Class: Dnsruby::ResolverRuby

Inherits:
Object
  • Object
show all
Defined in:
lib/dnsruby/resolver.rb

Overview

This class implements the I/O using pure Ruby, with no dependencies.

Support for EventMachine has been deprecated.

Instance Method Summary collapse

Constructor Details

#initialize(parent) ⇒ ResolverRuby

:nodoc: all



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# File 'lib/dnsruby/resolver.rb', line 854

def initialize(parent)
  reset_attributes
  @parent=parent
end

Instance Method Details

#close ⇒ Object

Close the Resolver. Unfinished queries are terminated with OtherResolvError.



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# File 'lib/dnsruby/resolver.rb', line 947

def close
  #       @mutex.synchronize {
  @parent.single_res_mutex.synchronize {
    @query_list.each do |client_query_id, values|
     _msg, client_queue, q, _outstanding = values
      send_result_and_stop_querying(client_queue, client_query_id, q, nil,
          OtherResolvError.new('Resolver closing!'))
    end
  }
end

#decrement_resolver_priority(res) ⇒ Object

TO BE CALLED IN A SYNCHRONIZED BLOCK



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# File 'lib/dnsruby/resolver.rb', line 1188

def decrement_resolver_priority(res)
  TheLog.debug("Decrementing resolver priority for #{res.server}\n")
  #       @parent.single_res_mutex.synchronize {
  index = @parent.single_resolvers.index(res)
  if index < @parent.single_resolvers.length
    @parent.single_resolvers.delete(res)
    @parent.single_resolvers.insert(index+1,res)
  end
  #       }
end

#demote_resolver(res) ⇒ Object

TO BE CALLED IN A SYNCHRONIZED BLOCK



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# File 'lib/dnsruby/resolver.rb', line 1200

def demote_resolver(res)
  TheLog.debug("Demoting resolver priority for #{res.server} to bottom\n")
  #       @parent.single_res_mutex.synchronize {
  @parent.single_resolvers.delete(res)
  @parent.single_resolvers.push(res)
  #       }
end

#generate_timeouts ⇒ Object

:nodoc: all



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# File 'lib/dnsruby/resolver.rb', line 937

def generate_timeouts # :nodoc: all
  #  Create the timeouts for the query from the retry_times and retry_delay attributes.
  #  These are created at the same time in case the parameters change during the life of the query.
  #
  #  These should be absolute, rather than relative
  #  The first value should be Time.now[
  @parent.generate_timeouts(Time.now)
end

#handle_error_response(select_queue, query_id, error, response) ⇒ Object

:nodoc: all



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# File 'lib/dnsruby/resolver.rb', line 1116

def handle_error_response(select_queue, query_id, error, response) # :nodoc: all
  #  Handle an error
  #       @mutex.synchronize{
  Dnsruby.log.debug{"handling error #{error.class}, #{error}"}
  #  Check what sort of error it was :
  resolver, _msg, client_query_id, _retry_count = query_id
  _msg, client_queue, select_queue, outstanding = @query_list[client_query_id]
  if error.kind_of?(ResolvTimeout)
    #    - if it was a timeout, then check which number it was, and how many retries are expected on that server
    #        - if it was the last retry, on the last server, then return a timeout to the client (and clean up)
    #        - otherwise, continue
    #  Do we have any more packets to send to this resolver?

    decrement_resolver_priority(resolver)
    timeouts = @timeouts[client_query_id]
    if outstanding.empty? && timeouts && timeouts[1].values.empty?
      Dnsruby.log.debug{'Sending timeout to client'}
      send_result_and_stop_querying(client_queue, client_query_id, select_queue, response, error)
    end
  elsif error.kind_of?(NXDomain)
    #    - if it was an NXDomain, then return that to the client, and stop all new queries (and clean up)
    #         send_result_and_stop_querying(client_queue, client_query_id, select_queue, response, error)
    increment_resolver_priority(resolver) unless response.cached
    stop_querying(client_query_id)
    #  @TODO@ Does the client want notified at this point?
  elsif error.kind_of?(EncodeError)
    Dnsruby.log.debug{'Encode error - sending to client'}
    send_result_and_stop_querying(client_queue, client_query_id, select_queue, response, error)
  else
    #    - if it was any other error, then remove that server from the list for that query
    #    If a Too Many Open Files error, then don't remove, but let retry work.
    timeouts = @timeouts[client_query_id]
    unless error.to_s =~ /Errno::EMFILE/
      Dnsruby.log.debug{"Removing #{resolver.server} from resolver list for this query"}
      if timeouts
        timeouts[1].each do |key, value|
          res = value[0]
          if res == resolver
            timeouts[1].delete(key)
          end
        end
      end
      #  Also stick it to the back of the list for future queries
      demote_resolver(resolver)
    else
      Dnsruby.log.debug("NOT Removing #{resolver.server} due to Errno::EMFILE")
    end
    #         - if it was the last server, then return an error to the client (and clean up)
    if outstanding.empty? && ((!timeouts) || (timeouts && timeouts[1].values.empty?))
      #           if outstanding.empty?
      Dnsruby.log.debug{'Sending error to client'}
      send_result_and_stop_querying(client_queue, client_query_id, select_queue, response, error)
    end
  end
  #  @TODO@ If we're still sending packets for this query, but none are outstanding, then
  #  jumpstart the next query?
  #       }
end

#handle_queue_event(queue, id) ⇒ Object

This method is called by the SelectThread (in the select thread) when the queue has a new item on it.

The queue interface is used to separate producer/consumer threads, but we're using it here in one thread.
It's probably a good idea to create a new "worker thread" to take items from the select thread queue and
call this method in the worker thread.



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# File 'lib/dnsruby/resolver.rb', line 1039

def handle_queue_event(queue, id) # :nodoc: all
  #  Time to process a new queue event.
  #  If we get a callback for an ID we don't know about, don't worry -
  #  just ignore it. It may be for a query we've already completed.
  #
  #  So, get the next response from the queue (presuming there is one!)
  #
  #  @TODO@ Tick could poll the queue and then call this method if needed - no need for observer interface.
  #  @TODO@ Currently, tick and handle_queue_event called from select_thread - could have thread chuck events in to tick_queue. But then, clients would have to call in on other thread!
  #
  #  So - two types of response :
  #  1) we've got a coherent response (or error) - stop sending more packets for that query!
  #  2) we've validated the response - it's ready to be sent to the client
  #
  #  so need two more methods :
  #   handleValidationResponse : basically calls send_result_and_stop_querying and
  #   handleValidationError : does the same as handleValidationResponse, but for errors
  #  can leave handleError alone
  #  but need to change handleResponse to stop sending, rather than send_result_and_stop_querying.
  #
  #  @TODO@ Also, we could really do with a MaxValidationTimeout - if validation not OK within
  #  this time, then raise Timeout (and stop validation)?
  #
  #  @TODO@ Also, should there be some facility to stop validator following same chain
  #  concurrently?
  #
  #  @TODO@ Also, should have option to speak only to configured resolvers (not follow authoritative chain)
  #
  if queue.empty?
    Dnsruby.log_and_raise('Severe internal error - Queue empty in handle_queue_event')
  end
  event_id, event_type, response, error = queue.pop
  #  We should remove this packet from the list of outstanding packets for this query
  _resolver, _msg, client_query_id, _retry_count = id
  if id != event_id
    Dnsruby.log_and_raise("Serious internal error!! #{id} expected, #{event_id} received")
  end
  #       @mutex.synchronize{
  @parent.single_res_mutex.synchronize {
    if @query_list[client_query_id] == nil
      #           print "Dead query response - ignoring\n"
      Dnsruby.log.debug{'Ignoring response for dead query'}
      return
    end
    _msg, _client_queue, _select_queue, outstanding = @query_list[client_query_id]
    if event_type == Resolver::EventType::RECEIVED ||
          event_type == Resolver::EventType::ERROR
      unless outstanding.include?(id)
        Dnsruby.log.error("Query id not on outstanding list! #{outstanding.length} items. #{id} not on #{outstanding}")
      end
      outstanding.delete(id)
    end
    #       }
    if event_type == Resolver::EventType::RECEIVED
      #       if (event.kind_of?(Exception))
      if error
        handle_error_response(queue, event_id, error, response)
      else # if event.kind_of?(Message)
        handle_response(queue, event_id, response)
        #       else
        #         Dnsruby.log.error('Random object #{event.class} returned through queue to Resolver')
      end
    elsif event_type == Resolver::EventType::VALIDATED
      if error
        handle_validation_error(queue, event_id, error, response)
      else
        handle_validation_response(queue, event_id, response)
      end
    elsif event_type == Resolver::EventType::ERROR
      handle_error_response(queue, event_id, error, response)
    else
      #           print "ERROR - UNKNOWN EVENT TYPE IN RESOLVER : #{event_type}\n"
      TheLog.error("ERROR - UNKNOWN EVENT TYPE IN RESOLVER : #{event_type}")
    end
  }
end

#handle_response(select_queue, query_id, response) ⇒ Object

:nodoc: all



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# File 'lib/dnsruby/resolver.rb', line 1208

def handle_response(select_queue, query_id, response) # :nodoc: all
  #  Handle a good response
  #  Should also stick resolver more to the front of the list for future queries
  Dnsruby.log.debug('Handling good response')
  resolver, _msg, client_query_id, _retry_count = query_id
  increment_resolver_priority(resolver) unless response.cached
  #       @mutex.synchronize{
  _query, _client_queue, s_queue, _outstanding = @query_list[client_query_id]
  if s_queue != select_queue
    Dnsruby.log_and_raise("Serious internal error : expected select queue #{s_queue}, got #{select_queue}")
  end
  stop_querying(client_query_id)
  #  @TODO@ Does the client want notified at this point?
  #         client_queue.push([client_query_id, Resolver::EventType::RECEIVED, msg, nil])
  #       }
end

#handle_validation_error(select_queue, query_id, error, response) ⇒ Object 



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# File 'lib/dnsruby/resolver.rb', line 1242

def handle_validation_error(select_queue, query_id, error, response)
  _resolver, _msg, client_query_id, _retry_count = query_id
  _query, client_queue, s_queue, _outstanding = @query_list[client_query_id]
  if s_queue != select_queue
    Dnsruby.log_and_raise("Serious internal error : expected select queue #{s_queue}, got #{select_queue}")
  end
  #       For some errors, we immediately send result. For others, should we retry?
  #       Either :
  #                 handle_error_response(queue, event_id, error, response)
  #                 Or:
  send_result(client_queue, client_query_id, select_queue, response, error)
  #
  #
end

#handle_validation_response(select_queue, query_id, response) ⇒ Object

:nodoc: all



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# File 'lib/dnsruby/resolver.rb', line 1225

def handle_validation_response(select_queue, query_id, response) # :nodoc: all
  _resolver, _msg, client_query_id, _retry_count = query_id
  #       @mutex.synchronize {
  _query, client_queue, s_queue, _outstanding = @query_list[client_query_id]
  if s_queue != select_queue
    Dnsruby.log_and_raise("Serious internal error : expected select queue #{s_queue}, got #{select_queue}")
  end
  if response.rcode == RCode.NXDOMAIN
    send_result(client_queue, client_query_id, select_queue, response, NXDomain.new)
  else
    #  @TODO@ Was there an error validating? Should we raise an exception for certain security levels?
    #  This should be configurable by the client.
    send_result(client_queue, client_query_id, select_queue, response, nil)
    #       }
  end
end

#increment_resolver_priority(res) ⇒ Object

TO BE CALLED IN A SYNCHRONIZED BLOCK



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# File 'lib/dnsruby/resolver.rb', line 1176

def increment_resolver_priority(res)
  TheLog.debug("Incrementing resolver priority for #{res.server}\n")
  #       @parent.single_res_mutex.synchronize {
  index = @parent.single_resolvers.index(res)
  if index > 0
    @parent.single_resolvers.delete(res)
    @parent.single_resolvers.insert(index-1,res)
  end
  #       }
end

#reset_attributes ⇒ Object

:nodoc: all



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# File 'lib/dnsruby/resolver.rb', line 858

def reset_attributes # :nodoc: all
  #  data structures
  #       @mutex=Mutex.new
  @query_list = {}
  @timeouts = {}
end

#send_async(msg, client_queue, client_query_id = nil) ⇒ Object 



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# File 'lib/dnsruby/resolver.rb', line 864

def send_async(msg, client_queue, client_query_id=nil)
  #  This is the whole point of the Resolver class.
  #  We want to use multiple SingleResolvers to run a query.
  #  So we kick off a system with select_thread where we send
  #  a query with a queue, but log ourselves as observers for that
  #  queue. When a new response is pushed on to the queue, then the
  #  select thread will call this class' handler method IN THAT THREAD.
  #  When the final response is known, this class then sticks it in
  #  to the client queue.

  q = Queue.new
  if client_query_id.nil?
    client_query_id = Time.now + rand(10000)
  end

  unless client_queue.kind_of?(Queue)
    Dnsruby.log_and_raise('Wrong type for client_queue in Resolver# send_async')
    #  @TODO@ Handle different queue tuples - push this to generic send_error method
    client_queue.push([client_query_id, ArgumentError.new('Wrong type of client_queue passed to Dnsruby::Resolver# send_async - should have been Queue, was #{client_queue.class}')])
    return
  end

  unless msg.kind_of?Message
    Dnsruby.log.error{'Wrong type for msg in Resolver# send_async'}
    #  @TODO@ Handle different queue tuples - push this to generic send_error method
    client_queue.push([client_query_id, ArgumentError.new("Wrong type of msg passed to Dnsruby::Resolver# send_async - should have been Message, was #{msg.class}")])
    return
  end

  # According to RFC 6891, a UDP payload size >512 bytes requires an
  # EDNS OPT RR in the message.
  if @parent.udp_size > 512 && !msg.get_opt
    TheLog.debug("Automatically adding EDNS OPT RR for udp_size=#{ @parent.udp_size }")
    msg.add_additional(Dnsruby::RR::OPT.new(@parent.udp_size))
  end

  begin
    msg.encode
  rescue EncodeError => err
    Dnsruby.log.error { "Can't encode " + msg.to_s + " : #{err}" }
    client_queue.push([client_query_id, err])
    return
  end

  tick_needed = false
  #  add to our data structures
  #       @mutex.synchronize{
  @parent.single_res_mutex.synchronize {
    tick_needed = true if @query_list.empty?
    if @query_list.has_key?(client_query_id)
      Dnsruby.log.error("Duplicate query id requested (#{client_query_id}")
      #  @TODO@ Handle different queue tuples - push this to generic send_error method
      client_queue.push([client_query_id, ArgumentError.new('Client query ID already in use')])
      return
    end
    outstanding = []
    @query_list[client_query_id]=[msg, client_queue, q, outstanding]

    query_timeout = Time.now + @parent.query_timeout
    if @parent.query_timeout == 0
      query_timeout = Time.now + 31536000 # a year from now
    end
    @timeouts[client_query_id] = [query_timeout, generate_timeouts]
  }

  #  Now do querying stuff using SingleResolver
  #  All this will be handled by the tick method (if we have 0 as the first timeout)
  st = SelectThread.instance
  st.add_observer(q, self)
  tick if tick_needed
  client_query_id
end

#send_result(client_queue, client_query_id, select_queue, msg, error) ⇒ Object

MUST BE CALLED IN A SYNCHRONIZED BLOCK!

Sends the result to the client's queue, and removes the queue observer from the select thread



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# File 'lib/dnsruby/resolver.rb', line 977

def send_result(client_queue, client_query_id, select_queue, msg, error) # :nodoc: all
  stop_querying(client_query_id)  # @TODO@ !
  #  We might still get some callbacks, which we should ignore
  st = SelectThread.instance
  st.remove_observer(select_queue, self)
  #       @mutex.synchronize{
  #  Remove the query from all of the data structures
  @query_list.delete(client_query_id)
  #       }
  #  Return the response to the client
  client_queue.push([client_query_id, msg, error])
end

#send_result_and_stop_querying(client_queue, client_query_id, select_queue, msg, error) ⇒ Object

MUST BE CALLED IN A SYNCHRONIZED BLOCK!

Send the result back to the client, and close the socket for that query by removing
the query from the select thread.



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# File 'lib/dnsruby/resolver.rb', line 962

def send_result_and_stop_querying(client_queue, client_query_id, select_queue, msg, error) # :nodoc: all
  stop_querying(client_query_id)
  send_result(client_queue, client_query_id, select_queue, msg, error)
end

#stop_querying(client_query_id) ⇒ Object

MUST BE CALLED IN A SYNCHRONIZED BLOCK!

Stops send any more packets for a client-level query



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# File 'lib/dnsruby/resolver.rb', line 970

def stop_querying(client_query_id) # :nodoc: all
  @timeouts.delete(client_query_id)
end

#tick ⇒ Object

This method is called twice a second from the select loop, in the select thread.

It should arguably be called from another worker thread... (which also handles the queue)
Each tick, we check if any timeouts have occurred. If so, we take the appropriate action :
Return a timeout to the client, or send a new query



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# File 'lib/dnsruby/resolver.rb', line 994

def tick # :nodoc: all
  #  Handle the tick
  #  Do we have any retries due to be sent yet?
  #       @mutex.synchronize{
  @parent.single_res_mutex.synchronize {
    time_now = Time.now
    @timeouts.keys.each do |client_query_id|
      msg, client_queue, select_queue, outstanding = @query_list[client_query_id]
      query_timeout, timeouts = @timeouts[client_query_id]
      if query_timeout < Time.now
        #  Time the query out
        send_result_and_stop_querying(client_queue, client_query_id, select_queue, nil,
            ResolvTimeout.new('Query timed out'))
        next
      end
      timeouts_done = []
      timeouts.keys.sort.each do |timeout|
        if timeout < time_now
          #  Send the next query
          res, retry_count = timeouts[timeout]
          id = [res, msg, client_query_id, retry_count]
          Dnsruby.log.debug("Sending msg to #{res.server}")
          #  We should keep a list of the queries which are outstanding
          outstanding.push(id)
          timeouts_done.push(timeout)
          timeouts.delete(timeout)

          #  Pick a new QID here @TODO@ !!!
          #               msg.header.id = rand(65535);
          #               print "New query : #{new_msg}\n"
          res.send_async(msg, select_queue, id)
        else
          break
        end
      end
      timeouts_done.each { |t| timeouts.delete(t) }
    end
  }
end