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, 18 insertions, 0 deletions

diff --git a/net/batman-adv/multicast.h b/net/batman-adv/multicast.h
index 34fb922a4566..653b9b76fabe 100644
--- a/net/batman-adv/multicast.h
+++ b/net/batman-adv/multicast.h
@@ -24,6 +24,13 @@ enum batadv_forw_mode {
 	BATADV_FORW_ALL,
 
 	/**
+	 * @BATADV_FORW_SOME: forward the packet to some nodes (currently via
+	 *  a multicast-to-unicast conversion and the BATMAN unicast routing
+	 *  protocol)
+	 */
+	BATADV_FORW_SOME,
+
+	/**
 	 * @BATADV_FORW_SINGLE: forward the packet to a single node (currently
 	 *  via the BATMAN unicast routing protocol)
 	 */
@@ -39,6 +46,9 @@ enum batadv_forw_mode
 batadv_mcast_forw_mode(struct batadv_priv *bat_priv, struct sk_buff *skb,
 		       struct batadv_orig_node **mcast_single_orig);
 
+int batadv_mcast_forw_send(struct batadv_priv *bat_priv, struct sk_buff *skb,
+			   unsigned short vid);
+
 void batadv_mcast_init(struct batadv_priv *bat_priv);
 
 int batadv_mcast_flags_seq_print_text(struct seq_file *seq, void *offset);
@@ -61,6 +71,14 @@ batadv_mcast_forw_mode(struct batadv_priv *bat_priv, struct sk_buff *skb,
 	return BATADV_FORW_ALL;
 }
 
+static inline int
+batadv_mcast_forw_send(struct batadv_priv *bat_priv, struct sk_buff *skb,
+		       unsigned short vid)
+{
+	kfree_skb(skb);
+	return NET_XMIT_DROP;
+}
+
 static inline int batadv_mcast_init(struct batadv_priv *bat_priv)
 {
 	return 0;