Implement AS4 capability

Specified in RFC 6793.

6 files changed, 133 insertions, 20 deletions

diff --git a/src/main/java/com/lumaserv/bgp/BGPFsm.java b/src/main/java/com/lumaserv/bgp/BGPFsm.java
index 7929d36..9bfc30b 100644
--- a/src/main/java/com/lumaserv/bgp/BGPFsm.java
+++ b/src/main/java/com/lumaserv/bgp/BGPFsm.java
@@ -8,6 +8,7 @@ import lombok.Getter;
 import lombok.Setter;
 
 import java.io.IOException;
+import java.util.Optional;
 import java.util.Timer;
 import java.util.TimerTask;
 
@@ -277,7 +278,15 @@ public class BGPFsm {
         @Override
         void openMsg(BGPOpen msg) {
             System.out.println("openMsg:" + msg);
-            if(session.getConfiguration().getRemoteAs() == msg.getAsn()) {
+
+            Optional<BGPOpen.AS4Capability> as4Opt =
+                msg.getAS4Capability();
+            int remoteAsn = session.getConfiguration().getRemoteAs();
+            int openAsn = as4Opt.isPresent()
+                ? as4Opt.get().getAsn()
+                : msg.getAsn();
+
+            if(remoteAsn == openAsn) {
                 // - resets the DelayOpenTimer to zero,
                 // - sets the BGP ConnectRetryTimer to zero,
                 session.keepAlive();
@@ -290,8 +299,14 @@ public class BGPFsm {
                 setState(OPEN_CONFIRM);
             } else {
                 System.out.println("Bad asn");
-                //  - sends a NOTIFICATION message with the appropriate error code,
-                // - sets the ConnectRetryTimer to zero,
+                try {
+                    BGPNotification notification = new BGPNotification()
+                        .setMajorErrorCode(BGPNotification.Error.OPEN_MESSAGE_ERROR.getCode())
+                        .setMinorErrorCode(BGPNotification.OpenMessageError.BAD_PEER_AS.getCode());
+                    session.sendNotification(notification);
+                } catch (IOException ex) {
+                }
+                setConnectRetryTimer(0);
                 // - releases all BGP resources,
                 session.dropConnection();
                 connectRetryCounter++;
diff --git a/src/main/java/com/lumaserv/bgp/BGPSession.java b/src/main/java/com/lumaserv/bgp/BGPSession.java
index c6a8cd2..bb38ebf 100644
--- a/src/main/java/com/lumaserv/bgp/BGPSession.java
+++ b/src/main/java/com/lumaserv/bgp/BGPSession.java
@@ -29,6 +29,9 @@ public class BGPSession implements Runnable {
     boolean outgoing;
     BGPFsm fsm;
     Thread thread;
+    boolean isAdvAS4Capability;
+    @Getter
+    boolean isAS4Capability;
 
     public BGPSession(Socket socket, BGPSessionConfiguration configuration, BGPFsm fsm) throws IOException {
         this.configuration = configuration;
@@ -75,10 +78,11 @@ public class BGPSession implements Runnable {
                 break;
             case OPEN:
                 BGPOpen open = new BGPOpen(packet.getMessage());
+                isAS4Capability = isAdvAS4Capability && open.getAS4Capability().isPresent();
                 fsm.getCurrentState().openMsg(open);
                 break;
             case UPDATE: {
-                BGPUpdate update = new BGPUpdate(packet.getMessage());
+                BGPUpdate update = new BGPUpdate(this, packet.getMessage());
                 fsm.getCurrentState().updateMsg(update);
                 configuration.getListener().onUpdate(this, update);
                 break;
@@ -103,6 +107,7 @@ public class BGPSession implements Runnable {
     }
 
     void sendOpen(BGPOpen request) throws IOException {
+        isAdvAS4Capability = request.getAS4Capability().isPresent();
         outputStream.write(new BGPPacket().setType(BGPPacket.Type.OPEN).setMessage(request.build()).build());
 System.out.println("Sent open");
     }
@@ -111,12 +116,14 @@ System.out.println("Sent open");
         BGPOpen.Capabilities caps = new BGPOpen.Capabilities();
         caps.getCapabilities().add(new BGPOpen.MultiprotocolExtensionCapability(AFI.IPV4.getValue(), SAFI.UNICAST.getValue()));
         caps.getCapabilities().add(new BGPOpen.MultiprotocolExtensionCapability(AFI.IPV6.getValue(), SAFI.UNICAST.getValue()));
+        caps.getCapabilities().add(new BGPOpen.AS4Capability(configuration.getLocalAs()));
 
         BGPOpen request = new BGPOpen()
-            .setAsn(configuration.getLocalAs())
             .setHoldTime(BGPFsm.CONFIG_HOLD_TIME)
             .setVersion(BGPFsm.CONFIG_VERSION)
             .setIdentifier(configuration.getLocalIdentifier());
+        if ((configuration.getLocalAs() & 0xFFFFFFFFL) < 0xFFFF)
+            request.setAsn(configuration.getLocalAs());
         request.getOptionalParameters().add(caps);
 
         sendOpen(request);
diff --git a/src/main/java/com/lumaserv/bgp/protocol/attribute/ASPathAttribute.java b/src/main/java/com/lumaserv/bgp/protocol/attribute/ASPathAttribute.java
index 6405924..c4c6962 100644
--- a/src/main/java/com/lumaserv/bgp/protocol/attribute/ASPathAttribute.java
+++ b/src/main/java/com/lumaserv/bgp/protocol/attribute/ASPathAttribute.java
@@ -1,5 +1,7 @@
 package com.lumaserv.bgp.protocol.attribute;
 
+import com.lumaserv.bgp.BGPSession;
+
 import lombok.Getter;
 import lombok.Setter;
 
@@ -12,14 +14,27 @@ public class ASPathAttribute implements PathAttribute {
 
     List<Segment> segments = new ArrayList<>();
 
-    public ASPathAttribute(byte typeCode, byte[] data) {
+    public ASPathAttribute(BGPSession session, byte typeCode, byte[] data) {
+        final boolean isAS4 = session.isAS4Capability();
+        final int asnLen = isAS4 ? 4 : 2;
         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);
+            for(int i=0; i<length; i++) {
+                int asn;
+                if (isAS4) {
+                    asn = ((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);
+                } else {
+                    asn = (((data[offset + 2 + (i * 2)] & 0xFF) << 8)
+                           | (data[offset + 3 + (i * 2)] & 0xFF));
+                }
+                segment.asns.add(asn);
+            }
+            offset += 2 + (length * asnLen);
             segments.add(segment);
         }
     }
@@ -45,7 +60,7 @@ public class ASPathAttribute implements PathAttribute {
             for(Integer asn : asns) {
                 if (buf.length() > 1)
                     buf.append(" ");
-                buf.append(asn);
+                buf.append((long)asn & 0xFFFFFFFFL);
             }
             buf.append(")");
             return buf.toString();
diff --git a/src/main/java/com/lumaserv/bgp/protocol/attribute/PathAttribute.java b/src/main/java/com/lumaserv/bgp/protocol/attribute/PathAttribute.java
index 1ba5ce4..06bbed5 100644
--- a/src/main/java/com/lumaserv/bgp/protocol/attribute/PathAttribute.java
+++ b/src/main/java/com/lumaserv/bgp/protocol/attribute/PathAttribute.java
@@ -1,16 +1,18 @@
 package com.lumaserv.bgp.protocol.attribute;
 
+import com.lumaserv.bgp.BGPSession;
+
 public interface PathAttribute {
 
     byte getTypeCode();
     byte[] build();
 
-    static PathAttribute from(byte typeCode, byte[] data) {
+    static PathAttribute from(BGPSession session, byte typeCode, byte[] data) {
         switch (typeCode & 0xFF) {
             case 1:
                 return new OriginAttribute(typeCode, data);
             case 2:
-                return new ASPathAttribute(typeCode, data);
+                return new ASPathAttribute(session, typeCode, data);
             case 3:
                 return new NextHopAttribute(typeCode, data);
             case 6:
diff --git a/src/main/java/com/lumaserv/bgp/protocol/message/BGPOpen.java b/src/main/java/com/lumaserv/bgp/protocol/message/BGPOpen.java
index ae4e32a..4937e1b 100644
--- a/src/main/java/com/lumaserv/bgp/protocol/message/BGPOpen.java
+++ b/src/main/java/com/lumaserv/bgp/protocol/message/BGPOpen.java
@@ -7,7 +7,9 @@ import lombok.Setter;
 
 import java.nio.ByteBuffer;
 import java.util.ArrayList;
+import java.util.EnumSet;
 import java.util.List;
+import java.util.Optional;
 
 @Getter
 @Setter
@@ -21,7 +23,7 @@ public class BGPOpen {
     List<Parameter> optionalParameters = new ArrayList<>();
 
     @Getter
-    enum ParameterType {
+    public enum ParameterType {
         CAPABILITIES(2);
 
         byte type;
@@ -31,7 +33,7 @@ public class BGPOpen {
         }
     }
 
-    interface Parameter {
+    public interface Parameter {
         byte getType();
         int getValue(byte[] dst, int offset);
     }
@@ -77,6 +79,12 @@ public class BGPOpen {
             return offset - first;
         }
 
+        public Optional<Capability> getCapability(Capability.Code capabilityCode) {
+            return capabilities.stream()
+                .filter(c -> c.getCode() == capabilityCode.getCode())
+                .findAny();
+        }
+
         Capabilities(byte[] src, int offset, int length) {
             int first = offset;
             while ((offset - first) < length) {
@@ -85,6 +93,8 @@ public class BGPOpen {
 
                 if (code == Capability.Code.MULTIPROTOCOL_EXTENSION.getCode()) {
                     capabilities.add(new MultiprotocolExtensionCapability(src, offset, capLength));
+                } else if (code == Capability.Code.AS4.getCode()) {
+                    capabilities.add(new AS4Capability(src, offset, capLength));
                 } else {
                     byte[] value = new byte[capLength];
                     System.arraycopy(src, offset, value, 0, capLength);
@@ -112,16 +122,31 @@ public class BGPOpen {
         }
     }
 
-    interface Capability {
+    public interface Capability {
         @Getter
         enum Code {
-            MULTIPROTOCOL_EXTENSION(1);
+            MULTIPROTOCOL_EXTENSION(1),
+            ROUTE_REFRESH(2),
+            EXTENDED_NEXT_HOP(5),
+            GRACEFUL_RESTART(64),
+            AS4(65),
+            ENHANCED_ROUTE_REFRESH(70),
+            LONG_LIVED_GRACEFUL_RESTART(71);
 
             byte code;
 
             Code(int code) {
                 this.code = (byte)code;
             }
+
+            public static Code fromInt(int code) {
+                return EnumSet
+                    .allOf(Code.class)
+                    .stream()
+                    .filter(e -> e.getCode() == code)
+                    .findAny()
+                    .orElseThrow(() -> new IllegalArgumentException("unknown capability: " + code));
+            }
         }
 
         byte getCode();
@@ -142,7 +167,7 @@ public class BGPOpen {
 
         @Override
         public String toString() {
-            return "Unknown{code=" + code + ", length=" + value.length + "}";
+            return "Unknown{code=" + Code.fromInt(code) + ", length=" + value.length + "}";
         }
     }
 
@@ -178,8 +203,41 @@ public class BGPOpen {
         }
     }
 
+    @AllArgsConstructor
+    @Getter
+    public static class AS4Capability implements Capability {
+        int asn;
+
+        @Override
+        public byte getCode() { return Capability.Code.AS4.getCode(); }
+
+        @Override
+        public int getValue(byte[] dst, int offset) {
+            dst[offset] = (byte)((asn >> 24) & 0xFF);
+            dst[offset + 1] = (byte)((asn >> 16) & 0xFF);
+            dst[offset + 2] = (byte)((asn >> 8) & 0xFF);
+            dst[offset + 3] = (byte)(asn & 0xFF);
+            return 4;
+        }
+
+        AS4Capability(byte[] src, int offset, int length) {
+            if (length != 4) {
+                throw new RuntimeException("Bad AS4Capability");
+            }
+
+            asn = ((src[offset] & 0xFF) << 24)
+                | ((src[offset + 1] & 0xFF) << 16)
+                | ((src[offset + 2] & 0xFF) << 8)
+                | (src[offset + 3] & 0xFF);
+        }
+
+        @Override
+        public String toString() {
+            return "as4: " + (asn & 0xFFFFFFFFL);
+        }
+    }
+
     public BGPOpen(ByteBuffer message) {
-System.out.println("BGPOpen pos:" + message.position());
         version = message.get();
         asn = message.getShort() & 0xFFFF;
         holdTime = message.getShort() & 0xFFFF;
@@ -210,6 +268,21 @@ System.out.println("BGPOpen pos:" + message.position());
         this(ByteBuffer.wrap(message));
     }
 
+    public Optional<Parameter> getOptionalParameter(ParameterType type) {
+        return optionalParameters.stream()
+            .filter(o -> o.getType() == type.getType())
+            .findAny();
+    }
+
+    public Optional<Capability> getCapability(Capability.Code capabilityCode) {
+        Capabilities caps = (Capabilities)getOptionalParameter(BGPOpen.ParameterType.CAPABILITIES).orElse(new Capabilities());
+        return caps.getCapability(capabilityCode);
+    }
+
+    public Optional<AS4Capability> getAS4Capability() {
+        return getCapability(Capability.Code.AS4).map(c -> (AS4Capability)c);
+    }
+
     public byte[] build() {
         ByteBuffer buf = ByteBuffer.allocate(256);
         build(buf);
diff --git a/src/main/java/com/lumaserv/bgp/protocol/message/BGPUpdate.java b/src/main/java/com/lumaserv/bgp/protocol/message/BGPUpdate.java
index fa23432..f5af399 100644
--- a/src/main/java/com/lumaserv/bgp/protocol/message/BGPUpdate.java
+++ b/src/main/java/com/lumaserv/bgp/protocol/message/BGPUpdate.java
@@ -1,5 +1,6 @@
 package com.lumaserv.bgp.protocol.message;
 
+import com.lumaserv.bgp.BGPSession;
 import com.lumaserv.bgp.protocol.IPPrefix;
 import com.lumaserv.bgp.protocol.attribute.PathAttribute;
 import lombok.Getter;
@@ -16,7 +17,7 @@ public class BGPUpdate {
     List<PathAttribute> attributes = new ArrayList<>();
     List<IPPrefix> prefixes = new ArrayList<>();
 
-    public BGPUpdate(byte[] message) {
+    public BGPUpdate(BGPSession session, byte[] message) {
         int routesLength = ((message[0] & 0xFF) << 8) | (message[1] & 0xFF);
         int offset = 2;
         int offsetOffset = 2;
@@ -46,7 +47,7 @@ public class BGPUpdate {
             byte[] data = new byte[length];
             System.arraycopy(message, offset, data, 0, length);
             offset += length;
-            attributes.add(PathAttribute.from(typeCode, data));
+            attributes.add(PathAttribute.from(session, typeCode, data));
         }
         while (offset < message.length) {
             IPPrefix prefix = new IPPrefix()