netdev - Re: [PATCH] wwan: core: Fix missing RTM

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Date:   Thu, 22 Jul 2021 20:01:08 +0200
From:   Loic Poulain <loic.poulain@...aro.org>
To:     Sergey Ryazanov <ryazanov.s.a@...il.com>
Cc:     David Miller <davem@...emloft.net>,
        Johannes Berg <johannes@...solutions.net>,
        Network Development <netdev@...r.kernel.org>,
        stable@...r.kernel.org
Subject: Re: [PATCH] wwan: core: Fix missing RTM_NEWLINK event

On Thu, 22 Jul 2021 at 19:42, Sergey Ryazanov <ryazanov.s.a@...il.com> wrote:
>
> On Thu, Jul 22, 2021 at 7:44 PM Loic Poulain <loic.poulain@...aro.org> wrote:
> > On Thu, 22 Jul 2021 at 18:14, Sergey Ryazanov <ryazanov.s.a@...il.com> wrote:
> >> On Thu, Jul 22, 2021 at 6:39 PM Loic Poulain <loic.poulain@...aro.org> wrote:
> >>> By default there is no rtnetlink event generated when registering a
> >>> netdev with rtnl_link_ops until its rtnl_link_state is switched to
> >>> initialized (RTNL_LINK_INITIALIZED). This causes issues with user
> >>> tools like NetworkManager which relies on such event to manage links.
> >>>
> >>> Fix that by setting link to initialized (via rtnl_configure_link).
> >>
> >> Shouldn't the __rtnl_newlink() function call rtnl_configure_link()
> >> just after the newlink() callback invocation? Or I missed something?
> >
> > Ah right, but the first call of rtnl_configure_link() (uninitialized)
> > does not cause RTM_NEWLINK event (cf __dev_notify_flags). It however
> > seems to work for other link types (e,g, rmnet), so probably something
> > to clarify here.
>
> Just check additional netdev creation with hwsim:
>
> # ip link add wwan0.3 parentdev wwan0 type wwan linkid 3
>
> On the other console:
>
> # ip -d mon
> 6: wwan0.3: <POINTOPOINT,NOARP> mtu 1500 qdisc noop state DOWN group default
>     link/none  promiscuity 0 minmtu 68 maxmtu 65535
>     wwan numtxqueues 1 numrxqueues 1 gso_max_size 65536 gso_max_segs 65535
>
> But I saw no notification at the moment of wwan_hwsim module loading.
> This happens since I missed the rtnl_configure_link() call in the
> wwan_create_default_link() after the default link successful creation
> :(

Yep just realized that!

> So we need your fix at least in the default link creation routine to
> fix ca374290aaad ("wwan: core: support default netdev creation").
> Something like this:
>
> diff --git a/drivers/net/wwan/wwan_core.c b/drivers/net/wwan/wwan_core.c
> index 3e16c318e705..374aa2cc884c 100644
> --- a/drivers/net/wwan/wwan_core.c
> +++ b/drivers/net/wwan/wwan_core.c
> @@ -984,6 +984,8 @@ static void wwan_create_default_link(struct
> wwan_device *wwandev,
>   goto unlock;
>   }
>
> + rtnl_configure_link(dev, NULL); /* trigger the RTM_NEWLINK event */
> +

Testing right now.

Loic