Re: [PATCH net-next v9 06/11] net: ipv6: Use link netns in newlink() of rtnl_link_ops

[Kuniyuki Iwashima <kuniyu@amazon.com>]

From: Xiao Liang <shaw.leon@gmail.com>
Date: Thu, 13 Feb 2025 17:55:32 +0800
> On Thu, Feb 13, 2025 at 4:37 PM Xiao Liang <shaw.leon@gmail.com> wrote:
> >
> > On Thu, Feb 13, 2025 at 3:05 PM Kuniyuki Iwashima <kuniyu@amazon.com> wrote:
> > >
> > [...]
> > > > diff --git a/net/ipv6/ip6_gre.c b/net/ipv6/ip6_gre.c
> > > > index 863852abe8ea..108600dc716f 100644
> > > > --- a/net/ipv6/ip6_gre.c
> > > > +++ b/net/ipv6/ip6_gre.c
> > > > @@ -1498,7 +1498,8 @@ static int ip6gre_tunnel_init_common(struct net_device *dev)
> > > >       tunnel = netdev_priv(dev);
> > > >
> > > >       tunnel->dev = dev;
> > > > -     tunnel->net = dev_net(dev);
> > > > +     if (!tunnel->net)
> > > > +             tunnel->net = dev_net(dev);
> > >
> > > Same question as patch 5 for here and other parts.
> > > Do we need this check and assignment ?
> > >
> > > ip6gre_newlink_common
> > > -> nt->net = dev_net(dev)
> > > -> register_netdevice
> > >   -> ndo_init / ip6gre_tunnel_init()
> > >     -> ip6gre_tunnel_init_common
> > >       -> tunnel->net = dev_net(dev)
> >
> > Will remove this line.
> 
> However, fb tunnel of ip6_tunnel, ip6_vti and sit can have
> tunnel->net == NULL here. Take ip6_tunnel for example:
> 
> ip6_tnl_init_net()
>     -> ip6_fb_tnl_dev_init()
>     -> register_netdev()
>         -> register_netdevice()
>             -> ip6_tnl_dev_init()
> 
> This code path (including ip6_fb_tnl_dev_init()) doesn't set
> tunnel->net. But for ip6_gre, ip6gre_fb_tunnel_init() does.

Ah, okay.  Then, let's set net in a single place, which would
be better than spreading net assignment and adding null check
in ->ndo_init(), and maybe apply the same to IPv4 tunnels ?