Subject: Re: [PATCH] net: fec: fix regression on i.MX28 introduced by rx_copybreak support

From: Sergei Shtylyov <[email-masked]>
Date: Tue, 07 Oct 2014 20:07:00 +0400

Hello.

On 10/07/2014 05:19 PM, Lothar Waßmann wrote:

> commit 1b7bde6d659d ("net: fec: implement rx_copybreak to improve rx performance")
> introduced a regression for i.MX28. The swap_buffer() function doing
> the endian conversion of the received data on i.MX28 may access memory
> beyond the actual packet size in the DMA buffer. fec_enet_copybreak()
> does not copy those bytes, so that the last bytes of a packet may be
> filled with invalid data after swapping.
> This will likely lead to checksum errors on received packets.
> E.g. when trying to mount an NFS rootfs:
> UDP: bad checksum. From 192.168.1.225:111 to 192.168.100.73:44662 ulen 36

> Do the byte swapping and copying to the new skb in one go if
> necessary.

> Signed-off-by: Lothar Waßmann <[email-masked]>
> ---
>   drivers/net/ethernet/freescale/fec_main.c |   25 +++++++++++++++++++++----
>   1 file changed, 21 insertions(+), 4 deletions(-)

> diff --git a/drivers/net/ethernet/freescale/fec_main.c b/drivers/net/ethernet/freescale/fec_main.c
> index 87975b5..eaaebad 100644
> --- a/drivers/net/ethernet/freescale/fec_main.c
> +++ b/drivers/net/ethernet/freescale/fec_main.c
[...]
> @@ -1348,7 +1360,7 @@ fec_enet_new_rxbdp(struct net_device *ndev, struct bufdesc *bdp, struct sk_buff
>   }
>
>   static bool fec_enet_copybreak(struct net_device *ndev, struct sk_buff **skb,
> -			       struct bufdesc *bdp, u32 length)
> +			       struct bufdesc *bdp, u32 length, int swap)

    'bool swap' perhaps?

> @@ -1393,6 +1408,7 @@ fec_enet_rx_queue(struct net_device *ndev, int budget, u16 queue_id)
>   	u16	vlan_tag;
>   	int	index = 0;
>   	bool	is_copybreak;
> +	bool need_swap = id_entry->driver_data & FEC_QUIRK_SWAP_FRAME;

    ... especially talking this into account...

WBR, Sergei