resolver

type ExchangeConfig interface {
	Net() string
	UDPSize() uint16
	// contains filtered or unexported methods
}

type Resolver interface {

	// LookupNS is similar to net.Resolver.LookupNS.
	//
	// LookupNS derives a WithDeadline context from the supplied context so there is
	// no need for the caller to worry about timeouts.
	LookupNS(context.Context, string) ([]string, error)

	// LookipIPAddr is similar to net.Resolver.LookupAddr.
	//
	// LookupIPAddr derives a WithDeadline context from the supplied context so there
	// is no need for the caller to worry about timeouts.
	LookupIPAddr(context.Context, string) ([]net.IP, error)

	// SingleExchange is a shim for the github.com/miekg/dns ExchangeContext function
	// which makes a single exchange attempt with the server; no retries, no fallback
	// to TCP. See FullExchange() for that capability.
	//
	// ExchangeConfig defines parameters which were originally passed thru to miekg
	// via the the miekg.Client struct but we want to reduce complexity where possible
	// to simplify alternative implementations of Resolver.
	//
	// SingleExchange sets the dns.Client.Timeout to singleExchangeTimeout so the
	// caller doesn't have to worry about timeouts via context, or whatever.
	//
	// The dns.Msg must be fully formed with all flags and Id set as needed by the
	// caller.
	//
	// logName is normally the domainName of server and is only used for logging
	// purposes to help identify the server (which is normally an ip address in the
	// autoreverse context).
	SingleExchange(ctx context.Context, c ExchangeConfig, q *dns.Msg,
		server, logName string) (r *dns.Msg, rtt time.Duration, err error)

	// FullExchange is a wrapper around SingleExchange which handles timeouts and
	// truncation. It also creates a fully-formed dns.Msg for SingleExchange.
	//
	// FullExchange derives a WithDeadline context from the supplied context to manage
	// timeouts so the caller doesn't have to do that themselves. This timeout applies
	// across the whole of FullExchange processing including retries and truncation
	// processing. The SingleExchange timeouts still apply across calls to it thus
	// there are in effect two timeouts active for exchanges initiated via
	// FullExchange.
	FullExchange(ctx context.Context, c ExchangeConfig, q dns.Question,
		server, logName string) (r *dns.Msg, rtt time.Duration, err error)
}