Correct getdata throttling.

This commit corrects an issue where the data requested by getdata was not
being properly throttled which could lead to higher than desired memory
usage on large requests.

peer.go

@@ -414,6 +414,10 @@ func (p *peer) pushTxMsg(sha *btcwire.ShaHash, doneChan, waitChan chan bool) err
 	if err != nil {
 		peerLog.Tracef("Unable to fetch tx %v from transaction "+
 			"pool: %v", sha, err)
+
+		if doneChan != nil {
+			doneChan <- false
+		}
 		return err
 	}
 
@@ -434,6 +438,10 @@ func (p *peer) pushBlockMsg(sha *btcwire.ShaHash, doneChan, waitChan chan bool)
 	if err != nil {
 		peerLog.Tracef("Unable to fetch requested block sha %v: %v",
 			sha, err)
+
+		if doneChan != nil {
+			doneChan <- false
+		}
 		return err
 	}
 
@@ -465,10 +473,7 @@ func (p *peer) pushBlockMsg(sha *btcwire.ShaHash, doneChan, waitChan chan bool)
 			p.QueueMessage(invMsg, doneChan)
 			p.continueHash = nil
 		} else if doneChan != nil {
-			// Avoid deadlock when caller waits on channel.
-			go func() {
-				doneChan <- false
-			}()
+			doneChan <- false
 		}
 	}
 	return nil
@@ -658,15 +663,15 @@ func (p *peer) handleGetDataMsg(msg *btcwire.MsgGetData) {
 	// The waiting occurs after the database fetch for the next one to
 	// provide a little pipelining.
 	var waitChan chan bool
-	doneChan := make(chan bool)
+	doneChan := make(chan bool, 1)
 
 	for i, iv := range msg.InvList {
 		var c chan bool
 		// If this will be the last message we send.
 		if i == len(msg.InvList)-1 && len(notFound.InvList) == 0 {
 			c = doneChan
-		} else if i > 0 && i+1%3 == 0 {
-			// buffered so as to not make the send goroutine block.
+		} else if (i+1)%3 == 0 {
+			// Buffered so as to not make the send goroutine block.
 			c = make(chan bool, 1)
 		}
 		var err error
@@ -684,6 +689,15 @@ func (p *peer) handleGetDataMsg(msg *btcwire.MsgGetData) {
 		}
 		if err != nil {
 			notFound.AddInvVect(iv)
+
+			// When there is a failure fetching the final entry
+			// and the done channel was sent in due to there
+			// being no outstanding not found inventory, consume
+			// it here because there is now not found inventory
+			// that will use the channel momentarily.
+			if i == len(msg.InvList)-1 && c != nil {
+				<-c
+			}
 		}
 		numAdded++
 		waitChan = c