Feature/add-ptp-protocol

[satveerbrar]

@polybassa @gpotter2
Here is the draft PR to add PTP protocol.

Currently this includes basic PTP header and Sync message type.

Planned additions in future commits:

1. post_build function to calculate and insert message length field.
2. Classes for the remaining PTP message types.
3. Unit tests

Let me know if I have followed the correct approach.

fixes #4637

[gpotter2]

Thanks for the PR!
A few comments. It's a good start !

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 18 lines in your changes missing coverage. Please review.

Project coverage is 81.62%. Comparing base (92925da) to head (7bf9906).
Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
scapy/layers/ptp_v2.py	0.00%	18 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4640      +/-   ##
==========================================
+ Coverage   80.71%   81.62%   +0.90%     
==========================================
  Files         359      360       +1     
  Lines       86052    86253     +201     
==========================================
+ Hits        69461    70404     +943     
+ Misses      16591    15849     -742     

Files with missing lines	Coverage Δ
scapy/layers/ptp_v2.py	0.00% <0.00%> (ø)

... and 25 files with indirect coverage changes

[eyalitki]

Hi, found this when going over the issues in the repository. I suggest you use the following logic I implemented way back during my thesis on IEEE 1588 security - eyalitki/ptpd@4e46fe9#diff-bf2c30fee47c7daecd502ee34e25bc6324ff333f293f9d539d3ec4277764acaf.

You can ignore the "encryption" fields as they were part of my thesis and weren't adopted by the IEEE 1588 security committee. Still, the layer implements all non-control messages + Announce, so it should become handy. It served me well in my python scripts for sending/receiving packets, so it is well tested (even if old).

I hereby grant full access rights for this code and its derivatives to be used as part of the Scapy repository in any way the maintainers of the repository deem to be fit. Enjoy.

[polybassa]

You could also use BitScalingField here. This would allow you to add a unit to the value for the representation to the user. If you think that's useful. But since the field names already contain the unit, it's not really necessary.