- DaveM

Hi Kirill,

On 03/05/2018 04:22 PM, Kirill Tkhai wrote:

> Thanks for the explanation, and module unloading should be nice. Just to 
> clarify,
> I worry not about rules, but about netdevices.
>       unshare -n ip link add type vcan
> This command creates net ns, adds vcan there and exits. Then net ns is 
> destroyed.
> Since vcan has rtnl_link_ops, it unregistered by default_device_exit_batch().
> Real can devices are moved to init_net in default_device_exit(), as they don't
> have rtnl_link_ops set.

In fact most of the real CAN drivers have rtnl_link_ops:


Just slcan.c which is something like slip.c is missing these feature.

AFAIK real CAN netdevices are created in init_net at system startup, and you
can move them to a netns later.

When we already have rtnl_link_ops in the real CAN drivers - what happens to
them when the namespace is destroyed? Are they still moved to init_net, or do
we need to add some default handler in the current rtnl_link_ops setup?

> So, for_each_netdev_rcu() cycle in can_pernet_exit() should be useless (there 
> are
> no can devices in the list of net's devices). This looks so for me, please say
> what devices are there if my assumption is wrong.

See above?

>>> Since can_pernet_ops is pernet subsys, it's executed after 
>>> default_device_exit()
>>> from default_device_ops pernet device, as devices exit methods are executed 
>>> first
>>> (see net/core/net_namespace.c).
>> Hm - a device exit fires the NETDEV_UNREGISTER notifier which removes the
>> user-generated filters (e.g. in raw_notifier() in net/can/raw.c).
>> Finally the can_dev_rcv_lists structure is free'd in af_can.c.
>> Marc Kleine-Budde recently proposed a patch to create the can_dev_rcv_lists 
>> at
>> netdevice creation time (-> the space is allocated by alloc_netdev() and
>> removed by free_netdev()). This would remove the handling (allocate & free) 
>> of
>> ml_priv by af_can.c. Would this rework fix the described issue?
> Could you please give me a link to the patches? I can't find them in 
> patchwork.

There was a patchset of 14 patches from Marc where some of the refactoring &
renaming already made it into mainline - but the patches to move the
can_dev_rcv_lists data structure into the network device space have not been


This patch & documentation describes Marc's proposed idea best:

Best regards,

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