can: dev: __can_get_echo_skb(): fix real payload length return value …

…for RTR frames [ Upstream commit ed3320cec279407a86bc4c72edc4a39eb49165ec ] The can_get_echo_skb() function returns the number of received bytes to be used for netdev statistics. In the case of RTR frames we get a valid (potential non-zero) data length value which has to be passed for further operations. But on the wire RTR frames have no payload length. Therefore the value to be used in the statistics has to be zero for RTR frames. Reported-by: Vincent Mailhol <[email protected]> Signed-off-by: Oliver Hartkopp <[email protected]> Link: https://lore.kernel.org/r/[email protected] Fixes: cf5046b ("can: dev: let can_get_echo_skb() return dlc of CAN frame") Signed-off-by: Marc Kleine-Budde <[email protected]> Signed-off-by: Sasha Levin <[email protected]>
kimocoder · Dec 3, 2021 · 483d55f · 483d55f
1 parent 468cb84
commit 483d55f
Showing 1 changed file with 6 additions and 2 deletions.
diff --git a/drivers/net/can/dev.c b/drivers/net/can/dev.c
@@ -469,9 +469,13 @@ struct sk_buff *__can_get_echo_skb(struct net_device *dev, unsigned int idx, u8
 		 */
 		struct sk_buff *skb = priv->echo_skb[idx];
 		struct canfd_frame *cf = (struct canfd_frame *)skb->data;
-		u8 len = cf->len;
 
-		*len_ptr = len;
+		/* get the real payload length for netdev statistics */
+		if (cf->can_id & CAN_RTR_FLAG)
+			*len_ptr = 0;
+		else
+			*len_ptr = cf->len;
+
 		priv->echo_skb[idx] = NULL;
 
 		return skb;