batman-adv: Add multicast optimization support for bridged setups

So far, the recently added multicast optimizations did not support a configuration where a bridge is on top of the soft-interface (e.g. bat0).

Now the Linux bridge code is able to provide us with the missing bits:

Multicast Listeners: The bridge hands us a list of multicast listeners it has detected behind the bridge which we will announce through the mesh via the translation table, allowing other nodes to direct multicast packets to these clients behind the bridge even with enabled multicast optimizations.

Queriers: The bridge informs us whether there is a selected IGMP or MLD querier behind the bridge or if there is no querier at all. In these cases we need all according IPv4 or IPv6 multicast traffic directed to us.

These two parts together allow us to serve all multicast listeners with IPv6 link-local multicast packets even when bridges are involved and our multicast optimizations enabled.

---
Changes in v3:
* Removed "RFC" tag in title again: The stubs and new export are upstream in net-next and therefore going to be included in 3.17
* Added some debug output:
* Two warning messages:

    -> Old kernel version or no bridge IGMP/MLD snooping compiled
  * New batman-adv log-level "mcast":
    -> Logging mcast flag changes

(a third debugging facility, a new table for debugfs for a global
mcast flag overview will be added in a separate patch later as discussed with Simon)

Changes in v2:
* fetching local (= on this same kernel) multicast listeners from the bridge instead of the bat0 interface if a bridge is present
- just like ip addresses and routes should be used from br0, the same goes for multicast listeners
* beautification of batadv_mcast_mla_br_addr_cpy(), now using already present functions from the kernel instead of own, hackish approach
* changed names of some goto-labels (not using "skip" anymore)
* using new, third bridge multicast export (because this export is not upstream yet, I've added the "RFC" in the title):
br_multicast_has_querier_anywhere()
* adding compat stubs for two bridge multicast exports, to make batman-adv compile- and usable even if a 3.16 kernel was compiled without bridge code - the stubs are supposed to be upstream in the bridge code in 3.17 (therefore just 'compat')
* updated kerneldocs for batadv_mcast_mla_bridge_get() and batadv_mcast_mla_softif_get()
* The two sentences in the commit message starting with "Queriers: ..." were slightly modified to include the third bridge multicast export

 compat.c    |   39 ++++++++++++
 compat.h    |   32 ++++++++++
 main.h      |    6 +-
 multicast.c |  193 +++++++++++++++++++++++++++++++++++++++++++++++++++++------
 4 files changed, 251 insertions(+), 19 deletions(-)

index 3dbf9d2..31546f5 100644
@@ -109,3 +109,42 @@ void batadv_free_rcu_tvlv_handler(struct rcu_head *rcu)
 }
 
 #endif /* < KERNEL_VERSION(3, 0, 0) */
+
+#if LINUX_VERSION_CODE < KERNEL_VERSION(3, 16, 0)
+
+int br_multicast_list_adjacent(struct net_device *dev,
+			       struct list_head *br_ip_list)
+{
+	return 0;
+}
+
+bool br_multicast_has_querier_adjacent(struct net_device *dev, int proto)
+{
+	return false;
+}
+
+#endif /* < KERNEL_VERSION(3, 16, 0) */
+
+#if LINUX_VERSION_CODE < KERNEL_VERSION(3, 17, 0)
+
+bool br_multicast_has_querier_anywhere(struct net_device *dev, int proto)
+{
+	pr_warn_once("Old kernel detected (< 3.17) - multicast optimizations disabled\n");
+
+	return false;
+}
+
+#if !(IS_ENABLED(CONFIG_BRIDGE) && IS_ENABLED(CONFIG_BRIDGE_IGMP_SNOOPING))
+int br_multicast_list_adjacent(struct net_device *dev,
+			       struct list_head *br_ip_list)
+{
+	return 0;
+}
+
+bool br_multicast_has_querier_adjacent(struct net_device *dev, int proto)
+{
+	return false;
+}
+#endif
+
+#endif /* < KERNEL_VERSION(3, 17, 0) */

index ed5b815..14de948 100644
@@ -240,6 +240,12 @@ static inline void skb_reset_mac_len(struct sk_buff *skb)
 
 #endif /* < KERNEL_VERSION(3, 0, 0) */
 
+#if LINUX_VERSION_CODE < KERNEL_VERSION(3, 1, 0)
+
+#define IS_ENABLED(x) defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
+
+#endif /* < KERNEL_VERSION(3, 1, 0) */
+
 #if LINUX_VERSION_CODE < KERNEL_VERSION(3, 3, 0)
 
 #define batadv_interface_add_vid(x, y, z) \

@@ -444,6 +450,32 @@ static int __batadv_interface_kill_vid(struct net_device *dev, __be16 proto,\
 
 #define pskb_copy_for_clone pskb_copy
 
+int br_multicast_list_adjacent(struct net_device *dev,
+			       struct list_head *br_ip_list);
+bool br_multicast_has_querier_adjacent(struct net_device *dev, int proto);
+
+struct br_ip {
+	union {
+		__be32  ip4;
+#if IS_ENABLED(CONFIG_IPV6)
+		struct in6_addr ip6;
+#endif
+	} u;
+	__be16          proto;
+	__u16           vid;
+};
+
+struct br_ip_list {
+	struct list_head list;
+	struct br_ip addr;
+};
+
 #endif /* < KERNEL_VERSION(3, 16, 0) */
 
+#if LINUX_VERSION_CODE < KERNEL_VERSION(3, 17, 0)
+
+bool br_multicast_has_querier_anywhere(struct net_device *dev, int proto);
+
+#endif /* < KERNEL_VERSION(3, 17, 0) */
+
 #endif /* _NET_BATMAN_ADV_COMPAT_H_ */

index 4bb500b..1e1e000 100644
@@ -169,6 +169,7 @@ enum batadv_uev_type {
 #include <linux/netdevice.h>	/* netdevice */
 #include <linux/etherdevice.h>  /* ethernet address classification */
 #include <linux/if_ether.h>	/* ethernet header */
+#include <linux/if_bridge.h>	/* bridge / multicast-snooping communication */
 #include <linux/poll.h>		/* poll_table */
 #include <linux/kthread.h>	/* kernel threads */
 #include <linux/pkt_sched.h>	/* schedule types */

@@ -177,6 +178,7 @@ enum batadv_uev_type {
 #include <linux/slab.h>
 #include <net/sock.h>		/* struct sock */
 #include <net/addrconf.h>	/* ipv6 address stuff */
+#include <net/ip.h>
 #include <linux/ip.h>
 #include <net/rtnetlink.h>
 #include <linux/jiffies.h>

@@ -223,6 +225,7 @@ __be32 batadv_skb_crc32(struct sk_buff *skb, u8 *payload_ptr);
  * @BATADV_DBG_BLA: bridge loop avoidance messages
  * @BATADV_DBG_DAT: ARP snooping and DAT related messages
  * @BATADV_DBG_NC: network coding related messages
+ * @BATADV_DBG_MCAST: multicast related messages
  * @BATADV_DBG_ALL: the union of all the above log levels
  */
 enum batadv_dbg_level {

@@ -232,7 +235,8 @@ enum batadv_dbg_level {
 	BATADV_DBG_BLA    = BIT(3),
 	BATADV_DBG_DAT    = BIT(4),
 	BATADV_DBG_NC	  = BIT(5),
-	BATADV_DBG_ALL    = 63,
+	BATADV_DBG_MCAST  = BIT(6),
+	BATADV_DBG_ALL    = 127,
 };
 
 #ifdef CONFIG_BATMAN_ADV_DEBUG

1.7.10.4

I've tested the previous version (PATCH RFC v2), but since the changes are minimal you can add for this patch:

The test included 3 hosts bridged together

host1 ---[LAN]--- host2 ---[Mesh]--- host 3

with the recent net-next kernel and patches as sent by Linus previously. I was using his listener tool [1] which creates a multicast socket on the bridged-in host 1, and enabled the multicast querier [2] on host2 or host3 (only one at a time). Then I could verify that the desired multicast MAC address showed up in batctl tl on host 2, so the announcement, snooping and list retrieval of batman-adv for the multicast address worked correctly. Also the "bridge" tool of iproute2 proved useful, "bridge mdb show" gives us the list of snooped multicast listeners on the bridge.

Linus, please don't forget the batctl patch since you've added a loglevel here. I'm also looking forward to the debugfs files patch, which would make monitoring the status of the multicast operation a lot easier. :)

Cheers,
Simon

[1] https://github.com/T-X/sm-listener
[2] echo 1 > /sys/class/net/br0/bridge/multicast_querier