netdev - Re: [IPV6] ADDRCONF: Defer dad for global address until dad for linklocal is completed.

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Date:	Tue, 20 May 2008 21:27:56 +0900
From:	Toyo Abe <tabe@...aclelinux.com>
To:	YOSHIFUJI Hideaki / 吉藤英明 
	<yoshfuji@...ux-ipv6.org>
CC:	davem@...emloft.net, netdev@...r.kernel.org,
	Toyo Abe <tabe@...aclelinux.com>
Subject: Re: [IPV6] ADDRCONF: Defer dad for global address until dad for linklocal
 is completed.

Yoshifuji-san,

Thanks for your response.

 > Why don't we just ignore RA until DAD for link-local
 > address has been successfully completed?
I was also thinking so. And I tried it at first.
But then, many other test scenarios in TAHI test suite went to FAIL. It 
was because
the tester node send RA with prefix option to the host right after it 
receives DAD NS
from the host, which is obviously in autoconfiguration process for 
linklocal address.

Besides, RFC4862 section 4(protocol overview) says;
---
To speed the autoconfiguration process, a host may generate its link-
local address (and verify its uniqueness) in parallel with waiting
for a Router Advertisement. Because a router may delay responding to
a Router Solicitation for a few seconds, the total time needed to
complete autoconfiguration can be significantly longer if the two
steps are done serially.
---

The  text indicates that a host *may* accept RA including prefix option 
even before
completion of DAD for linklocal address.
Since current addrconf code actually accepts RA including prefix option 
while DAD for
linklocal address is processing, changes of the behaviour looks like a 
degradation for me.
Hence, I chose to accept RA at that moment and defer sending DAD NS for 
global addresses.

Thanks,
-toyo

YOSHIFUJI Hideaki / 吉藤英明 wrote:
> In article <48324792.5070309@...aclelinux.com> (at Tue, 20 May 2008 
> 12:37:54 +0900), Toyo Abe <tabe@...aclelinux.com> says:
>
>> This patch fixes the problem by deferring DAD initiation for global 
>> address until
>> DAD for linklocal address is completed. Now the failed test scenarios 
>> noted above
>> are all passed.
>
> Why don't we just ignore RA until DAD for link-local
> address has been successfully completed?
>
> --yoshfuji
>
>

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