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, 198 insertions, 1 deletions

diff --git a/net/batman-adv/multicast.c b/net/batman-adv/multicast.c
index 4d6e89e04aa0..3feb9435b715 100644
--- a/net/batman-adv/multicast.c
+++ b/net/batman-adv/multicast.c
@@ -54,6 +54,7 @@
 #include "hash.h"
 #include "log.h"
 #include "netlink.h"
+#include "send.h"
 #include "soft-interface.h"
 #include "translation-table.h"
 #include "tvlv.h"
@@ -979,6 +980,7 @@ batadv_mcast_forw_mode(struct batadv_priv *bat_priv, struct sk_buff *skb,
 {
 	int ret, tt_count, ip_count, unsnoop_count, total_count;
 	bool is_unsnoopable = false;
+	unsigned int mcast_fanout;
 	struct ethhdr *ethhdr;
 
 	ret = batadv_mcast_forw_mode_check(bat_priv, skb, &is_unsnoopable);
@@ -1013,8 +1015,203 @@ batadv_mcast_forw_mode(struct batadv_priv *bat_priv, struct sk_buff *skb,
 	case 0:
 		return BATADV_FORW_NONE;
 	default:
-		return BATADV_FORW_ALL;
+		mcast_fanout = atomic_read(&bat_priv->multicast_fanout);
+
+		if (!unsnoop_count && total_count <= mcast_fanout)
+			return BATADV_FORW_SOME;
+	}
+
+	return BATADV_FORW_ALL;
+}
+
+/**
+ * batadv_mcast_forw_tt() - forwards a packet to multicast listeners
+ * @bat_priv: the bat priv with all the soft interface information
+ * @skb: the multicast packet to transmit
+ * @vid: the vlan identifier
+ *
+ * Sends copies of a frame with multicast destination to any multicast
+ * listener registered in the translation table. A transmission is performed
+ * via a batman-adv unicast packet for each such destination node.
+ *
+ * Return: NET_XMIT_DROP on memory allocation failure, NET_XMIT_SUCCESS
+ * otherwise.
+ */
+static int
+batadv_mcast_forw_tt(struct batadv_priv *bat_priv, struct sk_buff *skb,
+		     unsigned short vid)
+{
+	int ret = NET_XMIT_SUCCESS;
+	struct sk_buff *newskb;
+
+	struct batadv_tt_orig_list_entry *orig_entry;
+
+	struct batadv_tt_global_entry *tt_global;
+	const u8 *addr = eth_hdr(skb)->h_dest;
+
+	tt_global = batadv_tt_global_hash_find(bat_priv, addr, vid);
+	if (!tt_global)
+		goto out;
+
+	rcu_read_lock();
+	hlist_for_each_entry_rcu(orig_entry, &tt_global->orig_list, list) {
+		newskb = skb_copy(skb, GFP_ATOMIC);
+		if (!newskb) {
+			ret = NET_XMIT_DROP;
+			break;
+		}
+
+		batadv_send_skb_unicast(bat_priv, newskb, BATADV_UNICAST, 0,
+					orig_entry->orig_node, vid);
+	}
+	rcu_read_unlock();
+
+	batadv_tt_global_entry_put(tt_global);
+
+out:
+	return ret;
+}
+
+/**
+ * batadv_mcast_forw_want_all_ipv4() - forward to nodes with want-all-ipv4
+ * @bat_priv: the bat priv with all the soft interface information
+ * @skb: the multicast packet to transmit
+ * @vid: the vlan identifier
+ *
+ * Sends copies of a frame with multicast destination to any node with a
+ * BATADV_MCAST_WANT_ALL_IPV4 flag set. A transmission is performed via a
+ * batman-adv unicast packet for each such destination node.
+ *
+ * Return: NET_XMIT_DROP on memory allocation failure, NET_XMIT_SUCCESS
+ * otherwise.
+ */
+static int
+batadv_mcast_forw_want_all_ipv4(struct batadv_priv *bat_priv,
+				struct sk_buff *skb, unsigned short vid)
+{
+	struct batadv_orig_node *orig_node;
+	int ret = NET_XMIT_SUCCESS;
+	struct sk_buff *newskb;
+
+	rcu_read_lock();
+	hlist_for_each_entry_rcu(orig_node,
+				 &bat_priv->mcast.want_all_ipv4_list,
+				 mcast_want_all_ipv4_node) {
+		newskb = skb_copy(skb, GFP_ATOMIC);
+		if (!newskb) {
+			ret = NET_XMIT_DROP;
+			break;
+		}
+
+		batadv_send_skb_unicast(bat_priv, newskb, BATADV_UNICAST, 0,
+					orig_node, vid);
+	}
+	rcu_read_unlock();
+	return ret;
+}
+
+/**
+ * batadv_mcast_forw_want_all_ipv6() - forward to nodes with want-all-ipv6
+ * @bat_priv: the bat priv with all the soft interface information
+ * @skb: The multicast packet to transmit
+ * @vid: the vlan identifier
+ *
+ * Sends copies of a frame with multicast destination to any node with a
+ * BATADV_MCAST_WANT_ALL_IPV6 flag set. A transmission is performed via a
+ * batman-adv unicast packet for each such destination node.
+ *
+ * Return: NET_XMIT_DROP on memory allocation failure, NET_XMIT_SUCCESS
+ * otherwise.
+ */
+static int
+batadv_mcast_forw_want_all_ipv6(struct batadv_priv *bat_priv,
+				struct sk_buff *skb, unsigned short vid)
+{
+	struct batadv_orig_node *orig_node;
+	int ret = NET_XMIT_SUCCESS;
+	struct sk_buff *newskb;
+
+	rcu_read_lock();
+	hlist_for_each_entry_rcu(orig_node,
+				 &bat_priv->mcast.want_all_ipv6_list,
+				 mcast_want_all_ipv6_node) {
+		newskb = skb_copy(skb, GFP_ATOMIC);
+		if (!newskb) {
+			ret = NET_XMIT_DROP;
+			break;
+		}
+
+		batadv_send_skb_unicast(bat_priv, newskb, BATADV_UNICAST, 0,
+					orig_node, vid);
 	}
+	rcu_read_unlock();
+	return ret;
+}
+
+/**
+ * batadv_mcast_forw_want_all() - forward packet to nodes in a want-all list
+ * @bat_priv: the bat priv with all the soft interface information
+ * @skb: the multicast packet to transmit
+ * @vid: the vlan identifier
+ *
+ * Sends copies of a frame with multicast destination to any node with a
+ * BATADV_MCAST_WANT_ALL_IPV4 or BATADV_MCAST_WANT_ALL_IPV6 flag set. A
+ * transmission is performed via a batman-adv unicast packet for each such
+ * destination node.
+ *
+ * Return: NET_XMIT_DROP on memory allocation failure or if the protocol family
+ * is neither IPv4 nor IPv6. NET_XMIT_SUCCESS otherwise.
+ */
+static int
+batadv_mcast_forw_want_all(struct batadv_priv *bat_priv,
+			   struct sk_buff *skb, unsigned short vid)
+{
+	switch (ntohs(eth_hdr(skb)->h_proto)) {
+	case ETH_P_IP:
+		return batadv_mcast_forw_want_all_ipv4(bat_priv, skb, vid);
+	case ETH_P_IPV6:
+		return batadv_mcast_forw_want_all_ipv6(bat_priv, skb, vid);
+	default:
+		/* we shouldn't be here... */
+		return NET_XMIT_DROP;
+	}
+}
+
+/**
+ * batadv_mcast_forw_send() - send packet to any detected multicast recpient
+ * @bat_priv: the bat priv with all the soft interface information
+ * @skb: the multicast packet to transmit
+ * @vid: the vlan identifier
+ *
+ * Sends copies of a frame with multicast destination to any node that signaled
+ * interest in it, that is either via the translation table or the according
+ * want-all flags. A transmission is performed via a batman-adv unicast packet
+ * for each such destination node.
+ *
+ * The given skb is consumed/freed.
+ *
+ * Return: NET_XMIT_DROP on memory allocation failure or if the protocol family
+ * is neither IPv4 nor IPv6. NET_XMIT_SUCCESS otherwise.
+ */
+int batadv_mcast_forw_send(struct batadv_priv *bat_priv, struct sk_buff *skb,
+			   unsigned short vid)
+{
+	int ret;
+
+	ret = batadv_mcast_forw_tt(bat_priv, skb, vid);
+	if (ret != NET_XMIT_SUCCESS) {
+		kfree_skb(skb);
+		return ret;
+	}
+
+	ret = batadv_mcast_forw_want_all(bat_priv, skb, vid);
+	if (ret != NET_XMIT_SUCCESS) {
+		kfree_skb(skb);
+		return ret;
+	}
+
+	consume_skb(skb);
+	return ret;
 }
 
 /**