WIP: middleware/dnstap (#711)

middleware/dnstap add

middleware/dnstap/handler.go

@@ -0,0 +1,51 @@
+package dnstap
+
+import (
+	"fmt"
+	"golang.org/x/net/context"
+	"io"
+
+	"github.com/coredns/coredns/middleware"
+	"github.com/coredns/coredns/middleware/dnstap/msg"
+	"github.com/coredns/coredns/middleware/dnstap/taprw"
+
+	tap "github.com/dnstap/golang-dnstap"
+	"github.com/miekg/dns"
+)
+
+type Dnstap struct {
+	Next middleware.Handler
+	Out  io.Writer
+	Pack bool
+}
+
+func tapMessageTo(w io.Writer, m *tap.Message) error {
+	frame, err := msg.Marshal(m)
+	if err != nil {
+		return fmt.Errorf("marshal: %s", err)
+	}
+	_, err = w.Write(frame)
+	return err
+}
+
+func (h Dnstap) TapMessage(m *tap.Message) error {
+	return tapMessageTo(h.Out, m)
+}
+
+func (h Dnstap) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (int, error) {
+	rw := taprw.ResponseWriter{ResponseWriter: w, Taper: &h, Query: r, Pack: h.Pack}
+	rw.QueryEpoch()
+
+	code, err := middleware.NextOrFailure(h.Name(), h.Next, ctx, &rw, r)
+	if err != nil {
+		// ignore dnstap errors
+		return code, err
+	}
+
+	if err := rw.DnstapError(); err != nil {
+		return code, middleware.Error("dnstap", err)
+	}
+
+	return code, nil
+}
+func (h Dnstap) Name() string { return "dnstap" }