Add TCP MultiPath support

common/dialer/default.go

@@ -26,7 +26,7 @@ type DefaultDialer struct {
 	udpAddr6    string
 }
 
-func NewDefault(router adapter.Router, options option.DialerOptions) *DefaultDialer {
+func NewDefault(router adapter.Router, options option.DialerOptions) (*DefaultDialer, error) {
 	var dialer net.Dialer
 	var listener net.ListenConfig
 	if options.BindInterface != "" {
@@ -93,6 +93,12 @@ func NewDefault(router adapter.Router, options option.DialerOptions) *DefaultDia
 		udpDialer6.LocalAddr = &net.UDPAddr{IP: bindAddr.AsSlice()}
 		udpAddr6 = M.SocksaddrFrom(bindAddr, 0).String()
 	}
+	if options.TCPMultiPath {
+		if !multipathTCPAvailable {
+			return nil, E.New("MultiPath TCP requires go1.21, please recompile your binary.")
+		}
+		setMultiPathTCP(&dialer4)
+	}
 	return &DefaultDialer{
 		tfo.Dialer{Dialer: dialer4, DisableTFO: !options.TCPFastOpen},
 		tfo.Dialer{Dialer: dialer6, DisableTFO: !options.TCPFastOpen},
@@ -101,7 +107,7 @@ func NewDefault(router adapter.Router, options option.DialerOptions) *DefaultDia
 		listener,
 		udpAddr4,
 		udpAddr6,
-	}
+	}, nil
 }
 
 func (d *DefaultDialer) DialContext(ctx context.Context, network string, address M.Socksaddr) (net.Conn, error) {

common/dialer/default_go1.21.go

@@ -0,0 +1,11 @@
+//go:build go1.21
+
+package dialer
+
+import "net"
+
+const multipathTCPAvailable = true
+
+func setMultiPathTCP(dialer *net.Dialer) {
+	dialer.SetMultipathTCP(true)
+}

common/dialer/default_nongo1.21.go

@@ -0,0 +1,12 @@
+//go:build !go1.21
+
+package dialer
+
+import (
+	"net"
+)
+
+const multipathTCPAvailable = false
+
+func setMultiPathTCP(dialer *net.Dialer) {
+}

common/dialer/dialer.go

@@ -6,13 +6,24 @@ import (
 	"github.com/sagernet/sing-box/adapter"
 	"github.com/sagernet/sing-box/option"
 	"github.com/sagernet/sing-dns"
+	"github.com/sagernet/sing/common"
 	N "github.com/sagernet/sing/common/network"
 )
 
-func New(router adapter.Router, options option.DialerOptions) N.Dialer {
-	var dialer N.Dialer
+func MustNew(router adapter.Router, options option.DialerOptions) N.Dialer {
+	return common.Must1(New(router, options))
+}
+
+func New(router adapter.Router, options option.DialerOptions) (N.Dialer, error) {
+	var (
+		dialer N.Dialer
+		err    error
+	)
 	if options.Detour == "" {
-		dialer = NewDefault(router, options)
+		dialer, err = NewDefault(router, options)
+		if err != nil {
+			return nil, err
+		}
 	} else {
 		dialer = NewDetour(router, options.Detour)
 	}
@@ -20,5 +31,5 @@ func New(router adapter.Router, options option.DialerOptions) N.Dialer {
 	if domainStrategy != dns.DomainStrategyAsIS || options.Detour == "" {
 		dialer = NewResolveDialer(router, dialer, domainStrategy, time.Duration(options.FallbackDelay))
 	}
-	return dialer
+	return dialer, nil
 }

common/tls/reality_server.go

@@ -101,7 +101,10 @@ func NewRealityServer(ctx context.Context, router adapter.Router, logger log.Log
 		tlsConfig.ShortIds[shortID] = true
 	}
 
-	handshakeDialer := dialer.New(router, options.Reality.Handshake.DialerOptions)
+	handshakeDialer, err := dialer.New(router, options.Reality.Handshake.DialerOptions)
+	if err != nil {
+		return nil, err
+	}
 	tlsConfig.DialContext = func(ctx context.Context, network, addr string) (net.Conn, error) {
 		return handshakeDialer.DialContext(ctx, network, M.ParseSocksaddr(addr))
 	}