Idunn launches managed targets with PrivatePIDs=yes; systemd writes the
outer-namespace pid into LISTEN_PID, which the daemon cannot observe, so
the first v2 probation process exited at once with "systemd authority FDs
belong to another process". Odin made the same change in 8e16f56.
The exact descriptor count and name order, the root-owned read-only
descriptor checks and the signature verification of their contents bind
the descriptors to Idunn; LISTEN_PID must still be a canonical non-zero
pid. The layout test is now pure and runs on every platform; restoring
the own-pid comparison fails it.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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