middleware/file: Add CNAME chain support (#400)

Up till now we would only chase 1 CNAME. Spec requires we will chase all. This PR add support for this. Up to 8 CNAMEs are chased (this could be longer, by just checking for cycles, but 8 seems enough for now). Also add RRSIG of the first CNAME for DNSSEC.
2025-10-31 10:13:14 -04:00 · 2016-11-09 10:02:26 +00:00
parent 6abbe231e5
commit 4ef53081c5
4 changed files with 157 additions and 16 deletions
--- a/middleware/file/cname_test.go
+++ b/middleware/file/cname_test.go
@@ -0,0 +1,98 @@
+package file
+
+import (
+	"sort"
+	"strings"
+	"testing"
+
+	"github.com/miekg/coredns/middleware/pkg/dnsrecorder"
+	"github.com/miekg/coredns/middleware/test"
+
+	"github.com/miekg/dns"
+	"golang.org/x/net/context"
+)
+
+func TestLookupCNAMEChain(t *testing.T) {
+	name := "example.org."
+	zone, err := Parse(strings.NewReader(dbExampleCNAME), name, "stdin")
+	if err != nil {
+		t.Fatalf("Expected no error when reading zone, got %q", err)
+	}
+
+	fm := File{Next: test.ErrorHandler(), Zones: Zones{Z: map[string]*Zone{name: zone}, Names: []string{name}}}
+	ctx := context.TODO()
+
+	for _, tc := range cnameTestCases {
+		m := tc.Msg()
+
+		rec := dnsrecorder.New(&test.ResponseWriter{})
+		_, err := fm.ServeDNS(ctx, rec, m)
+		if err != nil {
+			t.Errorf("Expected no error, got %v\n", err)
+			return
+		}
+
+		resp := rec.Msg
+		sort.Sort(test.RRSet(resp.Answer))
+		sort.Sort(test.RRSet(resp.Ns))
+		sort.Sort(test.RRSet(resp.Extra))
+
+		if !test.Header(t, tc, resp) {
+			t.Logf("%v\n", resp)
+			continue
+		}
+
+		if !test.Section(t, tc, test.Answer, resp.Answer) {
+			t.Logf("%v\n", resp)
+		}
+		if !test.Section(t, tc, test.Ns, resp.Ns) {
+			t.Logf("%v\n", resp)
+
+		}
+		if !test.Section(t, tc, test.Extra, resp.Extra) {
+			t.Logf("%v\n", resp)
+		}
+	}
+}
+
+var cnameTestCases = []test.Case{
+	{
+		Qname: "a.example.org.", Qtype: dns.TypeA,
+		Answer: []dns.RR{
+			test.A("a.example.org. 1800	IN	A 127.0.0.1"),
+		},
+	},
+	{
+		Qname: "www3.example.org.", Qtype: dns.TypeCNAME,
+		Answer: []dns.RR{
+			test.CNAME("www3.example.org. 1800	IN	CNAME www2.example.org."),
+		},
+	},
+	{
+		Qname: "www3.example.org.", Qtype: dns.TypeA,
+		Answer: []dns.RR{
+			test.A("a.example.org. 1800	IN	A 127.0.0.1"),
+			test.CNAME("www.example.org. 1800	IN	CNAME a.example.org."),
+			test.CNAME("www1.example.org. 1800	IN	CNAME www.example.org."),
+			test.CNAME("www2.example.org. 1800	IN	CNAME www1.example.org."),
+			test.CNAME("www3.example.org. 1800	IN	CNAME www2.example.org."),
+		},
+	},
+}
+
+const dbExampleCNAME = `
+$TTL    30M
+$ORIGIN example.org.
+@       IN      SOA     linode.atoom.net. miek.miek.nl. (
+                             1282630057 ; Serial
+                             4H         ; Refresh
+                             1H         ; Retry
+                             7D         ; Expire
+                             4H )       ; Negative Cache TTL
+
+a               IN      A       127.0.0.1
+www3            IN      CNAME   www2
+www2            IN      CNAME   www1
+www1            IN      CNAME   www
+www             IN      CNAME   a
+dangling        IN      CNAME   foo`