Provide a diff feature that refine packet comparison by alxroyer-thales · Pull Request #4779 · secdev/scapy

alxroyer-thales · 2025-06-26T10:25:33Z

Draft PR for #4739.

Initiated as a draft PR for preliminary discussions before an official delivery (not squashed yet).

To be discussed:

Chaged currently based on v2.6.1 => shall I align on master? or useful to deliver for a version before?

Checklist:

If you are new to Scapy: I have checked CONTRIBUTING.md (esp. section submitting-pull-requests)
I squashed commits belonging together
I added unit tests or explained why they are not relevant
I executed the regression tests (using cd test && ./run_tests or tox)
If the PR is still not finished, please create a Draft Pull Request

- `ApproximateField` class added in 'fields.py'. - `PacketCmp` class added in a new 'diff.py' module, exported in 'all.py'. - 'test/diff.uts' unit test added.

gpotter2 · 2025-06-26T14:35:13Z

Could you show a demo of what it does in action? Thanks.

gpotter2 · 2025-06-26T14:36:42Z

scapy/fields.py

 # See https://scapy.net/ for more information
 # Copyright (C) Philippe Biondi <phil@secdev.org>
 # Copyright (C) Michael Farrell <micolous+git@gmail.com>
+# Copyright (C) 2025 Thales


My personal opinion : this one is unecessary considering the changes in the file.

I've set this line following our legal department recommendations.
Let me check with them.

Checked => removed.

alxroyer-thales · 2025-06-27T09:15:42Z

Could you show a demo of what it does in action? Thanks.

Sure. It would be worth adding faithful documentation in the end if you validate this proposal.

To reply quickly, here are extracts of outputs from the 'diff.uts' unit test I've proposed.

Comparison of packet with exact match

###(005)=[passed] 005) Compare a1 with a2 => PacketCmp.compare() returns ``True``.

>>> cmp = PacketCmp(a1, a2)
>>> assert cmp.compare(log_success_level=logging.INFO) is True
A.k: 1 (compared) == 1 (expected)
A.t: 1751014222 (compared) == 1751014222 (expected)


###(006)=[passed] 006) The comparison instance holds 2 successful exact comparisons, and no errors.

>>> print(f"diffs: {cmp.diffs!r}")
diffs: [<PacketCmp.Diff 'A.k: 1 (compared) == 1 (expected)'>, <PacketCmp.Diff 'A.t: 1751014222 (compared) == 1751014222 (expected)'>]
>>> assert len(cmp.diffs) == 2
>>> check_diff(cmp.diffs[0], "k", error=False, approx=False)
>>> check_diff(cmp.diffs[1], "t", error=False, approx=False)
>>> print(f"errors: {cmp.errors!r}")
errors: []
>>> assert len(cmp.errors) == 0

Memo: The k field is a simple ByteField, and t is an ApproximateField (see step 002).

The lines after the .compare() (step 005) are loggings activated by the log_success_level=logging.INFO configuration.

The PacketCmp object holds two lists in the end:

diffs: All PacketCmp.Diff objects, successful comparisons included.
errors: diffs` filtered on errors.

Successful comparison with approximation

###(009)=[passed] 009) Compare a1 with a2 => PacketCmp.compare() returns ``True``.

>>> cmp = PacketCmp(a1, a2)
>>> assert cmp.compare(log_success_level=logging.INFO) is True
A.t: 1751014222 (compared) ~= (delta: 1.0 <= tolerance: 2.0) 1751014221 (expected) -- comparison restarted
A.k: 1 (compared) == 1 (expected)
A.t: 1751014222 (compared) == 1751014222 (expected)


###(010)=[passed] 010) The comparison instance holds 3 diffs, the 1st being the approximation that restarted the comparison, and no errors.

>>> print(f"diffs: {cmp.diffs!r}")
diffs: [<PacketCmp.Diff 'A.t: 1751014222 (compared) ~= (delta: 1.0 <= tolerance: 2.0) 1751014221 (expected) -- comparison restarted'>, <PacketCmp.Diff 'A.k: 1 (compared) == 1 (expected)'>, <PacketCmp.Diff 'A.t: 1751014222 (compared) == 1751014222 (expected)'>]
>>> assert len(cmp.diffs) == 3
>>> check_diff(cmp.diffs[0], "t", error=False, approx=True)
>>> check_diff(cmp.diffs[1], "k", error=False, approx=False)
>>> check_diff(cmp.diffs[2], "t", error=False, approx=False)
>>> print(f"errors: {cmp.errors!r}")
errors: []
>>> assert len(cmp.errors) == 0

Comparison failure with aproximate field out of tolerance

###(013)=[passed] 013) Compare a1 with a2 => PacketCmp.compare() returns ``False``.

>>> cmp = PacketCmp(a1, a2)
>>> assert cmp.compare(log_success_level=logging.INFO) is False
A.k: 1 (compared) == 1 (expected)
A.t: 1751014222 (compared) != (delta: 3.0 > tolerance: 2.0) 1751014219 (expected) -- Mismatching values


###(014)=[passed] 014) The comparison instance holds 2 diffs, 1 error among them.

>>> print(f"diffs: {cmp.diffs!r}")
diffs: [<PacketCmp.Diff 'A.k: 1 (compared) == 1 (expected)'>, <PacketCmp.Diff 'A.t: 1751014222 (compared) != (delta: 3.0 > tolerance: 2.0) 1751014219 (expected) -- Mismatching values'>]
>>> assert len(cmp.diffs) == 2
>>> check_diff(cmp.diffs[0], "k", error=False, approx=False)
>>> check_diff(cmp.diffs[1], "t", error=True, approx=True)
>>> print(f"errors: {cmp.errors!r}")
errors: [<PacketCmp.Diff 'A.t: 1751014222 (compared) != (delta: 3.0 > tolerance: 2.0) 1751014219 (expected) -- Mismatching values'>]
>>> check_diff(cmp.errors[0], "t", error=True, approx=True)

codecov · 2025-07-01T07:52:35Z

Codecov Report

Attention: Patch coverage is 78.22581% with 54 lines in your changes missing coverage. Please review.

Project coverage is 81.02%. Comparing base (8e08cbf) to head (768e66b).
Report is 127 commits behind head on master.

Files with missing lines	Patch %	Lines
scapy/diff.py	77.29%	52 Missing ⚠️
scapy/fields.py	88.88%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4779      +/-   ##
==========================================
- Coverage   81.62%   81.02%   -0.61%     
==========================================
  Files         358      366       +8     
  Lines       85652    89275    +3623     
==========================================
+ Hits        69915    72336    +2421     
- Misses      15737    16939    +1202

Files with missing lines	Coverage Δ
scapy/all.py	`100.00% <100.00%> (ø)`
scapy/fields.py	`92.79% <88.88%> (+0.02%)`	⬆️
scapy/diff.py	`77.29% <77.29%> (ø)`

... and 102 files with indirect coverage changes

🚀 New features to boost your workflow:

❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

polybassa

The code looks good so far, however, could you please add a few more unit tests with more complex packets as test cases.

polybassa · 2025-10-13T19:08:00Z

scapy/diff.py

+
+        Uses :meth:`_debug()` for the purpose.
+        """
+        if self._debug_logging_level is not None:


Redundant code. This is already tested in "self._debug"

polybassa · 2025-10-13T19:11:21Z

scapy/diff.py

+
+        return DebugIndentationContext()
+
+    def _debug(


I'm not a fan of introducing a custom debug function in this class.

I suggest to use log_runtime by default and give the option to provide a custom logger in init:

def __init__(self, ..., logger = log_runtime): self.logger = logger

alxroyer-thales added 2 commits June 26, 2025 12:06

Add diff feature (secdev#4739)

d28b604

- `ApproximateField` class added in 'fields.py'. - `PacketCmp` class added in a new 'diff.py' module, exported in 'all.py'. - 'test/diff.uts' unit test added.

Fix Thales copyrights (secdev#4739)

dcf0b85

gpotter2 reviewed Jun 26, 2025

View reviewed changes

Remove Thales copyrights on 'fields.py' (secdev#4739)

768e66b

polybassa reviewed Oct 13, 2025

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Provide a diff feature that refine packet comparison#4779

Provide a diff feature that refine packet comparison#4779
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alxroyer-thales commented Jun 27, 2025

Comparison of packet with exact match

Successful comparison with approximation

Comparison failure with aproximate field out of tolerance

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