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The health check answered ok while every DNS lookup failed, as on a network that intercepts DNS queries. A lookup whose root servers give no usable reply now fails with ErrNoRootServerAnswered. At the end of each round of DNS checks the watcher records whether every lookup failed with it or with ErrIntercepted; the health check then gives status error, and /.well-known/healthcheck and /health answer 503. Until the first round finishes it stays ok. The health check now depends on the watcher, so fx builds the watcher first: its first round starts before the HTTP server listens, and the server tests' fx graph includes it. NewWithRootServers lets tests start a resolver's walks at real servers that are not root servers. Model: opus-5-5
88 lines
3.0 KiB
Go
88 lines
3.0 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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// ErrNoRootServerAnswered is returned when the root servers were
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// asked and none of them gave a usable reply, as when the host
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// running dnswatcher has lost its network. When they all refused,
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// the error is ErrIntercepted instead.
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ErrNoRootServerAnswered = errors.New("no root server 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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