class Net::SSH::Gateway

  1. lib/net/ssh/gateway.rb
Parent: SSH

A Gateway is an object that allows you to tunnel network connections through a publicly visible host to a host hidden behind it. This is particularly useful when dealing with hosts behind a firewall. One host will generally be visible (and accessible) outside the firewall, while the others will all be behind the firewall, and the only way to access those restricted hosts is by first logging into the publicly visible host, and from thence logging into the restricted ones.

This class makes it easy to programmatically connect to these restricted hosts via SSH. You can either simply forward a port from the local host to the remote host, or you can open a new Net::SSH connection to the remote host via a forwarded port.

require 'net/ssh/gateway'

gateway = Net::SSH::Gateway.new('host.name', 'user')

gateway.open('hidden.host', 80) do |port|
  Net::HTTP.get_print '127.0.0.1', '/path', port
end

gateway.ssh('hidden.host', 'user') do |ssh|
  puts ssh.exec!("hostname")
end

gateway.shutdown!

Port numbers are allocated automatically, beginning at MAX_PORT and decrementing on each request for a new port until MIN_PORT is reached. If a port is already in use, this is detected and a different port will be assigned.

Methods

Public Class

  1. new

Public Instance

  1. active?
  2. close
  3. open
  4. shutdown!
  5. ssh

Classes and Modules

  1. Net::SSH::Gateway::Version

Constants

MAX_PORT = 65535  

The maximum port number that the gateway will attempt to use to forward connections from.
MIN_PORT = 1024  

The minimum port number that the gateway will attempt to use to forward connections from.

Public Class methods

new (host, user, options={})

Instantiate a new Gateway object, using the given remote host as the tunnel. The arguments here are identical to those for Net::SSH.start, and are passed as given to that method to start up the gateway connection.

gateway = Net::SSH::Gateway.new('host', 'user', :password => "password")

As of 1.1 there is an additional option to specify the wait time for the gateway thread. The default is 0.001 seconds and can be changed with the :loop_wait option.

[show source] 
# File lib/net/ssh/gateway.rb, line 73
def initialize(host, user, options={})
  @session = Net::SSH.start(host, user, options)
  @session_mutex = Mutex.new
  @port_mutex = Mutex.new
  @next_port = MAX_PORT
  @loop_wait = options.delete(:loop_wait) || 0.001
  initiate_event_loop!
end

Public Instance methods

active? ()

Returns true if the gateway is currently open and accepting connections. This will be the case unless shutdown! has been invoked.

[show source] 
# File lib/net/ssh/gateway.rb, line 84
def active?
  @active
end
close (port)

Cancels port-forwarding over an open port that was previously opened via open.

[show source] 
# File lib/net/ssh/gateway.rb, line 146
def close(port)
  ensure_open!

  @session_mutex.synchronize do
    @session.forward.cancel_local(port)
  end
end
open (host, port, local_port=nil)

Opens a new port on the local host and forwards it to the given host/port via the gateway host. If a block is given, the newly allocated port number will be yielded to the block, and the port automatically closed (see close) when the block finishes. Otherwise, the port number will be returned, and the caller is responsible for closing the port (close).

gateway.open('host', 80) do |port|
  # ...
end

port = gateway.open('host', 80)
# ...
gateway.close(port)

If local_port is not specified, the next available port will be used.

[show source] 
# File lib/net/ssh/gateway.rb, line 121
def open(host, port, local_port=nil)
  ensure_open!

  actual_local_port = local_port || next_port

  @session_mutex.synchronize do
    @session.forward.local(actual_local_port, host, port)
  end

  if block_given?
    begin
      yield actual_local_port
    ensure
      close(actual_local_port)
    end
  else
    return actual_local_port
  end
rescue Errno::EADDRINUSE
  raise if local_port # if a local port was explicitly requested, bubble the error up
  retry
end
shutdown! ()

Shuts down the gateway by closing all forwarded ports and then closing the gateway's SSH session.

[show source] 
# File lib/net/ssh/gateway.rb, line 90
def shutdown!
  return unless active?

  @session_mutex.synchronize do
    # cancel all active forward channels
    @session.forward.active_locals.each do |lport, host, port|
      @session.forward.cancel_local(lport)
    end
  end

  @active = false

  @thread.join
  @session.close
end
ssh (host, user, options={}, &block)

Forwards a new connection to the given host and opens a new Net::SSH connection to that host over the forwarded port. If a block is given, the new SSH connection will be yielded to the block, and autoclosed when the block terminates. The forwarded port will be autoclosed as well. If no block was given, the new SSH connection will be returned, and it is up to the caller to terminate both the connection and the forwarded port when done.

gateway.ssh('host', 'user') do |ssh|
  # ...
end

ssh = gateway.ssh('host', 'user')
# ...
ssh.close
gateway.close(ssh.transport.port)
[show source] 
# File lib/net/ssh/gateway.rb, line 170
def ssh(host, user, options={}, &block)
  local_port = open(host, options[:port] || 22)

  begin
    Net::SSH.start("127.0.0.1", user, options.merge(:port => local_port), &block)
  ensure
    close(local_port) if block || $!
  end
end