Re: [net-next PATCH 05/11] net: ravb: Simplify types in RX csum validation

[Sergey Shtylyov]

On 9/30/24 19:08, Paul Barker wrote:

> From: Paul Barker <paul.barker.ct@xxxxxxxxxxxxxx>
> 
> The HW checksum value is used as a 16-bit flag, it is zero when the

   I think I prefer s/HW/hardware/ but there's no hard feelings... :-)

> checksum has been validated and non-zero otherwise. Therefore we don't
> need to treat this as an actual __wsum type or call csum_unfold(), we
> can just use a u16 pointer.
> 
> Signed-off-by: Paul Barker <paul.barker.ct@xxxxxxxxxxxxxx>
[...]
> diff --git a/drivers/net/ethernet/renesas/ravb_main.c b/drivers/net/ethernet/renesas/ravb_main.c
> index 1dd2152734b0..9350ca10ab22 100644
> --- a/drivers/net/ethernet/renesas/ravb_main.c
> +++ b/drivers/net/ethernet/renesas/ravb_main.c
[...]
> @@ -762,23 +761,22 @@ static void ravb_rx_csum_gbeth(struct sk_buff *skb)
>  	 * The last 2 bytes are the protocol checksum status which will be zero
>  	 * if the checksum has been validated.
>  	 */
> -	if (unlikely(skb->len < sizeof(__sum16) * 2))
> +	csum_len = sizeof(*hw_csum) * 2;

   Could've been done by an initializer instead?

> +	if (unlikely(skb->len < csum_len))
>  		return;
>  
>  	if (skb_is_nonlinear(skb)) {
> -		last_frag = &shinfo->frags[shinfo->nr_frags - 1];
> -		hw_csum = skb_frag_address(last_frag) +
> -			  skb_frag_size(last_frag);
> -		skb_frag_size_sub(last_frag, 2 * sizeof(__sum16));
> +		skb_frag_t *last_frag = &shinfo->frags[shinfo->nr_frags - 1];

   Could've been done in the previous patch...

> +
> +		hw_csum = (u16 *)(skb_frag_address(last_frag) +
> +				  skb_frag_size(last_frag));
> +		skb_frag_size_sub(last_frag, csum_len);
>  	} else {
> -		hw_csum = skb_tail_pointer(skb);
> -		skb_trim(skb, skb->len - 2 * sizeof(__sum16));
> +		hw_csum = (u16 *)skb_tail_pointer(skb);
> +		skb_trim(skb, skb->len - csum_len);
>  	}
>  
> -	hw_csum -= sizeof(__sum16);
> -	csum_proto = csum_unfold((__force __sum16)get_unaligned_le16(hw_csum));
> -
> -	if (!csum_proto)
> +	if (!*--hw_csum)

   Hm, you lost get_unaligned_le16() here. The checksum can be anywhere,
unaligned too...

[...]

MBR, Sergey