package resolver

import "errors"

// Sentinel errors returned by the resolver.
var (
	// ErrNoNameservers is returned when no authoritative NS
	// could be discovered for a domain.
	ErrNoNameservers = errors.New(
		"no authoritative nameservers found",
	)

	// ErrNoNameserverAnswered is returned when every nameserver
	// asked about a name timed out, failed or returned a referral,
	// so whether the name has addresses is unknown.
	ErrNoNameserverAnswered = errors.New("no nameserver answered")

	// ErrUnusableReply is returned when a server replied with an
	// error such as SERVFAIL, or with a referral that leads no
	// closer to the name asked about.
	ErrUnusableReply = errors.New(
		"reply is an error or a referral that leads no closer",
	)

	// ErrIntercepted is returned when every root server refused a
	// query. Root servers refuse no query, so the refusals came from
	// something on the network answering in their place.
	ErrIntercepted = errors.New("this network intercepts DNS queries")

	// ErrCNAMEDepthExceeded is returned when a CNAME chain
	// exceeds MaxCNAMEDepth.
	ErrCNAMEDepthExceeded = errors.New(
		"CNAME chain depth exceeded",
	)

	// ErrContextCanceled wraps context cancellation for the
	// resolver's iterative queries.
	ErrContextCanceled = errors.New("context canceled")
)