[PATCH net v3] tun: add missing rx stats accounting in tun_xdp_act

[Yunjian Wang]

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.

Fixes: 8ae1aff0b331 ("tuntap: split out XDP logic")
Signed-off-by: Yunjian Wang <wangyunjian@xxxxxxxxxx>
---
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);
+	}
+
 	return act;
 }
 
-- 
2.41.0