From 33392e1beedca210c4d20be1c30a6ab80c2a05f0 Mon Sep 17 00:00:00 2001

From: Jiri Wiesner <jwiesner@suse.com>

Date: Fri, 21 Aug 2020 10:42:13 +0200

Subject: bonding: fix active-backup failover for current ARP slave

Git-commit: 0410d07190961ac526f05085765a8d04d926545b

Patch-mainline: v5.9-rc2

References: bsc#1174771

When the ARP monitor is used for link detection, ARP replies are

validated for all slaves (arp_validate=3) and fail_over_mac is set to

active, two slaves of an active-backup bond may get stuck in a state

where both of them are active and pass packets that they receive to

the bond. This state makes IPv6 duplicate address detection fail. The

state is reached thus:

1. The current active slave goes down because the ARP target

   is not reachable.

2. The current ARP slave is chosen and made active.

3. A new slave is enslaved. This new slave becomes the current active

   slave and can reach the ARP target.

As a result, the current ARP slave stays active after the enslave

action has finished and the log is littered with "PROBE BAD" messages:

> bond0: PROBE: c_arp ens10 && cas ens11 BAD

The workaround is to remove the slave with "going back" status from

the bond and re-enslave it. This issue was encountered when DPDK PMD

interfaces were being enslaved to an active-backup bond.

I would be possible to fix the issue in bond_enslave() or

bond_change_active_slave() but the ARP monitor was fixed instead to

keep most of the actions changing the current ARP slave in the ARP

monitor code. The current ARP slave is set as inactive and backup

during the commit phase. A new state, BOND_LINK_FAIL, has been

introduced for slaves in the context of the ARP monitor. This allows

administrators to see how slaves are rotated for sending ARP requests

and attempts are made to find a new active slave.

Fixes: b2220cad583c9 ("bonding: refactor ARP active-backup monitor")

Signed-off-by: Jiri Wiesner <jwiesner@suse.com>

Signed-off-by: David S. Miller <davem@davemloft.net>

---

 drivers/net/bonding/bond_main.c | 18 ++++++++++++++++--

 1 file changed, 16 insertions(+), 2 deletions(-)

diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c

index d10805e5e623..061254a592c0 100644

--- a/drivers/net/bonding/bond_main.c

+++ b/drivers/net/bonding/bond_main.c

@@ -2824,6 +2824,9 @@ static int bond_ab_arp_inspect(struct bonding *bond)

 			if (bond_time_in_interval(bond, last_rx, 1)) {

 				bond_propose_link_state(slave, BOND_LINK_UP);

 				commit++;

+			} else if (slave->link == BOND_LINK_BACK) {

+				bond_propose_link_state(slave, BOND_LINK_FAIL);

+				commit++;

 			}

 			continue;

 		}

@@ -2932,6 +2935,19 @@ static void bond_ab_arp_commit(struct bonding *bond)

 			continue;

+		case BOND_LINK_FAIL:

+			bond_set_slave_link_state(slave, BOND_LINK_FAIL,

+						  BOND_SLAVE_NOTIFY_NOW);

+			bond_set_slave_inactive_flags(slave,

+						      BOND_SLAVE_NOTIFY_NOW);

+

+			/* A slave has just been enslaved and has become

+			 * the current active slave.

+			 */

+			if (rtnl_dereference(bond->curr_active_slave))

+				RCU_INIT_POINTER(bond->current_arp_slave, NULL);

+			continue;

+

 		default:

 			slave_err(bond->dev, slave->dev,

 				  "impossible: link_new_state %d on slave\n",

@@ -2982,8 +2998,6 @@ static bool bond_ab_arp_probe(struct bonding *bond)

 			return should_notify_rtnl;

 	}

-	bond_set_slave_inactive_flags(curr_arp_slave, BOND_SLAVE_NOTIFY_LATER);

-

 	bond_for_each_slave_rcu(bond, slave, iter) {

 		if (!found && !before && bond_slave_is_up(slave))

 			before = slave;

-- 

2.26.2