Re: [PATCH bpf-next] selftests/bpf: Restore the netns after flow dissector reattach test

[Martin Lau <kafai@fb.com>]

On Thu, Oct 17, 2019 at 10:37:52AM +0200, Jakub Sitnicki wrote:
> flow_dissector_reattach test changes the netns we run in but does not
> restore it to the one we started in when finished. This interferes with
> tests that run after it. Fix it by restoring the netns when done.
> 
> Fixes: f97eea1756f3 ("selftests/bpf: Check that flow dissector can be re-attached")
> Reported-by: Alexei Starovoitov <ast@kernel.org>
> Reported-by: Andrii Nakryiko <andriin@fb.com>
> Signed-off-by: Jakub Sitnicki <jakub@cloudflare.com>
> ---
>  .../bpf/prog_tests/flow_dissector_reattach.c  | 21 +++++++++++++++----
>  1 file changed, 17 insertions(+), 4 deletions(-)
> 
> diff --git a/tools/testing/selftests/bpf/prog_tests/flow_dissector_reattach.c b/tools/testing/selftests/bpf/prog_tests/flow_dissector_reattach.c
> index 777faffc4639..1f51ba66b98b 100644
> --- a/tools/testing/selftests/bpf/prog_tests/flow_dissector_reattach.c
> +++ b/tools/testing/selftests/bpf/prog_tests/flow_dissector_reattach.c
> @@ -91,12 +91,18 @@ static void do_flow_dissector_reattach(void)
>  
>  void test_flow_dissector_reattach(void)
>  {
> -	int init_net, err;
> +	int init_net, self_net, err;
> +
> +	self_net = open("/proc/self/ns/net", O_RDONLY);
> +	if (CHECK_FAIL(self_net < 0)) {
> +		perror("open(/proc/self/ns/net");
> +		return;
> +	}
>  
>  	init_net = open("/proc/1/ns/net", O_RDONLY);
>  	if (CHECK_FAIL(init_net < 0)) {
>  		perror("open(/proc/1/ns/net)");
> -		return;
> +		goto out_close;
Mostly nit.  close(-1) is ok-ish...  The same goes for the "out_close" in
do_flow_dissector_reattach().

Acked-by: Martin KaFai Lau <kafai@fb.com>

>  	}
>  
>  	err = setns(init_net, CLONE_NEWNET);
> @@ -108,7 +114,7 @@ void test_flow_dissector_reattach(void)
>  	if (is_attached(init_net)) {
>  		test__skip();
>  		printf("Can't test with flow dissector attached to init_net\n");
> -		return;
> +		goto out_setns;
>  	}
>  
>  	/* First run tests in root network namespace */
> @@ -118,10 +124,17 @@ void test_flow_dissector_reattach(void)
>  	err = unshare(CLONE_NEWNET);
>  	if (CHECK_FAIL(err)) {
>  		perror("unshare(CLONE_NEWNET)");
> -		goto out_close;
> +		goto out_setns;
>  	}
>  	do_flow_dissector_reattach();
>  
> +out_setns:
> +	/* Move back to netns we started in. */
> +	err = setns(self_net, CLONE_NEWNET);
> +	if (CHECK_FAIL(err))
> +		perror("setns(/proc/self/ns/net)");
> +
>  out_close:
>  	close(init_net);
> +	close(self_net);
>  }
> -- 
> 2.20.1
>