Add interface address rule items

common/srs/ip_cidr.go

@@ -0,0 +1,33 @@
+package srs
+
+import (
+	"encoding/binary"
+	"net/netip"
+
+	M "github.com/sagernet/sing/common/metadata"
+	"github.com/sagernet/sing/common/varbin"
+)
+
+func readPrefix(reader varbin.Reader) (netip.Prefix, error) {
+	addrSlice, err := varbin.ReadValue[[]byte](reader, binary.BigEndian)
+	if err != nil {
+		return netip.Prefix{}, err
+	}
+	prefixBits, err := varbin.ReadValue[uint8](reader, binary.BigEndian)
+	if err != nil {
+		return netip.Prefix{}, err
+	}
+	return netip.PrefixFrom(M.AddrFromIP(addrSlice), int(prefixBits)), nil
+}
+
+func writePrefix(writer varbin.Writer, prefix netip.Prefix) error {
+	err := varbin.Write(writer, binary.BigEndian, prefix.Addr().AsSlice())
+	if err != nil {
+		return err
+	}
+	err = binary.Write(writer, binary.BigEndian, uint8(prefix.Bits()))
+	if err != nil {
+		return err
+	}
+	return nil
+}