macvlan: allow to enqueue broadcast pkt on virtual device

Since commit 412ca1550cbe ("macvlan: Move broadcasts into a work queue"), the
driver uses tx_queue_len of the master device as the limit of packets enqueuing.
Problem is that virtual drivers have this value set to 0, thus all broadcast
packets were rejected.
Because tx_queue_len was arbitrarily chosen, I replace it with a static limit
of 1000 (also arbitrarily chosen).

CC: Herbert Xu <herbert@gondor.apana.org.au>
Reported-by: Thibaut Collet <thibaut.collet@6wind.com>
Suggested-by: Thibaut Collet <thibaut.collet@6wind.com>
Tested-by: Thibaut Collet <thibaut.collet@6wind.com>
Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Acked-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/macvlan.c

@@ -36,6 +36,7 @@
 #include <linux/netpoll.h>
 
 #define MACVLAN_HASH_SIZE	(1 << BITS_PER_BYTE)
+#define MACVLAN_BC_QUEUE_LEN	1000
 
 struct macvlan_port {
 	struct net_device	*dev;
@@ -248,7 +249,7 @@ static void macvlan_broadcast_enqueue(struct macvlan_port *port,
 		goto err;
 
 	spin_lock(&port->bc_queue.lock);
-	if (skb_queue_len(&port->bc_queue) < skb->dev->tx_queue_len) {
+	if (skb_queue_len(&port->bc_queue) < MACVLAN_BC_QUEUE_LEN) {
 		__skb_queue_tail(&port->bc_queue, nskb);
 		err = 0;
 	}