How to avoid getting ndo_open() immediately after probe

How to avoid getting ndo_open() immediately after probe

[Arijit De]

Hi,

I have handled the probe() and registered the netdev structure using register_netdev().
I have observed in other opensource driver(i.e. Intel e1000e driver) that ndo_open() gets called only when we try to bring up the interface (i.e. ifconfig <ip> ifconfig eth0 <ip-addr> netmask <net-mask> up).
But in my network driver I am getting ndo_open() call immediately after I handle the probe(). It's a wrong behavior, also my network interface is getting to UP/RUNNING state(as shown below) even without any valid ip address.

enp1s0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        ether 00:22:55:33:22:28  txqueuelen 1000  (Ethernet)
        RX packets 0  bytes 0 (0.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 252  bytes 43066 (43.0 KB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions

What is the change required in the driver such that my network interface(enp1s0) should be in down state(BROADCAST & MULTICAST only) after probe()
and ndo_open() call should happen only when device gets configured?

Thanks
Arijit

Re: How to avoid getting ndo_open() immediately after probe

[Stephen Hemminger]

On Thu, 2 Dec 2021 18:11:30 +0000
Arijit De <arijitde@marvell.com> wrote:

> Hi,
> 
> I have handled the probe() and registered the netdev structure using register_netdev().
> I have observed in other opensource driver(i.e. Intel e1000e driver) that ndo_open() gets called only when we try to bring up the interface (i.e. ifconfig <ip> ifconfig eth0 <ip-addr> netmask <net-mask> up).
> But in my network driver I am getting ndo_open() call immediately after I handle the probe(). It's a wrong behavior, also my network interface is getting to UP/RUNNING state(as shown below) even without any valid ip address.
> 
> enp1s0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
>         ether 00:22:55:33:22:28  txqueuelen 1000  (Ethernet)
>         RX packets 0  bytes 0 (0.0 B)
>         RX errors 0  dropped 0  overruns 0  frame 0
>         TX packets 252  bytes 43066 (43.0 KB)
>         TX errors 0  dropped 0 overruns 0  carrier 0  collisions
> 
> What is the change required in the driver such that my network interface(enp1s0) should be in down state(BROADCAST & MULTICAST only) after probe()
> and ndo_open() call should happen only when device gets configured?
> 
> Thanks
> Arijit

ndo_open gets called when userspace brings the device up.
Based on the device name, you are running on a distribution which renames
devices; probably systemd/networkd and it is starting the device.

You need to change userspace configuration 

Re: How to avoid getting ndo_open() immediately after probe

[Lino Sanfilippo]

Hi,

On 02.12.21 at 19:11, Arijit De wrote:
> Hi,
>
> I have handled the probe() and registered the netdev structure using register_netdev().
> I have observed in other opensource driver(i.e. Intel e1000e driver) that ndo_open() gets called only when we try to bring up the interface (i.e. ifconfig <ip> ifconfig eth0 <ip-addr> netmask <net-mask> up).
> But in my network driver I am getting ndo_open() call immediately after I handle the probe(). It's a wrong behavior, also my network interface is getting to UP/RUNNING state(as shown below) even without any valid ip address.

There is nothing wrong here. As soon as you register the netdevice with the kernel it is available
for userspace and userspace is free to bring it up. This may happen immediately after registration,
so your driver has to be prepared for this.
Its absolutely fine to bring up a network device without any ip address assigned.

Regards,
Lino


>
> enp1s0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
>         ether 00:22:55:33:22:28  txqueuelen 1000  (Ethernet)
>         RX packets 0  bytes 0 (0.0 B)
>         RX errors 0  dropped 0  overruns 0  frame 0
>         TX packets 252  bytes 43066 (43.0 KB)
>         TX errors 0  dropped 0 overruns 0  carrier 0  collisions
>
> What is the change required in the driver such that my network interface(enp1s0) should be in down state(BROADCAST & MULTICAST only) after probe()
> and ndo_open() call should happen only when device gets configured?
>
> Thanks
> Arijit
>

Re: How to avoid getting ndo_open() immediately after probe

[Andrew Lunn]

On Thu, Dec 02, 2021 at 09:29:21PM +0100, Lino Sanfilippo wrote:
> 
> Hi,
> 
> On 02.12.21 at 19:11, Arijit De wrote:
> > Hi,
> >
> > I have handled the probe() and registered the netdev structure using register_netdev().
> > I have observed in other opensource driver(i.e. Intel e1000e driver) that ndo_open() gets called only when we try to bring up the interface (i.e. ifconfig <ip> ifconfig eth0 <ip-addr> netmask <net-mask> up).
> > But in my network driver I am getting ndo_open() call immediately after I handle the probe(). It's a wrong behavior, also my network interface is getting to UP/RUNNING state(as shown below) even without any valid ip address.
> 
> There is nothing wrong here. As soon as you register the netdevice with the kernel it is available
> for userspace and userspace is free to bring it up. This may happen immediately after registration,
> so your driver has to be prepared for this.
> Its absolutely fine to bring up a network device without any ip address assigned.

And if you are using NFS root, the kernel can actually call ndo_open()
before register_netdev() even completes.

This is a common bug i look for in new drivers, register_netdev()
pretty much has to be the last thing done inside the probe function.

       Andrew