tipc: add new functions for multicast and broadcast distribution

We add a new broadcast link transmit function in bclink.c and a new
receive function in socket.c. The purpose is to move the branching
between external and internal destination down to the link layer,
just as we have done with unicast in earlier commits. We also make
use of the new link-independent fragmentation support that was
introduced in an earlier commit series.

This gives a shorter and simpler code path, and makes it possible
to obtain copy-free buffer delivery to all node local destination
sockets.

The new transmission code is added in parallel with the existing one,
and will be used by the socket multicast send function in the next
commit in this series.

Signed-off-by: Jon Maloy <jon.maloy@ericsson.com>
Reviewed-by: Erik Hugne <erik.hugne@ericsson.com>
Reviewed-by: Ying Xue <ying.xue@windriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/tipc/msg.h b/net/tipc/msg.h
index 7d57434..a15d596 100644
--- a/net/tipc/msg.h
+++ b/net/tipc/msg.h
@@ -744,4 +744,6 @@
 int tipc_msg_build2(struct tipc_msg *mhdr, struct iovec const *iov,
 		    int offset, int dsz, int mtu , struct sk_buff **chain);
 
+struct sk_buff *tipc_msg_reassemble(struct sk_buff *chain);
+
 #endif