networkd fails the entire can0 configuration on the unsupported option
("Device doesn't support restart from Bus Off") and never raises the
link — found by the reboot test; this, not a socket race, was also the
afternoon's "off (failed)". Bus-off recovery falls to open3e's service
restart loop.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>