This patch extended the MPTCP test base, to exercise the new helper
bpf_skc_to_mptcp_sock() from C test as Alexei suggested in [1].

Added a new function verify_msk() to verify the msk token, and a new
function get_msk_token() to parse the msk token from the output of the
command 'ip mptcp monitor'.

[1]
https://lore.kernel.org/netdev/20200922040830.3iis6xiavhvpfq3v@ast-mbp.dhcp.thefacebook.com/

Co-developed-by: Nicolas Rybowski <nicolas.rybowski@tessares.net>
Signed-off-by: Nicolas Rybowski <nicolas.rybowski@tessares.net>
Co-developed-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Signed-off-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Signed-off-by: Geliang Tang <geliang.tang@suse.com>
---
 tools/testing/selftests/bpf/bpf_tcp_helpers.h |  6 ++
 .../testing/selftests/bpf/prog_tests/mptcp.c  | 94 +++++++++++++++++--
 tools/testing/selftests/bpf/progs/mptcp.c     | 22 +++++
 3 files changed, 116 insertions(+), 6 deletions(-)

diff --git a/tools/testing/selftests/bpf/bpf_tcp_helpers.h b/tools/testing/selftests/bpf/bpf_tcp_helpers.h
index b1ede6f0b821..05f62f81cc4d 100644
--- a/tools/testing/selftests/bpf/bpf_tcp_helpers.h
+++ b/tools/testing/selftests/bpf/bpf_tcp_helpers.h
@@ -83,6 +83,12 @@ struct tcp_sock {
 	__u64	tcp_mstamp;	/* most recent packet received/sent */
 } __attribute__((preserve_access_index));
 
+struct mptcp_sock {
+	struct inet_connection_sock	sk;
+
+	__u32	token;
+} __attribute__((preserve_access_index));
+
 static __always_inline struct inet_connection_sock *inet_csk(const struct sock *sk)
 {
 	return (struct inet_connection_sock *)sk;
diff --git a/tools/testing/selftests/bpf/prog_tests/mptcp.c b/tools/testing/selftests/bpf/prog_tests/mptcp.c
index 87ee7bd8a689..3dce2431fdf3 100644
--- a/tools/testing/selftests/bpf/prog_tests/mptcp.c
+++ b/tools/testing/selftests/bpf/prog_tests/mptcp.c
@@ -3,19 +3,20 @@
 #include "cgroup_helpers.h"
 #include "network_helpers.h"
 
+char monitor_log_path[64];
+
 struct mptcp_storage {
 	__u32 invoked;
 	__u32 is_mptcp;
+	__u32 token;
 };
 
-static int verify_sk(int map_fd, int client_fd, const char *msg, __u32 is_mptcp)
+static int verify_tsk(int map_fd, int client_fd)
 {
+	char *msg = "plain TCP socket";
 	int err = 0, cfd = client_fd;
 	struct mptcp_storage val;
 
-	if (is_mptcp == 1)
-		return 0;
-
 	if (CHECK_FAIL(bpf_map_lookup_elem(map_fd, &cfd, &val) < 0)) {
 		perror("Failed to read socket storage");
 		return -1;
@@ -36,6 +37,77 @@ static int verify_sk(int map_fd, int client_fd, const char *msg, __u32 is_mptcp)
 	return err;
 }
 
+static __u32 get_msk_token(void)
+{
+	char *prefix = "[       CREATED] token=";
+	char buf[64] = {};
+	__u32 token = 0;
+	ssize_t len;
+	int fd;
+
+	fd = open(monitor_log_path, O_RDONLY);
+	if (CHECK_FAIL(fd < 0)) {
+		log_err("Failed to open %s", monitor_log_path);
+		goto err;
+	}
+
+	len = read(fd, buf, sizeof(buf));
+	if (CHECK_FAIL(len < 0)) {
+		log_err("Failed to read %s", monitor_log_path);
+		goto err;
+	}
+
+	if (strncmp(buf, prefix, strlen(prefix))) {
+		log_err("Invalid prefix %s", buf);
+		goto err;
+	}
+
+	token = strtol(buf + strlen(prefix), NULL, 16);
+
+err:
+	close(fd);
+	return token;
+}
+
+static int verify_msk(int map_fd, int client_fd)
+{
+	char *msg = "MPTCP subflow socket";
+	int err = 0, cfd = client_fd;
+	struct mptcp_storage val;
+	__u32 token;
+
+	token = get_msk_token();
+	if (token <= 0) {
+		log_err("Unexpected token %x", token);
+		return -1;
+	}
+
+	if (CHECK_FAIL(bpf_map_lookup_elem(map_fd, &cfd, &val) < 0)) {
+		perror("Failed to read socket storage");
+		return -1;
+	}
+
+	if (val.invoked != 1) {
+		log_err("%s: unexpected invoked count %d != 1",
+			msg, val.invoked);
+		err++;
+	}
+
+	if (val.is_mptcp != 1) {
+		log_err("%s: unexpected bpf_tcp_sock.is_mptcp %d != 1",
+			msg, val.is_mptcp);
+		err++;
+	}
+
+	if (val.token != token) {
+		log_err("Unexpected mptcp_sock.token %x != %x",
+			val.token, token);
+		err++;
+	}
+
+	return err;
+}
+
 static int run_test(int cgroup_fd, int server_fd, bool is_mptcp)
 {
 	int client_fd, prog_fd, map_fd, err;
@@ -70,8 +142,8 @@ static int run_test(int cgroup_fd, int server_fd, bool is_mptcp)
 		goto close_client_fd;
 	}
 
-	err += is_mptcp ? verify_sk(map_fd, client_fd, "MPTCP subflow socket", 1) :
-			  verify_sk(map_fd, client_fd, "plain TCP socket", 0);
+	err += is_mptcp ? verify_msk(map_fd, client_fd) :
+			  verify_tsk(map_fd, client_fd);
 
 close_client_fd:
 	close(client_fd);
@@ -83,6 +155,7 @@ static int run_test(int cgroup_fd, int server_fd, bool is_mptcp)
 
 void test_mptcp(void)
 {
+	char cmd[256], tmp_dir[] = "/tmp/XXXXXX";
 	int server_fd, cgroup_fd;
 
 	cgroup_fd = test__join_cgroup("/mptcp");
@@ -100,6 +173,13 @@ void test_mptcp(void)
 
 with_mptcp:
 	/* with MPTCP */
+	if (CHECK_FAIL(!mkdtemp(tmp_dir)))
+		goto close_cgroup_fd;
+	snprintf(monitor_log_path, sizeof(monitor_log_path),
+		 "%s/ip_mptcp_monitor", tmp_dir);
+	snprintf(cmd, sizeof(cmd), "ip mptcp monitor > %s &", monitor_log_path);
+	if (CHECK_FAIL(system(cmd)))
+		goto close_cgroup_fd;
 	server_fd = start_mptcp_server(AF_INET, NULL, 0, 0);
 	if (CHECK_FAIL(server_fd < 0))
 		goto close_cgroup_fd;
@@ -107,6 +187,8 @@ void test_mptcp(void)
 	CHECK_FAIL(run_test(cgroup_fd, server_fd, true));
 
 	close(server_fd);
+	snprintf(cmd, sizeof(cmd), "rm -rf %s", tmp_dir);
+	system(cmd);
 
 close_cgroup_fd:
 	close(cgroup_fd);
diff --git a/tools/testing/selftests/bpf/progs/mptcp.c b/tools/testing/selftests/bpf/progs/mptcp.c
index be5ee8dac2b3..bb0a9ec534b0 100644
--- a/tools/testing/selftests/bpf/progs/mptcp.c
+++ b/tools/testing/selftests/bpf/progs/mptcp.c
@@ -1,6 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0
 #include <linux/bpf.h>
 #include <bpf/bpf_helpers.h>
+#include "bpf_tcp_helpers.h"
 
 char _license[] SEC("license") = "GPL";
 __u32 _version SEC("version") = 1;
@@ -8,6 +9,7 @@ __u32 _version SEC("version") = 1;
 struct mptcp_storage {
 	__u32 invoked;
 	__u32 is_mptcp;
+	__u32 token;
 };
 
 struct {
@@ -43,6 +45,26 @@ int _sockops(struct bpf_sock_ops *ctx)
 
 	storage->invoked++;
 	storage->is_mptcp = tcp_sk->is_mptcp;
+	storage->token = 0;
+
+	if (tcp_sk->is_mptcp) {
+		char fmt[] = "msk=%p token=%x\n";
+		struct mptcp_sock *msk;
+
+		msk = bpf_skc_to_mptcp_sock(sk);
+		if (!msk)
+			return 1;
+
+		storage = bpf_sk_storage_get(&socket_storage_map, msk, 0,
+					     BPF_SK_STORAGE_GET_F_CREATE);
+		if (!storage)
+			return 1;
+
+		storage->invoked++;
+		storage->is_mptcp = 1;
+		storage->token = msk->token;
+		bpf_trace_printk(fmt, sizeof(fmt), msk, storage->token);
+	}
 
 	return 1;
 }
-- 
2.34.1