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AppType.get(port, proto=<combined flag>) mints an unknown member and displaces the real one #736
Description
AppType.get(port, proto=<combined flag>) misses the lookup, mints an unknown member, and permanently displaces the real member in the single-bit buckets. Reproduced deterministically in a clean process:
get(7, proto=tcp) -> echo # correct
get(7, proto=tcp|udp) -> unknown (8182 -> 8183 members)
get(7, proto=tcp) -> unknown # the real member is gone
Cause
__members_proto__ (pcapkit/const/reg/apptype.py:81) is keyed on single TransportProtocol bits — tcp, udp, sctp, dccp, undefined. A combined flag is never a key, so the lookup misses, _missing_ mints an unknown member, and the registration path then files that member into each single-bit bucket the combined flag covers, overwriting whatever was there.
Impact
5,354 of 8,182 members (65%) are multi-transport, so the natural round-trip AppType.get(m.port, proto=m.proto) triggers this for most of the registry. The corruption is process-lifetime and silent.
Shipped parsing is not affected: every in-library call site passes a single bit — protocols/transport/tcp.py:615-616, udp.py:203-204, sctp.py:581-582. The hazard is the public API and anything that round-trips a member's own proto.
Notes
- Distinct from AppType.get(name) never matches an existing member and silently mints a port=-1 member instead #734, which is the
str-keyed branch at:30622. This one is about combined flags and it displaces rather than merely mints. - design: AppType is str-valued with 1,004 port=-1 members, unlike its int-valued sibling registries #732's four-way split makes this structurally impossible — per-transport classes have no combined-flag key space — so this may be resolved by that redesign rather than patched. Worth deciding which.
- Related, same area, not filed separately:
_missing_'s 766 range branches take noprotoparameter, soget(6010, proto='udp')returns a tcp member and a second identical call raisesTypeError.
Activity
JarryShaw commentedon Sep 24, 2026
Deferred to #732 rather than patched — the owner's call, and it is the right one: the four-way split removes the combined-flag key space this defect lives in, so there is nothing left to guard.
Marking
blockedand adding it to #732's acceptance criteria alongside #717 and #734, so #732 cannot close without demonstrating this case is gone. Not closing it: the corruption is live in the public API today, and a closed issue is how it gets forgotten if #732 is descoped.Acceptance criterion for #732: in a clean process,
get(7, proto=tcp|udp)must not displace the memberget(7, proto=tcp)returns, and the round-tripget(m.port, proto=m.proto)must hold for a multi-transport member.JarryShaw commentedon Sep 24, 2026
Closed by #754 (
932cb48d1). Both halves of the acceptance criterion re-measured there, one fresh process each.Displacement — gone. The recorded sequence returns the same object three times, no member-count change in any registry:
Each registry owns its own port-keyed
MultiDict, so no shared single-bit bucket survives to be overwritten.get(80, proto=tcp|udp|sctp)twice returns<TCP.http: 80 [...]>both times —'PORT_80_tcp|udp|sctp'is now unreachable, since the mint usesowner.__transport__.name(apptype.py:2417) and is always one transport.Round-trip — holds for 10,624 of the 10,625 multi-transport members, swept in one process with zero mints and zero exceptions. 5,337 hand back the TCP twin of a UDP member (LSB-first
_dispatch; same port,svcandproto), and 45 are alias→canonical collapses, which isget's documented contract withget_allfor the rest.The single exception is a different mechanism:
UDP.accessbuilder(888,tcp|udp) round-trips to<TCP.cddbp: 888 [tcp]>, because__canonical__diverges between registries on 7 ports. Filed separately — and note==cannot catch it, sinceAppType.__eq__compares ports only.