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

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Message-ID: <ab7482f9-6833-416f-8adf-5e1347628dec@omp.ru>
Date: Mon, 30 Sep 2024 23:36:40 +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 19:08, Paul Barker 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)
>  
>  static bool ravb_can_tx_csum_gbeth(struct sk_buff *skb)
>  {
> -	/* TODO: Need to add support for VLAN tag 802.1Q */
> -	if (skb_vlan_tag_present(skb))
> +	u16 net_protocol = ntohs(skb->protocol);
> +
> +	/* GbEth IP can calculate the checksum if:
> +	 * - there are zero or one VLAN headers with TPID=0x8100
> +	 * - the network protocol is IPv4 or IPv6
> +	 * - the transport protocol is TCP, UDP or ICMP
> +	 * - the packet is not fragmented
> +	 */
> +
> +	if (skb_vlan_tag_present(skb) &&
> +	    (skb->vlan_proto != ETH_P_8021Q || net_protocol == ETH_P_8021Q))

   Not sure I understand this check... Maybe s/==/!=/?

>  		return false;
>  
> -	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...

[...]

MBR, Sergey