Re: [PATCHv3 net 2/2] team: reset team's flags when down link is P2P device

[Hangbin Liu <liuhangbin@gmail.com>]

On Thu, Jul 20, 2023 at 10:29:19AM +0200, Paolo Abeni wrote:
> > +static void team_ether_setup(struct net_device *dev)
> > +{
> > +	unsigned int flags = dev->flags & IFF_UP;
> > +
> > +	ether_setup(dev);
> > +	dev->flags |= flags;
> > +	dev->priv_flags &= ~IFF_TX_SKB_SHARING;
> 
> I think we can't do the above. e.g. ether_setup() sets dev->mtu to
> ethernet default, while prior to this patch dev inherited mtu from the
> slaved device. The change may affect the user-space in bad ways.

Hi Paolo,

I don't see the reason why we should inherited a none ethernet dev's mtu
to an ethernet dev (i.e. add a none ethernet dev to team, then delete it and
re-add a ethernet dev to team). I think the dev type has changed, so the
mtu should also be updated.

BTW, after adding the port, team will also set port's mtu to team's mtu.

> 
> I think we just need an 'else' branch in the point2point check above,
> restoring the bcast/mcast flags as needed.

Reset the flags is not enough. All the dev header_ops, type, etc are
all need to be reset back, that's why we need to call ether_setup().

Thanks
Hangbin