From 4cdb789918656f98bf1b2278fef840022f3c49d6 Mon Sep 17 00:00:00 2001
From: gVisor bot <gvisor-bot@google.com>
Date: Thu, 21 Sep 2023 23:49:45 +0800
Subject: [PATCH] chore: limit tuicv5's maxUdpRelayPacketSize up to
 1200-PacketOverHead

---
 adapter/outbound/tuic.go  | 6 +++++-
 transport/tuic/server.go  | 4 ++++
 transport/tuic/tuic.go    | 1 +
 transport/tuic/v5/frag.go | 5 +++++
 4 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/adapter/outbound/tuic.go b/adapter/outbound/tuic.go
index 4d826912..b1032e8c 100644
--- a/adapter/outbound/tuic.go
+++ b/adapter/outbound/tuic.go
@@ -323,6 +323,10 @@ func NewTuic(option TuicOption) (*Tuic, error) {
 
 		t.client = tuic.NewPoolClientV4(clientOption)
 	} else {
+		maxUdpRelayPacketSize := option.MaxUdpRelayPacketSize
+		if maxUdpRelayPacketSize > tuic.MaxFragSizeV5 {
+			maxUdpRelayPacketSize = tuic.MaxFragSizeV5
+		}
 		clientOption := &tuic.ClientOptionV5{
 			TlsConfig:             tlsConfig,
 			QuicConfig:            quicConfig,
@@ -331,7 +335,7 @@ func NewTuic(option TuicOption) (*Tuic, error) {
 			UdpRelayMode:          udpRelayMode,
 			CongestionController:  option.CongestionController,
 			ReduceRtt:             option.ReduceRtt,
-			MaxUdpRelayPacketSize: option.MaxUdpRelayPacketSize,
+			MaxUdpRelayPacketSize: maxUdpRelayPacketSize,
 			MaxOpenStreams:        clientMaxOpenStreams,
 			CWND:                  option.CWND,
 		}
diff --git a/transport/tuic/server.go b/transport/tuic/server.go
index a6f91b88..cabc04e0 100644
--- a/transport/tuic/server.go
+++ b/transport/tuic/server.go
@@ -223,6 +223,10 @@ func NewServer(option *ServerOption, pc net.PacketConn) (*Server, error) {
 		}
 	}
 	if len(option.Users) > 0 {
+		maxUdpRelayPacketSize := option.MaxUdpRelayPacketSize
+		if maxUdpRelayPacketSize > MaxFragSizeV5 {
+			maxUdpRelayPacketSize = MaxFragSizeV5
+		}
 		server.optionV5 = &v5.ServerOption{
 			HandleTcpFn:           option.HandleTcpFn,
 			HandleUdpFn:           option.HandleUdpFn,
diff --git a/transport/tuic/tuic.go b/transport/tuic/tuic.go
index 8832ef91..387a152c 100644
--- a/transport/tuic/tuic.go
+++ b/transport/tuic/tuic.go
@@ -30,6 +30,7 @@ const DefaultConnectionReceiveWindow = common.DefaultConnectionReceiveWindow
 var GenTKN = v4.GenTKN
 var PacketOverHeadV4 = v4.PacketOverHead
 var PacketOverHeadV5 = v5.PacketOverHead
+var MaxFragSizeV5 = v5.MaxFragSize
 
 type UdpRelayMode = common.UdpRelayMode
 
diff --git a/transport/tuic/v5/frag.go b/transport/tuic/v5/frag.go
index ae9dbf10..8df9f785 100644
--- a/transport/tuic/v5/frag.go
+++ b/transport/tuic/v5/frag.go
@@ -9,6 +9,11 @@ import (
 	"github.com/metacubex/quic-go"
 )
 
+// MaxFragSize is a safe udp relay packet size
+// because tuicv5 support udp fragment so we unneeded to do a magic modify for quic-go to increase MaxDatagramFrameSize
+// it may not work fine in some platform
+var MaxFragSize = 1200 - PacketOverHead
+
 func fragWriteNative(quicConn quic.Connection, packet Packet, buf *bytes.Buffer, fragSize int) (err error) {
 	fullPayload := packet.DATA
 	off := 0