Commit fa368826 authored Nov 02, 2017 by Jon Maloy Committed by David S. Miller Nov 03, 2017

tipc: eliminate unnecessary probing

The neighbor monitor employs a threshold, default set to 32 peer nodes,
where it activates the "Overlapping Neighbor Monitoring" algorithm.
Below that threshold, monitoring is full-mesh, and no "domain records"
are passed between the nodes.

Because of this, a node never received a peer's ack that it has received
the most recent update of the own domain. Hence, the field 'acked_gen'
in struct tipc_monitor_state remains permamently at zero, whereas the
own domain generation is incremented for each added or removed peer.

This has the effect that the function tipc_mon_get_state() always sets
the field 'probing' in struct tipc_monitor_state true, again leading the
tipc_link_timeout() of the link in question to always send out a probe,
even when link->silent_intv_count is zero.

This is functionally harmless, but leads to some unncessary probing,
which can easily be eliminated by setting the 'probing' field of the
said struct correctly in such cases.

At the same time, we explictly invalidate the sent domain records when
the algorithm is not activated. This will eliminate any risk that an
invalid domain record might be inadverently accepted by the peer.

Signed-off-by: Jon Maloy <jon.maloy@ericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 4bb1b116

net/tipc/monitor.c

+10 −1

Original line number	Original line	Diff line number	Diff line
	@@ -530,8 +530,11 @@ void tipc_mon_prep(struct net net, void data, int *dlen,
	u16 gen = mon->dom_gen;		u16 gen = mon->dom_gen;
	u16 len;		u16 len;

	if (!tipc_mon_is_active(net, mon))		/* Send invalid record if not active */
			if (!tipc_mon_is_active(net, mon)) {
			dom->len = 0;
	return;		return;
			}

	/* Send only a dummy record with ack if peer has acked our last sent */		/* Send only a dummy record with ack if peer has acked our last sent */
	if (likely(state->acked_gen == gen)) {		if (likely(state->acked_gen == gen)) {
	@@ -559,6 +562,12 @@ void tipc_mon_get_state(struct net *net, u32 addr,
	struct tipc_monitor *mon = tipc_monitor(net, bearer_id);		struct tipc_monitor *mon = tipc_monitor(net, bearer_id);
	struct tipc_peer *peer;		struct tipc_peer *peer;

			if (!tipc_mon_is_active(net, mon)) {
			state->probing = false;
			state->monitoring = true;
			return;
			}

	/* Used cached state if table has not changed */		/* Used cached state if table has not changed */
	if (!state->probing &&		if (!state->probing &&
	(state->list_gen == mon->list_gen) &&		(state->list_gen == mon->list_gen) &&

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