Re: Using pinned maps within a network namespace

On Tue, Sep 15, 2020 at 11:46 AM John McDowall
<[email protected]> wrote:
>
> Hi everyone,
>
> This may be a dumb question, I have set up a simple test environment
> with multiple network namespaces running on a ubuntu 20.04 vagrant
> box, with the latest github libbpf.
>
> I want to use a pinned map, I can make /sys/fs/bpf shared by:
>
> $ mount mount --make-shared /sys/fs/bpf
> $ mount --bind /sys/fs/bpf /sys/fs/bpf

Similar commands `mount --bind /sys/fs/bpf /sys/fs/bpf1` in the same namespace
works fine.

Maybe there are restrictions related to namespace? Maybe it becomes readonly?
Could you print out the error code below?

>
> but when I try access the maps from a C program running in a namespace
> using bpf I get
>
>  Access to /sys/fs/bpf/lwtconfig map failed obj_pin errno: No such
> file or directory
>
> The code snippet is:
>
> mapfd = bpf_obj_pin(pin_fd,CONFIG_MAP_PATH);
>         if (mapfd < 0) {
>             jed_info(jed_logfile,"Access to %s map failed obj_pin ",
> CONFIG_MAP_PATH);
>             pin_fd = bpf_obj_get(CONFIG_MAP_PATH);
>             if (pin_fd < 0){
>              jed_error(jed_logfile,"Access to %s map failed with
> obj_get ", CONFIG_MAP_PATH);
>             }
>         }
>
> Is this possible, and if so what am I missing?
>
> Regards
>
> John