selftests: add test-cases for MPTCP MP_JOIN

Use the pm netlink to configure the creation of several
subflows, and verify that via MIB counters.

Update the mptcp_connect program to allow reliable MP_JOIN
handshake even on small data file

Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

tools/testing/selftests/net/mptcp/Makefile

@@ -5,7 +5,7 @@ KSFT_KHDR_INSTALL := 1
 
 CFLAGS =  -Wall -Wl,--no-as-needed -O2 -g  -I$(top_srcdir)/usr/include
 
-TEST_PROGS := mptcp_connect.sh pm_netlink.sh
+TEST_PROGS := mptcp_connect.sh pm_netlink.sh mptcp_join.sh
 
 TEST_GEN_FILES = mptcp_connect pm_nl_ctl
 

tools/testing/selftests/net/mptcp/mptcp_connect.c

@@ -51,6 +51,7 @@ static bool tcpulp_audit;
 static int pf = AF_INET;
 static int cfg_sndbuf;
 static int cfg_rcvbuf;
+static bool cfg_join;
 
 static void die_usage(void)
 {
@@ -250,17 +251,27 @@ static int sock_connect_mptcp(const char * const remoteaddr,
 
 static size_t do_rnd_write(const int fd, char *buf, const size_t len)
 {
+	static bool first = true;
 	unsigned int do_w;
 	ssize_t bw;
 
 	do_w = rand() & 0xffff;
 	if (do_w == 0 || do_w > len)
 		do_w = len;
 
+	if (cfg_join && first && do_w > 100)
+		do_w = 100;
+
 	bw = write(fd, buf, do_w);
 	if (bw < 0)
 		perror("write");
 
+	/* let the join handshake complete, before going on */
+	if (cfg_join && first) {
+		usleep(200000);
+		first = false;
+	}
+
 	return bw;
 }
 
@@ -385,8 +396,11 @@ static int copyfd_io_poll(int infd, int peerfd, int outfd)
 					break;
 
 				/* ... but we still receive.
-				 * Close our write side.
+				 * Close our write side, ev. give some time
+				 * for address notification
 				 */
+				if (cfg_join)
+					usleep(400000);
 				shutdown(peerfd, SHUT_WR);
 			} else {
 				if (errno == EINTR)
@@ -403,6 +417,10 @@ static int copyfd_io_poll(int infd, int peerfd, int outfd)
 		}
 	}
 
+	/* leave some time for late join/announce */
+	if (cfg_join)
+		usleep(400000);
+
 	close(peerfd);
 	return 0;
 }
@@ -658,7 +676,7 @@ static void maybe_close(int fd)
 {
 	unsigned int r = rand();
 
-	if (r & 1)
+	if (!cfg_join && (r & 1))
 		close(fd);
 }
 
@@ -794,8 +812,12 @@ static void parse_opts(int argc, char **argv)
 {
 	int c;
 
-	while ((c = getopt(argc, argv, "6lp:s:hut:m:S:R:")) != -1) {
+	while ((c = getopt(argc, argv, "6jlp:s:hut:m:S:R:")) != -1) {
 		switch (c) {
+		case 'j':
+			cfg_join = true;
+			cfg_mode = CFG_MODE_POLL;
+			break;
 		case 'l':
 			listen_mode = true;
 			break;