Connect to peers signaling NODE_NETWORK_LIMITED when out-of-IBD

src/net.cpp

@@ -2710,6 +2710,7 @@ CNode::CNode(NodeId idIn, ServiceFlags nLocalServicesIn, int nMyStartingHeightIn
     fOneShot = false;
     m_manual_connection = false;
     fClient = false; // set by version message
+    m_limited_node = false; // set by version message
     fFeeler = false;
     fSuccessfullyConnected = false;
     fDisconnect = false;

src/net.h

@@ -643,6 +643,7 @@ public:
     bool fOneShot;
     bool m_manual_connection;
     bool fClient;
+    bool m_limited_node; //after BIP159
     const bool fInbound;
     std::atomic_bool fSuccessfullyConnected;
     std::atomic_bool fDisconnect;

src/net_processing.cpp

@@ -892,6 +892,7 @@ void PeerLogicValidation::UpdatedBlockTip(const CBlockIndex *pindexNew, const CB
     const int nNewHeight = pindexNew->nHeight;
     connman->SetBestHeight(nNewHeight);
 
+    g_initial_block_download_completed = !fInitialDownload;
     if (!fInitialDownload) {
         // Find the hashes of all blocks that weren't previously in the best chain.
         std::vector<uint256> vHashes;
@@ -1642,7 +1643,13 @@ 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
@@ -3611,7 +3618,7 @@ 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);

src/protocol.cpp

@@ -12,6 +12,8 @@
 # include <arpa/inet.h>
 #endif
 
+std::atomic<bool> g_initial_block_download_completed(false);
+
 namespace NetMsgType {
 const char *VERSION="version";
 const char *VERACK="verack";

src/protocol.h

@@ -15,6 +15,7 @@
 #include <uint256.h>
 #include <version.h>
 
+#include <atomic>
 #include <stdint.h>
 #include <string>
 
@@ -277,6 +278,7 @@ enum ServiceFlags : uint64_t {
     // BIP process.
 };
 
+extern std::atomic<bool> g_initial_block_download_completed;
 /**
  * Gets the set of service flags which are "desirable" for a given peer.
  *
@@ -302,6 +304,9 @@ enum ServiceFlags : uint64_t {
  * should be updated appropriately to filter for the same nodes.
  */
 static ServiceFlags GetDesirableServiceFlags(ServiceFlags services) {
+    if ((services & NODE_NETWORK_LIMITED) && g_initial_block_download_completed) {
+        return ServiceFlags(NODE_NETWORK_LIMITED | NODE_WITNESS);
+    }
     return ServiceFlags(NODE_NETWORK | NODE_WITNESS);
 }