package io.undertow.server.protocol.proxy;

import java.net.InetAddress;
import java.net.InetSocketAddress;
import java.net.Socket;
import java.nio.ByteBuffer;
import java.nio.charset.StandardCharsets;

import io.undertow.Undertow;
import io.undertow.server.HttpHandler;
import io.undertow.server.HttpServerExchange;
import io.undertow.testutils.DefaultServer;
import io.undertow.util.FileUtils;
import io.undertow.util.HttpString;
import org.junit.Assert;
import org.junit.Test;

/**
 * Tests the proxy protocol
 *
 * @author Stuart Douglas
 * @author Jan Stourac
 * @author Ulrich Herberg
 */
public class ProxyProtocolTestCase {
    private static final byte[] SIG = new byte[] {0x0D, 0x0A, 0x0D, 0x0A, 0x00, 0x0D, 0x0A, 0x51, 0x55, 0x49, 0x54, 0x0A};
    private static final byte[] NAME = "PROXY ".getBytes(StandardCharsets.US_ASCII);
    private static final byte PROXY = 0x21;
    private static final byte LOCAL = 0x20;
    private static final byte TCPv4 = 0x11;
    private static final byte TCPv6 = 0x21;

    // Undertow with HTTP listener and proxy-protocol enabled
    private Undertow undertow = Undertow.builder().addListener(
            new Undertow.ListenerBuilder()
                    .setType(Undertow.ListenerType.HTTP)
                    .setHost(DefaultServer.getHostAddress())
                    .setUseProxyProtocol(true)
                    .setPort(0)
    ).setHandler(new HttpHandler() {
        @Override
        public void handleRequest(HttpServerExchange exchange) throws Exception {
            exchange.setPersistent(false);
            exchange.getResponseHeaders().put(new HttpString("result"), exchange.getSourceAddress().toString()
                    + " " + exchange.getDestinationAddress().toString());
        }
    }).build();

    // Undertow with HTTPS listener and proxy-protocol enabled
    private Undertow undertowSsl = Undertow.builder().addListener(
            new Undertow.ListenerBuilder()
                    .setType(Undertow.ListenerType.HTTPS)
                    .setSslContext(DefaultServer.getServerSslContext())
                    .setHost(DefaultServer.getHostAddress())
                    .setUseProxyProtocol(true)
                    .setPort(0)
    ).setHandler(new HttpHandler() {
        @Override
        public void handleRequest(HttpServerExchange exchange) throws Exception {
            exchange.setPersistent(false);
            exchange.getResponseHeaders().put(new HttpString("result"), exchange.getSourceAddress().toString()
                    + " " + exchange.getDestinationAddress().toString());
        }
    }).build();

    @Test
    public void testProxyProtocolTcp4() throws Exception {
        // simple valid request
        String request = "PROXY TCP4 1.2.3.4 5.6.7.8 444 555\r\nGET / HTTP/1.0\r\n\r\n";
        String expectedResponse = "result: /1.2.3.4:444 /5.6.7.8:555";
        proxyProtocolRequestResponseCheck(request, expectedResponse);

        // check port range
        request = "PROXY TCP4 1.2.3.4 5.6.7.8 0 65535\r\nGET / HTTP/1.0\r\n\r\n";
        expectedResponse = "result: /1.2.3.4:0 /5.6.7.8:65535";
        proxyProtocolRequestResponseCheck(request, expectedResponse);
    }

    @Test
    public void testProxyProtocolTcp4Negative() throws Exception {
        // wrong number of spaces in requests
        String request = "PROXY  TCP4 1.2.3.4 5.6.7.8 444 555\r\nGET / HTTP/1.0\r\n\r\n";
        proxyProtocolRequestResponseCheck(request, "");

        request = "PROXY TCP4  1.2.3.4 5.6.7.8 444 555\r\nGET / HTTP/1.0\r\n\r\n";
        proxyProtocolRequestResponseCheck(request, "");

        request = "PROXY TCP4 1.2.3.4  5.6.7.8 444 555\r\nGET / HTTP/1.0\r\n\r\n";
        proxyProtocolRequestResponseCheck(request, "");

        request = "PROXY TCP4 1.2.3.4 5.6.7.8  444 555\r\nGET / HTTP/1.0\r\n\r\n";
        proxyProtocolRequestResponseCheck(request, "");

        request = "PROXY TCP4 1.2.3.4 5.6.7.8 444  555\r\nGET / HTTP/1.0\r\n\r\n";
        proxyProtocolRequestResponseCheck(request, "");

        // missing destination port
        request = "PROXY TCP4 1.2.3.4 5.6.7.8 444\r\nGET / HTTP/1.0\r\n\r\n";
        proxyProtocolRequestResponseCheck(request, "");

        // missing destination address
        request = "PROXY TCP4 1.2.3.4 444 555\r\nGET / HTTP/1.0\r\n\r\n";
        proxyProtocolRequestResponseCheck(request, "");

        // missing \n on the first line of the request
        request = "PROXY TCP4 1.2.3.4 5.6.7.8 444 555\rGET / HTTP/1.0\r\n\r\n";
        proxyProtocolRequestResponseCheck(request, "");

        // missing \r on the first line of the request
        request = "PROXY TCP4 1.2.3.4 5.6.7.8 444 555\nGET / HTTP/1.0\r\n\r\n";
        proxyProtocolRequestResponseCheck(request, "");

        // src address contains 0 characters at the beginning
        request = "PROXY TCP4 001.002.003.004 5.6.7.8 444 555\r\nGET / HTTP/1.0\r\n\r\n";
        proxyProtocolRequestResponseCheck(request, "");

        // dst address contains '0' characters at the beginning
        request = "PROXY TCP4 1.2.3.4 005.006.007.008 444 555\r\nGET / HTTP/1.0\r\n\r\n";
        proxyProtocolRequestResponseCheck(request, "");

        // src/dst ports out of range
        request = "PROXY TCP4 1.2.3.4 5.6.7.8 111444 555\r\nGET / HTTP/1.0\r\n\r\n";
        proxyProtocolRequestResponseCheck(request, "");

        request = "PROXY TCP4 1.2.3.4 005.006.007.008 444 111555\r\nGET / HTTP/1.0\r\n\r\n";
        proxyProtocolRequestResponseCheck(request, "");

        request = "PROXY TCP4 1.2.3.4 005.006.007.008 -444 555\r\nGET / HTTP/1.0\r\n\r\n";
        proxyProtocolRequestResponseCheck(request, "");

        request = "PROXY TCP4 1.2.3.4 005.006.007.008 444 -555\r\nGET / HTTP/1.0\r\n\r\n";
        proxyProtocolRequestResponseCheck(request, "");

        // src/dst ports contains '0' characters at the beginning
        request = "PROXY TCP4 1.2.3.4 5.6.7.8 0444 555\r\nGET / HTTP/1.0\r\n\r\n";
        proxyProtocolRequestResponseCheck(request, "");

        request = "PROXY TCP4 1.2.3.4 5.6.7.8 444 0555\r\nGET / HTTP/1.0\r\n\r\n";
        proxyProtocolRequestResponseCheck(request, "");

        // src address contains invalid characters
        request = "PROXY TCP4 277.2.3.4 5.6.7.8 444 555\r\nGET / " + "HTTP/1.0\r\n\r\n";
        proxyProtocolRequestResponseCheck(request, "");

        // dst address contains invalid characters
        request = "PROXY TCP4 1.2.3.4 5d.6.7.8 444 555\r\nGET / " + "HTTP/1.0\r\n\r\n";
        proxyProtocolRequestResponseCheck(request, "");

        // unallowed character after PROXY string
        request = "PROXY, TCP4 1.2.3.4 5.6.7.8 444 555\r\nGET / HTTP/1.0\r\n\r\n";
        proxyProtocolRequestResponseCheck(request, "");

        // IPv6 address when TCP4 is used
        request = "PROXY TCP4 fe80::56ee:75ff:fe44:85bc fe80::5ec5:d4ff:fede:66d8 444 555\r\nGET / HTTP/1.0\r\n\r\n";
        proxyProtocolRequestResponseCheck(request, "");
    }

    @Test
    public void testProxyProtocolTcp6() throws Exception {
        // simple valid request
        String request = "PROXY TCP6 fe80::56ee:75ff:fe44:85bc fe80::5ec5:d4ff:fede:66d8 444 555\r\nGET / " +
                "HTTP/1.0\r\n\r\n";
        String expectedResponse = "result: /fe80:0:0:0:56ee:75ff:fe44:85bc:444 /fe80:0:0:0:5ec5:d4ff:fede:66d8:555";
        proxyProtocolRequestResponseCheck(request, expectedResponse);

        // check port range
        request = "PROXY TCP6 fe80::56ee:75ff:fe44:85bc fe80::5ec5:d4ff:fede:66d8 0 65535\r\nGET / HTTP/1.0\r\n\r\n";
        expectedResponse = "result: /fe80:0:0:0:56ee:75ff:fe44:85bc:0 /fe80:0:0:0:5ec5:d4ff:fede:66d8:65535";
        proxyProtocolRequestResponseCheck(request, expectedResponse);
    }

    @Test
    public void testProxyProtocolTcp6Negative() throws Exception {
        // wrong number of spaces in requests
        String request = "PROXY  TCP6 fe80::56ee:75ff:fe44:85bc fe80::5ec5:d4ff:fede:66d8 444 555\r\nGET / " +
                "HTTP/1.0\r\n\r\n";
        proxyProtocolRequestResponseCheck(request, "");

        request = "PROXY TCP6  fe80::56ee:75ff:fe44:85bc fe80::5ec5:d4ff:fede:66d8 444 555\r\nGET / " +
                "HTTP/1.0\r\n\r\n";
        proxyProtocolRequestResponseCheck(request, "");

        request = "PROXY TCP6 fe80::56ee:75ff:fe44:85bc  fe80::5ec5:d4ff:fede:66d8 444 555\r\nGET / " +
                "HTTP/1.0\r\n\r\n";
        proxyProtocolRequestResponseCheck(request, "");

        request = "PROXY TCP6 fe80::56ee:75ff:fe44:85bc fe80::5ec5:d4ff:fede:66d8  444 555\r\nGET / " +
                "HTTP/1.0\r\n\r\n";
        proxyProtocolRequestResponseCheck(request, "");

        request = "PROXY TCP6 fe80::56ee:75ff:fe44:85bc fe80::5ec5:d4ff:fede:66d8 444  555\r\nGET / " +
                "HTTP/1.0\r\n\r\n";
        proxyProtocolRequestResponseCheck(request, "");

        // missing destination port
        request = "PROXY TCP6 fe80::56ee:75ff:fe44:85bc fe80::5ec5:d4ff:fede:66d8 444\r\nGET / " + "HTTP/1.0\r\n\r\n";
        proxyProtocolRequestResponseCheck(request, "");

        // missing destination address
        request = "PROXY TCP6 fe80::56ee:75ff:fe44:85bc 444 555\r\nGET / " + "HTTP/1.0\r\n\r\n";
        proxyProtocolRequestResponseCheck(request, "");

        // missing \n on the first line of the request
        request = "PROXY TCP6 fe80::56ee:75ff:fe44:85bc fe80::5ec5:d4ff:fede:66d8 444 555\rGET / " + "HTTP/1.0\r\n\r\n";
        proxyProtocolRequestResponseCheck(request, "");

        // missing \r on the first line of the request
        request = "PROXY TCP6 fe80::56ee:75ff:fe44:85bc fe80::5ec5:d4ff:fede:66d8 444 555\nGET / " + "HTTP/1.0\r\n\r\n";
        proxyProtocolRequestResponseCheck(request, "");

        // src address contains invalid characters
        request = "PROXY TCP6 fz80::56ee:75ff:fe44:85bc fe80::5ec5:d4ff:fede:66d8 444 555\r\nGET / " +
                "HTTP/1.0\r\n\r\n";
        proxyProtocolRequestResponseCheck(request, "");

        // dst address contains invalid characters
        request = "PROXY TCP6 fe80::56ee:75ff:fe44:85bc fe80::5zc5:d4ff:fede:66d8 444 555\r\nGET / " +
                "HTTP/1.0\r\n\r\n";
        proxyProtocolRequestResponseCheck(request, "");

        // src/dst ports out of range
        request = "PROXY TCP6 fe80::56ee:75ff:fe44:85bc fe80::5ec5:d4ff:fede:66d8 111444 555\r\nGET / " +
                "HTTP/1.0\r\n\r\n";
        proxyProtocolRequestResponseCheck(request, "");

        request = "PROXY TCP6 fe80::56ee:75ff:fe44:85bc fe80::5ec5:d4ff:fede:66d8 444 111555\r\nGET / " +
                "HTTP/1.0\r\n\r\n";
        proxyProtocolRequestResponseCheck(request, "");

        request = "PROXY TCP6 fe80::56ee:75ff:fe44:85bc fe80::5ec5:d4ff:fede:66d8 -444 555\r\nGET / " +
                "HTTP/1.0\r\n\r\n";
        proxyProtocolRequestResponseCheck(request, "");

        request = "PROXY TCP6 fe80::56ee:75ff:fe44:85bc fe80::5ec5:d4ff:fede:66d8 444 -555\r\nGET / " +
                "HTTP/1.0\r\n\r\n";
        proxyProtocolRequestResponseCheck(request, "");

        // src/dst ports contains '0' characters at the beginning
        request = "PROXY TCP6 fe80::56ee:75ff:fe44:85bc fe80::5ec5:d4ff:fede:66d8 0444 555\r\nGET / " +
                "HTTP/1.0\r\n\r\n";
        proxyProtocolRequestResponseCheck(request, "");

        request = "PROXY TCP6 fe80::56ee:75ff:fe44:85bc fe80::5ec5:d4ff:fede:66d8 444 0555\r\nGET / " +
                "HTTP/1.0\r\n\r\n";
        proxyProtocolRequestResponseCheck(request, "");

        // unallowed character after PROXY string
        request = "PROXY, TCP6 fe80::56ee:75ff:fe44:85bc fe80::5ec5:d4ff:fede:66d8 444 555\r\nGET / " +
                "HTTP/1.0\r\n\r\n";
        proxyProtocolRequestResponseCheck(request, "");

        // IPv6 address when TCP4 is used
        request = "PROXY TCP6 1.2.3.4 5.6.7.8 444 555\r\nGET / HTTP/1.0\r\n\r\n";
        proxyProtocolRequestResponseCheck(request, "");
    }

    /**
     * General negative tests for proxy-protocol. We expect that server closes connection sending no data.
     *
     * @throws Exception
     */
    @Test
    public void testProxyProtocolNegative() throws Exception {
        String request = "NONSENSE\r\n";
        proxyProtocolRequestResponseCheck(request, "");

        request = "NONSENSE TCP4 1.2.3.4 5.6.7.8 444 555\r\nGET / HTTP/1.0\r\n\r\n";
        proxyProtocolRequestResponseCheck(request, "");

        request = "NONSENSE\r\nGET / HTTP/1.0\r\n\r\n";
        proxyProtocolRequestResponseCheck(request, "");

        request = "PROXY\r\n";
        proxyProtocolRequestResponseCheck(request, "");

        request = "PROXY\r\nGET / HTTP/1.0\r\n\r\n";
        proxyProtocolRequestResponseCheck(request, "");

        request = "PROXY NONSENSE\r\n";
        proxyProtocolRequestResponseCheck(request, "");

        request = "PROXY NONSENSE 1.2.3.4 5.6.7.8 444 555\r\nGET / HTTP/1.0\r\n\r\n";
        proxyProtocolRequestResponseCheck(request, "");
    }


    /**
     * Starts an undertow server with HTTP listener and performs request to the server with given request string.
     * Then response from the server is checked with given expected response string. Undertow is stopped in the end.
     *
     * @param request          request string that is send to server
     * @param expectedResponse expected response string that we expect from the server
     * @throws Exception
     */
    private void proxyProtocolRequestResponseCheck(String request, String expectedResponse) throws Exception {
        try {
            undertow.start();
            int port = ((InetSocketAddress) undertow.getListenerInfo().get(0).getAddress()).getPort();
            Socket s = new Socket(DefaultServer.getHostAddress(), port);
            s.getOutputStream().write(request.getBytes(StandardCharsets.US_ASCII));
            String result = FileUtils.readFile(s.getInputStream());
            Assert.assertTrue(result, result.contains(expectedResponse));
        } finally {
            undertow.stop();
        }
    }

    /**
     * Main cases are covered in plain-text HTTP connection tests. So here is just simple check that connection can
     * be established also via HTTPS.
     *
     * @throws Exception
     */
    @Test
    public void testProxyProtocolSSl() throws Exception {
        String request = "PROXY TCP4 1.2.3.4 5.6.7.8 444 555\r\n";
        String requestHttp = "GET / HTTP/1.0\r\n\r\n";
        String expectedResponse = "result: /1.2.3.4:444 /5.6.7.8:555";
        proxyProtocolRequestResponseCheck(request, requestHttp, expectedResponse);

        // negative test
        request = "PROXY TCP4  1.2.3.4 5.6.7.8 444 555\r\n";
        requestHttp = "GET / HTTP/1.0\r\n\r\n";
        proxyProtocolRequestResponseCheck(request, requestHttp, "");
    }

    @Test
    public void testProxyProtocolV2Tcp4() throws Exception {
        // simple valid request
        byte[] header = createProxyHeaderV2(PROXY, TCPv4, 12, InetAddress.getByName("1.2.3.4"), InetAddress.getByName("5.6.7.8"),444,555);

        String requestHttp = "GET / HTTP/1.0\r\n\r\n";
        String expectedResponse = "result: /1.2.3.4:444 /5.6.7.8:555";

        proxyProtocolRequestResponseCheck(header, requestHttp, expectedResponse);

        // check port range
        header = createProxyHeaderV2(PROXY, TCPv4, 12, InetAddress.getByName("1.2.3.4"), InetAddress.getByName("5.6.7.8"),0,65535);
        expectedResponse = "result: /1.2.3.4:0 /5.6.7.8:65535";
        proxyProtocolRequestResponseCheck(header, requestHttp, expectedResponse);

        // check extra len
        header = createProxyHeaderV2(PROXY, TCPv4, 100, InetAddress.getByName("1.2.3.4"), InetAddress.getByName("5.6.7.8"),444,555);
        expectedResponse = "result: /1.2.3.4:444 /5.6.7.8:555";
        proxyProtocolRequestResponseCheck(header, requestHttp, expectedResponse);
    }




    /**
     * Main cases are covered in plain-text HTTP connection tests. So here is just simple check that connection can
     * be established also via HTTPS.
     *
     * @throws Exception
     */
    @Test
    public void testProxyProtocolV2SSl() throws Exception {
        // simple valid request
        byte[] header = createProxyHeaderV2(PROXY, TCPv4, 12, InetAddress.getByName("1.2.3.4"), InetAddress.getByName("5.6.7.8"),444,555);

        String requestHttp = "GET / HTTP/1.0\r\n\r\n";
        String expectedResponse = "result: /1.2.3.4:444 /5.6.7.8:555";


        proxyProtocolRequestResponseCheck(header, requestHttp, expectedResponse);
    }



    @Test
    public void testProxyProtocolV2Tcp4Negative() throws Exception {
        String requestHttp = "GET / HTTP/1.0\r\n\r\n";
        byte[] request;

        // missing destination port
        request = createProxyHeaderV2(PROXY, TCPv4, 10, InetAddress.getByName("1.2.3.4"), InetAddress.getByName("5.6.7.8"),444,null);
        proxyProtocolRequestResponseCheck(request, requestHttp, "");

        // missing destination address
        request = createProxyHeaderV2(PROXY, TCPv4, 8, InetAddress.getByName("1.2.3.4"), null,444,555);
        proxyProtocolRequestResponseCheck(request, requestHttp, "");

        // invalid family
        request = createProxyHeaderV2(PROXY, (byte) 0x42, 12, InetAddress.getByName("1.2.3.4"), InetAddress.getByName("5.6.7.8"),444,555);
        proxyProtocolRequestResponseCheck(request, requestHttp, "");

        // len too low
        request = createProxyHeaderV2(PROXY, TCPv4, 4, InetAddress.getByName("1.2.3.4"), null,null,null);
        proxyProtocolRequestResponseCheck(request, requestHttp, "");
    }

    @Test
    public void testProxyProtocolV2Tcp6() throws Exception {
        String requestHttp = "GET / HTTP/1.0\r\n\r\n";
        byte[] request;

        // simple valid request
        request = createProxyHeaderV2(PROXY, TCPv6, 36, InetAddress.getByName("fe80::56ee:75ff:fe44:85bc"), InetAddress.getByName("fe80::5ec5:d4ff:fede:66d8"),444,555);
        String expectedResponse = "result: /fe80:0:0:0:56ee:75ff:fe44:85bc:444 /fe80:0:0:0:5ec5:d4ff:fede:66d8:555";
        proxyProtocolRequestResponseCheck(request, requestHttp, expectedResponse);

        // check port range
        request = createProxyHeaderV2(PROXY, TCPv6, 36, InetAddress.getByName("fe80::56ee:75ff:fe44:85bc"), InetAddress.getByName("fe80::5ec5:d4ff:fede:66d8"),0,65535);
        expectedResponse = "result: /fe80:0:0:0:56ee:75ff:fe44:85bc:0 /fe80:0:0:0:5ec5:d4ff:fede:66d8:65535";
        proxyProtocolRequestResponseCheck(request, requestHttp, expectedResponse);
    }

    @Test
    public void testProxyProtocolV2Tcp6Negative() throws Exception {
        String requestHttp = "GET / HTTP/1.0\r\n\r\n";
        byte[] request;

        // missing destination port
        request = createProxyHeaderV2(PROXY, TCPv6, 34, InetAddress.getByName("fe80::56ee:75ff:fe44:85bc"), InetAddress.getByName("fe80::5ec5:d4ff:fede:66d8"),444,null);
        proxyProtocolRequestResponseCheck(request, requestHttp, "");

        // missing destination address
        request = createProxyHeaderV2(PROXY, TCPv6, 20, InetAddress.getByName("1.2.3.4"), null,444,555);
        proxyProtocolRequestResponseCheck(request, requestHttp, "");

        // invalid family
        request = createProxyHeaderV2(PROXY, (byte) 0x42, 36, InetAddress.getByName("fe80::56ee:75ff:fe44:85bc"), InetAddress.getByName("fe80::5ec5:d4ff:fede:66d8"),444,555);
        proxyProtocolRequestResponseCheck(request, requestHttp, "");

        // len too low
        request = createProxyHeaderV2(PROXY, TCPv6, 16, InetAddress.getByName("fe80::56ee:75ff:fe44:85bc"), null,null,null);
        proxyProtocolRequestResponseCheck(request, requestHttp, "");
    }

    @Test
    public void testProxyProtocolV2Local() throws Exception {
        String requestHttp = "GET / HTTP/1.0\r\n\r\n";
        byte[] request;

        // simple valid request
        request = createProxyHeaderV2(LOCAL, (byte) 0, 0, null, null,null,null);
        String expectedResponse;
        if (isIpV6()) {
            expectedResponse = "result: /0:0:0:0:0:0:0:1";
        } else {
            expectedResponse = "result: /127.0.0.1";
        }
        proxyProtocolRequestResponseCheck(request, requestHttp, expectedResponse);
    }

    /**
     * General negative tests for proxy-protocol. We expect that server closes connection sending no data.
     *
     * @throws Exception
     */
    @Test
    public void testProxyProtocolV2Negative() throws Exception {
        String requestHttp = "GET / HTTP/1.0\r\n\r\n";
        byte[] request;

        // wrong version
        request = createProxyHeaderV2((byte) 0, TCPv4, 12, InetAddress.getByName("1.2.3.4"), InetAddress.getByName("5.6.7.8"),444,555);
        proxyProtocolRequestResponseCheck(request, requestHttp, "");

        // wrong signature (starting with NAME)
        request = new byte[]{NAME[0], 0x0, 0x0, 0x0};
        proxyProtocolRequestResponseCheck(request, requestHttp, "");

        // wrong signature (starting with SIG)
        request = new byte[]{SIG[0], 0x0, 0x0, 0x0};
        proxyProtocolRequestResponseCheck(request, requestHttp, "");

        // wrong signature (starting with 0x0)
        request = new byte[]{0x0, 0x0, 0x0, 0x0};
        proxyProtocolRequestResponseCheck(request, requestHttp, "");
    }



    private static byte[] createProxyHeaderV2(Byte ver_cmd, Byte family, Integer len, InetAddress sourceAddress, InetAddress destAddress, Integer sourcePort, Integer destPort) {
        ByteBuffer buffer = ByteBuffer.allocate(16 + len);
        buffer.put(SIG);

        if (ver_cmd != null) {
            buffer.put((byte) (ver_cmd & 0xff)); // ver=2: V2, cmd=1: PROXY / 2: LOCAL
        }
        if (family != null) {
            buffer.put((byte) (family & 0xff)); // 0x11: TCPv4 / 0x21: TCPv6
        }
        if (len != null) {
            buffer.putShort((short) (len & 0xffff)); // len=12
        }
        if (sourceAddress != null) {
            buffer.put(sourceAddress.getAddress());
        }
        if (destAddress != null) {
            buffer.put(destAddress.getAddress());
        }
        if (sourcePort != null) {
            buffer.putShort((short) (sourcePort & 0xffff));
        }
        if (destPort != null) {
            buffer.putShort((short) (destPort & 0xffff));
        }

        return buffer.array();
    }

    /**
     * Starts an undertow server with HTTPS listener and performs request to the server with given request proxy
     * string and HTTP request. Then response from the server is checked with given expected response string.
     * Undertow is stopped in the end.
     *
     * @param requestProxy     request string with proxy-protocol part
     * @param requestHttp      request string with HTTP part
     * @param expectedResponse expected response string that we expect from the server
     * @throws Exception
     */
    private void proxyProtocolRequestResponseCheck(String requestProxy, String requestHttp, String expectedResponse)
            throws Exception {
        proxyProtocolRequestResponseCheck(requestProxy.getBytes(StandardCharsets.US_ASCII), requestHttp, expectedResponse);
    }

    /**
     * Starts an undertow server with HTTP listener and performs request to the server with given request string.
     * Then response from the server is checked with given expected response string. Undertow is stopped in the end.
     *
     * @param request          request string that is send to server
     * @param expectedResponse expected response string that we expect from the server
     * @throws Exception
     */
    private void proxyProtocolRequestResponseCheck(byte[] request, String requestHttp, String expectedResponse) throws Exception {
        try {
            undertow.start();
            int port = ((InetSocketAddress) undertow.getListenerInfo().get(0).getAddress()).getPort();
            Socket s = new Socket(DefaultServer.getHostAddress(), port);
            s.getOutputStream().write(request);
            // if expectedResponse is empty, we expect server to close connection due to bad request
            if (!expectedResponse.isEmpty()) {
                s.getOutputStream().write(requestHttp.getBytes(StandardCharsets.US_ASCII));
            }
            String result = FileUtils.readFile(s.getInputStream());
            Assert.assertTrue(result, result.contains(expectedResponse));
        } finally {
            undertow.stop();
        }
    }


    @Test
    public void testProxyProtocolUnknownEmpty() throws Exception {
        doTestProxyProtocolUnknown("");
    }

    @Test
    public void testProxyProtocolUnknownSpace() throws Exception {
        doTestProxyProtocolUnknown(" ");
    }

    @Test
    public void testProxyProtocolUnknownJunk() throws Exception {
        doTestProxyProtocolUnknown(" mekmitasdigoat");
    }

    /**
     * Starts an undertow server with HTTP listener and performs request to the server with request proxy with
     * UNKNOWN protocol string and HTTP request. Then response from the server is checked with given expected
     * response string. Undertow is stopped in the end.
     *
     * @param extra extra content added after protocol type - "UNKNOWN" - server should ignore this information
     * @throws Exception
     */
    public void doTestProxyProtocolUnknown(String extra) throws Exception {
        try {
            undertow.start();
            InetSocketAddress serverAddress = (InetSocketAddress) undertow.getListenerInfo().get(0).getAddress();
            Socket s = new Socket(serverAddress.getAddress(), serverAddress.getPort());
            String expected = String.format("result: /%s:%d /%s:%d", s.getLocalAddress().getHostAddress(), s
                    .getLocalPort(), serverAddress.getAddress().getHostAddress(), serverAddress.getPort());
            s.getOutputStream().write(("PROXY UNKNOWN" + extra + "\r\nGET / HTTP/1.0\r\n\r\n").getBytes
                    (StandardCharsets.US_ASCII));
            String result = FileUtils.readFile(s.getInputStream());
            Assert.assertTrue(result, result.contains(expected));
        } finally {
            undertow.stop();
        }
    }

    private static boolean isIpV6() {
        String preferIpV6Property = System.getProperty("java.net.preferIPv6Addresses");
        return preferIpV6Property != null && preferIpV6Property.toLowerCase().equals("true");
    }
}
