Added ping time measurement.

New RPC "ping" command to request ping.
Implemented "pong" message handler.
New "pingtime" field in getpeerinfo, to provide results to user.
New "pingwait" field, to show pings still in flight, to better see newly lagging peers.

src/net.h

@@ -119,6 +119,8 @@ public:
     uint64 nSendBytes;
     uint64 nRecvBytes;
     bool fSyncNode;
+    double dPingTime;
+    double dPingWait;
 };
 
 
@@ -234,6 +236,12 @@ public:
     CCriticalSection cs_inventory;
     std::multimap<int64, CInv> mapAskFor;
 
+    // Ping time measurement
+    uint64 nPingNonceSent;
+    int64 nPingUsecStart;
+    int64 nPingUsecTime;
+    bool fPingQueued;
+    
     CNode(SOCKET hSocketIn, CAddress addrIn, std::string addrNameIn = "", bool fInboundIn=false) : ssSend(SER_NETWORK, MIN_PROTO_VERSION)
     {
         nServices = 0;
@@ -268,6 +276,10 @@ public:
         fRelayTxes = false;
         setInventoryKnown.max_size(SendBufferSize() / 1000);
         pfilter = new CBloomFilter();
+        nPingNonceSent = 0;
+        nPingUsecStart = 0;
+        nPingUsecTime = 0;
+        fPingQueued = false;
 
         // Be shy and don't send version until we hear
         if (hSocket != INVALID_SOCKET && !fInbound)