corrected rtt estimation

udp/congestion/newreno.go

@@ -161,7 +161,7 @@ func (c *NewReno) receivedSequence(seq uint32) {
 			time:     time.Now(),
 			sequence: seq,
 		})
-		return // if this seq doesn't change the ack field, awaitingAck will still not do anything useful
+		return // if this seq doesn't change the ack field, updateAck will still not do anything useful
 	}
 
 	sort.Sort(c.awaitingAck)
@@ -261,7 +261,7 @@ func (c *NewReno) receivedAck(ack uint32) {
 		return
 	}
 
-	c.inFlight = c.inFlight[i-1:]
+	c.inFlight = c.inFlight[i:]
 	if c.slowStart {
 		c.windowSize += uint32(i)
 	} else {

udp/congestion/newreno_test.go

@@ -97,14 +97,17 @@ func (n *newRenoTest) RunSideA(ctx context.Context) {
 			}
 
 			seq := n.sideA.AwaitEarlyUpdate(500 * time.Millisecond)
-			if seq == 0 { // discard keepalives
-				p := congestionPacket{
-					seq:  seq,
-					nack: n.sideA.NextNack(),
-					ack:  n.sideA.NextAck(),
-				}
-				n.aOutbound <- p
+			if seq != 0 {
+				// skip keepalive
+				// required to ensure AwaitEarlyUpdate terminates
+				continue
 			}
+			p := congestionPacket{
+				seq:  seq,
+				nack: n.sideA.NextNack(),
+				ack:  n.sideA.NextAck(),
+			}
+			n.aOutbound <- p
 		}
 	}()
 }
@@ -129,14 +132,17 @@ func (n *newRenoTest) RunSideB(ctx context.Context) {
 			}
 
 			seq := n.sideB.AwaitEarlyUpdate(500 * time.Millisecond)
-			if seq == 0 { // discard keepalives
-				p := congestionPacket{
-					seq:  seq,
-					nack: n.sideB.NextNack(),
-					ack:  n.sideB.NextAck(),
-				}
-				n.bOutbound <- p
+			if seq != 0 {
+				// skip keepalive
+				// required to ensure AwaitEarlyUpdate terminates
+				continue
 			}
+			p := congestionPacket{
+				seq:  seq,
+				nack: n.sideB.NextNack(),
+				ack:  n.sideB.NextAck(),
+			}
+			n.bOutbound <- p
 		}
 	}()
 }