1 files changed, 38 insertions, 5 deletions

diff --git a/src/net_processing.cpp b/src/net_processing.cpp
index bf9307727a..482a206c8b 100644
--- a/src/net_processing.cpp
+++ b/src/net_processing.cpp
@@ -401,6 +401,12 @@ void UpdateBlockAvailability(NodeId nodeid, const uint256 &hash) {
     }
 }
 
+/**
+ * When a peer sends us a valid block, instruct it to announce blocks to us
+ * using CMPCTBLOCK if possible by adding its nodeid to the end of
+ * lNodesAnnouncingHeaderAndIDs, and keeping that list under a certain size by
+ * removing the first element if necessary.
+ */
 void MaybeSetPeerAsAnnouncingHeaderAndIDs(NodeId nodeid, CConnman* connman) {
     AssertLockHeld(cs_main);
     CNodeState* nodestate = State(nodeid);
@@ -749,7 +755,11 @@ unsigned int LimitOrphanTxSize(unsigned int nMaxOrphans)
     return nEvicted;
 }
 
-// Requires cs_main.
+/**
+ * Mark a misbehaving peer to be banned depending upon the value of `-banscore`.
+ *
+ * Requires cs_main.
+ */
 void Misbehaving(NodeId pnode, int howmuch, const std::string& message)
 {
     if (howmuch == 0)
@@ -808,6 +818,10 @@ PeerLogicValidation::PeerLogicValidation(CConnman* connmanIn, CScheduler &schedu
     scheduler.scheduleEvery(std::bind(&PeerLogicValidation::CheckForStaleTipAndEvictPeers, this, consensusParams), EXTRA_PEER_CHECK_INTERVAL * 1000);
 }
 
+/**
+ * Evict orphan txn pool entries (EraseOrphanTx) based on a newly connected
+ * block. Also save the time of the last tip update.
+ */
 void PeerLogicValidation::BlockConnected(const std::shared_ptr<const CBlock>& pblock, const CBlockIndex* pindex, const std::vector<CTransactionRef>& vtxConflicted) {
     LOCK(g_cs_orphans);
 
@@ -828,7 +842,7 @@ void PeerLogicValidation::BlockConnected(const std::shared_ptr<const CBlock>& pb
         }
     }
 
-    // Erase orphan transactions include or precluded by this block
+    // Erase orphan transactions included or precluded by this block
     if (vOrphanErase.size()) {
         int nErased = 0;
         for (uint256 &orphanHash : vOrphanErase) {
@@ -847,6 +861,10 @@ static std::shared_ptr<const CBlockHeaderAndShortTxIDs> most_recent_compact_bloc
 static uint256 most_recent_block_hash;
 static bool fWitnessesPresentInMostRecentCompactBlock;
 
+/**
+ * Maintain state about the best-seen block and fast-announce a compact block 
+ * to compatible peers.
+ */
 void PeerLogicValidation::NewPoWValidBlock(const CBlockIndex *pindex, const std::shared_ptr<const CBlock>& pblock) {
     std::shared_ptr<const CBlockHeaderAndShortTxIDs> pcmpctblock = std::make_shared<const CBlockHeaderAndShortTxIDs> (*pblock, true);
     const CNetMsgMaker msgMaker(PROTOCOL_VERSION);
@@ -888,10 +906,15 @@ void PeerLogicValidation::NewPoWValidBlock(const CBlockIndex *pindex, const std:
     });
 }
 
+/**
+ * Update our best height and announce any block hashes which weren't previously 
+ * in chainActive to our peers.
+ */
 void PeerLogicValidation::UpdatedBlockTip(const CBlockIndex *pindexNew, const CBlockIndex *pindexFork, bool fInitialDownload) {
     const int nNewHeight = pindexNew->nHeight;
     connman->SetBestHeight(nNewHeight);
 
+    SetServiceFlagsIBDCache(!fInitialDownload);
     if (!fInitialDownload) {
         // Find the hashes of all blocks that weren't previously in the best chain.
         std::vector<uint256> vHashes;
@@ -919,6 +942,10 @@ void PeerLogicValidation::UpdatedBlockTip(const CBlockIndex *pindexNew, const CB
     nTimeBestReceived = GetTime();
 }
 
+/**
+ * Handle invalid block rejection and consequent peer banning, maintain which 
+ * peers announce compact blocks.
+ */
 void PeerLogicValidation::BlockChecked(const CBlock& block, const CValidationState& state) {
     LOCK(cs_main);
 
@@ -1642,7 +1669,13 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr
             pfrom->cleanSubVer = cleanSubVer;
         }
         pfrom->nStartingHeight = nStartingHeight;
-        pfrom->fClient = !(nServices & NODE_NETWORK);
+
+        // set nodes not relaying blocks and tx and not serving (parts) of the historical blockchain as "clients"
+        pfrom->fClient = (!(nServices & NODE_NETWORK) && !(nServices & NODE_NETWORK_LIMITED));
+
+        // set nodes not capable of serving the complete blockchain history as "limited nodes"
+        pfrom->m_limited_node = (!(nServices & NODE_NETWORK) && (nServices & NODE_NETWORK_LIMITED));
+
         {
             LOCK(pfrom->cs_filter);
             pfrom->fRelayTxes = fRelay; // set to true after we get the first filter* message
@@ -1801,7 +1834,7 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr
             // We only bother storing full nodes, though this may include
             // things which we would not make an outbound connection to, in
             // part because we may make feeler connections to them.
-            if (!MayHaveUsefulAddressDB(addr.nServices))
+            if (!MayHaveUsefulAddressDB(addr.nServices) && !HasAllDesirableServiceFlags(addr.nServices))
                 continue;
 
             if (addr.nTime <= 100000000 || addr.nTime > nNow + 10 * 60)
@@ -3611,7 +3644,7 @@ bool PeerLogicValidation::SendMessages(CNode* pto, std::atomic<bool>& interruptM
         // Message: getdata (blocks)
         //
         std::vector<CInv> vGetData;
-        if (!pto->fClient && (fFetch || !IsInitialBlockDownload()) && state.nBlocksInFlight < MAX_BLOCKS_IN_TRANSIT_PER_PEER) {
+        if (!pto->fClient && ((fFetch && !pto->m_limited_node) || !IsInitialBlockDownload()) && state.nBlocksInFlight < MAX_BLOCKS_IN_TRANSIT_PER_PEER) {
             std::vector<const CBlockIndex*> vToDownload;
             NodeId staller = -1;
             FindNextBlocksToDownload(pto->GetId(), MAX_BLOCKS_IN_TRANSIT_PER_PEER - state.nBlocksInFlight, vToDownload, staller, consensusParams);