netdev - Re: [PATCH v6 net-next 3/5] xdp: add multi-buff support for xdp running in generic mode

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Message-ID: <20240201071512.0fb7c5ee@kernel.org>
Date: Thu, 1 Feb 2024 07:15:12 -0800
From: Jakub Kicinski <kuba@...nel.org>
To: Lorenzo Bianconi <lorenzo@...nel.org>
Cc: netdev@...r.kernel.org, lorenzo.bianconi@...hat.com,
 davem@...emloft.net, edumazet@...gle.com, pabeni@...hat.com,
 bpf@...r.kernel.org, toke@...hat.com, willemdebruijn.kernel@...il.com,
 jasowang@...hat.com, sdf@...gle.com, hawk@...nel.org,
 ilias.apalodimas@...aro.org
Subject: Re: [PATCH v6 net-next 3/5] xdp: add multi-buff support for xdp
 running in generic mode

On Thu, 1 Feb 2024 12:34:26 +0100 Lorenzo Bianconi wrote:
> > nit: doesn't look all that related to a netif, I'd put it in skbuff.c  
> 
> ack, fine. skb_segment_for_xdp() in this case?

I think the closest thing we have now is skb_cow_data(),
so how about skb_cow_data_pp() or skb_cow_fragged() or
skb_cow_something? :)

I'm on the fence whether we should split the XDP-ness out.
I mean the only two xdp-related things are the headroom and
check for xdp_has_frags, so we could also:

skb_cow_data_pp(struct page_pool *pool, struct sk_buff **pskb,
		unsigned int headroom)
{
	...
}

skb_cow_data_xdp(struct page_pool *pool, struct sk_buff **pskb,
		 struct bpf_prog *prog)
{
	if (!prog->aux->xdp_has_frags)
		return -EINVAL;

	return skb_cow_data_pp(pool, pskb, XDP_PACKET_HEADROOM);
}


I think it'd increase the chances of reuse. But that's speculative 
so I'll let you decide if you prefer that or to keep it simple.