server: actually scrub response (#2225)

* server: actually scrub response

Did all the worked, hooked it up wrongly :(

This also needs test, but those are hard(er) because we only receive
packets after they have been decoded; i.e. we never see the wirefmt.

Signed-off-by: Miek Gieben <miek@miek.nl>

* Add tests

Add a test for checking is compression pointers are set in the packet.
This also adds an undocumented 'large' feature to the erratic plugin to
send large responses that should be compressed.

Commenting the Scrub out in server results in:

=== RUN   TestCompressScrub
--- FAIL: TestCompressScrub (0.00s)
    compression_scrub_test.go:41: Expected returned packet to be < 512, got 839
FAIL
exit status 1
FAIL    github.com/coredns/coredns/test 0.036s

Actually checking the size might be easier, but lets be thorough here
and check the pointers them selves.

Signed-off-by: Miek Gieben <miek@miek.nl>

* Fix tests

Signed-off-by: Miek Gieben <miek@miek.nl>

* plugin erratic: fix e.large

always put an rr in the reply, fix e.large in erractic and add test to
check for it.

Signed-off-by: Miek Gieben <miek@miek.nl>

plugin/erratic/erratic.go

@@ -19,6 +19,7 @@ type Erratic struct {
 	duration time.Duration
 
 	truncate uint64
+	large    bool // undocumented feature; return large responses for A request (>512B, to test compression).
 
 	q uint64 // counter of queries
 }
@@ -57,6 +58,11 @@ func (e *Erratic) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg
 		rr := *(rrA.(*dns.A))
 		rr.Header().Name = state.QName()
 		m.Answer = append(m.Answer, &rr)
+		if e.large {
+			for i := 0; i < 29; i++ {
+				m.Answer = append(m.Answer, &rr)
+			}
+		}
 	case dns.TypeAAAA:
 		rr := *(rrAAAA.(*dns.AAAA))
 		rr.Header().Name = state.QName()

plugin/erratic/erratic_test.go

@@ -98,3 +98,19 @@ func TestAxfr(t *testing.T) {
 		t.Errorf("Expected for record to be %d, got %d", dns.TypeSOA, x)
 	}
 }
+
+func TestErratic(t *testing.T) {
+	e := &Erratic{drop: 0, delay: 0}
+
+	ctx := context.TODO()
+
+	req := new(dns.Msg)
+	req.SetQuestion("example.org.", dns.TypeA)
+
+	rec := dnstest.NewRecorder(&test.ResponseWriter{})
+	e.ServeDNS(ctx, rec, req)
+
+	if rec.Msg.Answer[0].Header().Rrtype != dns.TypeA {
+		t.Errorf("Expected A response, got %d type", rec.Msg.Answer[0].Header().Rrtype)
+	}
+}

plugin/erratic/setup.go

@@ -104,6 +104,8 @@ func parseErratic(c *caddy.Controller) (*Erratic, error) {
 					return nil, fmt.Errorf("illegal amount value given %q", args[0])
 				}
 				e.truncate = uint64(amount)
+			case "large":
+				e.large = true
 			default:
 				return nil, c.Errf("unknown property '%s'", c.Val())
 			}