Limit CNode::mapAskFor

Tighten resource constraints on CNode.

src/net.cpp

@@ -2106,6 +2106,8 @@ CNode::~CNode()
 
 void CNode::AskFor(const CInv& inv)
 {
+    if (mapAskFor.size() > MAPASKFOR_MAX_SZ)
+        return;
     // We're using mapAskFor as a priority queue,
     // the key is the earliest time the request can be sent
     int64_t nRequestTime;

src/net.h

@@ -51,6 +51,8 @@ static const bool DEFAULT_UPNP = USE_UPNP;
 #else
 static const bool DEFAULT_UPNP = false;
 #endif
+/** The maximum number of entries in mapAskFor */
+static const size_t MAPASKFOR_MAX_SZ = MAX_INV_SZ;
 
 unsigned int ReceiveFloodSize();
 unsigned int SendBufferSize();