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, 13 insertions, 1 deletions

diff --git a/net/batman-adv/types.h b/net/batman-adv/types.h
index 1a674cb19553..d4b923c7229c 100644
--- a/net/batman-adv/types.h
+++ b/net/batman-adv/types.h
@@ -207,6 +207,8 @@ struct batadv_orig_bat_iv {
  * @mcast_flags: multicast flags announced by the orig node
  * @mcast_want_all_unsnoop_node: a list node for the
  *  mcast.want_all_unsnoopables list
+ * @mcast_want_all_ipv4_node: a list node for the mcast.want_all_ipv4 list
+ * @mcast_want_all_ipv6_node: a list node for the mcast.want_all_ipv6 list
  * @capabilities: announced capabilities of this originator
  * @capa_initialized: bitfield to remember whether a capability was initialized
  * @last_ttvn: last seen translation table version number
@@ -252,6 +254,8 @@ struct batadv_orig_node {
 #ifdef CONFIG_BATMAN_ADV_MCAST
 	uint8_t mcast_flags;
 	struct hlist_node mcast_want_all_unsnoopables_node;
+	struct hlist_node mcast_want_all_ipv4_node;
+	struct hlist_node mcast_want_all_ipv6_node;
 #endif
 	uint8_t capabilities;
 	uint8_t capa_initialized;
@@ -624,21 +628,29 @@ struct batadv_priv_dat {
  * @mla_list: list of multicast addresses we are currently announcing via TT
  * @want_all_unsnoopables_list: a list of orig_nodes wanting all unsnoopable
  *  multicast traffic
+ * @want_all_ipv4_list: a list of orig_nodes wanting all IPv4 multicast traffic
+ * @want_all_ipv6_list: a list of orig_nodes wanting all IPv6 multicast traffic
  * @flags: the flags we have last sent in our mcast tvlv
  * @enabled: whether the multicast tvlv is currently enabled
  * @num_disabled: number of nodes that have no mcast tvlv
  * @num_want_all_unsnoopables: number of nodes wanting unsnoopable IP traffic
+ * @num_want_all_ipv4: counter for items in want_all_ipv4_list
+ * @num_want_all_ipv6: counter for items in want_all_ipv6_list
  * @want_lists_lock: lock for protecting modifications to mcast want lists
  *  (traversals are rcu-locked)
  */
 struct batadv_priv_mcast {
 	struct hlist_head mla_list;
 	struct hlist_head want_all_unsnoopables_list;
+	struct hlist_head want_all_ipv4_list;
+	struct hlist_head want_all_ipv6_list;
 	uint8_t flags;
 	bool enabled;
 	atomic_t num_disabled;
 	atomic_t num_want_all_unsnoopables;
-	/* protects want_all_unsnoopables_list */
+	atomic_t num_want_all_ipv4;
+	atomic_t num_want_all_ipv6;
+	/* protects want_all_{unsnoopables,ipv4,ipv6}_list */
 	spinlock_t want_lists_lock;
 };
 #endif