partial bitcoin#26396: Avoid SetTxRelay for feeler connections

excludes:
- fa24239a (changes to `p2p_sendtxrcncl.py`)

src/net.h

@@ -929,10 +929,8 @@ public:
     /** Whether this peer provides all services that we want. Used for eviction decisions */
     std::atomic_bool m_has_all_wanted_services{false};
 
-    /** Whether we should relay transactions to this peer (their version
-     *  message did not include fRelay=false and this is not a block-relay-only
-     *  connection). This only changes from false to true. It will never change
-     *  back to false. Used only in inbound eviction logic. */
+    /** Whether we should relay transactions to this peer. This only changes
+     * from false to true. It will never change back to false. */
     std::atomic_bool m_relays_txs{false};
 
     /** Whether this peer has loaded a bloom filter. Used only in inbound

src/net_processing.cpp

@@ -399,9 +399,7 @@ private:
     Mutex m_tx_relay_mutex;
 
     /** Transaction relay data.
-     * (Bitcoin) Will be a nullptr if we're not relaying transactions with this peer
-     *           (e.g. if it's a block-relay-only peer). Users should access this with
-     *           the GetTxRelay() getter.
+     * (Bitcoin) Transaction relay data. May be a nullptr.
      * (Dash)    Always initialized but selectively available through GetTxRelay()
      *           (non-transaction relay should use GetInvRelay(), which will provide
      *           unconditional access) */
@@ -3523,9 +3521,11 @@ void PeerManagerImpl::ProcessMessage(
 
         // We only initialize the m_tx_relay data structure if:
         // - this isn't an outbound block-relay-only connection; and
+        // - this isn't an outbound feeler connection, and
         // - fRelay=true or we're offering NODE_BLOOM to this peer
         //   (NODE_BLOOM means that the peer may turn on tx relay later)
         if (!pfrom.IsBlockOnlyConn() &&
+            !pfrom.IsFeelerConn() &&
             (fRelay || (peer->m_our_services & NODE_BLOOM))) {
             auto* const tx_relay = peer->SetTxRelay();
             {