Re: [PATCH bpf-next 2/3] veth: rework veth_xdp_rcv_skb in order to accept non-linear skb

On Sat, 12 Feb 2022 12:03:49 +0100 Lorenzo Bianconi wrote:

On Feb 11, Jakub Kicinski wrote:

quoted

On Fri, 11 Feb 2022 02:20:31 +0100 Lorenzo Bianconi wrote:  

quoted

+	if (skb_shared(skb) || skb_head_is_locked(skb)) {  

Is this sufficient to guarantee that the frags can be written?
skb_cow_data() tells a different story.  

Do you mean to consider paged part of the skb always not writable, right?
In other words, we should check something like:

	if (skb_shared(skb) || skb_head_is_locked(skb) ||
	    skb_shinfo(skb)->nr_frags) {
	    ...
	}

Yes, we do have skb_has_shared_frag() but IDK if it guarantees frags
are writable :S