Subject: Re: [PATCH net-next v4 2/3] bpf: Add bpf_current_task_under_cgroup helper

From: Daniel Borkmann <[email-masked]>
Date: Fri, 12 Aug 2016 09:16:07 +0200

On 08/12/2016 06:50 AM, Sargun Dhillon wrote:
> I realize that in_cgroup is more consistent, but under_cgroup makes
> far more sense to me. I think it's more intuitive.
>
> On Thu, Aug 11, 2016 at 9:48 PM, Alexei Starovoitov
> <[email-masked]> wrote:
>> On Thu, Aug 11, 2016 at 08:14:56PM -0700, Sargun Dhillon wrote:
>>> This adds a bpf helper that's similar to the skb_in_cgroup helper to check
>>> whether the probe is currently executing in the context of a specific
>>> subset of the cgroupsv2 hierarchy. It does this based on membership test
>>> for a cgroup arraymap. It is invalid to call this in an interrupt, and
>>> it'll return an error. The helper is primarily to be used in debugging
>>> activities for containers, where you may have multiple programs running in
>>> a given top-level "container".
>>>
>>> Signed-off-by: Sargun Dhillon <[email-masked]>
>>> Cc: Alexei Starovoitov <[email-masked]>
>>> Cc: Daniel Borkmann <[email-masked]>
>>> Cc: Tejun Heo <[email-masked]>
>>> ---
>>> +     /**
>>> +      * bpf_current_task_under_cgroup(map, index) - Check cgroup2 membership of current task
>>> +      * @map: pointer to bpf_map in BPF_MAP_TYPE_CGROUP_ARRAY type
>>> +      * @index: index of the cgroup in the bpf_map
>>> +      * Return:
>>> +      *   == 0 current failed the cgroup2 descendant test
>>> +      *   == 1 current succeeded the cgroup2 descendant test
>>> +      *    < 0 error
>>> +      */
>>> +     BPF_FUNC_current_task_under_cgroup,
>> ..
>>>        case BPF_MAP_TYPE_CGROUP_ARRAY:
>>> -             if (func_id != BPF_FUNC_skb_in_cgroup)
>>> +             if (func_id != BPF_FUNC_skb_in_cgroup &&
>>> +                 func_id != BPF_FUNC_current_task_under_cgroup)
>>>                        goto error;
>> ...
>>> +     case BPF_FUNC_current_task_under_cgroup:
>>>        case BPF_FUNC_skb_in_cgroup:
>>
>> Tejun,
>> do you feel strongly about 'under' ?
>> It just looks inconsistent vs existing skb_in_cgroup...
>> "in cgroup" - 4k google hits
>> "under cgroup" - 2k google hits

Alternative could be that we take "BPF_FUNC_current_in_cgroup" as a
helper enum to keep consistency with what we have wrt skb helper, but
for the cgroup header have the suggested task_under_cgroup_hierarchy()
name.