netdev - Re: [PATCH bpf-next 02/10] xsk: diversify return codes in xsk_rcv

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Date:   Tue, 5 Apr 2022 15:00:25 +0200
From:   Jesper Dangaard Brouer <jbrouer@...hat.com>
To:     Maciej Fijalkowski <maciej.fijalkowski@...el.com>,
        bpf@...r.kernel.org, ast@...nel.org, daniel@...earbox.net,
        magnus.karlsson@...el.com, bjorn@...nel.org
Cc:     brouer@...hat.com, netdev@...r.kernel.org, maximmi@...dia.com,
        alexandr.lobakin@...el.com
Subject: Re: [PATCH bpf-next 02/10] xsk: diversify return codes in
 xsk_rcv_check()



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();}'


> Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@...el.com>
> ---

Acked-by: Jesper Dangaard Brouer <brouer@...hat.com>

>   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;
>