bonding: correctly handle bonding type change on enslave failure

If the bond is enslaving a device with different type it will be setup by it, but if after being setup the enslave fails the bond doesn't switch back its type and also keeps pointers to foreign structures that can be long gone. Thus revert back any type changes if the enslave failed and the bond had to change its type. Example: Before patch: $ echo lo > bond0/bonding/slaves -bash: echo: write error: Cannot assign requested address $ ip l sh bond0 20: bond0: <BROADCAST,MULTICAST,MASTER> mtu 1500 qdisc noop state DOWN mode DEFAULT group default link/loopback 16:54:78:34:bd:41 brd 00:00:00:00:00:00 $ echo +eth1 > bond0/bonding/slaves $ ip l sh bond0 20: bond0: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN mode DEFAULT group default qlen 1000 link/ether 52:54:00:3f:47:69 brd ff:ff:ff:ff:ff:ff (notice the MASTER flag is gone) After patch: $ echo lo > bond0/bonding/slaves -bash: echo: write error: Cannot assign requested address $ ip l sh bond0 21: bond0: <BROADCAST,MULTICAST,MASTER> mtu 1500 qdisc noop state DOWN mode DEFAULT group default qlen 1000 link/ether 6e:66:94:f6:07:fc brd ff:ff:ff:ff:ff:ff $ echo +eth1 > bond0/bonding/slaves $ ip l sh bond0 21: bond0: <BROADCAST,MULTICAST,MASTER> mtu 1500 qdisc noop state DOWN mode DEFAULT group default qlen 1000 link/ether 52:54:00:3f:47:69 brd ff:ff:ff:ff:ff:ff Signed-off-by: Nikolay Aleksandrov <nikolay@cumulusnetworks.com> Fixes: e36b9d1 ("bonding: clean muticast addresses when device changes type") Signed-off-by: David S. Miller <davem@davemloft.net>

Author: Nikolay Aleksandrov

drivers/net/bonding/bond_main.c

@@ -1725,9 +1725,16 @@ int bond_enslave(struct net_device *bond_dev, struct net_device *slave_dev)
 
 err_undo_flags:
 /* Enslave of first slave has failed and we need to fix master's mac */
-if (!bond_has_slaves(bond) &&
- ether_addr_equal_64bits(bond_dev->dev_addr, slave_dev->dev_addr))
-eth_hw_addr_random(bond_dev);
+if (!bond_has_slaves(bond)) {
+if (ether_addr_equal_64bits(bond_dev->dev_addr,
+ slave_dev->dev_addr))
+eth_hw_addr_random(bond_dev);
+if (bond_dev->type != ARPHRD_ETHER) {
+ether_setup(bond_dev);
+bond_dev->flags |= IFF_MASTER;
+bond_dev->priv_flags &= ~IFF_TX_SKB_SHARING;
+}
+}
 
 return res;
 }