Frozen Maps

Frozen Maps

[Abhishek Vijeev]

Hi,

From a user-space process, given a BPF map file descriptor, is it
possible to determine whether the map is frozen (with BPF_MAP_FREEZE)?

As far as I'm aware, the only way to retrieve information about BPF
maps from file descriptors is to use BPF_OBJ_GET_INFO_BY_FD. However,
I do not see a field which tells me whether a map is frozen (or not)
in struct bpf_map_info
(https://github.com/torvalds/linux/blob/master/include/uapi/linux/bpf.h#L4035).
Kindly correct me if I'm wrong.

Thank you,
Abhishek Vijeev.

Re: Frozen Maps

[David Ahern]

On 8/27/20 9:59 AM, Abhishek Vijeev wrote:
> Hi,
> 
> From a user-space process, given a BPF map file descriptor, is it
> possible to determine whether the map is frozen (with BPF_MAP_FREEZE)?
> 
> As far as I'm aware, the only way to retrieve information about BPF
> maps from file descriptors is to use BPF_OBJ_GET_INFO_BY_FD. However,
> I do not see a field which tells me whether a map is frozen (or not)
> in struct bpf_map_info
> (https://github.com/torvalds/linux/blob/master/include/uapi/linux/bpf.h#L4035).
> Kindly correct me if I'm wrong.
> 
> Thank you,
> Abhishek Vijeev.
> 

fdinfo for the file has the frozen status (cat /proc/$pid/fdinfo/$fd)

Re: Frozen Maps

[Abhishek Vijeev]

Thank you.

To confirm, is this the only way?

On Thu, Aug 27, 2020 at 10:13 PM Abhishek Vijeev
<abhishek.vijeev@gmail.com> wrote:
>
> Thank you.
>
> To confirm, is this the only way?
>
> On Thu, Aug 27, 2020, 9:54 PM David Ahern <dsahern@gmail.com> wrote:
>>
>> On 8/27/20 9:59 AM, Abhishek Vijeev wrote:
>> > Hi,
>> >
>> > From a user-space process, given a BPF map file descriptor, is it
>> > possible to determine whether the map is frozen (with BPF_MAP_FREEZE)?
>> >
>> > As far as I'm aware, the only way to retrieve information about BPF
>> > maps from file descriptors is to use BPF_OBJ_GET_INFO_BY_FD. However,
>> > I do not see a field which tells me whether a map is frozen (or not)
>> > in struct bpf_map_info
>> > (https://github.com/torvalds/linux/blob/master/include/uapi/linux/bpf.h#L4035).
>> > Kindly correct me if I'm wrong.
>> >
>> > Thank you,
>> > Abhishek Vijeev.
>> >
>>
>> fdinfo for the file has the frozen status (cat /proc/$pid/fdinfo/$fd)

Re: Frozen Maps

[David Ahern]

On 8/27/20 10:43 AM, Abhishek Vijeev wrote:
> Thank you.
> 
> To confirm, is this the only way?

appears so from a code review. I am surprised it is not in GET_INFO
response.

Re: Frozen Maps

[Abhishek Vijeev]

Yes, that's precisely why I reached out.

Thank you.

On Thu, Aug 27, 2020 at 10:19 PM David Ahern <dsahern@gmail.com> wrote:
>
> On 8/27/20 10:43 AM, Abhishek Vijeev wrote:
> > Thank you.
> >
> > To confirm, is this the only way?
>
> appears so from a code review. I am surprised it is not in GET_INFO
> response.