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…rt read (#2727) In HOPOPT and IPv6-Opts, a capture cut leaving only the type octet of a CALIPSO, SMF_DPD or MPL option logged "FieldValueError: ... invalid <X> option length: 0", at CRITICAL and again by beholder inside IPv6: the callbacks sizing the option refused the zero the cut left for Opt Data Len, before the short read could record the cut. - Schema.unpack gives the fields after the one the data ends inside the short read, as __short_read__ in their packet, a forward match included, and clears it as each unpack starts, so a nested schema finds only its own. - calipso_pad_len, mpl_opt_pad_len, smf_i_dpd_id_len and smf_dpd_data_selector leave an Opt Data Len the data ends before to the short read. #2694's rule then keeps CALIPSO and SMF_DPD, and refuses MPL quietly, as its parser refuses the zero, as Router Alert's does. - An Opt Data Len on the wire too short raises ProtocolError, not FieldValueError, so a header refused for it is refused quietly. The four helpers' documented Raises class moves: the breaking change. - Schema._note_short_read takes packet as an optional argument, so a caller with none keeps the record on the schema alone. - The utilities-or-corekit page says how a callback tells a cut. - Tests sweep every option of both headers at every cut, alone and in IPv6; the pins of the FieldValueError move to ProtocolError. The new tests fail on ab7be2f. protocols, corekit and project pass module by module.
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make pylint,make mypy,make isort)make testpasses, and a test case covers the changeWhat is the purpose of your pull request?
fix— corrects a defectA capture cut that left only the type octet of a CALIPSO, SMF_DPD or MPL option, in HOPOPT or IPv6-Opts, logged a
FieldValueError, at CRITICAL inside IPv6. The option's length callback rejected the zero-filled length.Schema.unpackhands the fields after a cut the record of where the data ended, aspacket['__short_read__']. The record is popped at the start of each unpack, so it never leaks between siblings or packets.Schema._note_short_readtakes the packet as an optional argument.ipv6_option.pydefer only when that record shows the data ended before the length field. Nothing is clamped. CALIPSO and SMF_DPD then read as a recorded short read and rebuild byte-exactly throughinfoandto_dict(). MPL is refused quietly, because its parser rejects a length under 2, as fix(corekit): a capture cut inside an option area is refused, and loudly, instead of a short read #2694 pins for Router Alert.ProtocolErrorwhere 1.5.1 raisedFieldValueError. The two are siblings underBaseErrorandValueError. Inside IPv6 such a header becomes quietRawinstead of logging CRITICAL.The new tests fail on
main. A trial merge with #2711's commit passes both sides' new tests.Closes #2727