From 3b8343af379c3bc9212c562a49bc1d1add12c060 Mon Sep 17 00:00:00 2001
From: xqzr <34030394+xqzr@users.noreply.github.com>
Date: Tue, 1 Apr 2025 01:38:27 +0800
Subject: [PATCH] Sockopt: Add Windows `TCP_MAXSEG`

#2002
---
 transport/internet/sockopt_windows.go | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/transport/internet/sockopt_windows.go b/transport/internet/sockopt_windows.go
index cbd3b41e..ecae807a 100644
--- a/transport/internet/sockopt_windows.go
+++ b/transport/internet/sockopt_windows.go
@@ -16,6 +16,7 @@ const (
 	IP_MULTICAST_IF = 9
 	IPV6_MULTICAST_IF = 9
 	IPV6_V6ONLY = 27
+	TCP_MAXSEG = 4
 )
 
 func setTFO(fd syscall.Handle, tfo int) error {
@@ -70,6 +71,11 @@ func applyOutboundSocketOptions(network string, address string, fd uintptr, conf
 				return errors.New("failed to unset SO_KEEPALIVE", err)
 			}
 		}
+		if config.TcpMaxSeg > 0 {
+			if err := syscall.SetsockoptInt(syscall.Handle(fd), syscall.IPPROTO_TCP, syscall.TCP_MAXSEG, int(config.TcpMaxSeg)); err != nil {
+				return errors.New("failed to set TCP_MAXSEG", err)
+			}
+		}
 	}
 
 	return nil
@@ -89,6 +95,11 @@ func applyInboundSocketOptions(network string, fd uintptr, config *SocketConfig)
 				return errors.New("failed to unset SO_KEEPALIVE", err)
 			}
 		}
+		if config.TcpMaxSeg > 0 {
+			if err := syscall.SetsockoptInt(syscall.Handle(fd), syscall.IPPROTO_TCP, syscall.TCP_MAXSEG, int(config.TcpMaxSeg)); err != nil {
+				return errors.New("failed to set TCP_MAXSEG", err)
+			}
+		}
 	}
 
 	if config.V6Only {