ETH: Fix inaccurate default difficulty

Author: SwimmingTiger

DownSessionETH.go

@@ -517,7 +517,7 @@ func (down *DownSessionETH) submitResponse(e EventSubmitResponse) {
 
 func (down *DownSessionETH) setDifficulty(e EventSetDifficulty) {
 	if down.protocol == ProtocolEthereumStratum && down.jobDiff != e.Difficulty {
-		diff := float64(e.Difficulty) / float64(0xffffffff)
+		diff := float64(e.Difficulty) / 4294967296.0
 
 		var request JSONRPCRequest
 		request.Method = "mining.set_difficulty"

UpSessionETH.go

@@ -8,7 +8,6 @@ import (
 	"errors"
 	"fmt"
 	"io"
-	"math"
 	"net"
 	"strconv"
 	"time"
@@ -349,7 +348,10 @@ func (up *UpSessionETH) handleSetDifficulty(rpcData *JSONRPCLineETH, jsonBytes [
 			return
 		}
 		// nicehash_diff = btcpool_diff / pow(2, 32)
-		up.defaultDiff = uint64(math.Round(diff * 0xffffffff))
+		up.defaultDiff = uint64(diff * 4294967296.0)
+		if glog.V(5) {
+			glog.Info(up.id, "mining.set_difficulty: ", diff, " -> ", up.defaultDiff)
+		}
 
 		e := EventSetDifficulty{up.defaultDiff}
 		for _, down := range up.downSessions {