em driver: netif hangs the system if interface is cabled and configured but there is no link

[John Jasem]

I'm configuring a system that's destined to be a multi-homed server,
using Intel dual port 1GbE cards that rely on the em driver.

em0 has link, and only needed configuration.

In an attempt to be ahead of the game, I pre-configured em2, plugged in
my side of the cable to be ready when the other side plugged theirs in,
and rebooted the box.

In this state, it appears the box will hang as netif works through
interfaces defined in rc.conf. I'm not sure if permanently, but I'm
willing to call 20 minutes 'permanent' for the purposes of this exercise.

I eventually was able to narrow it down to the configurations for em2,
and em2 not having link WHILE a cable was plugged in. I was able to
replicate the expected condition by unplugging the cable, and was able
to replicate the failure condition on em1 and em3 by moving the cable
and configurations.

Any thoughts? Am I missing something?

-- John Jasen (jjasen at gmail.com)