From 219a6131f4169c9b5ca9dc9420278ffa1a5f6d32 Mon Sep 17 00:00:00 2001
From: Dave Collins <davec@conformal.com>
Date: Mon, 7 Oct 2013 09:04:11 -0500
Subject: [PATCH] Correct all list/container loops that remove items.

It is not safe to remove an item from a container/list while iterating the
list without first saving the next pointer since removing the item nils
the internal list element's next pointer.
---
 blockmanager.go | 8 ++++++--
 mempool.go      | 4 +++-
 server.go       | 4 +++-
 3 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/blockmanager.go b/blockmanager.go
index 8f5f408a..8066de39 100644
--- a/blockmanager.go
+++ b/blockmanager.go
@@ -95,7 +95,9 @@ func (b *blockManager) startSync(peers *list.List) {
 	}
 
 	var bestPeer *peer
-	for e := peers.Front(); e != nil; e = e.Next() {
+	var enext *list.Element
+	for e := peers.Front(); e != nil; e = enext {
+		enext = e.Next()
 		p := e.Value.(*peer)
 
 		// Remove sync candidate peers that are no longer candidates due
@@ -187,7 +189,9 @@ func (b *blockManager) handleNewPeerMsg(peers *list.List, p *peer) {
 // is invoked from the syncHandler goroutine.
 func (b *blockManager) handleDonePeerMsg(peers *list.List, p *peer) {
 	// Remove the peer from the list of candidate peers.
-	for e := peers.Front(); e != nil; e = e.Next() {
+	var enext *list.Element
+	for e := peers.Front(); e != nil; e = enext {
+		enext = e.Next()
 		if e.Value == p {
 			peers.Remove(e)
 			break
diff --git a/mempool.go b/mempool.go
index 4401225a..2909cc94 100644
--- a/mempool.go
+++ b/mempool.go
@@ -292,7 +292,9 @@ func (mp *txMemPool) removeOrphan(txHash *btcwire.ShaHash) {
 	for _, txIn := range tx.TxIn {
 		originTxHash := txIn.PreviousOutpoint.Hash
 		if orphans, exists := mp.orphansByPrev[originTxHash]; exists {
-			for e := orphans.Front(); e != nil; e = e.Next() {
+			var enext *list.Element
+			for e := orphans.Front(); e != nil; e = enext {
+				enext = e.Next()
 				if e.Value.(*btcwire.MsgTx) == tx {
 					orphans.Remove(e)
 					break
diff --git a/server.go b/server.go
index 90d6d395..6576b203 100644
--- a/server.go
+++ b/server.go
@@ -116,7 +116,9 @@ func (s *server) handleAddPeerMsg(peers *list.List, banned map[string]time.Time,
 // handleDonePeerMsg deals with peers that have signalled they are done.  It is
 // invoked from the peerHandler goroutine.
 func (s *server) handleDonePeerMsg(peers *list.List, p *peer) bool {
-	for e := peers.Front(); e != nil; e = e.Next() {
+	var enext *list.Element
+	for e := peers.Front(); e != nil; e = enext {
+		enext = e.Next()
 		if e.Value == p {
 			// Issue an asynchronous reconnect if the peer was a
 			// persistent outbound connection.