netdev - Re: [PATCH] l2tp: ensure sk->dst is still valid

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Date:	Sat, 26 Nov 2011 05:30:01 +0100
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Florian Westphal <fw@...len.de>
Cc:	netdev <netdev@...r.kernel.org>,
	James Chapman <jchapman@...alix.com>
Subject: Re: [PATCH] l2tp: ensure sk->dst is still valid

Le vendredi 25 novembre 2011 à 17:47 +0100, Florian Westphal a écrit :
> When using l2tp over ipsec, the tunnel will hang when rekeying
> occurs. Reason is that the transformer bundle attached to the dst entry
> is now in STATE_DEAD and thus xfrm_output_one() drops all packets
> (XfrmOutStateExpired increases).
> 
> Fix this by calling __sk_dst_check (which drops the stale dst
> if xfrm dst->check callback finds that the bundle is no longer valid).
> 
> Cc: James Chapman <jchapman@...alix.com>
> Signed-off-by: Florian Westphal <fw@...len.de>
> ---
>  net/l2tp/l2tp_core.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/net/l2tp/l2tp_core.c b/net/l2tp/l2tp_core.c
> index cf0f308..89ff8c6 100644
> --- a/net/l2tp/l2tp_core.c
> +++ b/net/l2tp/l2tp_core.c
> @@ -1072,7 +1072,7 @@ int l2tp_xmit_skb(struct l2tp_session *session, struct sk_buff *skb, int hdr_len
>  
>  	/* Get routing info from the tunnel socket */
>  	skb_dst_drop(skb);
> -	skb_dst_set(skb, dst_clone(__sk_dst_get(sk)));
> +	skb_dst_set(skb, dst_clone(__sk_dst_check(sk, 0)));
>  
>  	inet = inet_sk(sk);
>  	fl = &inet->cork.fl;

Seems good to me, although we could use RCU and skb_dst_set_noref() to
avoid dirtying dst refcount. I'll send a patch for net-next later.

Acked-by: Eric Dumazet <eric.dumazet@...il.com>



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