Need some help for using Port Forward feature

[ireallylikeher]

Hi all, here is an issue I bump into while using the WebSocketNamespacedPodPortForwardAsync() in the client.

My usecase is that I want to create a tunnel between the local port and the ssh port (22) on the pod. I try using the Kubectl port-forward command, and it's working just fine. When I try using the port-forward function from the Kubernetes's client, things are not working properly.

Here is the ssh debug logging when I try to ssh into the pod:

//
OpenSSH_9.1p1, OpenSSL 1.1.1s 1 Nov 2022
debug1: Reading configuration data /c/Users/LeeTony(USAC-ER)/.ssh/config
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: Connecting to 127.0.0.1 [127.0.0.1] port 22001.
debug1: Connection established.
debug1: identity file /c/Users/LeeTony(USAC-ER)/.ssh/id_rsa type -1
debug1: identity file /c/Users/LeeTony(USAC-ER)/.ssh/id_rsa-cert type -1
debug1: identity file /c/Users/LeeTony(USAC-ER)/.ssh/id_ecdsa type -1
debug1: identity file /c/Users/LeeTony(USAC-ER)/.ssh/id_ecdsa-cert type -1
debug1: identity file /c/Users/LeeTony(USAC-ER)/.ssh/id_ecdsa_sk type -1
debug1: identity file /c/Users/LeeTony(USAC-ER)/.ssh/id_ecdsa_sk-cert type -1
debug1: identity file /c/Users/LeeTony(USAC-ER)/.ssh/id_ed25519 type -1
debug1: identity file /c/Users/LeeTony(USAC-ER)/.ssh/id_ed25519-cert type -1
debug1: identity file /c/Users/LeeTony(USAC-ER)/.ssh/id_ed25519_sk type -1
debug1: identity file /c/Users/LeeTony(USAC-ER)/.ssh/id_ed25519_sk-cert type -1
debug1: identity file /c/Users/LeeTony(USAC-ER)/.ssh/id_xmss type -1
debug1: identity file /c/Users/LeeTony(USAC-ER)/.ssh/id_xmss-cert type -1
debug1: identity file /c/Users/LeeTony(USAC-ER)/.ssh/id_dsa type -1
debug1: identity file /c/Users/LeeTony(USAC-ER)/.ssh/id_dsa-cert type -1
debug1: Local version string SSH-2.0-OpenSSH_9.1
debug1: Remote protocol version 2.0, remote software version OpenSSH_8.9p1 Ubuntu-3ubuntu0.4
debug1: compat_banner: match: OpenSSH_8.9p1 Ubuntu-3ubuntu0.4 pat OpenSSH compat 0x04000000
debug1: Authenticating to 127.0.0.1:22001 as 'tonylee'
debug1: load_hostkeys: fopen /c/Users/LeeTony(USAC-ER)/.ssh/known_hosts2: No such file or directory
debug1: load_hostkeys: fopen /etc/ssh/ssh_known_hosts: No such file or directory
debug1: load_hostkeys: fopen /etc/ssh/ssh_known_hosts2: No such file or directory
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
debug1: kex: algorithm: sntrup761x25519-sha512@openssh.com
debug1: kex: host key algorithm: ssh-ed25519
debug1: kex: server->client cipher: chacha20-poly1305@openssh.com MAC: compression: none
debug1: kex: client->server cipher: chacha20-poly1305@openssh.com MAC: compression: none
debug1: expecting SSH2_MSG_KEX_ECDH_REPLY
/*/

It seems like the connection does get established, but it just stuck on waiting for the response of "SSH2_MSG_KEX_ECDH_REPLY". I tried googling the issue and tried what people suggested, but it still didn't work.
I am wondering if anyone has similar issue or knows what kind of issues it is and could point me to a direction.
Thank you all.

[tg123]

sdk should work the same as kubectl

from you ssh log, seems the connection stuck. did you test other algo?

[ireallylikeher]

sdk should work the same as kubectl

from you ssh log, seems the connection stuck. did you test other algo?

Thank you for the reply.
Yes, I did try other key algorithms/cipher, which what people suggested online, and it didn't work. However, with the kubectl command, I did not need to use different algo/cipher.

[tg123]

ok allow me some time to repro and see if any bug in sdk
thanks for reporting

[ireallylikeher]

ok allow me some time to repro and see if any bug in sdk thanks for reporting

Thank you so much!

[brendandburns]

Can you send your port forwarding code? Did you see the example here:

https://github.com/kubernetes-client/csharp/blob/master/examples/portforward/PortForward.cs#L41

Are you making sure to spawn multiple threads to handle the reading/writing simultaneously in both directions? Also you need to make sure there's no contention between those threads.

[IvanJosipovic]

I have been working on a new port forwarder that you can try. Once I get it stabilized, I will PR it over here.

using k8s;
using System.Net.NetworkInformation;
using System.Net;
using System.Net.Sockets;

namespace KubeUI.Core.Client;

public class PortForwarder
{
    IKubernetes client;

    TcpListener listener;

    public string PodName { get; }

    public string Namespace { get; }

    public int ContainerPort { get; }

    public int LocalPort { get; }

    public string Status { get; private set; }

    public PortForwarder(IKubernetes client, string podName, string @namespace, int containerPort, int localPort)
    {
        this.client = client;
        PodName = podName;
        Namespace = @namespace;
        ContainerPort = containerPort;
        LocalPort = localPort;

        listener = new TcpListener(IPAddress.Loopback, localPort);
    }

    public void Start()
    {
        if (!IsPortAvailable(LocalPort))
        {
            Status = "Local port is busy";
            return;
        }

        listener.Start();

        listener.BeginAcceptSocket(new AsyncCallback(ClientConnected), null);
        Status = "Active";
    }

    public void Stop()
    {
        listener.Stop();
        Status = "Inactive";
    }

    private void ClientConnected(IAsyncResult result)
    {
        var socket = listener.EndAcceptSocket(result);

        Task.Run(async () => await HandleConnection(socket));

        listener.BeginAcceptSocket(new AsyncCallback(ClientConnected), null);
    }

    private async Task HandleConnection(Socket socket)
    {
        using var webSocket = await client.WebSocketNamespacedPodPortForwardAsync(PodName, Namespace, new int[] { ContainerPort }, "v4.channel.k8s.io");
        using var demux = new StreamDemuxer(webSocket, StreamType.PortForward);
        demux.Start();

        using var stream = demux.GetStream((byte?)0, (byte?)0);

        var read = Task.Run(() =>
        {
            var buffer = new byte[4096];
            while (SocketConnected(socket))
            {
                var bytesReceived = socket.Receive(buffer);
                stream.Write(buffer, 0, bytesReceived);
            }
        });

        var write = Task.Run(() =>
        {
            var buffer = new byte[4096];
            while (SocketConnected(socket))
            {
                var bytesReceived = stream.Read(buffer, 0, 4096);
                socket.Send(buffer, bytesReceived, 0);
            }
        });

        await read;
        await write;

        socket.Close();
    }

    private static bool IsPortAvailable(int port)
    {
        var properties = IPGlobalProperties.GetIPGlobalProperties();
        var activeTcpListeners = properties.GetActiveTcpListeners();
        return !activeTcpListeners.Any(x => x.Port == port);
    }

    private static bool SocketConnected(Socket s)
    {
        var part1 = s.Poll(1000, SelectMode.SelectRead);
        var part2 = s.Available == 0;
        if (part1 && part2)
            return false;
        else
            return true;
    }
}

[ireallylikeher]

Can you send your port forwarding code? Did you see the example here:

https://github.com/kubernetes-client/csharp/blob/master/examples/portforward/PortForward.cs#L41

Are you making sure to spawn multiple threads to handle the reading/writing simultaneously in both directions? Also you need to make sure there's no contention between those threads.

Here is the port forwarded code I used. I had to cleanup the stuff that were not relevant.

using k8s;
using Serilog;
using System;
using System.Collections.Generic;
using System.IO;
using System.Net;
using System.Net.Sockets;
using System.Threading;
using System.Threading.Tasks;

namespace VWAC.VirtualVehicles.Support
{
    public class ForwardedPort : IDisposable
    {
        private const int ReceiveBufferSize = 0xFFFF;
        private const int SendBufferSize = 0xFFFF;
        private readonly List<TcpConnection> _tcpConnections = new();
        private readonly CancellationTokenSource _instanceCts = new CancellationTokenSource();
        private TcpListener _tcpListener;

        public ForwardedPort(int localPort)
        {
            LocalPort = localPort;
        }

        public Guid Id { get; }

        public Guid ServiceId { get; }

        public Guid VehicleId { get; }

        public string TargetNodeName { get; }

        public string TargetProtocol { get; }

        public int? TargetPort { get; }

        public int LocalPort { get; }

        public void Initialize()
        {
            _tcpListener = new TcpListener(IPAddress.Loopback, LocalPort);
            _tcpListener.Start();
            _ = Task.Factory.StartNew(RunTcpListener);
        }

        private async Task RunTcpListener()
        {
            while (!_instanceCts.IsCancellationRequested)
            {
                TcpClient tcpClient = null;
                TcpConnection tcpConnection = null;
                try
                {
                    tcpClient = await _tcpListener.AcceptTcpClientAsync();
                    tcpClient.NoDelay = true;
                    tcpClient.ReceiveBufferSize = ReceiveBufferSize;
                    tcpClient.SendBufferSize = SendBufferSize;
                    tcpConnection = new TcpConnection { TcpClient = tcpClient, PodSocketStream = await GetPodStream(), Stream = tcpClient.GetStream() };
                    tcpConnection.TunnelReceiveTask = Task.Factory.StartNew(() => RunTcpReceiveTunnel(tcpConnection));
                    tcpConnection.TunnelSendTask = Task.Factory.StartNew(() => RunTcpSendTunnel(tcpConnection));
                    lock (_tcpConnections)
                        _tcpConnections.Add(tcpConnection);
                }
                catch (Exception ex)
                {
                    // TODO: Setup better handling + logging
                    if (tcpClient != null)
                    {
                        tcpClient.Dispose();
                    }
                    if (tcpConnection != null)
                        tcpConnection.Dispose();
                }
            }
        }

        private async Task RunTcpSendTunnel(TcpConnection tcpConnection)
        {
            using var cancellationTokenSource = CancellationTokenSource.CreateLinkedTokenSource(_instanceCts.Token, tcpConnection.ConnectionCancellationToken);
            try
            {
                await RunTcpTunnel(new byte[SendBufferSize], tcpConnection.Stream, tcpConnection.PodSocketStream, cancellationTokenSource.Token);
            }
            catch
            {
                tcpConnection.Cancel();
                // TODO: Setup better handling + logging and closing of the connection
            }
            finally
            {
                tcpConnection.Dispose(); // Only need to dispose once, so the send tunnel does it
            }
            lock (_tcpConnections)
                _tcpConnections.Remove(tcpConnection);
        }

        private async Task RunTcpReceiveTunnel(TcpConnection tcpConnection)
        {
            using var cancellationTokenSource = CancellationTokenSource.CreateLinkedTokenSource(_instanceCts.Token, tcpConnection.ConnectionCancellationToken);
            try
            {
                await RunTcpTunnel(new byte[ReceiveBufferSize], tcpConnection.PodSocketStream, tcpConnection.Stream, cancellationTokenSource.Token);
            }
            catch
            {
                tcpConnection.Cancel();
                // TODO: Setup better handling + logging and closing of the connection
            }
            finally
            {
                //await tcpConnection.DisposeAsync(); // Only need to dispose once, so the send tunnel does it
            }
            lock (_tcpConnections)
                _tcpConnections.Remove(tcpConnection);
        }

        private static async Task RunTcpTunnel(byte[] buffer, Stream readStream, Stream writeStream, CancellationToken cancellationToken = default)
        {
            while (!cancellationToken.IsCancellationRequested)
            {
                var readAmount = await readStream.ReadAsync(buffer, 0, buffer.Length, cancellationToken);
                if (readAmount <= 0)
                {
                    break;
                }
                await writeStream.WriteAsync(buffer, 0, readAmount, cancellationToken);
            }
        }

        private async Task<Stream> GetPodStream()
        {
            var config = KubernetesClientConfiguration.BuildConfigFromConfigFile();
            var client = new Kubernetes(config);
            var webSocket = await client.WebSocketNamespacedPodPortForwardAsync("vv-4321f07e-124f-4b3f-b8e3-5402074c2c19-0", "virtual-vehicle", new int[] { 22 }, "v4.channel.k8s.io");

            var demux = new StreamDemuxer(webSocket, StreamType.PortForward);
            demux.Start();
            var stream = demux.GetStream((byte?)0, (byte?)0);
            return stream;
        }

        public void Dispose()
        {
            Dispose(true);
            GC.SuppressFinalize(this);
        }

        protected virtual void Dispose(bool disposing)
        {
            // Determine if waiting for tcp listener task to complete is necessary
            _tcpListener.Stop();
            _instanceCts.Cancel();
            TcpConnection[] connections;
            lock (_tcpConnections)
                connections = _tcpConnections.ToArray();
            foreach (var tcpConnection in connections)
                tcpConnection.Dispose();
            _instanceCts.Dispose();
        }

        private class TcpConnection : IDisposable
        {
            private readonly CancellationTokenSource _connectionCts = new();

            public CancellationToken ConnectionCancellationToken => _connectionCts.Token;

            public TcpClient TcpClient { get; set; }

            public Task TunnelReceiveTask { get; set; }

            public Task TunnelSendTask { get; set; }

            public Stream PodSocketStream { get; set; }

            public NetworkStream Stream { get; set; }

            public void Cancel()
            {
                try
                {
                    _connectionCts.Cancel();
                }
                catch (Exception ex)
                {
                    Log.Error(ex, "Cancel Error");
                }
            }

            public void Dispose()
            {
                Dispose(true);
                GC.SuppressFinalize(this);
            }

            protected virtual void Dispose(bool disposing)
            {
                // TODO: Determine if waiting for tunnel receive/send task completion is necessary
                try
                {
                    _connectionCts.Dispose();
                }
                catch (Exception ex)
                {
                    Log.Error(ex, "connectionCts Dispose Error");
                }
                TcpClient.Close();
                TcpClient.Dispose();

                Stream.Dispose();
            }
        }
    }
}

[ireallylikeher]

@IvanJosipovic Thank you. I will give it a try.

[ireallylikeher]

@IvanJosipovic Good news!! The code you provided totally works!!! I am wondering what are the changes that make it working?
Thank you very much again!

[tg123]

thanks all, could you please send a pr of working example code?