[B.A.T.M.A.N.] [PATCH 18/19] batman-adv: Still flood multicast packets we are not a receiver of

["Linus Lüssing" <linus.luessing@saxnet.de>]

We may only optimize the multicast packet flow, if an mcast_mode has been
activated and if we are a multicast receiver of the same group. Otherwise
flood the multicast packet without optimizations.

This allows us to still flood multicast packets of protocols where it is
not easily possible for a multicast sender to be a multicast receiver of
the same group instead of dropping them (for instance IPv6 NDP).

This commit therefore also makes IPv6 usable again, if the
proact_tracking multicast mode has been activated.

Signed-off-by: Linus Lüssing <linus.luessing@saxnet.de>
---
 soft-interface.c |   28 ++++++++++++++++++++++++++--
 1 files changed, 26 insertions(+), 2 deletions(-)

diff --git a/batman-adv/soft-interface.c b/batman-adv/soft-interface.c
index 2f327c4..2b202ae 100644
--- a/batman-adv/soft-interface.c
+++ b/batman-adv/soft-interface.c
@@ -340,6 +340,31 @@ static int interface_change_mtu(struct net_device *dev, int new_mtu)
 	return 0;
 }
 
+static int mcast_may_optimize(uint8_t *dest, struct net_device *soft_iface)
+{
+	MC_LIST *mc_entry;
+	struct bat_priv *bat_priv = netdev_priv(soft_iface);
+	int mcast_mode = atomic_read(&bat_priv->mcast_mode);
+
+	if (mcast_mode != MCAST_MODE_PROACT_TRACKING)
+		return 0;
+
+	/* Still allow flooding of multicast packets of protocols where it is
+	 * not easily possible for a multicast sender to be a multicast
+	 * receiver of the same group (for instance IPv6 NDP) */
+	netif_addr_lock_bh(soft_iface);
+	netdev_for_each_mc_addr(mc_entry, soft_iface) {
+		if (memcmp(dest, mc_entry->MC_LIST_ADDR, ETH_ALEN))
+			continue;
+
+		netif_addr_unlock_bh(soft_iface);
+		return 1;
+	}
+	netif_addr_unlock_bh(soft_iface);
+
+	return 0;
+}
+
 int interface_tx(struct sk_buff *skb, struct net_device *soft_iface)
 {
 	struct ethhdr *ethhdr = (struct ethhdr *)skb->data;
@@ -392,8 +417,7 @@ int interface_tx(struct sk_buff *skb, struct net_device *soft_iface)
 
 		if (is_broadcast_ether_addr(ethhdr->h_dest))
 			bcast_dst = true;
-		else if (atomic_read(&bat_priv->mcast_mode) ==
-			 MCAST_MODE_PROACT_TRACKING)
+		else if (mcast_may_optimize(ethhdr->h_dest, soft_iface))
 			mcast_dst = true;
 		else
 			bcast_dst = true;
-- 
1.7.2.3