Add fakeip support

adapter/fakeip_metadata.go

@@ -0,0 +1,50 @@
+package adapter
+
+import (
+	"bytes"
+	"encoding"
+	"encoding/binary"
+	"io"
+	"net/netip"
+
+	"github.com/sagernet/sing/common"
+)
+
+type FakeIPMetadata struct {
+	Inet4Range   netip.Prefix
+	Inet6Range   netip.Prefix
+	Inet4Current netip.Addr
+	Inet6Current netip.Addr
+}
+
+func (m *FakeIPMetadata) MarshalBinary() (data []byte, err error) {
+	var buffer bytes.Buffer
+	for _, marshaler := range []encoding.BinaryMarshaler{m.Inet4Range, m.Inet6Range, m.Inet4Current, m.Inet6Current} {
+		data, err = marshaler.MarshalBinary()
+		if err != nil {
+			return
+		}
+		common.Must(binary.Write(&buffer, binary.BigEndian, uint16(len(data))))
+		buffer.Write(data)
+	}
+	data = buffer.Bytes()
+	return
+}
+
+func (m *FakeIPMetadata) UnmarshalBinary(data []byte) error {
+	reader := bytes.NewReader(data)
+	for _, unmarshaler := range []encoding.BinaryUnmarshaler{&m.Inet4Range, &m.Inet6Range, &m.Inet4Current, &m.Inet6Current} {
+		var length uint16
+		common.Must(binary.Read(reader, binary.BigEndian, &length))
+		element := make([]byte, length)
+		_, err := io.ReadFull(reader, element)
+		if err != nil {
+			return err
+		}
+		err = unmarshaler.UnmarshalBinary(element)
+		if err != nil {
+			return err
+		}
+	}
+	return nil
+}