Hopefully fix rare coredump #89

We now create a new lock for vRelayNodes, which becomes a global instead of
function level variable. This should prevent the rare case when pnode = NULL.
Also, to be even safer, we now check if pnode is NULL and if it is, we log
that we are ignoring it and go to the next iteration of the loop.

src/net.cpp

@@ -118,6 +118,9 @@ extern void StartShutdown();
 
 vector<CNode*> vNodes;
 CCriticalSection cs_vNodes;
+vector<CNode*> vRelayNodes;
+CCriticalSection cs_vRelayNodes;
+
 map<CInv, CDataStream> mapRelay;
 deque<pair<int64_t, CInv> > vRelayExpiration;
 CCriticalSection cs_mapRelay;
@@ -2110,9 +2113,11 @@ void RelayTransaction(const CTransaction& tx, const CDataStream& ss)
         mapRelay.insert(std::make_pair(inv, ss));
         vRelayExpiration.push_back(std::make_pair(GetTime() + 15 * 60, inv));
     }
-    LOCK(cs_vNodes);
 
-    auto vRelayNodes = vNodes;
+    LOCK2(cs_vNodes, cs_vRelayNodes);
+
+    // make a copy of our full node list so we can choose a subset to relay to
+    vRelayNodes = vNodes;
 
     // We always round down, except when we have only 1 connection
     auto newSize = (vNodes.size() / 2) == 0 ? 1 : (vNodes.size() / 2);
@@ -2120,11 +2125,17 @@ void RelayTransaction(const CTransaction& tx, const CDataStream& ss)
     random_shuffle( vRelayNodes.begin(), vRelayNodes.end(), GetRandInt );
 
     vRelayNodes.resize(newSize);
+    // We do not log this to debug.log because it leaks metadata about how many
+    // peers this node had at a certain timestamp
     fprintf(stderr, "%s: Relaying to %lu of %lu peers\n", __func__, newSize, vNodes.size() );
 
     // Only relay to randomly chosen 50% of peers
     BOOST_FOREACH(CNode* pnode, vRelayNodes)
     {
+        if(!pnode) {
+            LogPrintf("%s: invalid relay node found, ignoring\n", __func__);
+            continue;
+        }
         if(!pnode->fRelayTxes)
             continue;
         LOCK(pnode->cs_filter);

src/net.h

@@ -179,6 +179,9 @@ extern int nMaxConnections;
 
 extern std::vector<CNode*> vNodes;
 extern CCriticalSection cs_vNodes;
+extern std::vector<CNode*> vRelayNodes;
+extern CCriticalSection cs_vRelayNodes;
+
 extern std::map<CInv, CDataStream> mapRelay;
 extern std::deque<std::pair<int64_t, CInv> > vRelayExpiration;
 extern CCriticalSection cs_mapRelay;