netdev - Re: [PATCH net-next v3 2/2] ipv6: remove from fib tree aged out RTF

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Message-ID: <20171019210221.kucy67evij65nctx@kafai-mbp.dhcp.thefacebook.com>
Date:   Thu, 19 Oct 2017 14:02:21 -0700
From:   Martin KaFai Lau <kafai@...com>
To:     Paolo Abeni <pabeni@...hat.com>
CC:     <netdev@...r.kernel.org>, "David S. Miller" <davem@...emloft.net>,
        Wei Wang <weiwan@...gle.com>,
        Eric Dumazet <edumazet@...gle.com>,
        Hannes Frederic Sowa <hannes@...essinduktion.org>
Subject: Re: [PATCH net-next v3 2/2] ipv6: remove from fib tree aged out
 RTF_CACHE dst

On Thu, Oct 19, 2017 at 02:07:11PM +0000, Paolo Abeni wrote:
> The commit 2b760fcf5cfb ("ipv6: hook up exception table to store
> dst cache") partially reverted the commit 1e2ea8ad37be ("ipv6: set
> dst.obsolete when a cached route has expired").
> 
> As a result, RTF_CACHE dst referenced outside the fib tree will
> not be removed until the next sernum change; dst_check() does not
> fail on aged-out dst, and dst->__refcnt can't decrease: the aged
> out dst will stay valid for a potentially unlimited time after the
> timeout expiration.
> 
> This change explicitly removes RTF_CACHE dst from the fib tree when
> aged out. The rt6_remove_exception() logic will then obsolete the
> dst and other entities will drop the related reference on next
> dst_check().
> 
> pMTU exceptions are not aged-out, and are removed from the exception
> table only when the - usually considerably longer - ip6_rt_mtu_expires
> timeout expires.
> 
> v1 -> v2:
>   - do not touch dst.obsolete in rt6_remove_exception(), not needed
> v2 -> v3:
>   - take care of pMTU exceptions, too
> 
> Fixes: 2b760fcf5cfb ("ipv6: hook up exception table to store dst cache")
> Signed-off-by: Paolo Abeni <pabeni@...hat.com>
Acked-by: Martin KaFai Lau <kafai@...com>