WIP: autopath as middleware (#859)

autopath as middleware

middleware/autopath/cname.go

@@ -0,0 +1,25 @@
+package autopath
+
+import (
+	"strings"
+
+	"github.com/miekg/dns"
+)
+
+// cnamer will prefix the answer section with a cname that points from original qname to the
+// name of the first RR. It will also update the question section and put original in there.
+func cnamer(m *dns.Msg, original string) {
+	for _, a := range m.Answer {
+		if strings.EqualFold(original, a.Header().Name) {
+			continue
+		}
+		m.Answer = append(m.Answer, nil)
+		copy(m.Answer[1:], m.Answer)
+		m.Answer[0] = &dns.CNAME{
+			Hdr:    dns.RR_Header{Name: original, Rrtype: dns.TypeCNAME, Class: dns.ClassINET, Ttl: a.Header().Ttl},
+			Target: a.Header().Name,
+		}
+		break
+	}
+	m.Question[0].Name = original
+}