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

From: Simon Horman <[email-masked]>
Date: Tue, 1 Oct 2024 11:44:13 +0100

On Mon, Sep 30, 2024 at 11:36:40PM +0300, Sergey Shtylyov wrote:
> On 9/30/24 19:08, Paul Barker wrote:
> 
> > From: Paul Barker <[email-masked]>
> > 
> > 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 <[email-masked]>
> [...]
> 
> > 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/==/!=/?

A minor nit if the check stays in some form:
vlan_proto is big endian, while ETH_P_8021Q is host byte order.

> 
> >  		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
> 
>