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dnswatcher never asks for recursion and a root server never offers it, so a reply marked recursion available from a root server's address came from a resolver on the network answering in its place. The first such reply, a refusal included, now stops the lookup at once with the existing "this network intercepts DNS queries", naming the address, and no other root server is asked, whether or not that resolver had the name cached. queryDNS now returns a refused reply along with ErrRefused, so the mark on a refusal can be seen. A refusal without the mark is passed over and counted as before. On such a network dnswatcher and its tests fail with that error, by design. A live test passes public resolvers as the root servers and expects it. Model: opus-5-5
82 lines
2.7 KiB
Go
82 lines
2.7 KiB
Go
package resolver
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import "errors"
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// NoAnswerError is returned when the walk to a name's nameservers
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// reached a zone through a referral and none of that zone's
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// nameservers, Nameservers as the referral names them, answered. Err
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// says why they did not.
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type NoAnswerError struct {
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Nameservers []string
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Err error
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}
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func (e *NoAnswerError) Error() string {
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return e.Err.Error()
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}
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func (e *NoAnswerError) Unwrap() error {
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return e.Err
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}
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// Sentinel errors returned by the resolver.
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var (
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// ErrNoNameservers is returned when no authoritative NS
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// could be discovered for a domain.
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ErrNoNameservers = errors.New(
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"no authoritative nameservers found",
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)
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// ErrNXDomain is returned when the servers of the zone a domain
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// is in answer NXDOMAIN: the domain does not exist.
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ErrNXDomain = errors.New("domain does not exist")
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// ErrNoNameserverAnswered is returned when every nameserver
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// asked about a name timed out, failed or returned a referral,
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// so whether the name has addresses is unknown.
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ErrNoNameserverAnswered = errors.New("no nameserver answered")
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// ErrNoNameserverAddress is returned when a nameserver is to be
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// asked and no address for it was given.
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ErrNoNameserverAddress = errors.New("nameserver has no address")
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// ErrUnusableReply is returned when a server replied with an
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// error such as SERVFAIL, or with a referral that leads no
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// closer to the name asked about.
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ErrUnusableReply = errors.New(
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"reply is an error or a referral that leads no closer",
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)
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// ErrTruncated is the reason given for a reply too large for UDP
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// whose retry over TCP failed.
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ErrTruncated = errors.New(
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"reply truncated and its retry over TCP failed",
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)
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// ErrIntercepted is returned when a root server's address gave a
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// reply marked recursion available, a refusal included, which ends
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// the lookup at once, or when every root server refused a query.
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// Root servers do neither, so those replies came from something on
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// the network answering in their place. On such a network
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// dnswatcher fails with it, by design: nothing works around the
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// interception.
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ErrIntercepted = errors.New("this network intercepts DNS queries")
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// ErrCNAMEDepthExceeded is returned when a CNAME chain
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// exceeds MaxCNAMEDepth.
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ErrCNAMEDepthExceeded = errors.New(
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"CNAME chain depth exceeded",
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)
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// ErrLookupDepthExceeded is returned when nameserver addresses
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// were not looked up because lookups were already maxLookupDepth
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// deep, one inside another.
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ErrLookupDepthExceeded = errors.New(
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"lookups of nameserver addresses go too deep",
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)
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// ErrContextCanceled wraps context cancellation for the
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// resolver's iterative queries.
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ErrContextCanceled = errors.New("context canceled")
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)
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