From 1d26c0a20d3c595d2846de31c2034e27595540b1 Mon Sep 17 00:00:00 2001
From: JanHolger <jan@bebendorf.eu>
Date: Tue, 6 Jul 2021 17:01:33 +0200
Subject: Initial commit

---
 src/main/java/com/lumaserv/bgp/BGPListener.java    | 11 ++++
 src/main/java/com/lumaserv/bgp/BGPServer.java      | 70 ++++++++++++++++++++
 src/main/java/com/lumaserv/bgp/BGPSession.java     | 54 +++++++++++++++
 .../com/lumaserv/bgp/BGPSessionConfiguration.java  | 19 ++++++
 .../java/com/lumaserv/bgp/protocol/BGPPacket.java  | 76 ++++++++++++++++++++++
 .../java/com/lumaserv/bgp/protocol/IPPrefix.java   | 27 ++++++++
 .../protocol/attribute/AS4AggregatorAttribute.java | 30 +++++++++
 .../bgp/protocol/attribute/AS4PathAttribute.java   | 45 +++++++++++++
 .../bgp/protocol/attribute/ASPathAttribute.java    | 40 ++++++++++++
 .../protocol/attribute/ASPathLimitAttribute.java   | 29 +++++++++
 .../protocol/attribute/AggregatorAttribute.java    | 27 ++++++++
 .../attribute/AtomicAggregateAttribute.java        | 17 +++++
 .../protocol/attribute/CommunitiesAttribute.java   | 41 ++++++++++++
 .../protocol/attribute/DevelopmentAttribute.java   | 24 +++++++
 .../attribute/ExtendedCommuntiesAttribute.java     | 33 ++++++++++
 .../attribute/LargeCommunityAttribute.java         | 56 ++++++++++++++++
 .../bgp/protocol/attribute/NextHopAttribute.java   | 20 ++++++
 .../bgp/protocol/attribute/OriginAttribute.java    | 24 +++++++
 .../bgp/protocol/attribute/PathAttribute.java      | 38 +++++++++++
 .../bgp/protocol/attribute/UnknownAttribute.java   | 23 +++++++
 .../bgp/protocol/message/BGPNotification.java      | 18 +++++
 .../com/lumaserv/bgp/protocol/message/BGPOpen.java | 35 ++++++++++
 .../lumaserv/bgp/protocol/message/BGPUpdate.java   | 63 ++++++++++++++++++
 23 files changed, 820 insertions(+)
 create mode 100644 src/main/java/com/lumaserv/bgp/BGPListener.java
 create mode 100644 src/main/java/com/lumaserv/bgp/BGPServer.java
 create mode 100644 src/main/java/com/lumaserv/bgp/BGPSession.java
 create mode 100644 src/main/java/com/lumaserv/bgp/BGPSessionConfiguration.java
 create mode 100644 src/main/java/com/lumaserv/bgp/protocol/BGPPacket.java
 create mode 100644 src/main/java/com/lumaserv/bgp/protocol/IPPrefix.java
 create mode 100644 src/main/java/com/lumaserv/bgp/protocol/attribute/AS4AggregatorAttribute.java
 create mode 100644 src/main/java/com/lumaserv/bgp/protocol/attribute/AS4PathAttribute.java
 create mode 100644 src/main/java/com/lumaserv/bgp/protocol/attribute/ASPathAttribute.java
 create mode 100644 src/main/java/com/lumaserv/bgp/protocol/attribute/ASPathLimitAttribute.java
 create mode 100644 src/main/java/com/lumaserv/bgp/protocol/attribute/AggregatorAttribute.java
 create mode 100644 src/main/java/com/lumaserv/bgp/protocol/attribute/AtomicAggregateAttribute.java
 create mode 100644 src/main/java/com/lumaserv/bgp/protocol/attribute/CommunitiesAttribute.java
 create mode 100644 src/main/java/com/lumaserv/bgp/protocol/attribute/DevelopmentAttribute.java
 create mode 100644 src/main/java/com/lumaserv/bgp/protocol/attribute/ExtendedCommuntiesAttribute.java
 create mode 100644 src/main/java/com/lumaserv/bgp/protocol/attribute/LargeCommunityAttribute.java
 create mode 100644 src/main/java/com/lumaserv/bgp/protocol/attribute/NextHopAttribute.java
 create mode 100644 src/main/java/com/lumaserv/bgp/protocol/attribute/OriginAttribute.java
 create mode 100644 src/main/java/com/lumaserv/bgp/protocol/attribute/PathAttribute.java
 create mode 100644 src/main/java/com/lumaserv/bgp/protocol/attribute/UnknownAttribute.java
 create mode 100644 src/main/java/com/lumaserv/bgp/protocol/message/BGPNotification.java
 create mode 100644 src/main/java/com/lumaserv/bgp/protocol/message/BGPOpen.java
 create mode 100644 src/main/java/com/lumaserv/bgp/protocol/message/BGPUpdate.java

(limited to 'src/main/java')

diff --git a/src/main/java/com/lumaserv/bgp/BGPListener.java b/src/main/java/com/lumaserv/bgp/BGPListener.java
new file mode 100644
index 0000000..54f4fe5
--- /dev/null
+++ b/src/main/java/com/lumaserv/bgp/BGPListener.java
@@ -0,0 +1,11 @@
+package com.lumaserv.bgp;
+
+import com.lumaserv.bgp.protocol.message.BGPUpdate;
+
+public interface BGPListener {
+
+    void onOpen(BGPSession session);
+    void onUpdate(BGPSession session, BGPUpdate update);
+    void onClose(BGPSession session);
+
+}
diff --git a/src/main/java/com/lumaserv/bgp/BGPServer.java b/src/main/java/com/lumaserv/bgp/BGPServer.java
new file mode 100644
index 0000000..2e960fe
--- /dev/null
+++ b/src/main/java/com/lumaserv/bgp/BGPServer.java
@@ -0,0 +1,70 @@
+package com.lumaserv.bgp;
+
+import com.lumaserv.bgp.protocol.BGPPacket;
+import com.lumaserv.bgp.protocol.message.BGPOpen;
+import lombok.Getter;
+
+import java.io.IOException;
+import java.net.ServerSocket;
+import java.net.Socket;
+import java.util.ArrayList;
+import java.util.List;
+
+public class BGPServer implements Runnable {
+
+    final ServerSocket serverSocket;
+    @Getter
+    final List<BGPSessionConfiguration> sessionConfigurations = new ArrayList<>();
+
+    public BGPServer() throws IOException {
+        serverSocket = new ServerSocket(179);
+    }
+
+    private static boolean checkEqual(byte[] a, byte[] b) {
+        if(a == b)
+            return true;
+        if(a == null || b == null)
+            return false;
+        if(a.length != b.length)
+            return false;
+        for(int i=0; i<a.length; i++) {
+            if(a[i] != b[i])
+                return false;
+        }
+        return true;
+    }
+
+    public void run() {
+        while (true) {
+            try {
+                Socket socket = serverSocket.accept();
+                BGPPacket packet = BGPPacket.read(socket.getInputStream());
+                if(packet.getType() != BGPPacket.Type.OPEN)
+                    continue;
+                BGPOpen request = new BGPOpen(packet.getMessage());
+                BGPSessionConfiguration config = sessionConfigurations.stream()
+                        .filter(c -> c.getRemoteAs() == request.getAsn() && checkEqual(c.getRemoteIdentifier(), request.getIdentifier()))
+                        .findFirst()
+                        .orElse(null);
+                if(config == null)
+                    continue;
+                BGPOpen response = new BGPOpen()
+                        .setAsn(config.getLocalAs())
+                        .setHoldTime(request.getHoldTime())
+                        .setVersion(request.getVersion())
+                        .setIdentifier(config.getLocalIdentifier());
+                try {
+                    socket.getOutputStream().write(new BGPPacket().setType(BGPPacket.Type.OPEN).setMessage(response.build()).build());
+                } catch (IOException e) {
+                    e.printStackTrace();
+                }
+                BGPSession session = new BGPSession(socket, config);
+                session.keepAlive();
+                new Thread(session).start();
+            } catch (IOException ex) {
+                ex.printStackTrace();
+            }
+        }
+    }
+
+}
diff --git a/src/main/java/com/lumaserv/bgp/BGPSession.java b/src/main/java/com/lumaserv/bgp/BGPSession.java
new file mode 100644
index 0000000..de1fc66
--- /dev/null
+++ b/src/main/java/com/lumaserv/bgp/BGPSession.java
@@ -0,0 +1,54 @@
+package com.lumaserv.bgp;
+
+import com.lumaserv.bgp.protocol.BGPPacket;
+import com.lumaserv.bgp.protocol.message.BGPUpdate;
+import lombok.Getter;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.OutputStream;
+import java.net.Socket;
+
+public class BGPSession implements Runnable {
+
+    @Getter
+    final BGPSessionConfiguration configuration;
+    final InputStream inputStream;
+    final OutputStream outputStream;
+
+    public BGPSession(Socket socket, BGPSessionConfiguration configuration) throws IOException {
+        this.configuration = configuration;
+        this.inputStream = socket.getInputStream();
+        this.outputStream = socket.getOutputStream();
+    }
+
+    public void keepAlive() {
+        try {
+            outputStream.write(new BGPPacket().setType(BGPPacket.Type.KEEPALIVE).setMessage(new byte[0]).build());
+        } catch (IOException e) {
+            e.printStackTrace();
+        }
+    }
+
+    private void handle(BGPPacket packet) {
+        switch (packet.getType()) {
+            case KEEPALIVE:
+                keepAlive();
+                break;
+            case UPDATE: {
+                configuration.getListener().onUpdate(this, new BGPUpdate(packet.getMessage()));
+                break;
+            }
+        }
+    }
+
+    public void run() {
+        try {
+            while (true)
+                handle(BGPPacket.read(inputStream));
+        } catch (IOException ex) {
+            ex.printStackTrace();
+        }
+    }
+
+}
diff --git a/src/main/java/com/lumaserv/bgp/BGPSessionConfiguration.java b/src/main/java/com/lumaserv/bgp/BGPSessionConfiguration.java
new file mode 100644
index 0000000..8102f81
--- /dev/null
+++ b/src/main/java/com/lumaserv/bgp/BGPSessionConfiguration.java
@@ -0,0 +1,19 @@
+package com.lumaserv.bgp;
+
+import lombok.AllArgsConstructor;
+import lombok.Getter;
+import lombok.Setter;
+
+@AllArgsConstructor
+@Setter
+@Getter
+public class BGPSessionConfiguration {
+
+    String name;
+    int localAs;
+    byte[] localIdentifier;
+    int remoteAs;
+    byte[] remoteIdentifier;
+    BGPListener listener;
+
+}
diff --git a/src/main/java/com/lumaserv/bgp/protocol/BGPPacket.java b/src/main/java/com/lumaserv/bgp/protocol/BGPPacket.java
new file mode 100644
index 0000000..e7cf66b
--- /dev/null
+++ b/src/main/java/com/lumaserv/bgp/protocol/BGPPacket.java
@@ -0,0 +1,76 @@
+package com.lumaserv.bgp.protocol;
+
+import lombok.AllArgsConstructor;
+import lombok.Getter;
+import lombok.NoArgsConstructor;
+import lombok.Setter;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.util.Arrays;
+
+@Setter
+@Getter
+@NoArgsConstructor
+public class BGPPacket {
+
+    Type type;
+    byte[] message;
+
+    public BGPPacket(byte[] packet) {
+        type = Type.fromValue(packet[18]);
+        message = new byte[packet.length-19];
+        System.arraycopy(packet, 19, message, 0, message.length);
+    }
+
+    public byte[] build() {
+        byte[] packet = new byte[message.length + 19];
+        Arrays.fill(packet, 0, 16, (byte) 0xFF);
+        packet[16] = (byte)(packet.length >> 8);
+        packet[17] = (byte)(packet.length & 0xFF);
+        packet[18] = type.getValue();
+        System.arraycopy(message, 0, packet, 19, message.length);
+        return packet;
+    }
+
+    public static BGPPacket read(InputStream stream) throws IOException {
+        byte[] packet = new byte[18];
+        int value;
+        for(int i=0; i<packet.length; i++) {
+            value = stream.read();
+            if(value == -1)
+                throw new IOException("Unexpected end of stream");
+            packet[i] = (byte) value;
+        }
+        int length = ((packet[16] & 0xFF) << 8) | (packet[17] & 0xFF);
+        byte[] newPacket = new byte[length];
+        System.arraycopy(packet, 0, newPacket, 0, packet.length);
+        packet = newPacket;
+        for(int i=18; i<packet.length; i++) {
+            value = stream.read();
+            if(value == -1)
+                throw new IOException("Unexpected end of stream");
+            packet[i] = (byte) value;
+        }
+        return new BGPPacket(packet);
+    }
+
+    @AllArgsConstructor
+    @Getter
+    public enum Type {
+        OPEN((byte) 1),
+        UPDATE((byte) 2),
+        NOTIFICATION((byte) 3),
+        KEEPALIVE((byte) 4),
+        ROUTE_REFRESH((byte) 5);
+        final byte value;
+        public static Type fromValue(byte value) {
+            for(Type t : values()) {
+                if(t.value == value)
+                    return t;
+            }
+            return null;
+        }
+    }
+
+}
diff --git a/src/main/java/com/lumaserv/bgp/protocol/IPPrefix.java b/src/main/java/com/lumaserv/bgp/protocol/IPPrefix.java
new file mode 100644
index 0000000..be70c4f
--- /dev/null
+++ b/src/main/java/com/lumaserv/bgp/protocol/IPPrefix.java
@@ -0,0 +1,27 @@
+package com.lumaserv.bgp.protocol;
+
+import lombok.Getter;
+import lombok.NoArgsConstructor;
+import lombok.Setter;
+
+import java.net.InetAddress;
+import java.net.UnknownHostException;
+
+@NoArgsConstructor
+@Setter
+@Getter
+public class IPPrefix {
+
+    byte[] address;
+    byte length;
+
+    public String toString() {
+        try {
+            return InetAddress.getByAddress(address).getHostAddress() + "/" + length;
+        } catch (UnknownHostException e) {
+            e.printStackTrace();
+            return null;
+        }
+    }
+
+}
diff --git a/src/main/java/com/lumaserv/bgp/protocol/attribute/AS4AggregatorAttribute.java b/src/main/java/com/lumaserv/bgp/protocol/attribute/AS4AggregatorAttribute.java
new file mode 100644
index 0000000..c579210
--- /dev/null
+++ b/src/main/java/com/lumaserv/bgp/protocol/attribute/AS4AggregatorAttribute.java
@@ -0,0 +1,30 @@
+package com.lumaserv.bgp.protocol.attribute;
+
+import lombok.Getter;
+import lombok.Setter;
+
+@Getter
+@Setter
+public class AS4AggregatorAttribute implements PathAttribute {
+
+    int as;
+    byte[] origin;
+
+    public AS4AggregatorAttribute(byte typeCode, byte[] data) {
+        as = ((data[0] & 0xFF) << 24) |
+                ((data[1] & 0xFF) << 16) |
+                ((data[2] & 0xFF) << 8) |
+                (data[3] & 0xFF);
+        origin = new byte[4];
+        System.arraycopy(data, 4, origin, 0, origin.length);
+    }
+
+    public byte getTypeCode() {
+        return 18;
+    }
+
+    public byte[] build() {
+        return new byte[0];
+    }
+
+}
diff --git a/src/main/java/com/lumaserv/bgp/protocol/attribute/AS4PathAttribute.java b/src/main/java/com/lumaserv/bgp/protocol/attribute/AS4PathAttribute.java
new file mode 100644
index 0000000..415dd5f
--- /dev/null
+++ b/src/main/java/com/lumaserv/bgp/protocol/attribute/AS4PathAttribute.java
@@ -0,0 +1,45 @@
+package com.lumaserv.bgp.protocol.attribute;
+
+import lombok.Getter;
+import lombok.Setter;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class AS4PathAttribute implements PathAttribute {
+
+    List<Segment> segments = new ArrayList<>();
+
+    public AS4PathAttribute(byte typeCode, byte[] data) {
+        int offset = 0;
+        while (offset < data.length) {
+            Segment segment = new Segment().setType(data[offset]);
+            byte length = data[offset + 1];
+            for(int i=0; i<length; i++)
+                segment.asns.add(
+                        ((data[offset + 2 + (i * 4)] & 0xFF) << 24) |
+                        ((data[offset + 3 + (i * 4)] & 0xFF) << 16) |
+                        ((data[offset + 4 + (i * 4)] & 0xFF) << 8) |
+                        (data[offset + 5 + (i * 4)] & 0xFF)
+                );
+            offset += 2 + (length * 4);
+            segments.add(segment);
+        }
+    }
+
+    public byte getTypeCode() {
+        return 17;
+    }
+
+    public byte[] build() {
+        return new byte[0];
+    }
+
+    @Getter
+    @Setter
+    public static class Segment {
+        byte type;
+        List<Integer> asns = new ArrayList<>();
+    }
+
+}
diff --git a/src/main/java/com/lumaserv/bgp/protocol/attribute/ASPathAttribute.java b/src/main/java/com/lumaserv/bgp/protocol/attribute/ASPathAttribute.java
new file mode 100644
index 0000000..64be45b
--- /dev/null
+++ b/src/main/java/com/lumaserv/bgp/protocol/attribute/ASPathAttribute.java
@@ -0,0 +1,40 @@
+package com.lumaserv.bgp.protocol.attribute;
+
+import lombok.Getter;
+import lombok.Setter;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class ASPathAttribute implements PathAttribute {
+
+    List<Segment> segments = new ArrayList<>();
+
+    public ASPathAttribute(byte typeCode, byte[] data) {
+        int offset = 0;
+        while (offset < data.length) {
+            Segment segment = new Segment().setType(data[offset]);
+            byte length = data[offset + 1];
+            for(int i=0; i<length; i++)
+                segment.asns.add(((data[offset + 2 + (i * 2)] & 0xFF) << 8) | (data[offset + 3 + (i * 2)] & 0xFF));
+            offset += 2 + (length * 2);
+            segments.add(segment);
+        }
+    }
+
+    public byte getTypeCode() {
+        return 2;
+    }
+
+    public byte[] build() {
+        return new byte[0];
+    }
+
+    @Getter
+    @Setter
+    public static class Segment {
+        byte type;
+        List<Integer> asns = new ArrayList<>();
+    }
+
+}
diff --git a/src/main/java/com/lumaserv/bgp/protocol/attribute/ASPathLimitAttribute.java b/src/main/java/com/lumaserv/bgp/protocol/attribute/ASPathLimitAttribute.java
new file mode 100644
index 0000000..732b018
--- /dev/null
+++ b/src/main/java/com/lumaserv/bgp/protocol/attribute/ASPathLimitAttribute.java
@@ -0,0 +1,29 @@
+package com.lumaserv.bgp.protocol.attribute;
+
+import lombok.Getter;
+import lombok.Setter;
+
+@Setter
+@Getter
+public class ASPathLimitAttribute implements PathAttribute {
+
+    byte upperBound;
+    int as;
+
+    public ASPathLimitAttribute(byte typeCode, byte[] data) {
+        upperBound = data[0];
+        as = ((data[1] & 0xFF) << 24) |
+                ((data[2] & 0xFF) << 16) |
+                ((data[3] & 0xFF) << 8) |
+                (data[4] & 0xFF);
+    }
+
+    public byte getTypeCode() {
+        return 21;
+    }
+
+    public byte[] build() {
+        return new byte[0];
+    }
+
+}
diff --git a/src/main/java/com/lumaserv/bgp/protocol/attribute/AggregatorAttribute.java b/src/main/java/com/lumaserv/bgp/protocol/attribute/AggregatorAttribute.java
new file mode 100644
index 0000000..8a3dfdb
--- /dev/null
+++ b/src/main/java/com/lumaserv/bgp/protocol/attribute/AggregatorAttribute.java
@@ -0,0 +1,27 @@
+package com.lumaserv.bgp.protocol.attribute;
+
+import lombok.Getter;
+import lombok.Setter;
+
+@Getter
+@Setter
+public class AggregatorAttribute implements PathAttribute {
+
+    int as;
+    byte[] origin;
+
+    public AggregatorAttribute(byte typeCode, byte[] data) {
+        as = ((data[0] & 0xFF) << 8) | (data[1] & 0xFF);
+        origin = new byte[4];
+        System.arraycopy(data, 2, origin, 0, origin.length);
+    }
+
+    public byte getTypeCode() {
+        return 7;
+    }
+
+    public byte[] build() {
+        return new byte[0];
+    }
+
+}
diff --git a/src/main/java/com/lumaserv/bgp/protocol/attribute/AtomicAggregateAttribute.java b/src/main/java/com/lumaserv/bgp/protocol/attribute/AtomicAggregateAttribute.java
new file mode 100644
index 0000000..6f7e479
--- /dev/null
+++ b/src/main/java/com/lumaserv/bgp/protocol/attribute/AtomicAggregateAttribute.java
@@ -0,0 +1,17 @@
+package com.lumaserv.bgp.protocol.attribute;
+
+public class AtomicAggregateAttribute implements PathAttribute {
+
+    public AtomicAggregateAttribute(byte typeCode, byte[] data) {
+
+    }
+
+    public byte getTypeCode() {
+        return 6;
+    }
+
+    public byte[] build() {
+        return new byte[0];
+    }
+
+}
diff --git a/src/main/java/com/lumaserv/bgp/protocol/attribute/CommunitiesAttribute.java b/src/main/java/com/lumaserv/bgp/protocol/attribute/CommunitiesAttribute.java
new file mode 100644
index 0000000..7c7f060
--- /dev/null
+++ b/src/main/java/com/lumaserv/bgp/protocol/attribute/CommunitiesAttribute.java
@@ -0,0 +1,41 @@
+package com.lumaserv.bgp.protocol.attribute;
+
+import lombok.Getter;
+import lombok.Setter;
+
+import java.util.ArrayList;
+import java.util.List;
+
+@Getter
+@Setter
+public class CommunitiesAttribute implements PathAttribute {
+
+    List<Community> communities = new ArrayList<>();
+
+    public CommunitiesAttribute(byte typeCode, byte[] data) {
+        int offset = 0;
+        while (offset < data.length) {
+            communities.add(new Community()
+                    .setValueA(((data[offset] & 0xFF) << 8) | (data[offset + 1] & 0xFF))
+                    .setValueB(((data[offset + 2] & 0xFF) << 8) | (data[offset + 3] & 0xFF))
+            );
+            offset += 4;
+        }
+    }
+
+    public byte getTypeCode() {
+        return 8;
+    }
+
+    public byte[] build() {
+        return new byte[0];
+    }
+
+    @Setter
+    @Getter
+    public static class Community {
+        int valueA;
+        int valueB;
+    }
+
+}
diff --git a/src/main/java/com/lumaserv/bgp/protocol/attribute/DevelopmentAttribute.java b/src/main/java/com/lumaserv/bgp/protocol/attribute/DevelopmentAttribute.java
new file mode 100644
index 0000000..453f934
--- /dev/null
+++ b/src/main/java/com/lumaserv/bgp/protocol/attribute/DevelopmentAttribute.java
@@ -0,0 +1,24 @@
+package com.lumaserv.bgp.protocol.attribute;
+
+import lombok.Getter;
+import lombok.Setter;
+
+@Getter
+@Setter
+public class DevelopmentAttribute implements PathAttribute {
+
+    byte[] data;
+
+    public DevelopmentAttribute(byte typeCode, byte[] data) {
+        this.data = data;
+    }
+
+    public byte[] build() {
+        return data;
+    }
+
+    public byte getTypeCode() {
+        return (byte) 255;
+    }
+
+}
diff --git a/src/main/java/com/lumaserv/bgp/protocol/attribute/ExtendedCommuntiesAttribute.java b/src/main/java/com/lumaserv/bgp/protocol/attribute/ExtendedCommuntiesAttribute.java
new file mode 100644
index 0000000..759ae60
--- /dev/null
+++ b/src/main/java/com/lumaserv/bgp/protocol/attribute/ExtendedCommuntiesAttribute.java
@@ -0,0 +1,33 @@
+package com.lumaserv.bgp.protocol.attribute;
+
+import lombok.Getter;
+import lombok.Setter;
+
+@Getter
+@Setter
+public class ExtendedCommuntiesAttribute implements PathAttribute {
+
+    byte type;
+    byte subType;
+    int as;
+    int an;
+
+    public ExtendedCommuntiesAttribute(byte typeCode, byte[] data) {
+        type = data[0];
+        subType = data[1];
+        as = ((data[2] & 0xFF) << 24) |
+                ((data[3] & 0xFF) << 16) |
+                ((data[4] & 0xFF) << 8) |
+                (data[5] & 0xFF);
+        an = ((data[6] & 0xFF) << 8) | (data[7] & 0xFF);
+    }
+
+    public byte getTypeCode() {
+        return 16;
+    }
+
+    public byte[] build() {
+        return new byte[0];
+    }
+
+}
diff --git a/src/main/java/com/lumaserv/bgp/protocol/attribute/LargeCommunityAttribute.java b/src/main/java/com/lumaserv/bgp/protocol/attribute/LargeCommunityAttribute.java
new file mode 100644
index 0000000..921d5a5
--- /dev/null
+++ b/src/main/java/com/lumaserv/bgp/protocol/attribute/LargeCommunityAttribute.java
@@ -0,0 +1,56 @@
+package com.lumaserv.bgp.protocol.attribute;
+
+import lombok.Getter;
+import lombok.Setter;
+
+import java.util.ArrayList;
+import java.util.List;
+
+@Getter
+@Setter
+public class LargeCommunityAttribute implements PathAttribute {
+
+    List<LargeCommunity> communities = new ArrayList<>();
+
+    public LargeCommunityAttribute(byte typeCode, byte[] data) {
+        for(int i=0; i<data.length; i+=12) {
+            communities.add(new LargeCommunity()
+                    .setGlobalAdministrator(
+                            ((data[i] & 0xFF) << 24) |
+                            ((data[i+1] & 0xFF) << 16) |
+                            ((data[i+2] & 0xFF) << 8) |
+                            (data[i+3] & 0xFF)
+                    )
+                    .setLocalDataPart1(
+                            ((data[i+4] & 0xFF) << 24) |
+                            ((data[i+5] & 0xFF) << 16) |
+                            ((data[i+6] & 0xFF) << 8) |
+                            (data[i+7] & 0xFF)
+                    )
+                    .setLocalDataPart2(
+                            ((data[i+8] & 0xFF) << 24) |
+                            ((data[i+9] & 0xFF) << 16) |
+                            ((data[i+10] & 0xFF) << 8) |
+                            (data[i+11] & 0xFF)
+                    )
+            );
+        }
+    }
+
+    public byte getTypeCode() {
+        return 32;
+    }
+
+    public byte[] build() {
+        return new byte[0];
+    }
+
+    @Setter
+    @Getter
+    public static class LargeCommunity {
+        int globalAdministrator;
+        int localDataPart1;
+        int localDataPart2;
+    }
+
+}
diff --git a/src/main/java/com/lumaserv/bgp/protocol/attribute/NextHopAttribute.java b/src/main/java/com/lumaserv/bgp/protocol/attribute/NextHopAttribute.java
new file mode 100644
index 0000000..f60d236
--- /dev/null
+++ b/src/main/java/com/lumaserv/bgp/protocol/attribute/NextHopAttribute.java
@@ -0,0 +1,20 @@
+package com.lumaserv.bgp.protocol.attribute;
+
+public class NextHopAttribute implements PathAttribute {
+
+    byte[] address;
+
+    public NextHopAttribute(byte typeCode, byte[] data) {
+        this.address = new byte[data.length];
+        System.arraycopy(data, 0, address, 0, address.length);
+    }
+
+    public byte getTypeCode() {
+        return 3;
+    }
+
+    public byte[] build() {
+        return address;
+    }
+
+}
diff --git a/src/main/java/com/lumaserv/bgp/protocol/attribute/OriginAttribute.java b/src/main/java/com/lumaserv/bgp/protocol/attribute/OriginAttribute.java
new file mode 100644
index 0000000..2bf1208
--- /dev/null
+++ b/src/main/java/com/lumaserv/bgp/protocol/attribute/OriginAttribute.java
@@ -0,0 +1,24 @@
+package com.lumaserv.bgp.protocol.attribute;
+
+import lombok.Getter;
+import lombok.Setter;
+
+@Getter
+@Setter
+public class OriginAttribute implements PathAttribute {
+
+    byte origin;
+
+    public OriginAttribute(byte typeCode, byte[] data) {
+        origin = data[0];
+    }
+
+    public byte getTypeCode() {
+        return 1;
+    }
+
+    public byte[] build() {
+        return new byte[0];
+    }
+
+}
diff --git a/src/main/java/com/lumaserv/bgp/protocol/attribute/PathAttribute.java b/src/main/java/com/lumaserv/bgp/protocol/attribute/PathAttribute.java
new file mode 100644
index 0000000..4a10daa
--- /dev/null
+++ b/src/main/java/com/lumaserv/bgp/protocol/attribute/PathAttribute.java
@@ -0,0 +1,38 @@
+package com.lumaserv.bgp.protocol.attribute;
+
+public interface PathAttribute {
+
+    byte getTypeCode();
+    byte[] build();
+
+    static PathAttribute from(byte typeCode, byte[] data) {
+        switch (typeCode & 0xFF) {
+            case 1:
+                return new OriginAttribute(typeCode, data);
+            case 2:
+                return new ASPathAttribute(typeCode, data);
+            case 3:
+                return new NextHopAttribute(typeCode, data);
+            case 6:
+                return new AtomicAggregateAttribute(typeCode, data);
+            case 7:
+                return new AggregatorAttribute(typeCode, data);
+            case 8:
+                return new CommunitiesAttribute(typeCode, data);
+            case 16:
+                return new ExtendedCommuntiesAttribute(typeCode, data);
+            case 17:
+                return new AS4PathAttribute(typeCode, data);
+            case 18:
+                return new AS4AggregatorAttribute(typeCode, data);
+            case 21:
+                return new ASPathLimitAttribute(typeCode, data);
+            case 32:
+                return new LargeCommunityAttribute(typeCode, data);
+            case 255:
+                return new DevelopmentAttribute(typeCode, data);
+        }
+        return new UnknownAttribute(typeCode, data);
+    }
+
+}
diff --git a/src/main/java/com/lumaserv/bgp/protocol/attribute/UnknownAttribute.java b/src/main/java/com/lumaserv/bgp/protocol/attribute/UnknownAttribute.java
new file mode 100644
index 0000000..9dbe0f9
--- /dev/null
+++ b/src/main/java/com/lumaserv/bgp/protocol/attribute/UnknownAttribute.java
@@ -0,0 +1,23 @@
+package com.lumaserv.bgp.protocol.attribute;
+
+import lombok.AllArgsConstructor;
+import lombok.Getter;
+import lombok.Setter;
+
+@AllArgsConstructor
+@Getter
+@Setter
+public class UnknownAttribute implements PathAttribute {
+
+    byte typeCode;
+    byte[] data;
+
+    public byte[] build() {
+        return data;
+    }
+
+    public byte getTypeCode() {
+        return typeCode;
+    }
+
+}
diff --git a/src/main/java/com/lumaserv/bgp/protocol/message/BGPNotification.java b/src/main/java/com/lumaserv/bgp/protocol/message/BGPNotification.java
new file mode 100644
index 0000000..54ee9bd
--- /dev/null
+++ b/src/main/java/com/lumaserv/bgp/protocol/message/BGPNotification.java
@@ -0,0 +1,18 @@
+package com.lumaserv.bgp.protocol.message;
+
+import lombok.Getter;
+import lombok.Setter;
+
+@Getter
+@Setter
+public class BGPNotification {
+
+    byte majorErrorCode;
+    byte minorErrorCode;
+
+    public BGPNotification(byte[] message) {
+        this.majorErrorCode = message[0];
+        this.minorErrorCode = message[1];
+    }
+
+}
diff --git a/src/main/java/com/lumaserv/bgp/protocol/message/BGPOpen.java b/src/main/java/com/lumaserv/bgp/protocol/message/BGPOpen.java
new file mode 100644
index 0000000..875f7bc
--- /dev/null
+++ b/src/main/java/com/lumaserv/bgp/protocol/message/BGPOpen.java
@@ -0,0 +1,35 @@
+package com.lumaserv.bgp.protocol.message;
+
+import lombok.Getter;
+import lombok.NoArgsConstructor;
+import lombok.Setter;
+
+@Getter
+@Setter
+@NoArgsConstructor
+public class BGPOpen {
+
+    byte version;
+    int asn;
+    int holdTime;
+    byte[] identifier;
+
+    public BGPOpen(byte[] message) {
+        version = message[0];
+        asn = ((message[1] & 0xFF) << 8) | (message[2] & 0xFF);
+        holdTime = ((message[3] & 0xFF) << 8) | (message[4] & 0xFF);
+        identifier = new byte[4];
+    }
+
+    public byte[] build() {
+        byte[] message = new byte[6 + identifier.length];
+        message[0] = version;
+        message[1] = (byte) (asn >> 8);
+        message[2] = (byte) (asn & 0xFF);
+        message[3] = (byte) (holdTime >> 8);
+        message[4] = (byte) (holdTime & 0xFF);
+        System.arraycopy(identifier, 0, message, 5, identifier.length);
+        return message;
+    }
+
+}
diff --git a/src/main/java/com/lumaserv/bgp/protocol/message/BGPUpdate.java b/src/main/java/com/lumaserv/bgp/protocol/message/BGPUpdate.java
new file mode 100644
index 0000000..fa23432
--- /dev/null
+++ b/src/main/java/com/lumaserv/bgp/protocol/message/BGPUpdate.java
@@ -0,0 +1,63 @@
+package com.lumaserv.bgp.protocol.message;
+
+import com.lumaserv.bgp.protocol.IPPrefix;
+import com.lumaserv.bgp.protocol.attribute.PathAttribute;
+import lombok.Getter;
+import lombok.Setter;
+
+import java.util.ArrayList;
+import java.util.List;
+
+@Getter
+@Setter
+public class BGPUpdate {
+
+    List<IPPrefix> withdrawnPrefixes = new ArrayList<>();
+    List<PathAttribute> attributes = new ArrayList<>();
+    List<IPPrefix> prefixes = new ArrayList<>();
+
+    public BGPUpdate(byte[] message) {
+        int routesLength = ((message[0] & 0xFF) << 8) | (message[1] & 0xFF);
+        int offset = 2;
+        int offsetOffset = 2;
+        while ((offset - offsetOffset) < routesLength) {
+            IPPrefix prefix = new IPPrefix()
+                    .setLength(message[offset])
+                    .setAddress(new byte[4]);
+            offset++;
+            int addressLen = (int) Math.ceil(prefix.getLength() / 8d);
+            System.arraycopy(message, offset, prefix.getAddress(), 0, addressLen);
+            offset += addressLen;
+            withdrawnPrefixes.add(prefix);
+        }
+        int attributesLength = ((message[offset] & 0xFF) << 8) | (message[offset + 1] & 0xFF);
+        offset += 2;
+        offsetOffset = offset;
+        while ((offset - offsetOffset) < attributesLength) {
+            byte flags = message[offset];
+            byte typeCode = message[offset + 1];
+            int length = message[offset + 2] & 0xFF;
+            offset += 3;
+            if((flags & 0b0001_0000) > 0) {
+                length <<= 8;
+                length |= message[offset] & 0xFF;
+                offset++;
+            }
+            byte[] data = new byte[length];
+            System.arraycopy(message, offset, data, 0, length);
+            offset += length;
+            attributes.add(PathAttribute.from(typeCode, data));
+        }
+        while (offset < message.length) {
+            IPPrefix prefix = new IPPrefix()
+                    .setLength(message[offset])
+                    .setAddress(new byte[4]);
+            offset++;
+            int addressLen = (int) Math.ceil(prefix.getLength() / 8d);
+            System.arraycopy(message, offset, prefix.getAddress(), 0, addressLen);
+            offset += addressLen;
+            prefixes.add(prefix);
+        }
+    }
+
+}
-- 
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