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[PATCH 5.1 14/46] bonding: fix arp_validate toggling in active-backup mode

From: Jarod Wilson <jarod@xxxxxxxxxx>

[ Upstream commit a9b8a2b39ce65df45687cf9ef648885c2a99fe75 ]

There's currently a problem with toggling arp_validate on and off with an
active-backup bond. At the moment, you can start up a bond, like so:

modprobe bonding mode=1 arp_interval=100 arp_validate=0 arp_ip_targets=
ip link set bond0 down
echo "ens4f0" > /sys/class/net/bond0/bonding/slaves
echo "ens4f1" > /sys/class/net/bond0/bonding/slaves
ip link set bond0 up
ip addr add dev bond0

Pings to work just fine. Now turn on arp_validate:

echo 1 > /sys/class/net/bond0/bonding/arp_validate

Pings to continue to work just fine. Now when you go to turn
arp_validate off again, the link falls flat on it's face:

echo 0 > /sys/class/net/bond0/bonding/arp_validate
[133191.911987] bond0: Setting arp_validate to none (0)
[133194.257793] bond0: bond_should_notify_peers: slave ens4f0
[133194.258031] bond0: link status definitely down for interface ens4f0, disabling it
[133194.259000] bond0: making interface ens4f1 the new active one
[133197.330130] bond0: link status definitely down for interface ens4f1, disabling it
[133197.331191] bond0: now running without any active interface!

The problem lies in bond_options.c, where passing in arp_validate=0
results in bond->recv_probe getting set to NULL. This flies directly in
the face of commit 3fe68df97c7f, which says we need to set recv_probe =
bond_arp_recv, even if we're not using arp_validate. Said commit fixed
this in bond_option_arp_interval_set, but missed that we can get to that
same state in bond_option_arp_validate_set as well.

One solution would be to universally set recv_probe = bond_arp_recv here
as well, but I don't think bond_option_arp_validate_set has any business
touching recv_probe at all, and that should be left to the arp_interval
code, so we can just make things much tidier here.

Fixes: 3fe68df97c7f ("bonding: always set recv_probe to bond_arp_rcv in arp monitor")
CC: Jay Vosburgh <j.vosburgh@xxxxxxxxx>
CC: Veaceslav Falico <vfalico@xxxxxxxxx>
CC: Andy Gospodarek <andy@xxxxxxxxxxxxx>
CC: "David S. Miller" <davem@xxxxxxxxxxxxx>
CC: netdev@xxxxxxxxxxxxxxx
Signed-off-by: Jarod Wilson <jarod@xxxxxxxxxx>
Signed-off-by: Jay Vosburgh <jay.vosburgh@xxxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
 drivers/net/bonding/bond_options.c |    7 -------
 1 file changed, 7 deletions(-)

--- a/drivers/net/bonding/bond_options.c
+++ b/drivers/net/bonding/bond_options.c
@@ -1098,13 +1098,6 @@ static int bond_option_arp_validate_set(
 	netdev_dbg(bond->dev, "Setting arp_validate to %s (%llu)\n",
 		   newval->string, newval->value);
-	if (bond->dev->flags & IFF_UP) {
-		if (!newval->value)
-			bond->recv_probe = NULL;
-		else if (bond->params.arp_interval)
-			bond->recv_probe = bond_arp_rcv;
-	}
 	bond->params.arp_validate = newval->value;
 	return 0;