selftests/bpf: Add mptcp_subflow bpf_iter subtest

This patch adds a subtest named test_bpf_iter to load and verify the newly
added mptcp_subflow type bpf_iter example in test_mptcp. Use endpoint_init()
to add a new subflow endpoint. A new helper recv_send() is invoked to trigger
the ftrace hook for mptcp_sched_get_send() after wait_for_new_subflows().
Check if skel->bss->iter equals 2 to verify whether the ftrace program loops
twice as expected.

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

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

@@ -10,6 +10,7 @@
 #include "mptcp_sock.skel.h"
 #include "mptcpify.skel.h"
 #include "mptcp_subflow.skel.h"
+#include "mptcp_bpf_iter.skel.h"
 #include "mptcp_bpf_first.skel.h"
 #include "mptcp_bpf_bkup.skel.h"
 #include "mptcp_bpf_rr.skel.h"
@@ -258,6 +259,34 @@ static void send_byte(int fd)
 	ASSERT_EQ(write(fd, &b, sizeof(b)), 1, "send single byte");
 }
 
+static int recv_send(int server_fd)
+{
+	char buf[1];
+	int ret, fd;
+	ssize_t n;
+
+	fd = accept(server_fd, NULL, NULL);
+	if (!ASSERT_OK_FD(fd, "accept"))
+		return -1;
+
+	n = recv(fd, buf, sizeof(buf), 0);
+	if (!ASSERT_GT(n, 0, "recv")) {
+		ret = -1;
+		goto close;
+	}
+
+	n = send(fd, buf, n, 0);
+	if (!ASSERT_GT(n, 0, "send")) {
+		ret = -1;
+		goto close;
+	}
+
+	ret = 0;
+close:
+	close(fd);
+	return ret;
+}
+
 static int verify_mptcpify(int server_fd, int client_fd)
 {
 	struct __mptcp_info info;
@@ -470,6 +499,60 @@ static void test_subflow(void)
 	close(cgroup_fd);
 }
 
+static void run_bpf_iter(void)
+{
+	int server_fd, client_fd;
+
+	server_fd = start_mptcp_server(AF_INET, ADDR_1, PORT_1, 0);
+	if (!ASSERT_OK_FD(server_fd, "start_mptcp_server"))
+		return;
+
+	client_fd = connect_to_fd(server_fd, 0);
+	if (!ASSERT_OK_FD(client_fd, "connect_to_fd"))
+		goto close_server;
+
+	send_byte(client_fd);
+	wait_for_new_subflows(client_fd);
+	recv_send(server_fd);
+
+	close(client_fd);
+close_server:
+	close(server_fd);
+}
+
+static void test_bpf_iter(void)
+{
+	struct mptcp_bpf_iter *skel;
+	struct nstoken *nstoken;
+	int err;
+
+	skel = mptcp_bpf_iter__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "skel_open_load: mptcp_iter"))
+		return;
+
+	skel->bss->pid = getpid();
+
+	err = mptcp_bpf_iter__attach(skel);
+	if (!ASSERT_OK(err, "skel_attach: mptcp_iter"))
+		goto skel_destroy;
+
+	nstoken = create_netns();
+	if (!ASSERT_OK_PTR(nstoken, "create_netns: mptcp_iter"))
+		goto skel_destroy;
+
+	if (endpoint_init("subflow") < 0)
+		goto close_netns;
+
+	run_bpf_iter();
+
+	ASSERT_EQ(skel->bss->iter, 2, "iter");
+
+close_netns:
+	cleanup_netns(nstoken);
+skel_destroy:
+	mptcp_bpf_iter__destroy(skel);
+}
+
 static struct nstoken *sched_init(char *flags, char *sched)
 {
 	struct nstoken *nstoken;
@@ -651,6 +734,8 @@ void test_mptcp(void)
 		test_mptcpify();
 	if (test__start_subtest("subflow"))
 		test_subflow();
+	if (test__start_subtest("bpf_iter"))
+		test_bpf_iter();
 	if (test__start_subtest("default"))
 		test_default();
 	if (test__start_subtest("first"))