net/mlx5: E-Switch, Initialize MAC Address for Default GID

Initialize the source MAC address when creating the default GID entry.
Since this entry is used only for loopback traffic, it only needs to
be a unicast address. A zeroed-out MAC address is sufficient for this
purpose.
Without this fix, random bits would be assigned as the source address.
If these bits formed a multicast address, the firmware would return an
error, preventing the user from switching to switchdev mode:

Error: mlx5_core: Failed setting eswitch to offloads.
kernel answers: Invalid argument

Fixes: 80f09df ("net/mlx5: Eswitch, enable RoCE loopback traffic")
Signed-off-by: Maor Gottlieb <[email protected]>
Signed-off-by: Mark Bloch <[email protected]>
Reviewed-by: Michal Swiatkowski <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

Author: maorgottlieb

drivers/net/ethernet/mellanox/mlx5/core/rdma.c

@@ -118,8 +118,8 @@ static void mlx5_rdma_make_default_gid(struct mlx5_core_dev *dev, union ib_gid *
 
 static int mlx5_rdma_add_roce_addr(struct mlx5_core_dev *dev)
 {
+	u8 mac[ETH_ALEN] = {};
 	union ib_gid gid;
-	u8 mac[ETH_ALEN];
 
 	mlx5_rdma_make_default_gid(dev, &gid);
 	return mlx5_core_roce_gid_set(dev, 0,