netdev - Re: [PATCH] IPv6: Implement RFC 4429 Optimistic Duplicate Address Detection

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Date:	Mon, 29 Jan 2007 11:34:47 -0500
From:	Neil Horman <nhorman@...driver.com>
To:	Vlad Yasevich <vladislav.yasevich@...com>
Cc:	YOSHIFUJI Hideaki / 吉藤英明 
	<yoshfuji@...ux-ipv6.org>, sri@...ibm.com, davem@...emloft.net,
	kuznet@....inr.ac.ru, pekkas@...core.fi, jmorris@...ei.org,
	kaber@...eworks.de, netdev@...r.kernel.org
Subject: Re: [PATCH] IPv6: Implement RFC 4429 Optimistic Duplicate Address Detection

On Fri, Jan 26, 2007 at 04:42:41PM -0500, Vlad Yasevich wrote:
> Neil Horman wrote:
> > On Fri, Jan 26, 2007 at 03:28:40PM -0500, Vlad Yasevich wrote:
> >> Hi Neil
> >>
> >> Neil Horman wrote:
> >>> On Fri, Jan 26, 2007 at 09:13:31AM +0900, YOSHIFUJI Hideaki / 吉藤英明 wrote:
> >>>> In article <20070125194500.GB8891@...reliant.homelinux.net> (at Thu, 25 Jan 2007 14:45:00 -0500), Neil Horman <nhorman@...driver.com> says:
> >>>
> >>> New patch attached with most of your suggestions incorporated.  I've a few
> >>> comments mixed in for some of the suggestions that I think need further
> >>> discussion
> >>>
> >>>> If optimistic_dad is disabled, flags should be IFA_F_TEMPORARY,
> >>>> not IFA_F_TEMPORARY|IFA_F_OPTIMISTIC.
> >>>>
> >>>> Another idea is to use IFA_F_OPTIMISTIC not
> >>>> IFA_F_OPTIMISTIC|IFA_F_TENTATIVE until the DAD has been finished.
> >>>>
> >>> I'm currently setting the OPTIMISTIC flag in every location that its possibly
> >>> needed, and then clearing it in addrconf_dad_start if that interface is not
> >>> participating in optimistic dad.  I do this because the RFC in section 3.1
> >>> indicates that manually configured addresses should not set the optimistic flag.
> >>> If I removed the OPTIMISTIC flag from the locations it gets set in the patch and
> >>> then only set it for participating interfaces in addrconf_dad_start, I would
> >>> need to have some way to tell if the address in question was manually configured
> >>> (to avoid setting it in that case).  At present I see no clear way to do that,
> >>> but if you have a suggestion, I'll happily change this around.
> >> One suggestiong/question:
> >>
> >> Instead of clearing the OPTIMISTIC flag in addrconf_dad_start(), wouldn't it be better
> >> to simply not set the flag in ipv6_add_addr()?  Just mask that flag from the 'flags'
> >> argument passed to that function when conditions are right.
> >>
> > Doh!  Sometimes I don't just think straight.  Yes, as long as ipv6_add_addr is
> > only for adding static addresses (which it pretty clearly is), that would work
> > much better.  I'll fix it up and repost on monday.
> > 
> > Don't suppose you have any thoughts on how to solve the "send to default router"
> > problem, do you?
> > 
> 
> Still trying to figure how the routing side works. sorry....
> 
> -vlad
I've got your flag changes made, but I'm holding off on reposting for a bit.
Dave M. just gave me some advice on how best to handle the default router case.
Trying to understand the routing code and integrate that before I repost.

Thanks
Neil

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