Improve linux bind interface

common/control/bind_linux.go

@@ -1,13 +1,48 @@
 package control
 
 import (
+	"os"
 	"syscall"
 
+	"github.com/sagernet/sing/common/atomic"
+	E "github.com/sagernet/sing/common/exceptions"
+
 	"golang.org/x/sys/unix"
 )
 
-func bindToInterface(conn syscall.RawConn, network string, address string, interfaceName string, interfaceIndex int) error {
+var ifIndexDisabled atomic.Bool
+
+func bindToInterface(conn syscall.RawConn, network string, address string, finder InterfaceFinder, interfaceName string, interfaceIndex int) error {
 	return Raw(conn, func(fd uintptr) error {
+		var err error
+		if !ifIndexDisabled.Load() {
+			if interfaceIndex == -1 {
+				if finder == nil {
+					return os.ErrInvalid
+				}
+				interfaceIndex, err = finder.InterfaceIndexByName(interfaceName)
+				if err != nil {
+					return err
+				}
+			}
+			err = unix.SetsockoptInt(int(fd), unix.SOL_SOCKET, unix.SO_BINDTOIFINDEX, interfaceIndex)
+			if err == nil {
+				return nil
+			} else if E.IsMulti(err, unix.ENOPROTOOPT, unix.EINVAL) {
+				ifIndexDisabled.Store(true)
+			} else {
+				return err
+			}
+		}
+		if interfaceName == "" {
+			if finder == nil {
+				return os.ErrInvalid
+			}
+			interfaceName, err = finder.InterfaceNameByIndex(interfaceIndex)
+			if err != nil {
+				return err
+			}
+		}
 		return unix.BindToDevice(int(fd), interfaceName)
 	})
 }