[PATCH] wwan: core: Fix missing RTM_NEWLINK event

[PATCH] wwan: core: Fix missing RTM_NEWLINK event

[Loic Poulain]

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).

Cc: stable@vger.kernel.org
Fixes: 88b710532e53 ("wwan: add interface creation support")
Signed-off-by: Loic Poulain <loic.poulain@linaro.org>
---
 drivers/net/wwan/wwan_core.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/net/wwan/wwan_core.c b/drivers/net/wwan/wwan_core.c
index 3e16c31..409caf4 100644
--- a/drivers/net/wwan/wwan_core.c
+++ b/drivers/net/wwan/wwan_core.c
@@ -866,6 +866,10 @@ static int wwan_rtnl_newlink(struct net *src_net, struct net_device *dev,
 	else
 		ret = register_netdevice(dev);
 
+	/* Link initialized, notify new link */
+	if (!ret)
+		rtnl_configure_link(dev, NULL);
+
 out:
 	/* release the reference */
 	put_device(&wwandev->dev);
-- 
2.7.4

Re: [PATCH] wwan: core: Fix missing RTM_NEWLINK event

[Sergey Ryazanov]

Hello Loic,

On Thu, Jul 22, 2021 at 6:39 PM Loic Poulain <loic.poulain@linaro.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?

-- 
Sergey

Re: [PATCH] wwan: core: Fix missing RTM_NEWLINK event

[Loic Poulain]

On Thu, 22 Jul 2021 at 18:14, Sergey Ryazanov <ryazanov.s.a@gmail.com> wrote:
>
> Hello Loic,
>
> On Thu, Jul 22, 2021 at 6:39 PM Loic Poulain <loic.poulain@linaro.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.

Regards,
Loic


>
> --
> Sergey

Re: [PATCH] wwan: core: Fix missing RTM_NEWLINK event

[Sergey Ryazanov]

On Thu, Jul 22, 2021 at 7:44 PM Loic Poulain <loic.poulain@linaro.org> wrote:
> On Thu, 22 Jul 2021 at 18:14, Sergey Ryazanov <ryazanov.s.a@gmail.com> wrote:
>> On Thu, Jul 22, 2021 at 6:39 PM Loic Poulain <loic.poulain@linaro.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
:(

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 */
+
 unlock:
  rtnl_unlock();

--
Sergey

Re: [PATCH] wwan: core: Fix missing RTM_NEWLINK event

[Loic Poulain]

On Thu, 22 Jul 2021 at 19:42, Sergey Ryazanov <ryazanov.s.a@gmail.com> wrote:
>
> On Thu, Jul 22, 2021 at 7:44 PM Loic Poulain <loic.poulain@linaro.org> wrote:
> > On Thu, 22 Jul 2021 at 18:14, Sergey Ryazanov <ryazanov.s.a@gmail.com> wrote:
> >> On Thu, Jul 22, 2021 at 6:39 PM Loic Poulain <loic.poulain@linaro.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