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

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Message-ID: <alpine.LRH.1.10.0804020849410.29568@netcore.fi>
Date:	Wed, 2 Apr 2008 08:56:39 +0300 (EEST)
From:	Pekka Savola <pekkas@...core.fi>
To:	YOSHIFUJI Hideaki / 吉藤英明 
	<yoshfuji@...ux-ipv6.org>
cc:	benoit.boissinot@...-lyon.org, netdev@...r.kernel.org
Subject: Re: [PATCH 4 of 5] IPv6: fix lifetime calculation on temporary
 address creation

On Wed, 2 Apr 2008, YOSHIFUJI Hideaki / ???? wrote:
>> 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.

Did I understand correctly that this issue is about the 0..1second 
interval being (for simplicity sake) being a bit shorter than exactly 
1 second?

Is there a good reason why this would be a problem?

I observe that the granularity (and I one could argue the accuracy) of 
Valid/Preferred Lifetime information is one second, so I'm not sure if 
the user should expect accuracy that's much finer than that (e.g. 0.1 
seconds).  Typically Valid/Preferred lifetimes are configured to be in 
the order of hours or even days, so what happens (with 0.1-0.01 second 
accuracy) during the last second doesn't seem very interesting from 
the practical point of view.

-- 
Pekka Savola                 "You each name yourselves king, yet the
Netcore Oy                    kingdom bleeds."
Systems. Networks. Security. -- George R.R. Martin: A Clash of Kings
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