netdev - Re: [PATCH] bonding: send IPv6 neighbor advertisement on failover

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Date:	Wed, 08 Oct 2008 22:08:42 -0400
From:	Brian Haley <brian.haley@...com>
To:	Sridhar Samudrala <sri@...ibm.com>
CC:	David Stevens <dlstevens@...ibm.com>,
	Alex Sidorenko <alexandre.sidorenko@...com>,
	David Miller <davem@...emloft.net>, fubar@...ux.vnet.ibm.com,
	Simon Horman <horms@...ge.net.au>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	netdev-owner@...r.kernel.org,
	Vladislav Yasevich <vladislav.yasevich@...com>
Subject: Re: [PATCH] bonding: send IPv6 neighbor advertisement on failover

Sridhar Samudrala wrote:
> On Wed, 2008-10-08 at 15:01 -0400, Brian Haley wrote:
>> David Stevens wrote:
>>> Well, actually, it looks like I'm suggesting you to re-use something that 
>>> doesn't
>>> exist. :-)
>>>
>>> MLD (and IGMP) has such a thing where unsolicited advertisements are sent
>>> multiple times, with delays in between, to account for lossy networks 
>>> possibly
>>> dropping the first one. There are configurable counts associated with 
>>> probes
>>> and retransmit intervals for solicits, but I don't see the equivalent yet 
>>> for
>>> unsolicited NA's.
>> I don't see an equivalent either, since the only unsolicited NA the 
>> kernel sends is for DAD, which uses dad_transmits.
> 
> Doesn't DAD use neighbor solicitation rather than unsolicited NA?

Yes.  There is one case in the NS code that will respond with an 
unsolicited NA if we get a NS doing DAD.  I guess I should have made it 
clearer that it's when we're defending our address during a DAD probe.

> Can we use NS in the bonding failover scenario too?

Both and NS and NA seemed to update the switch, so either one can be 
sent on a failover event.  It seemed to be the consensus that the NA was 
more appropriate, especially since we can send it without the solicited 
bit set.

-Brian
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