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

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Date: Fri, 26 Apr 2024 10:21:23 +0200
From: Paolo Abeni <pabeni@...hat.com>
To: Felix Fietkau <nbd@....name>, netdev@...r.kernel.org, Eric Dumazet
 <edumazet@...gle.com>, "David S. Miller" <davem@...emloft.net>, David Ahern
 <dsahern@...nel.org>, Jakub Kicinski <kuba@...nel.org>
Cc: willemdebruijn.kernel@...il.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 net-next v3 3/6] net: add code for TCP fraglist GRO

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@....name>
> ---
>  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));
		flush |= !pskb_may_pull(skb, skb_gro_offset(skb));

still stands, I think.

Thanks,

Paolo