restore old logic/constants (#2045)

* fix indices

* Update serversInfo.go

For safety go back to former logic, just generalized for lbStrategy, until someone comes up with an actual improvement.

* restore old logic/constants

Author: livingentity

dnscrypt-proxy/serversInfo.go

@@ -24,7 +24,7 @@ import (
 )
 
 const (
-	RTTEwmaDecay = 15.0
+	RTTEwmaDecay = 10.0
 )
 
 type RegisteredServer struct {
@@ -264,9 +264,9 @@ func (serversInfo *ServersInfo) estimatorUpdate() {
 		serversInfo.inner[candidate], serversInfo.inner[currentActive] = serversInfo.inner[currentActive], serversInfo.inner[candidate]
 		dlog.Debugf("New preferred candidate: %s (RTT: %d vs previous: %d)", serversInfo.inner[currentActive].Name, int(candidateRtt), int(currentActiveRtt))
 		partialSort = true
-	} else if candidateRtt > 0 && candidateRtt > serversInfo.inner[activeCount].rtt.Value() {
+	} else if candidateRtt > 0 && candidateRtt >= (serversInfo.inner[0].rtt.Value()+serversInfo.inner[activeCount-1].rtt.Value())/2.0*4.0 {
 		if time.Since(serversInfo.inner[candidate].lastActionTS) > time.Duration(1*time.Minute) {
-			serversInfo.inner[candidate].rtt.Add(serversInfo.inner[activeCount].rtt.Value())
+			serversInfo.inner[candidate].rtt.Add(candidateRtt/2.0)
 			dlog.Debugf("Giving a new chance to candidate [%s], lowering its RTT from %d to %d (best: %d)", serversInfo.inner[candidate].Name, int(candidateRtt), int(serversInfo.inner[candidate].rtt.Value()), int(serversInfo.inner[0].rtt.Value()))
 			partialSort = true
 		}