Re: [PATCH bpf-next v4 2/3] bpf, xdp: move offload check into dev_xdp_install()

[Jiayuan Chen <jiayuan.chen@linux.dev>]

On 8/11/26 2:49 AM, Jakub Kicinski wrote:
> On Mon, 10 Aug 2026 13:06:00 +0800 Jiayuan Chen wrote:
>> bpf_xdp_link_update() calls dev_xdp_install() directly and skips
>> dev_xdp_attach(), so the checks in dev_xdp_attach() do not run. A user can
>> make an XDP link with a normal program and then swap in an offloaded or
>> device-bound program with BPF_LINK_UPDATE, which puts it on the software
>> path.
>>
>> Move the three program checks (offloaded, bound to another device, and
>> device-bound in generic mode) from dev_xdp_attach() into
>> dev_xdp_install(), so both the attach path and the link update path are
>> covered.
> Shouldn't we move all the checks that are not explicitly about the
> netlink API (so all but the first?)

Sounds great, the code would be much cleaner.


>
> It may be better to split the series and send this patch to net,
> the netdev CI has a netdevsim test for the prog offload, would be
> good to run that.


Though for now bpf_xdp_link_update() already does:

     if (old_prog->type != new_prog->type ||
         old_prog->expected_attach_type != new_prog->expected_attach_type) {
         err = -EINVAL;
         goto out_unlock;
     }

so the other checks can't be triggered on the update path even without 
them in dev_xdp_install().


So I'm thinking this patch works as a standalone fix (good for 
backport), and the cleanup goes as a followup (if necessary)?