net: fix a few races. Credit @TheBlueMatt

These are (afaik) all long-standing races or concurrent accesses. Going
forward, we can clean these up so that they're not all individual atomic
accesses.

- Reintroduce cs_vRecv to guard receive-specific vars
- Lock vRecv/vSend for CNodeStats
- Make some vars atomic.
- Only set the connection time in CNode's constructor so that it doesn't change

src/net.cpp

@@ -389,7 +389,6 @@ CNode* CConnman::ConnectNode(CAddress addrConnect, const char *pszDest, bool fCo
         uint64_t nonce = GetDeterministicRandomizer(RANDOMIZER_ID_LOCALHOSTNONCE).Write(id).Finalize();
         CNode* pnode = new CNode(id, nLocalServices, GetBestHeight(), hSocket, addrConnect, CalculateKeyedNetGroup(addrConnect), nonce, pszDest ? pszDest : "", false);
         pnode->nServicesExpected = ServiceFlags(addrConnect.nServices & nRelevantServices);
-        pnode->nTimeConnected = GetSystemTimeInSeconds();
         pnode->AddRef();
 
         return pnode;
@@ -612,10 +611,16 @@ void CNode::copyStats(CNodeStats &stats)
     X(fInbound);
     X(fAddnode);
     X(nStartingHeight);
-    X(nSendBytes);
+    {
+        LOCK(cs_vSend);
         X(mapSendBytesPerMsgCmd);
-    X(nRecvBytes);
+        X(nSendBytes);
+    }
+    {
+        LOCK(cs_vRecv);
         X(mapRecvBytesPerMsgCmd);
+        X(nRecvBytes);
+    }
     X(fWhitelisted);
 
     // It is common for nodes with good ping times to suddenly become lagged,
@@ -643,6 +648,7 @@ bool CNode::ReceiveMsgBytes(const char *pch, unsigned int nBytes, bool& complete
 {
     complete = false;
     int64_t nTimeMicros = GetTimeMicros();
+    LOCK(cs_vRecv);
     nLastRecv = nTimeMicros / 1000000;
     nRecvBytes += nBytes;
     while (nBytes > 0) {

src/net.h

@@ -573,6 +573,7 @@ public:
     std::deque<std::vector<unsigned char>> vSendMsg;
     CCriticalSection cs_vSend;
     CCriticalSection cs_hSocket;
+    CCriticalSection cs_vRecv;
 
     CCriticalSection cs_vProcessMsg;
     std::list<CNetMessage> vProcessMsg;
@@ -584,10 +585,10 @@ public:
     uint64_t nRecvBytes;
     std::atomic<int> nRecvVersion;
 
-    int64_t nLastSend;
+    std::atomic<int64_t> nLastSend;
-    int64_t nLastRecv;
+    std::atomic<int64_t> nLastRecv;
     int64_t nTimeConnected;
-    int64_t nTimeOffset;
+    std::atomic<int64_t> nTimeOffset;
     const CAddress addr;
     std::string addrName;
     CService addrLocal;
@@ -614,7 +615,7 @@ public:
     CSemaphoreGrant grantOutbound;
     CCriticalSection cs_filter;
     CBloomFilter* pfilter;
-    int nRefCount;
+    std::atomic<int> nRefCount;
     const NodeId id;
 
     const uint64_t nKeyedNetGroup;
@@ -665,15 +666,15 @@ public:
 
     // Ping time measurement:
     // The pong reply we're expecting, or 0 if no pong expected.
-    uint64_t nPingNonceSent;
+    std::atomic<uint64_t> nPingNonceSent;
     // Time (in usec) the last ping was sent, or 0 if no ping was ever sent.
-    int64_t nPingUsecStart;
+    std::atomic<int64_t> nPingUsecStart;
     // Last measured round-trip time.
-    int64_t nPingUsecTime;
+    std::atomic<int64_t> nPingUsecTime;
     // Best measured round-trip time.
-    int64_t nMinPingUsecTime;
+    std::atomic<int64_t> nMinPingUsecTime;
     // Whether a ping is requested.
-    bool fPingQueued;
+    std::atomic<bool> fPingQueued;
     // Minimum fee rate with which to filter inv's to this node
     CAmount minFeeFilter;
     CCriticalSection cs_feeFilter;

src/net_processing.cpp

@@ -2450,7 +2450,7 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr
                     if (pingUsecTime > 0) {
                         // Successful ping time measurement, replace previous
                         pfrom->nPingUsecTime = pingUsecTime;
-                        pfrom->nMinPingUsecTime = std::min(pfrom->nMinPingUsecTime, pingUsecTime);
+                        pfrom->nMinPingUsecTime = std::min(pfrom->nMinPingUsecTime.load(), pingUsecTime);
                     } else {
                         // This should never happen
                         sProblem = "Timing mishap";