[PATCH net] bonding: 3ad: don't set BOND_LINK_FAIL on a slave that is not up

[Timur Stukan <timur.stukan.linux@gmail.com>]

In 802.3ad mode, when bond_update_speed_duplex() fails on NETDEV_UP or
NETDEV_CHANGE, bond_slave_netdev_event() sets the slave link to FAIL if
the slave has ever been up (last_link_up != 0), and to DOWN otherwise,
so that miimon can set it right once speed/duplex are valid.

last_link_up is never cleared, so a slave that is currently DOWN but
was up before is set to FAIL as well. miimon then treats it as a slave
that is still in use and takes it through the full down path again:
the link failure count is incremented, "link status definitely down"
is logged and the 802.3ad port is disabled a second time, although the
slave has not been up since it went down.

Reproduced in 802.3ad mode with miimon=100 by setting a slave down and
up again. On NETDEV_UP the speed is still unknown, so the notifier sets
FAIL, and the next miimon pass sees no carrier and proposes DOWN:

	ip link add bond0 type bond mode 802.3ad miimon 100 lacp_rate 1
	ip link set enp0s3 down
	ip link set enp0s4 down
	ip link set enp0s3 master bond0
	ip link set enp0s4 master bond0
	ip link set enp0s3 up
	ip link set enp0s4 up
	ip link set bond0 up
	# wait for LACP to settle
	ip link set enp0s3 down
	ip link set enp0s3 up

procfs then shows "Link Failure Count: 2" in enp0s3 slave part. Also in
dmesg wrote twice: "link status definitely down, disabling slave".

Fix this by setting FAIL only for a slave that is currently UP and
leaving other states alone. An up slave that loses speed/duplex still
goes through FAIL as before, and DOWN/BACK slaves are left to miimon,
as in the other modes.

Fixes: ea53abfab960 ("bonding/802.3ad: fix link_failure_count tracking")
Signed-off-by: Timur Stukan <timur.stukan.linux@gmail.com>
---
 drivers/net/bonding/bond_main.c | 15 +++++----------
 1 file changed, 5 insertions(+), 10 deletions(-)

diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index 7019e5d8fdc8..8212d406f3bc 100644
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -3973,18 +3973,13 @@ static int bond_slave_netdev_event(unsigned long event,
 	case NETDEV_CHANGE:
 		/* For 802.3ad mode only:
 		 * Getting invalid Speed/Duplex values here will put slave
-		 * in weird state. Mark it as link-fail if the link was
-		 * previously up or link-down if it hasn't yet come up, and
-		 * let link-monitoring (miimon) set it right when correct
-		 * speeds/duplex are available.
+		 * in weird state. Mark an up slave as link-fail and let
+		 * miimon set it right when correct speed/duplex are available.
 		 */
 		if (bond_update_speed_duplex(slave) &&
-		    BOND_MODE(bond) == BOND_MODE_8023AD) {
-			if (slave->last_link_up)
-				slave->link = BOND_LINK_FAIL;
-			else
-				slave->link = BOND_LINK_DOWN;
-		}
+		    BOND_MODE(bond) == BOND_MODE_8023AD &&
+		    slave->link == BOND_LINK_UP)
+			slave->link = BOND_LINK_FAIL;
 
 		if (BOND_MODE(bond) == BOND_MODE_8023AD)
 			bond_3ad_adapter_speed_duplex_changed(slave);
-- 
2.43.0