mptcp: Add a member to mptcp_pm_data to track kernel vs userspace mode

When adding support for netlink path management commands, the kernel
needs to know whether paths are being controlled by the in-kernel path
manager or a userspace PM.
Acked-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

net/mptcp/pm.c

@@ -424,6 +424,10 @@ void mptcp_pm_data_reset(struct mptcp_sock *msk)
 	pm->subflows = 0;
 	pm->rm_list_tx.nr = 0;
 	pm->rm_list_rx.nr = 0;
+	WRITE_ONCE(pm->pm_type, MPTCP_PM_TYPE_KERNEL);
+	/* pm->work_pending must be only be set to 'true' when
+	 * pm->pm_type is set to MPTCP_PM_TYPE_KERNEL
+	 */
 	WRITE_ONCE(pm->work_pending,
 		   (!!mptcp_pm_get_local_addr_max(msk) && subflows_allowed) ||
 		   !!mptcp_pm_get_add_addr_signal_max(msk));

net/mptcp/protocol.h

@@ -184,6 +184,14 @@ enum mptcp_pm_status {
 					 */
 };
 
+enum mptcp_pm_type {
+	MPTCP_PM_TYPE_KERNEL = 0,
+	MPTCP_PM_TYPE_USERSPACE,
+
+	__MPTCP_PM_TYPE_NR,
+	__MPTCP_PM_TYPE_MAX = __MPTCP_PM_TYPE_NR - 1,
+};
+
 /* Status bits below MPTCP_PM_ALREADY_ESTABLISHED need pm worker actions */
 #define MPTCP_PM_WORK_MASK ((1 << MPTCP_PM_ALREADY_ESTABLISHED) - 1)
 
@@ -212,6 +220,7 @@ struct mptcp_pm_data {
 	u8		add_addr_signaled;
 	u8		add_addr_accepted;
 	u8		local_addr_used;
+	u8		pm_type;
 	u8		subflows;
 	u8		status;
 	DECLARE_BITMAP(id_avail_bitmap, MPTCP_PM_MAX_ADDR_ID + 1);