From mboxrd@z Thu Jan  1 00:00:00 1970
From: Eric Dumazet <eric.dumazet@gmail.com>
Subject: Re: [PATCH net-next 3/3] v4 GRE: Add TCP segmentation offload for
 GRE
Date: Fri, 15 Feb 2013 06:41:00 -0800
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Cc: netdev@vger.kernel.org, edumazet@google.com, jesse@nicira.com,
	bhutchings@solarflare.com, mirqus@gmail.com
To: Pravin B Shelar <pshelar@nicira.com>
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On Thu, 2013-02-14 at 16:02 -0800, Pravin B Shelar wrote:

> +	err = ip_local_out(skb);
> +	if (likely(net_xmit_eval(err) == 0)) {
> +		int pkt_len = skb->len - skb_transport_offset(skb);
> +		u64_stats_update_begin(&tstats->syncp);
> +		tstats->tx_bytes += pkt_len;
> +		tstats->tx_packets++;
> +		u64_stats_update_end(&tstats->syncp);
> +	} else {
> +		dev->stats.tx_errors++;
> +		dev->stats.tx_aborted_errors++;
> +	}
>  	return NETDEV_TX_OK;

Once given to ip_local_out(), you cant reference the skb anymore,
therefore you must evaluate pkt_len before :

pkt_len = skb->len - skb_transport_offset(skb);
err = ip_local_out(skb);
if (likely(net_xmit_eval(err) == 0)) {
    ...