Patch "can: kvaser_usb: do not increase tx statistics when sending error message frames" has been added to the 5.10-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    can: kvaser_usb: do not increase tx statistics when sending error message frames

to the 5.10-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     can-kvaser_usb-do-not-increase-tx-statistics-when-se.patch
and it can be found in the queue-5.10 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 719eb15056fdef2f8246f173092142a957335193
Author: Vincent Mailhol <mailhol.vincent@xxxxxxxxxx>
Date:   Tue Dec 7 21:15:28 2021 +0900

    can: kvaser_usb: do not increase tx statistics when sending error message frames
    
    [ Upstream commit 0b0ce2c67795672115ac6ca28351a78799cd114b ]
    
    The CAN error message frames (i.e. error skb) are an interface
    specific to socket CAN. The payload of the CAN error message frames
    does not correspond to any actual data sent on the wire. Only an error
    flag and a delimiter are transmitted when an error occurs (c.f. ISO
    11898-1 section 10.4.4.2 "Error flag").
    
    For this reason, it makes no sense to increment the tx_packets and
    tx_bytes fields of struct net_device_stats when sending an error
    message frame because no actual payload will be transmitted on the
    wire.
    
    N.B. Sending error message frames is a very specific feature which, at
    the moment, is only supported by the Kvaser Hydra hardware. Please
    refer to [1] for more details on the topic.
    
    [1] https://lore.kernel.org/linux-can/CAMZ6RqK0rTNg3u3mBpZOoY51jLZ-et-J01tY6-+mWsM4meVw-A@xxxxxxxxxxxxxx/t/#u
    
    Link: https://lore.kernel.org/all/20211207121531.42941-3-mailhol.vincent@xxxxxxxxxx
    Co-developed-by: Jimmy Assarsson <extja@xxxxxxxxxx>
    Signed-off-by: Jimmy Assarsson <extja@xxxxxxxxxx>
    Signed-off-by: Vincent Mailhol <mailhol.vincent@xxxxxxxxxx>
    Signed-off-by: Marc Kleine-Budde <mkl@xxxxxxxxxxxxxx>
    Stable-dep-of: 35364f5b41a4 ("can: kvaser_usb: kvaser_usb_leaf: Get capabilities from device")
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/net/can/usb/kvaser_usb/kvaser_usb_hydra.c b/drivers/net/can/usb/kvaser_usb/kvaser_usb_hydra.c
index 45d278724883..9588efbfae71 100644
--- a/drivers/net/can/usb/kvaser_usb/kvaser_usb_hydra.c
+++ b/drivers/net/can/usb/kvaser_usb/kvaser_usb_hydra.c
@@ -293,6 +293,7 @@ struct kvaser_cmd {
 #define KVASER_USB_HYDRA_CF_FLAG_OVERRUN	BIT(1)
 #define KVASER_USB_HYDRA_CF_FLAG_REMOTE_FRAME	BIT(4)
 #define KVASER_USB_HYDRA_CF_FLAG_EXTENDED_ID	BIT(5)
+#define KVASER_USB_HYDRA_CF_FLAG_TX_ACK		BIT(6)
 /* CAN frame flags. Used in ext_rx_can and ext_tx_can */
 #define KVASER_USB_HYDRA_CF_FLAG_OSM_NACK	BIT(12)
 #define KVASER_USB_HYDRA_CF_FLAG_ABL		BIT(13)
@@ -1099,6 +1100,7 @@ static void kvaser_usb_hydra_tx_acknowledge(const struct kvaser_usb *dev,
 	struct kvaser_usb_net_priv *priv;
 	unsigned long irq_flags;
 	bool one_shot_fail = false;
+	bool is_err_frame = false;
 	u16 transid = kvaser_usb_hydra_get_cmd_transid(cmd);
 
 	priv = kvaser_usb_hydra_net_priv_from_cmd(dev, cmd);
@@ -1117,10 +1119,13 @@ static void kvaser_usb_hydra_tx_acknowledge(const struct kvaser_usb *dev,
 			kvaser_usb_hydra_one_shot_fail(priv, cmd_ext);
 			one_shot_fail = true;
 		}
+
+		is_err_frame = flags & KVASER_USB_HYDRA_CF_FLAG_TX_ACK &&
+			       flags & KVASER_USB_HYDRA_CF_FLAG_ERROR_FRAME;
 	}
 
 	context = &priv->tx_contexts[transid % dev->max_tx_urbs];
-	if (!one_shot_fail) {
+	if (!one_shot_fail && !is_err_frame) {
 		struct net_device_stats *stats = &priv->netdev->stats;
 
 		stats->tx_packets++;