netdev - Re: [RFC 07/12] ravb: Fillup ravb_rx

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Date:   Sat, 9 Oct 2021 11:34:35 +0300
From:   Sergei Shtylyov <sergei.shtylyov@...il.com>
To:     Biju Das <biju.das.jz@...renesas.com>,
        Sergey Shtylyov <s.shtylyov@....ru>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
Cc:     Geert Uytterhoeven <geert+renesas@...der.be>,
        Sergey Shtylyov <s.shtylyov@...russia.ru>,
        Adam Ford <aford173@...il.com>, Andrew Lunn <andrew@...n.ch>,
        Yuusuke Ashizuka <ashiduka@...itsu.com>,
        Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-renesas-soc@...r.kernel.org" 
        <linux-renesas-soc@...r.kernel.org>,
        Chris Paterson <Chris.Paterson2@...esas.com>,
        Biju Das <biju.das@...renesas.com>,
        Prabhakar Mahadev Lad <prabhakar.mahadev-lad.rj@...renesas.com>
Subject: Re: [RFC 07/12] ravb: Fillup ravb_rx_gbeth() stub

On 09.10.2021 11:27, Biju Das wrote:

>>> [...]
>>>>>>>>>>> Fillup ravb_rx_gbeth() function to support RZ/G2L.
>>>>>>>>>>>
>>>>>>>>>>> This patch also renames ravb_rcar_rx to ravb_rx_rcar to be
>>>>>>>>>>> consistent with the naming convention used in sh_eth driver.
>>>>>>>>>>>
>>>>>>>>>>> Signed-off-by: Biju Das <biju.das.jz@...renesas.com>
>>>>>>>>>>> Reviewed-by: Lad Prabhakar
>>>>>>>>>>> <prabhakar.mahadev-lad.rj@...renesas.com>[...]
>>>>>>>>>>> diff --git a/drivers/net/ethernet/renesas/ravb_main.c
>>>>>>>>>>> b/drivers/net/ethernet/renesas/ravb_main.c
>>>>>>>>>>> index 37164a983156..42573eac82b9 100644
>>>>>>>>>>> --- a/drivers/net/ethernet/renesas/ravb_main.c
>>>>>>>>>>> +++ b/drivers/net/ethernet/renesas/ravb_main.c
>>>>>>>>>>> @@ -720,6 +720,23 @@ static void ravb_get_tx_tstamp(struct
>>>>>>>>>>> net_device
>>>>>>>>>> *ndev)
>>>>>>>>>>>   	}
>>>>>>>>>>>   }
>>>>>>>>>>>
>>>>>>>>>>> +static void ravb_rx_csum_gbeth(struct sk_buff *skb) {
>>>>>>>>>>> +	u8 *hw_csum;
>>>>>>>>>>> +
>>>>>>>>>>> +	/* The hardware checksum is contained in sizeof(__sum16) (2)
>>>>>> bytes
>>>>>>>>>>> +	 * appended to packet data
>>>>>>>>>>> +	 */
>>>>>>>>>>> +	if (unlikely(skb->len < sizeof(__sum16)))
>>>>>>>>>>> +		return;
>>>>>>>>>>> +	hw_csum = skb_tail_pointer(skb) - sizeof(__sum16);
>>> [...]
>>>>>>> Please check the section 30.5.6.1 checksum calculation handling>
>>>>>>> And figure 30.25 the field of checksum attaching field
>>>>>>
>>>>>>     I have.
>>>>>>
>>>>>>> Also see Table 30.17 for checksum values for non-error conditions.
>>>>>>
>>>>>>> TCP/UDP/ICPM checksum is at last 2bytes.
>>>>>>
>>>>>>     What are you arguing with then? :-)
>>>>>>     My point was that your code fetched the TCP/UDP/ICMP checksum
>>>>>> ISO the IP checksum because it subtracts sizeof(__sum16), while
>>>>>> should probably subtract sizeof(__wsum)
>>>>>
>>>>> Agreed. My code missed IP4 checksum result. May be we need to
>>>>> extract 2 checksum info from last 4 bytes.  First checksum(2bytes)
>>>>> is IP4 header checksum and next checksum(2 bytes)  for TCP/UDP/ICMP
>>>>> and use this info finding the non error case mentioned in  Table
>> 30.17.
>>>>>
>>>>> For eg:-
>>>>> IPV6 non error-condition -->  "0xFFFF"-->IPV4HeaderCSum value and
>> "0x0000"
>>>>> TCP/UDP/ICMP CSUM value
>>>>>
>>>>> IPV4 non error-condition -->  "0x0000"-->IPV4HeaderCSum value and
>> "0x0000"
>>>>> TCP/UDP/ICMP CSUM value
>>>>>
>>>>> Do you agree?
>>>
>>>> What I meant here is some thing like below, please let me know if you
>>>> have any issues with this, otherwise I would like to send the patch
>> with below changes.
>>>>
>>>> Further improvements can happen later.
>>>>
>>>> Please let me know.
>>>>
>>>> +/* Hardware checksum status */
>>>> +#define IPV4_RX_CSUM_OK                0x00000000
>>>> +#define IPV6_RX_CSUM_OK                0xFFFF0000
>>>
>>>     Mhm, this should prolly come from the IP headers...
>>>
>>> [...]
>>>> diff --git a/drivers/net/ethernet/renesas/ravb_main.c
>>>> b/drivers/net/ethernet/renesas/ravb_main.c
>>>> index bbb42e5328e4..d9201fbbd472 100644
>>>> --- a/drivers/net/ethernet/renesas/ravb_main.c
>>>> +++ b/drivers/net/ethernet/renesas/ravb_main.c
>>>> @@ -722,16 +722,18 @@ static void ravb_get_tx_tstamp(struct
>>>> net_device *ndev)
>>>>
>>>>   static void ravb_rx_csum_gbeth(struct sk_buff *skb)  {
>>>> -       u16 *hw_csum;
>>>> +       u32 csum_result;
>>>
>>>     This is not against the patch currently under investigation. :-)
>>>
>>>> +       u8 *hw_csum;
>>>>
>>>>          /* The hardware checksum is contained in sizeof(__sum16) (2)
>> bytes
>>>>           * appended to packet data
>>>>           */
>>>> -       if (unlikely(skb->len < sizeof(__sum16)))
>>>> +       if (unlikely(skb->len < sizeof(__wsum)))
>>>
>>>     I think this usage of __wsum is valid (I remember that I suggested
>> it). We have 2 16-bit checksums here
>>
>>     I meant "I don't think", of course. :-)
> 
> Ok will use 2 * sizeof(__sum16) instead and extract IPV4 header csum and TCP/UDP/ICMP csum result.

    I'm not sure how to deal with the later...

> All error condition/unsupported cases will be passed to stack with CHECKSUM_NONE
> and only non-error cases will be set as CHECKSUM_UNNCESSARY.
> 
> Does it sounds good to you?

    No. The networking stack needs to know about the bad checksums too.

> Regards,
> Biju

>> [...]

MBR, Sergey