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fix(foundation): warn when PyPCAP, PCAP_CT or PyPCAPFile ignores Extractor(context=) (#2313) (#2332)
Problem: the DPKT, Scapy and PyShark engines warn that a parsing context supplied through 'context=' is ignored, but the PyPCAP, PCAP_CT and PyPCAPFile engines never read Extractor._exctx and drop it silently. Fix: each of the three engines' run() emits the same AttributeWarning, naming the engine, right after its layer/protocol threshold warning, and lists it under Warns: as DPKT and Scapy do. Test: each engine's unit test drives run() with a non-empty _exctx and pins the exact warning; the shared fixtures gain an empty _exctx, so the threshold tests' call counts also pin that no context stays silent.
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6 files changed

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‎pcapkit/foundation/engines/pcap_ct.py‎

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@@ -309,6 +309,9 @@ def run(self) -> 'None':
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and/or :attr:`self.extractor._exptl <pcapkit.foundation.extraction.Extractor._exptl>`
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is provided as the pcap-ct engine does not
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support such operations.
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* if :attr:`self.extractor._exctx <pcapkit.foundation.extraction.Extractor._exctx>`
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is provided, as the pcap-ct engine does not parse with :mod:`pcapkit`'s
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own protocol implementations.
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* if reassembly and/or flow tracing is enabled, as the pcap-ct
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engine performs no protocol dissection and so cannot support
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either operation.
@@ -357,6 +360,12 @@ def run(self) -> 'None':
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f"'layer={ext._exlyr}' and 'protocol={ext._exptl}' ignored",
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AttributeWarning, stacklevel=stacklevel())
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if ext._exctx:
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warn("'Extractor(engine=pcap_ct)' does not parse with pcapkit's own protocol "
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"implementations, so the parsing context supplied through "
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"'context=' is ignored",
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AttributeWarning, stacklevel=stacklevel())
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if ext.magic_number not in PCAP.MAGIC_NUMBER:
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raise FormatError(f'unsupported file format: {ext.magic_number!r}; '
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'the pcap-ct engine reads PCAP savefiles only')

‎pcapkit/foundation/engines/pypcap.py‎

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@@ -262,6 +262,9 @@ def run(self) -> 'None':
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and/or :attr:`self.extractor._exptl <pcapkit.foundation.extraction.Extractor._exptl>`
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is provided as the PyPCAP engine does not
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support such operations.
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* if :attr:`self.extractor._exctx <pcapkit.foundation.extraction.Extractor._exctx>`
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is provided, as the PyPCAP engine does not parse with :mod:`pcapkit`'s
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own protocol implementations.
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* if reassembly and/or flow tracing is enabled, as the PyPCAP
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engine performs no protocol dissection and so cannot support
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either operation.
@@ -284,6 +287,12 @@ def run(self) -> 'None':
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f"'layer={ext._exlyr}' and 'protocol={ext._exptl}' ignored",
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AttributeWarning, stacklevel=stacklevel())
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if ext._exctx:
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warn("'Extractor(engine=pypcap)' does not parse with pcapkit's own protocol "
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"implementations, so the parsing context supplied through "
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"'context=' is ignored",
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AttributeWarning, stacklevel=stacklevel())
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if ext.magic_number not in PCAP.MAGIC_NUMBER:
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raise FormatError(f'unsupported file format: {ext.magic_number!r}; '
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'the PyPCAP engine reads PCAP savefiles only')

‎pcapkit/foundation/engines/pypcapfile.py‎

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@@ -221,6 +221,9 @@ def run(self) -> 'None':
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and/or :attr:`self.extractor._exptl <pcapkit.foundation.extraction.Extractor._exptl>`
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is provided as the PyPCAPFile engine does not
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support such operations.
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* if :attr:`self.extractor._exctx <pcapkit.foundation.extraction.Extractor._exctx>`
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is provided, as the PyPCAPFile engine does not parse with :mod:`pcapkit`'s
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own protocol implementations.
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* if IPv6 reassembly is enabled, as |pcapfile|_ has no IPv6
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decoder.
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* if |pcapfile|_ has no decoder for the savefile's link layer
@@ -241,6 +244,12 @@ def run(self) -> 'None':
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f"'layer={ext._exlyr}' and 'protocol={ext._exptl}' ignored",
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AttributeWarning, stacklevel=stacklevel())
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if ext._exctx:
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warn("'Extractor(engine=pypcapfile)' does not parse with pcapkit's own protocol "
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"implementations, so the parsing context supplied through "
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"'context=' is ignored",
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AttributeWarning, stacklevel=stacklevel())
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if ext.magic_number not in PCAP.MAGIC_NUMBER:
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raise FormatError(f'unsupported file format: {ext.magic_number!r}; '
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'the PyPCAPFile engine reads PCAP savefiles only')

‎tests/foundation/engines/test_pcap_ct_engine.py‎

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Original file line numberDiff line numberDiff line change
@@ -169,6 +169,7 @@ def make_extractor(self, **overrides):
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'_frnum': 0,
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'_exlyr': 'none',
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'_exptl': 'null',
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'_exctx': {},
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'_vfunc': mock.Mock(),
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'magic_number': PCAP_MAGIC,
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}
@@ -389,6 +390,25 @@ def test_run_warns_on_layer_and_protocol_threshold(self) -> None:
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self.assertIn('protocol and layer threshold', warn.call_args.args[0])
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self.assertIs(warn.call_args.args[1], AttributeWarning)
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def test_run_warns_that_a_parsing_context_is_ignored(self) -> None:
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from pcapkit.utilities.warnings import AttributeWarning
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# #2313: the engine never parses with pcapkit's own protocols, so a
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# ``context=`` has no effect and the caller is told so, as DPKT, Scapy and
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# PyShark already do. The fixture's empty ``_exctx`` stays silent, which
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# the threshold test above pins through its call count.
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extractor, _ = self.make_extractor(_exctx={'ipv4': mock.sentinel.context})
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engine = self.engine(extractor)
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with mock.patch.object(engine._expkg, 'pcap', return_value=FakeHandle()):
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with mock.patch('pcapkit.foundation.engines.pcap_ct.warn') as warn:
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engine.run()
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self.assertEqual(warn.call_count, 1)
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self.assertEqual(warn.call_args.args[0],
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"'Extractor(engine=pcap_ct)' does not parse with pcapkit's own "
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"protocol implementations, so the parsing context supplied "
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"through 'context=' is ignored")
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self.assertIs(warn.call_args.args[1], AttributeWarning)
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def test_run_rejects_pcapng_rather_than_reading_it_approximately(self) -> None:
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from pcapkit.utilities.exceptions import FormatError
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‎tests/foundation/engines/test_pypcap_engine.py‎

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@@ -112,6 +112,7 @@ def make_extractor(self, **overrides):
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'_frnum': 0,
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'_exlyr': 'none',
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'_exptl': 'null',
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'_exctx': {},
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'_vfunc': mock.Mock(),
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'magic_number': PCAP_MAGIC,
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}
@@ -308,6 +309,25 @@ def test_run_warns_on_layer_and_protocol_threshold(self) -> None:
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self.assertIn('protocol and layer threshold', warn.call_args.args[0])
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self.assertIs(warn.call_args.args[1], AttributeWarning)
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def test_run_warns_that_a_parsing_context_is_ignored(self) -> None:
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from pcapkit.utilities.warnings import AttributeWarning
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# #2313: the engine never parses with pcapkit's own protocols, so a
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# ``context=`` has no effect and the caller is told so, as DPKT, Scapy and
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# PyShark already do. The fixture's empty ``_exctx`` stays silent, which
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# the threshold test above pins through its call count.
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extractor, _ = self.make_extractor(_exctx={'ipv4': mock.sentinel.context})
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engine = self.engine(extractor)
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with mock.patch.object(engine._expkg, 'pcap', return_value=FakeHandle()):
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with mock.patch('pcapkit.foundation.engines.pypcap.warn') as warn:
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engine.run()
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self.assertEqual(warn.call_count, 1)
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self.assertEqual(warn.call_args.args[0],
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"'Extractor(engine=pypcap)' does not parse with pcapkit's own "
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"protocol implementations, so the parsing context supplied "
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"through 'context=' is ignored")
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self.assertIs(warn.call_args.args[1], AttributeWarning)
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def test_run_rejects_pcapng_rather_than_yielding_no_frames(self) -> None:
312332
from pcapkit.utilities.exceptions import FormatError
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‎tests/foundation/engines/test_pypcapfile_engine.py‎

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Original file line numberDiff line numberDiff line change
@@ -196,6 +196,7 @@ def make_extractor(self, **overrides):
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'_frnum': 0,
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'_exlyr': 'none',
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'_exptl': 'null',
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'_exctx': {},
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'_vfunc': mock.Mock(),
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'magic_number': PCAP_MAGIC,
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}
@@ -257,6 +258,24 @@ def test_run_warns_on_layer_and_protocol_threshold(self) -> None:
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self.assertIn('protocol and layer threshold', warn.call_args.args[0])
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self.assertIs(warn.call_args.args[1], AttributeWarning)
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261+
def test_run_warns_that_a_parsing_context_is_ignored(self) -> None:
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from pcapkit.utilities.warnings import AttributeWarning
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# #2313: the engine never parses with pcapkit's own protocols, so a
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# ``context=`` has no effect and the caller is told so, as DPKT, Scapy and
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# PyShark already do. The fixture's empty ``_exctx`` stays silent, which
267+
# the threshold test above pins through its call count.
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extractor, _ = self.make_extractor(_exctx={'ipv4': mock.sentinel.context})
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engine = self.engine(extractor)
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with mock.patch('pcapkit.foundation.engines.pypcapfile.warn') as warn:
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engine.run()
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self.assertEqual(warn.call_count, 1)
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self.assertEqual(warn.call_args.args[0],
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"'Extractor(engine=pypcapfile)' does not parse with pcapkit's own "
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"protocol implementations, so the parsing context supplied "
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"through 'context=' is ignored")
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self.assertIs(warn.call_args.args[1], AttributeWarning)
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def test_run_rejects_pcapng(self) -> None:
261280
from pcapkit.utilities.exceptions import FormatError
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