diff options
Diffstat (limited to 'plugin/file/file.go')
| -rw-r--r-- | plugin/file/file.go | 9 |
1 files changed, 8 insertions, 1 deletions
diff --git a/plugin/file/file.go b/plugin/file/file.go index 0834ddc4d..f50c3d091 100644 --- a/plugin/file/file.go +++ b/plugin/file/file.go @@ -99,7 +99,14 @@ func (f File) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (i case Delegation: m.Authoritative = false case ServerFailure: - return dns.RcodeServerFailure, nil + // If the result is SERVFAIL and the answer is non-empty, then the SERVFAIL came from an + // external CNAME lookup and the answer contains the CNAME with no target record. We should + // write the CNAME record to the client instead of sending an empty SERVFAIL response. + if len(m.Answer) == 0 { + return dns.RcodeServerFailure, nil + } + // The rcode in the response should be the rcode received from the target lookup. RFC 6604 section 3 + m.Rcode = dns.RcodeServerFailure } w.WriteMsg(m) |