From 16b0e12385f4c67d4f69f275c9ab38d6a64f5345 Mon Sep 17 00:00:00 2001
From: Gregory Maxwell <greg@xiph.org>
Date: Fri, 20 May 2016 16:19:26 +0000
Subject: [PATCH] Do not use mempool for GETDATA for tx accepted after the last
 mempoolreq

---
 src/main.cpp      | 11 ++++++-----
 src/net.cpp       |  1 +
 src/net.h         |  3 +++
 src/txmempool.cpp | 10 +++++++++-
 src/txmempool.h   |  1 +
 5 files changed, 20 insertions(+), 6 deletions(-)

diff --git a/src/main.cpp b/src/main.cpp
index b42d7e039..257e77977 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -4899,11 +4899,11 @@ void static ProcessGetData(CNode* pfrom, const Consensus::Params& consensusParam
                 }
                 if (!pushed && inv.type == MSG_TX) {
                     CTransaction tx;
-                    if (mempool.lookup(inv.hash, tx)) {
-                        CDataStream ss(SER_NETWORK, PROTOCOL_VERSION);
-                        ss.reserve(1000);
-                        ss << tx;
-                        pfrom->PushMessage(NetMsgType::TX, ss);
+                    int64_t txtime;
+                    // To protect privacy, do not answer getdata using the mempool when
+                    // that TX couldn't have been INVed in reply to a MEMPOOL request.
+                    if (mempool.lookup(inv.hash, tx, txtime) && txtime <= pfrom->timeLastMempoolReq) {
+                        pfrom->PushMessage(NetMsgType::TX, tx);
                         pushed = true;
                     }
                 }
@@ -6581,6 +6581,7 @@ bool SendMessages(CNode* pto)
                         vInv.clear();
                     }
                 }
+                pto->timeLastMempoolReq = GetTime();
             }
 
             // Determine transactions to relay
diff --git a/src/net.cpp b/src/net.cpp
index 3d0e0bbbe..3c8a21a83 100644
--- a/src/net.cpp
+++ b/src/net.cpp
@@ -2364,6 +2364,7 @@ CNode::CNode(SOCKET hSocketIn, const CAddress& addrIn, const std::string& addrNa
     nNextInvSend = 0;
     fRelayTxes = false;
     pfilter = new CBloomFilter();
+    timeLastMempoolReq = 0;
     nPingNonceSent = 0;
     nPingUsecStart = 0;
     nPingUsecTime = 0;
diff --git a/src/net.h b/src/net.h
index 4c7fa0d3f..cf96516d9 100644
--- a/src/net.h
+++ b/src/net.h
@@ -17,6 +17,7 @@
 #include "sync.h"
 #include "uint256.h"
 
+#include <atomic>
 #include <deque>
 #include <stdint.h>
 
@@ -409,6 +410,8 @@ public:
     // Used for BIP35 mempool sending, also protected by cs_inventory
     bool fSendMempool;
 
+    // Last time a "MEMPOOL" request was serviced.
+    std::atomic<int64_t> timeLastMempoolReq;
     // Ping time measurement:
     // The pong reply we're expecting, or 0 if no pong expected.
     uint64_t nPingNonceSent;
diff --git a/src/txmempool.cpp b/src/txmempool.cpp
index 0e5e28648..9a0f78279 100644
--- a/src/txmempool.cpp
+++ b/src/txmempool.cpp
@@ -801,15 +801,23 @@ void CTxMemPool::queryHashes(vector<uint256>& vtxid)
     std::sort(vtxid.begin(), vtxid.end(), DepthAndScoreComparator(this));
 }
 
-bool CTxMemPool::lookup(uint256 hash, CTransaction& result) const
+
+bool CTxMemPool::lookup(uint256 hash, CTransaction& result, int64_t& time) const
 {
     LOCK(cs);
     indexed_transaction_set::const_iterator i = mapTx.find(hash);
     if (i == mapTx.end()) return false;
     result = i->GetTx();
+    time = i->GetTime();
     return true;
 }
 
+bool CTxMemPool::lookup(uint256 hash, CTransaction& result) const
+{
+    int64_t time;
+    return CTxMemPool::lookup(hash, result, time);
+}
+
 bool CTxMemPool::lookupFeeRate(const uint256& hash, CFeeRate& feeRate) const
 {
     LOCK(cs);
diff --git a/src/txmempool.h b/src/txmempool.h
index 521c9cf7c..53a0887fd 100644
--- a/src/txmempool.h
+++ b/src/txmempool.h
@@ -597,6 +597,7 @@ public:
     }
 
     bool lookup(uint256 hash, CTransaction& result) const;
+    bool lookup(uint256 hash, CTransaction& result, int64_t& time) const;
     bool lookupFeeRate(const uint256& hash, CFeeRate& feeRate) const;
 
     /** Estimate fee rate needed to get into the next nBlocks