The reproduction section described the harness only in prose; the actual
driver scripts were throwaway lab files. Embed the distilled, runnable
reproducer (drives uBridge's control socket through the repo's own client,
kept tap for the single-variable A/B), the exact measurement semantics
(40 re-enslavements, ~1 kHz / 200 ms membership sampling, a release = the
brif entry vanishing, latency print) and the flip protocol, so a reader
can reproduce the 19-20/40 vs 0/40 numbers on an affected host. Also point
the host-fix layer at the reproducer for re-verification.
A kernel-datapath link could die silently after a delete/recreate: on
NetworkManager hosts, NM's state machine releases an NM-managed TAP from
its bridge 58-87 ms after (re)enslavement (~50% while the tap has not
been assumed yet; the port stays up, no GNS3 process logs anything).
Root-caused with a server-free minimal harness (one uBridge, one tap,
one bridge, an addif/delif loop) and a single-variable NM A/B; the
NetworkManager side is explained by three of its commits (assumption
recheck on external enslavement, master removal during activation,
external changes not touching assumed slaves).
Records: forensic signatures (ifindex unchanged, flags 0x300 cleared,
heal-on-next-update), the reproducer, the verified host fix
(unmanaged-devices conf.d snippet: 19-20/40 -> 0/40, and the e2e
scenario green with test-side workarounds disabled), scope and history
(2016 issue #440 veth incident; the 2026-10-01 ethernet-switch
incident previously misattributed). Cross-linked from the L2-anchor
spec and the switch feature doc.
