From f4ac02ee7c6530c273503d8575a492e9b2ac1f13 Mon Sep 17 00:00:00 2001
From: Kaz Wesley <keziahw@gmail.com>
Date: Wed, 27 Apr 2016 09:26:33 -0700
Subject: [PATCH] fix race that could fail to persist a ban

DumpBanList currently does this:
  - with lock: take a copy of the banmap
  - perform I/O (write out the banmap)
  - with lock: mark the banmap non-dirty
If a new ban is added during the I/O operation, it may never be persisted to
disk.

Reorder operations so that the data to be persisted cannot be older than the
time at which the banmap was marked non-dirty.
---
 src/net.cpp | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/src/net.cpp b/src/net.cpp
index 7dec8fc1c..f566af24c 100644
--- a/src/net.cpp
+++ b/src/net.cpp
@@ -2634,9 +2634,10 @@ void DumpBanlist()
 
     CBanDB bandb;
     banmap_t banmap;
+    CNode::SetBannedSetDirty(false);
     CNode::GetBanned(banmap);
-    if (bandb.Write(banmap))
-        CNode::SetBannedSetDirty(false);
+    if (!bandb.Write(banmap))
+        CNode::SetBannedSetDirty(true);
 
     LogPrint("net", "Flushed %d banned node ips/subnets to banlist.dat  %dms\n",
         banmap.size(), GetTimeMillis() - nStart);