netdev - [PATCH net v2 2/4] bonding: restore IFF_MASTER/SLAVE flags on bond enslave ether type change

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Date:   Tue, 14 Mar 2023 13:14:24 +0200
From:   Nikolay Aleksandrov <razor@...ckwall.org>
To:     netdev@...r.kernel.org
Cc:     monis@...taire.com, syoshida@...hat.com, j.vosburgh@...il.com,
        andy@...yhouse.net, kuba@...nel.org, davem@...emloft.net,
        pabeni@...hat.com, edumazet@...gle.com,
        syzbot+9dfc3f3348729cc82277@...kaller.appspotmail.com,
        Nikolay Aleksandrov <razor@...ckwall.org>
Subject: [PATCH net v2 2/4] bonding: restore IFF_MASTER/SLAVE flags on bond enslave ether type change

If the bond enslaves non-ARPHRD_ETHER device (changes its type), then
releases it and enslaves ARPHRD_ETHER device (changes back) then we
use ether_setup() to restore the bond device type but it also resets its
flags and removes IFF_MASTER and IFF_SLAVE[1]. Use the bond_ether_setup
helper to restore both after such transition.

[1] reproduce (nlmon is non-ARPHRD_ETHER):
 $ ip l add nlmon0 type nlmon
 $ ip l add bond2 type bond mode active-backup
 $ ip l set nlmon0 master bond2
 $ ip l set nlmon0 nomaster
 $ ip l add bond1 type bond
 (we use bond1 as ARPHRD_ETHER device to restore bond2's mode)
 $ ip l set bond1 master bond2
 $ ip l sh dev bond2
 37: bond2: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN mode DEFAULT group default qlen 1000
    link/ether be:d7:c5:40:5b:cc brd ff:ff:ff:ff:ff:ff promiscuity 0 minmtu 68 maxmtu 1500
 (notice bond2's IFF_MASTER is missing)

Fixes: e36b9d16c6a6 ("bonding: clean muticast addresses when device changes type")
Signed-off-by: Nikolay Aleksandrov <razor@...ckwall.org>
---
 drivers/net/bonding/bond_main.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index d41024ad2c18..cd94baccdac5 100644
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -1878,10 +1878,8 @@ int bond_enslave(struct net_device *bond_dev, struct net_device *slave_dev,
 
 			if (slave_dev->type != ARPHRD_ETHER)
 				bond_setup_by_slave(bond_dev, slave_dev);
-			else {
-				ether_setup(bond_dev);
-				bond_dev->priv_flags &= ~IFF_TX_SKB_SHARING;
-			}
+			else
+				bond_ether_setup(bond_dev);
 
 			call_netdevice_notifiers(NETDEV_POST_TYPE_CHANGE,
 						 bond_dev);
-- 
2.39.2