Core: convert IP addresses to reverse zone (#838)

* Core: convert IP addresses to reverse zone

If we see IP/mask syntax and the mask mod 8 == 0 we assume a reverse
zone and convert to in-addr or .arpa.

* typos

* integration test

* Addr is not used

* core: clean up normalize

Create a SplitHostPort function that can be used both from normalize.go
and address.go. This removes some (not all!) duplication between the
both and makes it work with reverse address notations.

* More tests

1 files changed, 37 insertions, 0 deletions

diff --git a/test/reverse_test.go b/test/reverse_test.go
index 6342f66b8..2a32ed968 100644
--- a/test/reverse_test.go
+++ b/test/reverse_test.go
@@ -93,3 +93,40 @@ func TestReverseFallthrough(t *testing.T) {
 		t.Errorf("Expected 127.0.0.1, got: %s", resp.Answer[0].(*dns.A).A.String())
 	}
 }
+
+func TestReverseCorefile(t *testing.T) {
+	corefile := `10.0.0.0/24:0 {
+		whoami
+	}`
+
+	i, err := CoreDNSServer(corefile)
+	if err != nil {
+		t.Fatalf("Could not get CoreDNS serving instance: %s", err)
+	}
+	defer i.Stop()
+
+	udp, _ := CoreDNSServerPorts(i, 0)
+	if udp == "" {
+		t.Fatalf("Could not get UDP listening port")
+	}
+
+	log.SetOutput(ioutil.Discard)
+
+	p := proxy.NewLookup([]string{udp})
+	state := request.Request{W: &test.ResponseWriter{}, Req: new(dns.Msg)}
+	resp, err := p.Lookup(state, "17.0.0.10.in-addr.arpa.", dns.TypePTR)
+	if err != nil {
+		t.Fatal("Expected to receive reply, but didn't")
+	}
+
+	if len(resp.Extra) != 2 {
+		t.Fatal("Expected to at least two RRs in the extra section, got none")
+	}
+	// Second one is SRV, first one can be A or AAAA depending on system.
+	if resp.Extra[1].Header().Rrtype != dns.TypeSRV {
+		t.Errorf("Expected RR to SRV, got: %d", resp.Extra[1].Header().Rrtype)
+	}
+	if resp.Extra[1].Header().Name != "_udp.17.0.0.10.in-addr.arpa." {
+		t.Errorf("Expected _udp.17.0.0.10.in-addr.arpa. got: %s", resp.Extra[1].Header().Name)
+	}
+}