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require 'open3'
require 'socket'
require 'timeout'

class PortInUse < StandardError; end

class WsProxy
attr_accessor :host, :host_port, :password, :timeout, :idle_timeout, :ssl_target
attr_reader :proxy_port

# Allowed ports to communicate with our web sockets proxy
PORTS = 5910..5930

def initialize(attributes)
# setup all attributes.
defaults.merge(attributes).each do |k, v|
send("#{k}=", v) if respond_to?("#{k}=")
end
end

def self.start(attributes)
proxy = WsProxy.new(attributes)
proxy.start_proxy
end

def free_port?(port)
socket = Socket.new :INET, :STREAM
socket.bind(Socket.pack_sockaddr_in(port, '127.0.0.1'))
true
rescue Errno::EADDRINUSE
false
ensure
socket&.close
end

def start_proxy
# randomly preselect free tcp port from the range
port = 0
Timeout.timeout(5) do
until free_port?(port = rand(PORTS)); end
end
# execute websockify proxy
begin
cmd = "websockify --daemon --idle-timeout=#{idle_timeout} --timeout=#{timeout} #{port} #{host}:#{host_port}"
cmd += " --ssl-target" if ssl_target
if Setting[:websockets_encrypt]
cmd += " --cert #{Setting[:websockets_ssl_cert]}" if Setting[:websockets_ssl_cert]
cmd += " --key #{Setting[:websockets_ssl_key]}" if Setting[:websockets_ssl_key]
end
execute(cmd)
rescue Errno::ENOENT
raise ::Foreman::Exception.new(N_('Websockify was not found'))
rescue PortInUse
# fallback just in case of race condition
port += 1
if port >= PORTS.last
raise ::Foreman::Exception.new(N_('No free ports available for websockify, try again later'))
else
retry
end
end
@proxy_port = port
{ :port => proxy_port, :password => password, :encrypt => Setting[:websockets_encrypt] }
end

private

def defaults
{
:timeout => 120,
:idle_timeout => 120,
:host_port => 5900,
:host => "0.0.0.0",
}
end

def logger
Rails.logger
end

def execute(cmd)
logger.debug "Starting VNC Proxy: #{cmd}"
Open3.popen3(cmd) do |stdin, stdout, stderr|
stdout.each do |line|
logger.debug "[#{line}"
end
stderr.each do |line|
logger.debug "VNCProxy Error: #{line}"
raise PortInUse if line["socket.error: [Errno 98] Address already in use"]
end
end
end
end
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