Adding bind address pre-check before starting the default proxy

browserup-proxy-core/src/main/java/com/browserup/bup/BrowserUpProxyServer.java

@@ -530,7 +530,7 @@ public InetAddress getClientBindAddress() {
     @Override
     public int getPort() {
         if (started.get()) {
-            return proxyServer.getListenAddress().getPort();
+            return (proxyServer != null ?  proxyServer.getListenAddress().getPort() : 0);
         } else {
             return 0;
         }

browserup-proxy-rest/src/main/java/com/browserup/bup/exception/AddressInUseException.java

@@ -0,0 +1,46 @@
+/*
+ * Modifications Copyright (c) 2019 BrowserUp, Inc.
+ */
+
+package com.browserup.bup.exception;
+
+import java.net.InetAddress;
+
+public class AddressInUseException extends RuntimeException {
+
+	private static final long serialVersionUID = -2548760680049910435L;
+	private final int port;
+	private final InetAddress address;
+
+    public AddressInUseException(int port, InetAddress bindAddress) {
+        this.port = port;
+        this.address = bindAddress;
+    }
+
+    public AddressInUseException(String message, int port, InetAddress bindAddress) {
+        super(message);
+        this.port = port;
+        this.address = bindAddress;
+    }
+
+    public AddressInUseException(String message, Throwable cause, int port, InetAddress bindAddress) {
+        super(message, cause);
+        this.port = port;
+        this.address = bindAddress;
+    }
+
+    public AddressInUseException(Throwable cause, int port, InetAddress bindAddress) {
+        super(cause);
+        this.port = port;
+        this.address = bindAddress;
+    }
+
+    public int getPort() {
+        return port;
+    }
+
+	public InetAddress getAddress() {
+		return address;
+	}
+
+}

browserup-proxy-rest/src/main/java/com/browserup/bup/proxy/ProxyManager.java

@@ -5,6 +5,7 @@
 package com.browserup.bup.proxy;
 
 import com.browserup.bup.BrowserUpProxyServer;
+import com.browserup.bup.exception.AddressInUseException;
 import com.browserup.bup.exception.ProxyExistsException;
 import com.browserup.bup.exception.ProxyPortsExhaustedException;
 import com.browserup.bup.proxy.auth.AuthType;
@@ -19,9 +20,11 @@
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
+import java.io.IOException;
 import java.lang.ref.WeakReference;
 import java.net.InetAddress;
 import java.net.InetSocketAddress;
+import java.net.Socket;
 import java.net.URISyntaxException;
 import java.net.UnknownHostException;
 import java.util.Collection;
@@ -217,8 +220,48 @@ public BrowserUpProxyServer create(String upstreamHttpProxy, boolean upstreamPro
         }
         throw new ProxyPortsExhaustedException();
     }
+
+    /**
+     * Check that the Port is Available to bind to.
+     * 
+     * We need to verify that the port isn't already bound to on the client bind address.
+     * The application by default assumes that the min-max ports are reserved, however 
+     * in a mixed environment there may be some stray ports that are being used by 
+     * other services. 
+     * 
+     * This method will verify that the port isn't already bound by trying 
+     * to bind to it and then closing it. 
+     * 
+     * If the port is already bound it will throw a run-time exception.
+     * 
+     * @param clientBindAddress the bind address to check, can be null which is a wildcard
+     * @param port the port to attempt to bind to with the bind address
+     */
+    private void checkPortAvailability(InetAddress clientBindAddress, Integer port) {
 
-    public BrowserUpProxyServer create(String upstreamHttpProxy, String proxyUsername, String proxyPassword, Integer port, String bindAddr, boolean useEcc, boolean trustAllServers) {
+        InetSocketAddress testClientBindSocket;
+
+        // Use the wildcard address if the clientBindAddress isn't specified
+        if (clientBindAddress == null) {
+        	testClientBindSocket = new InetSocketAddress(port);
+        } else {
+        	testClientBindSocket = new InetSocketAddress(clientBindAddress, port);
+        }
+
+        // Use a test socket to attempt binding with
+        try(Socket testSocket = new Socket()) {
+        	testSocket.bind(testClientBindSocket);
+        } catch (IOException e) {
+        	// Assume that the port cannot be bound to, log a warning and then return False
+            LOG.error("Bind address unavailable: " + testClientBindSocket.toString(), e);
+            throw new AddressInUseException(e, port, clientBindAddress);            
+		}
+
+        // Log that the bind address is available
+        LOG.debug("Bind address available {}", testClientBindSocket);
+	}
+
+	public BrowserUpProxyServer create(String upstreamHttpProxy, String proxyUsername, String proxyPassword, Integer port, String bindAddr, boolean useEcc, boolean trustAllServers) {
         return create(upstreamHttpProxy, false, null, proxyUsername, proxyPassword, port, null, null, false, false);
     }
 
@@ -249,6 +292,7 @@ private BrowserUpProxyServer startProxy(BrowserUpProxyServer proxy, int port, In
                 LOG.info("Proxy already exists at port {}", port);
                 throw new ProxyExistsException(port);
             }
+            checkPortAvailability(clientBindAddr, port);            
         }
 
         try {

browserup-proxy-rest/src/test/java/com/browserup/bup/proxy/ProxyPortAssignmentTest.java

@@ -7,7 +7,12 @@
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.fail;
 
+import java.io.IOException;
+import java.net.InetSocketAddress;
+import java.net.Socket;
+
 import com.browserup.bup.BrowserUpProxyServer;
+import com.browserup.bup.exception.AddressInUseException;
 import com.browserup.bup.exception.ProxyExistsException;
 import com.browserup.bup.exception.ProxyPortsExhaustedException;
 import com.browserup.bup.proxy.test.util.ProxyManagerTest;
@@ -57,4 +62,26 @@ public void testManualAssignment() {
             proxyManager.delete(9094);
         }
     }
-}
+
+    @Test
+    public void testBindFailure() {
+
+    	int testPort = 9094;
+
+        InetSocketAddress testClientBindSocket = new InetSocketAddress(testPort);
+
+        // Use a test socket to attempt binding with
+        try(Socket testSocket = new Socket()) {
+        	testSocket.bind(testClientBindSocket);	
+	        try{
+	            proxyManager.create(9094);
+	            fail();
+	        }catch(AddressInUseException e){
+	            assertEquals(9094, e.getPort());
+	        }
+        } catch (IOException e1) {
+			e1.printStackTrace();
+        	fail();
+		}
+    }
+}