VNET kernel panic on remove renamed interfaces

[Reshad Patuck]

Hi,

I am trying to use vnet and pf to host multiple (100s of) jails on a server with a jailed pf router, which will be spun up and down by a script.

I rename the epair interfaces so that I know which jail links to which interface (for convenience).

After I delete the jail and renamed epair the kernel panics when I attempt to recreate the epair.

I believe this is an issue occurs only when I have renamed the epair.

This issue seems to be fixed in 12-CURRENT as I can not make it crash on current. However this continues to happen on 11-STABLE and 11.0-RELEASE.

I have found these which seem to fix something similar issues:
https://svnweb.freebsd.org/base?view=revision&sortby=rev&revision=292604
https://svnweb.freebsd.org/base/projects/vnet/_scripts/jail-vnet-epair-regression01.sh?view=markup

I have attached scripts that crash the system for the latest versions on 11.0-RELEASE and 11-STABLE branches.

Can someone help me find where this problem was fixed? (for 12) and if there are any plans to backport the fix to the 11 branch.

Also any tips on running 100s of VNET jails on a single box would be much appreciated, and if there is anything I can help test I have some physical and VMware boxes I can test on.

Kernel version I have tested on:
FreeBSD FreeBSD-11-RELEASE 11.0-RELEASE-p8 FreeBSD 11.0-RELEASE-p8 #1 r315007: Fri Mar 10 17:27:30 UTC 2017 root at FreeBSD-11-RELEASE:/usr/obj/usr/src/sys/VNET amd64
FreeBSD FreeBSD-11-STABLE 11.0-STABLE FreeBSD 11.0-STABLE #1 r315241: Tue Mar 14 12:58:54 UTC 2017 root at FreeBSD-11-STABLE:/usr/obj/usr/src/sys/VNET amd64
FreeBSD FreeBSD-12 12.0-CURRENT FreeBSD 12.0-CURRENT #1 r315237: Tue Mar 14 10:17:06 UTC 2017 root at FreeBSD-12:/usr/obj/usr/src/sys/VNET amd64 

Attached:
vnet-rename-epair.sh - Create and destroy a VNET jail in a loop while renaming the epair interface. This crashes on 11. 
vnet-no-rename-epair.sh - Create and destroy a VNET jail while not renaming the epair interface. This does not crash.
info.0 - info file from core dump on FreeBSD-11-STABLE
core.txt.0 - core.txt.0 file from core dump on FreeBSD-11-STABLE

Best regards,

Reshad
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