netdev - Re: [Patch net-next 2/2] net: dump whole skb data in netdev_rx_csum

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Message-ID: <a1e1b48b-68af-16f6-2442-b96718f6ae00@gmail.com>
Date:   Wed, 21 Nov 2018 05:05:31 -0800
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Cong Wang <xiyou.wangcong@...il.com>, netdev@...r.kernel.org
Cc:     Herbert Xu <herbert@...dor.apana.org.au>,
        Eric Dumazet <edumazet@...gle.com>,
        David Miller <davem@...emloft.net>
Subject: Re: [Patch net-next 2/2] net: dump whole skb data in
 netdev_rx_csum_fault()



On 11/20/2018 06:13 PM, Cong Wang wrote:
> Currently, we only dump a few selected skb fields in
> netdev_rx_csum_fault(). It is not suffient for debugging checksum
> fault. This patch introduces skb_dump() which dumps skb mac header,
> network header and its whole skb->data too.
> 
> Cc: Herbert Xu <herbert@...dor.apana.org.au>
> Cc: Eric Dumazet <edumazet@...gle.com>
> Cc: David Miller <davem@...emloft.net>
> Signed-off-by: Cong Wang <xiyou.wangcong@...il.com>
> ---


> +	print_hex_dump(level, "skb data: ", DUMP_PREFIX_OFFSET, 16, 1,
> +		       skb->data, skb->len, false);

As I mentioned to David, we want all the bytes that were maybe already pulled

(skb->head starting point, not skb->data)

Also we will miss the trimmed bytes if there were padding data.

And it seems the various bugs we have are all tied to the pulled or trimmed bytes.

Thanks.