ipvlan: properly track tx_errors

Both ipvlan_process_v4_outbound() and ipvlan_process_v6_outbound()
increment dev->stats.tx_errors in case of errors.

Unfortunately there are two issues :

1) ipvlan_get_stats64() does not propagate dev->stats.tx_errors to user.

2) Increments are not atomic. KCSAN would complain eventually.

Use DEV_STATS_INC() to not miss an update, and change ipvlan_get_stats64()
to copy the value back to user.

Fixes: 2ad7bf3 ("ipvlan: Initial check-in of the IPVLAN driver.")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Mahesh Bandewar <maheshb@google.com>
Link: https://lore.kernel.org/r/20231026131446.3933175-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: edumazet

drivers/net/ipvlan/ipvlan_core.c

@@ -441,12 +441,12 @@ static int ipvlan_process_v4_outbound(struct sk_buff *skb)
 
 	err = ip_local_out(net, skb->sk, skb);
 	if (unlikely(net_xmit_eval(err)))
-		dev->stats.tx_errors++;
+		DEV_STATS_INC(dev, tx_errors);
 	else
 		ret = NET_XMIT_SUCCESS;
 	goto out;
 err:
-	dev->stats.tx_errors++;
+	DEV_STATS_INC(dev, tx_errors);
 	kfree_skb(skb);
 out:
 	return ret;
@@ -482,12 +482,12 @@ static int ipvlan_process_v6_outbound(struct sk_buff *skb)
 
 	err = ip6_local_out(net, skb->sk, skb);
 	if (unlikely(net_xmit_eval(err)))
-		dev->stats.tx_errors++;
+		DEV_STATS_INC(dev, tx_errors);
 	else
 		ret = NET_XMIT_SUCCESS;
 	goto out;
 err:
-	dev->stats.tx_errors++;
+	DEV_STATS_INC(dev, tx_errors);
 	kfree_skb(skb);
 out:
 	return ret;

drivers/net/ipvlan/ipvlan_main.c

@@ -324,6 +324,7 @@ static void ipvlan_get_stats64(struct net_device *dev,
 		s->rx_dropped = rx_errs;
 		s->tx_dropped = tx_drps;
 	}
+	s->tx_errors = DEV_STATS_READ(dev, tx_errors);
 }
 
 static int ipvlan_vlan_rx_add_vid(struct net_device *dev, __be16 proto, u16 vid)