NNet::TResolver Class Reference

Async DNS resolver over UDP. More...

#include <resolver.hpp>

Public Member Functions
template<typename TPoller >
	TResolver (TPoller &poller, EDNSType defaultType=EDNSType::A)
	Constructs a TResolver using the default resolv configuration.
template<typename TPoller >
	TResolver (const TResolvConf &conf, TPoller &poller, EDNSType defaultType=EDNSType::A)
	Constructs a TResolver with a specified DNS configuration.
template<typename TPoller >
	TResolver (TAddress dnsAddr, TPoller &poller, EDNSType defaultType=EDNSType::A)
	Constructs a TResolver using a specific DNS address.
TFuture< std::vector< TAddress > >	Resolve (const std::string &hostname, EDNSType type=EDNSType::DEFAULT)
	Resolves a hostname to a list of IP addresses.

Detailed Description

Async DNS resolver over UDP.

Sends DNS queries to a nameserver (from /etc/resolv.conf by default) and caches results. Multiple concurrent Resolve() calls for the same hostname share a single in-flight query — only one UDP packet is sent.

Owns three background coroutines (sender, receiver, timeouts) that run for the lifetime of the resolver. Construct once and reuse from multiple coroutines concurrently.

TLoop<TDefaultPoller> loop;
TResolver resolver(loop.Poller());
 
TFuture<void> lookup = [&]() -> TFuture<void> {
    auto addrs = co_await resolver.Resolve("example.com");         // A record
    auto v6    = co_await resolver.Resolve("example.com", EDNSType::AAAA);
    TAddress addr = co_await THostPort("example.com", 80).Resolve(resolver);
}();
while (!lookup.done()) loop.Step();

Constructor & Destructor Documentation

TResolver() [1/3]

template<typename TPoller >

NNet::TResolver::TResolver	(	TPoller &	poller,
		EDNSType	defaultType = EDNSType::A
	)

Constructs a TResolver using the default resolv configuration.

The resolver uses DNS nameservers from the default configuration file or as determined by the system.

Parameters

poller	Reference to a poller used for asynchronous operations.
defaultType	The default DNS record type to use if none is specified in a request.

TResolver() [2/3]

template<typename TPoller >

NNet::TResolver::TResolver	(	const TResolvConf &	conf,
		TPoller &	poller,
		EDNSType	defaultType = EDNSType::A
	)

Constructs a TResolver with a specified DNS configuration.

This constructor initializes the resolver with nameservers from a given TResolvConf object.

Parameters

conf	A TResolvConf object containing DNS configuration.
poller	Reference to a poller for asynchronous operations.
defaultType	The default DNS record type to use for resolution.

TResolver() [3/3]

template<typename TPoller >

NNet::TResolver::TResolver	(	TAddress	dnsAddr,
		TPoller &	poller,
		EDNSType	defaultType = EDNSType::A
	)

Constructs a TResolver using a specific DNS address.

This variant allows specifying a single DNS nameserver for resolution.

Parameters

dnsAddr	The address of the DNS server.
poller	Reference to a poller used for asynchronous operations.
defaultType	The default DNS record type for resolution.

Member Function Documentation

Resolve()

TFuture< std::vector< TAddress > > NNet::TResolver::Resolve	(	const std::string &	hostname,
		EDNSType	type = EDNSType::DEFAULT
	)

Resolves a hostname to a list of IP addresses.

If a cached result exists it is returned immediately without a network round-trip. If another coroutine is already resolving the same {hostname, type} pair, this call joins that in-flight query. The result vector is empty if the DNS server returned NXDOMAIN or no records.

Parameters

hostname	Hostname to resolve (e.g. "example.com").
type	Record type; EDNSType::DEFAULT uses the type passed to the constructor (typically EDNSType::A).

Returns

Awaitable resolving to a std::vector<TAddress>.

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The documentation for this class was generated from the following files:

• coroio/dns/resolver.hpp
• coroio/dns/resolver.cpp