From 900b64403d097ac7260fa18cff1ec718ec2b39c7 Mon Sep 17 00:00:00 2001
From: James Tucker <james@tailscale.com>
Date: Tue, 21 Jan 2025 13:17:21 -0800
Subject: [PATCH] cmd/natc: send TCP keepalives to upstreams

Idle connections may silently close, detect those closures with TCP
keeliave.

Updates tailscale/corp#25169

Signed-off-by: James Tucker <james@tailscale.com>
---
 cmd/natc/natc.go | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/cmd/natc/natc.go b/cmd/natc/natc.go
index d94523c6e..5df060f76 100644
--- a/cmd/natc/natc.go
+++ b/cmd/natc/natc.go
@@ -475,7 +475,8 @@ func proxyTCPConn(c net.Conn, dest string) {
 		},
 	}
 	p.AddRoute(addrPortStr, &tcpproxy.DialProxy{
-		Addr: fmt.Sprintf("%s:%s", dest, port),
+		Addr:            fmt.Sprintf("%s:%s", dest, port),
+		KeepAlivePeriod: time.Second,
 	})
 	p.Start()
 }