[Emu][ONOS-2597] BGP Keepalive message encoding and decoding

Change-Id: I4dd39f1725aa426827d5c4f011f5a0e02557a5c3

+/*
+ * Copyright 2015 Open Networking Laboratory
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.onosproject.bgpio.protocol;
+
+import org.jboss.netty.buffer.ChannelBuffer;
+import org.onosproject.bgpio.types.BGPHeader;
+
+/**
+ * Abstraction of an entity providing BGP Keepalive Message.
+ */
+public interface BGPKeepaliveMsg extends BGPMessage {
+
+    @Override
+    BGPVersion getVersion();
+
+    @Override
+    BGPType getType();
+
+    @Override
+    void writeTo(ChannelBuffer channelBuffer);
+
+    @Override
+    BGPHeader getHeader();
+
+    /**
+     * Builder interface with get and set functions to build Keepalive message.
+     */
+    interface Builder extends BGPMessage.Builder {
+
+        @Override
+        BGPKeepaliveMsg build();
+
+        @Override
+        BGPVersion getVersion();
+
+        @Override
+        BGPType getType();
+
+        @Override
+        Builder setHeader(BGPHeader bgpMsgHeader);
+
+        @Override
+        BGPHeader getHeader();
+    }
+}

+/*
+ * Copyright 2015 Open Networking Laboratory
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.onosproject.bgpio.protocol.ver4;
+
+import org.jboss.netty.buffer.ChannelBuffer;
+import org.onosproject.bgpio.exceptions.BGPParseException;
+import org.onosproject.bgpio.protocol.BGPKeepaliveMsg;
+import org.onosproject.bgpio.protocol.BGPMessageReader;
+import org.onosproject.bgpio.protocol.BGPMessageWriter;
+import org.onosproject.bgpio.types.BGPHeader;
+import org.onosproject.bgpio.protocol.BGPType;
+import org.onosproject.bgpio.protocol.BGPVersion;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import com.google.common.base.MoreObjects;
+
+/**
+ * Provides BGP keep alive message.
+ */
+class BGPKeepaliveMsgVer4 implements BGPKeepaliveMsg {
+
+    /*
+    <Keepalive Message>::= <Common Header>
+    A KEEPALIVE message consists of only the message header and has a
+    length of 19 octets.
+
+    0                   1                   2                   3
+    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+    |                                                               |
+    +                                                               +
+    |                                                               |
+    +                                                               +
+    |                           Marker                              |
+    +                                                               +
+    |                                                               |
+    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+    |          Length               |      Type     |
+    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+
+    REFERENCE : RFC 4271
+    */
+
+    protected static final Logger log = LoggerFactory
+            .getLogger(BGPKeepaliveMsgVer4.class);
+
+    private BGPHeader bgpMsgHeader;
+    public static final byte PACKET_VERSION = 4;
+    public static final int PACKET_MINIMUM_LENGTH = 19;
+    public static final int MARKER_LENGTH = 16;
+    public static final BGPType MSG_TYPE = BGPType.KEEP_ALIVE;
+    public static byte[] marker = new byte[] {(byte) 0xff, (byte) 0xff, (byte) 0xff, (byte) 0xff,
+                                              (byte) 0xff, (byte) 0xff, (byte) 0xff, (byte) 0xff,
+                                              (byte) 0xff, (byte) 0xff, (byte) 0xff, (byte) 0xff,
+                                              (byte) 0xff, (byte) 0xff, (byte) 0xff, (byte) 0xff};
+
+    public static final BGPKeepaliveMsgVer4.Reader READER = new Reader();
+
+    /**
+     * Reader class for reading BGP keepalive message from channel buffer.
+     */
+    static class Reader implements BGPMessageReader<BGPKeepaliveMsg> {
+
+        @Override
+        public BGPKeepaliveMsg readFrom(ChannelBuffer cb, BGPHeader bgpHeader)
+                throws BGPParseException {
+
+            /* bgpHeader is not required in case of keepalive message and
+            Header is already read and no other fields except header in keepalive message.*/
+            return new BGPKeepaliveMsgVer4();
+        }
+    }
+
+    /**
+     * Default constructor.
+     */
+    BGPKeepaliveMsgVer4() {
+    }
+
+    /**
+     * Builder class for BGP keepalive message.
+     */
+    static class Builder implements BGPKeepaliveMsg.Builder {
+        BGPHeader bgpMsgHeader;
+
+        @Override
+        public BGPVersion getVersion() {
+            return BGPVersion.BGP_4;
+        }
+
+        @Override
+        public BGPType getType() {
+            return BGPType.KEEP_ALIVE;
+        }
+
+        @Override
+        public BGPHeader getHeader() {
+            return this.bgpMsgHeader;
+        }
+
+        @Override
+        public Builder setHeader(BGPHeader bgpMsgHeader) {
+            this.bgpMsgHeader = bgpMsgHeader;
+            return this;
+        }
+
+        @Override
+        public BGPKeepaliveMsg build() {
+            return new BGPKeepaliveMsgVer4();
+        }
+    }
+
+    @Override
+    public void writeTo(ChannelBuffer cb) {
+        WRITER.write(cb, this);
+    }
+
+    static final Writer WRITER = new Writer();
+
+    /**
+     * Writer class for writing the BGP keepalive message to channel buffer.
+     */
+    static class Writer implements BGPMessageWriter<BGPKeepaliveMsgVer4> {
+
+        @Override
+        public void write(ChannelBuffer cb, BGPKeepaliveMsgVer4 message) {
+
+            // write marker
+            cb.writeBytes(marker, 0, MARKER_LENGTH);
+
+            // write length of header
+            cb.writeShort(PACKET_MINIMUM_LENGTH);
+
+            // write the type of message
+            cb.writeByte(MSG_TYPE.getType());
+        }
+    }
+
+    @Override
+    public BGPVersion getVersion() {
+        return BGPVersion.BGP_4;
+    }
+
+    @Override
+    public BGPType getType() {
+        return MSG_TYPE;
+    }
+
+    @Override
+    public BGPHeader getHeader() {
+        return this.bgpMsgHeader;
+    }
+
+    @Override
+    public String toString() {
+        return MoreObjects.toStringHelper(getClass()).toString();
+    }
+}