tipc: introduce replicast as transport option for multicast

TIPC multicast messages are currently carried over a reliable
'broadcast link', making use of the underlying media's ability to
transport packets as L2 broadcast or IP multicast to all nodes in
the cluster.

When the used bearer is lacking that ability, we can instead emulate
the broadcast service by replicating and sending the packets over as
many unicast links as needed to reach all identified destinations.
We now introduce a new TIPC link-level 'replicast' service that does
this.

Reviewed-by: Parthasarathy Bhuvaragan <parthasarathy.bhuvaragan@ericsson.com>
Acked-by: Ying Xue <ying.xue@windriver.com>
Signed-off-by: Jon Maloy <jon.maloy@ericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 82 insertions, 23 deletions

diff --git a/net/tipc/bcast.c b/net/tipc/bcast.c
index 412d3351abb7..672e6ef93cab 100644
--- a/net/tipc/bcast.c
+++ b/net/tipc/bcast.c
@@ -70,7 +70,7 @@ static struct tipc_bc_base *tipc_bc_base(struct net *net)
 
 int tipc_bcast_get_mtu(struct net *net)
 {
-	return tipc_link_mtu(tipc_bc_sndlink(net));
+	return tipc_link_mtu(tipc_bc_sndlink(net)) - INT_H_SIZE;
 }
 
 /* tipc_bcbase_select_primary(): find a bearer with links to all destinations,
@@ -175,42 +175,101 @@ static void tipc_bcbase_xmit(struct net *net, struct sk_buff_head *xmitq)
 	__skb_queue_purge(&_xmitq);
 }
 
-/* tipc_bcast_xmit - deliver buffer chain to all nodes in cluster
- *                    and to identified node local sockets
+/* tipc_bcast_xmit - broadcast the buffer chain to all external nodes
  * @net: the applicable net namespace
- * @list: chain of buffers containing message
+ * @pkts: chain of buffers containing message
+ * @cong_link_cnt: set to 1 if broadcast link is congested, otherwise 0
  * Consumes the buffer chain.
- * Returns 0 if success, otherwise errno: -ELINKCONG,-EHOSTUNREACH,-EMSGSIZE
+ * Returns 0 if success, otherwise errno: -EHOSTUNREACH,-EMSGSIZE
  */
-int tipc_bcast_xmit(struct net *net, struct sk_buff_head *list)
+static int tipc_bcast_xmit(struct net *net, struct sk_buff_head *pkts,
+			   u16 *cong_link_cnt)
 {
 	struct tipc_link *l = tipc_bc_sndlink(net);
-	struct sk_buff_head xmitq, inputq, rcvq;
+	struct sk_buff_head xmitq;
 	int rc = 0;
 
-	__skb_queue_head_init(&rcvq);
 	__skb_queue_head_init(&xmitq);
-	skb_queue_head_init(&inputq);
-
-	/* Prepare message clone for local node */
-	if (unlikely(!tipc_msg_reassemble(list, &rcvq)))
-		return -EHOSTUNREACH;
-
 	tipc_bcast_lock(net);
 	if (tipc_link_bc_peers(l))
-		rc = tipc_link_xmit(l, list, &xmitq);
+		rc = tipc_link_xmit(l, pkts, &xmitq);
 	tipc_bcast_unlock(net);
+	tipc_bcbase_xmit(net, &xmitq);
+	__skb_queue_purge(pkts);
+	if (rc == -ELINKCONG) {
+		*cong_link_cnt = 1;
+		rc = 0;
+	}
+	return rc;
+}
 
-	/* Don't send to local node if adding to link failed */
-	if (unlikely(rc && (rc != -ELINKCONG))) {
-		__skb_queue_purge(&rcvq);
-		return rc;
+/* tipc_rcast_xmit - replicate and send a message to given destination nodes
+ * @net: the applicable net namespace
+ * @pkts: chain of buffers containing message
+ * @dests: list of destination nodes
+ * @cong_link_cnt: returns number of congested links
+ * @cong_links: returns identities of congested links
+ * Returns 0 if success, otherwise errno
+ */
+static int tipc_rcast_xmit(struct net *net, struct sk_buff_head *pkts,
+			   struct tipc_nlist *dests, u16 *cong_link_cnt)
+{
+	struct sk_buff_head _pkts;
+	struct u32_item *n, *tmp;
+	u32 dst, selector;
+
+	selector = msg_link_selector(buf_msg(skb_peek(pkts)));
+	__skb_queue_head_init(&_pkts);
+
+	list_for_each_entry_safe(n, tmp, &dests->list, list) {
+		dst = n->value;
+		if (!tipc_msg_pskb_copy(dst, pkts, &_pkts))
+			return -ENOMEM;
+
+		/* Any other return value than -ELINKCONG is ignored */
+		if (tipc_node_xmit(net, &_pkts, dst, selector) == -ELINKCONG)
+			(*cong_link_cnt)++;
 	}
+	return 0;
+}
 
-	/* Broadcast to all nodes, inluding local node */
-	tipc_bcbase_xmit(net, &xmitq);
-	tipc_sk_mcast_rcv(net, &rcvq, &inputq);
-	__skb_queue_purge(list);
+/* tipc_mcast_xmit - deliver message to indicated destination nodes
+ *                   and to identified node local sockets
+ * @net: the applicable net namespace
+ * @pkts: chain of buffers containing message
+ * @dests: destination nodes for message. Not consumed.
+ * @cong_link_cnt: returns number of encountered congested destination links
+ * @cong_links: returns identities of congested links
+ * Consumes buffer chain.
+ * Returns 0 if success, otherwise errno
+ */
+int tipc_mcast_xmit(struct net *net, struct sk_buff_head *pkts,
+		    struct tipc_nlist *dests, u16 *cong_link_cnt)
+{
+	struct tipc_bc_base *bb = tipc_bc_base(net);
+	struct sk_buff_head inputq, localq;
+	int rc = 0;
+
+	skb_queue_head_init(&inputq);
+	skb_queue_head_init(&localq);
+
+	/* Clone packets before they are consumed by next call */
+	if (dests->local && !tipc_msg_reassemble(pkts, &localq)) {
+		rc = -ENOMEM;
+		goto exit;
+	}
+
+	if (dests->remote) {
+		if (!bb->bcast_support)
+			rc = tipc_rcast_xmit(net, pkts, dests, cong_link_cnt);
+		else
+			rc = tipc_bcast_xmit(net, pkts, cong_link_cnt);
+	}
+
+	if (dests->local)
+		tipc_sk_mcast_rcv(net, &localq, &inputq);
+exit:
+	__skb_queue_purge(pkts);
 	return rc;
 }