On Fri, Aug 04, 2023 at 05:23:32PM -0700, Martin KaFai Lau wrote:

On 8/3/23 10:07 PM, Geliang Tang wrote:

quoted

Use rand() to generate a random netns name instead of using the fixed
name "mptcp_ns" for every test.

By doing that, we can re-launch the test even if there was an issue
removing the previous netns or if by accident, a netns with this generic
name already existed on the system.

Note that using a different name each will also help adding more
subtests in future commits.

Hi Martin,

I tried to run mptcp tests simultaneously, and got "Cannot create
namespace file "/var/run/netns/mptcp_ns": File exists" errors sometimes.
So I add this patch to fix it.

It's easy to reproduce, just run this commands in multiple terminals:
 > for i in `seq 1 100`; do sudo ./test_progs -t mptcp; done

I run test_progs repeatedly without rebooting qemu to save time. If there is
a test did not clean up its netns, I would rather uncover it earlier and fix
it instead. Randomizing the name is hiding the issue and does not help to
uncover the broken test sooner. Although this change is to mptcp test alone,
this could be referred in other future tests.

I added "ip netns show" after "ip netns del" in v12 to check if there is
a test did not clean up its netns.

Thanks,
-Geliang

afaik, I don't remember bpf CI ever run into a test failure because the
picked name had already been used by the system. It seems you ran into this
issue a lot with the mptcp test in your setup. Could you explain a little
more?