linux-kernel - Re: [net-next PATCH 11/11] net: ravb: Add VLAN checksum support

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Message-ID: <2664c044-bb38-44f0-821e-28d813589d15@omp.ru>
Date: Tue, 1 Oct 2024 01:32:39 +0300
From: Sergey Shtylyov <s.shtylyov@....ru>
To: Paul Barker <paul@...rker.dev>, "David S . Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo
 Abeni <pabeni@...hat.com>
CC: Paul Barker <paul.barker.ct@...renesas.com>, Geert Uytterhoeven
	<geert+renesas@...der.be>, Niklas Söderlund
	<niklas.soderlund+renesas@...natech.se>, Biju Das
	<biju.das.jz@...renesas.com>, Claudiu Beznea
	<claudiu.beznea.uj@...renesas.com>, <netdev@...r.kernel.org>,
	<linux-renesas-soc@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [net-next PATCH 11/11] net: ravb: Add VLAN checksum support

On 9/30/24 23:36, Sergey Shtylyov wrote:
[...]

>> From: Paul Barker <paul.barker.ct@...renesas.com>
>>
>> The GbEth IP supports offloading checksum calculation for VLAN-tagged
>> packets, provided that the EtherType is 0x8100 and only one VLAN tag is
>> present.
>>
>> Signed-off-by: Paul Barker <paul.barker.ct@...renesas.com>
> [...]
> 
>> diff --git a/drivers/net/ethernet/renesas/ravb_main.c b/drivers/net/ethernet/renesas/ravb_main.c
>> index 832132d44fb4..eb7499d42a9b 100644
>> --- a/drivers/net/ethernet/renesas/ravb_main.c
>> +++ b/drivers/net/ethernet/renesas/ravb_main.c
>> @@ -2063,11 +2063,30 @@ static void ravb_tx_timeout_work(struct work_struct *work)
[...]
>> -	switch (ntohs(skb->protocol)) {
>> +	if (net_protocol == ETH_P_8021Q) {
>> +		struct vlan_hdr vhdr, *vh;
>> +
>> +		vh = skb_header_pointer(skb, ETH_HLEN, sizeof(vhdr), &vhdr);
> 
>    Hm, I thought the VLAN header starts at ETH_HLEN - 2, not at ETH_HLEN...

    Wikipedia indeed says that the VLAN header begins with TPID word (0x8100)
and then the TCI word follows -- while in Linux, *struct* vlan_hgr starts with
the TCI word -- hence my confusion... :-)

> [...]

MBR, Sergey