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Calimero KNXnet/IP server, a free KNX network server
/*
Calimero 2 - A library for KNX network access
Copyright (c) 2016, 2024 B. Malinowsky
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
Linking this library statically or dynamically with other modules is
making a combined work based on this library. Thus, the terms and
conditions of the GNU General Public License cover the whole
combination.
As a special exception, the copyright holders of this library give you
permission to link this library with independent modules to produce an
executable, regardless of the license terms of these independent
modules, and to copy and distribute the resulting executable under terms
of your choice, provided that you also meet, for each linked independent
module, the terms and conditions of the license of that module. An
independent module is a module which is not derived from or based on
this library. If you modify this library, you may extend this exception
to your version of the library, but you are not obligated to do so. If
you do not wish to do so, delete this exception statement from your
version.
*/
package tuwien.auto.calimero.server.gateway;
import java.net.InetSocketAddress;
import java.time.Duration;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import tuwien.auto.calimero.FrameEvent;
import tuwien.auto.calimero.knxnetip.KNXnetIPConnection;
class ReplayBuffer
{
private static final Logger logger = LoggerFactory.getLogger("calimero.server.gateway.ReplayBuffer");
private record Key(String hostAddress, int port, long timestamp) {
Key(InetSocketAddress remote) {
this(remote.getAddress().getHostAddress(), remote.getPort(), System.currentTimeMillis());
}
}
private final Map connectionToKey = Collections.synchronizedMap(new HashMap<>());
private final Map completedEvent = Collections.synchronizedMap(new HashMap<>());
private static final long maxBufferSize = 350;
private final List buffer = new ArrayList<>();
private final long keepDisruptedConnection; // [ms]
ReplayBuffer(final Duration expireDisruptedConnectionAfter)
{
keepDisruptedConnection = expireDisruptedConnectionAfter.toMillis();
}
public boolean isDisrupted(final KNXnetIPConnection c)
{
return !disruptedCandidates(c).isEmpty();
}
private List disruptedCandidates(final KNXnetIPConnection c)
{
final Key key = new Key(c.getRemoteAddress());
synchronized (connectionToKey) {
final List exactMatch = find(c, key, 2);
if (!exactMatch.isEmpty()) {
logger.info("found exact match for {} in disrupted connections: {}", key, exactMatch);
return exactMatch;
}
final List matchedHosts = find(c, key, 1);
final List closedOnly = new ArrayList<>(matchedHosts);
closedOnly.removeIf(e -> e.getState() != KNXnetIPConnection.CLOSED);
if (!closedOnly.isEmpty()) {
logger.info("found match for {} in closed disrupted connections: {}", key, closedOnly);
return closedOnly;
}
// TODO with the current implementation, the following wrong outcome is possible: using host-matching only,
// a (truly disrupted) connection in open state is initially found, because no new subnet event has
// arrived yet. Hence, that connection is removed from matchedHosts set as it is not missing events,
// therefore, it is not a disrupted candidate.
// A future connect attempt then might match that connection again even though it shouldn't.
// we matched open connections by host, check if any connection is missing events
matchedHosts.removeIf(e -> !isMissingEvents(e));
logger.info("match for {} in open connections with missing events: {}", key, matchedHosts);
return matchedHosts;
}
}
private boolean isMissingEvents(final KNXnetIPConnection c)
{
final Long lastTx = completedEvent.get(c);
if (lastTx == null)
return false;
return lastTx < latestEventCount();
}
// only call iff synchronized on connectionToKey
private List find(final KNXnetIPConnection c, final Key key, final int compare)
{
final List remove = new ArrayList<>();
final List found = new ArrayList<>();
for (final Entry e : connectionToKey.entrySet()) {
final long timestamp = e.getValue().timestamp();
final KNXnetIPConnection conn = e.getKey();
if ((timestamp + keepDisruptedConnection) < System.currentTimeMillis()) {
logger.info("remove expired disrupted connection {}", conn);
remove.add(conn);
}
else if (conn != c) { // we ignore c itself in the entry set, otherwise it would always show up in found
if (compare(e.getValue(), key) == compare)
found.add(conn);
}
}
remove.forEach(this::remove);
return found;
}
public void add(final KNXnetIPConnection c)
{
logger.debug("activate replay buffer for {}", c);
connectionToKey.put(c, new Key(c.getRemoteAddress()));
}
public void recordEvent(final T e)
{
synchronized (buffer) {
while (buffer.size() >= maxBufferSize)
buffer.remove(0);
buffer.add(e);
}
logger.trace("record {} as event '{}'", e, e.id());
}
// returns list of pending events for connection
public Collection replay(final KNXnetIPConnection conn)
{
final List candidates = disruptedCandidates(conn);
if (candidates.isEmpty())
return Collections.emptyList();
synchronized (buffer) {
// we select and terminate a single matching connection with the oldest successful event
long last = Long.MAX_VALUE;
KNXnetIPConnection selected = null;
for (final KNXnetIPConnection c : candidates) {
final long l = completedEvent.get(c);
if (l < last) {
last = l;
selected = c;
}
}
remove(selected);
// pending events
final int fromIndex = findEvent(last) + 1;
final int events = buffer.size() - fromIndex;
if (fromIndex == 0) {
logger.warn("{} has ≥ {} events pending with a buffer size of {}, up to {} events "
+ "will be missing", conn, events, buffer.size(), buffer.get(0).id() - last);
}
logger.info("{} has {} pending events for replay: ({}..{}]", conn, events, last, latestEventCount());
return new ArrayList<>(buffer.subList(fromIndex, buffer.size()));
}
}
// call only iff synchronized on buffer
private int findEvent(final long last)
{
for (int i = 0; i < buffer.size(); i++)
if (buffer.get(i).id() == last)
return i;
return -1;
}
public void completeEvent(final KNXnetIPConnection c, final T e)
{
synchronized (connectionToKey) {
final Key key = connectionToKey.get(c);
if (key == null)
return;
connectionToKey.put(c, new Key(key.hostAddress(), key.port(), System.currentTimeMillis()));
}
completedEvent.put(c, e.id());
logger.debug("{} successfully completed event '{}/{}'", c, e.id(), latestEventCount());
}
private long latestEventCount()
{
synchronized (buffer) {
return buffer.get(buffer.size() - 1).id();
}
}
public void remove(final KNXnetIPConnection c)
{
completedEvent.remove(c);
final Key key = connectionToKey.remove(c);
if (key != null)
logger.trace("remove {} ({})", c, key);
}
// returns 0: no match, 1: key[0] matches to[0], 2: match 1 and key[1] matches to[1]
private static int compare(final Key key, final Key to)
{
if (key.hostAddress().equals(to.hostAddress())) {
if (key.port() == to.port())
return 2;
return 1;
}
return 0;
}
}
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