batman-adv: Add multicast-to-unicast support for multiple targets

With this patch multicast packets with a limited number of destinations
(current default: 16) will be split and transmitted by the originator as
individual unicast transmissions.

Wifi broadcasts with their low bitrate are still a costly undertaking.
In a mesh network this cost multiplies with the overall size of the mesh
network. Therefore using multiple unicast transmissions instead of
broadcast flooding is almost always less burdensome for the mesh
network.

The maximum amount of unicast packets can be configured via the newly
introduced multicast_fanout parameter. If this limit is exceeded
distribution will fall back to classic broadcast flooding.

The multicast-to-unicast conversion is performed on the initial
multicast sender node and counts on a final destination node, mesh-wide
basis (and not next hop, neighbor node basis).

Signed-off-by: Linus Lüssing <linus.luessing@c0d3.blue>
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>

1 files changed, 7 insertions, 0 deletions

diff --git a/include/uapi/linux/batman_adv.h b/include/uapi/linux/batman_adv.h
index e53f2b5e7ee7..67f4636758af 100644
--- a/include/uapi/linux/batman_adv.h
+++ b/include/uapi/linux/batman_adv.h
@@ -473,6 +473,13 @@ enum batadv_nl_attrs {
 	 */
 	BATADV_ATTR_THROUGHPUT_OVERRIDE,
 
+	/**
+	 * @BATADV_ATTR_MULTICAST_FANOUT: defines the maximum number of packet
+	 * copies that may be generated for a multicast-to-unicast conversion.
+	 * Once this limit is exceeded distribution will fall back to broadcast.
+	 */
+	BATADV_ATTR_MULTICAST_FANOUT,
+
 	/* add attributes above here, update the policy in netlink.c */
 
 	/**