[net processing] Ensure transaction announcements are only queued for fully connected peers

Author: dergoegge

src/net_processing.cpp

@@ -295,7 +295,7 @@ struct Peer {
         std::atomic<std::chrono::seconds> m_last_mempool_req{0s};
         /** The next time after which we will send an `inv` message containing
          *  transaction announcements to this peer. */
-        std::chrono::microseconds m_next_inv_send_time GUARDED_BY(NetEventsInterface::g_msgproc_mutex){0};
+        std::chrono::microseconds m_next_inv_send_time GUARDED_BY(m_tx_inventory_mutex){0};
 
         /** Minimum fee rate with which to filter transaction announcements to this node. See BIP133. */
         std::atomic<CAmount> m_fee_filter_received{0};
@@ -2011,8 +2011,15 @@ void PeerManagerImpl::RelayTransaction(const uint256& txid, const uint256& wtxid
         auto tx_relay = peer.GetTxRelay();
         if (!tx_relay) continue;
 
-        const uint256& hash{peer.m_wtxid_relay ? wtxid : txid};
         LOCK(tx_relay->m_tx_inventory_mutex);
+        // Only queue transactions for announcement once the version handshake
+        // is completed. The time of arrival for these transactions is
+        // otherwise at risk of leaking to a spy, if the spy is able to
+        // distinguish transactions received during the handshake from the rest
+        // in the announcement.
+        if (tx_relay->m_next_inv_send_time == 0s) continue;
+
+        const uint256& hash{peer.m_wtxid_relay ? wtxid : txid};
         if (!tx_relay->m_tx_inventory_known_filter.contains(hash)) {
             tx_relay->m_tx_inventory_to_send.insert(hash);
         }