external/bsd/libevent/dist/include/event2/dns.h

   1 /*      $NetBSD: dns.h,v 1.1.1.2 2015/01/29 06:38:28 spz Exp $  */
   2 /*      $NetBSD: dns.h,v 1.1.1.2 2015/01/29 06:38:28 spz Exp $  */
   3 /*
   4  * Copyright (c) 2006-2007 Niels Provos <provos@citi.umich.edu>
   5  * Copyright (c) 2007-2012 Niels Provos and Nick Mathewson
   6  *
   7  * Redistribution and use in source and binary forms, with or without
   8  * modification, are permitted provided that the following conditions
   9  * are met:
  10  * 1. Redistributions of source code must retain the above copyright
  11  *    notice, this list of conditions and the following disclaimer.
  12  * 2. Redistributions in binary form must reproduce the above copyright
  13  *    notice, this list of conditions and the following disclaimer in the
  14  *    documentation and/or other materials provided with the distribution.
  15  * 3. The name of the author may not be used to endorse or promote products
  16  *    derived from this software without specific prior written permission.
  17  *
  18  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  19  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  20  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  21  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  22  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  23  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  24  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  25  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  26  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  27  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  28  */
  29
  30 /*
  31  * The original DNS code is due to Adam Langley with heavy
  32  * modifications by Nick Mathewson.  Adam put his DNS software in the
  33  * public domain.  You can find his original copyright below.  Please,
  34  * aware that the code as part of Libevent is governed by the 3-clause
  35  * BSD license above.
  36  *
  37  * This software is Public Domain. To view a copy of the public domain dedication,
  38  * visit http://creativecommons.org/licenses/publicdomain/ or send a letter to
  39  * Creative Commons, 559 Nathan Abbott Way, Stanford, California 94305, USA.
  40  *
  41  * I ask and expect, but do not require, that all derivative works contain an
  42  * attribution similar to:
  43  *     Parts developed by Adam Langley <agl@imperialviolet.org>
  44  *
  45  * You may wish to replace the word "Parts" with something else depending on
  46  * the amount of original code.
  47  *
  48  * (Derivative works does not include programs which link against, run or include
  49  * the source verbatim in their source distributions)
  50  */
  51
  52 /** @file event2/dns.h
  53  *
  54  * Welcome, gentle reader
  55  *
  56  * Async DNS lookups are really a whole lot harder than they should be,
  57  * mostly stemming from the fact that the libc resolver has never been
  58  * very good at them. Before you use this library you should see if libc
  59  * can do the job for you with the modern async call getaddrinfo_a
  60  * (see http://www.imperialviolet.org/page25.html#e498). Otherwise,
  61  * please continue.
  62  *
  63  * The library keeps track of the state of nameservers and will avoid
  64  * them when they go down. Otherwise it will round robin between them.
  65  *
  66  * Quick start guide:
  67  *   #include "evdns.h"
  68  *   void callback(int result, char type, int count, int ttl,
  69  *               void *addresses, void *arg);
  70  *   evdns_resolv_conf_parse(DNS_OPTIONS_ALL, "/etc/resolv.conf");
  71  *   evdns_resolve("www.hostname.com", 0, callback, NULL);
  72  *
  73  * When the lookup is complete the callback function is called. The
  74  * first argument will be one of the DNS_ERR_* defines in evdns.h.
  75  * Hopefully it will be DNS_ERR_NONE, in which case type will be
  76  * DNS_IPv4_A, count will be the number of IP addresses, ttl is the time
  77  * which the data can be cached for (in seconds), addresses will point
  78  * to an array of uint32_t's and arg will be whatever you passed to
  79  * evdns_resolve.
  80  *
  81  * Searching:
  82  *
  83  * In order for this library to be a good replacement for glibc's resolver it
  84  * supports searching. This involves setting a list of default domains, in
  85  * which names will be queried for. The number of dots in the query name
  86  * determines the order in which this list is used.
  87  *
  88  * Searching appears to be a single lookup from the point of view of the API,
  89  * although many DNS queries may be generated from a single call to
  90  * evdns_resolve. Searching can also drastically slow down the resolution
  91  * of names.
  92  *
  93  * To disable searching:
  94  *   1. Never set it up. If you never call evdns_resolv_conf_parse or
  95  *   evdns_search_add then no searching will occur.
  96  *
  97  *   2. If you do call evdns_resolv_conf_parse then don't pass
  98  *   DNS_OPTION_SEARCH (or DNS_OPTIONS_ALL, which implies it).
  99  *
 100  *   3. When calling evdns_resolve, pass the DNS_QUERY_NO_SEARCH flag.
 101  *
 102  * The order of searches depends on the number of dots in the name. If the
 103  * number is greater than the ndots setting then the names is first tried
 104  * globally. Otherwise each search domain is appended in turn.
 105  *
 106  * The ndots setting can either be set from a resolv.conf, or by calling
 107  * evdns_search_ndots_set.
 108  *
 109  * For example, with ndots set to 1 (the default) and a search domain list of
 110  * ["myhome.net"]:
 111  *  Query: www
 112  *  Order: www.myhome.net, www.
 113  *
 114  *  Query: www.abc
 115  *  Order: www.abc., www.abc.myhome.net
 116  *
 117  * Internals:
 118  *
 119  * Requests are kept in two queues. The first is the inflight queue. In
 120  * this queue requests have an allocated transaction id and nameserver.
 121  * They will soon be transmitted if they haven't already been.
 122  *
 123  * The second is the waiting queue. The size of the inflight ring is
 124  * limited and all other requests wait in waiting queue for space. This
 125  * bounds the number of concurrent requests so that we don't flood the
 126  * nameserver. Several algorithms require a full walk of the inflight
 127  * queue and so bounding its size keeps thing going nicely under huge
 128  * (many thousands of requests) loads.
 129  *
 130  * If a nameserver loses too many requests it is considered down and we
 131  * try not to use it. After a while we send a probe to that nameserver
 132  * (a lookup for google.com) and, if it replies, we consider it working
 133  * again. If the nameserver fails a probe we wait longer to try again
 134  * with the next probe.
 135  */
 136
 137 #ifndef _EVENT2_DNS_H_
 138 #define _EVENT2_DNS_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 /**
 207   Initialize the asynchronous DNS library.
 208
 209   This function initializes support for non-blocking name resolution by
 210   calling evdns_resolv_conf_parse() on UNIX and
 211   evdns_config_windows_nameservers() on Windows.
 212
 213   @param event_base the event base to associate the dns client with
 214   @param initialize_nameservers 1 if resolve.conf processing should occur
 215   @return evdns_base object if successful, or NULL if an error occurred.
 216   @see evdns_base_free()
 217  */
 218 struct evdns_base * evdns_base_new(struct event_base *event_base, int initialize_nameservers);
 219
 220
 221 /**
 222   Shut down the asynchronous DNS resolver and terminate all active requests.
 223
 224   If the 'fail_requests' option is enabled, all active requests will return
 225   an empty result with the error flag set to DNS_ERR_SHUTDOWN. Otherwise,
 226   the requests will be silently discarded.
 227
 228   @param evdns_base the evdns base to free
 229   @param fail_requests if zero, active requests will be aborted; if non-zero,
 230                 active requests will return DNS_ERR_SHUTDOWN.
 231   @see evdns_base_new()
 232  */
 233 void evdns_base_free(struct evdns_base *base, int fail_requests);
 234
 235 /**
 236   Convert a DNS error code to a string.
 237
 238   @param err the DNS error code
 239   @return a string containing an explanation of the error code
 240 */
 241 const char *evdns_err_to_string(int err);
 242
 243
 244 /**
 245   Add a nameserver.
 246
 247   The address should be an IPv4 address in network byte order.
 248   The type of address is chosen so that it matches in_addr.s_addr.
 249
 250   @param base the evdns_base to which to add the name server
 251   @param address an IP address in network byte order
 252   @return 0 if successful, or -1 if an error occurred
 253   @see evdns_base_nameserver_ip_add()
 254  */
 255 int evdns_base_nameserver_add(struct evdns_base *base,
 256     unsigned long int address);
 257
 258 /**
 259   Get the number of configured nameservers.
 260
 261   This returns the number of configured nameservers (not necessarily the
 262   number of running nameservers).  This is useful for double-checking
 263   whether our calls to the various nameserver configuration functions
 264   have been successful.
 265
 266   @param base the evdns_base to which to apply this operation
 267   @return the number of configured nameservers
 268   @see evdns_base_nameserver_add()
 269  */
 270 int evdns_base_count_nameservers(struct evdns_base *base);
 271
 272 /**
 273   Remove all configured nameservers, and suspend all pending resolves.
 274
 275   Resolves will not necessarily be re-attempted until evdns_base_resume() is called.
 276
 277   @param base the evdns_base to which to apply this operation
 278   @return 0 if successful, or -1 if an error occurred
 279   @see evdns_base_resume()
 280  */
 281 int evdns_base_clear_nameservers_and_suspend(struct evdns_base *base);
 282
 283
 284 /**
 285   Resume normal operation and continue any suspended resolve requests.
 286
 287   Re-attempt resolves left in limbo after an earlier call to
 288   evdns_base_clear_nameservers_and_suspend().
 289
 290   @param base the evdns_base to which to apply this operation
 291   @return 0 if successful, or -1 if an error occurred
 292   @see evdns_base_clear_nameservers_and_suspend()
 293  */
 294 int evdns_base_resume(struct evdns_base *base);
 295
 296 /**
 297   Add a nameserver by string address.
 298
 299   This function parses a n IPv4 or IPv6 address from a string and adds it as a
 300   nameserver.  It supports the following formats:
 301   - [IPv6Address]:port
 302   - [IPv6Address]
 303   - IPv6Address
 304   - IPv4Address:port
 305   - IPv4Address
 306
 307   If no port is specified, it defaults to 53.
 308
 309   @param base the evdns_base to which to apply this operation
 310   @return 0 if successful, or -1 if an error occurred
 311   @see evdns_base_nameserver_add()
 312  */
 313 int evdns_base_nameserver_ip_add(struct evdns_base *base,
 314     const char *ip_as_string);
 315
 316 /**
 317    Add a nameserver by sockaddr.
 318  **/
 319 int
 320 evdns_base_nameserver_sockaddr_add(struct evdns_base *base,
 321     const struct sockaddr *sa, ev_socklen_t len, unsigned flags);
 322
 323 struct evdns_request;
 324
 325 /**
 326   Lookup an A record for a given name.
 327
 328   @param base the evdns_base to which to apply this operation
 329   @param name a DNS hostname
 330   @param flags either 0, or DNS_QUERY_NO_SEARCH to disable searching for this query.
 331   @param callback a callback function to invoke when the request is completed
 332   @param ptr an argument to pass to the callback function
 333   @return an evdns_request object if successful, or NULL if an error occurred.
 334   @see evdns_resolve_ipv6(), evdns_resolve_reverse(), evdns_resolve_reverse_ipv6(), evdns_cancel_request()
 335  */
 336 struct evdns_request *evdns_base_resolve_ipv4(struct evdns_base *base, const char *name, int flags, evdns_callback_type callback, void *ptr);
 337
 338 /**
 339   Lookup an AAAA record for a given name.
 340
 341   @param base the evdns_base to which to apply this operation
 342   @param name a DNS hostname
 343   @param flags either 0, or DNS_QUERY_NO_SEARCH to disable searching for this query.
 344   @param callback a callback function to invoke when the request is completed
 345   @param ptr an argument to pass to the callback function
 346   @return an evdns_request object if successful, or NULL if an error occurred.
 347   @see evdns_resolve_ipv4(), evdns_resolve_reverse(), evdns_resolve_reverse_ipv6(), evdns_cancel_request()
 348  */
 349 struct evdns_request *evdns_base_resolve_ipv6(struct evdns_base *base, const char *name, int flags, evdns_callback_type callback, void *ptr);
 350
 351 struct in_addr;
 352 struct in6_addr;
 353
 354 /**
 355   Lookup a PTR record for a given IP address.
 356
 357   @param base the evdns_base to which to apply this operation
 358   @param in an IPv4 address
 359   @param flags either 0, or DNS_QUERY_NO_SEARCH to disable searching for this query.
 360   @param callback a callback function to invoke when the request is completed
 361   @param ptr an argument to pass to the callback function
 362   @return an evdns_request object if successful, or NULL if an error occurred.
 363   @see evdns_resolve_reverse_ipv6(), evdns_cancel_request()
 364  */
 365 struct evdns_request *evdns_base_resolve_reverse(struct evdns_base *base, const struct in_addr *in, int flags, evdns_callback_type callback, void *ptr);
 366
 367
 368 /**
 369   Lookup a PTR record for a given IPv6 address.
 370
 371   @param base the evdns_base to which to apply this operation
 372   @param in an IPv6 address
 373   @param flags either 0, or DNS_QUERY_NO_SEARCH to disable searching for this query.
 374   @param callback a callback function to invoke when the request is completed
 375   @param ptr an argument to pass to the callback function
 376   @return an evdns_request object if successful, or NULL if an error occurred.
 377   @see evdns_resolve_reverse_ipv6(), evdns_cancel_request()
 378  */
 379 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);
 380
 381 /**
 382   Cancels a pending DNS resolution request.
 383
 384   @param base the evdns_base that was used to make the request
 385   @param req the evdns_request that was returned by calling a resolve function
 386   @see evdns_base_resolve_ipv4(), evdns_base_resolve_ipv6, evdns_base_resolve_reverse
 387 */
 388 void evdns_cancel_request(struct evdns_base *base, struct evdns_request *req);
 389
 390 /**
 391   Set the value of a configuration option.
 392
 393   The currently available configuration options are:
 394
 395     ndots, timeout, max-timeouts, max-inflight, attempts, randomize-case,
 396     bind-to, initial-probe-timeout, getaddrinfo-allow-skew.
 397
 398   In versions before Libevent 2.0.3-alpha, the option name needed to end with
 399   a colon.
 400
 401   @param base the evdns_base to which to apply this operation
 402   @param option the name of the configuration option to be modified
 403   @param val the value to be set
 404   @return 0 if successful, or -1 if an error occurred
 405  */
 406 int evdns_base_set_option(struct evdns_base *base, const char *option, const char *val);
 407
 408
 409 /**
 410   Parse a resolv.conf file.
 411
 412   The 'flags' parameter determines what information is parsed from the
 413   resolv.conf file. See the man page for resolv.conf for the format of this
 414   file.
 415
 416   The following directives are not parsed from the file: sortlist, rotate,
 417   no-check-names, inet6, debug.
 418
 419   If this function encounters an error, the possible return values are: 1 =
 420   failed to open file, 2 = failed to stat file, 3 = file too large, 4 = out of
 421   memory, 5 = short read from file, 6 = no nameservers listed in the file
 422
 423   @param base the evdns_base to which to apply this operation
 424   @param flags any of DNS_OPTION_NAMESERVERS|DNS_OPTION_SEARCH|DNS_OPTION_MISC|
 425     DNS_OPTION_HOSTSFILE|DNS_OPTIONS_ALL
 426   @param filename the path to the resolv.conf file
 427   @return 0 if successful, or various positive error codes if an error
 428     occurred (see above)
 429   @see resolv.conf(3), evdns_config_windows_nameservers()
 430  */
 431 int evdns_base_resolv_conf_parse(struct evdns_base *base, int flags, const char *const filename);
 432
 433 /**
 434    Load an /etc/hosts-style file from 'hosts_fname' into 'base'.
 435
 436    If hosts_fname is NULL, add minimal entries for localhost, and nothing
 437    else.
 438
 439    Note that only evdns_getaddrinfo uses the /etc/hosts entries.
 440
 441    Return 0 on success, negative on failure.
 442 */
 443 int evdns_base_load_hosts(struct evdns_base *base, const char *hosts_fname);
 444
 445 /**
 446   Obtain nameserver information using the Windows API.
 447
 448   Attempt to configure a set of nameservers based on platform settings on
 449   a win32 host.  Preferentially tries to use GetNetworkParams; if that fails,
 450   looks in the registry.
 451
 452   @return 0 if successful, or -1 if an error occurred
 453   @see evdns_resolv_conf_parse()
 454  */
 455 #ifdef WIN32
 456 int evdns_base_config_windows_nameservers(struct evdns_base *);
 457 #define EVDNS_BASE_CONFIG_WINDOWS_NAMESERVERS_IMPLEMENTED
 458 #endif
 459
 460
 461 /**
 462   Clear the list of search domains.
 463  */
 464 void evdns_base_search_clear(struct evdns_base *base);
 465
 466
 467 /**
 468   Add a domain to the list of search domains
 469
 470   @param domain the domain to be added to the search list
 471  */
 472 void evdns_base_search_add(struct evdns_base *base, const char *domain);
 473
 474
 475 /**
 476   Set the 'ndots' parameter for searches.
 477
 478   Sets the number of dots which, when found in a name, causes
 479   the first query to be without any search domain.
 480
 481   @param ndots the new ndots parameter
 482  */
 483 void evdns_base_search_ndots_set(struct evdns_base *base, const int ndots);
 484
 485 /**
 486   A callback that is invoked when a log message is generated
 487
 488   @param is_warning indicates if the log message is a 'warning'
 489   @param msg the content of the log message
 490  */
 491 typedef void (*evdns_debug_log_fn_type)(int is_warning, const char *msg);
 492
 493
 494 /**
 495   Set the callback function to handle DNS log messages.  If this
 496   callback is not set, evdns log messages are handled with the regular
 497   Libevent logging system.
 498
 499   @param fn the callback to be invoked when a log message is generated
 500  */
 501 void evdns_set_log_fn(evdns_debug_log_fn_type fn);
 502
 503 /**
 504    Set a callback that will be invoked to generate transaction IDs.  By
 505    default, we pick transaction IDs based on the current clock time, which
 506    is bad for security.
 507
 508    @param fn the new callback, or NULL to use the default.
 509
 510    NOTE: This function has no effect in Libevent 2.0.4-alpha and later,
 511    since Libevent now provides its own secure RNG.
 512  */
 513 void evdns_set_transaction_id_fn(ev_uint16_t (*fn)(void));
 514
 515 /**
 516    Set a callback used to generate random bytes.  By default, we use
 517    the same function as passed to evdns_set_transaction_id_fn to generate
 518    bytes two at a time.  If a function is provided here, it's also used
 519    to generate transaction IDs.
 520
 521    NOTE: This function has no effect in Libevent 2.0.4-alpha and later,
 522    since Libevent now provides its own secure RNG.
 523 */
 524 void evdns_set_random_bytes_fn(void (*fn)(char *, size_t));
 525
 526 /*
 527  * Functions used to implement a DNS server.
 528  */
 529
 530 struct evdns_server_request;
 531 struct evdns_server_question;
 532
 533 /**
 534    A callback to implement a DNS server.  The callback function receives a DNS
 535    request.  It should then optionally add a number of answers to the reply
 536    using the evdns_server_request_add_*_reply functions, before calling either
 537    evdns_server_request_respond to send the reply back, or
 538    evdns_server_request_drop to decline to answer the request.
 539
 540    @param req A newly received request
 541    @param user_data A pointer that was passed to
 542       evdns_add_server_port_with_base().
 543  */
 544 typedef void (*evdns_request_callback_fn_type)(struct evdns_server_request *, void *);
 545 #define EVDNS_ANSWER_SECTION 0
 546 #define EVDNS_AUTHORITY_SECTION 1
 547 #define EVDNS_ADDITIONAL_SECTION 2
 548
 549 #define EVDNS_TYPE_A       1
 550 #define EVDNS_TYPE_NS      2
 551 #define EVDNS_TYPE_CNAME   5
 552 #define EVDNS_TYPE_SOA     6
 553 #define EVDNS_TYPE_PTR    12
 554 #define EVDNS_TYPE_MX     15
 555 #define EVDNS_TYPE_TXT    16
 556 #define EVDNS_TYPE_AAAA   28
 557
 558 #define EVDNS_QTYPE_AXFR 252
 559 #define EVDNS_QTYPE_ALL  255
 560
 561 #define EVDNS_CLASS_INET   1
 562
 563 /* flags that can be set in answers; as part of the err parameter */
 564 #define EVDNS_FLAGS_AA  0x400
 565 #define EVDNS_FLAGS_RD  0x080
 566
 567 /** Create a new DNS server port.
 568
 569     @param base The event base to handle events for the server port.
 570     @param socket A UDP socket to accept DNS requests.
 571     @param flags Always 0 for now.
 572     @param callback A function to invoke whenever we get a DNS request
 573       on the socket.
 574     @param user_data Data to pass to the callback.
 575     @return an evdns_server_port structure for this server port.
 576  */
 577 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);
 578 /** Close down a DNS server port, and free associated structures. */
 579 void evdns_close_server_port(struct evdns_server_port *port);
 580
 581 /** Sets some flags in a reply we're building.
 582     Allows setting of the AA or RD flags
 583  */
 584 void evdns_server_request_set_flags(struct evdns_server_request *req, int flags);
 585
 586 /* Functions to add an answer to an in-progress DNS reply.
 587  */
 588 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);
 589 int evdns_server_request_add_a_reply(struct evdns_server_request *req, const char *name, int n, const void *addrs, int ttl);
 590 int evdns_server_request_add_aaaa_reply(struct evdns_server_request *req, const char *name, int n, const void *addrs, int ttl);
 591 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);
 592 int evdns_server_request_add_cname_reply(struct evdns_server_request *req, const char *name, const char *cname, int ttl);
 593
 594 /**
 595    Send back a response to a DNS request, and free the request structure.
 596 */
 597 int evdns_server_request_respond(struct evdns_server_request *req, int err);
 598 /**
 599    Free a DNS request without sending back a reply.
 600 */
 601 int evdns_server_request_drop(struct evdns_server_request *req);
 602 struct sockaddr;
 603 /**
 604     Get the address that made a DNS request.
 605  */
 606 int evdns_server_request_get_requesting_addr(struct evdns_server_request *_req, struct sockaddr *sa, int addr_len);
 607
 608 /** Callback for evdns_getaddrinfo. */
 609 typedef void (*evdns_getaddrinfo_cb)(int result, struct evutil_addrinfo *res, void *arg);
 610
 611 struct evdns_base;
 612 struct evdns_getaddrinfo_request;
 613 /** Make a non-blocking getaddrinfo request using the dns_base in 'dns_base'.
 614  *
 615  * If we can answer the request immediately (with an error or not!), then we
 616  * invoke cb immediately and return NULL.  Otherwise we return
 617  * an evdns_getaddrinfo_request and invoke cb later.
 618  *
 619  * When the callback is invoked, we pass as its first argument the error code
 620  * that getaddrinfo would return (or 0 for no error).  As its second argument,
 621  * we pass the evutil_addrinfo structures we found (or NULL on error).  We
 622  * pass 'arg' as the third argument.
 623  *
 624  * Limitations:
 625  *
 626  * - The AI_V4MAPPED and AI_ALL flags are not currently implemented.
 627  * - For ai_socktype, we only handle SOCKTYPE_STREAM, SOCKTYPE_UDP, and 0.
 628  * - For ai_protocol, we only handle IPPROTO_TCP, IPPROTO_UDP, and 0.
 629  */
 630 struct evdns_getaddrinfo_request *evdns_getaddrinfo(
 631     struct evdns_base *dns_base,
 632     const char *nodename, const char *servname,
 633     const struct evutil_addrinfo *hints_in,
 634     evdns_getaddrinfo_cb cb, void *arg);
 635
 636 /* Cancel an in-progress evdns_getaddrinfo.  This MUST NOT be called after the
 637  * getaddrinfo's callback has been invoked.  The resolves will be canceled,
 638  * and the callback will be invoked with the error EVUTIL_EAI_CANCEL. */
 639 void evdns_getaddrinfo_cancel(struct evdns_getaddrinfo_request *req);
 640
 641 #ifdef __cplusplus
 642 }
 643 #endif
 644
 645 #endif  /* !_EVENT2_DNS_H_ */