netdev - Re: [PATCH v3] hv_netvsc: Set VF priv_flags to IFF_NO_ADDRCONF before open to prevent IPv6 addrconf

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Message-ID: <CADvbK_cdOTO_UVg6ovx-Si7-ja=ErYw-MnSnR-CL4HwmtKJ8YQ@mail.gmail.com>
Date: Wed, 16 Jul 2025 11:14:27 -0400
From: Xin Long <lucien.xin@...il.com>
To: Simon Horman <horms@...nel.org>
Cc: Li Tian <litian@...hat.com>, netdev@...r.kernel.org, linux-hyperv@...r.kernel.org, 
	linux-kernel@...r.kernel.org, Haiyang Zhang <haiyangz@...rosoft.com>, 
	Dexuan Cui <decui@...rosoft.com>, Stephen Hemminger <stephen@...workplumber.org>, 
	Long Li <longli@...rosoft.com>
Subject: Re: [PATCH v3] hv_netvsc: Set VF priv_flags to IFF_NO_ADDRCONF before
 open to prevent IPv6 addrconf

On Wed, Jul 16, 2025 at 5:29 AM Simon Horman <horms@...nel.org> wrote:
>
> + Xin Long
>
Thanks for Ccing me.

> On Wed, Jul 16, 2025 at 08:26:05AM +0800, Li Tian wrote:
> > Set an additional flag IFF_NO_ADDRCONF to prevent ipv6 addrconf.
> >
> > Commit under Fixes added a new flag change that was not made
> > to hv_netvsc resulting in the VF being assinged an IPv6.
> >
> > Fixes: 8a321cf7becc ("net: add IFF_NO_ADDRCONF and use it in bonding to prevent ipv6 addrconf")
> > Suggested-by: Cathy Avery <cavery@...hat.com>
> > Signed-off-by: Li Tian <litian@...hat.com>
> > ---
> > v3:
> >   - only fixes commit message.
> > v2: https://lore.kernel.org/netdev/20250710024603.10162-1-litian@redhat.com/
> >   - instead of replacing flag, add it.
> > v1: https://lore.kernel.org/netdev/20250710024603.10162-1-litian@redhat.com/
> > ---
> >  drivers/net/hyperv/netvsc_drv.c | 5 ++++-
> >  1 file changed, 4 insertions(+), 1 deletion(-)
>
> Hi Li Tian,
>
> Thanks for addressing earlier feedback.
>
> I don't think you need to repost because of this, but for future reference:
>
> 1. Because this is a fix for a commit that is present in net
>    it should be targeted at that tree.
>
>    Subject: [PATCH net vX] ...
>
> 2. Please use get_maintainers.pl this.patch to generate the CC list. In
>    this case Xin Long (now CCed) should be included as he is the author of the
>    patch cited in the Fixes tag.
>
>    b4 can help you with this and other aspects of patch management.
>
> >
> > diff --git a/drivers/net/hyperv/netvsc_drv.c b/drivers/net/hyperv/netvsc_drv.c
> > index c41a025c66f0..8be9bce66a4e 100644
> > --- a/drivers/net/hyperv/netvsc_drv.c
> > +++ b/drivers/net/hyperv/netvsc_drv.c
> > @@ -2317,8 +2317,11 @@ static int netvsc_prepare_bonding(struct net_device *vf_netdev)
> >       if (!ndev)
> >               return NOTIFY_DONE;
> >
> > -     /* set slave flag before open to prevent IPv6 addrconf */
> > +     /* Set slave flag and no addrconf flag before open
> > +      * to prevent IPv6 addrconf.
> > +      */
> >       vf_netdev->flags |= IFF_SLAVE;
> > +     vf_netdev->priv_flags |= IFF_NO_ADDRCONF;
If it is only to prevent IPv6 addrconf, I think you can replace IFF_SLAVE
with IFF_NO_ADDRCONF.

IFF_SLAVE normally comes with IFF_MASTER, like bonding and eql.
I don't see IFF_MASTER used in netvsc_drv.c, so IFF_SLAVE probably
should be dropped, including the one in __netvsc_vf_setup()?

> >       return NOTIFY_DONE;
> >  }
> >
> > --
> > 2.50.0
> >
> >