Yang Huajian（杨华健） <huajianyang@xxxxxxxxxxxx> wrote:
> > if (skb_headroom(skb) < ll_rs)
> > goto expand_headroom;
>
> > ... but I'm not sure what the actual problem is.
>
> Yes, your guess is correct!
>
> Actual problem: I think it is unreasonable to directly drop skb with insufficient headroom.
>
> > Why does this need to make a full skb copy?
> > Should that be using skb_expand_head()?
>
> Using skb_expand_head has the same effect.
> > Actually, can't you just (re)use the slowpath for the skb_headroom < ll_rs case instead of adding headroom expansion?
>
> I tested it just now, reuse the slowpath will successed.
> But maybe this change cannot resolve all cases if the netdevice really needs this headroom.
The slowpath considers headroom requirements, see ip_frag_next():
skb2 = alloc_skb(len + state->hlen + state->ll_rs, GFP_ATOMIC);
You should wait for more feedback and then send a v2 tomorrow.
Thanks!
