Merge branch 'IFF_NO_QUEUE-semantics'

Jesper Dangaard Brouer says:

====================
qdisc and tx_queue_len cleanups for IFF_NO_QUEUE devices

This patchset is a cleanup for IFF_NO_QUEUE devices.  It will
hopefully help userspace get a more consistent behavior when attaching
qdisc to such virtual devices.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/pkt_sched.h

@@ -6,6 +6,8 @@
 #include <linux/if_vlan.h>
 #include <net/sch_generic.h>
 
+#define DEFAULT_TX_QUEUE_LEN	1000
+
 struct qdisc_walker {
 	int	stop;
 	int	skip;

net/core/dev.c

@@ -7651,7 +7651,7 @@ struct net_device *alloc_netdev_mqs(int sizeof_priv, const char *name,
 
 	if (!dev->tx_queue_len) {
 		dev->priv_flags |= IFF_NO_QUEUE;
-		dev->tx_queue_len = 1;
+		dev->tx_queue_len = DEFAULT_TX_QUEUE_LEN;
 	}
 
 	dev->num_tx_queues = txqs;

net/ethernet/eth.c

@@ -62,6 +62,7 @@
 #include <net/dsa.h>
 #include <net/flow_dissector.h>
 #include <linux/uaccess.h>
+#include <net/pkt_sched.h>
 
 __setup("ether=", netdev_boot_setup);
 
@@ -359,7 +360,7 @@ void ether_setup(struct net_device *dev)
 	dev->min_mtu		= ETH_MIN_MTU;
 	dev->max_mtu		= ETH_DATA_LEN;
 	dev->addr_len		= ETH_ALEN;
-	dev->tx_queue_len	= 1000;	/* Ethernet wants good queues */
+	dev->tx_queue_len	= DEFAULT_TX_QUEUE_LEN;
 	dev->flags		= IFF_BROADCAST|IFF_MULTICAST;
 	dev->priv_flags		|= IFF_TX_SKB_SHARING;
 

net/sched/sch_api.c

@@ -960,6 +960,17 @@ static struct Qdisc *qdisc_create(struct net_device *dev,
 
 	sch->handle = handle;
 
+	/* This exist to keep backward compatible with a userspace
+	 * loophole, what allowed userspace to get IFF_NO_QUEUE
+	 * facility on older kernels by setting tx_queue_len=0 (prior
+	 * to qdisc init), and then forgot to reinit tx_queue_len
+	 * before again attaching a qdisc.
+	 */
+	if ((dev->priv_flags & IFF_NO_QUEUE) && (dev->tx_queue_len == 0)) {
+		dev->tx_queue_len = DEFAULT_TX_QUEUE_LEN;
+		netdev_info(dev, "Caught tx_queue_len zero misconfig\n");
+	}
+
 	if (!ops->init || (err = ops->init(sch, tca[TCA_OPTIONS])) == 0) {
 		if (qdisc_is_percpu_stats(sch)) {
 			sch->cpu_bstats =