batman-adv: Add IPv4 link-local/IPv6-ll-all-nodes multicast support

With this patch a node may additionally perform the dropping or
unicasting behaviour for a link-local IPv4 and link-local-all-nodes
IPv6 multicast packet, too.

The extra counter and BATADV_MCAST_WANT_ALL_UNSNOOPABLES flag is needed
because with a future bridge snooping support integration a node with a
bridge on top of its soft interface is not able to reliably detect its
multicast listeners for IPv4 link-local and the IPv6
link-local-all-nodes addresses anymore (see RFC4541, section 2.1.2.2
and section 3).

Even though this new flag does make "no difference" now, it'll ensure
a seamless integration of multicast bridge support without needing to
break compatibility later.

Also note, that even with multicast bridge support it won't be possible
to optimize 224.0.0.x and ff02::1 towards nodes with bridges, they will
always receive these ranges.

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, 127 insertions, 8 deletions

diff --git a/net/batman-adv/multicast.c b/net/batman-adv/multicast.c
index 1d1627fe0de0..a4804fa1ad11 100644
--- a/net/batman-adv/multicast.c
+++ b/net/batman-adv/multicast.c
@@ -248,9 +248,48 @@ out:
 }
 
 /**
+ * batadv_mcast_forw_mode_check_ipv4 - check for optimized forwarding potential
+ * @bat_priv: the bat priv with all the soft interface information
+ * @skb: the IPv4 packet to check
+ * @is_unsnoopable: stores whether the destination is snoopable
+ *
+ * Checks whether the given IPv4 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 in case of
+ * memory allocation failure.
+ */
+static int batadv_mcast_forw_mode_check_ipv4(struct batadv_priv *bat_priv,
+                                             struct sk_buff *skb,
+                                             bool *is_unsnoopable)
+{
+        struct iphdr *iphdr;
+
+        /* We might fail due to out-of-memory -> drop it */
+        if (!pskb_may_pull(skb, sizeof(struct ethhdr) + sizeof(*iphdr)))
+                return -ENOMEM;
+
+        iphdr = ip_hdr(skb);
+
+        /* TODO: Implement Multicast Router Discovery (RFC4286),
+         * then allow scope > link local, too
+         */
+        if (!ipv4_is_local_multicast(iphdr->daddr))
+                return -EINVAL;
+
+        /* link-local multicast listeners behind a bridge are
+         * not snoopable (see RFC4541, section 2.1.2.2)
+         */
+        *is_unsnoopable = true;
+
+        return 0;
+}
+
+/**
  * 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
+ * @is_unsnoopable: stores whether the destination is snoopable
  *
  * Checks whether the given IPv6 packet has the potential to be forwarded with a
  * mode more optimal than classic flooding.
@@ -259,7 +298,8 @@ out:
  * of memory.
  */
 static int batadv_mcast_forw_mode_check_ipv6(struct batadv_priv *bat_priv,
-                                             struct sk_buff *skb)
+                                             struct sk_buff *skb,
+                                             bool *is_unsnoopable)
 {
         struct ipv6hdr *ip6hdr;
 
@@ -279,7 +319,7 @@ static int batadv_mcast_forw_mode_check_ipv6(struct batadv_priv *bat_priv,
          * not snoopable (see RFC4541, section 3, paragraph 3)
          */
         if (ipv6_addr_is_ll_all_nodes(&ip6hdr->daddr))
-                return -EINVAL;
+                *is_unsnoopable = true;
 
         return 0;
 }
@@ -288,6 +328,7 @@ static int batadv_mcast_forw_mode_check_ipv6(struct batadv_priv *bat_priv,
  * 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
+ * @is_unsnoopable: stores whether the destination is snoopable
  *
  * Checks whether the given multicast ethernet frame has the potential to be
  * forwarded with a mode more optimal than classic flooding.
@@ -296,7 +337,8 @@ static int batadv_mcast_forw_mode_check_ipv6(struct batadv_priv *bat_priv,
  * of memory.
  */
 static int batadv_mcast_forw_mode_check(struct batadv_priv *bat_priv,
-                                        struct sk_buff *skb)
+                                        struct sk_buff *skb,
+                                        bool *is_unsnoopable)
 {
         struct ethhdr *ethhdr = eth_hdr(skb);
 
@@ -307,8 +349,12 @@ static int batadv_mcast_forw_mode_check(struct batadv_priv *bat_priv,
                 return -EINVAL;
 
         switch (ntohs(ethhdr->h_proto)) {
+        case ETH_P_IP:
+                return batadv_mcast_forw_mode_check_ipv4(bat_priv, skb,
+                                                         is_unsnoopable);
         case ETH_P_IPV6:
-                return batadv_mcast_forw_mode_check_ipv6(bat_priv, skb);
+                return batadv_mcast_forw_mode_check_ipv6(bat_priv, skb,
+                                                         is_unsnoopable);
         default:
                 return -EINVAL;
         }
@@ -331,6 +377,33 @@ batadv_mcast_forw_tt_node_get(struct batadv_priv *bat_priv,
 }
 
 /**
+ * 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
+ *
+ * Returns an orig_node which has the BATADV_MCAST_WANT_ALL_UNSNOOPABLES flag
+ * set and increases its refcount.
+ */
+static struct batadv_orig_node *
+batadv_mcast_forw_unsnoop_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_unsnoopables_list,
+                                 mcast_want_all_unsnoopables_node) {
+                if (!atomic_inc_not_zero(&orig_node->refcount))
+                        continue;
+
+                orig_node = tmp_orig_node;
+                break;
+        }
+        rcu_read_unlock();
+
+        return orig_node;
+}
+
+/**
  * 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
@@ -344,10 +417,11 @@ 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;
+        bool is_unsnoopable = false;
         struct ethhdr *ethhdr;
-        int ret, tt_count;
 
-        ret = batadv_mcast_forw_mode_check(bat_priv, skb);
+        ret = batadv_mcast_forw_mode_check(bat_priv, skb, &is_unsnoopable);
         if (ret == -ENOMEM)
                 return BATADV_FORW_NONE;
         else if (ret < 0)
@@ -357,10 +431,18 @@ 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);
+        unsnoop_count = !is_unsnoopable ? 0 :
+                        atomic_read(&bat_priv->mcast.num_want_all_unsnoopables);
+
+        total_count = tt_count + unsnoop_count;
 
-        switch (tt_count) {
+        switch (total_count) {
         case 1:
-                *orig = batadv_mcast_forw_tt_node_get(bat_priv, ethhdr);
+                if (tt_count)
+                        *orig = batadv_mcast_forw_tt_node_get(bat_priv, ethhdr);
+                else if (unsnoop_count)
+                        *orig = batadv_mcast_forw_unsnoop_node_get(bat_priv);
+
                 if (*orig)
                         return BATADV_FORW_SINGLE;
 
@@ -373,6 +455,39 @@ batadv_mcast_forw_mode(struct batadv_priv *bat_priv, struct sk_buff *skb,
 }
 
 /**
+ * batadv_mcast_want_unsnoop_update - update unsnoop 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_UNSNOOPABLES flag of this originator,
+ * orig, has toggled then this method updates counter and list accordingly.
+ */
+static void batadv_mcast_want_unsnoop_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_UNSNOOPABLES &&
+            !(orig->mcast_flags & BATADV_MCAST_WANT_ALL_UNSNOOPABLES)) {
+                atomic_inc(&bat_priv->mcast.num_want_all_unsnoopables);
+
+                spin_lock_bh(&bat_priv->mcast.want_lists_lock);
+                hlist_add_head_rcu(&orig->mcast_want_all_unsnoopables_node,
+                                   &bat_priv->mcast.want_all_unsnoopables_list);
+                spin_unlock_bh(&bat_priv->mcast.want_lists_lock);
+        /* switched from flag set to unset */
+        } else if (!(mcast_flags & BATADV_MCAST_WANT_ALL_UNSNOOPABLES) &&
+                   orig->mcast_flags & BATADV_MCAST_WANT_ALL_UNSNOOPABLES) {
+                atomic_dec(&bat_priv->mcast.num_want_all_unsnoopables);
+
+                spin_lock_bh(&bat_priv->mcast.want_lists_lock);
+                hlist_del_rcu(&orig->mcast_want_all_unsnoopables_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
@@ -416,6 +531,8 @@ static void batadv_mcast_tvlv_ogm_handler_v1(struct batadv_priv *bat_priv,
             (tvlv_value_len >= sizeof(mcast_flags)))
                 mcast_flags = *(uint8_t *)tvlv_value;
 
+        batadv_mcast_want_unsnoop_update(bat_priv, orig, mcast_flags);
+
         orig->mcast_flags = mcast_flags;
 }
 
@@ -452,4 +569,6 @@ void batadv_mcast_purge_orig(struct batadv_orig_node *orig)
 
         if (!(orig->capabilities & BATADV_ORIG_CAPA_HAS_MCAST))
                 atomic_dec(&bat_priv->mcast.num_disabled);
+
+        batadv_mcast_want_unsnoop_update(bat_priv, orig, BATADV_NO_FLAGS);
 }