Re: [PATCH bpf-next v2] net: Don't allow to attach xdp if bond slave device's upper already has a program

[Jiri Pirko <jiri@resnulli.us>]

Fri, Aug 23, 2024 at 02:07:45PM CEST, daniel@iogearbox.net wrote:
>On 8/23/24 1:55 PM, Jiri Pirko wrote:
>> Fri, Aug 23, 2024 at 10:42:04AM CEST, zhoufeng.zf@bytedance.com wrote:
>> > From: Feng Zhou <zhoufeng.zf@bytedance.com>
>> > 
>> > Cannot attach when an upper device already has a program, This
>> > restriction is only for bond's slave devices or team port, and
>> > should not be accidentally injured for devices like eth0 and vxlan0.
>> 
>> What if I attach xdp program to solo netdev and then I enslave it
>> to bond/team netdev that already has xdp program attached?
>> What prevents me from doing that?
>
>In that case the enslaving of the device to bond(/team) must fail as
>otherwise the latter won't be able to propagate the XDP prog downwards.

Yep, I don't see that in the code though.


>
>Feng, did you double check if we have net or BPF selftest coverage for
>that? If not might be good to add.
>
>> > Reviewed-by: Toke Høiland-Jørgensen <toke@redhat.com>
>> > Signed-off-by: Feng Zhou <zhoufeng.zf@bytedance.com>
>> > ---
>> > Changelog:
>> > v1->v2: Addressed comments from Paolo Abeni, Jiri Pirko
>> > - Use "netif_is_lag_port" relace of "netif_is_bond_slave"
>> > Details in here:
>> > https://lore.kernel.org/netdev/3bf84d23-a561-47ae-84a4-e99488fc762b@bytedance.com/T/
>> > 
>> > net/core/dev.c | 10 ++++++----
>> > 1 file changed, 6 insertions(+), 4 deletions(-)
>> > 
>> > diff --git a/net/core/dev.c b/net/core/dev.c
>> > index f66e61407883..49144e62172e 100644
>> > --- a/net/core/dev.c
>> > +++ b/net/core/dev.c
>> > @@ -9502,10 +9502,12 @@ static int dev_xdp_attach(struct net_device *dev, struct netlink_ext_ack *extack
>> > 	}
>> > 
>> > 	/* don't allow if an upper device already has a program */
>> > -	netdev_for_each_upper_dev_rcu(dev, upper, iter) {
>> > -		if (dev_xdp_prog_count(upper) > 0) {
>> > -			NL_SET_ERR_MSG(extack, "Cannot attach when an upper device already has a program");
>> > -			return -EEXIST;
>> > +	if (netif_is_lag_port(dev)) {
>> > +		netdev_for_each_upper_dev_rcu(dev, upper, iter) {
>> > +			if (dev_xdp_prog_count(upper) > 0) {
>> > +				NL_SET_ERR_MSG(extack, "Cannot attach when an upper device already has a program");
>> > +				return -EEXIST;
>> > +			}
>> > 		}
>> > 	}
>> > 
>> > -- 
>> > 2.30.2
>> > 
>> 
>