selftests: mptcp: add userspace pm subflow flag

This patch adds the address flag MPTCP_PM_ADDR_FLAG_SUBFLOW in csf() in
pm_nl_ctl.c when subflow is created by a userspace PM.
Signed-off-by: Geliang Tang <tanggeliang@kylinos.cn>
Reviewed-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

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

@@ -453,6 +453,7 @@ int csf(int fd, int pm_family, int argc, char *argv[])
 	char data[NLMSG_ALIGN(sizeof(struct nlmsghdr)) +
 		  NLMSG_ALIGN(sizeof(struct genlmsghdr)) +
 		  1024];
+	u_int32_t flags = MPTCP_PM_ADDR_FLAG_SUBFLOW;
 	const char *params[5];
 	struct nlmsghdr *nh;
 	struct rtattr *addr;
@@ -558,6 +559,13 @@ int csf(int fd, int pm_family, int argc, char *argv[])
 			off += NLMSG_ALIGN(rta->rta_len);
 		}
 
+		/* addr flags */
+		rta = (void *)(data + off);
+		rta->rta_type = MPTCP_PM_ADDR_ATTR_FLAGS;
+		rta->rta_len = RTA_LENGTH(4);
+		memcpy(RTA_DATA(rta), &flags, 4);
+		off += NLMSG_ALIGN(rta->rta_len);
+
 		addr->rta_len = off - addr_start;
 	}