[PATCH RFC] net-sysfs: consistent behavior between ioctl and sysfs

[Julius Niedworok <julius.n@gmx.net>]

The flags of a network interface can be read either from
/sys/class/net/<dev>/flags or from the ioctl SIOCGIFFLAGS. When the ioctl
is used, dev_get_flags is called to extract the flags. However, reads on
the sysfs file return the plain content of the flags integer and do not
call dev_get_flags.

In order to fix this inconsistent behavior, replace the NETDEVICE_SHOW_RW
macro by the functions format_flags and flags_show. These functions extract
the flags by calling dev_get_flags and return them formatted for the user.

This makes the behavior between calling the SIOCGIFFLAGS ioctl and reading
/sys/class/net/<dev>/flags consistent.

Co-developed-by: Charlie Groh <ga58taw@mytum.de>
Signed-off-by: Charlie Groh <ga58taw@mytum.de>
Signed-off-by: Julius Niedworok <julius.n@gmx.net>
---
 net/core/net-sysfs.c | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
index ff9fd2b..8ae8be5 100644
--- a/net/core/net-sysfs.c
+++ b/net/core/net-sysfs.c
@@ -345,7 +345,19 @@ static ssize_t flags_store(struct device *dev, struct device_attribute *attr,
 {
 	return netdev_store(dev, attr, buf, len, change_flags);
 }
-NETDEVICE_SHOW_RW(flags, fmt_hex);
+
+static ssize_t format_flags(const struct net_device *dev, char *buf)
+{
+	return sprintf(buf, fmt_hex, dev_get_flags(dev));
+}
+
+static ssize_t flags_show(struct device *dev,
+			  struct device_attribute *attr,
+			  char *buf)
+{
+	return netdev_show(dev, attr, buf, format_flags);
+}
+static DEVICE_ATTR_RW(flags);
 
 static ssize_t tx_queue_len_store(struct device *dev,
 				  struct device_attribute *attr,
-- 
2.10.1 (Apple Git-78)