Phonet: return an error when packet TX fails

Phonet assumes that packets are never dropped. We try our best to
avoid this situation. But lets return ENOBUFS if queueing to the
network device fails so that the caller knows things went wrong.
Signed-off-by: NRémi Denis-Courmont <remi.denis-courmont@nokia.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/phonet/af_phonet.c

@@ -195,11 +195,7 @@ static int pn_send(struct sk_buff *skb, struct net_device *dev,
 	if (skb->pkt_type == PACKET_LOOPBACK) {
 		skb_reset_mac_header(skb);
 		skb_orphan(skb);
-		if (irq)
-			netif_rx(skb);
-		else
-			netif_rx_ni(skb);
-		err = 0;
+		err = (irq ? netif_rx(skb) : netif_rx_ni(skb)) ? -ENOBUFS : 0;
 	} else {
 		err = dev_hard_header(skb, dev, ntohs(skb->protocol),
 					NULL, NULL, skb->len);
@@ -208,6 +204,8 @@ static int pn_send(struct sk_buff *skb, struct net_device *dev,
 			goto drop;
 		}
 		err = dev_queue_xmit(skb);
+		if (unlikely(err > 0))
+			err = net_xmit_errno(err);
 	}
 
 	return err;