Re: [PATCH net-next v3 1/4] net: hdlc_fr: Simpify fr_rx by using "goto rx_drop" to drop frames

[Willem de Bruijn]

On Wed, Oct 28, 2020 at 6:01 PM Xie He <xie.he.0141@xxxxxxxxx> wrote:
>
> When the fr_rx function drops a received frame (because the protocol type
> is not supported, or because the PVC virtual device that corresponds to
> the DLCI number and the protocol type doesn't exist), the function frees
> the skb and returns.
>
> The code for freeing the skb and returning is repeated several times, this
> patch uses "goto rx_drop" to replace them so that the code looks cleaner.
>
> Also add code to increase the stats.rx_dropped count whenever we drop a
> frame.
>
> Cc: Krzysztof Halasa <khc@xxxxxxxxx>
> Signed-off-by: Xie He <xie.he.0141@xxxxxxxxx>
> ---
>  drivers/net/wan/hdlc_fr.c | 16 +++++++---------
>  1 file changed, 7 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/net/wan/hdlc_fr.c b/drivers/net/wan/hdlc_fr.c
> index 409e5a7ad8e2..c774eff44534 100644
> --- a/drivers/net/wan/hdlc_fr.c
> +++ b/drivers/net/wan/hdlc_fr.c
> @@ -904,8 +904,7 @@ static int fr_rx(struct sk_buff *skb)
>                 netdev_info(frad, "No PVC for received frame's DLCI %d\n",
>                             dlci);
>  #endif
> -               dev_kfree_skb_any(skb);
> -               return NET_RX_DROP;
> +               goto rx_drop;
>         }
>
>         if (pvc->state.fecn != fh->fecn) {
> @@ -963,14 +962,12 @@ static int fr_rx(struct sk_buff *skb)
>                 default:
>                         netdev_info(frad, "Unsupported protocol, OUI=%x PID=%x\n",
>                                     oui, pid);
> -                       dev_kfree_skb_any(skb);
> -                       return NET_RX_DROP;
> +                       goto rx_drop;
>                 }
>         } else {
>                 netdev_info(frad, "Unsupported protocol, NLPID=%x length=%i\n",
>                             data[3], skb->len);
> -               dev_kfree_skb_any(skb);
> -               return NET_RX_DROP;
> +               goto rx_drop;
>         }
>
>         if (dev) {
> @@ -982,12 +979,13 @@ static int fr_rx(struct sk_buff *skb)
>                 netif_rx(skb);
>                 return NET_RX_SUCCESS;
>         } else {
> -               dev_kfree_skb_any(skb);
> -               return NET_RX_DROP;
> +               goto rx_drop;
>         }
>
> - rx_error:
> +rx_error:
>         frad->stats.rx_errors++; /* Mark error */
> +rx_drop:
> +       frad->stats.rx_dropped++;
>         dev_kfree_skb_any(skb);
>         return NET_RX_DROP;

This does change rx_dropped count on errors. Not sure how important
that is. But perhaps good to call out in the commit explicitly if it's
intentional.