ServerProxyAcceptor implementation for Mina SSHD. Tested with sshd-core 1.3.0 & 1.4.0 - https://issues.apache.org/jira/browse/SSHD-656

ProxyProtocolAcceptor.java

/**
 * 
 * A working prototype to support PROXY protocol as described 
 * @see <a href="http://www.haproxy.org/download/1.8/doc/proxy-protocol.txt">HAProxy Documentation</a>
 * 
 * Feel free to improve and integrate to the core library, just include my name as contributor  :
 * Tony Bussieres - tony@codingtony.com
 *
 */
public class ProxyProtocolAcceptor implements ServerProxyAcceptor {

	private static final byte[] PROXY_HEADER = new byte[] { 0x50, 0x52, 0x4F, 0x58, 0x59, 0x20 };
	private Logger logger = LoggerFactory.getLogger(getClass());

	@Override
	public boolean acceptServerProxyMetadata(ServerSession session, Buffer buffer) throws Exception {
		int mark = buffer.rpos();
		if (buffer.available() >= 6) {
			byte[] proxyHeader = new byte[6];
			buffer.getRawBytes(proxyHeader);
			buffer.rpos(mark); // Rewind the buffer
			if (Arrays.equals(PROXY_HEADER, proxyHeader)) {
				logger.debug("PROXY protocol detected");
				// 108 bytes is the largest buffer needed for the PROXY protocol
				StringBuilder proxyPayload = new StringBuilder(108);
				byte n = 0x0;
				// read until we get 0x0d.
				while ((n = buffer.getByte()) != 0x0d) {
					proxyPayload.append((char) n);
				}
				buffer.getByte(); // 0x0a
				logger.debug(proxyPayload.toString());
				String[] proxyFields = proxyPayload.toString().split(" ", -1);
				String proxyProtocolHeader = proxyFields[0];
				String protocol = proxyFields[1];
				if ("TCP4".equals(protocol) || "TCP6".equals(protocol)) {
					String layer3SrcAddress = proxyFields[2];
					String layer3DstAddress = proxyFields[3];
					String layer3SrcPort = proxyFields[4];
					String layer3DstPort = proxyFields[5];
					logger.debug("Header: {}, protocol: {}, src: {}, dst: {}, srcPort: {}, dstPort: {}", proxyProtocolHeader, protocol,
							layer3SrcAddress, layer3DstAddress, layer3SrcPort, layer3DstPort);
					if (session instanceof AbstractServerSession) {
						// Set the client address in the session from the proxy payload 
						((AbstractServerSession) session)
						.setClientAddress(new InetSocketAddress(layer3SrcAddress, Integer.valueOf(layer3SrcPort)));
					}
				} else {
					logger.warn("Proxy Protocol not supported : {}, But still continuing to the login", protocol);
				}
			} 
			return true;
		} else {
			logger.error("Problem with setting up proxy protocol acceptor");
			return false;
		}
	}
}

Now implemented in core : apache/mina-sshd@655e7db#diff-56b8e2be6891753e67159301f4b932c5