[JarryShaw]

• Searched for similar pull requests
• Followed the coding style (make pylint, make mypy, make isort) — mypy on the 4 source files and pylint E/W on the new test only; no new messages, but not the full make targets
• make test passes, and a test case covers the change — per module only, listed below; not the full make test
• Added a changelog entry under docs/source/changelog/ and regenerated CHANGELOG.md, if the change is user-visible — N/A, added centrally after the wave

What is the purpose of your pull request?

• fix — corrects a defect

---

Description of your pull request and other information

Closes #1173. IPv6_Route (4), MH (6), HOPOPT and IPv6_Opts (2) now hint 8, their minimum header (RFC 8200 §4.4/§4.3/§4.6, RFC 6275 §6.1.1). ApplicationBase._import_next_layer already reaches _parse_next_layer through super(), so it is unchanged; a test pins that route.

IPv4 + zero body	before	after
IPv6_Route, 4–7 octets	IPv6-Route, rebuilds 8	Raw, rebuilds 4–7
MH, 6–7 octets	MH, rebuilds 8	Raw, rebuilds 6–7

HOPOPT/IPv6_Opts were not fabricating (short streams already fail to parse), so their change is for correctness only. test_ipv6_extension_unit and test_mh_unit pinned the old hints and now pin 8.

from_data sweep over examples/captures/ (1612 frames) is the same before and after: IPv4 0/0, UDP 0/0, TCP 0/0, IPv6 0 / 183 (pre-existing), with byte-identical layer chains.

Tests: the new test_length_hint_minimum_header_unit.py gives 4 passed; without the fix, 10 subtests fail. ipv6_extension 61, mh 52, ipv6_ext 30, next_layer_short_header 7, ospf 3, option_roundtrip 6, tests/project 389 passed / 1 skipped. Ordering legs: protocols (rest) 838, 0F/0E before and after; protocols/internet 468 → 472, 0F/0E.

[github-actions]

Coverage: 88.89% (unit tier, Python 3.14, 222dd72a2, Unit Tests run success)

Package	Statements	Missed	Branches	Partial	Cover
pcapkit (top level)	104	4	20	4	93.55%
pcapkit/const	18757	1034	2342	845	90.24%
pcapkit/corekit	1878	91	580	22	94.34%
pcapkit/dumpkit	142	0	42	0	100.00%
pcapkit/foundation	2442	102	852	39	94.38%
pcapkit/interface	112	7	40	5	92.11%
pcapkit/protocols	15707	188	3974	163	98.19%
pcapkit/toolkit	487	65	144	1	85.42%
pcapkit/utilities	429	4	122	4	98.55%
pcapkit/vendor	4409	2359	1006	158	42.84%

Per-file detail: the coverage-html artifact of this run.

[JarryShaw]

Cross-review verdict on 222dd72a2: GOOD TO GO (ran on Sonnet; author Opus). Labelled review: good-to-go.

• Hints: the RFC 8200 §4.3/§4.4/§4.6 and RFC 6275 §6.1.1 minimums were checked against the RFC text. An 8-octet header and any longer one still parse as IPv6_Route, MH, HOPOPT or IPv6_Opts, whether over IPv4 or in the IPv6 chain.
• Behaviour change: the only change against main is Route at 4–7 octets and MH at 6–7 octets, which now become Raw and rebuild exactly.
• Fails without the fix: with the four source files reverted, 10 subtests fail.
• Ordering legs: protocols (rest) ran 838 tests and protocols/internet ran 472, both 0 failures and 0 errors.
• Capture sweep: the from_data output is byte-identical between main and this PR.
• Application path: application payloads reach the guard (application.py:132-154).
• Nit: the application-path test and the complete-headers test pass on main as well. That is correct for guards, but neither one proves the fix.

Two follow-ups, both reproduced on main as well and neither blocking: #1177 (from_data drops extension headers, which I re-measured as 48→40 octets) and #1178 (whether the IPv6_Ext fallback hint stays at 2, needs: decision). CI: 0 failed, 0 incomplete.