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A nameserver's queries went only to the first IPv4 address its name resolves to, so one unreachable address made it fail whenever that address came first in the answer. Each record type is now asked at the addresses one at a time until one gives a usable reply, and the next type is asked first at the address that gave it. A type that fails is logged with the reason at each address, and a nameserver is reported as timed out only when every query timed out; one given no address has failed. The README's DNS Resolution Strategy says which addresses are asked. Model: opus-5-5
78 lines
2.5 KiB
Go
78 lines
2.5 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 every root server refused a
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// query. Root servers refuse no query, so the refusals came from
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// something on the network answering in their place.
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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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