netdev - Re: [PATCH v2] bonding: send IPv6 neighbor advertisement on failover

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Date:	Fri, 10 Oct 2008 13:15:08 -0400
From:	Vlad Yasevich <vladislav.yasevich@...com>
To:	Sridhar Samudrala <sri@...ibm.com>
CC:	Brian Haley <brian.haley@...com>, Jay Vosburgh <fubar@...ibm.com>,
	David Stevens <dlstevens@...ibm.com>,
	Alex Sidorenko <alexandre.sidorenko@...com>,
	David Miller <davem@...emloft.net>,
	Simon Horman <horms@...ge.net.au>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	netdev-owner@...r.kernel.org,
	YOSHIFUJI Hideaki <yoshfuji@...ux-ipv6.org>
Subject: Re: [PATCH v2] bonding: send IPv6 neighbor advertisement on	failover

Sridhar Samudrala wrote:
> On Fri, 2008-10-10 at 12:29 -0400, Vlad Yasevich wrote:
>> Brian Haley wrote:
>>> Jay Vosburgh wrote:
>>>>     As a semi-related question, what does IPv6 do if it receives a
>>>> gratutitous NA, and finds a duplicate?
> 
> I think Jay was asking about the case where the target address in the NA 
> matches the address of the receiving interface. The RFCs don't describe
> how to handle such a case and leave it to the implementation. Linux logs
> a warning message and ignores such NA.
> 

Yes, but in this case, you have duplicate addresses configured.  This
can happen when subnets merge and isn't really related to bonding driver.

In such a case, if we do an NS, it will trigger an NA and we'll end up
logging such a warning.  If we do an NA, the other end, if it's linux, will
log this warning, or deal with it in its own manner.

So, it's really a draw.

-vlad

> Thanks
> Sridhar
> 
>>> If a node has an IPv6 neighbor entry and receives an unsolicited NA it
>>> will change it's state to stale, forcing a re-lookup on the next
>>> transmit.  An un-solicited NA will change the state to reachable.
>>                 ^^^^^^^^^^^^
>>
>> You probably meant to say "solicited".  Unsolicited NAs can only change
>> the state to STALE.
>>
>> Also, the re-lookup will happen on a delay after the transmit.
>>
>> -vlad
> 
> 

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