RE: [PATCH v2 net-next 2/5] net: enetc: add Tx checksum offload for i.MX95 ENETC

[Wei Fang]

> > --- a/drivers/net/ethernet/freescale/enetc/enetc.c
> > +++ b/drivers/net/ethernet/freescale/enetc/enetc.c
> > @@ -143,6 +143,27 @@ static int enetc_ptp_parse(struct sk_buff *skb, u8
> > *udp,
> >  	return 0;
> >  }
> >
> > +static bool enetc_tx_csum_offload_check(struct sk_buff *skb)
> > +{
> > +	if (ip_hdr(skb)->version == 4)
> 
> I would avoid using ip_hdr(), or any form of touching packed data and try
> extract this kind of info directly from the skb metadata instead, see also
> comment below.
> 
> i.e., why not:
> if (skb->protocol == htons(ETH_P_IPV6)) ..  etc. ?

skb->protocol may be VLAN protocol, such as ETH_P_8021Q, ETH_P_8021AD.
If so, it is impossible to determine whether it is an IPv4 or IPv6 frames through
protocol.

> or
> switch (skb->csum_offset) {
> case offsetof(struct tcphdr, check):
> [...]
> case offsetof(struct udphdr, check):
> [...]

This seems to be able to be used to determine whether it is a UDP or TCP frame.
Thanks.

> 
> > +		return ip_hdr(skb)->protocol == IPPROTO_TCP ||
> > +		       ip_hdr(skb)->protocol == IPPROTO_UDP;
> > +
> > +	if (ip_hdr(skb)->version == 6)
> > +		return ipv6_hdr(skb)->nexthdr == NEXTHDR_TCP ||
> > +		       ipv6_hdr(skb)->nexthdr == NEXTHDR_UDP;
> > +
> > +	return false;
> > +}
> > +
> > +static bool enetc_skb_is_tcp(struct sk_buff *skb)
> > +{
> 
> There is a more efficient way of checking if L4 is TCP, without touching
> packet data, i.e. through the 'csum_offset' skb field:
> return skb->csum_offset == offsetof(struct tcphdr, check);
> 
> Pls. have a look at these optimizations, I would expect visible improvements
> in throughput. Thanks.

For small packets this might improve performance, but I'm not sure if it would be
a significant improvement. :)

> 
> > +	if (ip_hdr(skb)->version == 4)
> > +		return ip_hdr(skb)->protocol == IPPROTO_TCP;
> > +	else
> > +		return ipv6_hdr(skb)->nexthdr == NEXTHDR_TCP;
> > +}
> > +