vxcan: remove sk reference in peer skb

With can_create_echo_skb() the skb which is forwarded to the peer CAN
interface shares the sk pointer from the originating socket.
This makes the CAN frame show up in the peer namespace as a TX packet.

With the use of skb_clone() analogue to the handling in gw.c the peer
skb gets a new start in the peer namespace and correctly appears as
a RX packet.

Link: https://lore.kernel.org/all/20220309120416.83514-4-socketcan@hartkopp.net
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

drivers/net/can/vxcan.c

@@ -33,28 +33,33 @@ struct vxcan_priv {
 	struct net_device __rcu	*peer;
 };
 
-static netdev_tx_t vxcan_xmit(struct sk_buff *skb, struct net_device *dev)
+static netdev_tx_t vxcan_xmit(struct sk_buff *oskb, struct net_device *dev)
 {
 	struct vxcan_priv *priv = netdev_priv(dev);
 	struct net_device *peer;
-	struct canfd_frame *cfd = (struct canfd_frame *)skb->data;
+	struct canfd_frame *cfd = (struct canfd_frame *)oskb->data;
 	struct net_device_stats *peerstats, *srcstats = &dev->stats;
+	struct sk_buff *skb;
 	u8 len;
 
-	if (can_dropped_invalid_skb(dev, skb))
+	if (can_dropped_invalid_skb(dev, oskb))
 		return NETDEV_TX_OK;
 
 	rcu_read_lock();
 	peer = rcu_dereference(priv->peer);
 	if (unlikely(!peer)) {
-		kfree_skb(skb);
+		kfree_skb(oskb);
 		dev->stats.tx_dropped++;
 		goto out_unlock;
 	}
 
-	skb = can_create_echo_skb(skb);
-	if (!skb)
+	skb = skb_clone(oskb, GFP_ATOMIC);
+	if (skb) {
+		consume_skb(oskb);
+	} else {
+		kfree(oskb);
 		goto out_unlock;
+	}
 
 	/* reset CAN GW hop counter */
 	skb->csum_start = 0;