[PATCH net-next] net: add check for current MAC address in dev_set_mac_address

[Piotr Gardocki <piotrx.gardocki@intel.com>]

In some cases it is possible for kernel to come with request
to change primary MAC address to the address that is already
set on the given interface.

This patch adds proper check to return fast from the function
in these cases.

An example of such case is adding an interface to bonding
channel in balance-alb mode:
modprobe bonding mode=balance-alb miimon=100 max_bonds=1
ip link set bond0 up
ifenslave bond0 <eth>

Signed-off-by: Piotr Gardocki <piotrx.gardocki@intel.com>
---
 net/core/dev.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/core/dev.c b/net/core/dev.c
index 99d99b247bc9..c2c3ec61397b 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -8820,6 +8820,8 @@ int dev_set_mac_address(struct net_device *dev, struct sockaddr *sa,
 		return -EINVAL;
 	if (!netif_device_present(dev))
 		return -ENODEV;
+	if (ether_addr_equal(dev->dev_addr, sa->sa_data))
+		return 0;
 	err = dev_pre_changeaddr_notify(dev, sa->sa_data, extack);
 	if (err)
 		return err;
-- 
2.34.1