Class: Net::SSH::Gateway

### Home Classes Methods

### In Files

- lib/net/ssh/gateway.rb

### Parent

Object

### Namespace

- CLASS Net::SSH::Gateway::Version

### Methods

- ::new
- #active?
- #close
- #open
- #shutdown!
- #ssh

### Files

- README.rdoc

### Class/Module Index

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- Net
- Net::SSH
- Net::SSH::Gateway
- Net::SSH::Gateway::Version

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# Net::SSH::Gateway

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.

### Constants

MAX_PORT

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

MIN_PORT

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

### Public Class Methods

new(host, user, options={}) click to toggle source

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.

    # 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?() click to toggle source

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

    # File lib/net/ssh/gateway.rb, line 84
    def active?
      @active
    end

close(port) click to toggle source

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

    # 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) click to toggle source

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.

    # 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!() click to toggle source

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

    # 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) click to toggle source

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)

    # 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

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