[Devel] Re: [PATCH] netns: Coexist with the sysfs limitations

[Daniel Lezcano]

Eric W. Biederman wrote:
> To make testing of the network namespace simpler allow
> the network namespace code and the sysfs code to be
> compiled and run at the same time.  To do this only
> virtual devices are allowed in the additional network
> namespaces and those virtual devices are not placed
> in the kobject tree.
> 
> Since virtual devices don't actually do anything interesting
> hardware wise that needs device management there should
> be no loss in keeping them out of the kobject tree and
> by implication sysfs.  The gain in ease of testing
> and code coverage should be significant.
> 
> I.e. people running distributions that make it next to
> impossible to boot without sysfs should at be able to
> boot a test kernel now.
> 
> Plus no ABIs are harmed with this patch.
> 
> Signed-off-by: Eric W. Biederman <ebiederm at xmission.com>

Acked-by: Daniel Lezcano <dlezcano at fr.ibm.com>

> ---
>  net/Kconfig          |    2 +-
>  net/core/dev.c       |   12 +++++++++++-
>  net/core/net-sysfs.c |    7 +++++++
>  3 files changed, 19 insertions(+), 2 deletions(-)
> 
> diff --git a/net/Kconfig b/net/Kconfig
> index d789d79..8c3d97c 100644
> --- a/net/Kconfig
> +++ b/net/Kconfig
> @@ -27,7 +27,7 @@ menu "Networking options"
>  config NET_NS
>  	bool "Network namespace support"
>  	default n
> -	depends on EXPERIMENTAL && !SYSFS && NAMESPACES
> +	depends on EXPERIMENTAL && NAMESPACES
>  	help
>  	  Allow user space to create what appear to be multiple instances
>  	  of the network stack.
> diff --git a/net/core/dev.c b/net/core/dev.c
> index b8a4fd0..a7f0461 100644
> --- a/net/core/dev.c
> +++ b/net/core/dev.c
> @@ -4449,6 +4449,15 @@ int dev_change_net_namespace(struct net_device *dev, struct net *net, const char
>  	if (dev->features & NETIF_F_NETNS_LOCAL)
>  		goto out;
> 
> +#ifdef CONFIG_SYSFS
> +	/* Don't allow real devices to be moved when sysfs
> +	 * is enabled.
> +	 */
> +	err = -EINVAL;
> +	if (dev->dev.parent)
> +		goto out;
> +#endif
> +
>  	/* Ensure the device has been registrered */
>  	err = -EINVAL;
>  	if (dev->reg_state != NETREG_REGISTERED)
> @@ -4506,6 +4515,8 @@ int dev_change_net_namespace(struct net_device *dev, struct net *net, const char
>  	 */
>  	dev_addr_discard(dev);
> 
> +	netdev_unregister_kobject(dev);
> +
>  	/* Actually switch the network namespace */
>  	dev_net_set(dev, net);
> 
> @@ -4522,7 +4533,6 @@ int dev_change_net_namespace(struct net_device *dev, struct net *net, const char
>  	}
> 
>  	/* Fixup kobjects */
> -	netdev_unregister_kobject(dev);
>  	err = netdev_register_kobject(dev);
>  	WARN_ON(err);
> 
> diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
> index 92d6b94..85cb8bd 100644
> --- a/net/core/net-sysfs.c
> +++ b/net/core/net-sysfs.c
> @@ -476,6 +476,10 @@ void netdev_unregister_kobject(struct net_device * net)
>  	struct device *dev = &(net->dev);
> 
>  	kobject_get(&dev->kobj);
> +
> +	if (dev_net(net) != &init_net)
> +		return;
> +
>  	device_del(dev);
>  }
> 
> @@ -501,6 +505,9 @@ int netdev_register_kobject(struct net_device *net)
>  #endif
>  #endif /* CONFIG_SYSFS */
> 
> +	if (dev_net(net) != &init_net)
> +		return 0;
> +
>  	return device_add(dev);
>  }
> 


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