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: Allow to register tun devices in namespace.

PATCH In review Pavel Emelyanov 2 participants 3 messages Apr 2, 2008 – Apr 3, 2008

Subsystems (3)
Networking Network drivers TUN/TAP driver
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Pavel Emelyanov

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#0 lore raw

PATCH 3/3 : Allow to register tun devices in namespace.

This is basically means that a net is set for a new device, but actually this involves two more steps:

1. mark the tun device as "local", i.e. do not allow for it to move across namespaces.

This is done so, since tun device is most often associated to some file (and thus to some process) and moving the device alone is not valid while keeping the file and the process outside.

2. get the tun device's net when tun becomes attached and put one when it becomes detached.

This is needed to handle the case when a task owning the tun dies, but a files lives for some more time - in this case we must not allow for net to be freed, since its exit hook will spoil that file's private data by unregistering the tun from under tun_chr_close.

Signed-off-by Pavel Emelyanov <[email protected]>
---
 drivers/net/tun.c |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)
drivers/net/tun.c +4 -0
index e3210bf..bcc4ced 100644
@@ -438,6 +438,7 @@ static void tun_setup(struct net_device *dev)
 	dev->stop = tun_net_close;
 	dev->ethtool_ops = &tun_ethtool_ops;
 	dev->destructor = free_netdev;
+	dev->features |= NETIF_F_NETNS_LOCAL;
 }
 
 static struct tun_struct *tun_get_by_name(struct net *net, const char *name)

@@ -503,6 +504,7 @@ static int tun_set_iff(struct net *net, struct file *file, struct ifreq *ifr)
 		if (!dev)
 			return -ENOMEM;
 
+		dev_net_set(dev, net);
 		tun = netdev_priv(dev);
 		tun->dev = dev;
 		tun->flags = flags;

@@ -542,6 +544,7 @@ static int tun_set_iff(struct net *net, struct file *file, struct ifreq *ifr)
 
 	file->private_data = tun;
 	tun->attached = 1;
+	get_net(dev_net(tun->dev));
 
 	strcpy(ifr->ifr_name, tun->dev->name);
 	return 0;

@@ -757,6 +760,7 @@ static int tun_chr_close(struct inode *inode, struct file *file)
 	/* Detach from net device */
 	file->private_data = NULL;
 	tun->attached = 0;
+	put_net(dev_net(tun->dev));
 
 	/* Drop read queue */
 	skb_queue_purge(&tun->readq);
Signature · 1 line
1.5.3.4
#1 lore raw

Hi Pavel,

All three patches look perfectly fine to me.
Feel free to add Acked-by: Max Krasnyansky <[email protected]>

Quoted 10 lines · Pavel Emelyanov

This is basically means that a net is set for a new device, but actually this involves two more steps:

1. mark the tun device as "local", i.e. do not allow for it to move across namespaces.

This is done so, since tun device is most often associated to some file (and thus to some process) and moving the device alone is not valid while keeping the file and the process outside.

Quoted 7 lines

2. get the tun device's net when tun becomes attached and put one when it becomes detached.

This is needed to handle the case when a task owning the tun dies, but a files lives for some more time - in this case we must not allow for net to be freed, since its exit hook will spoil that file's private data by unregistering the tun from under tun_chr_close.

I'm not sure what you mean "by file lives on" here. I believe you're talking about persistent tun devices. ie Those that exist in detached state and are not attached to any file descriptors. "net" refcounting logic there looks fine to me.

Max

author
#2 lore raw
Quoted 4 lines · Max Krasnyanskiy

Hi Pavel,

All three patches look perfectly fine to me.
Feel free to add Acked-by: Max Krasnyansky <[email protected]>

:)

Quoted 11 lines
Quoted 10 lines · Pavel Emelyanov

This is basically means that a net is set for a new device, but actually this involves two more steps:

1. mark the tun device as "local", i.e. do not allow for it to move across namespaces.

This is done so, since tun device is most often associated to some file (and thus to some process) and moving the device alone is not valid while keeping the file and the process outside.

Quoted 8 lines
Quoted 7 lines

2. get the tun device's net when tun becomes attached and put one when it becomes detached.

This is needed to handle the case when a task owning the tun dies, but a files lives for some more time - in this case we must not allow for net to be freed, since its exit hook will spoil that file's private data by unregistering the tun from under tun_chr_close.

I'm not sure what you mean "by file lives on" here. I believe you're talking

I meant the following. When a task dies it releases it's net namespace and thus this net cleanup job may start. But the file, that holds the (not yet detached) tun device is not released immediately - so before this file is being released the tun_exit_net callback may be called and the file's tun device will be unregistered in it. I catch this race by getting the net by attached tun device, so that net is cleaned up only when there are only detached tuns in it. In this case no tasks will pick up these tuns and everything will be OK.

Quoted 3 lines

about persistent tun devices. ie Those that exist in detached state and are not attached to any file descriptors.
"net" refcounting logic there looks fine to me.

Great!

Quoted 1 line

Max

Thanks,
Pavel