[PATCH net v3 3/5] bonding: 3ad: fix mux port state on oper down

[Louis Scalbert <louis.scalbert@6wind.com>]

When the bonding interface has carrier down due to the absence of
valid slaves and a slave transitions from down to up, the bonding
interface briefly goes carrier up, then down again, and finally up
once LACP negotiates collecting and distributing on the port.

The interface should not transition to carrier up until LACP
negotiation is complete.

This happens because the actor and partner port states remain in
collecting (and distributing) when the port goes down. When the port
comes back up, it temporarily remains in this state until LACP
renegotiation occurs.

Previously this was mostly cosmetic, but since the bonding carrier
state now depends on the LACP negotiation state, it causes the
interface to flap.

Fix this by unsetting the SELECTED flag when a port goes down so that
the mux state machine transitions through ATTACHED and DETACHED,
which clears the actor collecting and distributing flags. Do not
attempt to set the SELECTED flag if the port is still disabled.

Fixes: 655f8919d549 ("bonding: add min links parameter to 802.3ad")
Signed-off-by: Louis Scalbert <louis.scalbert@6wind.com>
---
 drivers/net/bonding/bond_3ad.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/net/bonding/bond_3ad.c b/drivers/net/bonding/bond_3ad.c
index b79a76296966..3a94fbcbf721 100644
--- a/drivers/net/bonding/bond_3ad.c
+++ b/drivers/net/bonding/bond_3ad.c
@@ -1570,6 +1570,12 @@ static void ad_port_selection_logic(struct port *port, bool *update_slave_arr)
 	struct slave *slave;
 	int found = 0;
 
+	/* Disabled ports cannot be SELECTED.
+	 * Do not attempt to set the SELECTED flag if the port is still disabled.
+	 */
+	if (!port->is_enabled)
+		return;
+
 	/* if the port is already Selected, do nothing */
 	if (port->sm_vars & AD_PORT_SELECTED)
 		return;
@@ -2794,6 +2800,7 @@ void bond_3ad_handle_link_change(struct slave *slave, char link)
 		/* link has failed */
 		port->is_enabled = false;
 		ad_update_actor_keys(port, true);
+		port->sm_vars &= ~AD_PORT_SELECTED;
 	}
 	agg = __get_first_agg(port);
 	ad_agg_selection_logic(agg, &dummy);
-- 
2.39.2