plugin/erratic: add axfr support (#1977)

* plugin/erratic: add axfr support

Add support for axfr. This to fix and test long standing axfr issues
that are hard to test if we don't support it directly in coredns.

The most intriguing feature is withholding the last SOA from a response
so the client needs to wait; drop (no reply) and delay is also
supported. All TTLs are set to zero.

Add simple tests that checks if first record is a SOA.

Signed-off-by: Miek Gieben <miek@miek.nl>

* more test coverage

Signed-off-by: Miek Gieben <miek@miek.nl>

1 files changed, 24 insertions, 3 deletions

diff --git a/plugin/erratic/erratic_test.go b/plugin/erratic/erratic_test.go
index 8a3b4e011..406fd8774 100644
--- a/plugin/erratic/erratic_test.go
+++ b/plugin/erratic/erratic_test.go
@@ -14,19 +14,22 @@ func TestErraticDrop(t *testing.T) {
 	e := &Erratic{drop: 2} // 50% drops
 
 	tests := []struct {
+		rrtype       uint16
 		expectedCode int
 		expectedErr  error
 		drop         bool
 	}{
-		{expectedCode: dns.RcodeSuccess, expectedErr: nil, drop: true},
-		{expectedCode: dns.RcodeSuccess, expectedErr: nil, drop: false},
+		{rrtype: dns.TypeA, expectedCode: dns.RcodeSuccess, expectedErr: nil, drop: true},
+		{rrtype: dns.TypeA, expectedCode: dns.RcodeSuccess, expectedErr: nil, drop: false},
+		{rrtype: dns.TypeAAAA, expectedCode: dns.RcodeSuccess, expectedErr: nil, drop: true},
+		{rrtype: dns.TypeHINFO, expectedCode: dns.RcodeServerFailure, expectedErr: nil, drop: false},
 	}
 
 	ctx := context.TODO()
 
 	for i, tc := range tests {
 		req := new(dns.Msg)
-		req.SetQuestion("example.org.", dns.TypeA)
+		req.SetQuestion("example.org.", tc.rrtype)
 
 		rec := dnstest.NewRecorder(&test.ResponseWriter{})
 		code, err := e.ServeDNS(ctx, rec, req)
@@ -77,3 +80,21 @@ func TestErraticTruncate(t *testing.T) {
 		}
 	}
 }
+
+func TestAxfr(t *testing.T) {
+	e := &Erratic{truncate: 0} // nothing, just check if we can get an axfr
+
+	ctx := context.TODO()
+
+	req := new(dns.Msg)
+	req.SetQuestion("example.org.", dns.TypeAXFR)
+
+	rec := dnstest.NewRecorder(&test.ResponseWriter{})
+	_, err := e.ServeDNS(ctx, rec, req)
+	if err != nil {
+		t.Errorf("Failed to set up AXFR: %s", err)
+	}
+	if x := rec.Msg.Answer[0].Header().Rrtype; x != dns.TypeSOA {
+		t.Errorf("Expected for record to be %d, got %d", dns.TypeSOA, x)
+	}
+}