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/*
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* Copyright (c) 2006 Niels Provos <provos@citi.umich.edu>
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. The name of the author may not be used to endorse or promote products
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* derived from this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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/*
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* The original DNS code is due to Adam Langley with heavy
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* modifications by Nick Mathewson. Adam put his DNS software in the
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* public domain. You can find his original copyright below. Please,
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* aware that the code as part of libevent is governed by the 3-clause
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* BSD license above.
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*
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* This software is Public Domain. To view a copy of the public domain dedication,
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* visit http://creativecommons.org/licenses/publicdomain/ or send a letter to
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* Creative Commons, 559 Nathan Abbott Way, Stanford, California 94305, USA.
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*
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* I ask and expect, but do not require, that all derivative works contain an
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* attribution similar to:
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* Parts developed by Adam Langley <agl@imperialviolet.org>
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*
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* You may wish to replace the word "Parts" with something else depending on
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* the amount of original code.
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*
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* (Derivative works does not include programs which link against, run or include
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* the source verbatim in their source distributions)
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*/
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/*
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* Welcome, gentle reader
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*
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* Async DNS lookups are really a whole lot harder than they should be,
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* mostly stemming from the fact that the libc resolver has never been
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* very good at them. Before you use this library you should see if libc
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* can do the job for you with the modern async call getaddrinfo_a
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* (see http://www.imperialviolet.org/page25.html#e498). Otherwise,
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* please continue.
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*
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* This code is based on libevent and you must call event_init before
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* any of the APIs in this file. You must also seed the OpenSSL random
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* source if you are using OpenSSL for ids (see below).
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*
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* This library is designed to be included and shipped with your source
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* code. You statically link with it. You should also test for the
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* existence of strtok_r and define HAVE_STRTOK_R if you have it.
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*
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* The DNS protocol requires a good source of id numbers and these
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* numbers should be unpredictable for spoofing reasons. There are
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* three methods for generating them here and you must define exactly
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* one of them. In increasing order of preference:
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*
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* DNS_USE_GETTIMEOFDAY_FOR_ID:
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* Using the bottom 16 bits of the usec result from gettimeofday. This
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* is a pretty poor solution but should work anywhere.
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* DNS_USE_CPU_CLOCK_FOR_ID:
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* Using the bottom 16 bits of the nsec result from the CPU's time
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* counter. This is better, but may not work everywhere. Requires
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* POSIX realtime support and you'll need to link against -lrt on
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* glibc systems at least.
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* DNS_USE_OPENSSL_FOR_ID:
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* Uses the OpenSSL RAND_bytes call to generate the data. You must
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* have seeded the pool before making any calls to this library.
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*
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* The library keeps track of the state of nameservers and will avoid
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* them when they go down. Otherwise it will round robin between them.
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*
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* Quick start guide:
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* #include "evdns.h"
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* void callback(int result, char type, int count, int ttl,
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* void *addresses, void *arg);
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* evdns_resolv_conf_parse(DNS_OPTIONS_ALL, "/etc/resolv.conf");
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* evdns_resolve("www.hostname.com", 0, callback, NULL);
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*
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* When the lookup is complete the callback function is called. The
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* first argument will be one of the DNS_ERR_* defines in evdns.h.
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* Hopefully it will be DNS_ERR_NONE, in which case type will be
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* DNS_IPv4_A, count will be the number of IP addresses, ttl is the time
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* which the data can be cached for (in seconds), addresses will point
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* to an array of uint32_t's and arg will be whatever you passed to
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* evdns_resolve.
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*
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* Searching:
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*
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* In order for this library to be a good replacement for glibc's resolver it
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* supports searching. This involves setting a list of default domains, in
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* which names will be queried for. The number of dots in the query name
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* determines the order in which this list is used.
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*
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* Searching appears to be a single lookup from the point of view of the API,
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* although many DNS queries may be generated from a single call to
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* evdns_resolve. Searching can also drastically slow down the resolution
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* of names.
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*
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* To disable searching:
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* 1. Never set it up. If you never call evdns_resolv_conf_parse or
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* evdns_search_add then no searching will occur.
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*
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* 2. If you do call evdns_resolv_conf_parse then don't pass
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* DNS_OPTION_SEARCH (or DNS_OPTIONS_ALL, which implies it).
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*
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* 3. When calling evdns_resolve, pass the DNS_QUERY_NO_SEARCH flag.
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*
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* The order of searches depends on the number of dots in the name. If the
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* number is greater than the ndots setting then the names is first tried
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* globally. Otherwise each search domain is appended in turn.
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*
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* The ndots setting can either be set from a resolv.conf, or by calling
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* evdns_search_ndots_set.
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*
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* For example, with ndots set to 1 (the default) and a search domain list of
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* ["myhome.net"]:
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* Query: www
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* Order: www.myhome.net, www.
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*
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* Query: www.abc
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* Order: www.abc., www.abc.myhome.net
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*
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* API reference:
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*
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* int evdns_nameserver_add(unsigned long int address)
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* Add a nameserver. The address should be an IP address in
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* network byte order. The type of address is chosen so that
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* it matches in_addr.s_addr.
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* Returns non-zero on error.
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*
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* int evdns_nameserver_ip_add(const char *ip_as_string)
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* This wraps the above function by parsing a string as an IP
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* address and adds it as a nameserver.
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* Returns non-zero on error
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*
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* int evdns_resolve(const char *name, int flags,
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* evdns_callback_type callback,
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* void *ptr)
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* Resolve a name. The name parameter should be a DNS name.
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* The flags parameter should be 0, or DNS_QUERY_NO_SEARCH
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* which disables searching for this query. (see defn of
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* searching above).
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*
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* The callback argument is a function which is called when
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* this query completes and ptr is an argument which is passed
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* to that callback function.
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*
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* Returns non-zero on error
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*
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* void evdns_search_clear()
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* Clears the list of search domains
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*
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* void evdns_search_add(const char *domain)
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* Add a domain to the list of search domains
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*
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* void evdns_search_ndots_set(int ndots)
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* Set the number of dots which, when found in a name, causes
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* the first query to be without any search domain.
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*
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* int evdns_count_nameservers(void)
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* Return the number of configured nameservers (not necessarily the
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* number of running nameservers). This is useful for double-checking
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* whether our calls to the various nameserver configuration functions
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* have been successful.
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*
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* int evdns_clear_nameservers_and_suspend(void)
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* Remove all currently configured nameservers, and suspend all pending
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* resolves. Resolves will not necessarily be re-attempted until
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* evdns_resume() is called.
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*
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* int evdns_resume(void)
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* Re-attempt resolves left in limbo after an earlier call to
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* evdns_clear_nameservers_and_suspend().
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*
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* int evdns_config_windows_nameservers(void)
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* Attempt to configure a set of nameservers based on platform settings on
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* a win32 host. Preferentially tries to use GetNetworkParams; if that fails,
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* looks in the registry. Returns 0 on success, nonzero on failure.
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*
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* int evdns_resolv_conf_parse(int flags, const char *filename)
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* Parse a resolv.conf like file from the given filename.
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*
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* See the man page for resolv.conf for the format of this file.
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* The flags argument determines what information is parsed from
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* this file:
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* DNS_OPTION_SEARCH - domain, search and ndots options
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* DNS_OPTION_NAMESERVERS - nameserver lines
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* DNS_OPTION_MISC - timeout and attempts options
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* DNS_OPTIONS_ALL - all of the above
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* The following directives are not parsed from the file:
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* sortlist, rotate, no-check-names, inet6, debug
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*
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* Returns non-zero on error:
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* 0 no errors
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* 1 failed to open file
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* 2 failed to stat file
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* 3 file too large
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* 4 out of memory
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* 5 short read from file
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* 6 no nameservers in file
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*
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* Internals:
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*
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* Requests are kept in two queues. The first is the inflight queue. In
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* this queue requests have an allocated transaction id and nameserver.
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* They will soon be transmitted if they haven't already been.
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*
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* The second is the waiting queue. The size of the inflight ring is
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* limited and all other requests wait in waiting queue for space. This
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* bounds the number of concurrent requests so that we don't flood the
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* nameserver. Several algorithms require a full walk of the inflight
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* queue and so bounding its size keeps thing going nicely under huge
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* (many thousands of requests) loads.
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*
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* If a nameserver loses too many requests it is considered down and we
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* try not to use it. After a while we send a probe to that nameserver
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* (a lookup for google.com) and, if it replies, we consider it working
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* again. If the nameserver fails a probe we wait longer to try again
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* with the next probe.
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*/
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#ifndef EVENTDNS_H
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#define EVENTDNS_H
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#ifdef __cplusplus
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extern "C" {
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#endif
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/* Error codes 0-5 are as described in RFC 1035. */
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#define DNS_ERR_NONE 0
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/* The name server was unable to interpret the query */
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#define DNS_ERR_FORMAT 1
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/* The name server was unable to process this query due to a problem with the
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* name server */
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#define DNS_ERR_SERVERFAILED 2
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/* The domain name does not exist */
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#define DNS_ERR_NOTEXIST 3
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/* The name server does not support the requested kind of query */
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#define DNS_ERR_NOTIMPL 4
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/* The name server refuses to reform the specified operation for policy
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* reasons */
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#define DNS_ERR_REFUSED 5
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/* The reply was truncated or ill-formated */
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#define DNS_ERR_TRUNCATED 65
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/* An unknown error occurred */
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#define DNS_ERR_UNKNOWN 66
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/* Communication with the server timed out */
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#define DNS_ERR_TIMEOUT 67
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/* The request was canceled because the DNS subsystem was shut down. */
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#define DNS_ERR_SHUTDOWN 68
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#define DNS_IPv4_A 1
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#define DNS_PTR 2
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#define DNS_IPv6_AAAA 3
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#define DNS_QUERY_NO_SEARCH 1
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#define DNS_OPTION_SEARCH 1
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#define DNS_OPTION_NAMESERVERS 2
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#define DNS_OPTION_MISC 4
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#define DNS_OPTIONS_ALL 7
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/*
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* The callback that contains the results from a lookup.
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* - type is either DNS_IPv4_A or DNS_PTR or DNS_IPv6_AAAA
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* - count contains the number of addresses of form type
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* - ttl is the number of seconds the resolution may be cached for.
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* - addresses needs to be cast according to type
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*/
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typedef void (*evdns_callback_type) (int result, char type, int count, int ttl, void *addresses, void *arg);
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int evdns_init(void);
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void evdns_shutdown(int fail_requests);
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const char *evdns_err_to_string(int err);
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int evdns_nameserver_add(unsigned long int address);
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int evdns_count_nameservers(void);
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int evdns_clear_nameservers_and_suspend(void);
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int evdns_resume(void);
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int evdns_nameserver_ip_add(const char *ip_as_string);
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int evdns_resolve_ipv4(const char *name, int flags, evdns_callback_type callback, void *ptr);
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int evdns_resolve_ipv6(const char *name, int flags, evdns_callback_type callback, void *ptr);
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struct in_addr;
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struct in6_addr;
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int evdns_resolve_reverse(struct in_addr *in, int flags, evdns_callback_type callback, void *ptr);
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int evdns_resolve_reverse_ipv6(struct in6_addr *in, int flags, evdns_callback_type callback, void *ptr);
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int evdns_set_option(const char *option, const char *val, int flags);
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int evdns_resolv_conf_parse(int flags, const char *);
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#ifdef MS_WINDOWS
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int evdns_config_windows_nameservers(void);
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#endif
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void evdns_search_clear(void);
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void evdns_search_add(const char *domain);
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void evdns_search_ndots_set(const int ndots);
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typedef void (*evdns_debug_log_fn_type)(int is_warning, const char *msg);
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void evdns_set_log_fn(evdns_debug_log_fn_type fn);
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#define DNS_NO_SEARCH 1
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#ifdef __cplusplus
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}
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#endif
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/*
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* Structures and functions used to implement a DNS server.
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*/
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struct evdns_server_request {
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int flags;
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int nquestions;
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struct evdns_server_question **questions;
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};
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struct evdns_server_question {
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int type;
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int class;
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char name[1];
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};
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typedef void (*evdns_request_callback_fn_type)(struct evdns_server_request *, void *);
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#define EVDNS_ANSWER_SECTION 0
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#define EVDNS_AUTHORITY_SECTION 1
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#define EVDNS_ADDITIONAL_SECTION 2
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#define EVDNS_TYPE_A 1
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#define EVDNS_TYPE_NS 2
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#define EVDNS_TYPE_CNAME 5
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#define EVDNS_TYPE_SOA 6
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#define EVDNS_TYPE_PTR 12
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#define EVDNS_TYPE_MX 15
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#define EVDNS_TYPE_TXT 16
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#define EVDNS_TYPE_AAAA 28
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#define EVDNS_QTYPE_AXFR 252
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#define EVDNS_QTYPE_ALL 255
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#define EVDNS_CLASS_INET 1
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struct evdns_server_port *evdns_add_server_port(int socket, int is_tcp, evdns_request_callback_fn_type callback, void *user_data);
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void evdns_close_server_port(struct evdns_server_port *port);
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int evdns_server_request_add_reply(struct evdns_server_request *req, int section, const char *name, int type, int class, int ttl, int datalen, int is_name, const char *data);
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int evdns_server_request_add_a_reply(struct evdns_server_request *req, const char *name, int n, void *addrs, int ttl);
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int evdns_server_request_add_aaaa_reply(struct evdns_server_request *req, const char *name, int n, void *addrs, int ttl);
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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);
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int evdns_server_request_add_cname_reply(struct evdns_server_request *req, const char *name, const char *cname, int ttl);
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int evdns_server_request_respond(struct evdns_server_request *req, int err);
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int evdns_server_request_drop(struct evdns_server_request *req);
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struct sockaddr;
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int evdns_server_request_get_requesting_addr(struct evdns_server_request *_req, struct sockaddr *sa, int addr_len);
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#endif /* !EVENTDNS_H */
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