Subject: Re: [PATCH] hv_netvsc: Fix net device attach on older Windows hosts

From: Stephen Hemminger <[email-masked]>
Date: Tue, 8 May 2018 15:49:33 -0700

On Tue, 08 May 2018 20:17:51 +0200
Mohammed Gamal <[email-masked]> wrote:

> On Tue, 2018-05-08 at 11:13 -0700, Stephen Hemminger wrote:
> > On Tue,  8 May 2018 19:40:47 +0200
> > Mohammed Gamal <[email-masked]> wrote:
> >   
> > > On older windows hosts the net_device instance is returned to
> > > the caller of rndis_filter_device_add() without having the presence
> > > bit set first. This would cause any subsequent calls to network
> > > device
> > > operations (e.g. MTU change, channel change) to fail after the
> > > device
> > > is detached once, returning -ENODEV.
> > > 
> > > Make sure we explicitly call netif_device_attach() before returning
> > > the net_device instance to make sure the presence bit is set
> > > 
> > > Fixes: 7b2ee50c0cd5 ("hv_netvsc: common detach logic")
> > > 
> > > Signed-off-by: Mohammed Gamal <[email-masked]>
> > > ---
> > >  drivers/net/hyperv/rndis_filter.c | 4 +++-
> > >  1 file changed, 3 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/drivers/net/hyperv/rndis_filter.c
> > > b/drivers/net/hyperv/rndis_filter.c
> > > index 6b127be..09a3c1d 100644
> > > --- a/drivers/net/hyperv/rndis_filter.c
> > > +++ b/drivers/net/hyperv/rndis_filter.c
> > > @@ -1287,8 +1287,10 @@ struct netvsc_device
> > > *rndis_filter_device_add(struct hv_device *dev,
> > >  		   rndis_device->hw_mac_adr,
> > >  		   rndis_device->link_state ? "down" : "up");
> > >  
> > > -	if (net_device->nvsp_version < NVSP_PROTOCOL_VERSION_5)
> > > +	if (net_device->nvsp_version < NVSP_PROTOCOL_VERSION_5) {
> > > +		netif_device_attach(net);
> > >  		return net_device;
> > > +	}  
> > 
> > Yes, this looks right, but it might be easier to use goto existing
> > exit
> > path.
> >   
> 
> I was just not sure if we should set max_chn and num_chn here. I will
> modify the patch and resend.

On older code it was just a goto. At that point: num_chn = max_chn = 1
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