adjust flush condition sequence,fastack first to prevent needless fire

Author: xtaci

kcp.go

@@ -788,30 +788,30 @@ func (kcp *KCP) flush(ackOnly bool) uint32 {
 			needsend = true
 			segment.rto = kcp.rx_rto
 			segment.resendts = current + segment.rto
-		} else if _itimediff(current, segment.resendts) >= 0 { // RTO
-			needsend = true
-			if kcp.nodelay == 0 {
-				segment.rto += kcp.rx_rto
-			} else {
-				segment.rto += kcp.rx_rto / 2
-			}
-			segment.resendts = current + segment.rto
-			lost++
-			lostSegs++
-		} else if segment.fastack >= resent && _itimediff(current, segment.ts) >= int32(kcp.rx_rto) { // fast retransmit
+		} else if segment.fastack >= resent { // fast retransmit
 			needsend = true
 			segment.fastack = 0
 			segment.rto = kcp.rx_rto
 			segment.resendts = current + segment.rto
 			change++
 			fastRetransSegs++
-		} else if segment.fastack > 0 && _itimediff(current, segment.ts) >= int32(kcp.rx_rto) && newSegsCount == 0 { // early retransmit
+		} else if segment.fastack > 0 && newSegsCount == 0 { // early retransmit
 			needsend = true
 			segment.fastack = 0
 			segment.rto = kcp.rx_rto
 			segment.resendts = current + segment.rto
 			change++
 			earlyRetransSegs++
+		} else if _itimediff(current, segment.resendts) >= 0 { // RTO
+			needsend = true
+			if kcp.nodelay == 0 {
+				segment.rto += kcp.rx_rto
+			} else {
+				segment.rto += kcp.rx_rto / 2
+			}
+			segment.resendts = current + segment.rto
+			lost++
+			lostSegs++
 		}
 
 		if needsend {