netdev - Re: [PATCH net-next] net: vxlan: when lower dev unregisters remove vxlan dev as well

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Date:	Fri, 10 Jan 2014 10:51:28 -0800
From:	Cong Wang <cwang@...pensource.com>
To:	Daniel Borkmann <dborkman@...hat.com>
Cc:	David Miller <davem@...emloft.net>, netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next] net: vxlan: when lower dev unregisters remove
 vxlan dev as well

On Fri, Jan 10, 2014 at 5:01 AM, Daniel Borkmann <dborkman@...hat.com> wrote:
> We can create a vxlan device with an explicit underlying carrier.
> In that case, when the carrier link is being deleted from the
> system (e.g. due to module unload) we should also clean up all
> created vxlan devices on top of it since otherwise we're in an
> inconsistent state in vxlan device. In that case, the user needs
> to remove all such devices, while in case of other virtual devs
> that sit on top of physical ones, it is usually the case that
> these devices do unregister automatically as well and do not
> leave the burden on the user.
>
> This work is not necessary when vxlan device was not created with
> a real underlying device, as connections can resume in that case
> when driver is plugged again. But at least for the other cases,
> we should go ahead and do the cleanup on removal.
>

So it makes sense to move the notifier register to vxlan_newlink()
from vxlan_init_module()?

...
>
> diff --git a/drivers/net/vxlan.c b/drivers/net/vxlan.c
> index 481f85d..39035ba 100644
> --- a/drivers/net/vxlan.c
> +++ b/drivers/net/vxlan.c
> @@ -2656,6 +2656,54 @@ static struct rtnl_link_ops vxlan_link_ops __read_mostly = {
>         .fill_info      = vxlan_fill_info,
>  };
>
> +static void vxlan_handle_lowerdev_unregister(struct vxlan_net *vn,
> +                                            struct net_device *dev)
> +{
> +       struct vxlan_dev *vxlan, *next;
> +       LIST_HEAD(list_kill);
> +
> +       BUG_ON(!rtnl_is_locked());


This is not necessary at all, it is known that netdev notication
holds rtnl lock.

> +
> +       list_for_each_entry_safe(vxlan, next, &vn->vxlan_list, next) {
> +               struct vxlan_rdst *dst = &vxlan->default_dst;
> +
> +               /* In case we created vxlan device with carrier
> +                * and we loose the carrier due to module unload
> +                * we also need to remove vxlan device. In other
> +                * cases, it's not necessary and remote_ifindex
> +                * is 0 here, so no matches.
> +                */
> +               if (dst->remote_ifindex == dev->ifindex)
> +                       vxlan_dellink(vxlan->dev, &list_kill);
> +       }
> +
> +       unregister_netdevice_many(&list_kill);
> +       list_del(&list_kill);


I think you need to flush fdb as well?


>  static __net_init int vxlan_init_net(struct net *net)
>  {
>         struct vxlan_net *vn = net_generic(net, vxlan_net_id);
> @@ -2673,14 +2721,16 @@ static __net_init int vxlan_init_net(struct net *net)
>  static __net_exit void vxlan_exit_net(struct net *net)
>  {
>         struct vxlan_net *vn = net_generic(net, vxlan_net_id);
> -       struct vxlan_dev *vxlan;
> -       LIST_HEAD(list);
> +       struct vxlan_dev *vxlan, *next;
> +       LIST_HEAD(list_kill);
>
>         rtnl_lock();
> -       list_for_each_entry(vxlan, &vn->vxlan_list, next)
> -               unregister_netdevice_queue(vxlan->dev, &list);
> -       unregister_netdevice_many(&list);
> +       list_for_each_entry_safe(vxlan, next, &vn->vxlan_list, next)
> +               vxlan_dellink(vxlan->dev, &list_kill);
> +       unregister_netdevice_many(&list_kill);
>         rtnl_unlock();
> +
> +       list_del(&list_kill);


Why these changes in vxlan_exit_net()?
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