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From: John Baldwin <jhb@freebsd.org>
To: freebsd-net@freebsd.org
Subject: Re: Multicast races on vlan & lagg
Date: Mon, 11 Aug 2014 17:10:46 -0400
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 (bigwig.baldwin.cx); Mon, 11 Aug 2014 17:29:18 -0400 (EDT)
Cc: Alexander Motin <mav@freebsd.org>
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On Thursday, July 31, 2014 10:21:22 am Alexander Motin wrote:
> Hi.
> 
> Doing some tests on FreeNAS (FreeBSD 9.2+) I hit series of panic during
> active interfaces manipulation in some scenarios including multicast and
> several vlans on top of lagg. I am not ready to reproduce the full
> environment on head, but the code looks equal, so probably the bugs.
> 
> I've made a patch to improve locking in that area, that seems fixes the
> problems: http://people.freebsd.org/~mav/mcast_vlan_lagg.patch
> 
> Could somebody with more experience in the area please take a look?

Can't you use IF_ADDR_RLOCK instead of IF_ADDR_WLOCK?  Also, strictly speaking 
it might be best to use if_maddr_rlock() instead of directly using 
IF_ADDR_RLOCK().

-- 
John Baldwin