From 4f95e2f9ec3e416773e6a87b3c76667d97894f36 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?P=C3=A9ter=20Szil=C3=A1gyi?= <peterke@gmail.com>
Date: Thu, 9 Jul 2015 13:55:06 +0300
Subject: [PATCH] eth: calculate the correct TD, only update if better

---
 eth/handler.go | 18 +++++++++++++++---
 eth/peer.go    |  4 ++--
 2 files changed, 17 insertions(+), 5 deletions(-)

diff --git a/eth/handler.go b/eth/handler.go
index bbb251812..50e2ac99b 100644
--- a/eth/handler.go
+++ b/eth/handler.go
@@ -19,6 +19,7 @@ package eth
 import (
 	"fmt"
 	"math"
+	"math/big"
 	"sync"
 	"time"
 
@@ -412,8 +413,10 @@ func (pm *ProtocolManager) handleMsg(p *peer) error {
 		pm.fetcher.Enqueue(p.id, request.Block)
 
 		// TODO: Schedule a sync to cover potential gaps (this needs proto update)
-		p.SetTd(request.TD)
-		go pm.synchronise(p)
+		if request.TD.Cmp(p.Td()) > 0 {
+			p.SetTd(request.TD)
+			go pm.synchronise(p)
+		}
 
 	case TxMsg:
 		// Transactions arrived, parse all of them and deliver to the pool
@@ -452,9 +455,18 @@ func (pm *ProtocolManager) BroadcastBlock(block *types.Block, propagate bool) {
 
 	// If propagation is requested, send to a subset of the peer
 	if propagate {
+		// Calculate the TD of the block (it's not imported yet, so block.Td is not valid)
+		var td *big.Int
+		if parent := pm.chainman.GetBlock(block.ParentHash()); parent != nil {
+			td = new(big.Int).Add(parent.Td, block.Difficulty())
+		} else {
+			glog.V(logger.Error).Infof("propagating dangling block #%d [%x]", block.NumberU64(), hash[:4])
+			return
+		}
+		// Send the block to a subset of our peers
 		transfer := peers[:int(math.Sqrt(float64(len(peers))))]
 		for _, peer := range transfer {
-			peer.SendNewBlock(block)
+			peer.SendNewBlock(block, td)
 		}
 		glog.V(logger.Detail).Infof("propagated block %x to %d peers in %v", hash[:4], len(transfer), time.Since(block.ReceivedAt))
 	}
diff --git a/eth/peer.go b/eth/peer.go
index ccd5d3c6f..d70ad4c94 100644
--- a/eth/peer.go
+++ b/eth/peer.go
@@ -167,12 +167,12 @@ func (p *peer) SendNewBlockHashes(hashes []common.Hash) error {
 }
 
 // SendNewBlock propagates an entire block to a remote peer.
-func (p *peer) SendNewBlock(block *types.Block) error {
+func (p *peer) SendNewBlock(block *types.Block, td *big.Int) error {
 	propBlockOutPacketsMeter.Mark(1)
 	propBlockOutTrafficMeter.Mark(block.Size().Int64())
 
 	p.knownBlocks.Add(block.Hash())
-	return p2p.Send(p.rw, NewBlockMsg, []interface{}{block, block.Td})
+	return p2p.Send(p.rw, NewBlockMsg, []interface{}{block, td})
 }
 
 // RequestHashes fetches a batch of hashes from a peer, starting at from, going