eth: better discovery iterator nesting order

Signed-off-by: Csaba Kiraly <[email protected]>

Author: cskiraly

eth/backend.go

@@ -522,9 +522,9 @@ func (s *Ethereum) setupDiscovery() error {
 		fairmix := enode.NewFairMix(0)
 		for i := 0; i < discoveryParallelLookups; i++ {
 			iter := s.p2pServer.DiscoveryV4().RandomNodes()
-			iter = enode.NewBufferIter(iter, discoveryPrefetchBuffer)
 			iter = enode.AsyncFilter(iter, s.p2pServer.DiscoveryV4().RequestENR, maxParallelENRRequests)
 			iter = enode.Filter(iter, eth.NewNodeFilter(s.blockchain))
+			iter = enode.NewBufferIter(iter, discoveryPrefetchBuffer)
 			fairmix.AddSource(iter, fmt.Sprintf("DiscoveryV4-%d", i))
 		}
 		s.discmix.AddSource(fairmix, "DiscoveryV4")
@@ -535,8 +535,8 @@ func (s *Ethereum) setupDiscovery() error {
 		fairmix := enode.NewFairMix(0)
 		for i := 0; i < discoveryParallelLookups; i++ {
 			iter := s.p2pServer.DiscoveryV5().RandomNodes()
-			iter = enode.NewBufferIter(iter, discoveryPrefetchBuffer)
 			iter = enode.Filter(iter, eth.NewNodeFilter(s.blockchain))
+			iter = enode.NewBufferIter(iter, discoveryPrefetchBuffer)
 			fairmix.AddSource(iter, fmt.Sprintf("DiscoveryV5-%d", i))
 		}
 		s.discmix.AddSource(fairmix, "DiscoveryV5")