mptcp: allow to use port and non-signal in set_flags

It's illegal to use both port and non-signal flags for adding address.
But it's legal to use both of them for setting flags, which always uses
non-signal flags, backup or fullmesh.

This patch moves this non-signal flag with port check from
mptcp_pm_parse_addr() to mptcp_nl_cmd_add_addr(). Do the check only when
adding addresses, not setting flags or deleting addresses.

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>

net/mptcp/pm_netlink.c

@@ -1174,14 +1174,8 @@ skip_family:
 	if (tb[MPTCP_PM_ADDR_ATTR_FLAGS])
 		entry->flags = nla_get_u32(tb[MPTCP_PM_ADDR_ATTR_FLAGS]);
 
-	if (tb[MPTCP_PM_ADDR_ATTR_PORT]) {
-		if (!(entry->flags & MPTCP_PM_ADDR_FLAG_SIGNAL)) {
-			NL_SET_ERR_MSG_ATTR(info->extack, attr,
-					    "flags must have signal when using port");
-			return -EINVAL;
-		}
+	if (tb[MPTCP_PM_ADDR_ATTR_PORT])
 		entry->addr.port = htons(nla_get_u16(tb[MPTCP_PM_ADDR_ATTR_PORT]));
-	}
 
 	return 0;
 }
@@ -1227,6 +1221,11 @@ static int mptcp_nl_cmd_add_addr(struct sk_buff *skb, struct genl_info *info)
 	if (ret < 0)
 		return ret;
 
+	if (addr.addr.port && !(addr.flags & MPTCP_PM_ADDR_FLAG_SIGNAL)) {
+		GENL_SET_ERR_MSG(info, "flags must have signal when using port");
+		return -EINVAL;
+	}
+
 	entry = kmalloc(sizeof(*entry), GFP_KERNEL);
 	if (!entry) {
 		GENL_SET_ERR_MSG(info, "can't allocate addr");