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

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Date:	Mon, 03 Feb 2014 16:23:00 +0100
From:	Nicolas Dichtel <nicolas.dichtel@...nd.com>
To:	Sohny Thomas <sthomas@...ux.vnet.ibm.com>,
	netdev <netdev@...r.kernel.org>, linux-kernel@...r.kernel.org,
	yoshfuji@...ux-ipv6.org, davem@...emloft.net,
	kumuda <kumuda@...ux.vnet.ibm.com>,
	Hannes Frederic Sowa <hannes@...essinduktion.org>
Subject: Re: [PATCH] ipv6: default route for link local address is not added
 while assigning a address

Le 03/02/2014 08:19, Sohny Thomas a écrit :
>
>> Actually I am not so sure, there is no defined semantic of flush. I would
>> be ok with all three solutions: leave it as is, always add link-local
>> address (it does not matter if we don't have a link-local address on
It matters. This address is required.
RFC 4291
Section 2.1:
    All interfaces are required to have at least one Link-Local unicast
    address (see Section 2.8 for additional required addresses).
Section 2.8:
       o Its required Link-Local address for each interface.

>> that interface, as a global scoped one is just fine enough) or make flush not
>> remove the link-local address (but this seems a bit too special cased for me).
>
> 1) In case if we leave it as it is, there is rfc 6724 rule 2 to be considered (
> previously rfc 3484)
>
> Rule 2: Prefer appropriate scope.
>     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:
>
>     Destination: fe80::2(LS)
>      Candidate Source Addresses: 3ffe::1(GS) or fec0::1(SS) or LLA(LS)
>      Result: LLA(LS)
>      Scope(LLA) < Scope(fec0::1): If Scope(LLA) < Scope(fe80::2),  no, prefer LLA
>      Scope(LLA) < Scope(3ffe::1): If Scope(LLA) < Scope(fe80::2),  no, prefer LLA
>
>
> Now the above test fails since the route itself is not present, and the test
> assumes that the route gets added since the LLA is not removed during the test
In your scenario, the link local route has been removed manually, not by the
kernel. What is your network manager?

>
> 2) having a LLA always helps in NDP i think
A link-local Address yes, it's a MUST. But having only the link local route will
not help.

>
> 3) making flush not remove link-local address will be chnaging functionality of
> ip flush command
You can flush by specifying the prototype:
ip -6 route flush proto static


Regards,
Nicolas
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