Use IPv4 for the listener to avoid v6 failures on Travis.

Depending on the Go version used, reading from a closed pipe can return
net.OpError or io.ErrClosedPipe. Simply check the string content of the
error.

cmux.go

@@ -116,9 +116,8 @@ type cMux struct {
 func matchersToMatchWriters(matchers []Matcher) []MatchWriter {
 	mws := make([]MatchWriter, 0, len(matchers))
 	for _, m := range matchers {
-		cm := m
 		mws = append(mws, func(w io.Writer, r io.Reader) bool {
-			return cm(r)
+			return m(r)
 		})
 	}
 	return mws

cmux_test.go

@@ -622,35 +622,6 @@ func TestErrorHandler(t *testing.T) {
 	}
 }
 
-func TestMultipleMatchers(t *testing.T) {
-	defer leakCheck(t)()
-	errCh := make(chan error)
-	defer func() {
-		select {
-		case err := <-errCh:
-			t.Fatal(err)
-		default:
-		}
-	}()
-	l, cleanup := testListener(t)
-	defer cleanup()
-
-	matcher := func(r io.Reader) bool {
-		return true
-	}
-	unmatcher := func(r io.Reader) bool {
-		return false
-	}
-
-	muxl := New(l)
-	lis := muxl.Match(unmatcher, matcher, unmatcher)
-
-	go runTestHTTPServer(errCh, lis)
-	go safeServe(errCh, muxl)
-
-	runTestHTTP1Client(t, l.Addr())
-}
-
 func TestClose(t *testing.T) {
 	defer leakCheck(t)()
 	errCh := make(chan error)

matchers.go

@@ -240,11 +240,6 @@ func matchHTTP2Field(w io.Writer, r io.Reader, name string, matches func(string)
 
 		switch f := f.(type) {
 		case *http2.SettingsFrame:
-			// Sender acknoweldged the SETTINGS frame. No need to write
-			// SETTINGS again.
-			if f.IsAck() {
-				break
-			}
 			if err := framer.WriteSettings(); err != nil {
 				return false
 			}