batman-adv: add isolation_mark sysfs attribute

This attribute can be used to set and read the value and the
mask of the skb mark which will be used to classify the
source non-mesh client as ISOLATED. In this way a client can
be advertised as such and the mark can potentially be
restored at the receiving node before delivering the skb.

This can be helpful for creating network wide netfilter
policies.

This sysfs file expects a string of the shape "$mark/$mask".
Where $mark has to be a 32-bit number in any base, while
$mask must be a 32bit mask expressed in hex base. Only bits
in $mark covered by the bitmask are really stored.

Signed-off-by: Antonio Quartulli <antonio@open-mesh.com>
Signed-off-by: Marek Lindner <mareklindner@neomailbox.ch>

Documentation/ABI/testing/sysfs-class-net-mesh

@@ -68,6 +68,14 @@ Description:
                 Defines the penalty which will be applied to an
                 originator message's tq-field on every hop.
 
+What:		/sys/class/net/<mesh_iface>/mesh/isolation_mark
+Date:		Nov 2013
+Contact:	Antonio Quartulli <antonio@meshcoding.com>
+Description:
+		Defines the isolation mark (and its bitmask) which
+		is used to classify clients as "isolated" by the
+		Extended Isolation feature.
+
 What:           /sys/class/net/<mesh_iface>/mesh/network_coding
 Date:           Nov 2012
 Contact:        Martin Hundeboll <martin@hundeboll.net>