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cli: add tailscale dns query (#13368)

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Updates tailscale/tailscale#13326

Adds a CLI subcommand to perform DNS queries using the internal DNS forwarder and observe its internals (namely, which upstream resolvers are being used).

Signed-off-by: Andrea Gottardo <andrea@gottardo.me>
This commit is contained in:
Andrea Gottardo
2024-09-24 13:18:45 -07:00
committed by GitHub
parent a98f75b783
commit 8a6f48b455
13 changed files with 396 additions and 7 deletions
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11
net/dns/resolver/forwarder.go
View File

@ -834,6 +834,17 @@ func (f *forwarder) resolvers(domain dnsname.FQDN) []resolverAndDelay {
return cloudHostFallback // or nil if no fallback
}
// GetUpstreamResolvers returns the resolvers that would be used to resolve
// the given FQDN.
func (f *forwarder) GetUpstreamResolvers(name dnsname.FQDN) []*dnstype.Resolver {
resolvers := f.resolvers(name)
upstreamResolvers := make([]*dnstype.Resolver, 0, len(resolvers))
for _, r := range resolvers {
upstreamResolvers = append(upstreamResolvers, r.name)
}
return upstreamResolvers
}
// forwardQuery is information and state about a forwarded DNS query that's
// being sent to 1 or more upstreams.
//

6
net/dns/resolver/tsdns.go
View File

@ -337,6 +337,12 @@ func (r *Resolver) Query(ctx context.Context, bs []byte, family string, from net
return out, err
}
// GetUpstreamResolvers returns the resolvers that would be used to resolve
// the given FQDN.
func (r *Resolver) GetUpstreamResolvers(name dnsname.FQDN) []*dnstype.Resolver {
return r.forwarder.GetUpstreamResolvers(name)
}
// parseExitNodeQuery parses a DNS request packet.
// It returns nil if it's malformed or lacking a question.
func parseExitNodeQuery(q []byte) *response {