tipc: support broadcast/replicast configurable for bc-link

Currently, a multicast stream uses either broadcast or replicast as
transmission method, based on the ratio between number of actual
destinations nodes and cluster size.

However, when an L2 interface (e.g., VXLAN) provides pseudo
broadcast support, this becomes very inefficient, as it blindly
replicates multicast packets to all cluster/subnet nodes,
irrespective of whether they host actual target sockets or not.

The TIPC multicast algorithm is able to distinguish real destination
nodes from other nodes, and hence provides a smarter and more
efficient method for transferring multicast messages than
pseudo broadcast can do.

Because of this, we now make it possible for users to force
the broadcast link to permanently switch to using replicast,
irrespective of which capabilities the bearer provides,
or pretend to provide.
Conversely, we also make it possible to force the broadcast link
to always use true broadcast. While maybe less useful in
deployed systems, this may at least be useful for testing the
broadcast algorithm in small clusters.

We retain the current AUTOSELECT ability, i.e., to let the broadcast link
automatically select which algorithm to use, and to switch back and forth
between broadcast and replicast as the ratio between destination
node number and cluster size changes. This remains the default method.

Furthermore, we make it possible to configure the threshold ratio for
such switches. The default ratio is now set to 10%, down from 25% in the
earlier implementation.

Acked-by: Jon Maloy <jon.maloy@ericsson.com>
Signed-off-by: Hoang Le <hoang.h.le@dektech.com.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 7 insertions, 0 deletions

diff --git a/net/tipc/bcast.h b/net/tipc/bcast.h
index 751530ab0c49..37c55e7347a5 100644
--- a/net/tipc/bcast.h
+++ b/net/tipc/bcast.h
@@ -48,6 +48,10 @@ extern const char tipc_bclink_name[];
 
 #define TIPC_METHOD_EXPIRE msecs_to_jiffies(5000)
 
+#define BCLINK_MODE_BCAST  0x1
+#define BCLINK_MODE_RCAST  0x2
+#define BCLINK_MODE_SEL    0x4
+
 struct tipc_nlist {
 	struct list_head list;
 	u32 self;
@@ -92,6 +96,9 @@ int tipc_nl_add_bc_link(struct net *net, struct tipc_nl_msg *msg);
 int tipc_nl_bc_link_set(struct net *net, struct nlattr *attrs[]);
 int tipc_bclink_reset_stats(struct net *net);
 
+u32 tipc_bcast_get_broadcast_mode(struct net *net);
+u32 tipc_bcast_get_broadcast_ratio(struct net *net);
+
 static inline void tipc_bcast_lock(struct net *net)
 {
 	spin_lock_bh(&tipc_net(net)->bclock);