bgp/rib-impl/src/main/java/org/opendaylight/protocol/bgp/rib/impl/BGPSessionImpl.java

   1 /*
   2  * Copyright (c) 2013 Cisco Systems, Inc. and others.  All rights reserved.
   3  *
   4  * This program and the accompanying materials are made available under the
   5  * terms of the Eclipse Public License v1.0 which accompanies this distribution,
   6  * and is available at http://www.eclipse.org/legal/epl-v10.html
   7  */
   8 package org.opendaylight.protocol.bgp.rib.impl;
   9
  10 import static java.util.Objects.requireNonNull;
  11
  12 import com.google.common.annotations.VisibleForTesting;
  13 import com.google.common.base.MoreObjects;
  14 import com.google.common.base.MoreObjects.ToStringHelper;
  15 import com.google.common.base.Preconditions;
  16 import com.google.common.collect.ImmutableSet;
  17 import io.netty.buffer.ByteBufUtil;
  18 import io.netty.channel.Channel;
  19 import io.netty.channel.ChannelFuture;
  20 import io.netty.channel.ChannelFutureListener;
  21 import io.netty.channel.ChannelHandlerContext;
  22 import io.netty.channel.SimpleChannelInboundHandler;
  23 import java.io.IOException;
  24 import java.nio.channels.NonWritableChannelException;
  25 import java.util.ArrayList;
  26 import java.util.Date;
  27 import java.util.HashSet;
  28 import java.util.List;
  29 import java.util.Optional;
  30 import java.util.Set;
  31 import java.util.concurrent.TimeUnit;
  32 import java.util.function.Function;
  33 import javax.annotation.concurrent.GuardedBy;
  34 import org.opendaylight.protocol.bgp.parser.AsNumberUtil;
  35 import org.opendaylight.protocol.bgp.parser.BGPDocumentedException;
  36 import org.opendaylight.protocol.bgp.parser.BGPError;
  37 import org.opendaylight.protocol.bgp.parser.BgpExtendedMessageUtil;
  38 import org.opendaylight.protocol.bgp.parser.BgpTableTypeImpl;
  39 import org.opendaylight.protocol.bgp.parser.GracefulRestartUtil;
  40 import org.opendaylight.protocol.bgp.parser.spi.MultiPathSupport;
  41 import org.opendaylight.protocol.bgp.parser.spi.PeerConstraint;
  42 import org.opendaylight.protocol.bgp.parser.spi.pojo.MultiPathSupportImpl;
  43 import org.opendaylight.protocol.bgp.rib.impl.spi.BGPMessagesListener;
  44 import org.opendaylight.protocol.bgp.rib.impl.spi.BGPPeerRegistry;
  45 import org.opendaylight.protocol.bgp.rib.impl.spi.BGPSessionPreferences;
  46 import org.opendaylight.protocol.bgp.rib.impl.state.BGPSessionStateImpl;
  47 import org.opendaylight.protocol.bgp.rib.impl.state.BGPSessionStateProvider;
  48 import org.opendaylight.protocol.bgp.rib.spi.BGPSession;
  49 import org.opendaylight.protocol.bgp.rib.spi.BGPSessionListener;
  50 import org.opendaylight.protocol.bgp.rib.spi.BGPTerminationReason;
  51 import org.opendaylight.protocol.bgp.rib.spi.State;
  52 import org.opendaylight.protocol.bgp.rib.spi.state.BGPSessionState;
  53 import org.opendaylight.protocol.bgp.rib.spi.state.BGPTimersState;
  54 import org.opendaylight.protocol.bgp.rib.spi.state.BGPTransportState;
  55 import org.opendaylight.yang.gen.v1.urn.ietf.params.xml.ns.yang.ietf.inet.types.rev130715.AsNumber;
  56 import org.opendaylight.yang.gen.v1.urn.ietf.params.xml.ns.yang.ietf.inet.types.rev130715.Ipv4Address;
  57 import org.opendaylight.yang.gen.v1.urn.opendaylight.params.xml.ns.yang.bgp.message.rev180329.Keepalive;
  58 import org.opendaylight.yang.gen.v1.urn.opendaylight.params.xml.ns.yang.bgp.message.rev180329.KeepaliveBuilder;
  59 import org.opendaylight.yang.gen.v1.urn.opendaylight.params.xml.ns.yang.bgp.message.rev180329.Notify;
  60 import org.opendaylight.yang.gen.v1.urn.opendaylight.params.xml.ns.yang.bgp.message.rev180329.NotifyBuilder;
  61 import org.opendaylight.yang.gen.v1.urn.opendaylight.params.xml.ns.yang.bgp.message.rev180329.Open;
  62 import org.opendaylight.yang.gen.v1.urn.opendaylight.params.xml.ns.yang.bgp.message.rev180329.Update;
  63 import org.opendaylight.yang.gen.v1.urn.opendaylight.params.xml.ns.yang.bgp.message.rev180329.open.message.BgpParameters;
  64 import org.opendaylight.yang.gen.v1.urn.opendaylight.params.xml.ns.yang.bgp.message.rev180329.open.message.bgp.parameters.OptionalCapabilities;
  65 import org.opendaylight.yang.gen.v1.urn.opendaylight.params.xml.ns.yang.bgp.message.rev180329.open.message.bgp.parameters.optional.capabilities.CParameters;
  66 import org.opendaylight.yang.gen.v1.urn.opendaylight.params.xml.ns.yang.bgp.multiprotocol.rev180329.BgpTableType;
  67 import org.opendaylight.yang.gen.v1.urn.opendaylight.params.xml.ns.yang.bgp.multiprotocol.rev180329.CParameters1;
  68 import org.opendaylight.yang.gen.v1.urn.opendaylight.params.xml.ns.yang.bgp.multiprotocol.rev180329.MpCapabilities;
  69 import org.opendaylight.yang.gen.v1.urn.opendaylight.params.xml.ns.yang.bgp.multiprotocol.rev180329.RouteRefresh;
  70 import org.opendaylight.yang.gen.v1.urn.opendaylight.params.xml.ns.yang.bgp.multiprotocol.rev180329.mp.capabilities.AddPathCapability;
  71 import org.opendaylight.yang.gen.v1.urn.opendaylight.params.xml.ns.yang.bgp.multiprotocol.rev180329.mp.capabilities.GracefulRestartCapability;
  72 import org.opendaylight.yang.gen.v1.urn.opendaylight.params.xml.ns.yang.bgp.multiprotocol.rev180329.mp.capabilities.LlGracefulRestartCapability;
  73 import org.opendaylight.yang.gen.v1.urn.opendaylight.params.xml.ns.yang.bgp.multiprotocol.rev180329.mp.capabilities.MultiprotocolCapability;
  74 import org.opendaylight.yang.gen.v1.urn.opendaylight.params.xml.ns.yang.bgp.multiprotocol.rev180329.mp.capabilities.add.path.capability.AddressFamilies;
  75 import org.opendaylight.yang.gen.v1.urn.opendaylight.params.xml.ns.yang.bgp.rib.rev180329.rib.TablesKey;
  76 import org.opendaylight.yangtools.yang.binding.ChildOf;
  77 import org.opendaylight.yangtools.yang.binding.Notification;
  78 import org.slf4j.Logger;
  79 import org.slf4j.LoggerFactory;
  80
  81 @VisibleForTesting
  82 public class BGPSessionImpl extends SimpleChannelInboundHandler<Notification> implements BGPSession,
  83         BGPSessionStateProvider, AutoCloseable {
  84
  85     private static final Logger LOG = LoggerFactory.getLogger(BGPSessionImpl.class);
  86
  87     private static final Notification KEEP_ALIVE = new KeepaliveBuilder().build();
  88
  89     private static final int KA_TO_DEADTIMER_RATIO = 3;
  90
  91     private static final String EXTENDED_MSG_DECODER = "EXTENDED_MSG_DECODER";
  92
  93     static final String END_OF_INPUT = "End of input detected. Close the session.";
  94
  95     /**
  96      * System.nanoTime value about when was sent the last message.
  97      */
  98     @VisibleForTesting
  99     private long lastMessageSentAt;
 100
 101     /**
 102      * System.nanoTime value about when was received the last message.
 103      */
 104     private long lastMessageReceivedAt;
 105
 106     private final BGPSessionListener listener;
 107
 108     private final BGPSynchronization sync;
 109
 110     private int kaCounter = 0;
 111
 112     private final Channel channel;
 113
 114     @GuardedBy("this")
 115     private State state = State.OPEN_CONFIRM;
 116
 117     private final Set<BgpTableType> tableTypes;
 118     private final List<AddressFamilies> addPathTypes;
 119     private final int holdTimerValue;
 120     private final int keepAlive;
 121     private final AsNumber asNumber;
 122     private final Ipv4Address bgpId;
 123     private final BGPPeerRegistry peerRegistry;
 124     private final ChannelOutputLimiter limiter;
 125     private final BGPSessionStateImpl sessionState;
 126     private final GracefulRestartCapability gracefulCapability;
 127     private final LlGracefulRestartCapability llGracefulCapability;
 128     private boolean terminationReasonNotified;
 129
 130     public BGPSessionImpl(final BGPSessionListener listener, final Channel channel, final Open remoteOpen,
 131             final BGPSessionPreferences localPreferences, final BGPPeerRegistry peerRegistry) {
 132         this(listener, channel, remoteOpen, localPreferences.getHoldTime(), peerRegistry);
 133     }
 134
 135     public BGPSessionImpl(final BGPSessionListener listener, final Channel channel, final Open remoteOpen,
 136             final int localHoldTimer, final BGPPeerRegistry peerRegistry) {
 137         this.listener = requireNonNull(listener);
 138         this.channel = requireNonNull(channel);
 139         this.limiter = new ChannelOutputLimiter(this);
 140         this.channel.pipeline().addLast(this.limiter);
 141         this.holdTimerValue = remoteOpen.getHoldTimer() < localHoldTimer ? remoteOpen.getHoldTimer() : localHoldTimer;
 142         LOG.info("BGP HoldTimer new value: {}", this.holdTimerValue);
 143         this.keepAlive = this.holdTimerValue / KA_TO_DEADTIMER_RATIO;
 144         this.asNumber = AsNumberUtil.advertizedAsNumber(remoteOpen);
 145         this.peerRegistry = peerRegistry;
 146         this.sessionState = new BGPSessionStateImpl();
 147
 148         final Set<TablesKey> tts = new HashSet<>();
 149         final Set<BgpTableType> tats = new HashSet<>();
 150         final List<AddressFamilies> addPathCapabilitiesList = new ArrayList<>();
 151         final List<BgpParameters> bgpParameters = remoteOpen.getBgpParameters();
 152         if (bgpParameters != null) {
 153             for (final BgpParameters param : bgpParameters) {
 154                 for (final OptionalCapabilities optCapa : param.getOptionalCapabilities()) {
 155                     final CParameters cParam = optCapa.getCParameters();
 156                     final CParameters1 cParam1 = cParam.augmentation(CParameters1.class);
 157                     if (cParam1 != null) {
 158                         final MultiprotocolCapability multi = cParam1.getMultiprotocolCapability();
 159                         if (multi != null) {
 160                             final TablesKey tt = new TablesKey(multi.getAfi(), multi.getSafi());
 161                             LOG.trace("Added table type to sync {}", tt);
 162                             tts.add(tt);
 163                             tats.add(new BgpTableTypeImpl(tt.getAfi(), tt.getSafi()));
 164                         } else {
 165                             final AddPathCapability addPathCap = cParam1.getAddPathCapability();
 166                             if (addPathCap != null) {
 167                                 addPathCapabilitiesList.addAll(addPathCap.getAddressFamilies());
 168                             }
 169                         }
 170                     }
 171                 }
 172             }
 173             this.gracefulCapability = findSingleCapability(bgpParameters, "Graceful Restart",
 174                 CParameters1::getGracefulRestartCapability).orElse(GracefulRestartUtil.EMPTY_GR_CAPABILITY);
 175             this.llGracefulCapability = findSingleCapability(bgpParameters, "Long-lived Graceful Restart",
 176                 CParameters1::getLlGracefulRestartCapability).orElse(GracefulRestartUtil.EMPTY_LLGR_CAPABILITY);
 177         } else {
 178             this.gracefulCapability = GracefulRestartUtil.EMPTY_GR_CAPABILITY;
 179             this.llGracefulCapability = GracefulRestartUtil.EMPTY_LLGR_CAPABILITY;
 180         }
 181
 182         this.sync = new BGPSynchronization(this.listener, tts);
 183         this.tableTypes = tats;
 184         this.addPathTypes = addPathCapabilitiesList;
 185
 186         if (!this.addPathTypes.isEmpty()) {
 187             addDecoderConstraint(MultiPathSupport.class,
 188                 MultiPathSupportImpl.createParserMultiPathSupport(this.addPathTypes));
 189         }
 190
 191         if (this.holdTimerValue != 0) {
 192             channel.eventLoop().schedule(this::handleHoldTimer, this.holdTimerValue, TimeUnit.SECONDS);
 193             channel.eventLoop().schedule(this::handleKeepaliveTimer, this.keepAlive, TimeUnit.SECONDS);
 194         }
 195         this.bgpId = remoteOpen.getBgpIdentifier();
 196         this.sessionState.advertizeCapabilities(this.holdTimerValue, channel.remoteAddress(), channel.localAddress(),
 197                 this.tableTypes, bgpParameters);
 198     }
 199
 200     private static <T extends ChildOf<MpCapabilities>> Optional<T> findSingleCapability(
 201             final List<BgpParameters> bgpParameters, final String name, final Function<CParameters1, T> extractor) {
 202         final List<T> found = new ArrayList<>(1);
 203         for (BgpParameters bgpParams : bgpParameters) {
 204             for (OptionalCapabilities optCapability : bgpParams.nonnullOptionalCapabilities()) {
 205                 final CParameters cparam = optCapability.getCParameters();
 206                 if (cparam != null) {
 207                     final CParameters1 augment = cparam.augmentation(CParameters1.class);
 208                     if (augment != null) {
 209                         final T capa = extractor.apply(augment);
 210                         if (capa != null) {
 211                             found.add(capa);
 212                         }
 213                     }
 214                 }
 215             }
 216         }
 217
 218         final Set<T> set = ImmutableSet.copyOf(found);
 219         switch (set.size()) {
 220             case 0:
 221                 LOG.debug("{} capability not advertised.", name);
 222                 return Optional.empty();
 223             case 1:
 224                 return Optional.of(found.get(0));
 225             default:
 226                 LOG.warn("Multiple instances of {} capability advertised: {}, ignoring.", name, set);
 227                 return Optional.empty();
 228         }
 229     }
 230
 231     /**
 232      * Set the extend message coder for current channel.
 233      * The reason for separating this part from constructor is, in #channel.pipeline().replace(..), the
 234      * invokeChannelRead() will be invoked after the original message coder handler got removed. And there
 235      * is chance that before the session instance is fully initiated (constructor returns), a KeepAlive
 236      * message arrived already in the channel buffer. Thus #AbstractBGPSessionNegotiator.handleMessage(..)
 237      * gets invoked again and a deadlock is caused.  A BGP final state machine error will happen as BGP
 238      * negotiator is still in OPEN_SENT state as the session constructor hasn't returned yet.
 239      */
 240     public synchronized void setChannelExtMsgCoder(final Open remoteOpen) {
 241         final boolean enableExMess = BgpExtendedMessageUtil.advertizedBgpExtendedMessageCapability(remoteOpen);
 242         if (enableExMess) {
 243             this.channel.pipeline().replace(BGPMessageHeaderDecoder.class, EXTENDED_MSG_DECODER,
 244                     BGPMessageHeaderDecoder.getExtendedBGPMessageHeaderDecoder());
 245         }
 246     }
 247
 248     @Override
 249     public synchronized void close() {
 250         if (this.state != State.IDLE) {
 251             if (!this.terminationReasonNotified) {
 252                 this.writeAndFlush(new NotifyBuilder().setErrorCode(BGPError.CEASE.getCode())
 253                         .setErrorSubcode(BGPError.CEASE.getSubcode()).build());
 254             }
 255             this.closeWithoutMessage();
 256         }
 257     }
 258
 259     /**
 260      * Handles incoming message based on their type.
 261      *
 262      * @param msg incoming message
 263      */
 264     synchronized void handleMessage(final Notification msg) {
 265         if (this.state == State.IDLE) {
 266             return;
 267         }
 268         try {
 269             // Update last reception time
 270             this.lastMessageReceivedAt = System.nanoTime();
 271
 272             if (msg instanceof Open) {
 273                 // Open messages should not be present here
 274                 this.terminate(new BGPDocumentedException(null, BGPError.FSM_ERROR));
 275             } else if (msg instanceof Notify) {
 276                 final Notify notify = (Notify) msg;
 277                 // Notifications are handled internally
 278                 LOG.info("Session closed because Notification message received: {} / {}, data={}",
 279                         notify.getErrorCode(),
 280                         notify.getErrorSubcode(),
 281                         notify.getData() != null ? ByteBufUtil.hexDump(notify.getData()) : null);
 282                 notifyTerminationReasonAndCloseWithoutMessage(notify.getErrorCode(), notify.getErrorSubcode());
 283             } else if (msg instanceof Keepalive) {
 284                 // Keepalives are handled internally
 285                 LOG.trace("Received KeepAlive message.");
 286                 this.kaCounter++;
 287                 if (this.kaCounter >= 2) {
 288                     this.sync.kaReceived();
 289                 }
 290             } else if (msg instanceof RouteRefresh) {
 291                 this.listener.onMessage(this, msg);
 292             } else if (msg instanceof Update) {
 293                 this.listener.onMessage(this, msg);
 294                 this.sync.updReceived((Update) msg);
 295             } else {
 296                 LOG.warn("Ignoring unhandled message: {}.", msg.getClass());
 297             }
 298
 299             this.sessionState.messageReceived(msg);
 300         } catch (final BGPDocumentedException e) {
 301             this.terminate(e);
 302         }
 303     }
 304
 305     private synchronized void notifyTerminationReasonAndCloseWithoutMessage(
 306             final Short errorCode,
 307             final Short errorSubcode) {
 308         this.terminationReasonNotified = true;
 309         this.closeWithoutMessage();
 310         this.listener.onSessionTerminated(this, new BGPTerminationReason(
 311                 BGPError.forValue(errorCode, errorSubcode)));
 312     }
 313
 314     synchronized void endOfInput() {
 315         if (this.state == State.UP) {
 316             LOG.info(END_OF_INPUT);
 317             this.listener.onSessionDown(this, new IOException(END_OF_INPUT));
 318         }
 319     }
 320
 321     @GuardedBy("this")
 322     private ChannelFuture writeEpilogue(final ChannelFuture future, final Notification msg) {
 323         future.addListener((ChannelFutureListener) f -> {
 324             if (!f.isSuccess()) {
 325                 LOG.warn("Failed to send message {} to socket {}", msg, BGPSessionImpl.this.channel, f.cause());
 326             } else {
 327                 LOG.trace("Message {} sent to socket {}", msg, BGPSessionImpl.this.channel);
 328             }
 329         });
 330         this.lastMessageSentAt = System.nanoTime();
 331         this.sessionState.messageSent(msg);
 332         return future;
 333     }
 334
 335     void flush() {
 336         this.channel.flush();
 337     }
 338
 339     synchronized void write(final Notification msg) {
 340         try {
 341             writeEpilogue(this.channel.write(msg), msg);
 342         } catch (final Exception e) {
 343             LOG.warn("Message {} was not sent.", msg, e);
 344         }
 345     }
 346
 347     synchronized ChannelFuture writeAndFlush(final Notification msg) {
 348         if (isWritable()) {
 349             return writeEpilogue(this.channel.writeAndFlush(msg), msg);
 350         }
 351         return this.channel.newFailedFuture(new NonWritableChannelException());
 352     }
 353
 354     @Override
 355     public synchronized void closeWithoutMessage() {
 356         if (this.state == State.IDLE) {
 357             return;
 358         }
 359         LOG.info("Closing session: {}", this);
 360         this.channel.close().addListener((ChannelFutureListener) future
 361             -> Preconditions.checkArgument(future.isSuccess(), "Channel failed to close: %s", future.cause()));
 362         this.state = State.IDLE;
 363         removePeerSession();
 364         this.sessionState.setSessionState(this.state);
 365     }
 366
 367     /**
 368      * Closes BGP session from the parent with given reason. A message needs to be sent, but parent doesn't have to be
 369      * modified, because he initiated the closing. (To prevent concurrent modification exception).
 370      *
 371      * @param e BGPDocumentedException
 372      */
 373     @VisibleForTesting
 374     synchronized void terminate(final BGPDocumentedException e) {
 375         final BGPError error = e.getError();
 376         final byte[] data = e.getData();
 377         final NotifyBuilder builder = new NotifyBuilder().setErrorCode(error.getCode())
 378                 .setErrorSubcode(error.getSubcode());
 379         if (data != null && data.length != 0) {
 380             builder.setData(data);
 381         }
 382         this.writeAndFlush(builder.build());
 383         notifyTerminationReasonAndCloseWithoutMessage(error.getCode(), error.getSubcode());
 384     }
 385
 386     private void removePeerSession() {
 387         if (this.peerRegistry != null) {
 388             this.peerRegistry.removePeerSession(StrictBGPPeerRegistry.getIpAddress(this.channel.remoteAddress()));
 389         }
 390     }
 391
 392     /**
 393      * If HoldTimer expires, the session ends. If a message (whichever) was received during this period, the HoldTimer
 394      * will be rescheduled by HOLD_TIMER_VALUE + the time that has passed from the start of the HoldTimer to the time at
 395      * which the message was received. If the session was closed by the time this method starts to execute (the session
 396      * state will become IDLE), then rescheduling won't occur.
 397      */
 398     private synchronized void handleHoldTimer() {
 399         if (this.state == State.IDLE) {
 400             return;
 401         }
 402
 403         final long ct = System.nanoTime();
 404         final long nextHold = this.lastMessageReceivedAt + TimeUnit.SECONDS.toNanos(this.holdTimerValue);
 405
 406         if (ct >= nextHold) {
 407             LOG.debug("HoldTimer expired. {}", new Date());
 408             this.terminate(new BGPDocumentedException(BGPError.HOLD_TIMER_EXPIRED));
 409         } else {
 410             this.channel.eventLoop().schedule(this::handleHoldTimer, nextHold - ct, TimeUnit.NANOSECONDS);
 411         }
 412     }
 413
 414     /**
 415      * If KeepAlive Timer expires, sends KeepAlive message. If a message (whichever) was send during this period, the
 416      * KeepAlive Timer will be rescheduled by KEEP_ALIVE_TIMER_VALUE + the time that has passed from the start of the
 417      * KeepAlive timer to the time at which the message was sent. If the session was closed by the time this method
 418      * starts to execute (the session state will become IDLE), that rescheduling won't occur.
 419      */
 420     private synchronized void handleKeepaliveTimer() {
 421         if (this.state == State.IDLE) {
 422             return;
 423         }
 424
 425         final long ct = System.nanoTime();
 426         long nextKeepalive = this.lastMessageSentAt + TimeUnit.SECONDS.toNanos(this.keepAlive);
 427
 428         if (ct >= nextKeepalive) {
 429             this.writeAndFlush(KEEP_ALIVE);
 430             nextKeepalive = this.lastMessageSentAt + TimeUnit.SECONDS.toNanos(this.keepAlive);
 431         }
 432         this.channel.eventLoop().schedule(this::handleKeepaliveTimer, nextKeepalive - ct, TimeUnit.NANOSECONDS);
 433     }
 434
 435     @Override
 436     public final String toString() {
 437         return addToStringAttributes(MoreObjects.toStringHelper(this)).toString();
 438     }
 439
 440     protected ToStringHelper addToStringAttributes(final ToStringHelper toStringHelper) {
 441         toStringHelper.add("channel", this.channel);
 442         toStringHelper.add("state", this.getState());
 443         return toStringHelper;
 444     }
 445
 446     @Override
 447     public Set<BgpTableType> getAdvertisedTableTypes() {
 448         return this.tableTypes;
 449     }
 450
 451     @Override
 452     public List<AddressFamilies> getAdvertisedAddPathTableTypes() {
 453         return this.addPathTypes;
 454     }
 455
 456     @Override
 457     public GracefulRestartCapability getAdvertisedGracefulRestartCapability() {
 458         return this.gracefulCapability;
 459     }
 460
 461     @Override
 462     public LlGracefulRestartCapability getAdvertisedLlGracefulRestartCapability() {
 463         return this.llGracefulCapability;
 464     }
 465
 466     @VisibleForTesting
 467     synchronized void sessionUp() {
 468         this.state = State.UP;
 469         try {
 470             this.sessionState.setSessionState(this.state);
 471             this.listener.onSessionUp(this);
 472         } catch (final Exception e) {
 473             handleException(e);
 474             throw e;
 475         }
 476     }
 477
 478     public synchronized State getState() {
 479         return this.state;
 480     }
 481
 482     @Override
 483     public final Ipv4Address getBgpId() {
 484         return this.bgpId;
 485     }
 486
 487     @Override
 488     public final AsNumber getAsNumber() {
 489         return this.asNumber;
 490     }
 491
 492     private synchronized boolean isWritable() {
 493         return this.channel != null && this.channel.isWritable();
 494     }
 495
 496     public ChannelOutputLimiter getLimiter() {
 497         return this.limiter;
 498     }
 499
 500     @Override
 501     public final void channelInactive(final ChannelHandlerContext ctx) {
 502         LOG.debug("Channel {} inactive.", ctx.channel());
 503         this.endOfInput();
 504
 505         try {
 506             super.channelInactive(ctx);
 507         } catch (final Exception e) {
 508             throw new IllegalStateException("Failed to delegate channel inactive event on channel " + ctx.channel(), e);
 509         }
 510     }
 511
 512     @Override
 513     protected final void channelRead0(final ChannelHandlerContext ctx, final Notification msg) {
 514         LOG.debug("Message was received: {}", msg);
 515         this.handleMessage(msg);
 516     }
 517
 518     @Override
 519     public final void handlerAdded(final ChannelHandlerContext ctx) {
 520         this.sessionUp();
 521     }
 522
 523     @Override
 524     public synchronized void exceptionCaught(final ChannelHandlerContext ctx, final Throwable cause) {
 525         handleException(cause);
 526     }
 527
 528     /**
 529      * Handle exception occurred in the BGP session. The session in error state should be closed
 530      * properly so that it can be restored later.
 531      */
 532     @VisibleForTesting
 533     void handleException(final Throwable cause) {
 534         LOG.warn("BGP session encountered error", cause);
 535         final Throwable docCause = cause.getCause();
 536         if (docCause instanceof BGPDocumentedException) {
 537             this.terminate((BGPDocumentedException) docCause);
 538         } else {
 539             this.terminate(new BGPDocumentedException(BGPError.CEASE));
 540         }
 541     }
 542
 543     @Override
 544     public BGPSessionState getBGPSessionState() {
 545         return this.sessionState;
 546     }
 547
 548     @Override
 549     public BGPTimersState getBGPTimersState() {
 550         return this.sessionState;
 551     }
 552
 553     @Override
 554     public BGPTransportState getBGPTransportState() {
 555         return this.sessionState;
 556     }
 557
 558     @Override
 559     public void registerMessagesCounter(final BGPMessagesListener bgpMessagesListener) {
 560         this.sessionState.registerMessagesCounter(bgpMessagesListener);
 561     }
 562
 563     @Override
 564     public <T extends PeerConstraint> void addDecoderConstraint(final Class<T> constraintClass, final T constraint) {
 565         this.channel.pipeline().get(BGPByteToMessageDecoder.class).addDecoderConstraint(constraintClass, constraint);
 566     }
 567 }