Add better connection algorithms and choices

src/main/java/com/trilead/ssh2/Connection.java

@@ -564,29 +564,75 @@ private void close(Throwable t, boolean hard)
 
 	/**
 	 * Same as
-		 * @return see comments for the
-		 *         {@link #connect(ServerHostKeyVerifier, int, int) connect(ServerHostKeyVerifier, int, int)}
-		 *         method.
-		 * @throws IOException on error
-		 */
+	 * {@link #connect(ServerHostKeyVerifier, int, int, IpVersion) connect(null, 0, 0, IpVersion.IPV4_AND_IPV6)}.
+	 *
+	 * @return see comments for the
+	 *         {@link #connect(ServerHostKeyVerifier, int, int, IpVersion) connect(ServerHostKeyVerifier, int, int, IpVersion)}
+	 *         method.
+	 * @throws IOException on error
+	 */
 	public synchronized ConnectionInfo connect() throws IOException
 	{
-		return connect(null, 0, 0);
+		return connect(null, 0, 0, IpVersion.IPV4_AND_IPV6);
 	}
 
 	/**
 	 * Same as
-	 * {@link #connect(ServerHostKeyVerifier, int, int) connect(verifier, 0, 0)}.
+	 * {@link #connect(ServerHostKeyVerifier, int, int, IpVersion) connect(null, 0, 0, ipVersion)}.
 	 *
 	 * @return see comments for the
-	 *         {@link #connect(ServerHostKeyVerifier, int, int) connect(ServerHostKeyVerifier, int, int)}
+	 *         {@link #connect(ServerHostKeyVerifier, int, int, IpVersion) connect(ServerHostKeyVerifier, int, int, IpVersion)}
+	 *         method.
+	 * @throws IOException
+	 */
+	public synchronized ConnectionInfo connect(IpVersion ipVersion) throws IOException
+	{
+		return connect(null, 0, 0, ipVersion);
+	}
+
+
+	/**
+	 * Same as
+	 * {@link #connect(ServerHostKeyVerifier, int, int, IpVersion) connect(verifier, 0, 0, IpVersion.IPV4_AND_IPV6)}.
+	 *
+	 * @return see comments for the
+	 *         {@link #connect(ServerHostKeyVerifier, int, int, IpVersion) connect(ServerHostKeyVerifier, int, int, IpVersion)}
 	 *         method.
 	 * @param verifier the verifier
 	 * @throws IOException on error
 	 */
 	public synchronized ConnectionInfo connect(ServerHostKeyVerifier verifier) throws IOException
 	{
-		return connect(verifier, 0, 0);
+		return connect(verifier, 0, 0, IpVersion.IPV4_AND_IPV6);
+	}
+
+	/**
+	 * Same as
+	 * {@link #connect(ServerHostKeyVerifier, int, int, IpVersion) connect(verifier, 0, 0, ipVersion)}.
+	 *
+	 * @return see comments for the
+	 *         {@link #connect(ServerHostKeyVerifier, int, int, IpVersion) connect(ServerHostKeyVerifier, int, int, IpVersion)}
+	 *         method.
+	 * @throws IOException
+	 */
+	public synchronized ConnectionInfo connect(ServerHostKeyVerifier verifier, IpVersion ipVersion) throws IOException
+	{
+		return connect(verifier, 0, 0, ipVersion);
+	}
+
+	/**
+	 * Same as
+	 * {@link #connect(ServerHostKeyVerifier, int, int, IpVersion) connect(verifier, connectTimeout, kexTimeout, IpVersion.IPV4_AND_IPV6)}.
+	 *
+	 * @return see comments for the
+	 *         {@link #connect(ServerHostKeyVerifier, int, int, IpVersion) connect(ServerHostKeyVerifier, int, int, IpVersion)}
+	 *         method.
+	 * @throws IOException
+	 */
+	public synchronized ConnectionInfo connect(ServerHostKeyVerifier verifier, int connectTimeout, int kexTimeout)
+		throws IOException
+	{
+		return connect(verifier, connectTimeout, kexTimeout, IpVersion.IPV4_AND_IPV6);
 	}
 
 	/**
@@ -648,6 +694,11 @@ public synchronized ConnectionInfo connect(ServerHostKeyVerifier verifier) throw
 	 *            but it will only have an effect after the
 	 *            <code>verifier</code> returns.
 	 *
+	 * @param ipVersion
+	 *            Specify whether the connection should be restricted to one of
+	 *            IPv4 or IPv6, with a default of allowing both. See
+	 *            {@link IpVersion}.
+	 *
 	 * @return A {@link ConnectionInfo} object containing the details of the
 	 *         established connection.
 	 *
@@ -671,7 +722,7 @@ public synchronized ConnectionInfo connect(ServerHostKeyVerifier verifier) throw
 	 *             proxy is buggy and does not return a proper HTTP response,
 	 *             then a normal IOException is thrown instead.
 	 */
-	public synchronized ConnectionInfo connect(ServerHostKeyVerifier verifier, int connectTimeout, int kexTimeout)
+	public synchronized ConnectionInfo connect(ServerHostKeyVerifier verifier, int connectTimeout, int kexTimeout, IpVersion ipVersion)
 			throws IOException
 	{
 		final class TimeoutState
@@ -746,7 +797,7 @@ public void run()
 
 			try
 			{
-				tm.initialize(cryptoWishList, verifier, dhgexpara, connectTimeout, getOrCreateSecureRND(), proxyData);
+				tm.initialize(cryptoWishList, verifier, dhgexpara, connectTimeout, ipVersion, getOrCreateSecureRND(), proxyData);
 			}
 			catch (SocketTimeoutException se)
 			{

src/main/java/com/trilead/ssh2/IpVersion.java

@@ -0,0 +1,12 @@
+
+package com.trilead.ssh2;
+
+/**
+ * Allow the caller to restrict the IP version of the connection to
+ * be established.
+ */
+public enum IpVersion {
+	IPV4_AND_IPV6,
+	IPV4_ONLY,
+	IPV6_ONLY
+}