Add collision detection

2 files changed, 127 insertions, 6 deletions

diff --git a/src/main/java/com/lumaserv/bgp/BGPServer.java b/src/main/java/com/lumaserv/bgp/BGPServer.java
index 80ec7ff..e95caea 100644
--- a/src/main/java/com/lumaserv/bgp/BGPServer.java
+++ b/src/main/java/com/lumaserv/bgp/BGPServer.java
@@ -1,6 +1,7 @@
 package com.lumaserv.bgp;
 
 import com.lumaserv.bgp.protocol.BGPPacket;
+import com.lumaserv.bgp.protocol.message.BGPNotification;
 import com.lumaserv.bgp.protocol.message.BGPOpen;
 import lombok.Getter;
 
@@ -39,6 +40,77 @@ public class BGPServer implements Runnable {
         return true;
     }
 
+    public boolean hasCollided(BGPSession session, BGPOpen msg) {
+        for (BGPSession otherSession : sessions) {
+            BGPFsm fsm = otherSession.getFsm();
+            BGPFsm.State state = fsm.getCurrentState();
+
+            // May examine OPEN_SENT
+            if (state == fsm.OPEN_SENT
+                && otherSession.getConfiguration() == null)
+                continue;
+
+            // Cannot detect collision
+            if (state == fsm.IDLE
+                || state == fsm.CONNECT
+                || state == fsm.ACTIVE)
+                continue;
+
+            // Detect collision
+            if (session.getInetAddress() != otherSession.getLocalAddress()
+                || session.getLocalAddress() != otherSession.getInetAddress())
+                continue;
+
+            // Collision!
+            if (state == fsm.ESTABLISHED) {
+                // Close new connection
+                sessions.remove(session);
+                return true;
+            }
+
+            byte[] remoteIdentifier;
+            byte[] localIdentifier = session.getConfiguration()
+                .getLocalIdentifier();
+
+            if (state == fsm.OPEN_SENT) {
+                remoteIdentifier = otherSession.getConfiguration()
+                    .getRemoteIdentifier();
+            } else { // state == BGPFsm.OPEN_CONFIRM
+                remoteIdentifier = otherSession.getRemoteIdentifier();
+            }
+
+            boolean isLocalIdLess = false;
+
+            // Compare integer stored in network byte order
+            for (int i=0; i < 4; i++) {
+                if (localIdentifier[i] < remoteIdentifier[i]) {
+                    isLocalIdLess = true;
+                    break;
+                }
+            }
+
+            if (isLocalIdLess) {
+                // Close existing connection
+                BGPNotification notification = new BGPNotification()
+                    .setMajorErrorCode(BGPNotification.Error.CEASE.getCode());
+                try {
+                    otherSession.sendNotification(notification);
+                } catch(IOException ex) {
+                }
+                sessions.remove(otherSession);
+                otherSession.dropConnection();
+                // Accept new connection
+                return false;
+            } else {
+                // Close new connection
+                sessions.remove(session);
+                return true;
+            }
+        }
+
+        return false;
+    }
+
     public void run() {
         while (true) {
             try {
@@ -57,7 +129,7 @@ public class BGPServer implements Runnable {
                 }
 
                 BGPFsm fsm = new BGPFsm();
-                BGPSession session = new BGPSession(socket, config, fsm);
+                BGPSession session = new BGPSession(this, socket, config, fsm);
                 fsm.setSession(session);
                 sessions.add(session);
                 System.out.println("automaticStartPassive");
@@ -66,6 +138,8 @@ public class BGPServer implements Runnable {
                 // System.out.println("tcpConnectionConfirmed in " + fsm.getCurrentState());
                 // fsm.getCurrentState().tcpConnectionConfirmed();
             } catch (IOException ex) {
+                if (serverSocket.isClosed())
+                    break;
                 ex.printStackTrace();
             }
         }
@@ -76,9 +150,16 @@ public class BGPServer implements Runnable {
     }
 
     public boolean connect(BGPSessionConfiguration config, String host, int port) throws IOException {
+        for (BGPSession session : sessions) {
+            if (session.getConfiguration().equals(config)) {
+                // Already connected
+                return false;
+            }
+        }
+
         try {
             BGPFsm fsm = new BGPFsm();
-            BGPSession session = new BGPSession(config, fsm, host, port);
+            BGPSession session = new BGPSession(this, config, fsm, host, port);
             fsm.setSession(session);
             sessions.add(session);
             fsm.getCurrentState().automaticStart();
@@ -93,5 +174,13 @@ public class BGPServer implements Runnable {
         for(BGPSession session : sessions) {
             session.automaticStop();
         }
+        sessions.clear();
+        if (serverSocket != null) {
+            try {
+                serverSocket.close();
+            } 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
index bb38ebf..e785e3b 100644
--- a/src/main/java/com/lumaserv/bgp/BGPSession.java
+++ b/src/main/java/com/lumaserv/bgp/BGPSession.java
@@ -11,6 +11,7 @@ import lombok.Getter;
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.OutputStream;
+import java.net.InetAddress;
 import java.net.InetSocketAddress;
 import java.net.Socket;
 import java.net.SocketException;
@@ -18,6 +19,8 @@ import java.net.SocketException;
 public class BGPSession implements Runnable {
 
     @Getter
+    final BGPServer server;
+    @Getter
     final BGPSessionConfiguration configuration;
     final String host;
     final int port;
@@ -27,13 +30,17 @@ public class BGPSession implements Runnable {
     @Getter
     boolean closed;
     boolean outgoing;
+    @Getter
     BGPFsm fsm;
     Thread thread;
     boolean isAdvAS4Capability;
     @Getter
     boolean isAS4Capability;
+    @Getter
+    byte[] remoteIdentifier;
 
-    public BGPSession(Socket socket, BGPSessionConfiguration configuration, BGPFsm fsm) throws IOException {
+    public BGPSession(BGPServer server, Socket socket, BGPSessionConfiguration configuration, BGPFsm fsm) throws IOException {
+        this.server = server;
         this.configuration = configuration;
         this.socket = socket;
         this.inputStream = socket.getInputStream();
@@ -43,13 +50,26 @@ public class BGPSession implements Runnable {
         this.port = -1;
     }
 
-    public BGPSession(BGPSessionConfiguration configuration, BGPFsm fsm, String host, int port) throws IOException {
+    public BGPSession(BGPServer server, BGPSessionConfiguration configuration, BGPFsm fsm, String host, int port) throws IOException {
+        this.server = server;
         this.configuration = configuration;
         this.fsm = fsm;
         this.host = host;
         this.port = port;
     }
 
+    public InetAddress getInetAddress() {
+        return socket.getInetAddress();
+    }
+
+    public InetAddress getLocalAddress() {
+        return socket.getLocalAddress();
+    }
+
+    protected void finalize() throws Throwable {
+        System.out.println("Finalize BGPSession");
+    }
+
     public void automaticStop() {
         fsm.getCurrentState().automaticStop();
     }
@@ -78,8 +98,20 @@ public class BGPSession implements Runnable {
                 break;
             case OPEN:
                 BGPOpen open = new BGPOpen(packet.getMessage());
-                isAS4Capability = isAdvAS4Capability && open.getAS4Capability().isPresent();
-                fsm.getCurrentState().openMsg(open);
+                if (server.hasCollided(this, open)) {
+                    BGPNotification notification = new BGPNotification()
+                        .setMajorErrorCode(BGPNotification.Error.CEASE.getCode());
+                    try {
+                        sendNotification(notification);
+                    } catch(IOException ex) {
+                    }
+                    dropConnection();
+                    // TODO Break links between fsm and session!
+                } else {
+                    isAS4Capability = isAdvAS4Capability && open.getAS4Capability().isPresent();
+                    remoteIdentifier = open.getIdentifier();
+                    fsm.getCurrentState().openMsg(open);
+                }
                 break;
             case UPDATE: {
                 BGPUpdate update = new BGPUpdate(this, packet.getMessage());