Subject: Re: [PATCH] net: bonding: do not set force_primary if reselect is set to failure

From: Jay Vosburgh <[email-masked]>
Date: Thu, 12 Sep 2024 17:06:56 -0700

Suresh Kumar <[email-masked]> wrote:

>when bond_enslave() is called, it sets bond->force_primary to true
>without checking if primary_reselect is set to 'failure' or 'better'.
>This can result in primary becoming active again when link is back which
>is not what we want when primary_reselect is set to 'failure'

	The current behavior is by design, and is documented in
Documentation/networking/bonding.rst:

	The primary_reselect setting is ignored in two cases:

		If no slaves are active, the first slave to recover is
		made the active slave.

		When initially enslaved, the primary slave is always made
		the active slave.

	Your proposed change would cause the primary to never be made
the active interface when added to the bond for the primary_reselect
"better" and "failure" settings, unless the primary interface is added
to the bond first or all other interfaces are down.

	Also, your description above and the test example below use the
phrases "link is back" and "primary link failure" but the patch and test
context suggest that the primary interface is being removed from the
bond and then later added back to the bond, which is not the same thing
as a link failure.

	-J

>Test
>====
>Ethernet Channel Bonding Driver: v3.7.1 (April 27, 2011)
>
>Bonding Mode: fault-tolerance (active-backup)
>Primary Slave: enp1s0 (primary_reselect failure)
>Currently Active Slave: enp1s0
>MII Status: up
>MII Polling Interval (ms): 100
>Up Delay (ms): 0
>Down Delay (ms): 0
>Peer Notification Delay (ms): 0
>
>Slave Interface: enp1s0
>MII Status: up
>Speed: 1000 Mbps
>Duplex: full
>Link Failure Count: 0
>Permanent HW addr: 52:54:00:d7:a7:2a
>Slave queue ID: 0
>
>Slave Interface: enp9s0
>MII Status: up
>Speed: 1000 Mbps
>Duplex: full
>Link Failure Count: 0
>Permanent HW addr: 52:54:00:da:9a:f9
>Slave queue ID: 0
>
>
>After primary link failure:
>
>Bonding Mode: fault-tolerance (active-backup)
>Primary Slave: None
>Currently Active Slave: enp9s0 <---- secondary is active now
>MII Status: up
>MII Polling Interval (ms): 100
>Up Delay (ms): 0
>Down Delay (ms): 0
>Peer Notification Delay (ms): 0
>
>Slave Interface: enp9s0
>MII Status: up
>Speed: 1000 Mbps
>Duplex: full
>Link Failure Count: 0
>Permanent HW addr: 52:54:00:da:9a:f9
>Slave queue ID: 0
>
>
>Now add primary link back and check bond status:
>
>Bonding Mode: fault-tolerance (active-backup)
>Primary Slave: enp1s0 (primary_reselect failure)
>Currently Active Slave: enp1s0  <------------- primary is active again
>MII Status: up
>MII Polling Interval (ms): 100
>Up Delay (ms): 0
>Down Delay (ms): 0
>Peer Notification Delay (ms): 0
>
>Slave Interface: enp9s0
>MII Status: up
>Speed: 1000 Mbps
>Duplex: full
>Link Failure Count: 0
>Permanent HW addr: 52:54:00:da:9a:f9
>Slave queue ID: 0
>
>Slave Interface: enp1s0
>MII Status: up
>Speed: 1000 Mbps
>Duplex: full
>Link Failure Count: 0
>Permanent HW addr: 52:54:00:d7:a7:2a
>Slave queue ID: 0
>
>Signed-off-by: Suresh Kumar <[email-masked]>
>---
> drivers/net/bonding/bond_main.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
>diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
>index bb9c3d6ef435..731256fbb996 100644
>--- a/drivers/net/bonding/bond_main.c
>+++ b/drivers/net/bonding/bond_main.c
>@@ -2146,7 +2146,9 @@ int bond_enslave(struct net_device *bond_dev, struct net_device *slave_dev,
> 		/* if there is a primary slave, remember it */
> 		if (strcmp(bond->params.primary, new_slave->dev->name) == 0) {
> 			rcu_assign_pointer(bond->primary_slave, new_slave);
>-			bond->force_primary = true;
>+            if (bond->params.primary_reselect != BOND_PRI_RESELECT_FAILURE  &&
>+                bond->params.primary_reselect != BOND_PRI_RESELECT_BETTER)
>+			    bond->force_primary = true;
> 		}
> 	}
> 
>-- 
>2.43.0
>

---
	-Jay Vosburgh, [email-masked]