mirror of
https://github.com/matrix-construct/construct
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110 lines
4.7 KiB
C++
110 lines
4.7 KiB
C++
// Matrix Construct
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//
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// Copyright (C) Matrix Construct Developers, Authors & Contributors
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// Copyright (C) 2016-2018 Jason Volk <jason@zemos.net>
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//
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// Permission to use, copy, modify, and/or distribute this software for any
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// purpose with or without fee is hereby granted, provided that the above
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// copyright notice and this permission notice is present in all copies. The
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// full license for this software is available in the LICENSE file.
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#pragma once
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#define HAVE_IRCD_NET_DNS_H
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/// DNS resolution suite.
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///
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/// Note that in returned rfc1035::records that TTL values are modified from their
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/// original value to an absolute epoch time in seconds which we use for caching.
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/// This modification only occurs if the dns query allows result caching (default).
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///
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namespace ircd::net::dns
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{
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struct opts extern const opts_default;
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using records = vector_view<const rfc1035::record *>;
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using callback = std::function<void (std::exception_ptr, const hostport &, const records &)>;
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using callback_A_one = std::function<void (std::exception_ptr, const hostport &, const rfc1035::record::A &)>;
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using callback_SRV_one = std::function<void (std::exception_ptr, const hostport &, const rfc1035::record::SRV &)>;
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using callback_ipport_one = std::function<void (std::exception_ptr, const hostport &, const ipport &)>;
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// Cache warming drop-in callbacks.
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extern const callback_A_one prefetch_A;
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extern const callback_SRV_one prefetch_SRV;
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extern const callback_ipport_one prefetch_ipport;
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// Callback-based interface
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void resolve(const hostport &, const opts &, callback);
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void resolve(const hostport &, const opts &, callback_A_one);
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void resolve(const hostport &, const opts &, callback_SRV_one);
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void resolve(const hostport &, const opts &, callback_ipport_one);
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// Callback-based interface (default options)
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template<class Callback> void resolve(const hostport &, Callback&&);
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// (internal) generate strings for rfc1035 questions or dns::cache keys.
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string_view make_SRV_key(const mutable_buffer &out, const hostport &, const opts &);
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string_view unmake_SRV_key(const string_view &);
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};
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/// DNS resolution options
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struct ircd::net::dns::opts
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{
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/// Specifies the rfc1035 query type. If this is non-zero a query of this
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/// type will be made or an exception will be thrown if it is not possible
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/// to make the query with this type. A zero value means automatic and the
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/// type will deduced and set internally. To translate a string type like
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/// "SRV" to the type integer for this value see ircd/rfc1035.h.
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uint16_t qtype {0};
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/// Overrides the SRV query to make for this resolution. If empty an
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/// SRV query may still be made from other deductions. This string is
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/// copied at the start of the resolution. It must be a fully qualified
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/// SRV query string: Example: "_matrix._tcp."
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string_view srv;
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/// Specifies the SRV protocol part when deducing the SRV query to be
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/// made. This is used when the net::hostport.service string is just
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/// the name of the service like "matrix" so we then use this value
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/// to build the protocol part of the SRV query string. It is ignored
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/// if `srv` is set or if no service is specified (thus no SRV query is
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/// made in the first place).
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string_view proto{"tcp"};
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/// Whether the dns::cache is checked and may respond to the query.
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bool cache_check {true};
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/// Whether the result of this lookup from the nameserver should be
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/// added to the cache. If true, the TTL value in result records will be
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/// modified to an absolute expiration time. If false, no modification
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/// occurs from the original value.
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bool cache_result {true};
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/// When false, nxdomain errors are not treated as exceptions and the
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/// eptr of a callback will not be set. Instead, the returned record
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/// will contain some nulled / empty data and the user is obliged to
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/// know that this is not a real DNS answer but the error's result.
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/// Note: Requires that cache_result is set to true. If not, this value
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/// is ignored and always considered to be set to true; this is because
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/// the returned record is a reference to the cached error.
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bool nxdomain_exceptions {true};
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};
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/// (internal) DNS cache
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namespace ircd::net::dns::cache
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{
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using closure = std::function<bool (const string_view &, const rfc1035::record &)>;
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bool for_each(const uint16_t &type, const closure &);
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bool for_each(const string_view &type, const closure &);
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bool get(const hostport &, const opts &, const callback &);
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rfc1035::record *put(const rfc1035::question &, const rfc1035::answer &);
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rfc1035::record *put_error(const rfc1035::question &, const uint &code);
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};
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template<class Callback>
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void
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ircd::net::dns::resolve(const hostport &hostport,
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Callback&& callback)
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{
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resolve(hostport, opts_default, std::forward<Callback>(callback));
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}
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