netdev - Re: [PATCH net-next 2/2] ipv6: dont cache cloned routes

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Date:	Wed, 12 Sep 2012 13:52:44 -0700
From:	Maciej Żenczykowski <zenczykowski@...il.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	David Miller <davem@...emloft.net>,
	netdev <netdev@...r.kernel.org>,
	Lorenzo Colitti <lorenzo@...gle.com>,
	Tom Herbert <therbert@...gle.com>
Subject: Re: [PATCH net-next 2/2] ipv6: dont cache cloned routes

Acked-by: Maciej Żenczykowski <maze@...gle.com>

On Wed, Sep 12, 2012 at 5:01 AM, Eric Dumazet <eric.dumazet@...il.com> wrote:
> From: Eric Dumazet <edumazet@...gle.com>
>
> We can now destroy cloned routes immediately from dst_release() instead
> of depending on garbage collection.
>
> Set DST_NOCACHE in rt6_alloc_clone() so that :
>
> 1) we avoid calling ip6_ins_rt() on such routes
>
> 2) dst_release() can call destroy when refcount becomes 0
>
> This allows machines to resist to DDOS.
>
> Reported-by: Lorenzo Colitti <lorenzo@...gle.com>
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Cc: Maciej Żenczykowski <maze@...gle.com>
> Cc: Tom Herbert <therbert@...gle.com>
> ---
>  net/ipv6/route.c |    3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/net/ipv6/route.c b/net/ipv6/route.c
> index d4ba3fc..fedbb41 100644
> --- a/net/ipv6/route.c
> +++ b/net/ipv6/route.c
> @@ -840,6 +840,7 @@ static struct rt6_info *rt6_alloc_clone(struct rt6_info *ort,
>         struct rt6_info *rt = ip6_rt_copy(ort, daddr);
>
>         if (rt) {
> +               rt->dst.flags |= DST_NOCACHE;
>                 rt->rt6i_flags |= RTF_CACHE;
>                 rt->n = neigh_clone(ort->n);
>         }
> @@ -887,7 +888,7 @@ restart:
>
>         dst_hold(&rt->dst);
>         if (nrt) {
> -               err = ip6_ins_rt(nrt);
> +               err = (nrt->dst.flags & DST_NOCACHE) ? 0 : ip6_ins_rt(nrt);
>                 if (!err)
>                         goto out2;
>         }
>
>
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