linux-kernel - Re: [Bonding-devel] 2.6.29 regression? Bonding tied to IPV6 in 29-rc5

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Date:	Tue, 17 Feb 2009 16:49:16 -0500
From:	Brian Haley <brian.haley@...com>
To:	Jay Vosburgh <fubar@...ibm.com>
CC:	Andrey Borzenkov <arvidjaar@...l.ru>, "J.A. Magall"@us.ibm.com,
	ón <jamagallon@....com>,
	netdev@...r.kernel.org,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	bonding-devel@...ts.sourceforge.net
Subject: Re: [Bonding-devel] 2.6.29 regression? Bonding tied to IPV6 in 29-rc5

Jay Vosburgh wrote:
> Brian Haley <brian.haley@...com> wrote:
> 
>> Andrey Borzenkov wrote:
> [...]
>>> This hard dependency was apparently introduced by this commit:
>>>
>>> commit 305d552accae6afb859c493ebc7d98ca3371dae2
>>> Author: Brian Haley <brian.haley@...com>
>>> Date:   Tue Nov 4 17:51:14 2008 -0800
>>>
>>>     bonding: send IPv6 neighbor advertisement on failover
>> I initially had bonding IPv6 support as a Kconfig option, but it was 
>> decided it would be cleaner if it just got built-in whenever CONFIG_IPV6 
>> was set like SCTP, with the assumption you might want it.
>>
>> Is it a common configuration to not allow a module to load like you're 
>> doing in modprobe.conf?  I don't know how hard it would be to rip this 
>> out into it's own bonding_ipv6.ko module, simply turning-off CONFIG_IPV6 
>> seems better.
> 
> 	I'm not sure either of those really helps.  Distro kernels are
> built with CONFIG_IPV6 (and would have the CONFIG_BONDING_IPV6_DINGUS
> enabled as well), so the common case users would have it enabled, too.

I think that was one of the reasons too.

> 	Putting the ipv6 bits into a different module might not help,
> either, because the "core" bonding code would still have the call to the
> ipv6 functions.  Unless there's some magic way to somehow know at
> runtime whether or not the ipv6 module is loaded, and only try to
> resolve those symbols if ipv6 is loaded.  That seems complicated.

This separate bonding_ipv6 module would have to register itself with the 
"core" one with a new proto_ops of some sort.  Calls are made for the 
appropriate method, for example bond_ops->send_gratuitous(bond).  We'd 
change the IPv4 code too.  It's just a theory, does make things more 
complicated.

> 	To answer your question, I have come across this (aliasing ipv6
> to nothing in modprobe.conf to disable IPv6) from time to time, but
> didn't think of it when the NA code was added to bonding.

So I guess I'll start hacking the above, unless someone has a better 
suggestion.

-Brian
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