Drop release times for CNode

It seems there were two mechanisms for assessing whether a CNode
was still in use: a refcount and a release timestamp. The latter
seems to have been there for a long time, as a safety mechanism.

However, this timer also keeps CNode objects alive for far longer
than necessary after disconnects, potentially opening up a DoS
window.

This commit removes the timestamp-based mechanism, and replaces
it with an assert(nRefCount >= 0), to verify that the refcounting
is indeed correctly working.

src/net.cpp

@@ -453,7 +453,7 @@ CNode* FindNode(const CService& addr)
     return NULL;
 }
 
-CNode* ConnectNode(CAddress addrConnect, const char *pszDest, int64 nTimeout)
+CNode* ConnectNode(CAddress addrConnect, const char *pszDest)
 {
     if (pszDest == NULL) {
         if (IsLocal(addrConnect))
@@ -463,9 +463,6 @@ CNode* ConnectNode(CAddress addrConnect, const char *pszDest, int64 nTimeout)
         CNode* pnode = FindNode((CService)addrConnect);
         if (pnode)
         {
-            if (nTimeout != 0)
-                pnode->AddRef(nTimeout);
-            else
             pnode->AddRef();
             return pnode;
         }
@@ -498,9 +495,6 @@ CNode* ConnectNode(CAddress addrConnect, const char *pszDest, int64 nTimeout)
 
         // Add node
         CNode* pnode = new CNode(hSocket, addrConnect, pszDest ? pszDest : "", false);
-        if (nTimeout != 0)
-            pnode->AddRef(nTimeout);
-        else
         pnode->AddRef();
 
         {
@@ -615,7 +609,6 @@ void CNode::copyStats(CNodeStats &stats)
     X(nVersion);
     X(strSubVer);
     X(fInbound);
-    X(nReleaseTime);
     X(nStartingHeight);
     X(nMisbehavior);
 }
@@ -773,7 +766,6 @@ void ThreadSocketHandler()
                     pnode->Cleanup();
 
                     // hold in disconnected pool until all refs are released
-                    pnode->nReleaseTime = max(pnode->nReleaseTime, GetTime() + 15 * 60);
                     if (pnode->fNetworkNode || pnode->fInbound)
                         pnode->Release();
                     vNodesDisconnected.push_back(pnode);

src/net.h

@@ -37,7 +37,7 @@ bool GetMyExternalIP(CNetAddr& ipRet);
 void AddressCurrentlyConnected(const CService& addr);
 CNode* FindNode(const CNetAddr& ip);
 CNode* FindNode(const CService& ip);
-CNode* ConnectNode(CAddress addrConnect, const char *strDest = NULL, int64 nTimeout=0);
+CNode* ConnectNode(CAddress addrConnect, const char *strDest = NULL);
 void MapPort(bool fUseUPnP);
 unsigned short GetListenPort();
 bool BindListenPort(const CService &bindAddr, std::string& strError=REF(std::string()));
@@ -99,7 +99,6 @@ public:
     int nVersion;
     std::string strSubVer;
     bool fInbound;
-    int64 nReleaseTime;
     int nStartingHeight;
     int nMisbehavior;
 };
@@ -187,8 +186,8 @@ public:
     CSemaphoreGrant grantOutbound;
     CCriticalSection cs_filter;
     CBloomFilter* pfilter;
-protected:
     int nRefCount;
+protected:
 
     // Denial-of-service detection/prevention
     // Key is IP address, value is banned-until-time
@@ -197,7 +196,6 @@ protected:
     int nMisbehavior;
 
 public:
-    int64 nReleaseTime;
     uint256 hashContinue;
     CBlockIndex* pindexLastGetBlocksBegin;
     uint256 hashLastGetBlocksEnd;
@@ -235,7 +233,6 @@ public:
         fSuccessfullyConnected = false;
         fDisconnect = false;
         nRefCount = 0;
-        nReleaseTime = 0;
         nSendSize = 0;
         nSendOffset = 0;
         hashContinue = 0;
@@ -272,7 +269,8 @@ public:
 
     int GetRefCount()
     {
-        return std::max(nRefCount, 0) + (GetTime() < nReleaseTime ? 1 : 0);
+        assert(nRefCount >= 0);
+        return nRefCount;
     }
 
     // requires LOCK(cs_vRecvMsg)
@@ -295,11 +293,8 @@ public:
             msg.SetVersion(nVersionIn);
     }
 
-    CNode* AddRef(int64 nTimeout=0)
+    CNode* AddRef()
     {
-        if (nTimeout != 0)
-            nReleaseTime = std::max(nReleaseTime, GetTime() + nTimeout);
-        else
         nRefCount++;
         return this;
     }

src/rpcnet.cpp

@@ -55,7 +55,6 @@ Value getpeerinfo(const Array& params, bool fHelp)
         obj.push_back(Pair("version", stats.nVersion));
         obj.push_back(Pair("subver", stats.strSubVer));
         obj.push_back(Pair("inbound", stats.fInbound));
-        obj.push_back(Pair("releasetime", (boost::int64_t)stats.nReleaseTime));
         obj.push_back(Pair("startingheight", stats.nStartingHeight));
         obj.push_back(Pair("banscore", stats.nMisbehavior));