own secure RNG. 599 */ 600 EVENT2_EXPORT_SYMBOL 601 void evdns_set_random_bytes_fn(void (*fn)(char *, size_t)); 602 603 /* 604 * Functions used to implement a DNS server. 605 */ 606 607 struct evdns_server_request; 608 struct evdns_server_question; 609 610 /** 611 A callback to implement a DNS server. The callback function receives a DNS 612 request. It should then optionally add a number of answers to the reply 613 using the evdns_server_request_add_*_reply functions, before calling either 614 evdns_server_request_respond to send the reply back, or 615 evdns_server_request_drop to decline to answer the request. 616 617 @param req A newly received request 618 @param user_data A pointer that was passed to 619 evdns_add_server_port_with_base(). 620 */ 621 typedef void (*evdns_request_callback_fn_type)(struct evdns_server_request *, void *); 622 #define EVDNS_ANSWER_SECTION 0 623 #define EVDNS_AUTHORITY_SECTION 1 624 #define EVDNS_ADDITIONAL_SECTION 2 625 626 #define EVDNS_TYPE_A 1 627 #define EVDNS_TYPE_NS 2 628 #define EVDNS_TYPE_CNAME 5 629 #define EVDNS_TYPE_SOA 6 630 #define EVDNS_TYPE_PTR 12 631 #define EVDNS_TYPE_MX 15 632 #define EVDNS_TYPE_TXT 16 633 #define EVDNS_TYPE_AAAA 28 634 635 #define EVDNS_QTYPE_AXFR 252 636 #define EVDNS_QTYPE_ALL 255 637 638 #define EVDNS_CLASS_INET 1 639 640 /* flags that can be set in answers; as part of the err parameter */ 641 #define EVDNS_FLAGS_AA 0x400 642 #define EVDNS_FLAGS_RD 0x080 643 644 /** Create a new DNS server port. 645 646 @param base The event base to handle events for the server port. 647 @param socket A UDP socket to accept DNS requests. 648 @param flags Always 0 for now. 649 @param callback A function to invoke whenever we get a DNS request 650 on the socket. 651 @param user_data Data to pass to the callback. 652 @return an evdns_server_port structure for this server port or NULL if 653 an error occurred. 654 */ 655 EVENT2_EXPORT_SYMBOL 656 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); 657 /** Close down a DNS server port, and free associated structures. */ 658 EVENT2_EXPORT_SYMBOL 659 void evdns_close_server_port(struct evdns_server_port *port); 660 661 /** Sets some flags in a reply we're building. 662 Allows setting of the AA or RD flags 663 */ 664 EVENT2_EXPORT_SYMBOL 665 void evdns_server_request_set_flags(struct evdns_server_request *req, int flags); 666 667 /* Functions to add an answer to an in-progress DNS reply. 668 */ 669 EVENT2_EXPORT_SYMBOL 670 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); 671 EVENT2_EXPORT_SYMBOL 672 int evdns_server_request_add_a_reply(struct evdns_server_request *req, const char *name, int n, const void *addrs, int ttl); 673 EVENT2_EXPORT_SYMBOL 674 int evdns_server_request_add_aaaa_reply(struct evdns_server_request *req, const char *name, int n, const void *addrs, int ttl); 675 EVENT2_EXPORT_SYMBOL 676 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); 677 EVENT2_EXPORT_SYMBOL 678 int evdns_server_request_add_cname_reply(struct evdns_server_request *req, const char *name, const char *cname, int ttl); 679 680 /** 681 Send back a response to a DNS request, and free the request structure. 682 */ 683 EVENT2_EXPORT_SYMBOL 684 int evdns_server_request_respond(struct evdns_server_request *req, int err); 685 /** 686 Free a DNS request without sending back a reply. 687 */ 688 EVENT2_EXPORT_SYMBOL 689 int evdns_server_request_drop(struct evdns_server_request *req); 690 struct sockaddr; 691 /** 692 Get the address that made a DNS request. 693 */ 694 EVENT2_EXPORT_SYMBOL 695 int evdns_server_request_get_requesting_addr(struct evdns_server_request *req, struct sockaddr *sa, int addr_len); 696 697 /** Callback for evdns_getaddrinfo. */ 698 typedef void (*evdns_getaddrinfo_cb)(int result, struct evutil_addrinfo *res, void *arg); 699 700 struct evdns_base; 701 struct evdns_getaddrinfo_request; 702 /** Make a non-blocking getaddrinfo request using the dns_base in 'dns_base'. 703 * 704 * If we can answer the request immediately (with an error or not!), then we 705 * invoke cb immediately and return NULL. Otherwise we return 706 * an evdns_getaddrinfo_request and invoke cb later. 707 * 708 * When the callback is invoked, we pass as its first argument the error code 709 * that getaddrinfo would return (or 0 for no error). As its second argument, 710 * we pass the evutil_addrinfo structures we found (or NULL on error). We 711 * pass 'arg' as the third argument. 712 * 713 * Limitations: 714 * 715 * - The AI_V4MAPPED and AI_ALL flags are not currently implemented. 716 * - For ai_socktype, we only handle SOCKTYPE_STREAM, SOCKTYPE_UDP, and 0. 717 * - For ai_protocol, we only handle IPPROTO_TCP, IPPROTO_UDP, and 0. 718 */ 719 EVENT2_EXPORT_SYMBOL 720 struct evdns_getaddrinfo_request *evdns_getaddrinfo( 721 struct evdns_base *dns_base, 722 const char *nodename, const char *servname, 723 const struct evutil_addrinfo *hints_in, 724 evdns_getaddrinfo_cb cb, void *arg); 725 726 /* Cancel an in-progress evdns_getaddrinfo. This MUST NOT be called after the 727 * getaddrinfo's callback has been invoked. The resolves will be canceled, 728 * and the callback will be invoked with the error EVUTIL_EAI_CANCEL. */ 729 EVENT2_EXPORT_SYMBOL 730 void evdns_getaddrinfo_cancel(struct evdns_getaddrinfo_request *req); 731 732 /** 733 Retrieve the address of the 'idx'th configured nameserver. 734 735 @param base The evdns_base to examine. 736 @param idx The index of the nameserver to get the address of. 737 @param sa A location to receive the server's address. 738 @param len The number of bytes available at sa. 739 740 @return the number of bytes written into sa on success. On failure, returns 741 -1 if idx is greater than the number of configured nameservers, or a 742 value greater than 'len' if len was not high enough. 743 */ 744 EVENT2_EXPORT_SYMBOL 745 int evdns_base_get_nameserver_addr(struct evdns_base *base, int idx, 746 struct sockaddr *sa, ev_socklen_t len); 747 748 #ifdef __cplusplus 749 } 750 #endif 751 752 #endif /* !EVENT2_DNS_H_INCLUDED_ */ 753