From e35259a95331ae4a9146cc03ab49aad641cab957 Mon Sep 17 00:00:00 2001
From: Max Krasnyansky <maxk@qualcomm.com>
Date: Thu, 10 Jul 2008 16:59:11 -0700
Subject: tun: Persistent devices can get stuck in xoff state

The scenario goes like this. App stops reading from tun/tap.
TX queue gets full and driver does netif_stop_queue().
App closes fd and TX queue gets flushed as part of the cleanup.
Next time the app opens tun/tap and starts reading from it but
the xoff state is not cleared. We're stuck.
Normally xoff state is cleared when netdev is brought up. But
in the case of persistent devices this happens only during
initial setup.

The fix is trivial. If device is already up when an app opens
it we clear xoff state and that gets things moving again.

Signed-off-by: Max Krasnyansky <maxk@qualcomm.com>
Tested-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
---
 drivers/net/tun.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 7ab94c825b5..b9018bfa0a9 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -602,6 +602,12 @@ static int tun_set_iff(struct net *net, struct file *file, struct ifreq *ifr)
 	tun->attached = 1;
 	get_net(dev_net(tun->dev));
 
+	/* Make sure persistent devices do not get stuck in
+	 * xoff state.
+	 */
+	if (netif_running(tun->dev))
+		netif_wake_queue(tun->dev);
+
 	strcpy(ifr->ifr_name, tun->dev->name);
 	return 0;
 
-- 
cgit v1.2.3-70-g09d2