Subject: Re: [PATCH bpf-next 02/10] xsk: diversify return codes in xsk_rcv_check()

From: Maciej Fijalkowski <[email-masked]>
Date: Tue, 5 Apr 2022 15:35:44 +0200

On Tue, Apr 05, 2022 at 03:00:25PM +0200, Jesper Dangaard Brouer wrote:
> 
> 
> On 05/04/2022 13.06, Maciej Fijalkowski wrote:
> > Inspired by patch that made xdp_do_redirect() return values for XSKMAP
> > more meaningful, return -ENXIO instead of -EINVAL for socket being
> > unbound in xsk_rcv_check() as this is the usual value that is returned
> > for such event. In turn, it is now possible to easily distinguish what
> > went wrong, which is a bit harder when for both cases checked, -EINVAL
> > was returned.
> 
> I like this as it makes it easier to troubleshoot.
> Could you update the description to explain how to debug this easily.
> E.g. via this bpftrace one liner:
> 
> 
>  bpftrace -e 'tracepoint:xdp:xdp_redirect* {@err[-args->err] = count();}'

Nice one! I'll include this in the commit message of v2.

> 
> 
> > Signed-off-by: Maciej Fijalkowski <[email-masked]>
> > ---
> 
> Acked-by: Jesper Dangaard Brouer <[email-masked]>
> 
> >   net/xdp/xsk.c | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
> > index f75e121073e7..040c73345b7c 100644
> > --- a/net/xdp/xsk.c
> > +++ b/net/xdp/xsk.c
> > @@ -217,7 +217,7 @@ static bool xsk_is_bound(struct xdp_sock *xs)
> >   static int xsk_rcv_check(struct xdp_sock *xs, struct xdp_buff *xdp)
> >   {
> >   	if (!xsk_is_bound(xs))
> > -		return -EINVAL;
> > +		return -ENXIO;
> >   	if (xs->dev != xdp->rxq->dev || xs->queue_id != xdp->rxq->queue_index)
> >   		return -EINVAL;
> > 
>