netdev - Re: [PATCH] ipv6: Add IFA_F

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Date:	Thu, 10 Sep 2009 18:11:20 +0200
From:	Jens Rosenboom <me@...r.de>
To:	Brian Haley <brian.haley@...com>
Cc:	david Miller <davem@...emloft.net>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	YOSHIFUJI Hideaki <yoshfuji@...ux-ipv6.org>
Subject: Re: [PATCH] ipv6: Add IFA_F_DADFAILED flag

On Wed, 2009-09-09 at 20:41 -0400, Brian Haley wrote:
> Jens Rosenboom wrote:
> > On Tue, 2009-09-08 at 11:18 -0400, Brian Haley wrote:
> >> Jens Rosenboom wrote:
> >>>> --- a/net/ipv6/addrconf.c
> >>>> +++ b/net/ipv6/addrconf.c
> >>>> @@ -1376,7 +1376,7 @@ static void addrconf_dad_stop(struct inet6_ifaddr *ifp)
> >>>>  	if (ifp->flags&IFA_F_PERMANENT) {
> >>>>  		spin_lock_bh(&ifp->lock);
> >>>>  		addrconf_del_timer(ifp);
> >>>> -		ifp->flags |= IFA_F_TENTATIVE;
> >>>> +		ifp->flags |= IFA_F_DADFAILED;
> >>> I think you still have to set IFA_F_TENTATIVE here, too, otherwise
> >>> ipv6_dev_get_saddr() will use this address. 		
> >> The tentative bit is still set from when this address was added back
> >> in ipv6_add_addr() from what I can tell, re-setting it here is actually
> >> unnecessary.  At least /sbin/ip was still showing it set during my
> >> testing.
> > 
> > There is the possibility of a race when the dad_timer expires at the
> > same time the NA triggering DAD failure is received. There isn't a big
> > chance to see that during real world testing, though.
> 
> Ok, how does this look?  I changed it to set the tentative flag as it did
> before, plus clear the dad_failed flag if the device got restarted,
> triggering DAD to happen again for any tentative address, that was an
> oversight on my part.

Looks fine to me so far, can you also send the patch for userspace? That
would making testing this a bit easier. ;-)

> I'd still like to know if using this last ifa_flag is going to be an issue,
> I actually finished a similar patch that uses a new IFA_ADDRFLAGS structure
> to pass in/out this additional info.

IMHO you should stick to this version, if any future feature needs
another bit, it may happen also to need two of them and so will need a
new structure then anyway, but why not keep it simple for now?

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