netdev - Re: [net] e1000: Small packets may get corrupted during padding by HW

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Message-ID: <CAHXqBFJZnGUSUutN=L-_LpCN7dXLPFY0ndJnQJ10NCcbzPVLww@mail.gmail.com>
Date:	Sat, 15 Sep 2012 22:44:58 +0200
From:	Michał Mirosław <mirqus@...il.com>
To:	Jeff Kirsher <jeffrey.t.kirsher@...el.com>
Cc:	davem@...emloft.net, Tushar Dave <tushar.n.dave@...el.com>,
	netdev@...r.kernel.org, gospo@...hat.com, sassmann@...hat.com
Subject: Re: [net] e1000: Small packets may get corrupted during padding by HW

2012/9/15 Jeff Kirsher <jeffrey.t.kirsher@...el.com>:
> From: Tushar Dave <tushar.n.dave@...el.com>
>
> On PCI/PCI-X HW, if packet size is less than ETH_ZLEN,
> packets may get corrupted during padding by HW.
> To WA this issue, pad all small packets manually.
>
> Signed-off-by: Tushar Dave <tushar.n.dave@...el.com>
> Tested-by: Aaron Brown <aaron.f.brown@...el.com>
> Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@...el.com>
> ---
>  drivers/net/ethernet/intel/e1000/e1000_main.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
>
> diff --git a/drivers/net/ethernet/intel/e1000/e1000_main.c b/drivers/net/ethernet/intel/e1000/e1000_main.c
> index 3bfbb8d..bde337e 100644
> --- a/drivers/net/ethernet/intel/e1000/e1000_main.c
> +++ b/drivers/net/ethernet/intel/e1000/e1000_main.c
> @@ -3149,6 +3149,17 @@ static netdev_tx_t e1000_xmit_frame(struct sk_buff *skb,
>                 return NETDEV_TX_OK;
>         }
>
> +       /* On PCI/PCI-X HW, if packet size is less than ETH_ZLEN,
> +        * packets may get corrupted during padding by HW.
> +        * To WA this issue, pad all small packets manually.
> +        */
> +       if (skb->len < ETH_ZLEN) {
> +               if (skb_pad(skb, ETH_ZLEN - skb->len))
> +                       return NETDEV_TX_OK;
> +               skb->len = ETH_ZLEN;
> +               skb_set_tail_pointer(skb, ETH_ZLEN);
> +       }
> +

Isn't there a skb_padto() that does just this?

Best Regards,
Michał Mirosław
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