Add support for specifying IP version #332

ppb2020 · 2025-01-01T20:10:51Z

Added new signatures to the connect method of the Connection class to allow the caller to restrict the IP version of the connection to be established. The new signatures duplicate existing signatures and add one parameter. For backwards compatibility, the default for the new parameter is IPv4 and IPv6, while the new values are "IPv4 only" and "IPv6 only".

ppb2020 · 2025-01-16T21:56:48Z

Shall I submit the connectbot change that depends on this right away or wait until this change is accepted and integrated? I don't want to submit a change to connectbot that will cause the builds to fail because and updated version of sshlib is not yet available...

Copilot

Pull request overview

This PR adds support for restricting SSH connections to specific IP versions (IPv4-only, IPv6-only, or both) by introducing an IpVersion enum and new connect() method signatures.

Key Changes:

Added IpVersion enum to Connection and TransportManager classes with three options: IPV4_AND_IPV6 (default), IPV4_ONLY, and IPV6_ONLY
Extended connect() methods in Connection class with overloads accepting an ipVersion parameter
Implemented IP address filtering logic in TransportManager to enforce the IP version restriction

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 9 comments.

File	Description
src/main/java/com/trilead/ssh2/Connection.java	Added IpVersion enum and four new connect() method overloads with ipVersion parameter; updated existing methods to delegate with default IPV4_AND_IPV6 value; added enum mapping logic to convert Connection.IpVersion to TransportManager.IpVersion
src/main/java/com/trilead/ssh2/transport/TransportManager.java	Added IpVersion enum and helper methods getIPv4Address/getIPv6Address to filter addresses; modified connectDirect() and establishConnection() to accept and use ipVersion parameter; updated initialize() signature to include ipVersion

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Copilot · 2025-12-16T01:04:25Z

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

+	public synchronized ConnectionInfo connect(IpVersion ipVersion) throws IOException
+	{
+		return connect(null, 0, 0, ipVersion);
 	}

+
 	/**
 	 * Same as
-	 * {@link #connect(ServerHostKeyVerifier, int, int) connect(verifier, 0, 0)}.
+	 * {@link #connect(ServerHostKeyVerifier, int, int, IpVersion) connect(verifier, 0, 0, IpVersion.IPV4_AND_IPV6)}.
 	 *
 	 * @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(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);
 	}


Missing API documentation: The IpVersion parameter is not documented in overload methods. The new connect overloads at lines 598, 627, and 641 don't document the ipVersion parameter even though they accept it. Only the main connect method at line 734 has documentation for this parameter. For consistency and API clarity, all public methods that accept the ipVersion parameter should document it.

Copilot · 2025-12-16T01:04:26Z

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

+	 * @param ipVersion
+	 *            Specify whether the connection should be restricted to one of
+	 *            IPv4 or IPv6, with a default of allowing both. See
+	 *            {@link IpVersion}.


Missing feature documentation: The IP version restriction feature is not documented in the main method Javadoc. The parameter is documented, but there's no mention of limitations (e.g., that ipVersion is ignored when using a proxy connection). Consider adding a note in the documentation explaining when ipVersion applies and when it doesn't.

Suggested change

* {@link IpVersion}.

* {@link IpVersion}. <b>Note:</b> This parameter is ignored if a proxy connection is used

* (i.e., if {@link #setProxyData(ProxyData)} has been called); in that case, the proxy

* determines the IP version used for the connection.

Copilot · 2025-12-16T01:04:26Z

src/main/java/com/trilead/ssh2/transport/TransportManager.java

+		else // Assume (ipVersion == IpVersion.IPV4_AND_IPV6), the default.
+		{
+			addr = InetAddress.getByName(hostname);
+		}


Null pointer exception risk: When ipVersion is IPV4_ONLY or IPV6_ONLY, getIPv4Address or getIPv6Address may return null if the hostname doesn't resolve to that IP version. The null address will cause a NullPointerException when passed to InetSocketAddress constructor. Add null check and throw an IOException with a clear error message explaining that the hostname doesn't resolve to the requested IP version.

Suggested change

}

}

if (addr == null) {

throw new IOException("The hostname '" + hostname + "' does not resolve to the requested IP version: " + ipVersion);

}

Copilot · 2025-12-16T01:04:26Z

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

+		IPV4_AND_IPV6, ///< Allow both IPV4 and IPv6, the default.
+		IPV4_ONLY,     ///< Require that the connection be over IPv4 only.
+		IPV6_ONLY      ///< Require that the connection be over IPv6 only.


C-style comments are not idiomatic in Java. The codebase uses Javadoc-style comments (/** ... */) for documentation. These inline comments after enum values should either be removed or converted to proper Javadoc comments above each enum value, following the pattern used elsewhere in the codebase for documenting class members.

Suggested change

IPV4_AND_IPV6, ///< Allow both IPV4 and IPv6, the default.

IPV4_ONLY, ///< Require that the connection be over IPv4 only.

IPV6_ONLY ///< Require that the connection be over IPv6 only.

/**

* Allow both IPV4 and IPv6, the default.

*/

IPV4_AND_IPV6,

/**

* Require that the connection be over IPv4 only.

*/

IPV4_ONLY,

/**

* Require that the connection be over IPv6 only.

*/

IPV6_ONLY

Copilot · 2025-12-16T01:04:27Z

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

+			TransportManager.IpVersion tmIpVersion;
+			if (ipVersion == IpVersion.IPV4_ONLY)
+			{
+				tmIpVersion = TransportManager.IpVersion.IPV4_ONLY;
+			}
+			else if (ipVersion == IpVersion.IPV6_ONLY) {
+				tmIpVersion = TransportManager.IpVersion.IPV6_ONLY;
+			}
+			else // Assume (ipVersion == IpVersion.IPV4_AND_IPV6), the default.
+			{
+				tmIpVersion = TransportManager.IpVersion.IPV4_AND_IPV6;
+			}


Duplicate enum definition: The IpVersion enum is defined identically in both Connection and TransportManager classes. This violates the DRY principle and creates a maintenance burden. Consider defining the enum once in a shared location (e.g., in Connection as the public API) and having TransportManager reference it directly, or create a shared constants class. The current approach requires maintaining two identical enums and manual conversion code (lines 807-818).

Copilot · 2025-12-16T01:04:27Z

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

 				token = TimeoutService.addTimeoutHandler(timeoutHorizont, timeoutHandler);
 			}

+			TransportManager.IpVersion tmIpVersion;


Missing input validation: The ipVersion parameter is not validated for null. If a caller passes null for ipVersion, the code will fail with a NullPointerException at line 808. Consider adding a null check and either throwing an IllegalArgumentException with a clear message or defaulting to IPV4_AND_IPV6.

Suggested change

TransportManager.IpVersion tmIpVersion;

TransportManager.IpVersion tmIpVersion;

// Default to IPV4_AND_IPV6 if ipVersion is null

if (ipVersion == null) {

ipVersion = IpVersion.IPV4_AND_IPV6;

}

Copilot · 2025-12-16T01:04:27Z

src/main/java/com/trilead/ssh2/transport/TransportManager.java

-	private static Socket connectDirect(String hostname, int port, int connectTimeout)
+	private static Socket connectDirect(String hostname, int port, int connectTimeout, IpVersion ipVersion)
 			throws IOException
 	{


Missing input validation: The ipVersion parameter is not validated for null. If a caller passes null for ipVersion, the code will fail with a NullPointerException at line 309. Consider adding a null check and either throwing an IllegalArgumentException with a clear message or defaulting to IPV4_AND_IPV6.

Suggested change

{

{

if (ipVersion == null) {

ipVersion = IpVersion.IPV4_AND_IPV6;

}

Copilot · 2025-12-16T01:04:27Z

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

+	public synchronized ConnectionInfo connect(IpVersion ipVersion) throws IOException
+	{
+		return connect(null, 0, 0, ipVersion);
 	}

+
 	/**
 	 * Same as
-	 * {@link #connect(ServerHostKeyVerifier, int, int) connect(verifier, 0, 0)}.
+	 * {@link #connect(ServerHostKeyVerifier, int, int, IpVersion) connect(verifier, 0, 0, IpVersion.IPV4_AND_IPV6)}.
 	 *
 	 * @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(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);
 	}


Missing test coverage: The new IpVersion feature and all the new connect() method overloads lack test coverage. The repository has comprehensive integration tests (OpenSSHCompatibilityTest, DropbearCompatibilityTest) that test connection functionality, but none test the IPv4-only, IPv6-only, or default behavior of the new ipVersion parameter. Consider adding tests to verify: 1) connections work correctly with each IpVersion value, 2) appropriate errors are thrown when a hostname doesn't resolve to the requested IP version, and 3) backwards compatibility with existing code that doesn't specify ipVersion.

Copilot · 2025-12-16T01:04:28Z

src/main/java/com/trilead/ssh2/transport/TransportManager.java

+		IPV4_AND_IPV6, ///< Allow both IPV4 and IPv6, the default.
+		IPV4_ONLY,     ///< Require that the connection be over IPv4 only.
+		IPV6_ONLY      ///< Require that the connection be over IPv6 only.


C-style comments are not idiomatic in Java. The codebase uses Javadoc-style comments (/** ... */) for documentation. These inline comments after enum values should either be removed or converted to proper Javadoc comments above each enum value, following the pattern used elsewhere in the codebase for documenting class members.

Suggested change

IPV4_AND_IPV6, ///< Allow both IPV4 and IPv6, the default.

IPV4_ONLY, ///< Require that the connection be over IPv4 only.

IPV6_ONLY ///< Require that the connection be over IPv6 only.

/**

* Allow both IPV4 and IPv6, the default.

*/

IPV4_AND_IPV6,

/**

* Require that the connection be over IPv4 only.

*/

IPV4_ONLY,

/**

* Require that the connection be over IPv6 only.

*/

IPV6_ONLY

ppb2020 mentioned this pull request Jan 1, 2025

Host option to force IPv4 connectbot/connectbot#693

Open

kruton force-pushed the main branch from 437988a to b9f7296 Compare April 15, 2025 16:09

Add support for specifying IP version

9690d15

kruton force-pushed the main branch from b9f7296 to 9690d15 Compare April 15, 2025 19:26

Merge branch 'main' into main

84f5905

kruton requested a review from Copilot December 16, 2025 00:59

Copilot started reviewing on behalf of kruton December 16, 2025 01:00 View session

Copilot AI reviewed Dec 16, 2025

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Add support for specifying IP version #332

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-	 *            {@link IpVersion}.
+	 *            {@link IpVersion}. <b>Note:</b> This parameter is ignored if a proxy connection is used
+	 *            (i.e., if {@link #setProxyData(ProxyData)} has been called); in that case, the proxy
+	 *            determines the IP version used for the connection.

-		}
+		}
+		if (addr == null) {
+			throw new IOException("The hostname '" + hostname + "' does not resolve to the requested IP version: " + ipVersion);
+		}

-			TransportManager.IpVersion tmIpVersion;
+			TransportManager.IpVersion tmIpVersion;
+			// Default to IPV4_AND_IPV6 if ipVersion is null
+			if (ipVersion == null) {
+				ipVersion = IpVersion.IPV4_AND_IPV6;
+			}

Add support for specifying IP version #332

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