* How to find an unused TAP device with kernel 3.8 ?
@ 2013-01-26 10:29 Toralf Förster
2013-01-28 9:38 ` Jason Wang
0 siblings, 1 reply; 7+ messages in thread
From: Toralf Förster @ 2013-01-26 10:29 UTC (permalink / raw)
To: netdev; +Cc: Linux Kernel
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
--
MfG/Sincerely
Toralf Förster
pgp finger print: 7B1A 07F4 EC82 0F90 D4C2 8936 872A E508 7DB6 9DA3
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: How to find an unused TAP device with kernel 3.8 ?
2013-01-26 10:29 How to find an unused TAP device with kernel 3.8 ? Toralf Förster
@ 2013-01-28 9:38 ` Jason Wang
2013-01-28 10:11 ` [PATCH] tun: fix carrier on/off status Michael S. Tsirkin
0 siblings, 1 reply; 7+ messages in thread
From: Jason Wang @ 2013-01-28 9:38 UTC (permalink / raw)
To: Toralf Förster; +Cc: netdev, Linux Kernel
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
^ permalink raw reply related [flat|nested] 7+ messages in thread
* [PATCH] tun: fix carrier on/off status
2013-01-28 9:38 ` Jason Wang
@ 2013-01-28 10:11 ` Michael S. Tsirkin
2013-01-28 10:38 ` [PATCHv2] " Michael S. Tsirkin
0 siblings, 1 reply; 7+ messages in thread
From: Michael S. Tsirkin @ 2013-01-28 10:11 UTC (permalink / raw)
To: Jason Wang; +Cc: Toralf Förster, netdev, Linux Kernel, David Miller
Commit c8d68e6be1c3b242f1c598595830890b65cea64a removed carrier off call
from tun_detach since it's now called on queue disable and not only on
tun close. This confuses userspace which used this flag to detect a
free tun. To fix, move on/off calls to setiff/close respectively.
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
On Mon, Jan 28, 2013 at 05:38:24PM +0800, Jason Wang wrote:
> On Saturday, January 26, 2013 11:29:49 AM Toralf Förster wrote:
> > Re: How to find an unused TAP device with kernel 3.8 ?
> > 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.
This will set carrier off if all queues are disabled, which I think is a
problem as it would confuse the script. How about the following instead:
diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index af372d0..00dfdad 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -1644,10 +1644,10 @@ static int tun_set_iff(struct net *net, struct file *file, struct ifreq *ifr)
device_create_file(&tun->dev->dev, &dev_attr_owner) ||
device_create_file(&tun->dev->dev, &dev_attr_group))
pr_err("Failed to create tun sysfs files\n");
-
- netif_carrier_on(tun->dev);
}
+ netif_carrier_on(tun->dev);
+
tun_debug(KERN_INFO, tun, "tun_set_iff\n");
if (ifr->ifr_flags & IFF_NO_PI)
@@ -2124,6 +2124,8 @@ static int tun_chr_close(struct inode *inode, struct file *file)
struct tun_file *tfile = file->private_data;
struct net *net = tfile->net;
+ netif_carrier_off(tun->dev);
+
tun_detach(tfile, true);
put_net(net);
--
MST
^ permalink raw reply related [flat|nested] 7+ messages in thread
* [PATCHv2] tun: fix carrier on/off status
2013-01-28 10:11 ` [PATCH] tun: fix carrier on/off status Michael S. Tsirkin
@ 2013-01-28 10:38 ` Michael S. Tsirkin
2013-01-28 11:00 ` Jason Wang
` (2 more replies)
0 siblings, 3 replies; 7+ messages in thread
From: Michael S. Tsirkin @ 2013-01-28 10:38 UTC (permalink / raw)
To: Jason Wang; +Cc: Toralf Förster, netdev, Linux Kernel, David Miller
Commit c8d68e6be1c3b242f1c598595830890b65cea64a removed carrier off call
from tun_detach since it's now called on queue disable and not only on
tun close. This confuses userspace which used this flag to detect a
free tun. To fix, put this back but under if (clean).
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
Changes from v1:
Don't set carrier off unless all queues are closed.
Note: didn't test in MQ mode - Jason, care checking this does the
right thing there?
diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index af372d0..06b2723 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -434,10 +434,13 @@ static void __tun_detach(struct tun_file *tfile, bool clean)
}
if (clean) {
- if (tun && tun->numqueues == 0 && tun->numdisabled == 0 &&
- !(tun->flags & TUN_PERSIST))
- if (tun->dev->reg_state == NETREG_REGISTERED)
+ if (tun && tun->numqueues == 0 && tun->numdisabled == 0) {
+ netif_carrier_off(tun->dev);
+
+ if (!(tun->flags & TUN_PERSIST) &&
+ tun->dev->reg_state == NETREG_REGISTERED)
unregister_netdevice(tun->dev);
+ }
BUG_ON(!test_bit(SOCK_EXTERNALLY_ALLOCATED,
&tfile->socket.flags));
@@ -1644,10 +1647,10 @@ static int tun_set_iff(struct net *net, struct file *file, struct ifreq *ifr)
device_create_file(&tun->dev->dev, &dev_attr_owner) ||
device_create_file(&tun->dev->dev, &dev_attr_group))
pr_err("Failed to create tun sysfs files\n");
-
- netif_carrier_on(tun->dev);
}
+ netif_carrier_on(tun->dev);
+
tun_debug(KERN_INFO, tun, "tun_set_iff\n");
if (ifr->ifr_flags & IFF_NO_PI)
^ permalink raw reply related [flat|nested] 7+ messages in thread
* Re: [PATCHv2] tun: fix carrier on/off status
2013-01-28 10:38 ` [PATCHv2] " Michael S. Tsirkin
@ 2013-01-28 11:00 ` Jason Wang
2013-01-28 19:38 ` Toralf Förster
2013-01-29 20:45 ` David Miller
2 siblings, 0 replies; 7+ messages in thread
From: Jason Wang @ 2013-01-28 11:00 UTC (permalink / raw)
To: Michael S. Tsirkin
Cc: Toralf Förster, netdev, Linux Kernel, David Miller
On 01/28/2013 06:38 PM, Michael S. Tsirkin wrote:
> Commit c8d68e6be1c3b242f1c598595830890b65cea64a removed carrier off call
> from tun_detach since it's now called on queue disable and not only on
> tun close. This confuses userspace which used this flag to detect a
> free tun. To fix, put this back but under if (clean).
>
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
>
> ---
>
> Changes from v1:
> Don't set carrier off unless all queues are closed.
>
> Note: didn't test in MQ mode - Jason, care checking this does the
> right thing there?
Tested-by: Jason Wang <jasowang@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>
>
> diff --git a/drivers/net/tun.c b/drivers/net/tun.c
> index af372d0..06b2723 100644
> --- a/drivers/net/tun.c
> +++ b/drivers/net/tun.c
> @@ -434,10 +434,13 @@ static void __tun_detach(struct tun_file *tfile, bool clean)
> }
>
> if (clean) {
> - if (tun && tun->numqueues == 0 && tun->numdisabled == 0 &&
> - !(tun->flags & TUN_PERSIST))
> - if (tun->dev->reg_state == NETREG_REGISTERED)
> + if (tun && tun->numqueues == 0 && tun->numdisabled == 0) {
> + netif_carrier_off(tun->dev);
> +
> + if (!(tun->flags & TUN_PERSIST) &&
> + tun->dev->reg_state == NETREG_REGISTERED)
> unregister_netdevice(tun->dev);
> + }
>
> BUG_ON(!test_bit(SOCK_EXTERNALLY_ALLOCATED,
> &tfile->socket.flags));
> @@ -1644,10 +1647,10 @@ static int tun_set_iff(struct net *net, struct file *file, struct ifreq *ifr)
> device_create_file(&tun->dev->dev, &dev_attr_owner) ||
> device_create_file(&tun->dev->dev, &dev_attr_group))
> pr_err("Failed to create tun sysfs files\n");
> -
> - netif_carrier_on(tun->dev);
> }
>
> + netif_carrier_on(tun->dev);
> +
> tun_debug(KERN_INFO, tun, "tun_set_iff\n");
>
> if (ifr->ifr_flags & IFF_NO_PI)
> --
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
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> More majordomo info at http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at http://www.tux.org/lkml/
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCHv2] tun: fix carrier on/off status
2013-01-28 10:38 ` [PATCHv2] " Michael S. Tsirkin
2013-01-28 11:00 ` Jason Wang
@ 2013-01-28 19:38 ` Toralf Förster
2013-01-29 20:45 ` David Miller
2 siblings, 0 replies; 7+ messages in thread
From: Toralf Förster @ 2013-01-28 19:38 UTC (permalink / raw)
To: Michael S. Tsirkin; +Cc: Jason Wang, netdev, Linux Kernel, David Miller
Tested-by: Toralf Förster <toralf.foerster@gmx.de>
On 01/28/2013 11:38 AM, Michael S. Tsirkin wrote:
> Commit c8d68e6be1c3b242f1c598595830890b65cea64a removed carrier off call
> from tun_detach since it's now called on queue disable and not only on
> tun close. This confuses userspace which used this flag to detect a
> free tun. To fix, put this back but under if (clean).
>
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
>
> ---
>
> Changes from v1:
> Don't set carrier off unless all queues are closed.
>
> Note: didn't test in MQ mode - Jason, care checking this does the
> right thing there?
>
> diff --git a/drivers/net/tun.c b/drivers/net/tun.c
> index af372d0..06b2723 100644
> --- a/drivers/net/tun.c
> +++ b/drivers/net/tun.c
> @@ -434,10 +434,13 @@ static void __tun_detach(struct tun_file *tfile, bool clean)
> }
>
> if (clean) {
> - if (tun && tun->numqueues == 0 && tun->numdisabled == 0 &&
> - !(tun->flags & TUN_PERSIST))
> - if (tun->dev->reg_state == NETREG_REGISTERED)
> + if (tun && tun->numqueues == 0 && tun->numdisabled == 0) {
> + netif_carrier_off(tun->dev);
> +
> + if (!(tun->flags & TUN_PERSIST) &&
> + tun->dev->reg_state == NETREG_REGISTERED)
> unregister_netdevice(tun->dev);
> + }
>
> BUG_ON(!test_bit(SOCK_EXTERNALLY_ALLOCATED,
> &tfile->socket.flags));
> @@ -1644,10 +1647,10 @@ static int tun_set_iff(struct net *net, struct file *file, struct ifreq *ifr)
> device_create_file(&tun->dev->dev, &dev_attr_owner) ||
> device_create_file(&tun->dev->dev, &dev_attr_group))
> pr_err("Failed to create tun sysfs files\n");
> -
> - netif_carrier_on(tun->dev);
> }
>
> + netif_carrier_on(tun->dev);
> +
> tun_debug(KERN_INFO, tun, "tun_set_iff\n");
>
> if (ifr->ifr_flags & IFF_NO_PI)
>
--
MfG/Sincerely
Toralf Förster
pgp finger print: 7B1A 07F4 EC82 0F90 D4C2 8936 872A E508 7DB6 9DA3
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCHv2] tun: fix carrier on/off status
2013-01-28 10:38 ` [PATCHv2] " Michael S. Tsirkin
2013-01-28 11:00 ` Jason Wang
2013-01-28 19:38 ` Toralf Förster
@ 2013-01-29 20:45 ` David Miller
2 siblings, 0 replies; 7+ messages in thread
From: David Miller @ 2013-01-29 20:45 UTC (permalink / raw)
To: mst; +Cc: jasowang, toralf.foerster, netdev, linux-kernel
From: "Michael S. Tsirkin" <mst@redhat.com>
Date: Mon, 28 Jan 2013 12:38:02 +0200
> Commit c8d68e6be1c3b242f1c598595830890b65cea64a removed carrier off call
> from tun_detach since it's now called on queue disable and not only on
> tun close. This confuses userspace which used this flag to detect a
> free tun. To fix, put this back but under if (clean).
>
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Applied.
^ permalink raw reply [flat|nested] 7+ messages in thread
end of thread, other threads:[~2013-01-29 20:45 UTC | newest]
Thread overview: 7+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2013-01-26 10:29 How to find an unused TAP device with kernel 3.8 ? Toralf Förster
2013-01-28 9:38 ` Jason Wang
2013-01-28 10:11 ` [PATCH] tun: fix carrier on/off status Michael S. Tsirkin
2013-01-28 10:38 ` [PATCHv2] " Michael S. Tsirkin
2013-01-28 11:00 ` Jason Wang
2013-01-28 19:38 ` Toralf Förster
2013-01-29 20:45 ` David Miller
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