bonding: restore IFF_MASTER/SLAVE flags on bond enslave ether type change

[ Upstream commit 3b37236c1fa939cca675f45026624526027000b0 ]

Add bond_ether_setup helper which is used to fix ether_setup() calls in the
bonding driver. It takes care of both IFF_MASTER and IFF_SLAVE flags, the
former is always restored and the latter only if it was set.
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: 3e239f541fa4 ("bonding: clean muticast addresses when device changes type")
Signed-off-by: Nikolay Aleksandrov <razor@blackwall.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index fce9301c8ebbc89e4e50383131f23d67e23a0fa5..091c430547e7c95c1501502c24e0bc4c1c8635b7 100644 (file)
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -1774,6 +1774,19 @@ void bond_lower_state_changed(struct slave *slave)
                slave_err(bond_dev, slave_dev, "Error: %s\n", errmsg);  \
 } while (0)
 
+/* The bonding driver uses ether_setup() to convert a master bond device
+ * to ARPHRD_ETHER, that resets the target netdevice's flags so we always
+ * have to restore the IFF_MASTER flag, and only restore IFF_SLAVE if it was set
+ */
+static void bond_ether_setup(struct net_device *bond_dev)
+{
+       unsigned int slave_flag = bond_dev->flags & IFF_SLAVE;
+
+       ether_setup(bond_dev);
+       bond_dev->flags |= IFF_MASTER | slave_flag;
+       bond_dev->priv_flags &= ~IFF_TX_SKB_SHARING;
+}
+
 /* enslave device <slave> to bond device <master> */
 int bond_enslave(struct net_device *bond_dev, struct net_device *slave_dev,
                 struct netlink_ext_ack *extack)
@@ -1865,10 +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);