From mboxrd@z Thu Jan  1 00:00:00 1970
From: David Miller <davem@davemloft.net>
Subject: Re: [PATCH]NET: Add ECN support for TSO
Date: Tue, 11 Jul 2006 18:51:31 -0700 (PDT)
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To: ravinandan.arakali@neterion.com
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From: "Ravinandan Arakali" <ravinandan.arakali@neterion.com>
Date: Tue, 11 Jul 2006 18:45:48 -0700

> tk = tcp_sk(skb->sk);
> if (tk->ecn_flags & TCP_ECN_OK)
>    /* Check CE, ECE, CWR etc */
> 
> I find that skb->sk is NULL. Is this the correct way to check the
> per-session
> ECN capability ? Why is skb->sk NULL ?

On receive?  There is no reason for skb->sk to be anything other than
NULL on receive, the networking stack hasn't even seen the packet yet.
Only the driver has seen the skb.