"Downing" interfaces on reboot cmd or a panic

None of the above do.

"shutdown -r" does, as it calls back through the "stop" chain in netif.  
But a reboot command (or kernel panic) does not; the latter obviously 
can't and the former doesn't go through any of those nicities at all.

I've never seen this cause trouble on a LAN but when the machine in 
question is an Internet gateway in some cases ONTs in particular want to 
see the interface carrier disappear specifically to tell it that the 
line was reset.  If it doesn't then on machine restart it may not remain 
properly associated with the ONT and thus you get no -- or partial -- 
connectivity.

On a cold boot this isn't an issue because the interface was never up in 
the first place, but on restarts it can be.  I've got an ISP here that 
sometimes will not restore connectivity properly in this instance, but 
on a shutdown (or power cycle) it never has a problem -- and it appears, 
from watching the interface LEDs, that the lack of carrier-toggling is 
responsible.  While an "attended" restart is easy ("don't use reboot") 
what's not-so-much is if the machine takes a panic while nobody is there 
to attend it and connectivity does not come back up.

I'm curious if anyone has thought about how this might be better handled 
(e.g. is this something that perhaps the startup sequence should have a 
flag for and, if its present, then all interfaces are "down"ed first as 
a protective measure to force carrier off before being configured?)

Thoughts?

-- 
Karl Denninger
karl@denninger.net
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