Re: [PATCH v3 net-next v3 3/6] net: add code for TCP fraglist GRO

[Felix Fietkau]

On 26.04.24 10:21, Paolo Abeni wrote:
> On Fri, 2024-04-26 at 08:51 +0200, Felix Fietkau wrote:
> > This implements fraglist GRO similar to how it's handled in UDP, however
> > no functional changes are added yet. The next change adds a heuristic for
> > using fraglist GRO instead of regular GRO.
> >
> > Signed-off-by: Felix Fietkau <nbd@xxxxxxxx>
> > ---
> >  net/ipv4/tcp_offload.c   | 22 ++++++++++++++++++++++
> >  net/ipv6/tcpv6_offload.c |  9 +++++++++
> >  2 files changed, 31 insertions(+)
> >
> > diff --git a/net/ipv4/tcp_offload.c b/net/ipv4/tcp_offload.c
> > index c493e95e09a5..ffd6b7a4163a 100644
> > --- a/net/ipv4/tcp_offload.c
> > +++ b/net/ipv4/tcp_offload.c
> > @@ -332,6 +332,19 @@ struct sk_buff *tcp_gro_receive(struct list_head *head, struct sk_buff *skb)
> >  	flush |= (ntohl(th2->seq) + skb_gro_len(p)) ^ ntohl(th->seq);
> >  	flush |= skb_cmp_decrypted(p, skb);
> >  
> > +	if (NAPI_GRO_CB(p)->is_flist) {
> > +		flush |= (__force int)(flags ^ tcp_flag_word(th2));
> > +		flush |= skb->ip_summed != p->ip_summed;
> > +		flush |= skb->csum_level != p->csum_level;
> > +		flush |= !pskb_may_pull(skb, skb_gro_offset(skb));
>
> I'm sorry, I'm lagging behind. I think the TCP flags handling here is
> correct - preserving the original ones should work.
>
> The question a made WRT 2 above checks being non necessary/redundant:
>
> 		flush |= (__force int)(flags ^ tcp_flag_word(th2));

This one is not redundant, because the earlier flags check includes this 
part: & ~(TCP_FLAG_CWR | TCP_FLAG_FIN | TCP_FLAG_PSH))

> 		flush |= !pskb_may_pull(skb, skb_gro_offset(skb));

This one looks like a redundant leftover, I will remove it in the next 
version.

Thanks,

- Felix