On Thu, 2017-06-01 at 12:39 +0200, Paolo Abeni wrote:
> On Wed, 2017-05-31 at 10:00 -0700, Eric Dumazet wrote:
> > On Mon, 2017-05-29 at 17:27 +0200, Paolo Abeni wrote:
> > > Since UDP no more uses sk->destructor, we can clear completely
> > > the skb head state before enqueuing.
> >
> > ...
> >
> > > @@ -1739,6 +1740,9 @@ static int __udp_queue_rcv_skb(struct sock *sk,
> > > struct sk_buff *skb)
> > > sk_mark_napi_id_once(sk, skb);
> > > }
> > >
> > > + /* drop all pending head states; dst, nf and sk are dropped by caller */
> > > + secpath_reset(skb);
> > > +
> >
> > I wonder if using skb_release_head_state() would be more appropriate ?
> >
> > Surely more descriptive and probably not more expensive since all
> > cache lines should be already hot at this point.
>
> Thank you for reviewing this.
>
> I would prefer not adding more code to the core, but I think we would
> need something new, like:
>
> skb_reset_head_state()
> {
> skb_dst_drop(skb);
> secpath_reset(skb);
> nf_reset(skb);
> skb_orphan(skb);
> }
>
> because elsewhere the skb could be in inconsistent state: skb->sp !=
> NULL but with its refcount is already decremented. WDYT?
I do not believe skb->sk is set anymore in UDP receive path.
If early demux sets skb->sk for a moment, skb_steal_sock() would set
skb->sk back to NULL
