Re: [PATCH bpf-next v9 4/4] selftests/bpf: Add mptcpify test

[Yonghong Song <yonghong.song@linux.dev>]

On 8/3/23 6:41 AM, 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@tessares.net>
> Signed-off-by: Geliang Tang <geliang.tang@suse.com>
> ---
>   .../testing/selftests/bpf/prog_tests/mptcp.c  | 94 +++++++++++++++++++
>   tools/testing/selftests/bpf/progs/mptcpify.c  | 25 +++++
>   2 files changed, 119 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 4407bd5c9e9a..caab3aa6a162 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];
>   
> @@ -195,8 +196,101 @@ 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, prog_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;
> +
> +	prog_fd = bpf_program__fd(mptcpify_skel->progs.mptcpify);
> +	if (!ASSERT_GE(prog_fd, 0, "bpf_program__fd")) {
> +		err = -EIO;
> +		goto out;
> +	}

load success means prog_fd is always valid. So above
ASSERT_GE not needed.

> +
> +	/* 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();
> +
> +	close(client_fd);
> +close_server:
> +	close(server_fd);
> +out:
> +	mptcpify__destroy(mptcpify_skel);
> +	return err;
> +}
> +
> +static void test_mptcpify(void)
> +{
> +	struct nstoken *nstoken = NULL;
> +	int cgroup_fd;
> +
> +	cgroup_fd = test__join_cgroup("/mptcpify");
> +	if (!ASSERT_GE(cgroup_fd, 0, "test__join_cgroup"))
> +		return;
> +
> +	nstoken = create_netns();
> +	if (!ASSERT_OK_PTR(nstoken, "create_netns"))
> +		goto fail;
> +
> +	ASSERT_OK(run_mptcpify(cgroup_fd), "run_mptcpify");
> +
> +fail:
> +	cleanup_netns(nstoken);
> +	close(cgroup_fd);
> +}
> +
>   void test_mptcp(void)
>   {
>   	if (test__start_subtest("base"))
>   		test_base();
> +	if (test__start_subtest("mptcpify"))
> +		test_mptcpify();
>   }
> diff --git a/tools/testing/selftests/bpf/progs/mptcpify.c b/tools/testing/selftests/bpf/progs/mptcpify.c
> new file mode 100644
> index 000000000000..9cf1febe982d
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/progs/mptcpify.c
> @@ -0,0 +1,25 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/* Copyright (c) 2023, SUSE. */
> +
> +#include <linux/bpf.h>
> +#include <bpf/bpf_tracing.h>
> +
> +char _license[] SEC("license") = "GPL";
> +
> +#define	AF_INET		2
> +#define	AF_INET6	10
> +#define	SOCK_STREAM	1
> +#define	IPPROTO_TCP	6
> +#define	IPPROTO_MPTCP	262

To avoid the above macros, you can use
vmlinux.h and bpf_tracing_net.h.

> +
> +SEC("fmod_ret/update_socket_protocol")
> +int BPF_PROG(mptcpify, int family, int type, int protocol)
> +{
> +	if ((family == AF_INET || family == AF_INET6) &&
> +	    type == SOCK_STREAM &&
> +	    (!protocol || protocol == IPPROTO_TCP)) {
> +		return IPPROTO_MPTCP;
> +	}
> +
> +	return protocol;
> +}