Re: [PATCH net v1] ip_gre: Reject enabling collect metadata through changelink

[Xuanqiang Luo]

在 2026/9/20 18:26, Ido Schimmel 写道:
> On Thu, Sep 17, 2026 at 05:50:16PM +0800, Xuanqiang Luo wrote:
> > diff --git a/net/ipv4/ip_gre.c b/net/ipv4/ip_gre.c
> > index 82309efd417e0..7b1b0f17f60b9 100644
> > --- a/net/ipv4/ip_gre.c
> > +++ b/net/ipv4/ip_gre.c
> > @@ -1464,6 +1464,9 @@ static int ipgre_changelink(struct net_device *dev, struct nlattr *tb[],
> >   	if (!rtnl_dev_link_net_capable(dev, t->net))
> >   		return -EPERM;
> >   
> > +	if (data && data[IFLA_GRE_COLLECT_METADATA] && !t->collect_md)
> > +		return -EOPNOTSUPP;
> > +
> >   	err = ipgre_newlink_encap_setup(dev, data);
> >   	if (err)
> >   		return err;
> > @@ -1496,6 +1499,9 @@ static int erspan_changelink(struct net_device *dev, struct nlattr *tb[],
> >   	if (!rtnl_dev_link_net_capable(dev, t->net))
> >   		return -EPERM;
> >   
> > +	if (data && data[IFLA_GRE_COLLECT_METADATA] && !t->collect_md)
> > +		return -EOPNOTSUPP;
>
> Both functions have extack, so please add a rejection message to make it
> clear to user space. Something like:
>
> "Enabling collect_md on an existing device is not supported"

Thanks for the suggestion!

I'll address this in v2.

> Also, I assume you audited other tunnels and confirmed that they don't
> suffer from this problem?

Yes, I checked the relevant paths in other tunnels and found no
similar issues.

Thanks,
Xuanqiang