netdev - Re: [PATCH 4 of 5] IPv6: fix lifetime calculation on temporary address creation

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Date:	Wed, 02 Apr 2008 09:25:14 +0900 (JST)
From:	YOSHIFUJI Hideaki / 吉藤英明 
	<yoshfuji@...ux-ipv6.org>
To:	benoit.boissinot@...-lyon.org
Cc:	netdev@...r.kernel.org, pekkas@...core.fi, yoshfuji@...ux-ipv6.org
Subject: Re: [PATCH 4 of 5] IPv6: fix lifetime calculation on temporary
 address creation

In article <20080402001706.GD32592@...zuine> (at Wed, 2 Apr 2008 02:17:06 +0200), Benoit Boissinot <benoit.boissinot@...-lyon.org> says:

> On Wed, Apr 02, 2008 at 08:41:14AM +0900, YOSHIFUJI Hideaki / 吉藤英明 wrote:
> > In article <20080401215657.GP475@...zuine> (at Tue, 1 Apr 2008 23:56:57 +0200), Benoit Boissinot <benoit.boissinot@...-lyon.org> says:
> > 
> > > On Fri, Mar 28, 2008 at 12:04:01PM +0900, YOSHIFUJI Hideaki / 吉藤英明 wrote:
> > > > In article <ec551b4a5bb25cda00ff.1206305172@...zuine> (at Sun, 23 Mar 2008 21:46:12 +0100), Benoit Boissinot <benoit.boissinot@...-lyon.org> says:
> > > > 
> > > > > IPv6: fix lifetime calculation on temporary address creation
> > > [snip]
> > > > > +	now = jiffies;
> > > > > +	elapsed = (now - ifp->tstamp) / HZ;
> > > > > +	if (elapsed >= ifp->valid_lft)
> > > > > +		tmp_valid_lft = 0;
> > > > > +	else
> > > > > +		tmp_valid_lft = min_t(__u32,
> > > > > +				      ifp->valid_lft - elapsed,
> > > > > +				      idev->cnf.temp_valid_lft);
> > > > > +	if (elapsed >= ifp->prefered_lft)
> > > > > +		tmp_prefered_lft = 0;
> > > > > +	else
> > > > > +		tmp_prefered_lft = min_t(__u32,
> > > > > +					 ifp->prefered_lft - elapsed,
> > > > > +					 idev->cnf.temp_prefered_lft - desync_factor / HZ);
> > > > 
> > > > Basically I agree, but it is possible to expire the temporary
> > > > address AFTER public address, which is not good.  Please fix this.
> > > 
> > > do you mean because of the rounding of 'elapsed' ? otherwise I don't see
> > > what the problem is, sorry.
> > 
> > Right.  Maybe we could substruct "now" by adj = (now - ifp->tstamp) % HZ;
> >    now = jiffies
> >    elapsed = (now - ifp->tstamp) / HZ;
> >    now -= (now - ifp->tstamp) % HZ;
> 
> Why not just simply round it above:
> elapsed = (now - ifp->tstamp + HZ - 1) / HZ; /* round it up */
> and the rest stays the same.
> 
> Or do we care about having a lifetime a little bit (<1s) shorter ?

Yes, I do.

--yoshfuji
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