implement writing of ACK frames containing ECN counts

qlog/frame.go

@@ -102,6 +102,11 @@ func marshalAckFrame(enc *gojay.Encoder, f *logging.AckFrame) {
 	enc.StringKey("frame_type", "ack")
 	enc.FloatKeyOmitEmpty("ack_delay", milliseconds(f.DelayTime))
 	enc.ArrayKey("acked_ranges", ackRanges(f.AckRanges))
+	if hasECN := f.ECT0 > 0 || f.ECT1 > 0 || f.ECNCE > 0; hasECN {
+		enc.Uint64Key("ect0", f.ECT0)
+		enc.Uint64Key("ect1", f.ECT1)
+		enc.Uint64Key("ce", f.ECNCE)
+	}
 }
 
 func marshalResetStreamFrame(enc *gojay.Encoder, f *logging.ResetStreamFrame) {

qlog/frame_test.go

@@ -60,6 +60,24 @@ var _ = Describe("Frames", func() {
 		)
 	})
 
+	It("marshals ACK frames with ECN counts", func() {
+		check(
+			&logging.AckFrame{
+				AckRanges: []logging.AckRange{{Smallest: 120, Largest: 120}},
+				ECT0:      10,
+				ECT1:      100,
+				ECNCE:     1000,
+			},
+			map[string]interface{}{
+				"frame_type":   "ack",
+				"acked_ranges": [][]float64{{120}},
+				"ect0":         10,
+				"ect1":         100,
+				"ce":           1000,
+			},
+		)
+	})
+
 	It("marshals ACK frames with a range acknowledging ranges of packets", func() {
 		check(
 			&logging.AckFrame{