🪚 service: add option to allow IP fragmentation

database64128 · Dec 3, 2024 · cb963b3 · cb963b3
1 parent 7e18187
commit cb963b3
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Showing 3 changed files with 31 additions and 6 deletions.
diff --git a/docs/config.json b/docs/config.json
@@ -109,7 +109,8 @@
                     "relayBatchSize": 0,
                     "serverRecvBatchSize": 0,
                     "sendChannelCapacity": 0,
-                    "natTimeout": "180s"
+                    "natTimeout": "180s",
+                    "allowFragmentation": false
                 },
                 {
                     "network": "udp4",
@@ -121,7 +122,8 @@
                     "relayBatchSize": 0,
                     "serverRecvBatchSize": 0,
                     "sendChannelCapacity": 0,
-                    "natTimeout": "180s"
+                    "natTimeout": "180s",
+                    "allowFragmentation": false
                 },
                 {
                     "network": "udp6",
@@ -133,7 +135,8 @@
                     "relayBatchSize": 0,
                     "serverRecvBatchSize": 0,
                     "sendChannelCapacity": 0,
-                    "natTimeout": "180s"
+                    "natTimeout": "180s",
+                    "allowFragmentation": false
                 }
             ],
             "mtu": 1500
@@ -287,6 +290,7 @@
             "multipathTCP": false,
             "allowSegmentedFixedLengthHeader": false,
             "enableUDP": true,
+            "allowFragmentation": false,
             "mtu": 1500,
             "psk": "oE/s2z9Q8EWORAB8B3UCxw==",
             "iPSKs": [
@@ -308,6 +312,7 @@
             "multipathTCP": false,
             "allowSegmentedFixedLengthHeader": false,
             "enableUDP": true,
+            "allowFragmentation": false,
             "mtu": 1500,
             "psk": "QzhDwx0lKZ+0Sustgwtjtw==",
             "iPSKs": [
@@ -325,6 +330,7 @@
             "enableTCP": true,
             "multipathTCP": false,
             "enableUDP": true,
+            "allowFragmentation": false,
             "mtu": 1500,
             "socks5": {
                 "username": "username",
@@ -364,6 +370,7 @@
             "tcpFastOpenFallback": false,
             "multipathTCP": false,
             "enableUDP": true,
+            "allowFragmentation": false,
             "mtu": 1500
         },
         {
@@ -377,6 +384,7 @@
             "tcpFastOpenFallback": false,
             "multipathTCP": false,
             "enableUDP": true,
+            "allowFragmentation": false,
             "mtu": 1500
         },
         {
@@ -390,6 +398,7 @@
             "tcpFastOpenFallback": false,
             "multipathTCP": false,
             "enableUDP": true,
+            "allowFragmentation": false,
             "mtu": 1500
         }
     ],

diff --git a/service/client.go b/service/client.go
@@ -89,7 +89,16 @@ type ClientConfig struct {
 	// UDP
 
 	EnableUDP bool `json:"enableUDP"`
-	MTU       int  `json:"mtu"`
+
+	// AllowFragmentation controls whether to allow fragmented UDP packets.
+	//
+	// IP fragmentation does not reliably work over the Internet.
+	// Sending fragmented packets will significantly reduce throughput.
+	// Do not enable this option unless it is absolutely necessary.
+	AllowFragmentation bool `json:"allowFragmentation"`
+
+	// MTU is the MTU of the client's designated network path.
+	MTU int `json:"mtu"`
 
 	// Socks5 is the protocol-specific configuration for "socks5".
 	Socks5 Socks5ClientConfig `json:"socks5"`
@@ -308,7 +317,7 @@ func (cc *ClientConfig) UDPClient() (zerocopy.UDPClient, error) {
 		ReceiveBufferSize: conn.DefaultUDPSocketBufferSize,
 		Fwmark:            cc.DialerFwmark,
 		TrafficClass:      cc.DialerTrafficClass,
-		PathMTUDiscovery:  true,
+		PathMTUDiscovery:  !cc.AllowFragmentation,
 	})
 
 	switch cc.Protocol {

diff --git a/service/server.go b/service/server.go
@@ -165,6 +165,13 @@ type UDPListenerConfig struct {
 	//
 	// The default value is 5 minutes.
 	NATTimeout jsonhelper.Duration `json:"natTimeout"`
+
+	// AllowFragmentation controls whether to allow IP fragmentation.
+	//
+	// IP fragmentation does not reliably work over the Internet.
+	// Sending fragmented packets will significantly reduce throughput.
+	// Do not enable this option unless it is absolutely necessary.
+	AllowFragmentation bool `json:"allowFragmentation"`
 }
 
 // Configure returns a UDP server socket configuration.
@@ -196,7 +203,7 @@ func (lnc *UDPListenerConfig) Configure(listenConfigCache conn.ListenConfigCache
 			TrafficClass:      lnc.TrafficClass,
 			ReusePort:         lnc.ReusePort,
 			Transparent:       transparent,
-			PathMTUDiscovery:  true,
+			PathMTUDiscovery:  !lnc.AllowFragmentation,
 			ReceivePacketInfo: true,
 		}),
 		network:             lnc.Network,