[PATCH] rtnetlink: expose value from SET_NETDEV_DEVTYPE via IFLA_DEVTYPE attribute

[Marcel Holtmann]

The name value from SET_NETDEV_DEVTYPE only ended up in the uevent sysfs
file as DEVTYPE= information. To avoid any kind of race conditions
between netlink messages and reading from sysfs, it is useful to add the
same string as new IFLA_DEVTYPE attribute included in the RTM_NEWLINK
messages.

For network managing daemons that have to classify ARPHRD_ETHER network
devices into different types (like Wireless LAN, Bluetooth etc.), this
avoids the extra round trip to sysfs and parsing of the uevent file.

Signed-off-by: Marcel Holtmann <mar...@holtmann.org>
---
 include/uapi/linux/if_link.h |  2 ++
 net/core/rtnetlink.c         | 12 ++++++++++++
 2 files changed, 14 insertions(+)

diff --git a/include/uapi/linux/if_link.h b/include/uapi/linux/if_link.h
index 43391e2d1153..781294972bb4 100644
--- a/include/uapi/linux/if_link.h
+++ b/include/uapi/linux/if_link.h
@@ -166,6 +166,8 @@ enum {
        IFLA_NEW_IFINDEX,
        IFLA_MIN_MTU,
        IFLA_MAX_MTU,
+       IFLA_DEVTYPE,           /* Name value from SET_NETDEV_DEVTYPE */
+#define IFLA_DEVTYPE IFLA_DEVTYPE
        __IFLA_MAX
 };
 
diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index 24431e578310..bd288710f9bf 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -970,6 +970,14 @@ static size_t rtnl_xdp_size(void)
        return xdp_size;
 }
 
+static size_t rtnl_devtype_size(const struct net_device *dev)
+{
+       if (!dev->dev.type || !dev->dev.type->name)
+               return 0;
+
+       return strlen(dev->dev.type->name) + 1;
+}
+
 static noinline size_t if_nlmsg_size(const struct net_device *dev,
                                     u32 ext_filter_mask)
 {
@@ -1017,6 +1025,7 @@ static noinline size_t if_nlmsg_size(const struct 
net_device *dev,
               + nla_total_size(4)  /* IFLA_CARRIER_DOWN_COUNT */
               + nla_total_size(4)  /* IFLA_MIN_MTU */
               + nla_total_size(4)  /* IFLA_MAX_MTU */
+              + rtnl_devtype_size(dev) /* IFLA_DEVTYPE */
               + 0;
 }
 
@@ -1679,6 +1688,8 @@ static int rtnl_fill_ifinfo(struct sk_buff *skb,
            nla_put_s32(skb, IFLA_NEW_IFINDEX, new_ifindex) < 0)
                goto nla_put_failure;
 
+       if (dev->dev.type && dev->dev.type->name)
+               nla_put_string(skb, IFLA_DEVTYPE, dev->dev.type->name);
 
        rcu_read_lock();
        if (rtnl_fill_link_af(skb, dev, ext_filter_mask))
@@ -1738,6 +1749,7 @@ static const struct nla_policy ifla_policy[IFLA_MAX+1] = {
        [IFLA_CARRIER_DOWN_COUNT] = { .type = NLA_U32 },
        [IFLA_MIN_MTU]          = { .type = NLA_U32 },
        [IFLA_MAX_MTU]          = { .type = NLA_U32 },
+       [IFLA_DEVTYPE]          = { .type = NLA_STRING },
 };
 
 static const struct nla_policy ifla_info_policy[IFLA_INFO_MAX+1] = {
-- 
2.14.4