From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D241213C677 for ; Thu, 15 Aug 2024 21:00:07 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1723755607; cv=none; b=AjY0jXHbi+iS+RM791vgLGVbFtFRiH6wK/3habzOct3CwxX75z70pPAvLcFW4DO+XVdxZMAf5NdlpdYbvkl5XG8FbuaAWvNixTjzBDKpR5zyBsF/hcTo6RnnDIozIuuyMK+iIE5h53E8+qdCtYmFrm8Gog3Z2eNG2af1tg91/sc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1723755607; c=relaxed/simple; bh=HydlqhyV1Ful9Sat+nBNm8+q0+h5c1v94FLryjyH7uk=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=il8oJrQXV+xv5vP2B142PoZTBycHyMFKCm1A2xIReOsGGpzsOQh25g8+lcS7BXgwrWujW+P8xcQ5X5qRiqRZ8YU9+zSFxk8/zU2GAkGqYseuMuplheX4rM9tvGKA138Z7sFi6c3/fNSNNCvnA68sjMaNh4KUOFjolKt0R7kzyxE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=jpf/LxkZ; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="jpf/LxkZ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C21D8C32786; Thu, 15 Aug 2024 21:00:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1723755607; bh=HydlqhyV1Ful9Sat+nBNm8+q0+h5c1v94FLryjyH7uk=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=jpf/LxkZtaGgRO6II+EI5o8Ga6OCp4V/e5gBL5usu1kpftIjIPvlpXdt4NSbYJdbo AhywGgk7S9Jtvm4DtuwZA84wzYdpYcREnbLBXlNVek4bYcBZvkyzqKnihvof7y2uqr mx+UxUGqKa6+VWI7Rr4iRaOv1T5XqYuUXUaDpENfe45deWys0Tja8HEMWr3TQImv3O 5oH+ISNtrGDqkO0U4CgCV23u2LuijDVHBd75kOSLnU2kN6N7X2Z/cse6v+mB2C+DWs +CUoXmDHuDMLRL9KaUL3XHZCee5WeD6HlZCkwYIqHZNJyXnTAFQpaZYBEhDxRtEL5a MMDkdLGBO0wmw== Message-ID: Date: Thu, 15 Aug 2024 23:00:05 +0200 Precedence: bulk X-Mailing-List: mptcp@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Beta Subject: Re: [PATCH bpf-next v4 2/2] selftests/bpf: Add mptcp subflow subtest Content-Language: en-GB To: Geliang Tang Cc: mptcp@lists.linux.dev References: <20240805-upstream-bpf-next-20240506-mptcp-subflow-test-v4-0-2b4ca6994993@kernel.org> <20240805-upstream-bpf-next-20240506-mptcp-subflow-test-v4-2-2b4ca6994993@kernel.org> <2136317a-3e95-4993-b2fc-1f3b2c28dbdc@linux.dev> <8a2ff1bd-52dc-421d-87b7-fc2f56e81da2@kernel.org> <716cbd56-4a44-4451-a6f3-5bacef3e0729@linux.dev> From: Matthieu Baerts Autocrypt: addr=matttbe@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 8bit Hi Geliang, (only the MPTCP list) On 15/08/2024 00:37, Martin KaFai Lau wrote: > On 8/14/24 3:04 AM, Matthieu Baerts wrote: >> Hi Martin, >> >> Thank you for your reply! >> >> On 14/08/2024 03:12, Martin KaFai Lau wrote: >>> On 8/5/24 2:52 AM, Matthieu Baerts (NGI0) wrote: (...) >>>> +    ASSERT_OK(ss_search(ADDR_1, "fwmark:0x1"), "ss_search >>>> fwmark:0x1"); >>>> +    ASSERT_OK(ss_search(ADDR_2, "fwmark:0x2"), "ss_search >>>> fwmark:0x2"); >>>> +    ASSERT_OK(ss_search(ADDR_1, new), "ss_search new cc"); >>>> +    ASSERT_OK(ss_search(ADDR_2, cc), "ss_search default cc"); >>> >>> Is there a getsockopt way instead of ss + grep? >> >> No there isn't: from the userspace, the app communicates with the MPTCP >> socket, which can have multiple paths (subflows, a TCP socket). To keep >> the compatibility with TCP, [gs]etsockopt() will look at/modify the >> whole MPTCP connection. For example, in some cases, a setsockopt() will >> propagate the option to all the subflows. Depending on the option, the >> modification might only apply to the first subflow, or to the >> user-facing socket. >> >> For advanced users who want to have different options set to the >> different subflows of an MPTCP connection, they can use BPF: that's what >> is being validated here. In other words, doing a 'getsockopt()' from the >> userspace program here will not show all the different marks and TCP CC >> that can be set per subflow with BPF. We can see that in the test: a >> getsockopt() is done on the MPTCP socket to retrieve the default TCP CC >> ('cc' which is certainly 'cubic'), but we expect to find another one >> ('new' which is 'reno'), set by the BPF program from patch 1/2. I guess >> we could use bpf to do a getsockopt() per subflow, but that's seems a >> bit cheated to have the BPF test program setting something and checking >> if it is set. Here, it is an external way. Because it is done from a > > I think the result is valid by having a bpf prog to inspect the value of > a sock. Inspecting socket is an existing use case. There are many > existing bpf tests covering this inspection use case to ensure the > result is legit. A separate cgroup/getsockopt program should help here > (more on this below). > >> dedicated netns, it sounds OK to do that, no? > > Thanks for the explanation. I was hoping there is a way to get to the > underlying subflow fd. It seems impossible. > > In the netns does help here. It is not only about the ss iterating a lot > of connections or not. My preference is not depending on external tool/ > shell-ing if possible, e.g. to avoid the package update discussion like > the iproute2 here. The uapi from the testing kernel is always up-to- > date. ss is another binary but arguably in the same iproute2 package. > There is now another extra "grep" and pipe here. We had been bitten by > different shell behaviors and some arch has different shells ...etc. > > I think it is ok to take this set as is if you (and Gelang?) are ok to > followup a "cgroup/getsockopt" way to inspect the subflow as the very > next patch to the mptcp selftest. It seems inspecting subflow will be a > common test going forward for mptcp, so it will be beneficial to have a > "cgroup/getsockopt" way to inspect the subflow directly. > > Take a look at a recent example [0]. The mptcp test is under a cgroup > already and has the cgroup setup. An extra "cgroup/getsockopt" prog > should be enough. That prog can walk the msk->conn_list and use > bpf_rdonly_cast (or the bpf_core_cast macro in libbpf) to cast a pointer > to tcp_sock for readonly. It will allow to inspect all the fields in a > tcp_sock. Do you think it is something that you could do to replace the validations with 'ss', and maybe help with future validations for the BPF packet schedulers? > Something needs to a fix in patch 2(replied separately), so a re-spin is > needed. > > pw-bot: cr > > [0]: https://lore.kernel.org/all/20240808150558.1035626-3- > alan.maguire@oracle.com/ > > > Cheers, Matt -- Sponsored by the NGI0 Core fund.