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

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Message-ID: <CABAhCORgi7Jqu=Aigs6Fc8ewG5OshFvcunye03R43C+Z0ojZyw@mail.gmail.com>
Date: Thu, 13 Feb 2025 17:55:32 +0800
From: Xiao Liang <shaw.leon@...il.com>
To: Kuniyuki Iwashima <kuniyu@...zon.com>
Cc: alex.aring@...il.com, andrew+netdev@...n.ch, 
	b.a.t.m.a.n@...ts.open-mesh.org, bpf@...r.kernel.org, bridge@...ts.linux.dev, 
	davem@...emloft.net, donald.hunter@...il.com, dsahern@...nel.org, 
	edumazet@...gle.com, herbert@...dor.apana.org.au, horms@...nel.org, 
	kuba@...nel.org, linux-can@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-kselftest@...r.kernel.org, linux-ppp@...r.kernel.org, 
	linux-rdma@...r.kernel.org, linux-wireless@...r.kernel.org, 
	linux-wpan@...r.kernel.org, miquel.raynal@...tlin.com, netdev@...r.kernel.org, 
	osmocom-net-gprs@...ts.osmocom.org, pabeni@...hat.com, shuah@...nel.org, 
	stefan@...enfreihafen.org, steffen.klassert@...unet.com, 
	wireguard@...ts.zx2c4.com
Subject: Re: [PATCH net-next v9 06/11] net: ipv6: Use link netns in newlink()
 of rtnl_link_ops

On Thu, Feb 13, 2025 at 4:37 PM Xiao Liang <shaw.leon@...il.com> wrote:
>
> On Thu, Feb 13, 2025 at 3:05 PM Kuniyuki Iwashima <kuniyu@...zon.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.