Continue relaying transactions after they expire from mapRelay

Author: ajtowns

src/net_processing.cpp

@@ -39,6 +39,8 @@
 static constexpr int64_t ORPHAN_TX_EXPIRE_TIME = 20 * 60;
 /** Minimum time between orphan transactions expire time checks in seconds */
 static constexpr int64_t ORPHAN_TX_EXPIRE_INTERVAL = 5 * 60;
+/** How long to cache transactions in mapRelay for normal relay */
+static constexpr std::chrono::seconds RELAY_TX_CACHE_TIME{15 * 60};
 /** Headers download timeout expressed in microseconds
  *  Timeout = base + per_header * (expected number of headers) */
 static constexpr int64_t HEADERS_DOWNLOAD_TIMEOUT_BASE = 15 * 60 * 1000000; // 15 minutes
@@ -1522,6 +1524,10 @@ void static ProcessGetData(CNode* pfrom, const CChainParams& chainparams, CConnm
     // messages from this peer (likely resulting in our peer eventually
     // disconnecting us).
     if (pfrom->m_tx_relay != nullptr) {
+        // mempool entries added before this time have likely expired from mapRelay
+        const std::chrono::seconds longlived_mempool_time = GetTime<std::chrono::seconds>() - RELAY_TX_CACHE_TIME;
+        const std::chrono::seconds mempool_req = pfrom->m_tx_relay->m_last_mempool_req.load();
+
         LOCK(cs_main);
 
         while (it != pfrom->vRecvGetData.end() && (it->type == MSG_TX || it->type == MSG_WITNESS_TX)) {
@@ -1541,11 +1547,15 @@ void static ProcessGetData(CNode* pfrom, const CChainParams& chainparams, CConnm
             if (mi != mapRelay.end()) {
                 connman->PushMessage(pfrom, msgMaker.Make(nSendFlags, NetMsgType::TX, *mi->second));
                 push = true;
-            } else if (pfrom->m_tx_relay->m_last_mempool_req.load().count()) {
+            } else {
                 auto txinfo = mempool.info(inv.hash);
                 // 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 (txinfo.tx && txinfo.m_time <= pfrom->m_tx_relay->m_last_mempool_req.load()) {
+                // that TX couldn't have been INVed in reply to a MEMPOOL request,
+                // or when it's too recent to have expired from mapRelay.
+                if (txinfo.tx && (
+                     (mempool_req.count() && txinfo.m_time <= mempool_req)
+                      || (txinfo.m_time <= longlived_mempool_time)))
+                {
                     connman->PushMessage(pfrom, msgMaker.Make(nSendFlags, NetMsgType::TX, *txinfo.tx));
                     push = true;
                 }
@@ -3931,7 +3941,7 @@ bool PeerLogicValidation::SendMessages(CNode* pto)
 
                             auto ret = mapRelay.insert(std::make_pair(hash, std::move(txinfo.tx)));
                             if (ret.second) {
-                                vRelayExpiration.push_back(std::make_pair(nNow + 15 * 60 * 1000000, ret.first));
+                                vRelayExpiration.push_back(std::make_pair(nNow + std::chrono::microseconds{RELAY_TX_CACHE_TIME}.count(), ret.first));
                             }
                         }
                         if (vInv.size() == MAX_INV_SZ) {