An adapted version of btc@ed7068302c7490e8061cb3a558a0f83a465beeea

furszy · furszy · commit cb4fc6c10732 · 2021-01-18T09:35:58.000-03:00
Handle mempool requests in send loop, subject to trickle  By eliminating queued entries from the mempool response and responding only at trickle time, this makes the mempool no longer leak transaction arrival order information (as the mempool itself is also sorted)-- at least no more than relay itself leaks it.
diff --git a/src/net.cpp b/src/net.cpp
@@ -2438,6 +2438,7 @@ CNode::CNode(NodeId idIn, ServiceFlags nLocalServicesIn, int nMyStartingHeightIn
     hashContinue = UINT256_ZERO;
     nStartingHeight = -1;
     filterInventoryKnown.reset();
+    fSendMempool = false;
     fGetAddr = false;
     nNextLocalAddrSend = 0;
     nNextAddrSend = 0;
diff --git a/src/net.h b/src/net.h
@@ -623,6 +623,8 @@ class CNode
     std::multimap<int64_t, CInv> mapAskFor;
     std::vector<uint256> vBlockRequested;
     int64_t nNextInvSend;
+    // Used for BIP35 mempool sending, also protected by cs_inventory
+    bool fSendMempool;
 
     // Ping time measurement:
     // The pong reply we're expecting, or 0 if no pong expected.
diff --git a/src/net_processing.cpp b/src/net_processing.cpp
@@ -1633,27 +1633,10 @@ bool static ProcessMessage(CNode* pfrom, std::string strCommand, CDataStream& vR
 
 
     else if (strCommand == NetMsgType::MEMPOOL) {
-        LOCK2(cs_main, pfrom->cs_filter);
 
-        std::vector<uint256> vtxid;
-        mempool.queryHashes(vtxid);
-        std::vector<CInv> vInv;
-        for (uint256& hash : vtxid) {
-            CInv inv(MSG_TX, hash);
-            if (pfrom->pfilter) {
-                CTransaction tx;
-                bool fInMemPool = mempool.lookup(hash, tx);
-                if (!fInMemPool) continue; // another thread removed since queryHashes, maybe...
-                if (!pfrom->pfilter->IsRelevantAndUpdate(tx)) continue;
-            }
-            vInv.emplace_back(inv);
-            if (vInv.size() == MAX_INV_SZ) {
-                connman.PushMessage(pfrom, msgMaker.Make(NetMsgType::INV, vInv));
-                vInv.clear();
-            }
-        }
-        if (vInv.size() > 0)
-            connman.PushMessage(pfrom, msgMaker.Make(NetMsgType::INV, vInv));
+        // todo: limit mempool request with a bandwidth limit
+        LOCK(pfrom->cs_inventory);
+        pfrom->fSendMempool = true;
     }
 
 
@@ -2104,13 +2087,42 @@ bool SendMessages(CNode* pto, CConnman& connman, std::atomic<bool>& interruptMsg
             }
             pto->vInventoryTierTwoToSend.clear();
 
-            // Determine transactions to relay
+            // Check whether periodic send should happen
             bool fSendTrickle = pto->fWhitelisted;
             if (pto->nNextInvSend < nNow) {
                 fSendTrickle = true;
                 // Use half the delay for outbound peers, as there is less privacy concern for them.
                 pto->nNextInvSend = PoissonNextSend(nNow, INVENTORY_BROADCAST_INTERVAL >> !pto->fInbound);
             }
+
+            // Respond to BIP35 mempool requests
+            if (fSendTrickle && pto->fSendMempool) {
+                std::vector<uint256> vtxid;
+                mempool.queryHashes(vtxid);
+                pto->fSendMempool = false;
+                // future: back port fee filter rate
+                LOCK(pto->cs_filter);
+
+                for (const uint256& hash : vtxid) {
+                    CInv inv(MSG_TX, hash);
+                    pto->setInventoryTxToSend.erase(hash);
+                    // future: add fee filter check here..
+                    if (pto->pfilter) {
+                        CTransaction tx;
+                        bool fInMemPool = mempool.lookup(hash, tx);
+                        if (!fInMemPool) continue; // another thread removed since queryHashes, maybe...
+                        if (!pto->pfilter->IsRelevantAndUpdate(tx)) continue;
+                    }
+                    pto->filterInventoryKnown.insert(hash);
+                    vInv.emplace_back(inv);
+                    if (vInv.size() == MAX_INV_SZ) {
+                        connman.PushMessage(pto, msgMaker.Make(NetMsgType::INV, vInv));
+                        vInv.clear();
+                    }
+                }
+            }
+
+            // Determine transactions to relay
             if (fSendTrickle) {
                 // Produce a vector with all candidates for sending
                 std::vector<std::set<uint256>::iterator> vInvTx;
@@ -2140,6 +2152,10 @@ bool SendMessages(CNode* pto, CConnman& connman, std::atomic<bool>& interruptMsg
                     // Send
                     vInv.emplace_back(CInv(MSG_TX, hash));
                     nRelayedTransactions++;
+                    if (vInv.size() == MAX_INV_SZ) {
+                        connman.PushMessage(pto, msgMaker.Make(NetMsgType::INV, vInv));
+                        vInv.clear();
+                    }
                     pto->filterInventoryKnown.insert(hash);
                 }
             }
