selftests/bpf: Add bpf_rr test

This patch adds the round-robin 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. Send data and check bytes_sent of
'ss' output after it to make sure the data has been sent on the new veth
net device.

Reviewed-by: Mat Martineau <[email protected]>
Signed-off-by: Geliang Tang <[email protected]>

tools/testing/selftests/bpf/prog_tests/mptcp.c

@@ -8,6 +8,7 @@
 #include "mptcp_sock.skel.h"
 #include "mptcp_bpf_first.skel.h"
 #include "mptcp_bpf_bkup.skel.h"
+#include "mptcp_bpf_rr.skel.h"
 
 #ifndef TCP_CA_NAME_MAX
 #define TCP_CA_NAME_MAX	16
@@ -329,6 +330,38 @@ static void test_bkup(void)
 	mptcp_bpf_bkup__destroy(bkup_skel);
 }
 
+static void test_rr(void)
+{
+	struct mptcp_bpf_rr *rr_skel;
+	int server_fd, client_fd;
+	struct bpf_link *link;
+
+	rr_skel = mptcp_bpf_rr__open_and_load();
+	if (!ASSERT_OK_PTR(rr_skel, "bpf_rr__open_and_load"))
+		return;
+
+	link = bpf_map__attach_struct_ops(rr_skel->maps.rr);
+	if (!ASSERT_OK_PTR(link, "bpf_map__attach_struct_ops")) {
+		mptcp_bpf_rr__destroy(rr_skel);
+		return;
+	}
+
+	add_veth();
+	system("ip mptcp endpoint add 10.0.1.1 subflow");
+	system("sysctl -qw net.mptcp.scheduler=bpf_rr");
+	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_OK(system("ss -MOenita | grep '10.0.1.1' | grep -q 'bytes_sent:'"), "ss");
+
+	close(client_fd);
+	close(server_fd);
+	cleanup();
+	bpf_link__destroy(link);
+	mptcp_bpf_rr__destroy(rr_skel);
+}
+
 void test_mptcp(void)
 {
 	if (test__start_subtest("base"))
@@ -337,4 +370,6 @@ void test_mptcp(void)
 		test_first();
 	if (test__start_subtest("bkup"))
 		test_bkup();
+	if (test__start_subtest("rr"))
+		test_rr();
 }