selftests: mptcp: add the port argument for set_flags

This patch added the port argument for setting the address flags in
pm_nl_ctl.

Usage:

    pm_nl_ctl set 10.0.2.1 flags backup port 10100
Signed-off-by: Geliang Tang <geliang.tang@suse.com>
Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

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

@@ -28,7 +28,7 @@ static void syntax(char *argv[])
 	fprintf(stderr, "\tadd [flags signal|subflow|backup|fullmesh] [id <nr>] [dev <name>] <ip>\n");
 	fprintf(stderr, "\tdel <id> [<ip>]\n");
 	fprintf(stderr, "\tget <id>\n");
-	fprintf(stderr, "\tset <ip> [flags backup|nobackup|fullmesh|nofullmesh]\n");
+	fprintf(stderr, "\tset <ip> [flags backup|nobackup|fullmesh|nofullmesh] [port <nr>]\n");
 	fprintf(stderr, "\tflush\n");
 	fprintf(stderr, "\tdump\n");
 	fprintf(stderr, "\tlimits [<rcv addr max> <subflow max>]\n");
@@ -721,6 +721,18 @@ int set_flags(int fd, int pm_family, int argc, char *argv[])
 			rta->rta_len = RTA_LENGTH(4);
 			memcpy(RTA_DATA(rta), &flags, 4);
 			off += NLMSG_ALIGN(rta->rta_len);
+		} else if (!strcmp(argv[arg], "port")) {
+			u_int16_t port;
+
+			if (++arg >= argc)
+				error(1, 0, " missing port value");
+
+			port = atoi(argv[arg]);
+			rta = (void *)(data + off);
+			rta->rta_type = MPTCP_PM_ADDR_ATTR_PORT;
+			rta->rta_len = RTA_LENGTH(2);
+			memcpy(RTA_DATA(rta), &port, 2);
+			off += NLMSG_ALIGN(rta->rta_len);
 		} else {
 			error(1, 0, "unknown keyword %s", argv[arg]);
 		}