Commit 158ad2d7 authored by Chris O'Haver's avatar Chris O'Haver Committed by GitHub

plugin/file/auto: Write CNAME answer to client even if target lookup is SERVFAIL (#4863)

* write cname answer to client even if target lookup is servfail
Signed-off-by: default avatarChris O'Haver <cohaver@infoblox.com>

* fix existing unit test expectations
Signed-off-by: default avatarChris O'Haver <cohaver@infoblox.com>
parent 8f7162c4
...@@ -82,7 +82,14 @@ func (a Auto) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (i ...@@ -82,7 +82,14 @@ func (a Auto) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (i
case file.Delegation: case file.Delegation:
m.Authoritative = false m.Authoritative = false
case file.ServerFailure: case file.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) w.WriteMsg(m)
......
...@@ -99,7 +99,14 @@ func (f File) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (i ...@@ -99,7 +99,14 @@ func (f File) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (i
case Delegation: case Delegation:
m.Authoritative = false m.Authoritative = false
case ServerFailure: 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) w.WriteMsg(m)
......
...@@ -383,7 +383,7 @@ Redo: ...@@ -383,7 +383,7 @@ Redo:
func (z *Zone) doLookup(ctx context.Context, state request.Request, target string, qtype uint16) ([]dns.RR, Result) { func (z *Zone) doLookup(ctx context.Context, state request.Request, target string, qtype uint16) ([]dns.RR, Result) {
m, e := z.Upstream.Lookup(ctx, state, target, qtype) m, e := z.Upstream.Lookup(ctx, state, target, qtype)
if e != nil { if e != nil {
return nil, Success return nil, ServerFailure
} }
if m == nil { if m == nil {
return nil, Success return nil, Success
......
...@@ -117,6 +117,14 @@ var dnsTestCases = []test.Case{ ...@@ -117,6 +117,14 @@ var dnsTestCases = []test.Case{
}, },
Ns: miekAuth, Ns: miekAuth,
}, },
{
Qname: "ext-cname.miek.nl.", Qtype: dns.TypeA,
Answer: []dns.RR{
test.CNAME("ext-cname.miek.nl. 1800 IN CNAME example.com."),
},
Rcode: dns.RcodeServerFailure,
Ns: miekAuth,
},
} }
const ( const (
...@@ -218,4 +226,6 @@ archive IN CNAME a ...@@ -218,4 +226,6 @@ archive IN CNAME a
dname IN DNAME x dname IN DNAME x
srv IN SRV 10 10 8080 a.miek.nl. srv IN SRV 10 10 8080 a.miek.nl.
mx IN MX 10 a.miek.nl.` mx IN MX 10 a.miek.nl.
ext-cname IN CNAME example.com.`
...@@ -77,10 +77,17 @@ func TestFileUpstreamError(t *testing.T) { ...@@ -77,10 +77,17 @@ func TestFileUpstreamError(t *testing.T) {
}, },
"srvfail": { "srvfail": {
Qname: "srvfail.example.org.", Qtype: dns.TypeA, Qname: "srvfail.example.org.", Qtype: dns.TypeA,
Answer: []dns.RR{
test.CNAME("srvfail.example.org. 3600 IN CNAME srvfail.example.net."),
},
Rcode: dns.RcodeServerFailure, Rcode: dns.RcodeServerFailure,
}, },
"srvfail-chain": { "srvfail-chain": {
Qname: "chain2.example.org.", Qtype: dns.TypeA, Qname: "chain2.example.org.", Qtype: dns.TypeA,
Answer: []dns.RR{
test.CNAME("chain2.example.org. 3600 IN CNAME srvfail.example.org."),
test.CNAME("srvfail.example.org. 3600 IN CNAME srvfail.example.net."),
},
Rcode: dns.RcodeServerFailure, Rcode: dns.RcodeServerFailure,
}, },
"nodata": { "nodata": {
......
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