selftests/bpf: Add mptcpify test

Implement a new test program mptcpify: if the family is AF_INET or
AF_INET6, the type is SOCK_STREAM, and the protocol ID is 0 or
IPPROTO_TCP, set it to IPPROTO_MPTCP. It will be hooked in
update_socket_protocol().

Extend the MPTCP test base, add a selftest test_mptcpify() for the
mptcpify case. Open and load the mptcpify test prog to mptcpify the
TCP sockets dynamically, then use start_server() and connect_to_fd()
to create a TCP socket, but actually what's created is an MPTCP
socket, which can be verified through 'getsockopt(SOL_PROTOCOL)'
and 'nstat' commands.

Acked-by: Yonghong Song <[email protected]>
Reviewed-by: Matthieu Baerts <[email protected]>
Signed-off-by: Geliang Tang <[email protected]>

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

@@ -2,13 +2,19 @@
 /* Copyright (c) 2020, Tessares SA. */
 /* Copyright (c) 2022, SUSE. */
 
+#include <netinet/in.h>
 #include <test_progs.h>
 #include "cgroup_helpers.h"
 #include "network_helpers.h"
 #include "mptcp_sock.skel.h"
+#include "mptcpify.skel.h"
 
 #define NS_TEST "mptcp_ns"
 
+#ifndef IPPROTO_MPTCP
+#define IPPROTO_MPTCP 262
+#endif
+
 #ifndef TCP_CA_NAME_MAX
 #define TCP_CA_NAME_MAX 16
 #endif
@@ -183,8 +189,104 @@ static void test_base(void)
  close(cgroup_fd);
 }
 
+static void send_byte(int fd)
+{
+ char b = 0x55;
+
+ ASSERT_EQ(write(fd, &b, sizeof(b)), 1, "send single byte");
+}
+
+static int verify_mptcpify(int server_fd)
+{
+ socklen_t optlen;
+ char cmd[256];
+ int protocol;
+ int err = 0;
+
+ optlen = sizeof(protocol);
+ if (!ASSERT_OK(getsockopt(server_fd, SOL_SOCKET, SO_PROTOCOL, &protocol, &optlen),
+ "getsockopt(SOL_PROTOCOL)"))
+ return -1;
+
+ if (!ASSERT_EQ(protocol, IPPROTO_MPTCP, "protocol isn't MPTCP"))
+ err++;
+
+ /* Output of nstat:
+ *
+ * #kernel
+ * MPTcpExtMPCapableSYNACKRX 1 0.0
+ */
+ snprintf(cmd, sizeof(cmd),
+ "ip netns exec %s nstat -asz %s | awk '%s' | grep -q '%s'",
+ NS_TEST, "MPTcpExtMPCapableSYNACKRX",
+ "NR==1 {next} {print $2}", "1");
+ if (!ASSERT_OK(system(cmd), "No MPTcpExtMPCapableSYNACKRX found!"))
+ err++;
+
+ return err;
+}
+
+static int run_mptcpify(int cgroup_fd)
+{
+ int server_fd, client_fd, err = 0;
+ struct mptcpify *mptcpify_skel;
+
+ mptcpify_skel = mptcpify__open_and_load();
+ if (!ASSERT_OK_PTR(mptcpify_skel, "skel_open_load"))
+ return libbpf_get_error(mptcpify_skel);
+
+ err = mptcpify__attach(mptcpify_skel);
+ if (!ASSERT_OK(err, "skel_attach"))
+ goto out;
+
+ /* without MPTCP */
+ server_fd = start_server(AF_INET, SOCK_STREAM, NULL, 0, 0);
+ if (!ASSERT_GE(server_fd, 0, "start_server")) {
+ err = -EIO;
+ goto out;
+ }
+
+ client_fd = connect_to_fd(server_fd, 0);
+ if (!ASSERT_GE(client_fd, 0, "connect to fd")) {
+ err = -EIO;
+ goto close_server;
+ }
+
+ send_byte(client_fd);
+ err = verify_mptcpify(server_fd);
+
+ close(client_fd);
+close_server:
+ close(server_fd);
+out:
+ mptcpify__destroy(mptcpify_skel);
+ return err;
+}
+
+static void test_mptcpify(void)
+{
+ struct nstoken *nstoken = NULL;
+ int cgroup_fd;
+
+ cgroup_fd = test__join_cgroup("/mptcpify");
+ if (!ASSERT_GE(cgroup_fd, 0, "test__join_cgroup"))
+ return;
+
+ nstoken = create_netns();
+ if (!ASSERT_OK_PTR(nstoken, "create_netns"))
+ goto fail;
+
+ ASSERT_OK(run_mptcpify(cgroup_fd), "run_mptcpify");
+
+fail:
+ cleanup_netns(nstoken);
+ close(cgroup_fd);
+}
+
 void test_mptcp(void)
 {
  if (test__start_subtest("base"))
  test_base();
+ if (test__start_subtest("mptcpify"))
+ test_mptcpify();
 }

tools/testing/selftests/bpf/progs/mptcpify.c

@@ -0,0 +1,20 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2023, SUSE. */
+
+#include "vmlinux.h"
+#include <bpf/bpf_tracing.h>
+#include "bpf_tracing_net.h"
+
+char _license[] SEC("license") = "GPL";
+
+SEC("fmod_ret/update_socket_protocol")
+int BPF_PROG(mptcpify, int family, int type, int protocol)
+{
+ if ((family == AF_INET || family == AF_INET6) &&
+ type == SOCK_STREAM &&
+ (!protocol || protocol == IPPROTO_TCP)) {
+ return IPPROTO_MPTCP;
+ }
+
+ return protocol;
+}