netdev - Re: [PATCH] ipv6: Avoid unnecessary temporary addresses being generated

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Date:	Wed, 12 Mar 2014 16:48:14 -0400 (EDT)
From:	David Miller <davem@...emloft.net>
To:	heiner.kallweit@....de
Cc:	netdev@...r.kernel.org
Subject: Re: [PATCH] ipv6: Avoid unnecessary temporary addresses being
 generated

From: Heiner Kallweit <heiner.kallweit@....de>
Date: Wed, 12 Mar 2014 20:53:48 +0100

> @@ -1103,8 +1103,11 @@ retry:
>  	 * Lifetime is greater than REGEN_ADVANCE time units.  In particular,
>  	 * an implementation must not create a temporary address with a zero
>  	 * Preferred Lifetime.
> +	 * Use age calculation as in addrconf_verify to avoid unnecessary
> +	 * temporary addresses being generated.
>  	 */
> -	if (tmp_prefered_lft <= regen_advance) {
> +	age = (now - ifp->tstamp + ADDRCONF_TIMER_FUZZ_MINUS) / HZ;
> +	if (tmp_prefered_lft <= regen_advance + age) {

I think you must use tmp_tstamp here, we snapshot all of the values
above into local variables while holding the lock so that we calculate
a consistent set of values and tests.
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