1 /* 2 * Copyright (c) 2006-2007 Niels Provos <provos (at) 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 (at) 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_INCLUDED_ 136 #define EVENT2_DNS_H_INCLUDED_ 137 138 #include <event2/visibility.h> 139 140 #ifdef __cplusplus 141 extern "C" { 142 #endif 143 144 /* For integer types. */ 145 #include <event2/util.h> 146 147 /** Error codes 0-5 are as described in RFC 1035. */ 148 #define DNS_ERR_NONE 0 149 /** The name server was unable to interpret the query */ 150 #define DNS_ERR_FORMAT 1 151 /** The name server was unable to process this query due to a problem with the 152 * name server */ 153 #define DNS_ERR_SERVERFAILED 2 154 /** The domain name does not exist */ 155 #define DNS_ERR_NOTEXIST 3 156 /** The name server does not support the requested kind of query */ 157 #define DNS_ERR_NOTIMPL 4 158 /** The name server refuses to reform the specified operation for policy 159 * reasons */ 160 #define DNS_ERR_REFUSED 5 161 /** The reply was truncated or ill-formatted */ 162 #define DNS_ERR_TRUNCATED 65 163 /** An unknown error occurred */ 164 #define DNS_ERR_UNKNOWN 66 165 /** Communication with the server timed out */ 166 #define DNS_ERR_TIMEOUT 67 167 /** The request was canceled because the DNS subsystem was shut down. */ 168 #define DNS_ERR_SHUTDOWN 68 169 /** The request was canceled via a call to evdns_cancel_request */ 170 #define DNS_ERR_CANCEL 69 171 /** There were no answers and no error condition in the DNS packet. 172 * This can happen when you ask for an address that exists, but a record 173 * type that doesn't. */ 174 #define DNS_ERR_NODATA 70 175 176 #define DNS_IPv4_A 1 177 #define DNS_PTR 2 178 #define DNS_IPv6_AAAA 3 179 180 #define DNS_QUERY_NO_SEARCH 1 181 182 #define DNS_OPTION_SEARCH 1 183 #define DNS_OPTION_NAMESERVERS 2 184 #define DNS_OPTION_MISC 4 185 #define DNS_OPTION_HOSTSFILE 8 186 #define DNS_OPTIONS_ALL 15 187 188 /* Obsolete name for DNS_QUERY_NO_SEARCH */ 189 #define DNS_NO_SEARCH DNS_QUERY_NO_SEARCH 190 191 /** 192 * The callback that contains the results from a lookup. 193 * - result is one of the DNS_ERR_* values (DNS_ERR_NONE for success) 194 * - type is either DNS_IPv4_A or DNS_PTR or DNS_IPv6_AAAA 195 * - count contains the number of addresses of form type 196 * - ttl is the number of seconds the resolution may be cached for. 197 * - addresses needs to be cast according to type. It will be an array of 198 * 4-byte sequences for ipv4, or an array of 16-byte sequences for ipv6, 199 * or a nul-terminated string for PTR. 200 */ 201 typedef void (*evdns_callback_type) (int result, char type, int count, int ttl, void *addresses, void *arg); 202 203 struct evdns_base; 204 struct event_base; 205 206 /** Flag for evdns_base_new: process resolv.conf. */ 207 #define EVDNS_BASE_INITIALIZE_NAMESERVERS 1 208 /** Flag for evdns_base_new: Do not prevent the libevent event loop from 209 * exiting when we have no active dns requests. */ 210 #define EVDNS_BASE_DISABLE_WHEN_INACTIVE 0x8000 211 212 /** 213 Initialize the asynchronous DNS library. 214 215 This function initializes support for non-blocking name resolution by 216 calling evdns_resolv_conf_parse() on UNIX and 217 evdns_config_windows_nameservers() on Windows. 218 219 @param event_base the event base to associate the dns client with 220 @param flags any of EVDNS_BASE_INITIALIZE_NAMESERVERS| 221 EVDNS_BASE_DISABLE_WHEN_INACTIVE 222 @return evdns_base object if successful, or NULL if an error occurred. 223 @see evdns_base_free() 224 */ 225 EVENT2_EXPORT_SYMBOL 226 struct evdns_base * evdns_base_new(struct event_base *event_base, int initialize_nameservers); 227 228 229 /** 230 Shut down the asynchronous DNS resolver and terminate all active requests. 231 232 If the 'fail_requests' option is enabled, all active requests will return 233 an empty result with the error flag set to DNS_ERR_SHUTDOWN. Otherwise, 234 the requests will be silently discarded. 235 236 @param evdns_base the evdns base to free 237 @param fail_requests if zero, active requests will be aborted; if non-zero, 238 active requests will return DNS_ERR_SHUTDOWN. 239 @see evdns_base_new() 240 */ 241 EVENT2_EXPORT_SYMBOL 242 void evdns_base_free(struct evdns_base *base, int fail_requests); 243 244 /** 245 Remove all hosts entries that have been loaded into the event_base via 246 evdns_base_load_hosts or via event_base_resolv_conf_parse. 247 248 @param evdns_base the evdns base to remove outdated host addresses from 249 */ 250 EVENT2_EXPORT_SYMBOL 251 void evdns_base_clear_host_addresses(struct evdns_base *base); 252 253 /** 254 Convert a DNS error code to a string. 255 256 @param err the DNS error code 257 @return a string containing an explanation of the error code 258 */ 259 EVENT2_EXPORT_SYMBOL 260 const char *evdns_err_to_string(int err); 261 262 263 /** 264 Add a nameserver. 265 266 The address should be an IPv4 address in network byte order. 267 The type of address is chosen so that it matches in_addr.s_addr. 268 269 @param base the evdns_base to which to add the name server 270 @param address an IP address in network byte order 271 @return 0 if successful, or -1 if an error occurred 272 @see evdns_base_nameserver_ip_add() 273 */ 274 EVENT2_EXPORT_SYMBOL 275 int evdns_base_nameserver_add(struct evdns_base *base, 276 unsigned long int address); 277 278 /** 279 Get the number of configured nameservers. 280 281 This returns the number of configured nameservers (not necessarily the 282 number of running nameservers). This is useful for double-checking 283 whether our calls to the various nameserver configuration functions 284 have been successful. 285 286 @param base the evdns_base to which to apply this operation 287 @return the number of configured nameservers 288 @see evdns_base_nameserver_add() 289 */ 290 EVENT2_EXPORT_SYMBOL 291 int evdns_base_count_nameservers(struct evdns_base *base); 292 293 /** 294 Remove all configured nameservers, and suspend all pending resolves. 295 296 Resolves will not necessarily be re-attempted until evdns_base_resume() is called. 297 298 @param base the evdns_base to which to apply this operation 299 @return 0 if successful, or -1 if an error occurred 300 @see evdns_base_resume() 301 */ 302 EVENT2_EXPORT_SYMBOL 303 int evdns_base_clear_nameservers_and_suspend(struct evdns_base *base); 304 305 306 /** 307 Resume normal operation and continue any suspended resolve requests. 308 309 Re-attempt resolves left in limbo after an earlier call to 310 evdns_base_clear_nameservers_and_suspend(). 311 312 @param base the evdns_base to which to apply this operation 313 @return 0 if successful, or -1 if an error occurred 314 @see evdns_base_clear_nameservers_and_suspend() 315 */ 316 EVENT2_EXPORT_SYMBOL 317 int evdns_base_resume(struct evdns_base *base); 318 319 /** 320 Add a nameserver by string address. 321 322 This function parses a n IPv4 or IPv6 address from a string and adds it as a 323 nameserver. It supports the following formats: 324 - [IPv6Address]:port 325 - [IPv6Address] 326 - IPv6Address 327 - IPv4Address:port 328 - IPv4Address 329 330 If no port is specified, it defaults to 53. 331 332 @param base the evdns_base to which to apply this operation 333 @return 0 if successful, or -1 if an error occurred 334 @see evdns_base_nameserver_add() 335 */ 336 EVENT2_EXPORT_SYMBOL 337 int evdns_base_nameserver_ip_add(struct evdns_base *base, 338 const char *ip_as_string); 339 340 /** 341 Add a nameserver by sockaddr. 342 **/ 343 EVENT2_EXPORT_SYMBOL 344 int 345 evdns_base_nameserver_sockaddr_add(struct evdns_base *base, 346 const struct sockaddr *sa, ev_socklen_t len, unsigned flags); 347 348 struct evdns_request; 349 350 /** 351 Lookup an A record for a given name. 352 353 @param base the evdns_base to which to apply this operation 354 @param name a DNS hostname 355 @param flags either 0, or DNS_QUERY_NO_SEARCH to disable searching for this query. 356 @param callback a callback function to invoke when the request is completed 357 @param ptr an argument to pass to the callback function 358 @return an evdns_request object if successful, or NULL if an error occurred. 359 @see evdns_resolve_ipv6(), evdns_resolve_reverse(), evdns_resolve_reverse_ipv6(), evdns_cancel_request() 360 */ 361 EVENT2_EXPORT_SYMBOL 362 struct evdns_request *evdns_base_resolve_ipv4(struct evdns_base *base, const char *name, int flags, evdns_callback_type callback, void *ptr); 363 364 /** 365 Lookup an AAAA record for a given name. 366 367 @param base the evdns_base to which to apply this operation 368 @param name a DNS hostname 369 @param flags either 0, or DNS_QUERY_NO_SEARCH to disable searching for this query. 370 @param callback a callback function to invoke when the request is completed 371 @param ptr an argument to pass to the callback function 372 @return an evdns_request object if successful, or NULL if an error occurred. 373 @see evdns_resolve_ipv4(), evdns_resolve_reverse(), evdns_resolve_reverse_ipv6(), evdns_cancel_request() 374 */ 375 EVENT2_EXPORT_SYMBOL 376 struct evdns_request *evdns_base_resolve_ipv6(struct evdns_base *base, const char *name, int flags, evdns_callback_type callback, void *ptr); 377 378 struct in_addr; 379 struct in6_addr; 380 381 /** 382 Lookup a PTR record for a given IP address. 383 384 @param base the evdns_base to which to apply this operation 385 @param in an IPv4 address 386 @param flags either 0, or DNS_QUERY_NO_SEARCH to disable searching for this query. 387 @param callback a callback function to invoke when the request is completed 388 @param ptr an argument to pass to the callback function 389 @return an evdns_request object if successful, or NULL if an error occurred. 390 @see evdns_resolve_reverse_ipv6(), evdns_cancel_request() 391 */ 392 EVENT2_EXPORT_SYMBOL 393 struct evdns_request *evdns_base_resolve_reverse(struct evdns_base *base, const struct in_addr *in, int flags, evdns_callback_type callback, void *ptr); 394 395 396 /** 397 Lookup a PTR record for a given IPv6 address. 398 399 @param base the evdns_base to which to apply this operation 400 @param in an IPv6 address 401 @param flags either 0, or DNS_QUERY_NO_SEARCH to disable searching for this query. 402 @param callback a callback function to invoke when the request is completed 403 @param ptr an argument to pass to the callback function 404 @return an evdns_request object if successful, or NULL if an error occurred. 405 @see evdns_resolve_reverse_ipv6(), evdns_cancel_request() 406 */ 407 EVENT2_EXPORT_SYMBOL 408 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); 409 410 /** 411 Cancels a pending DNS resolution request. 412 413 @param base the evdns_base that was used to make the request 414 @param req the evdns_request that was returned by calling a resolve function 415 @see evdns_base_resolve_ipv4(), evdns_base_resolve_ipv6, evdns_base_resolve_reverse 416 */ 417 EVENT2_EXPORT_SYMBOL 418 void evdns_cancel_request(struct evdns_base *base, struct evdns_request *req); 419 420 /** 421 Set the value of a configuration option. 422 423 The currently available configuration options are: 424 425 ndots, timeout, max-timeouts, max-inflight, attempts, randomize-case, 426 bind-to, initial-probe-timeout, getaddrinfo-allow-skew. 427 428 In versions before Libevent 2.0.3-alpha, the option name needed to end with 429 a colon. 430 431 @param base the evdns_base to which to apply this operation 432 @param option the name of the configuration option to be modified 433 @param val the value to be set 434 @return 0 if successful, or -1 if an error occurred 435 */ 436 EVENT2_EXPORT_SYMBOL 437 int evdns_base_set_option(struct evdns_base *base, const char *option, const char *val); 438 439 440 /** 441 Parse a resolv.conf file. 442 443 The 'flags' parameter determines what information is parsed from the 444 resolv.conf file. See the man page for resolv.conf for the format of this 445 file. 446 447 The following directives are not parsed from the file: sortlist, rotate, 448 no-check-names, inet6, debug. 449 450 If this function encounters an error, the possible return values are: 1 = 451 failed to open file, 2 = failed to stat file, 3 = file too large, 4 = out of 452 memory, 5 = short read from file, 6 = no nameservers listed in the file 453 454 @param base the evdns_base to which to apply this operation 455 @param flags any of DNS_OPTION_NAMESERVERS|DNS_OPTION_SEARCH|DNS_OPTION_MISC| 456 DNS_OPTION_HOSTSFILE|DNS_OPTIONS_ALL 457 @param filename the path to the resolv.conf file 458 @return 0 if successful, or various positive error codes if an error 459 occurred (see above) 460 @see resolv.conf(3), evdns_config_windows_nameservers() 461 */ 462 EVENT2_EXPORT_SYMBOL 463 int evdns_base_resolv_conf_parse(struct evdns_base *base, int flags, const char *const filename); 464 465 /** 466 Load an /etc/hosts-style file from 'hosts_fname' into 'base'. 467 468 If hosts_fname is NULL, add minimal entries for localhost, and nothing 469 else. 470 471 Note that only evdns_getaddrinfo uses the /etc/hosts entries. 472 473 This function does not replace previously loaded hosts entries; to do that, 474 call evdns_base_clear_host_addresses first. 475 476 Return 0 on success, negative on failure. 477 */ 478 EVENT2_EXPORT_SYMBOL 479 int evdns_base_load_hosts(struct evdns_base *base, const char *hosts_fname); 480 481 /** 482 Obtain nameserver information using the Windows API. 483 484 Attempt to configure a set of nameservers based on platform settings on 485 a win32 host. Preferentially tries to use GetNetworkParams; if that fails, 486 looks in the registry. 487 488 @return 0 if successful, or -1 if an error occurred 489 @see evdns_resolv_conf_parse() 490 */ 491 #ifdef _WIN32 492 EVENT2_EXPORT_SYMBOL 493 int evdns_base_config_windows_nameservers(struct evdns_base *); 494 #define EVDNS_BASE_CONFIG_WINDOWS_NAMESERVERS_IMPLEMENTED 495 #endif 496 497 498 /** 499 Clear the list of search domains. 500 */ 501 EVENT2_EXPORT_SYMBOL 502 void evdns_base_search_clear(struct evdns_base *base); 503 504 505 /** 506 Add a domain to the list of search domains 507 508 @param domain the domain to be added to the search list 509 */ 510 EVENT2_EXPORT_SYMBOL 511 void evdns_base_search_add(struct evdns_base *base, const char *domain); 512 513 514 /** 515 Set the 'ndots' parameter for searches. 516 517 Sets the number of dots which, when found in a name, causes 518 the first query to be without any search domain. 519 520 @param ndots the new ndots parameter 521 */ 522 EVENT2_EXPORT_SYMBOL 523 void evdns_base_search_ndots_set(struct evdns_base *base, const int ndots); 524 525 /** 526 A callback that is invoked when a log message is generated 527 528 @param is_warning indicates if the log message is a 'warning' 529 @param msg the content of the log message 530 */ 531 typedef void (*evdns_debug_log_fn_type)(int is_warning, const char *msg); 532 533 534 /** 535 Set the callback function to handle DNS log messages. If this 536 callback is not set, evdns log messages are handled with the regular 537 Libevent logging system. 538 539 @param fn the callback to be invoked when a log message is generated 540 */ 541 EVENT2_EXPORT_SYMBOL 542 void evdns_set_log_fn(evdns_debug_log_fn_type fn); 543 544 /** 545 Set a callback that will be invoked to generate transaction IDs. By 546 default, we pick transaction IDs based on the current clock time, which 547 is bad for security. 548 549 @param fn the new callback, or NULL to use the default. 550 551 NOTE: This function has no effect in Libevent 2.0.4-alpha and later, 552 since Libevent now provides its own secure RNG. 553 */ 554 EVENT2_EXPORT_SYMBOL 555 void evdns_set_transaction_id_fn(ev_uint16_t (*fn)(void)); 556 557 /** 558 Set a callback used to generate random bytes. By default, we use 559 the same function as passed to evdns_set_transaction_id_fn to generate 560 bytes two at a time. If a function is provided here, it's also used 561 to generate transaction IDs. 562 563 NOTE: This function has no effect in Libevent 2.0.4-alpha and later, 564 since Libevent now provides its own secure RNG. 565 */ 566 EVENT2_EXPORT_SYMBOL 567 void evdns_set_random_bytes_fn(void (*fn)(char *, size_t)); 568 569 /* 570 * Functions used to implement a DNS server. 571 */ 572 573 struct evdns_server_request; 574 struct evdns_server_question; 575 576 /** 577 A callback to implement a DNS server. The callback function receives a DNS 578 request. It should then optionally add a number of answers to the reply 579 using the evdns_server_request_add_*_reply functions, before calling either 580 evdns_server_request_respond to send the reply back, or 581 evdns_server_request_drop to decline to answer the request. 582 583 @param req A newly received request 584 @param user_data A pointer that was passed to 585 evdns_add_server_port_with_base(). 586 */ 587 typedef void (*evdns_request_callback_fn_type)(struct evdns_server_request *, void *); 588 #define EVDNS_ANSWER_SECTION 0 589 #define EVDNS_AUTHORITY_SECTION 1 590 #define EVDNS_ADDITIONAL_SECTION 2 591 592 #define EVDNS_TYPE_A 1 593 #define EVDNS_TYPE_NS 2 594 #define EVDNS_TYPE_CNAME 5 595 #define EVDNS_TYPE_SOA 6 596 #define EVDNS_TYPE_PTR 12 597 #define EVDNS_TYPE_MX 15 598 #define EVDNS_TYPE_TXT 16 599 #define EVDNS_TYPE_AAAA 28 600 601 #define EVDNS_QTYPE_AXFR 252 602 #define EVDNS_QTYPE_ALL 255 603 604 #define EVDNS_CLASS_INET 1 605 606 /* flags that can be set in answers; as part of the err parameter */ 607 #define EVDNS_FLAGS_AA 0x400 608 #define EVDNS_FLAGS_RD 0x080 609 610 /** Create a new DNS server port. 611 612 @param base The event base to handle events for the server port. 613 @param socket A UDP socket to accept DNS requests. 614 @param flags Always 0 for now. 615 @param callback A function to invoke whenever we get a DNS request 616 on the socket. 617 @param user_data Data to pass to the callback. 618 @return an evdns_server_port structure for this server port. 619 */ 620 EVENT2_EXPORT_SYMBOL 621 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); 622 /** Close down a DNS server port, and free associated structures. */ 623 EVENT2_EXPORT_SYMBOL 624 void evdns_close_server_port(struct evdns_server_port *port); 625 626 /** Sets some flags in a reply we're building. 627 Allows setting of the AA or RD flags 628 */ 629 EVENT2_EXPORT_SYMBOL 630 void evdns_server_request_set_flags(struct evdns_server_request *req, int flags); 631 632 /* Functions to add an answer to an in-progress DNS reply. 633 */ 634 EVENT2_EXPORT_SYMBOL 635 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); 636 EVENT2_EXPORT_SYMBOL 637 int evdns_server_request_add_a_reply(struct evdns_server_request *req, const char *name, int n, const void *addrs, int ttl); 638 EVENT2_EXPORT_SYMBOL 639 int evdns_server_request_add_aaaa_reply(struct evdns_server_request *req, const char *name, int n, const void *addrs, int ttl); 640 EVENT2_EXPORT_SYMBOL 641 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); 642 EVENT2_EXPORT_SYMBOL 643 int evdns_server_request_add_cname_reply(struct evdns_server_request *req, const char *name, const char *cname, int ttl); 644 645 /** 646 Send back a response to a DNS request, and free the request structure. 647 */ 648 EVENT2_EXPORT_SYMBOL 649 int evdns_server_request_respond(struct evdns_server_request *req, int err); 650 /** 651 Free a DNS request without sending back a reply. 652 */ 653 EVENT2_EXPORT_SYMBOL 654 int evdns_server_request_drop(struct evdns_server_request *req); 655 struct sockaddr; 656 /** 657 Get the address that made a DNS request. 658 */ 659 EVENT2_EXPORT_SYMBOL 660 int evdns_server_request_get_requesting_addr(struct evdns_server_request *req, struct sockaddr *sa, int addr_len); 661 662 /** Callback for evdns_getaddrinfo. */ 663 typedef void (*evdns_getaddrinfo_cb)(int result, struct evutil_addrinfo *res, void *arg); 664 665 struct evdns_base; 666 struct evdns_getaddrinfo_request; 667 /** Make a non-blocking getaddrinfo request using the dns_base in 'dns_base'. 668 * 669 * If we can answer the request immediately (with an error or not!), then we 670 * invoke cb immediately and return NULL. Otherwise we return 671 * an evdns_getaddrinfo_request and invoke cb later. 672 * 673 * When the callback is invoked, we pass as its first argument the error code 674 * that getaddrinfo would return (or 0 for no error). As its second argument, 675 * we pass the evutil_addrinfo structures we found (or NULL on error). We 676 * pass 'arg' as the third argument. 677 * 678 * Limitations: 679 * 680 * - The AI_V4MAPPED and AI_ALL flags are not currently implemented. 681 * - For ai_socktype, we only handle SOCKTYPE_STREAM, SOCKTYPE_UDP, and 0. 682 * - For ai_protocol, we only handle IPPROTO_TCP, IPPROTO_UDP, and 0. 683 */ 684 EVENT2_EXPORT_SYMBOL 685 struct evdns_getaddrinfo_request *evdns_getaddrinfo( 686 struct evdns_base *dns_base, 687 const char *nodename, const char *servname, 688 const struct evutil_addrinfo *hints_in, 689 evdns_getaddrinfo_cb cb, void *arg); 690 691 /* Cancel an in-progress evdns_getaddrinfo. This MUST NOT be called after the 692 * getaddrinfo's callback has been invoked. The resolves will be canceled, 693 * and the callback will be invoked with the error EVUTIL_EAI_CANCEL. */ 694 EVENT2_EXPORT_SYMBOL 695 void evdns_getaddrinfo_cancel(struct evdns_getaddrinfo_request *req); 696 697 /** 698 Retrieve the address of the 'idx'th configured nameserver. 699 700 @param base The evdns_base to examine. 701 @param idx The index of the nameserver to get the address of. 702 @param sa A location to receive the server's address. 703 @param len The number of bytes available at sa. 704 705 @return the number of bytes written into sa on success. On failure, returns 706 -1 if idx is greater than the number of configured nameservers, or a 707 value greater than 'len' if len was not high enough. 708 */ 709 EVENT2_EXPORT_SYMBOL 710 int evdns_base_get_nameserver_addr(struct evdns_base *base, int idx, 711 struct sockaddr *sa, ev_socklen_t len); 712 713 #ifdef __cplusplus 714 } 715 #endif 716 717 #endif /* !EVENT2_DNS_H_INCLUDED_ */ 718
