Adding optional padding into table features Property to make it multiple of 8

[italovalcy]

Closes #102

Summary

See updated changelog file and/or add any other summarized helpful information for reviewers

Local Tests

Without the proposed changes:

>>> from pyof.v0x04.common.flow_instructions import InstructionType, Instruction
... from pyof.v0x04.controller2switch.common import InstructionsProperty, TableFeaturePropType
... insts = [
...     InstructionType.OFPIT_GOTO_TABLE,
...     InstructionType.OFPIT_WRITE_METADATA,
...     InstructionType.OFPIT_WRITE_ACTIONS,
...     InstructionType.OFPIT_APPLY_ACTIONS,
...     InstructionType.OFPIT_CLEAR_ACTIONS,
...     InstructionType.OFPIT_METER,
... ]
... inst_ids = []
... for inst in insts:
...     inst_ids.append(Instruction(instruction_type=inst))
...
... inst_prop = InstructionsProperty(property_type=TableFeaturePropType.OFPTFPT_INSTRUCTIONS, instruction_ids=inst_ids)
...
>>> inst_prop.pack()
b'\x00\x00\x00\x1c\x00\x01\x00\x04\x00\x02\x00\x04\x00\x03\x00\x04\x00\x04\x00\x04\x00\x05\x00\x04\x00\x06\x00\x04'
>>> len(inst_prop.pack())
28
>>>

With the changes:

>>> from pyof.v0x04.common.flow_instructions import InstructionType, Instruction
... from pyof.v0x04.controller2switch.common import InstructionsProperty, TableFeaturePropType
... insts = [
...     InstructionType.OFPIT_GOTO_TABLE,
...     InstructionType.OFPIT_WRITE_METADATA,
...     InstructionType.OFPIT_WRITE_ACTIONS,
...     InstructionType.OFPIT_APPLY_ACTIONS,
...     InstructionType.OFPIT_CLEAR_ACTIONS,
...     InstructionType.OFPIT_METER,
... ]
... inst_ids = []
... for inst in insts:
...     inst_ids.append(Instruction(instruction_type=inst))
...
... inst_prop = InstructionsProperty(property_type=TableFeaturePropType.OFPTFPT_INSTRUCTIONS, instruction_ids=inst_ids)
...
>>> inst_prop.pack()
b'\x00\x00\x00\x1c\x00\x01\x00\x04\x00\x02\x00\x04\x00\x03\x00\x04\x00\x04\x00\x04\x00\x05\x00\x04\x00\x06\x00\x04\x00\x00\x00\x00'
>>> len(inst_prop.pack())
32
>>>

See that, new size is multiple of 8 by padding with 4 zero bytes, as suggested by the spec.

I've also added unit tests from packet capture obtained from a passive openflow connection from a Noviflow switch (I preferred to use Noviflow instead of OpenVswitch because the Table Features from OpenVSwitch is huge.. has many fields from NXM -- Nicira Extended Match and others).

End-to-End Tests

Please refer to the results presented here: #110

The end-to-end tests were executed with all PRs stacked

[viniarck]

LGTM. Just left a trivial comment about documenting a TODO

Thanks, Italo. Great to have table features Property packing fixed and improved.

[viniarck]

LGTM. Thanks for the updates, @italovalcy