middleware/file: fix DS handling (#344)

The DS record is handled specially in the server ServeDNS mux, but there
was no code that actually called the correct middleware handler chain
when encountering a DS.

This PR fixes that behavoir, additonal bugs has been files to look into
how we are handling delegation (secure and non-secure ones).

test/ds_file_test.go

@@ -0,0 +1,86 @@
+package test
+
+import (
+	"io/ioutil"
+	"log"
+	"sort"
+	"testing"
+
+	"github.com/miekg/coredns/middleware/proxy"
+	mtest "github.com/miekg/coredns/middleware/test"
+	"github.com/miekg/coredns/request"
+
+	"github.com/miekg/dns"
+)
+
+// Using miek.nl here because this is the easiest zone to get access to and it's masters
+// run both NSD and BIND9, making checks like "what should we actually return" super easy.
+var dsTestCases = []mtest.Case{
+	{
+		Qname: "_udp.miek.nl.", Qtype: dns.TypeDS,
+		Rcode: dns.RcodeNameError,
+		Ns: []dns.RR{
+			mtest.SOA("miek.nl.	1800	IN	SOA	linode.atoom.net. miek.miek.nl. 1282630057 14400 3600 604800 14400"),
+		},
+	},
+	{
+		Qname: "miek.nl.", Qtype: dns.TypeDS,
+		Ns: []dns.RR{
+			mtest.SOA("miek.nl.	1800	IN	SOA	linode.atoom.net. miek.miek.nl. 1282630057 14400 3600 604800 14400"),
+		},
+	},
+}
+
+func TestLookupDS(t *testing.T) {
+	name, rm, err := TempFile(".", miekNL)
+	if err != nil {
+		t.Fatalf("failed to created zone: %s", err)
+	}
+	defer rm()
+
+	corefile := `miek.nl:0 {
+       file ` + name + `
+}
+`
+
+	i, err := CoreDNSServer(corefile)
+	if err != nil {
+		t.Fatalf("Could not get CoreDNS serving instance: %s", err)
+	}
+
+	udp, _ := CoreDNSServerPorts(i, 0)
+	if udp == "" {
+		t.Fatalf("Could not get UDP listening port")
+	}
+	defer i.Stop()
+
+	log.SetOutput(ioutil.Discard)
+
+	p := proxy.New([]string{udp})
+	state := request.Request{W: &mtest.ResponseWriter{}, Req: new(dns.Msg)}
+
+	for _, tc := range dsTestCases {
+		resp, err := p.Lookup(state, tc.Qname, tc.Qtype)
+		if err != nil || resp == nil {
+			t.Fatalf("Expected to receive reply, but didn't for %s %d", tc.Qname, tc.Qtype)
+		}
+
+		sort.Sort(mtest.RRSet(resp.Answer))
+		sort.Sort(mtest.RRSet(resp.Ns))
+		sort.Sort(mtest.RRSet(resp.Extra))
+
+		if !mtest.Header(t, tc, resp) {
+			t.Logf("%v\n", resp)
+			continue
+		}
+		if !mtest.Section(t, tc, mtest.Answer, resp.Answer) {
+			t.Logf("%v\n", resp)
+		}
+		if !mtest.Section(t, tc, mtest.Ns, resp.Ns) {
+			t.Logf("%v\n", resp)
+		}
+		if !mtest.Section(t, tc, mtest.Extra, resp.Extra) {
+			t.Logf("%v\n", resp)
+		}
+	}
+}