client: omit mode from Transport header (#611) (#574) (#614)

client.go

@@ -1288,9 +1288,8 @@ func (c *Client) doSetup(
 				v := headers.TransportModeRecord
 				return &v
 			}
-
-			v := headers.TransportModePlay
-			return &v
+			// when playing, omit mode, since it causes errors with some servers.
+			return nil
 		}(),
 	}
 

client_play_test.go

@@ -344,6 +344,8 @@ func TestClientPlay(t *testing.T) {
 					err2 = inTH.Unmarshal(req.Header["Transport"])
 					require.NoError(t, err2)
 
+					require.Equal(t, (*headers.TransportMode)(nil), inTH.Mode)
+
 					var th headers.Transport
 
 					switch transport {

client_record_test.go

@@ -200,6 +200,8 @@ func TestClientRecordSerial(t *testing.T) {
 				err2 = inTH.Unmarshal(req.Header["Transport"])
 				require.NoError(t, err2)
 
+				require.Equal(t, headers.TransportModeRecord, *inTH.Mode)
+
 				var l1 net.PacketConn
 				var l2 net.PacketConn
 				if transport == "udp" {