Remove the word middleware (#1067)

* Rename middleware to plugin

first pass; mostly used 'sed', few spots where I manually changed
text.

This still builds a coredns binary.

* fmt error

* Rename AddMiddleware to AddPlugin

* Readd AddMiddleware to remain backwards compat

plugin/pkg/dnsrecorder/recorder.go

@@ -0,0 +1,58 @@
+// Package dnsrecorder allows you to record a DNS response when it is send to the client.
+package dnsrecorder
+
+import (
+	"time"
+
+	"github.com/miekg/dns"
+)
+
+// Recorder is a type of ResponseWriter that captures
+// the rcode code written to it and also the size of the message
+// written in the response. A rcode code does not have
+// to be written, however, in which case 0 must be assumed.
+// It is best to have the constructor initialize this type
+// with that default status code.
+type Recorder struct {
+	dns.ResponseWriter
+	Rcode int
+	Len   int
+	Msg   *dns.Msg
+	Start time.Time
+}
+
+// New makes and returns a new Recorder,
+// which captures the DNS rcode from the ResponseWriter
+// and also the length of the response message written through it.
+func New(w dns.ResponseWriter) *Recorder {
+	return &Recorder{
+		ResponseWriter: w,
+		Rcode:          0,
+		Msg:            nil,
+		Start:          time.Now(),
+	}
+}
+
+// WriteMsg records the status code and calls the
+// underlying ResponseWriter's WriteMsg method.
+func (r *Recorder) WriteMsg(res *dns.Msg) error {
+	r.Rcode = res.Rcode
+	// We may get called multiple times (axfr for instance).
+	// Save the last message, but add the sizes.
+	r.Len += res.Len()
+	r.Msg = res
+	return r.ResponseWriter.WriteMsg(res)
+}
+
+// Write is a wrapper that records the length of the message that gets written.
+func (r *Recorder) Write(buf []byte) (int, error) {
+	n, err := r.ResponseWriter.Write(buf)
+	if err == nil {
+		r.Len += n
+	}
+	return n, err
+}
+
+// Hijack implements dns.Hijacker. It simply wraps the underlying
+// ResponseWriter's Hijack method if there is one, or returns an error.
+func (r *Recorder) Hijack() { r.ResponseWriter.Hijack(); return }

plugin/pkg/dnsrecorder/recorder_test.go

@@ -0,0 +1,28 @@
+package dnsrecorder
+
+/*
+func TestNewResponseRecorder(t *testing.T) {
+	w := httptest.NewRecorder()
+	recordRequest := NewResponseRecorder(w)
+	if !(recordRequest.ResponseWriter == w) {
+		t.Fatalf("Expected Response writer in the Recording to be same as the one sent\n")
+	}
+	if recordRequest.status != http.StatusOK {
+		t.Fatalf("Expected recorded status  to be http.StatusOK (%d) , but found %d\n ", http.StatusOK, recordRequest.status)
+	}
+}
+
+func TestWrite(t *testing.T) {
+	w := httptest.NewRecorder()
+	responseTestString := "test"
+	recordRequest := NewResponseRecorder(w)
+	buf := []byte(responseTestString)
+	recordRequest.Write(buf)
+	if recordRequest.size != len(buf) {
+		t.Fatalf("Expected the bytes written counter to be %d, but instead found %d\n", len(buf), recordRequest.size)
+	}
+	if w.Body.String() != responseTestString {
+		t.Fatalf("Expected Response Body to be %s , but found %s\n", responseTestString, w.Body.String())
+	}
+}
+*/