Improve interface finder

common/control/bind_finder.go

@@ -1,30 +1,18 @@
 package control
 
-import "net"
+import (
+	"net/netip"
+)
 
 type InterfaceFinder interface {
 	InterfaceIndexByName(name string) (int, error)
 	InterfaceNameByIndex(index int) (string, error)
+	InterfaceByAddr(addr netip.Addr) (*Interface, error)
 }
 
-func DefaultInterfaceFinder() InterfaceFinder {
-	return (*netInterfaceFinder)(nil)
-}
-
-type netInterfaceFinder struct{}
-
-func (w *netInterfaceFinder) InterfaceIndexByName(name string) (int, error) {
-	netInterface, err := net.InterfaceByName(name)
-	if err != nil {
-		return 0, err
-	}
-	return netInterface.Index, nil
-}
-
-func (w *netInterfaceFinder) InterfaceNameByIndex(index int) (string, error) {
-	netInterface, err := net.InterfaceByIndex(index)
-	if err != nil {
-		return "", err
-	}
-	return netInterface.Name, nil
+type Interface struct {
+	Index     int
+	MTU       int
+	Name      string
+	Addresses []netip.Prefix
 }

common/control/bind_finder_default.go

@@ -0,0 +1,97 @@
+package control
+
+import (
+	"net"
+	"net/netip"
+	_ "unsafe"
+
+	"github.com/sagernet/sing/common"
+	M "github.com/sagernet/sing/common/metadata"
+)
+
+type DefaultInterfaceFinder struct {
+	interfaces []Interface
+}
+
+func NewDefaultInterfaceFinder() *DefaultInterfaceFinder {
+	return &DefaultInterfaceFinder{}
+}
+
+func (f *DefaultInterfaceFinder) Update() error {
+	netIfs, err := net.Interfaces()
+	if err != nil {
+		return err
+	}
+	interfaces := make([]Interface, 0, len(netIfs))
+	for _, netIf := range netIfs {
+		ifAddrs, err := netIf.Addrs()
+		if err != nil {
+			return err
+		}
+		interfaces = append(interfaces, Interface{
+			Index:     netIf.Index,
+			MTU:       netIf.MTU,
+			Name:      netIf.Name,
+			Addresses: common.Map(ifAddrs, M.PrefixFromNet),
+		})
+	}
+	f.interfaces = interfaces
+	return nil
+}
+
+func (f *DefaultInterfaceFinder) UpdateInterfaces(interfaces []Interface) {
+	f.interfaces = interfaces
+}
+
+func (f *DefaultInterfaceFinder) InterfaceIndexByName(name string) (int, error) {
+	for _, netInterface := range f.interfaces {
+		if netInterface.Name == name {
+			return netInterface.Index, nil
+		}
+	}
+	netInterface, err := net.InterfaceByName(name)
+	if err != nil {
+		return 0, err
+	}
+	f.Update()
+	return netInterface.Index, nil
+}
+
+func (f *DefaultInterfaceFinder) InterfaceNameByIndex(index int) (string, error) {
+	for _, netInterface := range f.interfaces {
+		if netInterface.Index == index {
+			return netInterface.Name, nil
+		}
+	}
+	netInterface, err := net.InterfaceByIndex(index)
+	if err != nil {
+		return "", err
+	}
+	f.Update()
+	return netInterface.Name, nil
+}
+
+//go:linkname errNoSuchInterface net.errNoSuchInterface
+var errNoSuchInterface error
+
+func (f *DefaultInterfaceFinder) InterfaceByAddr(addr netip.Addr) (*Interface, error) {
+	for _, netInterface := range f.interfaces {
+		for _, prefix := range netInterface.Addresses {
+			if prefix.Contains(addr) {
+				return &netInterface, nil
+			}
+		}
+	}
+	err := f.Update()
+	if err != nil {
+		return nil, err
+	}
+	for _, netInterface := range f.interfaces {
+		for _, prefix := range netInterface.Addresses {
+			if prefix.Contains(addr) {
+				return &netInterface, nil
+			}
+		}
+	}
+	return nil, &net.OpError{Op: "route", Net: "ip+net", Source: nil, Addr: &net.IPAddr{IP: addr.AsSlice()}, Err: errNoSuchInterface}
+}

common/metadata/addr.go

@@ -141,7 +141,7 @@ func SocksaddrFromNet(ap net.Addr) Socksaddr {
 	return ParseSocksaddr(ap.String())
 }
 
-func AddrFromNetAddr(netAddr net.Addr) netip.Addr {
+func AddrFromNet(netAddr net.Addr) netip.Addr {
 	if addr := AddrPortFromNet(netAddr); addr.Addr().IsValid() {
 		return addr.Addr()
 	}
@@ -157,6 +157,16 @@ func AddrFromNetAddr(netAddr net.Addr) netip.Addr {
 	}
 }
 
+func PrefixFromNet(netAddr net.Addr) netip.Prefix {
+	switch addr := netAddr.(type) {
+	case *net.IPNet:
+		bits, _ := addr.Mask.Size()
+		return netip.PrefixFrom(AddrFromIP(addr.IP), bits)
+	default:
+		return netip.Prefix{}
+	}
+}
+
 func AddrPortFromNet(netAddr net.Addr) netip.AddrPort {
 	var ip net.IP
 	var port uint16

common/network/addr.go

@@ -13,7 +13,7 @@ func LocalAddrs() ([]netip.Addr, error) {
 	if err != nil {
 		return nil, err
 	}
-	return common.Map(interfaceAddrs, M.AddrFromNetAddr), nil
+	return common.Map(interfaceAddrs, M.AddrFromNet), nil
 }
 
 func IsPublicAddr(addr netip.Addr) bool {

protocol/socks/handshake.go

@@ -203,7 +203,7 @@ func HandleConnection0(ctx context.Context, conn net.Conn, version byte, authent
 			return handler.NewConnection(ctx, conn, metadata)
 		case socks5.CommandUDPAssociate:
 			var udpConn *net.UDPConn
-			udpConn, err = net.ListenUDP(M.NetworkFromNetAddr("udp", M.AddrFromNetAddr(conn.LocalAddr())), net.UDPAddrFromAddrPort(netip.AddrPortFrom(M.AddrFromNetAddr(conn.LocalAddr()), 0)))
+			udpConn, err = net.ListenUDP(M.NetworkFromNetAddr("udp", M.AddrFromNet(conn.LocalAddr())), net.UDPAddrFromAddrPort(netip.AddrPortFrom(M.AddrFromNet(conn.LocalAddr()), 0)))
 			if err != nil {
 				return err
 			}