partial/logic backport bitcoin#18544: net: limit BIP37 filter lifespa…

…n (active between 'filterload'..'filterclear') (#4043)

* partial backport 18544: net: limit BIP37 filter lifespan (active between 'filterload'..'filterclear')

Previously, a default match-everything bloom filter was set for every peer,
i.e. even before receiving a 'filterload' message and after receiving a
'filterclear' message code branches checking for the existence of the filter
by testing the pointer "pfilter" were _always_ executed.

* net: Match the backport PR a bit more

Co-authored-by: xdustinface <xdustinfacex@gmail.com>

src/net.cpp

@@ -3913,7 +3913,6 @@ CNode::CNode(NodeId idIn, ServiceFlags nLocalServicesIn, int nMyStartingHeightIn
     nNextAddrSend = 0;
     fRelayTxes = false;
     fSentAddr = false;
-    pfilter = MakeUnique<CBloomFilter>();
     timeLastMempoolReq = 0;
     nLastBlockTime = 0;
     nLastTXTime = 0;

src/net.h

@@ -900,7 +900,7 @@ class CNode
     bool m_masternode_iqr_connection{false};
     CSemaphoreGrant grantOutbound;
     CCriticalSection cs_filter;
-    std::unique_ptr<CBloomFilter> pfilter PT_GUARDED_BY(cs_filter);
+    std::unique_ptr<CBloomFilter> pfilter PT_GUARDED_BY(cs_filter){nullptr};
     std::atomic<int> nRefCount;
 
     const uint64_t nKeyedNetGroup;

src/net_processing.cpp

@@ -3493,7 +3493,7 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr
     if (strCommand == NetMsgType::FILTERCLEAR) {
         LOCK(pfrom->cs_filter);
         if (pfrom->GetLocalServices() & NODE_BLOOM) {
-            pfrom->pfilter.reset(new CBloomFilter());
+            pfrom->pfilter = nullptr;
         }
         pfrom->fRelayTxes = true;
         return true;