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

Sergey Shtylyov
2024-09-30T19:30:28Z

On 9/30/24 22:11, Sergey Shtylyov wrote:
[...]

>> From: Paul Barker <paul.barker.ct@bp.renesas.com>
>>
>> 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@bp.renesas.com>
> [...]
>> 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)
[...]
>> + 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...

Even fit better there, I think...

>> +
>> + 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...

No need to keep using get_unaligned_le16() itself but you should then switch to
using get_unaligned().

[...]

MBR, Sergey