Ping automatically every 2 minutes (unconditionally)

... instead of after 30 minutes of no sending, for latency measurement
and keep-alive. Also, disconnect if no reply arrives within 20 minutes,
instead of 90 of inactivity (for peers supporting the 'pong' message).

src/main.cpp

@@ -4296,8 +4296,8 @@ bool SendMessages(CNode* pto, bool fSendTrickle)
             // RPC ping request by user
             pingSend = true;
         }
-        if (pto->nLastSend && GetTime() - pto->nLastSend > 30 * 60 && pto->vSendMsg.empty()) {
-            // Ping automatically sent as a keepalive
+        if (pto->nPingNonceSent == 0 && pto->nPingUsecStart + PING_INTERVAL * 1000000 < GetTimeMicros()) {
+            // Ping automatically sent as a latency probe & keepalive.
             pingSend = true;
         }
         if (pingSend) {
@@ -4305,15 +4305,14 @@ bool SendMessages(CNode* pto, bool fSendTrickle)
             while (nonce == 0) {
                 RAND_bytes((unsigned char*)&nonce, sizeof(nonce));
             }
-            pto->nPingNonceSent = nonce;
             pto->fPingQueued = false;
+            pto->nPingUsecStart = GetTimeMicros();
             if (pto->nVersion > BIP0031_VERSION) {
-                // Take timestamp as close as possible before transmitting ping
-                pto->nPingUsecStart = GetTimeMicros();
+                pto->nPingNonceSent = nonce;
                 pto->PushMessage("ping", nonce);
             } else {
-                // Peer is too old to support ping command with nonce, pong will never arrive, disable timing
-                pto->nPingUsecStart = 0;
+                // Peer is too old to support ping command with nonce, pong will never arrive.
+                pto->nPingNonceSent = 0;
                 pto->PushMessage("ping");
             }
         }

src/net.cpp

@@ -1028,23 +1028,27 @@ void ThreadSocketHandler()
             //
             // Inactivity checking
             //
-            if (pnode->vSendMsg.empty())
-                pnode->nLastSendEmpty = GetTime();
-            if (GetTime() - pnode->nTimeConnected > 60)
+            int64_t nTime = GetTime();
+            if (nTime - pnode->nTimeConnected > 60)
             {
                 if (pnode->nLastRecv == 0 || pnode->nLastSend == 0)
                 {
                     LogPrint("net", "socket no message in first 60 seconds, %d %d\n", pnode->nLastRecv != 0, pnode->nLastSend != 0);
                     pnode->fDisconnect = true;
                 }
-                else if (GetTime() - pnode->nLastSend > 90*60 && GetTime() - pnode->nLastSendEmpty > 90*60)
+                else if (nTime - pnode->nLastSend > TIMEOUT_INTERVAL)
                 {
-                    LogPrintf("socket not sending\n");
+                    LogPrintf("socket sending timeout: %is\n", nTime - pnode->nLastSend);
                     pnode->fDisconnect = true;
                 }
-                else if (GetTime() - pnode->nLastRecv > 90*60)
+                else if (nTime - pnode->nLastRecv > (pnode->nVersion > BIP0031_VERSION ? TIMEOUT_INTERVAL : 90*60))
                 {
-                    LogPrintf("socket inactivity timeout\n");
+                    LogPrintf("socket receive timeout: %is\n", nTime - pnode->nLastRecv);
+                    pnode->fDisconnect = true;
+                }
+                else if (pnode->nPingNonceSent && pnode->nPingUsecStart + TIMEOUT_INTERVAL * 1000000 < GetTimeMicros())
+                {
+                    LogPrintf("ping timeout: %fs\n", 0.000001 * (GetTimeMicros() - pnode->nPingUsecStart));
                     pnode->fDisconnect = true;
                 }
             }

src/net.h

@@ -28,6 +28,7 @@
 #include <boost/signals2/signal.hpp>
 #include <openssl/rand.h>
 
+
 class CAddrMan;
 class CBlockIndex;
 class CNode;
@@ -36,6 +37,10 @@ namespace boost {
     class thread_group;
 }
 
+/** Time between pings automatically sent out for latency probing and keepalive (in seconds). */
+static const int PING_INTERVAL = 2 * 60;
+/** Time after which to disconnect, after waiting for a ping response (or inactivity). */
+static const int TIMEOUT_INTERVAL = 20 * 60;
 /** The maximum number of entries in an 'inv' protocol message */
 static const unsigned int MAX_INV_SZ = 50000;
 /** -upnp default */
@@ -217,7 +222,6 @@ public:
 
     int64_t nLastSend;
     int64_t nLastRecv;
-    int64_t nLastSendEmpty;
     int64_t nTimeConnected;
     CAddress addr;
     std::string addrName;
@@ -273,10 +277,14 @@ public:
     CCriticalSection cs_inventory;
     std::multimap<int64_t, CInv> mapAskFor;
 
-    // Ping time measurement
+    // Ping time measurement:
+    // The pong reply we're expecting, or 0 if no pong expected.
     uint64_t nPingNonceSent;
+    // Time (in usec) the last ping was sent, or 0 if no ping was ever sent.
     int64_t nPingUsecStart;
+    // Last measured round-trip time.
     int64_t nPingUsecTime;
+    // Whether a ping is requested.
     bool fPingQueued;
 
     CNode(SOCKET hSocketIn, CAddress addrIn, std::string addrNameIn = "", bool fInboundIn=false) : ssSend(SER_NETWORK, INIT_PROTO_VERSION), setAddrKnown(5000)
@@ -288,7 +296,6 @@ public:
         nLastRecv = 0;
         nSendBytes = 0;
         nRecvBytes = 0;
-        nLastSendEmpty = GetTime();
         nTimeConnected = GetTime();
         addr = addrIn;
         addrName = addrNameIn == "" ? addr.ToStringIPPort() : addrNameIn;