netdev - Re: [PATCH bpf-next v10 5/5] selftests/bpf: Add mptcpify test

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Date: Thu, 3 Aug 2023 21:43:07 -0700
From: Yonghong Song <yonghong.song@...ux.dev>
To: Geliang Tang <geliang.tang@...e.com>, Alexei Starovoitov
 <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>,
 Andrii Nakryiko <andrii@...nel.org>, Martin KaFai Lau
 <martin.lau@...ux.dev>, Song Liu <song@...nel.org>,
 Yonghong Song <yhs@...com>, John Fastabend <john.fastabend@...il.com>,
 KP Singh <kpsingh@...nel.org>, Stanislav Fomichev <sdf@...gle.com>,
 Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>,
 Florent Revest <revest@...omium.org>, Brendan Jackman
 <jackmanb@...omium.org>, Matthieu Baerts <matthieu.baerts@...sares.net>,
 Mat Martineau <martineau@...nel.org>, "David S. Miller"
 <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
 John Johansen <john.johansen@...onical.com>, Paul Moore
 <paul@...l-moore.com>, James Morris <jmorris@...ei.org>,
 "Serge E. Hallyn" <serge@...lyn.com>,
 Stephen Smalley <stephen.smalley.work@...il.com>,
 Eric Paris <eparis@...isplace.org>, Mykola Lysenko <mykolal@...com>,
 Shuah Khan <shuah@...nel.org>, Simon Horman <horms@...nel.org>
Cc: bpf@...r.kernel.org, netdev@...r.kernel.org, mptcp@...ts.linux.dev,
 apparmor@...ts.ubuntu.com, linux-security-module@...r.kernel.org,
 selinux@...r.kernel.org, linux-kselftest@...r.kernel.org
Subject: Re: [PATCH bpf-next v10 5/5] selftests/bpf: Add mptcpify test



On 8/3/23 6:55 PM, Geliang Tang wrote:
> Implement a new test program mptcpify: if the family is AF_INET or
> AF_INET6, the type is SOCK_STREAM, and the protocol ID is 0 or
> IPPROTO_TCP, set it to IPPROTO_MPTCP. It will be hooked in
> update_socket_protocol().
> 
> Extend the MPTCP test base, add a selftest test_mptcpify() for the
> mptcpify case. Open and load the mptcpify test prog to mptcpify the
> TCP sockets dynamically, then use start_server() and connect_to_fd()
> to create a TCP socket, but actually what's created is an MPTCP
> socket, which can be verified through the outputs of 'ss' and 'nstat'
> commands.
> 
> Reviewed-by: Matthieu Baerts <matthieu.baerts@...sares.net>
> Signed-off-by: Geliang Tang <geliang.tang@...e.com>

Ack with a minor nit below.

Acked-by: Yonghong Song <yonghong.song@...ux.dev>

> ---
>   .../testing/selftests/bpf/prog_tests/mptcp.c  | 88 +++++++++++++++++++
>   tools/testing/selftests/bpf/progs/mptcpify.c  | 20 +++++
>   2 files changed, 108 insertions(+)
>   create mode 100644 tools/testing/selftests/bpf/progs/mptcpify.c
> 
> diff --git a/tools/testing/selftests/bpf/prog_tests/mptcp.c b/tools/testing/selftests/bpf/prog_tests/mptcp.c
> index 3dc0ba2e7590..e5ac2c3aab7d 100644
> --- a/tools/testing/selftests/bpf/prog_tests/mptcp.c
> +++ b/tools/testing/selftests/bpf/prog_tests/mptcp.c
> @@ -6,6 +6,7 @@
>   #include "cgroup_helpers.h"
>   #include "network_helpers.h"
>   #include "mptcp_sock.skel.h"
> +#include "mptcpify.skel.h"
>   
>   char NS_TEST[32];
>   
> @@ -185,8 +186,95 @@ static void test_base(void)
>   	close(cgroup_fd);
>   }
>   
> +static void send_byte(int fd)
> +{
> +	char b = 0x55;
> +
> +	ASSERT_EQ(write(fd, &b, sizeof(b)), 1, "send single byte");
> +}
> +
> +static int verify_mptcpify(void)
> +{
> +	char cmd[256];
> +	int err = 0;
> +
> +	snprintf(cmd, sizeof(cmd),
> +		 "ip netns exec %s ss -tOni | grep -q '%s'",
> +		 NS_TEST, "tcp-ulp-mptcp");
> +	if (!ASSERT_OK(system(cmd), "No tcp-ulp-mptcp found!"))
> +		err++;
> +
> +	snprintf(cmd, sizeof(cmd),
> +		 "ip netns exec %s nstat -asz %s | awk '%s' | grep -q '%s'",
> +		 NS_TEST, "MPTcpExtMPCapableSYNACKRX",
> +		 "NR==1 {next} {print $2}", "1");
> +	if (!ASSERT_OK(system(cmd), "No MPTcpExtMPCapableSYNACKRX found!"))
> +		err++;
> +
> +	return err;
> +}
> +
> +static int run_mptcpify(int cgroup_fd)
> +{
> +	int server_fd, client_fd, err = 0;
> +	struct mptcpify *mptcpify_skel;
> +
> +	mptcpify_skel = mptcpify__open_and_load();
> +	if (!ASSERT_OK_PTR(mptcpify_skel, "skel_open_load"))
> +		return -EIO;
> +
> +	err = mptcpify__attach(mptcpify_skel);
> +	if (!ASSERT_OK(err, "skel_attach"))
> +		goto out;
> +
> +	/* without MPTCP */
> +	server_fd = start_server(AF_INET, SOCK_STREAM, NULL, 0, 0);
> +	if (!ASSERT_GE(server_fd, 0, "start_server")) {
> +		err = -EIO;
> +		goto out;
> +	}
> +
> +	client_fd = connect_to_fd(server_fd, 0);
> +	if (!ASSERT_GE(client_fd, 0, "connect to fd")) {
> +		err = -EIO;
> +		goto close_server;
> +	}
> +
> +	send_byte(client_fd);
> +	err += verify_mptcpify();

The above code essentially equals to
	err = verify_mptcpify()
since err must be 0 before the above code.
I think it is worthwhile to change the above to
	err = verify_mptcpify();

Otherwise, people may confuse that maybe err could be
non-zero before send_byte(client_fd)? If this is the
case, why we did not return earlier? The code
	err = verify_mptcpify()
will make it clear that all previous error
conditions have been handled properly.

> +
> +	close(client_fd);
> +close_server:
> +	close(server_fd);
> +out:
> +	mptcpify__destroy(mptcpify_skel);
> +	return err;
> +}
> +
[...]