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Message-ID: <65a7f560a4643_6ba59294a7@willemb.c.googlers.com.notmuch>
Date: Wed, 17 Jan 2024 10:42:24 -0500
From: Willem de Bruijn <willemdebruijn.kernel@...il.com>
To: Yunjian Wang <wangyunjian@...wei.com>,
willemdebruijn.kernel@...il.com,
jasowang@...hat.com,
kuba@...nel.org,
davem@...emloft.net
Cc: netdev@...r.kernel.org,
linux-kernel@...r.kernel.org,
xudingke@...wei.com,
Yunjian Wang <wangyunjian@...wei.com>
Subject: Re: [PATCH net v3] tun: add missing rx stats accounting in
tun_xdp_act
Yunjian Wang wrote:
> The TUN can be used as vhost-net backend, and it is necessary to count
> the packets transmitted from TUN to vhost-net/virtio-net. However, there
> are some places in the receive path that were not taken into account
> when using XDP. The commit 8ae1aff0b331 ("tuntap: split out XDP logic")
> only includes dropped counter for XDP_DROP, XDP_ABORTED, and invalid
> XDP actions. It would be beneficial to also include new accounting for
> successfully received bytes using dev_sw_netstats_rx_add and introduce
> new dropped counter for XDP errors on XDP_TX and XDP_REDIRECT.
>From the description it is clear that these are two separate changes
wrapped into one patch. I should have flagged this previously.
Ack on returning the error counter that was previously present and
matches the Fixes tag.
For the second change, I had to check a few other XDP capable drivers
to verify that it is indeed common to count such packets.
> Fixes: 8ae1aff0b331 ("tuntap: split out XDP logic")
> Signed-off-by: Yunjian Wang <wangyunjian@...wei.com>
> ---
> v3: update commit log and code
> v2: add Fixes tag
> ---
> drivers/net/tun.c | 14 +++++++++-----
> 1 file changed, 9 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/net/tun.c b/drivers/net/tun.c
> index afa5497f7c35..0704a17e74e1 100644
> --- a/drivers/net/tun.c
> +++ b/drivers/net/tun.c
> @@ -1625,18 +1625,15 @@ static struct sk_buff *__tun_build_skb(struct tun_file *tfile,
> static int tun_xdp_act(struct tun_struct *tun, struct bpf_prog *xdp_prog,
> struct xdp_buff *xdp, u32 act)
> {
> - int err;
> + unsigned int datasize = xdp->data_end - xdp->data;
> + int err = 0;
>
> switch (act) {
> case XDP_REDIRECT:
> err = xdp_do_redirect(tun->dev, xdp, xdp_prog);
> - if (err)
> - return err;
> break;
> case XDP_TX:
> err = tun_xdp_tx(tun->dev, xdp);
> - if (err < 0)
> - return err;
> break;
> case XDP_PASS:
> break;
> @@ -1651,6 +1648,13 @@ static int tun_xdp_act(struct tun_struct *tun, struct bpf_prog *xdp_prog,
> break;
> }
>
> + if (err < 0) {
> + act = err;
> + dev_core_stats_rx_dropped_inc(tun->dev);
> + } else if (act == XDP_REDIRECT || act == XDP_TX) {
> + dev_sw_netstats_rx_add(tun->dev, datasize);
> + }
> +
Let's avoid adding yet another branch and just do these operations in
the case statements, like XDP_DROP.
> return act;
> }
>
> --
> 2.41.0
>
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