netdev - Re: [PATCH v3] net: bcmgenet: Fix FCS generation for fragmented skbuffs

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Date: Thu, 28 Dec 2023 13:58:02 -0800
From: Doug Berger <opendmb@...il.com>
To: Adrian Cinal <adriancinal1@...il.com>, netdev@...r.kernel.org
Cc: florian.fainelli@...adcom.com, bcm-kernel-feedback-list@...adcom.com,
 Adrian Cinal <adriancinal@...il.com>
Subject: Re: [PATCH v3] net: bcmgenet: Fix FCS generation for fragmented
 skbuffs

On 12/28/2023 5:56 AM, Adrian Cinal wrote:
> From: Adrian Cinal <adriancinal@...il.com>
> 
> The flag DMA_TX_APPEND_CRC was only written to the first DMA descriptor
> in the TX path, where each descriptor corresponds to a single skbuff
> fragment (or the skbuff head). This led to packets with no FCS appearing
> on the wire if the kernel allocated the packet in fragments, which would
> always happen when using PACKET_MMAP/TPACKET (cf. tpacket_fill_skb() in
> net/af_packet.c).
> 
> Fixes: 1c1008c793fa ("net: bcmgenet: add main driver file")
> Signed-off-by: Adrian Cinal <adriancinal1@...il.com>
> ---
> Differs from v2 in that now the flag DMA_TX_APPEND_CRC is set for all
> fragments (so as to be in line with the specification requiring the flag
> be set alongside DMA_SOP).
> 
>   drivers/net/ethernet/broadcom/genet/bcmgenet.c | 4 +++-
>   1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/broadcom/genet/bcmgenet.c b/drivers/net/ethernet/broadcom/genet/bcmgenet.c
> index 1174684a7f23..d86e5da6e157 100644
> --- a/drivers/net/ethernet/broadcom/genet/bcmgenet.c
> +++ b/drivers/net/ethernet/broadcom/genet/bcmgenet.c
> @@ -2140,8 +2140,10 @@ static netdev_tx_t bcmgenet_xmit(struct sk_buff *skb, struct net_device *dev)
>   		/* Note: if we ever change from DMA_TX_APPEND_CRC below we
>   		 * will need to restore software padding of "runt" packets
>   		 */
> +		len_stat |= DMA_TX_APPEND_CRC;
> +
>   		if (!i) {
> -			len_stat |= DMA_TX_APPEND_CRC | DMA_SOP;
> +			len_stat |= DMA_SOP;
>   			if (skb->ip_summed == CHECKSUM_PARTIAL)
>   				len_stat |= DMA_TX_DO_CSUM;
>   		}

Acked-by: Doug Berger <opendmb@...il.com>

Thanks for your help!
     Doug