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

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Message-Id: <20111126.155757.501820041622724078.davem@davemloft.net>
Date:	Sat, 26 Nov 2011 15:57:57 -0500 (EST)
From:	David Miller <davem@...emloft.net>
To:	eric.dumazet@...il.com
Cc:	fw@...len.de, netdev@...r.kernel.org, jchapman@...alix.com
Subject: Re: [PATCH] l2tp: ensure sk->dst is still valid

From: Eric Dumazet <eric.dumazet@...il.com>
Date: Sat, 26 Nov 2011 05:30:01 +0100

> 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check callback finds that the bundle is no longer valid).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>

Applied, thanks everyone.
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