netdev - Re: [PATCH bpf-next v2 4/5] bpf: selftests: add MPTCP test base

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Date:   Tue, 15 Sep 2020 17:18:56 +0000
From:   Song Liu <songliubraving@...com>
To:     Nicolas Rybowski <nicolas.rybowski@...sares.net>
CC:     Song Liu <song@...nel.org>, Shuah Khan <shuah@...nel.org>,
        "Alexei Starovoitov" <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        "Martin Lau" <kafai@...com>, Yonghong Song <yhs@...com>,
        Andrii Nakryiko <andriin@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...omium.org>,
        Matthieu Baerts <matthieu.baerts@...sares.net>,
        "open list" <linux-kernel@...r.kernel.org>,
        "linux-kselftest@...r.kernel.org" <linux-kselftest@...r.kernel.org>,
        Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>
Subject: Re: [PATCH bpf-next v2 4/5] bpf: selftests: add MPTCP test base



> On Sep 15, 2020, at 9:35 AM, Nicolas Rybowski <nicolas.rybowski@...sares.net> wrote:
> 
> Hi Song,
> 
> Thanks for the feedback !
> 
> On Mon, Sep 14, 2020 at 8:07 PM Song Liu <song@...nel.org> wrote:
>> 
>> On Fri, Sep 11, 2020 at 8:02 AM Nicolas Rybowski
>> <nicolas.rybowski@...sares.net> wrote:
>>> 
>>> This patch adds a base for MPTCP specific tests.
>>> 
>>> It is currently limited to the is_mptcp field in case of plain TCP
>>> connection because for the moment there is no easy way to get the subflow
>>> sk from a msk in userspace. This implies that we cannot lookup the
>>> sk_storage attached to the subflow sk in the sockops program.
>>> 
>>> Acked-by: Matthieu Baerts <matthieu.baerts@...sares.net>
>>> Signed-off-by: Nicolas Rybowski <nicolas.rybowski@...sares.net>
>> 
>> Acked-by: Song Liu <songliubraving@...com>
>> 
>> With some nitpicks below.
>> 
>>> ---
>>> 
>>> Notes:
>>>    v1 -> v2:
>>>    - new patch: mandatory selftests (Alexei)
>>> 
>> [...]
>>>                     int timeout_ms);
>>> diff --git a/tools/testing/selftests/bpf/prog_tests/mptcp.c b/tools/testing/selftests/bpf/prog_tests/mptcp.c
>>> new file mode 100644
>>> index 000000000000..0e65d64868e9
>>> --- /dev/null
>>> +++ b/tools/testing/selftests/bpf/prog_tests/mptcp.c
>>> @@ -0,0 +1,119 @@
>>> +// SPDX-License-Identifier: GPL-2.0
>>> +#include <test_progs.h>
>>> +#include "cgroup_helpers.h"
>>> +#include "network_helpers.h"
>>> +
>>> +struct mptcp_storage {
>>> +       __u32 invoked;
>>> +       __u32 is_mptcp;
>>> +};
>>> +
>>> +static int verify_sk(int map_fd, int client_fd, const char *msg, __u32 is_mptcp)
>>> +{
>>> +       int err = 0, cfd = client_fd;
>>> +       struct mptcp_storage val;
>>> +
>>> +       /* Currently there is no easy way to get back the subflow sk from the MPTCP
>>> +        * sk, thus we cannot access here the sk_storage associated to the subflow
>>> +        * sk. Also, there is no sk_storage associated with the MPTCP sk since it
>>> +        * does not trigger sockops events.
>>> +        * We silently pass this situation at the moment.
>>> +        */
>>> +       if (is_mptcp == 1)
>>> +               return 0;
>>> +
>>> +       if (CHECK_FAIL(bpf_map_lookup_elem(map_fd, &cfd, &val) < 0)) {
>>> +               perror("Failed to read socket storage");
>> 
>> Maybe simplify this with CHECK(), which contains a customized error message?
>> Same for some other calls.
>> 
> 
> The whole logic here is strongly inspired from prog_tests/tcp_rtt.c
> where CHECK_FAIL is used.
> Also the CHECK macro will print a PASS message on successful map
> lookup, which is not expected at this point of the tests.
> I think it would be more interesting to leave it as it is to keep a
> cohesion between TCP and MPTCP selftests. What do you think?

I guess CHECK_FAIL makes sense when we don't need the PASS message. 
Let's keep this part as-is then. 

Thanks,
Song