add RENAME devctl event for IFNET

[rozhuk.im-gmail.com]

Summary

Add devd event on network iface rename.

Test Plan

Apply patch, rebuild and reinstall kernel.

Run in terminal1:
cat /var/run/devd.pipe

In terminal2:
ifconfig lan0 name lan1
ifconfig lan1 name lan0

Result
terminal1 will produce output:
!system=IFNET subsystem=lan0 type=RENAME name=lan1
!system=IFNET subsystem=lan1 type=RENAME name=lan0

*lan0 must me replaced with real network interface name.

[imp]

Can you add rename to sbin/devd/devd.conf.5 please?

[rozhuk.im-gmail.com]

Update sbin/devd/devd.conf.5

[asomers]

There's insufficient context in the diff. If you created this revision through the web interface, use "diff -U 9999" to capture more context. OTOH, you won't need to do that if you use the arcanist CLI,

[asomers]

sbin/devd/devd.conf.5

470

Don't forget to touch the .Dd too.

sys/net/if.c

2677

I think you're sending the notification too early. It looks to me like it would be possible for userspace to see the notification before the interface has its new name.

[rozhuk.im-gmail.com]

Move code down, update date.

[rozhuk.im-gmail.com]

Add var old_name to keep if_xname.

[rozhuk.im-gmail.com]

This diff based on changes from https://reviews.freebsd.org/D30840 for file: sbin/devd/devd.conf.5

[imp]

This looks good to me now.