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 <tanggeliang@kylinos.cn>

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"))