This patch adds the backup BPF MPTCP scheduler test. Use sysctl to
set net.mptcp.scheduler to use this sched. Add a veth net device to
simulate the multiple addresses case. Use 'ip mptcp endpoint' command
to add this new endpoint to PM netlink with backup flag. Send data,
check bytes_sent of 'ss' output, and do some cleanups.

Signed-off-by: Geliang Tang <geliang.tang@suse.com>
---
 .../testing/selftests/bpf/prog_tests/mptcp.c  | 35 +++++++++++++++++++
 1 file changed, 35 insertions(+)

diff --git a/tools/testing/selftests/bpf/prog_tests/mptcp.c b/tools/testing/selftests/bpf/prog_tests/mptcp.c
index eaea4105728d..f3c73cd2c786 100644
--- a/tools/testing/selftests/bpf/prog_tests/mptcp.c
+++ b/tools/testing/selftests/bpf/prog_tests/mptcp.c
@@ -7,6 +7,7 @@
 #include "network_helpers.h"
 #include "mptcp_sock.skel.h"
 #include "mptcp_bpf_first.skel.h"
+#include "mptcp_bpf_bkup.skel.h"
 
 #ifndef TCP_CA_NAME_MAX
 #define TCP_CA_NAME_MAX	16
@@ -296,10 +297,44 @@ static void test_first(void)
 	mptcp_bpf_first__destroy(first_skel);
 }
 
+static void test_bkup(void)
+{
+	struct mptcp_bpf_bkup *bkup_skel;
+	int server_fd, client_fd;
+	struct bpf_link *link;
+
+	bkup_skel = mptcp_bpf_bkup__open_and_load();
+	if (!ASSERT_OK_PTR(bkup_skel, "bpf_bkup__open_and_load"))
+		return;
+
+	link = bpf_map__attach_struct_ops(bkup_skel->maps.bkup);
+	if (!ASSERT_OK_PTR(link, "bpf_map__attach_struct_ops")) {
+		mptcp_bpf_bkup__destroy(bkup_skel);
+		return;
+	}
+
+	add_veth();
+	system("ip mptcp endpoint add 10.0.1.1 subflow backup");
+	system("sysctl -qw net.mptcp.scheduler=bpf_bkup");
+	server_fd = start_mptcp_server(AF_INET, NULL, 0, 0);
+	client_fd = connect_to_fd(server_fd, 0);
+
+	send_data(server_fd, client_fd);
+	ASSERT_GT(system("ss -MOenita | grep '10.0.1.1' | grep 'bytes_sent:'"), 0, "ss");
+
+	close(client_fd);
+	close(server_fd);
+	cleanup();
+	bpf_link__destroy(link);
+	mptcp_bpf_bkup__destroy(bkup_skel);
+}
+
 void test_mptcp(void)
 {
 	if (test__start_subtest("base"))
 		test_base();
 	if (test__start_subtest("first"))
 		test_first();
+	if (test__start_subtest("bkup"))
+		test_bkup();
 }
-- 
2.34.1