Add auto_route and auto_detect_interface for linux

common/dialer/auto_linux.go

@@ -0,0 +1,23 @@
+package dialer
+
+import (
+	"syscall"
+
+	"github.com/sagernet/sing-box/adapter"
+	"github.com/sagernet/sing/common/control"
+	E "github.com/sagernet/sing/common/exceptions"
+)
+
+func BindToInterface(router adapter.Router) control.Func {
+	return func(network, address string, conn syscall.RawConn) error {
+		interfaceName := router.DefaultInterfaceName()
+		if interfaceName == "" {
+			return nil
+		}
+		var innerErr error
+		err := conn.Control(func(fd uintptr) {
+			innerErr = syscall.BindToDevice(int(fd), interfaceName)
+		})
+		return E.Errors(innerErr, err)
+	}
+}

common/dialer/auto_other.go

@@ -0,0 +1,12 @@
+//go:build !linux
+
+package dialer
+
+import (
+	"github.com/sagernet/sing-box/adapter"
+	"github.com/sagernet/sing/common/control"
+)
+
+func BindToInterface(router adapter.Router) control.Func {
+	return nil
+}

common/dialer/default.go

@@ -5,6 +5,7 @@ import (
 	"net"
 	"time"
 
+	"github.com/sagernet/sing-box/adapter"
 	C "github.com/sagernet/sing-box/constant"
 	"github.com/sagernet/sing-box/option"
 	"github.com/sagernet/sing/common/control"
@@ -18,12 +19,15 @@ type DefaultDialer struct {
 	net.ListenConfig
 }
 
-func NewDefault(options option.DialerOptions) *DefaultDialer {
+func NewDefault(router adapter.Router, options option.DialerOptions) *DefaultDialer {
 	var dialer net.Dialer
 	var listener net.ListenConfig
 	if options.BindInterface != "" {
 		dialer.Control = control.Append(dialer.Control, control.BindToInterface(options.BindInterface))
 		listener.Control = control.Append(listener.Control, control.BindToInterface(options.BindInterface))
+	} else if router.AutoDetectInterface() {
+		dialer.Control = BindToInterface(router)
+		listener.Control = BindToInterface(router)
 	}
 	if options.RoutingMark != 0 {
 		dialer.Control = control.Append(dialer.Control, control.RoutingMark(options.RoutingMark))

common/dialer/dialer.go

@@ -12,7 +12,7 @@ import (
 
 func New(router adapter.Router, options option.DialerOptions) N.Dialer {
 	if options.Detour == "" {
-		return NewDefault(options)
+		return NewDefault(router, options)
 	} else {
 		return NewDetour(router, options.Detour)
 	}