From e8410b230204077a8242d9b0ae48bd01c09be308 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?J=C4=99drzej=20Stuczy=C5=84ski?=
 <jedrzej.stuczynski@gmail.com>
Date: Fri, 5 Jun 2026 16:37:12 +0100
Subject: [PATCH] feat: disable Nagle's algorithm for LP between nym-nodes
 (#6857)

---
 .../src/node/lp/control/ingress/client_handler.rs    | 12 +++++++++++-
 nym-node/src/node/lp/control/ingress/listener.rs     |  8 ++++++++
 2 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/nym-node/src/node/lp/control/ingress/client_handler.rs b/nym-node/src/node/lp/control/ingress/client_handler.rs
index 1613795601..aad0ce88b8 100644
--- a/nym-node/src/node/lp/control/ingress/client_handler.rs
+++ b/nym-node/src/node/lp/control/ingress/client_handler.rs
@@ -404,7 +404,7 @@ where
         };
 
         // Connect to target gateway with timeout
-        let stream = match timeout(Duration::from_secs(5), S::connect(target_addr)).await {
+        let mut stream = match timeout(Duration::from_secs(5), S::connect(target_addr)).await {
             Ok(Ok(stream)) => stream,
             Ok(Err(e)) => {
                 inc!("lp_forward_failed");
@@ -422,6 +422,16 @@ where
             }
         };
 
+        // Disable Nagle's algorithm: the forward stream carries small request/response
+        // handshake packets, so we want them sent immediately rather than coalesced.
+        if let Err(e) = stream.set_no_delay(true) {
+            inc!("lp_forward_failed");
+            return Err(LpHandlerError::ConnectionFailure {
+                egress: target_addr,
+                reason: format!("failed to set TCP_NODELAY: {e}"),
+            });
+        }
+
         debug!("Opened persistent exit connection to {target_addr} for forwarding");
         self.exit_stream = Some((stream, target_addr));
 
diff --git a/nym-node/src/node/lp/control/ingress/listener.rs b/nym-node/src/node/lp/control/ingress/listener.rs
index 3d038abebe..15377a546f 100644
--- a/nym-node/src/node/lp/control/ingress/listener.rs
+++ b/nym-node/src/node/lp/control/ingress/listener.rs
@@ -171,6 +171,14 @@ impl LpControlListener {
     }
 
     fn handle_connection(&self, stream: tokio::net::TcpStream, remote_addr: SocketAddr) {
+        // Disable Nagle's algorithm on the accepted socket so our responses are flushed
+        // immediately rather than coalesced. This is the write side of every reply we send,
+        // including handshake replies forwarded back to an entry gateway. Non-fatal: a valid
+        // connection should still be served if the option can't be set.
+        if let Err(e) = stream.set_nodelay(true) {
+            warn!("failed to set TCP_NODELAY on accepted LP connection from {remote_addr}: {e}");
+        }
+
         if let Some(initiator_details) = self
             .nodes_handler_state
             .nodes