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construct/include/ircd/net/dns.h

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// Matrix Construct
//
// Copyright (C) Matrix Construct Developers, Authors & Contributors
// Copyright (C) 2016-2018 Jason Volk <jason@zemos.net>
//
// Permission to use, copy, modify, and/or distribute this software for any
// purpose with or without fee is hereby granted, provided that the above
// copyright notice and this permission notice is present in all copies. The
// full license for this software is available in the LICENSE file.
#pragma once
#define HAVE_IRCD_NET_DNS_H
/// DNS resolution suite.
///
/// Note that at this time these functions must be called on an ircd::ctx to
/// conduct any queries of the cache.
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///
namespace ircd::net::dns
{
struct init;
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struct opts;
using records = vector_view<const rfc1035::record *>;
using callback = std::function<void (const hostport &, const json::array &)>;
using callback_one = std::function<void (const hostport &, const json::object &)>;
using callback_ipport = std::function<void (std::exception_ptr, const hostport &, const ipport &)>;
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extern const struct opts opts_default;
extern log::log log;
// Utilities
bool is_error(const json::object &rr);
bool is_error(const json::array &rr);
bool is_empty(const json::object &rr);
bool is_empty(const json::array &rr);
time_t get_ttl(const json::object &rr);
bool expired(const json::object &rr, const time_t &rr_ts, const time_t &min_ttl);
bool expired(const json::object &rr, const time_t &rr_ts);
json::object random_choice(const json::array &);
string_view make_SRV_key(const mutable_buffer &out, const hostport &, const opts &);
string_view unmake_SRV_key(const string_view &);
// netdb tools
string_view service_name(std::nothrow_t, const mutable_buffer &out, const uint16_t &port, const string_view &prot = {});
string_view service_name(const mutable_buffer &out, const uint16_t &port, const string_view &prot = {});
uint16_t service_port(std::nothrow_t, const string_view &name, const string_view &prot = {});
uint16_t service_port(const string_view &name, const string_view &prot = {});
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// Callback-based interface
void resolve(const hostport &, const opts &, callback);
void resolve(const hostport &, const opts &, callback_one); // convenience
void resolve(const hostport &, const opts &, callback_ipport); // convenience
}
/// DNS resolution options
struct ircd::net::dns::opts
{
/// Specifies the rfc1035 query type. If this is non-zero a query of this
/// type will be made or an exception will be thrown if it is not possible
/// to make the query with this type. A zero value means automatic and the
/// type will deduced and set internally. To translate a string type like
/// "SRV" to the type integer for this value see ircd/rfc1035.h.
uint16_t qtype {0};
/// Overrides the SRV query to make for this resolution. If empty an
/// SRV query may still be made from other deductions. This string is
/// copied at the start of the resolution. It must be a fully qualified
/// SRV query string: Example: "_matrix._tcp."
string_view srv;
/// Specifies the SRV protocol part when deducing the SRV query to be
/// made. This is used when the net::hostport.service string is just
/// the name of the service like "matrix" so we then use this value
/// to build the protocol part of the SRV query string. It is ignored
/// if `srv` is set or if no service is specified (thus no SRV query is
/// made in the first place).
string_view proto{"tcp"};
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/// Whether the dns::cache is checked and may respond to the query.
bool cache_check {true};
/// Whether the result of this lookup from the nameserver should be
/// added to the cache.
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bool cache_result {true};
/// When false, nxdomain errors are not treated as exceptions and the
/// eptr of a callback will not be set. Instead, the returned record
/// will contain some nulled / empty data and the user is obliged to
/// know that this is not a real DNS answer but the error's result.
/// Note: Requires that cache_result is set to true. If not, this value
/// is ignored and always considered to be set to true; this is because
/// the returned record is a reference to the cached error.
bool nxdomain_exceptions {true};
/// When false, queries to translate service strings to port numbers using
/// netdb (i.e. /etc/services) will be disabled if they were to occur.
bool service_port {true};
opts() = default;
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};
/// (internal)
class [[gnu::visibility("hidden")]]
ircd::net::dns::init
{
static void
service_init(),
service_fini() noexcept;
public:
init();
~init() noexcept;
};