Add new class MPLSVPN for ipv4/ipv6 MPLS processing

Signed-off-by: Peng Xiao <xiaoquwl@gmail.com>

yabgp/message/attribute/nlri/mpls_vpn.py

@@ -0,0 +1,44 @@
+# Copyright 2016 Cisco Systems, Inc.
+# All rights reserved.
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+
+import struct
+
+
+class MPLSVPN(object):
+    """The base class for ipv4/ipv6 mpls vpn
+    """
+    WITHDARW_LABEL_HEX = b'\x80\x00\x00'
+    WITHDARW_LABEL = 524288
+
+    @classmethod
+    def parse_mpls_label_stack(cls, data):
+        labels = []
+        while len(data) >= 3:
+            label = struct.unpack('!L', b'\00'+data[:3])[0]
+            data = data[3:]
+            labels.append(label >> 4)
+            if label & 0x001:
+                break
+        return labels
+
+    @classmethod
+    def construct_mpls_label_stack(cls, labels, bos=True):
+        data = b''
+        for label in labels:
+            if bos:
+                data += struct.pack('!L', (label << 4 | 1))[1:]
+                continue
+            data += struct.pack('!L', label << 4)[1:]
+        return data

yabgp/tests/unit/message/attribute/nlri/test_mpls_vpn.py

@@ -0,0 +1,38 @@
+# Copyright 2016 Cisco Systems, Inc.
+# All rights reserved.
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+
+""" Test MPLS VPN """
+
+import unittest
+
+from yabgp.message.attribute.nlri.mpls_vpn import MPLSVPN
+
+
+class TestMPLSVPN(unittest.TestCase):
+
+    def test_parse_mpls_label_stack(self):
+        label_bin = b'\x00\x01\x41'
+        self.assertEqual([20], MPLSVPN.parse_mpls_label_stack(label_bin))
+        label_bin = b'\x00\x01\x10\x00\x01\x31'
+        self.assertEqual([17, 19], MPLSVPN.parse_mpls_label_stack(label_bin))
+        label_bin = b'\x80\x00\x00'
+        self.assertEqual([524288], MPLSVPN.parse_mpls_label_stack(label_bin))
+
+    def test_construct_mpls_label_stack(self):
+        label_bin = b'\x00\x01\x41'
+        self.assertEqual(label_bin, MPLSVPN.construct_mpls_label_stack(labels=[20]))
+
+if __name__ == '__main__':
+    unittest.main()