batman-adv: Send multicast packets to nodes with a WANT_ALL flag

With this patch a node sends IPv4 multicast packets to nodes which
have a BATADV_MCAST_WANT_ALL_IPV4 flag set and IPv6 multicast packets
to nodes which have a BATADV_MCAST_WANT_ALL_IPV6 flag set, too.

Why is this needed? There are scenarios involving bridges where
multicast report snooping and multicast TT announcements are not
sufficient, which would lead to packet loss for some nodes otherwise:

MLDv1 and IGMPv1/IGMPv2 have a suppression mechanism
for multicast listener reports. When we have an MLDv1/IGMPv1/IGMPv2
querier behind a bridge then our snooping bridge is potentially not
going to see any reports even though listeners exist because according
to RFC4541 such reports are only forwarded to multicast routers:

-----------------------------------------------------------
            ---------------
{Querier}---|Snoop. Switch|----{Listener}
            ---------------
                       \           ^
                      -------
                      | br0 |  <  ???
                      -------
                          \
                     _-~---~_
                 _-~/        ~-_
                ~   batman-adv  \-----{Sender}
                \~_   cloud    ~/
                   -~~__-__-~_/

I)  MLDv1 Query:  {Querier}  -> flooded
II) MLDv1 Report: {Listener} -> {Querier}

-> br0 cannot detect the {Listener}
=> Packets from {Sender} need to be forwarded to all
   detected listeners and MLDv1/IGMPv1/IGMPv2 queriers.

-----------------------------------------------------------

Note that we do not need to explicitly forward to MLDv2/IGMPv3 queriers,
because these protocols have no report suppression: A bridge has no
trouble detecting MLDv2/IGMPv3 listeners.

Even though we do not support bridges yet we need to provide the
according infrastructure already to not break compatibility later.

Signed-off-by: Linus Lüssing <linus.luessing@web.de>
Signed-off-by: Marek Lindner <mareklindner@neomailbox.ch>
Signed-off-by: Antonio Quartulli <antonio@meshcoding.com>

1 files changed, 176 insertions, 2 deletions

diff --git a/net/batman-adv/multicast.c b/net/batman-adv/multicast.c
index a4804fa1ad11..8c7ca811de6e 100644
--- a/net/batman-adv/multicast.c
+++ b/net/batman-adv/multicast.c
@@ -361,6 +361,29 @@ static int batadv_mcast_forw_mode_check(struct batadv_priv *bat_priv,
 }
 
 /**
+ * batadv_mcast_want_all_ip_count - count nodes with unspecific mcast interest
+ * @bat_priv: the bat priv with all the soft interface information
+ * @ethhdr: ethernet header of a packet
+ *
+ * Returns the number of nodes which want all IPv4 multicast traffic if the
+ * given ethhdr is from an IPv4 packet or the number of nodes which want all
+ * IPv6 traffic if it matches an IPv6 packet.
+ */
+static int batadv_mcast_forw_want_all_ip_count(struct batadv_priv *bat_priv,
+					       struct ethhdr *ethhdr)
+{
+	switch (ntohs(ethhdr->h_proto)) {
+	case ETH_P_IP:
+		return atomic_read(&bat_priv->mcast.num_want_all_ipv4);
+	case ETH_P_IPV6:
+		return atomic_read(&bat_priv->mcast.num_want_all_ipv6);
+	default:
+		/* we shouldn't be here... */
+		return 0;
+	}
+}
+
+/**
  * batadv_mcast_forw_tt_node_get - get a multicast tt node
  * @bat_priv: the bat priv with all the soft interface information
  * @ethhdr: the ether header containing the multicast destination
@@ -377,6 +400,84 @@ batadv_mcast_forw_tt_node_get(struct batadv_priv *bat_priv,
 }
 
 /**
+ * batadv_mcast_want_forw_ipv4_node_get - get a node with an ipv4 flag
+ * @bat_priv: the bat priv with all the soft interface information
+ *
+ * Returns an orig_node which has the BATADV_MCAST_WANT_ALL_IPV4 flag set and
+ * increases its refcount.
+ */
+static struct batadv_orig_node *
+batadv_mcast_forw_ipv4_node_get(struct batadv_priv *bat_priv)
+{
+	struct batadv_orig_node *tmp_orig_node, *orig_node = NULL;
+
+	rcu_read_lock();
+	hlist_for_each_entry_rcu(tmp_orig_node,
+				 &bat_priv->mcast.want_all_ipv4_list,
+				 mcast_want_all_ipv4_node) {
+		if (!atomic_inc_not_zero(&orig_node->refcount))
+			continue;
+
+		orig_node = tmp_orig_node;
+		break;
+	}
+	rcu_read_unlock();
+
+	return orig_node;
+}
+
+/**
+ * batadv_mcast_want_forw_ipv6_node_get - get a node with an ipv6 flag
+ * @bat_priv: the bat priv with all the soft interface information
+ *
+ * Returns an orig_node which has the BATADV_MCAST_WANT_ALL_IPV6 flag set
+ * and increases its refcount.
+ */
+static struct batadv_orig_node *
+batadv_mcast_forw_ipv6_node_get(struct batadv_priv *bat_priv)
+{
+	struct batadv_orig_node *tmp_orig_node, *orig_node = NULL;
+
+	rcu_read_lock();
+	hlist_for_each_entry_rcu(tmp_orig_node,
+				 &bat_priv->mcast.want_all_ipv6_list,
+				 mcast_want_all_ipv6_node) {
+		if (!atomic_inc_not_zero(&orig_node->refcount))
+			continue;
+
+		orig_node = tmp_orig_node;
+		break;
+	}
+	rcu_read_unlock();
+
+	return orig_node;
+}
+
+/**
+ * batadv_mcast_want_forw_ip_node_get - get a node with an ipv4/ipv6 flag
+ * @bat_priv: the bat priv with all the soft interface information
+ * @ethhdr: an ethernet header to determine the protocol family from
+ *
+ * Returns an orig_node which has the BATADV_MCAST_WANT_ALL_IPV4 or
+ * BATADV_MCAST_WANT_ALL_IPV6 flag, depending on the provided ethhdr, set and
+ * increases its refcount.
+ */
+static struct batadv_orig_node *
+batadv_mcast_forw_ip_node_get(struct batadv_priv *bat_priv,
+			      struct ethhdr *ethhdr)
+{
+	switch (ntohs(ethhdr->h_proto)) {
+	case ETH_P_IP:
+		return batadv_mcast_forw_ipv4_node_get(bat_priv);
+	case ETH_P_IPV6:
+		return batadv_mcast_forw_ipv6_node_get(bat_priv);
+	default:
+		/* we shouldn't be here... */
+		return NULL;
+	}
+}
+
+/**
  * batadv_mcast_want_forw_unsnoop_node_get - get a node with an unsnoopable flag
  * @bat_priv: the bat priv with all the soft interface information
  *
@@ -417,7 +518,7 @@ enum batadv_forw_mode
 batadv_mcast_forw_mode(struct batadv_priv *bat_priv, struct sk_buff *skb,
 		       struct batadv_orig_node **orig)
 {
-	int ret, tt_count, unsnoop_count, total_count;
+	int ret, tt_count, ip_count, unsnoop_count, total_count;
 	bool is_unsnoopable = false;
 	struct ethhdr *ethhdr;
 
@@ -431,15 +532,18 @@ batadv_mcast_forw_mode(struct batadv_priv *bat_priv, struct sk_buff *skb,
 
 	tt_count = batadv_tt_global_hash_count(bat_priv, ethhdr->h_dest,
 					       BATADV_NO_FLAGS);
+	ip_count = batadv_mcast_forw_want_all_ip_count(bat_priv, ethhdr);
 	unsnoop_count = !is_unsnoopable ? 0 :
 			atomic_read(&bat_priv->mcast.num_want_all_unsnoopables);
 
-	total_count = tt_count + unsnoop_count;
+	total_count = tt_count + ip_count + unsnoop_count;
 
 	switch (total_count) {
 	case 1:
 		if (tt_count)
 			*orig = batadv_mcast_forw_tt_node_get(bat_priv, ethhdr);
+		else if (ip_count)
+			*orig = batadv_mcast_forw_ip_node_get(bat_priv, ethhdr);
 		else if (unsnoop_count)
 			*orig = batadv_mcast_forw_unsnoop_node_get(bat_priv);
 
@@ -488,6 +592,72 @@ static void batadv_mcast_want_unsnoop_update(struct batadv_priv *bat_priv,
 }
 
 /**
+ * batadv_mcast_want_ipv4_update - update want-all-ipv4 counter and list
+ * @bat_priv: the bat priv with all the soft interface information
+ * @orig: the orig_node which multicast state might have changed of
+ * @mcast_flags: flags indicating the new multicast state
+ *
+ * If the BATADV_MCAST_WANT_ALL_IPV4 flag of this originator, orig, has
+ * toggled then this method updates counter and list accordingly.
+ */
+static void batadv_mcast_want_ipv4_update(struct batadv_priv *bat_priv,
+					  struct batadv_orig_node *orig,
+					  uint8_t mcast_flags)
+{
+	/* switched from flag unset to set */
+	if (mcast_flags & BATADV_MCAST_WANT_ALL_IPV4 &&
+	    !(orig->mcast_flags & BATADV_MCAST_WANT_ALL_IPV4)) {
+		atomic_inc(&bat_priv->mcast.num_want_all_ipv4);
+
+		spin_lock_bh(&bat_priv->mcast.want_lists_lock);
+		hlist_add_head_rcu(&orig->mcast_want_all_ipv4_node,
+				   &bat_priv->mcast.want_all_ipv4_list);
+		spin_unlock_bh(&bat_priv->mcast.want_lists_lock);
+	/* switched from flag set to unset */
+	} else if (!(mcast_flags & BATADV_MCAST_WANT_ALL_IPV4) &&
+		   orig->mcast_flags & BATADV_MCAST_WANT_ALL_IPV4) {
+		atomic_dec(&bat_priv->mcast.num_want_all_ipv4);
+
+		spin_lock_bh(&bat_priv->mcast.want_lists_lock);
+		hlist_del_rcu(&orig->mcast_want_all_ipv4_node);
+		spin_unlock_bh(&bat_priv->mcast.want_lists_lock);
+	}
+}
+
+/**
+ * batadv_mcast_want_ipv6_update - update want-all-ipv6 counter and list
+ * @bat_priv: the bat priv with all the soft interface information
+ * @orig: the orig_node which multicast state might have changed of
+ * @mcast_flags: flags indicating the new multicast state
+ *
+ * If the BATADV_MCAST_WANT_ALL_IPV6 flag of this originator, orig, has
+ * toggled then this method updates counter and list accordingly.
+ */
+static void batadv_mcast_want_ipv6_update(struct batadv_priv *bat_priv,
+					  struct batadv_orig_node *orig,
+					  uint8_t mcast_flags)
+{
+	/* switched from flag unset to set */
+	if (mcast_flags & BATADV_MCAST_WANT_ALL_IPV6 &&
+	    !(orig->mcast_flags & BATADV_MCAST_WANT_ALL_IPV6)) {
+		atomic_inc(&bat_priv->mcast.num_want_all_ipv6);
+
+		spin_lock_bh(&bat_priv->mcast.want_lists_lock);
+		hlist_add_head_rcu(&orig->mcast_want_all_ipv6_node,
+				   &bat_priv->mcast.want_all_ipv6_list);
+		spin_unlock_bh(&bat_priv->mcast.want_lists_lock);
+	/* switched from flag set to unset */
+	} else if (!(mcast_flags & BATADV_MCAST_WANT_ALL_IPV6) &&
+		   orig->mcast_flags & BATADV_MCAST_WANT_ALL_IPV6) {
+		atomic_dec(&bat_priv->mcast.num_want_all_ipv6);
+
+		spin_lock_bh(&bat_priv->mcast.want_lists_lock);
+		hlist_del_rcu(&orig->mcast_want_all_ipv6_node);
+		spin_unlock_bh(&bat_priv->mcast.want_lists_lock);
+	}
+}
+
+/**
  * batadv_mcast_tvlv_ogm_handler_v1 - process incoming multicast tvlv container
  * @bat_priv: the bat priv with all the soft interface information
  * @orig: the orig_node of the ogm
@@ -532,6 +702,8 @@ static void batadv_mcast_tvlv_ogm_handler_v1(struct batadv_priv *bat_priv,
 		mcast_flags = *(uint8_t *)tvlv_value;
 
 	batadv_mcast_want_unsnoop_update(bat_priv, orig, mcast_flags);
+	batadv_mcast_want_ipv4_update(bat_priv, orig, mcast_flags);
+	batadv_mcast_want_ipv6_update(bat_priv, orig, mcast_flags);
 
 	orig->mcast_flags = mcast_flags;
 }
@@ -571,4 +743,6 @@ void batadv_mcast_purge_orig(struct batadv_orig_node *orig)
 		atomic_dec(&bat_priv->mcast.num_disabled);
 
 	batadv_mcast_want_unsnoop_update(bat_priv, orig, BATADV_NO_FLAGS);
+	batadv_mcast_want_ipv4_update(bat_priv, orig, BATADV_NO_FLAGS);
+	batadv_mcast_want_ipv6_update(bat_priv, orig, BATADV_NO_FLAGS);
 }