class Ethon::Easy

def dup

the current handle will be set on duplicated handle.
Clones libcurl session handle. This means that all options that is set in 
def dup
  e = super
  e.handle = Curl.easy_duphandle(handle)
  e.instance_variable_set(:@body_write_callback, nil)
  e.instance_variable_set(:@header_write_callback, nil)
  e.instance_variable_set(:@debug_callback, nil)
  e.instance_variable_set(:@progress_callback, nil)
  e.set_callbacks
  e
end