Class: Dnsruby::SelectThread

Inherits:
Object
  • Object
show all
Includes:
Singleton
Defined in:
lib/dnsruby/select_thread.rb

Overview

:nodoc: all

Defined Under Namespace

Classes: QuerySettings, SelectWakeup

Instance Method Summary collapse

Constructor Details

#initialize ⇒ SelectThread

This singleton class runs a continuous select loop which

listens for responses on all of the in-use sockets.
When a new query is sent, the thread is woken up, and
the socket is added to the select loop (and the new timeout
calculated).
Note that a combination of the socket and the packet ID is
sufficient to uniquely identify the query to the select thread.

But how do we find the response queue for a particular query?
Hash of client_id->[query, client_queue, socket]
and socket->[client_id]

@todo@ should we implement some of cancel function?



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# File 'lib/dnsruby/select_thread.rb', line 44

def initialize
  @@mutex = Mutex.new
  @@mutex.synchronize {
    @@in_select=false
    #         @@notifier,@@notified=IO.pipe
    @@sockets = [] # @@notified]
    @@timeouts = Hash.new
    #     @@mutex.synchronize do
    @@query_hash = Hash.new
    @@socket_hash = Hash.new
    @@observers = Hash.new
    @@tcp_buffers=Hash.new
    @@tick_observers = []
    @@queued_exceptions=[]
    @@queued_responses=[]
    @@queued_validation_responses=[]
    @@wakeup_sockets = get_socket_pair
    @@sockets << @@wakeup_sockets[1]

    #  Suppress reverse lookups
    BasicSocket.do_not_reverse_lookup = true
    #     end
    #  Now start the select thread
    @@select_thread = Thread.new {
      do_select
    }
    #         # Start the validator thread
    #         @@validator = ValidatorThread.instance
  }
end

Instance Method Details

#add_observer(client_queue, observer) ⇒ Object 



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# File 'lib/dnsruby/select_thread.rb', line 671

def add_observer(client_queue, observer)
  @@mutex.synchronize {
    @@observers[client_queue]=observer
    check_select_thread_synchronized # Is this really necessary? The client should start the thread by sending a query, really...
    if (!@@tick_observers.include?observer)
      @@tick_observers.push(observer)
    end
  }
end

#add_to_select(query_settings) ⇒ Object 



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# File 'lib/dnsruby/select_thread.rb', line 114

def add_to_select(query_settings)
  #  Add the query to sockets, and then wake the select thread up
  @@mutex.synchronize {
    check_select_thread_synchronized
    #  @TODO@ This assumes that all client_query_ids are unique!
    #  Would be a good idea at least to check this...
    @@query_hash[query_settings.client_query_id]=query_settings
    @@socket_hash[query_settings.socket]=[query_settings.client_query_id] # @todo@ If we use persistent sockets then we need to update this array
    @@timeouts[query_settings.client_query_id]=query_settings.endtime
    @@sockets.push(query_settings.socket)
  }
  begin
    @@wakeup_sockets[0].send("wakeup!", 0)
  rescue Exception => e
    #          do nothing
  end
end

#check_select_thread_synchronized ⇒ Object 



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# File 'lib/dnsruby/select_thread.rb', line 132

def check_select_thread_synchronized
  if (!@@select_thread.alive?)
    Dnsruby.log.debug{"Restarting select thread"}
    @@select_thread = Thread.new {
      do_select
    }
  end
end

#do_select ⇒ Object 



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# File 'lib/dnsruby/select_thread.rb', line 149

def do_select
  unused_loop_count = 0
  last_tick_time = Time.now - 10
  while true do
    if (last_tick_time < (Time.now - 0.5))
      send_tick_to_observers # ONLY NEED TO SEND THIS TWICE A SECOND - NOT EVERY SELECT!!!
      last_tick_time = Time.now
    end
    send_queued_exceptions
    send_queued_responses
    send_queued_validation_responses
    timeout = tick_time = 0.1 # We provide a timer service to various Dnsruby classes
    sockets=[]
    timeouts=[]
    has_observer = false
    @@mutex.synchronize {
      sockets = @@sockets
      timeouts = @@timeouts.values
      has_observer = !@@observers.empty?
    }
    if (timeouts.length > 0)
      timeouts.sort!
      timeout = timeouts[0] - Time.now
      if (timeout <= 0)
        process_timeouts
        timeout = 0
        next
      end
    end
    ready=nil
    if (has_observer && (timeout > tick_time))
      timeout = tick_time
    end
    #         next if (timeout < 0)
    begin
      ready, write, errors = IO.select(sockets, nil, nil, timeout)
    rescue SelectWakeup
      #  If SelectWakeup, then just restart this loop - the select call will be made with the new data
      next
    rescue IOError => e# Don't worry if the socket was closed already
      #           print "IO Error  =: #{e}\n"
      next
    end
    if ready && ready.include?(@@wakeup_sockets[1])
      ready.delete(@@wakeup_sockets[1])
      wakeup_msg = "loop"
      begin
        while wakeup_msg && wakeup_msg.length > 0
          wakeup_msg = @@wakeup_sockets[1].recv_nonblock(20)
        end
      rescue
        #  do nothing
      end
    end
    if (ready == nil)
      #  proces the timeouts
      process_timeouts
      unused_loop_count+=1
    else
      process_ready(ready)
      unused_loop_count=0
      #                   process_error(errors)
    end
    @@mutex.synchronize{
      if (unused_loop_count > 10 && @@query_hash.empty? && @@observers.empty?)
        Dnsruby.log.debug{"Stopping select loop"}
        return
      end
    }
    #               }
  end
end

#get_client_id_from_answerfrom(socket, answerip, answerport) ⇒ Object 



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# File 'lib/dnsruby/select_thread.rb', line 513

def get_client_id_from_answerfrom(socket, answerip, answerport)
  #  @TODO@ Can get rid of this, as there is only one query per socket
  client_id=nil
  #  Figure out client id from answerfrom
  @@mutex.synchronize{
    ids = @@socket_hash[socket]
    ids.each do |id|
      #  Does this id speak to this dest_server?
      query_settings = @@query_hash[id]
      if (answerip == query_settings.dest_server && answerport == query_settings.dest_port)
        #  We have a match
        client_id = id
        break
      end
    end
  }
  return client_id
end

#get_incoming_data(socket, packet_size) ⇒ Object 



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# File 'lib/dnsruby/select_thread.rb', line 391

def get_incoming_data(socket, packet_size)
  answerfrom,answerip,answerport,answersize=nil
  ans,buf = nil
  begin
    if (socket.class == TCPSocket)
      #  @todo@ Ruby Bug #9061 stops this working right
      #  We'd like to do a socket.recvfrom, but that raises an Exception
      #  on Windows for TCPSocket for Ruby 1.8.5 (and 1.8.6).
      #  So, we need to do something different for TCP than UDP. *sigh*
      #  @TODO@ This workaround will only work if there is exactly one socket per query
      #     - *not* ideal TCP use!
      @@mutex.synchronize{
        client_id = @@socket_hash[socket][0]
        answerfrom = @@query_hash[client_id].dest_server
        answerip = answerfrom
        answerport = @@query_hash[client_id].dest_port
      }

      #  Call TCP read here - that will take care of reading the 2 byte length,
      #  and then the full packet - without blocking select.
      buf = tcp_read(socket)
      if (!buf) # Wait for the buffer to comletely fill
        #             handle_recvfrom_failure(socket, "")
        return
      end
    else
      #  @TODO@ Can we get recvfrom to stop issuing PTR queries when we already
      #  know both the FQDN and the IP address?
      if (ret = socket.recvfrom(packet_size))
        buf = ret[0]
        answerport=ret[1][1]
        answerfrom=ret[1][2]
        answerip=ret[1][3]
        answersize=(buf.length)
      else
        #  recvfrom failed - why?
        Dnsruby.log.error{"Error - recvfrom failed from #{socket}"}
        handle_recvfrom_failure(socket, "")
        return
      end
    end
  rescue Exception => e
    Dnsruby.log.error{"Error - recvfrom failed from #{socket}, exception : #{e}"}
    handle_recvfrom_failure(socket, e)
    return
  end
  Dnsruby.log.debug{";; answer from #{answerfrom} : #{answersize} bytes\n"}

  begin
    ans = Message.decode(buf)
  rescue Exception => e
    Dnsruby.log.error{"Decode error! #{e.class}, #{e}\nfor msg (length=#{buf.length}) : #{buf}"}
    client_id=get_client_id_from_answerfrom(socket, answerip, answerport)
    if (client_id == nil)
      Dnsruby.log.error{"Decode error from #{answerip} but can't determine packet id"}
    end
    #  We should check if the TC bit is set (if we can get that far)
    if ((DecodeError === e) && (e.partial_message.header.tc))
      Dnsruby.log.error{"Decode error (from {answerip})! Header shows truncation, so trying again over TCP"}
      #  If it is, then we should retry over TCP
      sent = false
      @@mutex.synchronize{
        client_ids = @@socket_hash[socket]
        #  get the queries associated with them
        client_ids.each do |id|
          query_header_id=nil
          query_header_id = @@query_hash[id].query.header.id
          if (query_header_id == e.partial_message.header.id)
            #  process the response
            client_queue = nil
            res = nil
            query=nil
            client_queue = @@query_hash[id].client_queue
            res = @@query_hash[id].single_resolver
            query = @@query_hash[id].query

            #  NOW RESEND OVER TCP!
            Thread.new {
              res.send_async(query, client_queue, id, true)
            }
            sent = true
          end
        end
      }
      if !sent
        send_exception_to_client(e, socket, client_id)
      end

    else
      send_exception_to_client(e, socket, client_id)
    end
    return
  end

  if (ans!= nil)
    Dnsruby.log.debug{"#{ans}"}
    ans.answerfrom=(answerfrom)
    ans.answersize=(answersize)
    ans.answerip =(answerip)
  end
  return ans, buf
end

#get_socket_pair ⇒ Object 



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# File 'lib/dnsruby/select_thread.rb', line 75

def get_socket_pair
  #  Emulate socketpair on platforms which don't support it
  srv = nil
  begin
    srv = TCPServer.new('localhost', 0)
  rescue Errno::EADDRNOTAVAIL, SocketError # OSX Snow Leopard issue - need to use explicit IP
    begin
      srv = TCPServer.new('127.0.0.1', 0)
    rescue Error # Try IPv6
      srv = TCPServer.new('::1', 0)
    end
  end
  rsock = TCPSocket.new(srv.addr[3], srv.addr[1])
  lsock = srv.accept
  srv.close
  return [lsock, rsock]
end

#handle_recvfrom_failure(socket, exception) ⇒ Object 



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# File 'lib/dnsruby/select_thread.rb', line 494

def handle_recvfrom_failure(socket, exception)
  #   No way to notify the client about this error, unless there was only one connection on the socket
  #  Not a problem, as there only will ever be one connection on the socket (Kaminsky attack mitigation)
  ids_for_socket = []
  @@mutex.synchronize{
    ids_for_socket = @@socket_hash[socket]
  }
  if (ids_for_socket.length == 1)
    answerfrom=nil
    @@mutex.synchronize{
      query_settings = @@query_hash[ids_for_socket[0]]
      answerfrom=query_settings.dest_server
    }
    send_exception_to_client(OtherResolvError.new("recvfrom failed from #{answerfrom}; #{exception}"), socket, ids_for_socket[0])
  else
    Dnsruby.log.fatal{"Recvfrom failed from #{socket}, no way to tell query id"}
  end
end

#notify_queue_observers(client_queue, client_query_id) ⇒ Object 



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# File 'lib/dnsruby/select_thread.rb', line 698

def notify_queue_observers(client_queue, client_query_id)
  #  If any observers are known for this query queue then notify them
  observer=nil
  @@mutex.synchronize {
    observer = @@observers[client_queue]
  }
  if (observer)
    observer.handle_queue_event(client_queue, client_query_id)
  end
end

#process_error(errors) ⇒ Object 



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# File 'lib/dnsruby/select_thread.rb', line 222

def process_error(errors)
  Dnsruby.log.debug{"Error! #{errors.inspect}"}
  #  @todo@ Process errors [can we do this in single socket environment?]
end

#process_ready(ready) ⇒ Object

@@query_hash=query_settings

@@socket_hash[query_settings.socket]=[query_settings.client_query_id] # @todo@ If we use persistent sockets then we need to update this array



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# File 'lib/dnsruby/select_thread.rb', line 229

def process_ready(ready)
  ready.each do |socket|
    query_settings = nil
    @@mutex.synchronize{
      #  Can do this if we have a query per socket, but not otherwise...
      c_q_id = @@socket_hash[socket][0] # @todo@ If we use persistent sockets then this won't work
      query_settings = @@query_hash[c_q_id]
    }
    next if !query_settings
    udp_packet_size = query_settings.udp_packet_size
    msg, bytes = get_incoming_data(socket, udp_packet_size)
    if (msg!=nil)
      #  Check that the IP we received from was the IP we sent to!
      answerip = msg.answerip.downcase
      answerfrom = msg.answerfrom.downcase
      dest_server = query_settings.dest_server
      answeripaddr = IPAddr.new(answerip)
      dest_server = IPAddr.new("0.0.0.0")
      begin
        destserveripaddr = IPAddr.new(dest_server)
      rescue ArgumentError
        #  Host name not IP address
      end
      if (dest_server && (dest_server != '0.0.0.0') &&
            (answeripaddr != destserveripaddr) &&
            (answerfrom != dest_server))
        Dnsruby.log.warn("Unsolicited response received from #{answerip} instead of #{query_settings.dest_server}")
      else
        send_response_to_client(msg, bytes, socket)
      end
    end
    ready.delete(socket)
  end
end

#process_timeouts ⇒ Object 



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# File 'lib/dnsruby/select_thread.rb', line 326

def process_timeouts
  time_now = Time.now
  timeouts={}
  @@mutex.synchronize {
    timeouts = @@timeouts
  }
  timeouts.each do |client_id, timeout|
    if (timeout < time_now)
      send_exception_to_client(ResolvTimeout.new("Query timed out"), nil, client_id)
    end
  end
end

#push_exception_to_select(client_id, client_queue, err, msg) ⇒ Object 



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# File 'lib/dnsruby/select_thread.rb', line 544

def push_exception_to_select(client_id, client_queue, err, msg)
  @@mutex.synchronize{
    @@queued_exceptions.push([client_id, client_queue, err, msg])
  }
  #  Make sure select loop is running!
  if (@@select_thread && @@select_thread.alive?)
  else
    @@select_thread = Thread.new {
      do_select
    }
  end
end

#push_response_to_select(client_id, client_queue, msg, query, res) ⇒ Object 



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# File 'lib/dnsruby/select_thread.rb', line 557

def push_response_to_select(client_id, client_queue, msg, query, res)
  #  This needs to queue the response TO THE SELECT THREAD, which then needs
  #  to send it out from its normal loop.
  Dnsruby.log.debug{"Pushing response to client queue direct from resolver or validator"}
  @@mutex.synchronize{
    err = nil
    if (msg.rcode == RCode.NXDOMAIN)
      err = NXDomain.new
    end
    @@queued_responses.push([client_id, client_queue, msg, err, query, res])
  }
  #  Make sure select loop is running!
  if (@@select_thread && @@select_thread.alive?)
  else
    @@select_thread = Thread.new {
      do_select
    }
  end
end

#push_to_client(client_id, client_queue, msg, err, query, res) ⇒ Object 



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# File 'lib/dnsruby/select_thread.rb', line 652

def push_to_client(client_id, client_queue, msg, err, query, res)
  #  @TODO@ Really need to let the client know that we have received a valid response!
  #  Can do that by calling notify_observers here, but with an identifier which
  #  defines the response to be a "Response received - validating. Please stop sending"
  #  type of response.
  client_queue.push([client_id, Resolver::EventType::RECEIVED, msg, err])
  notify_queue_observers(client_queue, client_id)

  if (!err || (err.instance_of?(NXDomain)))
    # 
    #  This method now needs to push the response to the validator,
    #  which will then take responsibility for delivering it to the client.
    #  The validator will need access to the queue observers -
    validator = ValidatorThread.new(client_id, client_queue, msg, err, query ,self, res)
    validator.run
    #       @@validator.add_to_queue([client_id, client_queue, msg, err, query, self, res])
  end
end

#push_validation_response_to_select(client_id, client_queue, msg, err, query, res) ⇒ Object 



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# File 'lib/dnsruby/select_thread.rb', line 577

def push_validation_response_to_select(client_id, client_queue, msg, err, query, res)
  #  This needs to queue the response TO THE SELECT THREAD, which then needs
  #  to send it out from its normal loop.
  Dnsruby.log.debug{"Pushing response to client queue direct from resolver or validator"}
  @@mutex.synchronize{
    @@queued_validation_responses.push([client_id, client_queue, msg, err, query, res])
  }
  #  Make sure select loop is running!
  if (@@select_thread && @@select_thread.alive?)
  else
    @@select_thread = Thread.new {
      do_select
    }
  end
end

#remove_id(id) ⇒ Object 



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# File 'lib/dnsruby/select_thread.rb', line 310

def remove_id(id)
  socket=nil
  @@mutex.synchronize{
    socket = @@query_hash[id].socket
    @@timeouts.delete(id)
    @@query_hash.delete(id)
    @@socket_hash.delete(socket)
    @@sockets.delete(socket) # @TODO@ Not if persistent!
  }
  Dnsruby.log.debug{"Closing socket #{socket}"}
  begin
    socket.close # @TODO@ Not if persistent!
  rescue IOError # Don't worry if the socket was closed already
  end
end

#remove_observer(client_queue, observer) ⇒ Object 



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# File 'lib/dnsruby/select_thread.rb', line 681

def remove_observer(client_queue, observer)
  @@mutex.synchronize {
    if (@@observers[client_queue]==observer)
      #           @@observers.delete(observer)
      @@observers.delete(client_queue)
    else
      if (@@observers[client_queue] == nil)
      end
      Dnsruby.log.error{"remove_observer called with wrong observer for queue"}
      raise ArgumentError.new("remove_observer called with wrong observer for queue")
    end
    if (!@@observers.values.include?observer)
      @@tick_observers.delete(observer)
    end
  }
end

#select_thread_alive? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/dnsruby/select_thread.rb', line 141

def select_thread_alive?
  ret=true
  @@mutex.synchronize{
    ret = @@select_thread.alive?
  }
  return ret
end

#send_exception_to_client(err, socket, client_id, msg = nil) ⇒ Object 



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# File 'lib/dnsruby/select_thread.rb', line 532

def send_exception_to_client(err, socket, client_id, msg=nil)
  #  find the client response queue
  client_queue = nil
  @@mutex.synchronize {
    client_queue = @@query_hash[client_id].client_queue
  }
  remove_id(client_id)
  #       push_to_client(client_id, client_queue, msg, err)
  client_queue.push([client_id, Resolver::EventType::ERROR, msg, err])
  notify_queue_observers(client_queue, client_id)
end

#send_queued_exceptions ⇒ Object 



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# File 'lib/dnsruby/select_thread.rb', line 593

def send_queued_exceptions
  exceptions = []
  @@mutex.synchronize{
    exceptions = @@queued_exceptions
    @@queued_exceptions = []
  }

  exceptions.each do |item|
    client_id, client_queue, err, msg = item
    #         push_to_client(client_id, client_queue, msg, err)
    client_queue.push([client_id, Resolver::EventType::ERROR, msg, err])
    notify_queue_observers(client_queue, client_id)
  end
end

#send_queued_responses ⇒ Object 



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# File 'lib/dnsruby/select_thread.rb', line 608

def send_queued_responses
  responses = []
  @@mutex.synchronize{
    responses = @@queued_responses
    @@queued_responses = []
  }

  responses.each do |item|
    client_id, client_queue, msg, err, query, res = item
    #         push_to_client(client_id, client_queue, msg, err)
    client_queue.push([client_id, Resolver::EventType::RECEIVED, msg, err])
    notify_queue_observers(client_queue, client_id)
    #  Do we need to validate this? The response has come from the cache -
    #  validate it only if it has not been validated already
    #  So, if we need to validate it, send it to the validation thread
    #  Otherwise, send VALIDATED to the requester.
    if (((msg.security_level == Message::SecurityLevel::UNCHECKED) ||
            (msg.security_level == Message::SecurityLevel::INDETERMINATE)) &&
          (ValidatorThread.requires_validation?(query, msg, err, res)))
      validator = ValidatorThread.new(client_id, client_queue, msg, err, query ,self, res)
      validator.run
    else
      PacketSender.cache(query, msg) # The validator won't cache it, so we'd better do it now
      client_queue.push([client_id, Resolver::EventType::VALIDATED, msg, err])
      notify_queue_observers(client_queue, client_id)
    end
  end
end

#send_queued_validation_responses ⇒ Object 



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# File 'lib/dnsruby/select_thread.rb', line 637

def send_queued_validation_responses
  responses = []
  @@mutex.synchronize{
    responses = @@queued_validation_responses
    @@queued_validation_responses = []
  }

  responses.each do |item|
    client_id, client_queue, msg, err, query, res = item
    #         push_to_client(client_id, client_queue, msg, err)
    client_queue.push([client_id, Resolver::EventType::VALIDATED, msg, err])
    notify_queue_observers(client_queue, client_id)
  end
end

#send_response_to_client(msg, bytes, socket) ⇒ Object 



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# File 'lib/dnsruby/select_thread.rb', line 264

def send_response_to_client(msg, bytes, socket)
  #  Figure out which client_ids we were expecting on this socket, then see if any header ids match up
  #  @TODO@ Can get rid of this, as we only have one query per socket.
  client_ids=[]
  @@mutex.synchronize{
    client_ids = @@socket_hash[socket]
  }
  #  get the queries associated with them
  client_ids.each do |id|
    query_header_id=nil
    @@mutex.synchronize{
      query_header_id = @@query_hash[id].query.header.id
    }
    if (query_header_id == msg.header.id)
      #  process the response
      client_queue = nil
      res = nil
      query=nil
      @@mutex.synchronize{
        client_queue = @@query_hash[id].client_queue
        res = @@query_hash[id].single_resolver
        query = @@query_hash[id].query
      }
      tcp = (socket.class == TCPSocket)
      #  At this point, we should check if the response is OK
      if (ret = res.check_response(msg, bytes, query, client_queue, id, tcp))
        remove_id(id)
        exception = msg.get_exception
        if (ret.kind_of?TsigError)
          exception = ret
        end
        Dnsruby.log.debug{"Pushing response to client queue"}
        push_to_client(id, client_queue, msg, exception, query, res)
        #             client_queue.push([id, msg, exception])
        #             notify_queue_observers(client_queue, id)
      else
        #  Sending query again - don't return response
      end
      return
    end
  end
  #  If not, then we have an error
  Dnsruby.log.error{"Stray packet - " + msg.inspect + "\n from " + socket.inspect}
  print("Stray packet - " + msg.question()[0].qname.to_s + " from " + msg.answerip.to_s + ", #{client_ids.length} client_ids\n")
end

#send_tick_to_observers ⇒ Object 



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# File 'lib/dnsruby/select_thread.rb', line 709

def send_tick_to_observers
  #  If any observers are known then send them a tick
  tick_observers=nil
  @@mutex.synchronize {
    tick_observers = @@tick_observers
  }
  tick_observers.each do |observer|
    observer.tick
  end
end

#tcp_read(socket) ⇒ Object 



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# File 'lib/dnsruby/select_thread.rb', line 339

def tcp_read(socket)
  #  Keep buffer for all TCP sockets, and return
  #  to select after reading available data. Once all data has been received,
  #  then process message.
  buf=""
  expected_length = 0
  @@mutex.synchronize {
    buf, expected_length = @@tcp_buffers[socket]
    if (!buf)
      buf = ""
      expected_length = 2
      @@tcp_buffers[socket]=[buf, expected_length]
    end
  }
  if (buf.length() < expected_length)
    begin
      input, = socket.recv_nonblock(expected_length-buf.length)
      if (input=="")
        TheLog.info("Bad response from server - no bytes read - ignoring")
        #  @TODO@ Should we do anything about this?
        return false
      end
      buf += input
    rescue
      #  Oh well - better luck next time!
      return false
    end
  end
  #  If data is complete, then return it.
  if (buf.length == expected_length)
    if (expected_length == 2)
      #  We just read the data_length field. Now we need to start reading that many bytes.
      @@mutex.synchronize {
        answersize = buf.unpack('n')[0]
        @@tcp_buffers[socket] = ["", answersize]
      }
      return tcp_read(socket)
    else
      #  We just read the data - now return it
      @@mutex.synchronize {
        @@tcp_buffers.delete(socket)
      }
      return buf
    end
  else
    @@mutex.synchronize {
      @@tcp_buffers[socket]=[buf, expected_length]
    }
    return false
  end
end