downloader: added demotion / promotion in prep. for rep. system

eth/downloader/downloader.go

@@ -245,6 +245,7 @@ out:
 	for {
 		select {
 		case blockPack := <-d.blockCh:
+			d.peers[blockPack.peerId].promote()
 			d.queue.deliver(blockPack.peerId, blockPack.blocks)
 			d.peers.setState(blockPack.peerId, idleState)
 		case <-ticker.C:
@@ -310,6 +311,9 @@ out:
 					// 2) Measure their speed;
 					// 3) Amount and availability.
 					d.queue.deliver(pid, nil)
+					if peer := p.peers[pid]; peer != nil {
+						peer.demote()
+					}
 				}
 
 			}
@@ -343,6 +347,7 @@ func (d *Downloader) AddBlock(id string, block *types.Block, td *big.Int) {
 	peer.td = td
 	peer.recentHash = block.Hash()
 	peer.mu.Unlock()
+	peer.promote()
 
 	glog.V(logger.Detail).Infoln("Inserting new block from:", id)
 	d.queue.addBlock(id, block, td)

eth/downloader/peer.go

@@ -95,3 +95,23 @@ func (p *peer) fetch(chunk *chunk) error {
 
 	return nil
 }
+
+// promote increases the peer's reputation
+func (p *peer) promote() {
+	p.mu.Lock()
+	defer p.mu.Unlock()
+
+	p.rep++
+}
+
+// demote decreases the peer's reputation or leaves it at 0
+func (p *peer) demote() {
+	p.mu.Lock()
+	defer p.mu.Unlock()
+
+	if p.rep > 1 {
+		p.rep -= 2
+	} else {
+		p.rep = 0
+	}
+}