sysfs: add attribute to indicate hw address assignment type

Add addr_assign_type to struct net_device and expose it via sysfs.
This new attribute has the purpose of giving user-space the ability to
distinguish between different assignment types of MAC addresses.

For example user-space can treat NICs with randomly generated MAC
addresses differently than NICs that have permanent (locally assigned)
MAC addresses.
For the former udev could write a persistent net rule by matching the
device path instead of the MAC address.
There's also the case of devices that 'steal' MAC addresses from slave
devices. In which it is also be beneficial for user-space to be aware
of the fact.

This patch also introduces a helper function to assist adoption of
drivers that generate MAC addresses randomly.

Signed-off-by: Stefan Assmann <sassmann@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 2 insertions, 0 deletions

diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
index d2b596537d41..af4dfbadf2a0 100644
--- a/net/core/net-sysfs.c
+++ b/net/core/net-sysfs.c
@@ -95,6 +95,7 @@ static ssize_t netdev_store(struct device *dev, struct device_attribute *attr,
 }
 
 NETDEVICE_SHOW(dev_id, fmt_hex);
+NETDEVICE_SHOW(addr_assign_type, fmt_dec);
 NETDEVICE_SHOW(addr_len, fmt_dec);
 NETDEVICE_SHOW(iflink, fmt_dec);
 NETDEVICE_SHOW(ifindex, fmt_dec);
@@ -295,6 +296,7 @@ static ssize_t show_ifalias(struct device *dev,
 }
 
 static struct device_attribute net_class_attributes[] = {
+        __ATTR(addr_assign_type, S_IRUGO, show_addr_assign_type, NULL),
         __ATTR(addr_len, S_IRUGO, show_addr_len, NULL),
         __ATTR(dev_id, S_IRUGO, show_dev_id, NULL),
         __ATTR(ifalias, S_IRUGO | S_IWUSR, show_ifalias, store_ifalias),