Song,
You are right the issue is that in a new namespace /sys/fs/bpf is readonly.
On host system (Centos 8.2)
[jmcdowall@jed102 framework]$ ls -al /sys/fs
total 0
drwxr-xr-x. 9 root root 0 Jul 15 16:01 .
dr-xr-xr-x. 13 root root 0 Jul 15 16:02 ..
drwx-----T. 2 root root 0 Jul 15 16:01 bpf
drwxr-xr-x. 14 root root 360 Jul 15 16:01 cgroup
drwxr-xr-x. 4 root root 0 Jul 22 11:58 ext4
drwxr-xr-x. 3 root root 0 Jul 16 11:05 fuse
drwxr-x---. 2 root root 0 Jul 15 16:01 pstore
drwxr-xr-x. 7 root root 0 Jul 15 16:01 selinux
drwxr-xr-x. 5 root root 0 Jul 29 18:58 xfs
[jmcdowall@jed102 framework]$
Then create a network namespace
[jmcdowall@jed102 framework]$ sudo ip netns add test
[sudo] password for jmcdowall:
[jmcdowall@jed102 framework]$ sudo ip netns exec test ls -la /sys/fs
total 0
drwxr-xr-x. 9 root root 0 Sep 25 14:31 .
dr-xr-xr-x. 13 root root 0 Jul 15 16:02 ..
dr-xr-xr-x. 2 root root 0 Sep 25 14:31 bpf
dr-xr-xr-x. 2 root root 0 Sep 25 14:31 cgroup
drwxr-xr-x. 4 root root 0 Sep 25 14:31 ext4
drwxr-xr-x. 3 root root 0 Sep 25 14:31 fuse
dr-xr-xr-x. 2 root root 0 Sep 25 14:31 pstore
dr-xr-xr-x. 2 root root 0 Sep 25 14:31 selinux
drwxr-xr-x. 5 root root 0 Sep 25 14:31 xfs
[jmcdowall@jed102 framework]$
and the bpf directory is readonly.
There does not seem to be a way to make the directory writable.
Does anyone have any ideas?
Regards
John
On Tue, Sep 15, 2020 at 10:12 PM Y Song <ys114321@xxxxxxxxx> wrote:
>
> On Tue, Sep 15, 2020 at 11:46 AM John McDowall
> <jmcdowall@xxxxxxxxxxxxxxxxxxxx> 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
|