linux-kernel - Re: ipv6: default route for link local address is not added while assigning a address

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Message-ID: <52D3A885.2080107@gmail.com>
Date:	Mon, 13 Jan 2014 14:19:09 +0530
From:	sohny thomas <sohny.kernel@...il.com>
To:	netdev <netdev@...r.kernel.org>, linux-kernel@...r.kernel.org,
	yoshfuji@...ux-ipv6.org, davem@...emloft.net,
	kumuda <kumuda@...ux.vnet.ibm.com>, hannes@...essinduktion.org
Subject: Re: ipv6: default route for link local address is not added while
 assigning a address

On Friday 10 January 2014 10:46 PM, Hannes Frederic Sowa wrote:
> On Fri, Jan 10, 2014 at 05:33:08PM +0100, Nicolas Dichtel wrote:
>> CC: netdev
>>
>> Le 10/01/2014 13:20, sohny thomas a écrit :
>>> Default route for link local address is configured automatically if
>>> NETWORKING_IPV6=yes is in ifcfg-eth*.
>>> When the route table for the interface is flushed and a new address is
>>> added to
>>> the same device with out removing linklocal addr, default route for link
>>> local
>>> address has to added by default.
>> I would say that removing the link local route but not the link local
>> address
>> is a configuration problem.
>> If you remove a connected route but not the associated address, you will
>> have
>> the same problem.
> We have some user accessible routes that are essential for IPv6 stack
> to work at all. So I don't know if I can agree with that.
>
> Maybe flush is a bit too aggressive?
>
Hi ,

Thank you for the inputs.

In the test for ipv6 default address selection , we are testing the rule
2 as specified in RFC 6724

   If Scope(SA) < Scope(SB): If Scope(SA) < Scope(D), then prefer SB
     and otherwise prefer SA.
     Similarly, if Scope(SB) < Scope(SA): If Scope(SB) < Scope(D), then
     prefer SA and otherwise prefer SB.

Test:

   Check 04:
      Destination: ff08::2(OS)
      Candidate Source Addresses: fec0::1(SS) or LLA(LS)
      Result: fec0::1(SS)

      Scope(LLA) < Scope(fec0::1): If Scope(LLA) < Scope(ff08::2),  yes, 
prefer fec0::1


Now in the test its flushing all the routes and adding an address ,
which in causes to add route into the routing table including the link
local routes.
Earlier in 2.6.32 it used to work fine now due to the above mentioned
check-in this is not happening

Of course we can still just delete a route and add , but even if we
delete the link local route, IMHO i think it should update the LLA route
when the interface is next added an address or bought up which ever is
the case.

Regards,
Sohny


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