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

[Xuanqiang Luo <xuanqiang.luo@linux.dev>]

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