Reduce fingerprinting through timestamps in 'addr' messages.

Suggested by Jonas Nick.

Rebased-From: 9c27379
Github-Pull: #5860

src/addrman.cpp

@@ -272,8 +272,9 @@ void CAddrMan::Good_(const CService& addr, int64_t nTime)
     // update info
     info.nLastSuccess = nTime;
     info.nLastTry = nTime;
-    info.nTime = nTime;
     info.nAttempts = 0;
+    // nTime is not updated here, to avoid leaking information about
+    // currently-connected peers.
 
     // if it is already in the tried set, don't do anything else
     if (info.fInTried)

src/main.cpp

@@ -231,6 +231,10 @@ struct CBlockReject {
  * and we're no longer holding the node's locks.
  */
 struct CNodeState {
+    //! The peer's address
+    CService address;
+    //! Whether we have a fully established connection.
+    bool fCurrentlyConnected;
     //! Accumulated misbehaviour score for this peer.
     int nMisbehavior;
     //! Whether this peer should be disconnected and banned (unless whitelisted).
@@ -255,6 +259,7 @@ struct CNodeState {
     bool fPreferredDownload;
 
     CNodeState() {
+        fCurrentlyConnected = false;
         nMisbehavior = 0;
         fShouldBan = false;
         pindexBestKnownBlock = NULL;
@@ -298,6 +303,7 @@ void InitializeNode(NodeId nodeid, const CNode *pnode) {
     LOCK(cs_main);
     CNodeState &state = mapNodeState.insert(std::make_pair(nodeid, CNodeState())).first->second;
     state.name = pnode->addrName;
+    state.address = pnode->addr;
 }
 
 void FinalizeNode(NodeId nodeid) {
@@ -307,6 +313,10 @@ void FinalizeNode(NodeId nodeid) {
     if (state->fSyncStarted)
         nSyncStarted--;
 
+    if (state->nMisbehavior == 0 && state->fCurrentlyConnected) {
+        AddressCurrentlyConnected(state->address);
+    }
+
     BOOST_FOREACH(const QueuedBlock& entry, state->vBlocksInFlight)
         mapBlocksInFlight.erase(entry.hash);
     EraseOrphansFor(nodeid);
@@ -3563,6 +3573,12 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv,
     else if (strCommand == "verack")
     {
         pfrom->SetRecvVersion(min(pfrom->nVersion, PROTOCOL_VERSION));
+
+        // Mark this node as currently connected, so we update its timestamp later.
+        if (pfrom->fNetworkNode) {
+            LOCK(cs_main);
+            State(pfrom->GetId())->fCurrentlyConnected = true;
+        }
     }
 
 
@@ -4207,11 +4223,6 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv,
     }
 
 
-    // Update the last seen time for this node's address
-    if (pfrom->fNetworkNode)
-        if (strCommand == "version" || strCommand == "addr" || strCommand == "inv" || strCommand == "getdata" || strCommand == "ping")
-            AddressCurrentlyConnected(pfrom->addr);
-
 
     return true;
 }