batman-adv: Modified forwarding behaviour for multicast packets

With this patch a multicast packet is not always simply flooded anymore,
the behaviour for the following cases is changed to reduce
unnecessary overhead:

If all nodes within the horizon of a certain node have signalized
multicast listener announcement capability then an IPv6 multicast packet
with a destination of IPv6 link-local scope (excluding ff02::1) coming
from the upstream of this node...

* ...is dropped if there is no according multicast listener in the
  translation table,
* ...is forwarded via unicast if there is a single node with interested
  multicast listeners
* ...and otherwise still gets flooded.

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>

9 files changed, 266 insertions, 26 deletions

diff --git a/net/batman-adv/multicast.c b/net/batman-adv/multicast.c
index 3ba9a18a906c..1d1627fe0de0 100644
--- a/net/batman-adv/multicast.c
+++ b/net/batman-adv/multicast.c
@@ -20,6 +20,7 @@
 #include "originator.h"
 #include "hard-interface.h"
 #include "translation-table.h"
+#include "multicast.h"
 
 /**
  * batadv_mcast_mla_softif_get - get softif multicast listeners
@@ -247,6 +248,131 @@ out:
 }
 
 /**
+ * batadv_mcast_forw_mode_check_ipv6 - check for optimized forwarding potential
+ * @bat_priv: the bat priv with all the soft interface information
+ * @skb: the IPv6 packet to check
+ *
+ * Checks whether the given IPv6 packet has the potential to be forwarded with a
+ * mode more optimal than classic flooding.
+ *
+ * If so then returns 0. Otherwise -EINVAL is returned or -ENOMEM if we are out
+ * of memory.
+ */
+static int batadv_mcast_forw_mode_check_ipv6(struct batadv_priv *bat_priv,
+                                             struct sk_buff *skb)
+{
+        struct ipv6hdr *ip6hdr;
+
+        /* We might fail due to out-of-memory -> drop it */
+        if (!pskb_may_pull(skb, sizeof(struct ethhdr) + sizeof(*ip6hdr)))
+                return -ENOMEM;
+
+        ip6hdr = ipv6_hdr(skb);
+
+        /* TODO: Implement Multicast Router Discovery (RFC4286),
+         * then allow scope > link local, too
+         */
+        if (IPV6_ADDR_MC_SCOPE(&ip6hdr->daddr) != IPV6_ADDR_SCOPE_LINKLOCAL)
+                return -EINVAL;
+
+        /* link-local-all-nodes multicast listeners behind a bridge are
+         * not snoopable (see RFC4541, section 3, paragraph 3)
+         */
+        if (ipv6_addr_is_ll_all_nodes(&ip6hdr->daddr))
+                return -EINVAL;
+
+        return 0;
+}
+
+/**
+ * batadv_mcast_forw_mode_check - check for optimized forwarding potential
+ * @bat_priv: the bat priv with all the soft interface information
+ * @skb: the multicast frame to check
+ *
+ * Checks whether the given multicast ethernet frame has the potential to be
+ * forwarded with a mode more optimal than classic flooding.
+ *
+ * If so then returns 0. Otherwise -EINVAL is returned or -ENOMEM if we are out
+ * of memory.
+ */
+static int batadv_mcast_forw_mode_check(struct batadv_priv *bat_priv,
+                                        struct sk_buff *skb)
+{
+        struct ethhdr *ethhdr = eth_hdr(skb);
+
+        if (!atomic_read(&bat_priv->multicast_mode))
+                return -EINVAL;
+
+        if (atomic_read(&bat_priv->mcast.num_disabled))
+                return -EINVAL;
+
+        switch (ntohs(ethhdr->h_proto)) {
+        case ETH_P_IPV6:
+                return batadv_mcast_forw_mode_check_ipv6(bat_priv, skb);
+        default:
+                return -EINVAL;
+        }
+}
+
+/**
+ * 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
+ *
+ * Returns an orig_node matching the multicast address provided by ethhdr
+ * via a translation table lookup. This increases the returned nodes refcount.
+ */
+static struct batadv_orig_node *
+batadv_mcast_forw_tt_node_get(struct batadv_priv *bat_priv,
+                              struct ethhdr *ethhdr)
+{
+        return batadv_transtable_search(bat_priv, ethhdr->h_source,
+                                        ethhdr->h_dest, BATADV_NO_FLAGS);
+}
+
+/**
+ * batadv_mcast_forw_mode - check on how to forward a multicast packet
+ * @bat_priv: the bat priv with all the soft interface information
+ * @skb: The multicast packet to check
+ * @orig: an originator to be set to forward the skb to
+ *
+ * Returns the forwarding mode as enum batadv_forw_mode and in case of
+ * BATADV_FORW_SINGLE set the orig to the single originator the skb
+ * should be forwarded to.
+ */
+enum batadv_forw_mode
+batadv_mcast_forw_mode(struct batadv_priv *bat_priv, struct sk_buff *skb,
+                       struct batadv_orig_node **orig)
+{
+        struct ethhdr *ethhdr;
+        int ret, tt_count;
+
+        ret = batadv_mcast_forw_mode_check(bat_priv, skb);
+        if (ret == -ENOMEM)
+                return BATADV_FORW_NONE;
+        else if (ret < 0)
+                return BATADV_FORW_ALL;
+
+        ethhdr = eth_hdr(skb);
+
+        tt_count = batadv_tt_global_hash_count(bat_priv, ethhdr->h_dest,
+                                               BATADV_NO_FLAGS);
+
+        switch (tt_count) {
+        case 1:
+                *orig = batadv_mcast_forw_tt_node_get(bat_priv, ethhdr);
+                if (*orig)
+                        return BATADV_FORW_SINGLE;
+
+                /* fall through */
+        case 0:
+                return BATADV_FORW_NONE;
+        default:
+                return BATADV_FORW_ALL;
+        }
+}
+
+/**
  * 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
diff --git a/net/batman-adv/multicast.h b/net/batman-adv/multicast.h
index c029eaca7c44..73b5d45819c1 100644
--- a/net/batman-adv/multicast.h
+++ b/net/batman-adv/multicast.h
@@ -18,10 +18,28 @@
 #ifndef _NET_BATMAN_ADV_MULTICAST_H_
 #define _NET_BATMAN_ADV_MULTICAST_H_
 
+/**
+ * batadv_forw_mode - the way a packet should be forwarded as
+ * @BATADV_FORW_ALL: forward the packet to all nodes (currently via classic
+ *  flooding)
+ * @BATADV_FORW_SINGLE: forward the packet to a single node (currently via the
+ *  BATMAN unicast routing protocol)
+ * @BATADV_FORW_NONE: don't forward, drop it
+ */
+enum batadv_forw_mode {
+        BATADV_FORW_ALL,
+        BATADV_FORW_SINGLE,
+        BATADV_FORW_NONE,
+};
+
 #ifdef CONFIG_BATMAN_ADV_MCAST
 
 void batadv_mcast_mla_update(struct batadv_priv *bat_priv);
 
+enum batadv_forw_mode
+batadv_mcast_forw_mode(struct batadv_priv *bat_priv, struct sk_buff *skb,
+                       struct batadv_orig_node **mcast_single_orig);
+
 void batadv_mcast_init(struct batadv_priv *bat_priv);
 
 void batadv_mcast_free(struct batadv_priv *bat_priv);
@@ -35,6 +53,13 @@ static inline void batadv_mcast_mla_update(struct batadv_priv *bat_priv)
         return;
 }
 
+static inline enum batadv_forw_mode
+batadv_mcast_forw_mode(struct batadv_priv *bat_priv, struct sk_buff *skb,
+                       struct batadv_orig_node **mcast_single_orig)
+{
+        return BATADV_FORW_ALL;
+}
+
 static inline int batadv_mcast_init(struct batadv_priv *bat_priv)
 {
         return 0;
diff --git a/net/batman-adv/send.c b/net/batman-adv/send.c
index ce163d50e5d7..8bee5e8536b7 100644
--- a/net/batman-adv/send.c
+++ b/net/batman-adv/send.c
@@ -248,11 +248,11 @@ out:
  *
  * Returns NET_XMIT_DROP in case of error or NET_XMIT_SUCCESS otherwise.
  */
-static int batadv_send_skb_unicast(struct batadv_priv *bat_priv,
-                                   struct sk_buff *skb, int packet_type,
-                                   int packet_subtype,
-                                   struct batadv_orig_node *orig_node,
-                                   unsigned short vid)
+int batadv_send_skb_unicast(struct batadv_priv *bat_priv,
+                            struct sk_buff *skb, int packet_type,
+                            int packet_subtype,
+                            struct batadv_orig_node *orig_node,
+                            unsigned short vid)
 {
         struct ethhdr *ethhdr;
         struct batadv_unicast_packet *unicast_packet;
diff --git a/net/batman-adv/send.h b/net/batman-adv/send.h
index 31e87811ce5b..38d0ec1833ae 100644
--- a/net/batman-adv/send.h
+++ b/net/batman-adv/send.h
@@ -36,6 +36,11 @@ bool batadv_send_skb_prepare_unicast_4addr(struct batadv_priv *bat_priv,
                                            struct sk_buff *skb,
                                            struct batadv_orig_node *orig_node,
                                            int packet_subtype);
+int batadv_send_skb_unicast(struct batadv_priv *bat_priv,
+                            struct sk_buff *skb, int packet_type,
+                            int packet_subtype,
+                            struct batadv_orig_node *orig_node,
+                            unsigned short vid);
 int batadv_send_skb_via_tt_generic(struct batadv_priv *bat_priv,
                                    struct sk_buff *skb, int packet_type,
                                    int packet_subtype, uint8_t *dst_hint,
diff --git a/net/batman-adv/soft-interface.c b/net/batman-adv/soft-interface.c
index 8ff47b7a0e04..1a643fe647e1 100644
--- a/net/batman-adv/soft-interface.c
+++ b/net/batman-adv/soft-interface.c
@@ -32,6 +32,7 @@
 #include <linux/ethtool.h>
 #include <linux/etherdevice.h>
 #include <linux/if_vlan.h>
+#include "multicast.h"
 #include "bridge_loop_avoidance.h"
 #include "network-coding.h"
 
@@ -170,6 +171,8 @@ static int batadv_interface_tx(struct sk_buff *skb,
         unsigned short vid;
         uint32_t seqno;
         int gw_mode;
+        enum batadv_forw_mode forw_mode;
+        struct batadv_orig_node *mcast_single_orig = NULL;
 
         if (atomic_read(&bat_priv->mesh_state) != BATADV_MESH_ACTIVE)
                 goto dropped;
@@ -247,9 +250,19 @@ static int batadv_interface_tx(struct sk_buff *skb,
                          * directed to a DHCP server
                          */
                         goto dropped;
-        }
 
 send:
+                if (do_bcast && !is_broadcast_ether_addr(ethhdr->h_dest)) {
+                        forw_mode = batadv_mcast_forw_mode(bat_priv, skb,
+                                                           &mcast_single_orig);
+                        if (forw_mode == BATADV_FORW_NONE)
+                                goto dropped;
+
+                        if (forw_mode == BATADV_FORW_SINGLE)
+                                do_bcast = false;
+                }
+        }
+
         batadv_skb_set_priority(skb, 0);
 
         /* ethernet packet should be broadcasted */
@@ -301,6 +314,10 @@ send:
                         if (ret)
                                 goto dropped;
                         ret = batadv_send_skb_via_gw(bat_priv, skb, vid);
+                } else if (mcast_single_orig) {
+                        ret = batadv_send_skb_unicast(bat_priv, skb,
+                                                      BATADV_UNICAST, 0,
+                                                      mcast_single_orig, vid);
                 } else {
                         if (batadv_dat_snoop_outgoing_arp_request(bat_priv,
                                                                   skb))
@@ -691,6 +708,7 @@ static int batadv_softif_init_late(struct net_device *dev)
 #endif
 #ifdef CONFIG_BATMAN_ADV_MCAST
         bat_priv->mcast.flags = BATADV_NO_FLAGS;
+        atomic_set(&bat_priv->multicast_mode, 1);
         atomic_set(&bat_priv->mcast.num_disabled, 0);
 #endif
         atomic_set(&bat_priv->gw_mode, BATADV_GW_MODE_OFF);
diff --git a/net/batman-adv/sysfs.c b/net/batman-adv/sysfs.c
index e456bf6bb284..1ebb0d9e2ea5 100644
--- a/net/batman-adv/sysfs.c
+++ b/net/batman-adv/sysfs.c
@@ -539,6 +539,9 @@ BATADV_ATTR_SIF_UINT(gw_sel_class, S_IRUGO | S_IWUSR, 1, BATADV_TQ_MAX_VALUE,
                      batadv_post_gw_reselect);
 static BATADV_ATTR(gw_bandwidth, S_IRUGO | S_IWUSR, batadv_show_gw_bwidth,
                    batadv_store_gw_bwidth);
+#ifdef CONFIG_BATMAN_ADV_MCAST
+BATADV_ATTR_SIF_BOOL(multicast_mode, S_IRUGO | S_IWUSR, NULL);
+#endif
 #ifdef CONFIG_BATMAN_ADV_DEBUG
 BATADV_ATTR_SIF_UINT(log_level, S_IRUGO | S_IWUSR, 0, BATADV_DBG_ALL, NULL);
 #endif
@@ -558,6 +561,9 @@ static struct batadv_attribute *batadv_mesh_attrs[] = {
 #ifdef CONFIG_BATMAN_ADV_DAT
         &batadv_attr_distributed_arp_table,
 #endif
+#ifdef CONFIG_BATMAN_ADV_MCAST
+        &batadv_attr_multicast_mode,
+#endif
         &batadv_attr_fragmentation,
         &batadv_attr_routing_algo,
         &batadv_attr_gw_mode,
diff --git a/net/batman-adv/translation-table.c b/net/batman-adv/translation-table.c
index f641dfe302a4..d636bde72c9a 100644
--- a/net/batman-adv/translation-table.c
+++ b/net/batman-adv/translation-table.c
@@ -193,6 +193,31 @@ batadv_tt_global_entry_free_ref(struct batadv_tt_global_entry *tt_global_entry)
         }
 }
 
+/**
+ * batadv_tt_global_hash_count - count the number of orig entries
+ * @hash: hash table containing the tt entries
+ * @addr: the mac address of the client to count entries for
+ * @vid: VLAN identifier
+ *
+ * Return the number of originators advertising the given address/data
+ * (excluding ourself).
+ */
+int batadv_tt_global_hash_count(struct batadv_priv *bat_priv,
+                                const uint8_t *addr, unsigned short vid)
+{
+        struct batadv_tt_global_entry *tt_global_entry;
+        int count;
+
+        tt_global_entry = batadv_tt_global_hash_find(bat_priv, addr, vid);
+        if (!tt_global_entry)
+                return 0;
+
+        count = atomic_read(&tt_global_entry->orig_list_count);
+        batadv_tt_global_entry_free_ref(tt_global_entry);
+
+        return count;
+}
+
 static void batadv_tt_orig_list_entry_free_rcu(struct rcu_head *rcu)
 {
         struct batadv_tt_orig_list_entry *orig_entry;
@@ -1225,6 +1250,8 @@ batadv_tt_global_orig_entry_add(struct batadv_tt_global_entry *tt_global,
         hlist_add_head_rcu(&orig_entry->list,
                            &tt_global->orig_list);
         spin_unlock_bh(&tt_global->list_lock);
+        atomic_inc(&tt_global->orig_list_count);
+
 out:
         if (orig_entry)
                 batadv_tt_orig_list_entry_free_ref(orig_entry);
@@ -1298,6 +1325,7 @@ static bool batadv_tt_global_add(struct batadv_priv *bat_priv,
                 common->added_at = jiffies;
 
                 INIT_HLIST_HEAD(&tt_global_entry->orig_list);
+                atomic_set(&tt_global_entry->orig_list_count, 0);
                 spin_lock_init(&tt_global_entry->list_lock);
 
                 hash_added = batadv_hash_add(bat_priv->tt.global_hash,
@@ -1563,6 +1591,25 @@ out:
         return 0;
 }
 
+/**
+ * batadv_tt_global_del_orig_entry - remove and free an orig_entry
+ * @tt_global_entry: the global entry to remove the orig_entry from
+ * @orig_entry: the orig entry to remove and free
+ *
+ * Remove an orig_entry from its list in the given tt_global_entry and
+ * free this orig_entry afterwards.
+ */
+static void
+batadv_tt_global_del_orig_entry(struct batadv_tt_global_entry *tt_global_entry,
+                                struct batadv_tt_orig_list_entry *orig_entry)
+{
+        batadv_tt_global_size_dec(orig_entry->orig_node,
+                                  tt_global_entry->common.vid);
+        atomic_dec(&tt_global_entry->orig_list_count);
+        hlist_del_rcu(&orig_entry->list);
+        batadv_tt_orig_list_entry_free_ref(orig_entry);
+}
+
 /* deletes the orig list of a tt_global_entry */
 static void
 batadv_tt_global_del_orig_list(struct batadv_tt_global_entry *tt_global_entry)
@@ -1573,20 +1620,26 @@ batadv_tt_global_del_orig_list(struct batadv_tt_global_entry *tt_global_entry)
 
         spin_lock_bh(&tt_global_entry->list_lock);
         head = &tt_global_entry->orig_list;
-        hlist_for_each_entry_safe(orig_entry, safe, head, list) {
-                hlist_del_rcu(&orig_entry->list);
-                batadv_tt_global_size_dec(orig_entry->orig_node,
-                                          tt_global_entry->common.vid);
-                batadv_tt_orig_list_entry_free_ref(orig_entry);
-        }
+        hlist_for_each_entry_safe(orig_entry, safe, head, list)
+                batadv_tt_global_del_orig_entry(tt_global_entry, orig_entry);
         spin_unlock_bh(&tt_global_entry->list_lock);
 }
 
+/**
+ * batadv_tt_global_del_orig_node - remove orig_node from a global tt entry
+ * @bat_priv: the bat priv with all the soft interface information
+ * @tt_global_entry: the global entry to remove the orig_node from
+ * @orig_node: the originator announcing the client
+ * @message: message to append to the log on deletion
+ *
+ * Remove the given orig_node and its according orig_entry from the given
+ * global tt entry.
+ */
 static void
-batadv_tt_global_del_orig_entry(struct batadv_priv *bat_priv,
-                                struct batadv_tt_global_entry *tt_global_entry,
-                                struct batadv_orig_node *orig_node,
-                                const char *message)
+batadv_tt_global_del_orig_node(struct batadv_priv *bat_priv,
+                               struct batadv_tt_global_entry *tt_global_entry,
+                               struct batadv_orig_node *orig_node,
+                               const char *message)
 {
         struct hlist_head *head;
         struct hlist_node *safe;
@@ -1603,10 +1656,8 @@ batadv_tt_global_del_orig_entry(struct batadv_priv *bat_priv,
                                    orig_node->orig,
                                    tt_global_entry->common.addr,
                                    BATADV_PRINT_VID(vid), message);
-                        hlist_del_rcu(&orig_entry->list);
-                        batadv_tt_global_size_dec(orig_node,
-                                                  tt_global_entry->common.vid);
-                        batadv_tt_orig_list_entry_free_ref(orig_entry);
+                        batadv_tt_global_del_orig_entry(tt_global_entry,
+                                                        orig_entry);
                 }
         }
         spin_unlock_bh(&tt_global_entry->list_lock);
@@ -1648,8 +1699,8 @@ batadv_tt_global_del_roaming(struct batadv_priv *bat_priv,
                 /* there is another entry, we can simply delete this
                  * one and can still use the other one.
                  */
-                batadv_tt_global_del_orig_entry(bat_priv, tt_global_entry,
-                                                orig_node, message);
+                batadv_tt_global_del_orig_node(bat_priv, tt_global_entry,
+                                               orig_node, message);
 }
 
 /**
@@ -1675,8 +1726,8 @@ static void batadv_tt_global_del(struct batadv_priv *bat_priv,
                 goto out;
 
         if (!roaming) {
-                batadv_tt_global_del_orig_entry(bat_priv, tt_global_entry,
-                                                orig_node, message);
+                batadv_tt_global_del_orig_node(bat_priv, tt_global_entry,
+                                               orig_node, message);
 
                 if (hlist_empty(&tt_global_entry->orig_list))
                         batadv_tt_global_free(bat_priv, tt_global_entry,
@@ -1759,8 +1810,8 @@ void batadv_tt_global_del_orig(struct batadv_priv *bat_priv,
                                                  struct batadv_tt_global_entry,
                                                  common);
 
-                        batadv_tt_global_del_orig_entry(bat_priv, tt_global,
-                                                        orig_node, message);
+                        batadv_tt_global_del_orig_node(bat_priv, tt_global,
+                                                       orig_node, message);
 
                         if (hlist_empty(&tt_global->orig_list)) {
                                 vid = tt_global->common.vid;
diff --git a/net/batman-adv/translation-table.h b/net/batman-adv/translation-table.h
index 20a1d7861ded..ad84d7b89e39 100644
--- a/net/batman-adv/translation-table.h
+++ b/net/batman-adv/translation-table.h
@@ -29,6 +29,8 @@ int batadv_tt_global_seq_print_text(struct seq_file *seq, void *offset);
 void batadv_tt_global_del_orig(struct batadv_priv *bat_priv,
                                struct batadv_orig_node *orig_node,
                                int32_t match_vid, const char *message);
+int batadv_tt_global_hash_count(struct batadv_priv *bat_priv,
+                                const uint8_t *addr, unsigned short vid);
 struct batadv_orig_node *batadv_transtable_search(struct batadv_priv *bat_priv,
                                                   const uint8_t *src,
                                                   const uint8_t *addr,
diff --git a/net/batman-adv/types.h b/net/batman-adv/types.h
index 96ee0d2b11d9..c28fc4a403a3 100644
--- a/net/batman-adv/types.h
+++ b/net/batman-adv/types.h
@@ -696,6 +696,8 @@ struct batadv_softif_vlan {
  *  enabled
  * @distributed_arp_table: bool indicating whether distributed ARP table is
  *  enabled
+ * @multicast_mode: Enable or disable multicast optimizations on this node's
+ *  sender/originating side
  * @gw_mode: gateway operation: off, client or server (see batadv_gw_modes)
  * @gw_sel_class: gateway selection class (applies if gw_mode client)
  * @orig_interval: OGM broadcast interval in milliseconds
@@ -746,6 +748,9 @@ struct batadv_priv {
 #ifdef CONFIG_BATMAN_ADV_DAT
         atomic_t distributed_arp_table;
 #endif
+#ifdef CONFIG_BATMAN_ADV_MCAST
+        atomic_t multicast_mode;
+#endif
         atomic_t gw_mode;
         atomic_t gw_sel_class;
         atomic_t orig_interval;
@@ -909,12 +914,14 @@ struct batadv_tt_local_entry {
  * struct batadv_tt_global_entry - translation table global entry data
  * @common: general translation table data
  * @orig_list: list of orig nodes announcing this non-mesh client
+ * @orig_list_count: number of items in the orig_list
  * @list_lock: lock protecting orig_list
  * @roam_at: time at which TT_GLOBAL_ROAM was set
  */
 struct batadv_tt_global_entry {
         struct batadv_tt_common_entry common;
         struct hlist_head orig_list;
+        atomic_t orig_list_count;
         spinlock_t list_lock;   /* protects orig_list */
         unsigned long roam_at;
 };