`:ssh.daemon` - can't get port tunneling to work (via tcpip_tunnel_in: true)

Questions / Help
,
1

Hello. I’ve noticed the tcpip_tunnel_in option in the Erlang documentation for the ssh module and trying to make it work.

defmodule MyApp.SSHDaemon do
  @sys_dir String.to_charlist("#{Path.expand(".")}/sys_dir")

  def start_link do
    :ssh.daemon(
      4445,
      system_dir: @sys_dir,
      no_auth_needed: true,
      # disconnectfun: &log_it/1,
      # connectfun: &log_it/3,
      # failfun: &log_it/3,
      tcpip_tunnel_in: true
    )
  end

  def child_spec(_) do
    %{
      id: __MODULE__,
      start: {__MODULE__, :start_link, []},
      name: __MODULE__
    }
  end

  def log_it(a1, a2 \\ nil, a3 \\ nil, a4 \\ nil, a5 \\ nil, a6 \\ nil) do
    require Logger

    Logger.debug(
      "#{inspect(a1)}, #{inspect(a2)}, #{inspect(a3)}, #{inspect(a4)}, #{inspect(a5)}, #{inspect(a6)}"
    )
  end
end

Here’s how I’ve generated the sample keys:

mkdir sys_dir
ssh-keygen -N '' -b 256 -t ecdsa -f sys_dir/ssh_host_ecdsa_key

Connecting to it this way:

❯❯❯ ssh -R 8082:localhost:8080 127.0.0.1 -p 4445
Warning: remote port forwarding failed for listen port 8082
Eshell V14.1.1 (press Ctrl+G to abort, type help(). for help)
1>

Any advice or examples on getting TCP port forwarding to work here?

2 Likes
2

Turns out I misunderstood the options and the correct one is tcpip_tunnel_out, not tcpip_tunnel_in. (notice -R in my ssh command usage)

1 Like