Merge pull request #444 from macartur/issue-#381

Add generic unpack method

Author: beraldoleal

pyof/utils.py

@@ -0,0 +1,65 @@
+"""General Unpack utils for python-openflow.
+
+This package was moved from kytos/of_core for the purpose of creating a generic
+method to perform package unpack independent of the OpenFlow version.
+"""
+from pyof import v0x01, v0x04
+from pyof.foundation.exceptions import UnpackException
+
+PYOF_VERSION_LIBS = {0x01: v0x01,
+                     0x04: v0x04}
+
+
+def validate_packet(packet):
+    """Check if packet is valid OF packet.
+
+    Raises:
+        UnpackException: If the packet is invalid.
+    """
+    if not isinstance(packet, bytes):
+        raise UnpackException('invalid packet')
+
+    packet_length = len(packet)
+
+    if packet_length < 8 or packet_length > 2**16:
+        raise UnpackException('invalid packet')
+
+    if packet_length != int.from_bytes(packet[2:4],
+                                       byteorder='big'):
+        raise UnpackException('invalid packet')
+
+    version = packet[0]
+    if version == 0 or version >= 128:
+        raise UnpackException('invalid packet')
+
+
+def unpack(packet):
+    """Unpack the OpenFlow Packet and returns a message.
+
+    Returns:
+        GenericMessage: Message unpacked based on openflow packet.
+
+    Raises:
+        UnpackException: if the packet can't be unpacked.
+    """
+    validate_packet(packet)
+
+    version = packet[0]
+    try:
+        pyof_lib = PYOF_VERSION_LIBS[version]
+    except KeyError:
+        raise UnpackException('Version not supported')
+
+    try:
+        header = pyof_lib.common.header.Header()
+        header.unpack(packet[:header.get_size()])
+        message = pyof_lib.common.utils.new_message_from_header(header)
+
+        binary_data = packet[header.get_size():]
+        binary_data_size = header.length - header.get_size()
+
+        if binary_data and len(binary_data) == binary_data_size:
+            message.unpack(binary_data)
+        return message
+    except (UnpackException, ValueError) as exception:
+        raise UnpackException(exception)

tests/test_utils.py

@@ -0,0 +1,39 @@
+"""Automate utils tests."""
+import unittest
+
+from pyof.utils import UnpackException, unpack, validate_packet
+from pyof.v0x01.symmetric.hello import Hello as Hello_v0x01
+from pyof.v0x04.symmetric.hello import Hello as Hello_v0x04
+
+
+class TestUtils(unittest.TestCase):
+    """Run tests to verify unpack independent of version."""
+
+    def test_unpack_v0x01_packet(self):
+        """Test if the package in version v0x01 is properly unpacked."""
+        data = Hello_v0x01().pack()
+        expected = unpack(data)
+        self.assertEqual(expected.pack(), data)
+
+    def test_unpack_v0x04_packet(self):
+        """Test if the package in version v0x04 is properly unpacked."""
+        data = Hello_v0x04().pack()
+        expected = unpack(data)
+        self.assertEqual(expected.pack(), data)
+
+    def test_invalid_packet_with_version_more_then_128(self):
+        """Test validate a invalid packet with version more than 128."""
+        hello = Hello_v0x04()
+        hello.header.version = 129
+
+        self.assertRaises(UnpackException, validate_packet, hello.pack())
+
+    def test_validate_packet_with_invalid_packets(self):
+        """Test validate a invalid packet with invalid packets."""
+        hello = Hello_v0x04()
+
+        hello.header.version = 128
+        self.assertRaises(UnpackException, validate_packet, hello.pack())
+
+        hello.header.version = 0
+        self.assertRaises(UnpackException, validate_packet, hello.pack())