On Saturday, January 26, 2013 11:29:49 AM Toralf Förster wrote: > With kernel 3.8. I just realized that all pre-defined TAP devices are > RUNNING even if no virtual linux system is using it. Now I'm wondering > whether this is a new feature of the upcoming kernel, a bug of the old - > and how I can avoid that. > > Background : When I start a user mode linux instance, I currently grep > for the next free tap device in this way : > > Code: > for t in $(ifconfig | grep "^tap" | cut -f1 -d:) > do > ethtool $t | grep -q 'Link detected: no' > if [[ $? -eq 0 ]]; then > NET="tuntap,$t" > break > fi > done > > but this doesn't work now anymore. > > Here is the diff in dmesg > > $ diff 3.7.1 3.8.0-rc1+ | grep UP > > < br0: flags=4355<UP,BROADCAST,PROMISC,MULTICAST> mtu 1500 > > > br0: flags=4419<UP,BROADCAST,RUNNING,PROMISC,MULTICAST> mtu 1500 > > < tap0: flags=4099<UP,BROADCAST,MULTICAST> mtu 1500 > > > tap0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500 > > more details : http://forums.gentoo.org/viewtopic-p-7211498.html#7211498
Looks like something wrong with the carrier detection of tap.
Please try the following patch to see if it helps.
Thanks.
diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index cc09b67..d8a53c3 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -438,6 +438,9 @@ static void __tun_detach(struct tun_file *tfile, bool clean)
sock_put(&tfile->sk);
}
+ if (tun && tun->numqueues == 0)
+ netif_carrier_off(tun->dev);
+
if (clean) {
if (tun && tun->numqueues == 0 && tun->numdisabled == 0 &&
!(tun->flags & TUN_PERSIST))
@@ -473,6 +476,7 @@ static void tun_detach_all(struct net_device *dev)
BUG_ON(tun->numqueues != 0);
synchronize_net();
+ netif_carrier_off(dev);
for (i = 0; i < n; i++) {
tfile = rtnl_dereference(tun->tfiles[i]);
/* Drop read queue */
@@ -531,6 +535,7 @@ static int tun_attach(struct tun_struct *tun, struct file
*file)
sock_hold(&tfile->sk);
tun_set_real_num_queues(tun);
+ netif_carrier_on(tun->dev);
/* device is allowed to go away first, so no need to hold extra
* refcnt.
--
1.7.1
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