Improve linux bind interface

Author: nekohasekai

common/control/bind.go

@@ -1,10 +1,9 @@
 package control
 
 import (
-	"os"
-	"runtime"
 	"syscall"
 
+	E "github.com/sagernet/sing/common/exceptions"
 	M "github.com/sagernet/sing/common/metadata"
 	N "github.com/sagernet/sing/common/network"
 )
@@ -25,38 +24,12 @@ func BindToInterfaceFunc(finder InterfaceFinder, block func(network string, addr
 	}
 }
 
-const useInterfaceName = runtime.GOOS == "linux" || runtime.GOOS == "android"
-
 func BindToInterface0(finder InterfaceFinder, conn syscall.RawConn, network string, address string, interfaceName string, interfaceIndex int) error {
 	if interfaceName == "" && interfaceIndex == -1 {
-		return nil
+		return E.New("interface not found: ", interfaceName)
 	}
 	if addr := M.ParseSocksaddr(address).Addr; addr.IsValid() && N.IsVirtual(addr) {
 		return nil
 	}
-	if interfaceName != "" && useInterfaceName || interfaceIndex != -1 && !useInterfaceName {
-		return bindToInterface(conn, network, address, interfaceName, interfaceIndex)
-	}
-	if finder == nil {
-		return os.ErrInvalid
-	}
-	var err error
-	if useInterfaceName {
-		interfaceName, err = finder.InterfaceNameByIndex(interfaceIndex)
-	} else {
-		interfaceIndex, err = finder.InterfaceIndexByName(interfaceName)
-	}
-	if err != nil {
-		return err
-	}
-	if useInterfaceName {
-		if interfaceName == "" {
-			return nil
-		}
-	} else {
-		if interfaceIndex == -1 {
-			return nil
-		}
-	}
-	return bindToInterface(conn, network, address, interfaceName, interfaceIndex)
+	return bindToInterface(conn, network, address, finder, interfaceName, interfaceIndex)
 }

common/control/bind_darwin.go

@@ -1,16 +1,24 @@
 package control
 
 import (
+	"os"
 	"syscall"
 
 	"golang.org/x/sys/unix"
 )
 
-func bindToInterface(conn syscall.RawConn, network string, address string, interfaceName string, interfaceIndex int) error {
-	if interfaceIndex == -1 {
-		return nil
-	}
+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 interfaceIndex == -1 {
+			if finder == nil {
+				return os.ErrInvalid
+			}
+			interfaceIndex, err = finder.InterfaceIndexByName(interfaceName)
+			if err != nil {
+				return err
+			}
+		}
 		switch network {
 		case "tcp6", "udp6":
 			return unix.SetsockoptInt(int(fd), unix.IPPROTO_IPV6, unix.IPV6_BOUND_IF, interfaceIndex)

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)
 	})
 }

common/control/bind_windows.go

@@ -2,17 +2,28 @@ package control
 
 import (
 	"encoding/binary"
+	"os"
 	"syscall"
 	"unsafe"
 
 	M "github.com/sagernet/sing/common/metadata"
 )
 
-func bindToInterface(conn syscall.RawConn, network string, address string, interfaceName string, interfaceIndex int) error {
+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 interfaceIndex == -1 {
+			if finder == nil {
+				return os.ErrInvalid
+			}
+			interfaceIndex, err = finder.InterfaceIndexByName(interfaceName)
+			if err != nil {
+				return err
+			}
+		}
 		handle := syscall.Handle(fd)
 		if M.ParseSocksaddr(address).AddrString() == "" {
-			err := bind4(handle, interfaceIndex)
+			err = bind4(handle, interfaceIndex)
 			if err != nil {
 				return err
 			}