packet/mpls: Add method to convert the format of label

Signed-off-by: Shinpei Muraoka <shinpei.muraoka@gmail.com>
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>

ryu/lib/packet/mpls.py

@@ -14,11 +14,11 @@
 # limitations under the License.
 
 import struct
-import socket
+
+import six
+
 from . import packet_base
-from . import packet_utils
-from . import ipv4
-from . import ether_types as ether
+from ryu.lib import type_desc
 
 
 class mpls(packet_base.PacketBase):
@@ -60,6 +60,7 @@ class mpls(packet_base.PacketBase):
         label = label >> 12
         msg = cls(label, exp, bsb, ttl)
         if bsb:
+            from . import ipv4
             return msg, ipv4.ipv4, buf[msg._MIN_LEN:]
         else:
             return msg, mpls, buf[msg._MIN_LEN:]
@@ -67,3 +68,24 @@ class mpls(packet_base.PacketBase):
     def serialize(self, payload, prev):
         val = self.label << 12 | self.exp << 9 | self.bsb << 8 | self.ttl
         return struct.pack(mpls._PACK_STR, val)
+
+
+def label_from_bin(buf):
+    """
+    Converts binary representation label to integer.
+    :param buf: Binary representation of label.
+    :return: MPLS Label and BoS bit.
+    """
+
+    mpls_label = type_desc.Int3.to_user(six.binary_type(buf))
+    return mpls_label >> 4, mpls_label & 1
+
+
+def label_to_bin(mpls_label, is_bos=False):
+    """
+    Converts integer label to binary representation.
+    :param mpls_label: MPLS Label.
+    :param is_bos: BoS bit.
+    :return: Binary representation of label.
+    """
+    return type_desc.Int3.from_user(mpls_label << 4 | is_bos)

ryu/tests/unit/packet/test_mpls.py

@@ -18,7 +18,7 @@ import unittest
 import logging
 import inspect
 
-from nose.tools import *
+from nose.tools import eq_
 from ryu.lib.packet import mpls
 
 
@@ -56,3 +56,37 @@ class Test_mpls(unittest.TestCase):
         jsondict = self.mp.to_jsondict()
         mp = mpls.mpls.from_jsondict(jsondict['mpls'])
         eq_(str(self.mp), str(mp))
+
+    def test_label_from_bin_true(self):
+        mpls_label = 0xfffff
+        is_bos = True
+        buf = b'\xff\xff\xf1'
+        mpls_label_out, is_bos_out = mpls.label_from_bin(buf)
+
+        eq_(mpls_label, mpls_label_out)
+        eq_(is_bos, is_bos_out)
+
+    def test_label_from_bin_false(self):
+        mpls_label = 0xfffff
+        is_bos = False
+        buf = b'\xff\xff\xf0'
+        mpls_label_out, is_bos_out = mpls.label_from_bin(buf)
+
+        eq_(mpls_label, mpls_label_out)
+        eq_(is_bos, is_bos_out)
+
+    def test_label_to_bin_true(self):
+        mpls_label = 0xfffff
+        is_bos = True
+        label = b'\xff\xff\xf1'
+        label_out = mpls.label_to_bin(mpls_label, is_bos)
+
+        eq_(label, label_out)
+
+    def test_label_to_bin_false(self):
+        mpls_label = 0xfffff
+        is_bos = False
+        label = b'\xff\xff\xf0'
+        label_out = mpls.label_to_bin(mpls_label, is_bos)
+
+        eq_(label, label_out)