Class: Dnsruby::Resolver

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

Overview

Description

Dnsruby::Resolver is a DNS stub resolver.
This class performs queries with retries across multiple nameservers.
The system configured resolvers are used by default.

The retry policy is a combination of the Net::DNS and dnsjava approach, and has the option of :
* A total timeout for the query (defaults to 0, meaning "no total timeout")
* A retransmission system that targets the namervers concurrently once the first query round is
 complete, but in which the total time per query round is split between the number of nameservers
 targetted for the first round. and total time for query round is doubled for each query round

Note that, if a total timeout is specified, then that will apply regardless of the retry policy
(i.e. it may cut retries short).

Note also that these timeouts are distinct from the SingleResolver's packet_timeout

Timeouts apply to the initial query and response. If DNSSEC validation is to
be performed, then additional queries may be required (these are performed automatically
by Dnsruby). Each additional query will be performed with its own timeouts.
So, even with a query_timeout of 5 seconds, a response which required extensive
validation may take several times that long.
(Future versions of Dnsruby may expose finer-grained events for client tracking of
responses and validation)

== Methods

=== Synchronous
These methods raise an exception or return a response message with rcode==NOERROR

*  Dnsruby::Resolver#send_message(msg)
*  Dnsruby::Resolver#query(name [, type [, klass]])

  There are "!" versions of these two methods that return an array [response, error]
  instead of raising an error on failure.  They can be called as follows:

  response, error = resolver.send_message!(...)
  response, error = resolver.query!(...)

  If the request succeeds, response will contain the Dnsruby::Message response
  and error will be nil.

  If the request fails, response will be nil and error will contain the error raised.

=== Asynchronous
These methods use a response queue to return the response and the error

*  Dnsruby::Resolver#send_async(msg, response_queue, query_id)

== Event Loop
Dnsruby runs a pure Ruby event loop to handle I/O in a single thread.
Support for EventMachine has been deprecated.

Direct Known Subclasses

SingleResolver

Defined Under Namespace

Classes: EventType

Constant Summary collapse

DefaultQueryTimeout = 
0
DefaultPacketTimeout = 
5
DefaultRetryTimes = 
1
DefaultRetryDelay = 
5
DefaultPort = 
53
DefaultDnssec = 
true
AbsoluteMinDnssecUdpSize = 
1220
MinDnssecUdpSize = 
4096
DefaultUDPSize = 
MinDnssecUdpSize

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(*args) ⇒ Resolver

Create a new Resolver object. If no parameters are passed in, then the default

system configuration will be used. Otherwise, a Hash may be passed in with the
following optional elements :

* :port
* :use_tcp
* :tsig
* :ignore_truncation
* :src_address
* :src_address6
* :src_port
* :recurse
* :udp_size
* :config_info - see Config
* :nameserver - can be either a String or an array of Strings
* :packet_timeout
* :query_timeout
* :retry_times
* :retry_delay
* :do_caching



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# File 'lib/dnsruby/resolver.rb', line 403

def initialize(*args)
  #  @TODO@ Should we allow :namesver to be an RRSet of NS records? Would then need to randomly order them?
  @resolver_ruby = nil
  @src_address = nil
  @src_address6 = nil
  @single_res_mutex = Mutex.new
  @configured = false
  @do_caching = true
  @config = Config.new()
  reset_attributes

  #  Process args
  if args.length == 1
    if args[0].class == Hash
      args[0].keys.each do |key|
        begin
          if key == :config_info
            @config.set_config_info(args[0][:config_info])
          elsif key == :nameserver
            set_config_nameserver(args[0][:nameserver])
          elsif key == :nameservers
            set_config_nameserver(args[0][:nameservers])
          else
            send(key.to_s + '=', args[0][key])
          end
        rescue Exception => e
          Dnsruby.log.error{"Argument #{key} not valid : #{e}\n"}
        end
      end
    elsif args[0].class == String
      set_config_nameserver(args[0])
    elsif args[0].class == Config
      #  also accepts a Config object from Dnsruby::Resolv
      @config = args[0]
    end
  else
    #  Anything to do?
  end
  update
end

Instance Attribute Details

#config ⇒ Object (readonly)

The current Config



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# File 'lib/dnsruby/resolver.rb', line 121

def config
  @config
end

#dnssec ⇒ Object

Use DNSSEC for this Resolver



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# File 'lib/dnsruby/resolver.rb', line 157

def dnssec
  @dnssec
end

#do_caching ⇒ Object

Defines whether we will cache responses, or pass every request to the

upstream resolver.  This is only really useful when querying authoritative
servers (as the upstream recursive resolver is likely to cache)



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# File 'lib/dnsruby/resolver.rb', line 124

def do_caching
  @do_caching
end

#do_validation ⇒ Object

Defines whether validation is performed by default on this Resolver when the

query method is called.
Note that send_message and send_async expect a
Message object to be passed in, which is already configured to the callers
requirements.



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# File 'lib/dnsruby/resolver.rb', line 164

def do_validation
  @do_validation
end

#ignore_truncation ⇒ Object

Should truncation be ignored?

i.e. the TC bit is ignored and thus the resolver will not requery over TCP if TC is set



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# File 'lib/dnsruby/resolver.rb', line 106

def ignore_truncation
  @ignore_truncation
end

#no_tcp ⇒ Object

If no_tcp==true, then ONLY UDP will be used as a transport.

This should not generally be used, but is provided as a debugging aid.



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# File 'lib/dnsruby/resolver.rb', line 99

def no_tcp
  @no_tcp
end

#packet_timeout ⇒ Object

The timeout for any individual packet. This is the timeout used by SingleResolver



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# File 'lib/dnsruby/resolver.rb', line 142

def packet_timeout
  @packet_timeout
end

#port ⇒ Object

The port to send queries to on the resolver



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# File 'lib/dnsruby/resolver.rb', line 91

def port
  @port
end

#query_timeout ⇒ Object

Note that this timeout represents the total time a query may run for - multiple packets

can be sent to multiple nameservers in this time.
This is distinct from the SingleResolver per-packet timeout
The query_timeout is not required - it will default to 0, which means "do not use query_timeout".
If this is the case then the timeout will be dictated by the retry_times and retry_delay attributes



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

def query_timeout
  @query_timeout
end

#recurse ⇒ Object

Should the Recursion Desired bit be set?



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# File 'lib/dnsruby/resolver.rb', line 115

def recurse
  @recurse
end

#retry_delay ⇒ Object

The query will be tried across nameservers retry_times times, with a delay of retry_delay seconds

between each retry. The first time round, retry_delay will be divided by the number of nameservers
being targetted, and a new nameserver will be queried with the resultant delay.



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# File 'lib/dnsruby/resolver.rb', line 154

def retry_delay
  @retry_delay
end

#retry_times ⇒ Object

The query will be tried across nameservers retry_times times, with a delay of retry_delay seconds

between each retry. The first time round, retry_delay will be divided by the number of nameservers
being targetted, and a new nameserver will be queried with the resultant delay.



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# File 'lib/dnsruby/resolver.rb', line 154

def retry_times
  @retry_times
end

#src_address ⇒ Object

The source address to send queries from for IPv4



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# File 'lib/dnsruby/resolver.rb', line 109

def src_address
  @src_address
end

#src_address6 ⇒ Object

The source address to send queries from for IPv6



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# File 'lib/dnsruby/resolver.rb', line 112

def src_address6
  @src_address6
end

#tsig ⇒ Object

Returns the value of attribute tsig.



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# File 'lib/dnsruby/resolver.rb', line 102

def tsig
  @tsig
end

#udp_size ⇒ Object

The maximum UDP size to be used



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# File 'lib/dnsruby/resolver.rb', line 118

def udp_size
  @udp_size
end

#use_tcp ⇒ Object

Should TCP be used as a transport rather than UDP?

If use_tcp==true, then ONLY TCP will be used as a transport.



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# File 'lib/dnsruby/resolver.rb', line 95

def use_tcp
  @use_tcp
end

Class Method Details

.check_port(p, src_port = []) ⇒ Object 



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# File 'lib/dnsruby/resolver.rb', line 615

def Resolver.check_port(p, src_port=[])
  if p.class != Fixnum
    tmp_src_ports = Array.new(src_port)
    p.each do |x|
      unless Resolver.check_port(x, tmp_src_ports)
        return false
      end
      tmp_src_ports.push(x)
    end
    return true
  end
  if Resolver.port_in_range(p)
    return ! ((p == 0) && (src_port.length > 0))
  else
    Dnsruby.log.error("Illegal port (#{p})")
    log_and_raise("Illegal port #{p}", ArgumentError)
  end
end

.get_ports_from(p) ⇒ Object 



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# File 'lib/dnsruby/resolver.rb', line 638

def Resolver.get_ports_from(p)
  a = []
  if p.class == Fixnum
    a = [p]
  else
    p.each do |x|
      a.push(x)
    end
  end
  a
end

.get_tsig(args) ⇒ Object 



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# File 'lib/dnsruby/resolver.rb', line 689

def Resolver.get_tsig(args)

  tsig = nil

  if args.length == 1
    if args[0]
      if args[0].instance_of?(RR::TSIG)
        tsig = args[0]
      elsif args[0].instance_of?(Array)
        tsig = RR.new_from_hash(create_tsig_options(args))
      end
    else
      #           Dnsruby.log.debug{'TSIG signing switched off'}
      return nil
    end
  else
    tsig = RR.new_from_hash(create_tsig_options(args))
  end
  Dnsruby.log.info{"TSIG signing now using #{tsig.name}, key=#{tsig.key}"}
  tsig
end

.port_in_range(p) ⇒ Object 



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# File 'lib/dnsruby/resolver.rb', line 634

def Resolver.port_in_range(p)
  (p == 0) || ((p >= 50000) && (p <= 65535))
end

Instance Method Details

#add_config_nameservers ⇒ Object

:nodoc: all



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# File 'lib/dnsruby/resolver.rb', line 444

def add_config_nameservers # :nodoc: all
  unless @configured
    @config.get_ready
  end
  @configured = true
  @single_res_mutex.synchronize {
    #  Add the Config nameservers
    @config.nameserver.each do |ns|
      res = PacketSender.new({
          server:             ns,
          dnssec:             @dnssec,
          use_tcp:            @use_tcp,
          no_tcp:             @no_tcp,
          packet_timeout:     @packet_timeout,
          tsig:               @tsig,
          ignore_truncation:  @ignore_truncation,
          src_address:        @src_address,
          src_address6:       @src_address6,
          src_port:           @src_port,
          recurse:            @recurse,
          udp_size:           @udp_size})
      @single_resolvers.push(res) if res
    end
  }
end

#add_server(server) ⇒ Object

# Add a new SingleResolver to the list of resolvers this Resolver object will

# query.
def add_resolver(internal) # :nodoc:
  # @TODO@ Make a new PacketSender from this SingleResolver!!
  @single_resolvers.push(internal)
end



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# File 'lib/dnsruby/resolver.rb', line 527

def add_server(server)# :nodoc:
  @configured = true
  res = PacketSender.new(server)
  log_and_raise("Can't create server #{server}", ArgumentError) unless res
  update_internal_res(res)
  @single_res_mutex.synchronize { @single_resolvers.push(res) }
end

#add_src_port(p) ⇒ Object

Can be a single Fixnum or a Range or an Array

If an invalid port is selected (one reserved by
IANA), then an ArgumentError will be raised.
"0" means "any valid port" - this is only a viable
option if it is the only port in the list.
An ArgumentError will be raised if "0" is added to
an existing set of source ports.

       res.add_src_port(60000)
       res.add_src_port([60001,60005,60010])
       res.add_src_port(60015..60115)



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# File 'lib/dnsruby/resolver.rb', line 601

def add_src_port(p)
  if Resolver.check_port(p, @src_port)
    a = Resolver.get_ports_from(p)
    a.each do |x|
      if (@src_port.length > 0) && (x == 0)
        log_and_raise("src_port of 0 only allowed as only src_port value (currently #{@src_port.length} values",
            ArgumentError)
      end
      @src_port.push(x)
    end
  end
  update
end

#close ⇒ Object

Close the Resolver. Unfinished queries are terminated with OtherResolvError.



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# File 'lib/dnsruby/resolver.rb', line 378

def close
  @resolver_ruby.close if @resolver_ruby
end

#generate_timeouts(base = 0) ⇒ Object

:nodoc: all



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# File 'lib/dnsruby/resolver.rb', line 772

def generate_timeouts(base=0) # :nodoc: all
  #  These should be be pegged to the single_resolver they are targetting :
  #   e.g. timeouts[timeout1]=nameserver
  timeouts = {}
  retry_delay = @retry_delay
  #       @single_res_mutex.synchronize {
  @retry_times.times do |retry_count|
    if retry_count > 0
      retry_delay *= 2
    end

    @single_resolvers.delete(nil) # Just in case...
    @single_resolvers.each_index do |i|
      res = @single_resolvers[i]
      offset = (i * @retry_delay.to_f / @single_resolvers.length)
      if retry_count == 0
        timeouts[base + offset]=[res, retry_count]
      else
        if timeouts.has_key?(base + retry_delay + offset)
          log_and_raise('Duplicate timeout key!')
        end
        timeouts[base + retry_delay + offset]=[res, retry_count]
      end
    end
  end
  #       }
  timeouts
end

#nameserver=(n) ⇒ Object 



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# File 'lib/dnsruby/resolver.rb', line 548

def nameserver=(n)
  @configured = true
  @single_res_mutex.synchronize { @single_resolvers=[] }
  set_config_nameserver(n)
  add_config_nameservers
end

#nameservers=(ns) ⇒ Object 



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

def nameservers=(ns)
  self.nameserver=(ns)
end

#persistent_tcp=(on) ⇒ Object 



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# File 'lib/dnsruby/resolver.rb', line 732

def persistent_tcp=(on)
  @persistent_tcp = on
  update
end

#persistent_udp=(on) ⇒ Object 



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# File 'lib/dnsruby/resolver.rb', line 737

def persistent_udp=(on)
  @persistent_udp = on
  update
end

#query(name, type = Types.A, klass = Classes.IN, set_cd = @dnssec) ⇒ Object

Query for a name. If a valid Message is received, then it is returned

to the caller. Otherwise an exception (a Dnsruby::ResolvError or Dnsruby::ResolvTimeout) is raised.

  require 'dnsruby'
  res = Dnsruby::Resolver.new
  response = res.query('example.com') # defaults to Types.A, Classes.IN
  response = res.query('example.com', Types.MX)
  response = res.query('208.77.188.166') # IPv4 address so PTR query will be made
  response = res.query('208.77.188.166', Types.PTR)



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# File 'lib/dnsruby/resolver.rb', line 186

def query(name, type=Types.A, klass=Classes.IN, set_cd=@dnssec)
  msg = Message.new
  msg.do_caching = @do_caching
  msg.header.rd = 1
  msg.add_question(name, type, klass)
  msg.do_validation = @do_validation
  if @dnssec
    msg.header.cd = set_cd # We do our own validation by default
  end
  send_message(msg)
end

#query!(name, type = Types.A, klass = Classes.IN, set_cd = @dnssec) ⇒ Object

Like query, but does not raise an error when an error occurs.

Instead, it returns it.
@return a 2 element array: [response, error]



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# File 'lib/dnsruby/resolver.rb', line 201

def query!(name, type=Types.A, klass=Classes.IN, set_cd=@dnssec)
  response = nil; error = nil
  begin
    response = query(name, type, klass, set_cd)
  rescue => e
    error = e
  end
  [response, error]
end

#query_no_validation_or_recursion(name, type = Types.A, klass = Classes.IN) ⇒ Object

:nodoc: all



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# File 'lib/dnsruby/resolver.rb', line 211

def query_no_validation_or_recursion(name, type=Types.A, klass=Classes.IN) # :nodoc: all
  msg = Message.new
  msg.do_caching = @do_caching
  msg.header.rd = false
  msg.do_validation = false
  msg.add_question(name, type, klass)
  if @dnssec
    msg.header.cd = true # We do our own validation by default
  end
  send_message(msg)
end

#reset_attributes ⇒ Object

:nodoc: all



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# File 'lib/dnsruby/resolver.rb', line 479

def reset_attributes # :nodoc: all
  @resolver_ruby.reset_attributes if @resolver_ruby

  #  Attributes

  #  do_validation tells the Resolver whether to try to validate the response
  #  with DNSSEC. This should work for NSEC-signed domains, but NSEC3
  #  validation is not currently supported. This attribute now defaults to
  #  false. Please let me know if you require NSEC3 validation.
  @do_validation = false
  @query_timeout = DefaultQueryTimeout
  @retry_delay = DefaultRetryDelay
  @retry_times = DefaultRetryTimes
  @packet_timeout = DefaultPacketTimeout
  @port = DefaultPort
  @udp_size = DefaultUDPSize
  @dnssec = DefaultDnssec
  @do_caching= true
  @use_tcp = false
  @no_tcp = false
  @tsig = nil
  @ignore_truncation = false
  @config = Config.new()
  @src_address = nil
  @src_address6 = nil
  @src_port = [0]
  @recurse = true
  @single_res_mutex.synchronize {
    @single_resolvers=[]
  }
  @configured = false
end

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

Asynchronously send a Message to the server. The send can be done using just

Dnsruby. Support for EventMachine has been deprecated.

== Dnsruby pure Ruby event loop :

A client_queue is supplied by the client,
along with an optional client_query_id to identify the response. The client_query_id
is generated, if not supplied, and returned to the client.
When the response is known,
a tuple of (query_id, response_message, exception) will be added to the client_queue.

The query is sent synchronously in the caller's thread. The select thread is then used to
listen for and process the response (up to pushing it to the client_queue). The client thread
is then used to retrieve the response and deal with it.

Takes :

* msg - the message to send
* client_queue - a Queue to push the response to, when it arrives
* client_query_id - an optional ID to identify the query to the client
* use_tcp - whether to use only TCP (defaults to SingleResolver.use_tcp)

Returns :

* client_query_id - to identify the query response to the client. This ID is
generated if it is not passed in by the client

=== Example invocations :

   id = res.send_async(msg, queue)
   NOT SUPPORTED : id = res.send_async(msg, queue, use_tcp)
   id = res.send_async(msg, queue, id)
   id = res.send_async(msg, queue, id, use_tcp)

=== Example code :

  require 'dnsruby'
  res = Dnsruby::Resolver.newsend
  query_id = 10 # can be any object you like
  query_queue = Queue.new
  res.send_async(Message.new('example.com', Types.MX),  query_queue, query_id)
  query_id_2 = res.send_async(Message.new('example.com', Types.A), query_queue)
  # ...do a load of other stuff here...
  2.times do
    response_id, response, exception = query_queue.pop
    # You can check the ID to see which query has been answered
    if exception == nil
        # deal with good response
    else
        # deal with problem
    end
  end



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# File 'lib/dnsruby/resolver.rb', line 358

def send_async(msg, client_queue, client_query_id = nil)
  unless @configured
    add_config_nameservers
  end
  #       @single_res_mutex.synchronize {
  unless @resolver_ruby # @TODO@ Synchronize this?
    @resolver_ruby = ResolverRuby.new(self)
  end
  #       }
  client_query_id = @resolver_ruby.send_async(msg, client_queue, client_query_id)
  if @single_resolvers.length == 0
    Thread.start {
      sleep(@query_timeout == 0 ? 1 : @query_timeout)
      client_queue.push([client_query_id, nil, ResolvTimeout.new('Query timed out - no nameservers configured')])
    }
  end
  client_query_id
end

#send_message(message) ⇒ Object

Send a message, and wait for the response. If a valid Message is received, then it is returned

to the caller. Otherwise an exception (a Dnsruby::ResolvError or Dnsruby::ResolvTimeout) is raised.

send_async is called internally.

example :

  require 'dnsruby'
  include Dnsruby
  res = Dnsruby::Resolver.new
  begin
  response = res.send_message(Message.new('example.com', Types.MX))
  rescue ResolvError
    # ...
  rescue ResolvTimeout
    # ...
  end



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# File 'lib/dnsruby/resolver.rb', line 240

def send_message(message)
  Dnsruby.log.debug{'Resolver : sending message'}
  q = Queue.new
  send_async(message, q)

  _id, result, error = q.pop

  if error
    raise error
  else
    result
  end
end

#send_message!(message) ⇒ Object

Like send_message, but does not raise an error when an error occurs.

Instead, it returns it.
@return a 2 element array: [response, error]



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# File 'lib/dnsruby/resolver.rb', line 257

def send_message!(message)
  response = nil; error = nil
  begin
    response = send_message(message)
  rescue => e
    error = e
  end
  [response, error]
end

#send_plain_message(message) ⇒ Object

This method takes a Message (supplied by the client), and sends it to

the configured nameservers. No changes are made to the Message before it
is sent (TSIG signatures will be applied if configured on the Resolver).
Retries are handled as the Resolver is configured to do.
Incoming responses to the query are not cached or validated (although TCP
fallback will be performed if the TC bit is set and the (Single)Resolver has
ignore_truncation set to false).
Note that the Message is left untouched - this means that no OPT records are
added, even if the UDP transport for the server is specified at more than 512
bytes. If it is desired to use EDNS for this packet, then you should call
the Dnsruby::PacketSender#prepare_for_dnssec(msg), or
Dnsruby::PacketSender#add_opt_rr(msg)
The return value from this method is the [response, error] tuple. Either of
these values may be nil - it is up to the client to check.

example :

  require 'dnsruby'
  include Dnsruby
  res = Dnsruby::Resolver.new
  response, error = res.send_plain_message(Message.new('example.com', Types.MX))
  if error
    print "Error returned : #{error}\n"
  else
    process_response(response)
  end



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# File 'lib/dnsruby/resolver.rb', line 293

def send_plain_message(message)
  Dnsruby::TheLog.debug('Resolver : send_plain_message')
  message.do_caching = false
  message.do_validation = false
  message.send_raw = true
  q = Queue.new
  send_async(message, q)
  _id, result, error = q.pop
  [result, error]
end

#set_config_nameserver(n) ⇒ Object 



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# File 'lib/dnsruby/resolver.rb', line 470

def set_config_nameserver(n)
  #  @TODO@ Should we allow NS RRSet here? If so, then .sort_by {rand}
  @config.get_ready unless @configured
  @configured = true

  @config.nameserver = n.kind_of?(String) ? [n] : n
  add_config_nameservers
end

#single_res_mutex ⇒ Object

:nodoc: all



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# File 'lib/dnsruby/resolver.rb', line 768

def single_res_mutex # :nodoc: all
  @single_res_mutex
end

#single_resolvers ⇒ Object

}



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# File 'lib/dnsruby/resolver.rb', line 134

def single_resolvers # :nodoc:
  unless @configured
    add_config_nameservers
  end
  @single_resolvers
end

#single_resolvers=(s) ⇒ Object

The array of SingleResolvers used for sending query messages

attr_accessor :single_resolvers # :nodoc:



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# File 'lib/dnsruby/resolver.rb', line 128

def single_resolvers=(s) # :nodoc:
  @configured = true
  #       @single_res_mutex.synchronize {
  @single_resolvers = s
  #       }
end

#src_port ⇒ Object

The source port to send queries from

Returns either a single Fixnum or an Array
e.g. '0', or '[60001, 60002, 60007]'

Defaults to 0 - random port



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# File 'lib/dnsruby/resolver.rb', line 570

def src_port
  @src_port.length == 1 ? @src_port[0] : @src_port
end

#src_port=(p) ⇒ Object

Can be a single Fixnum or a Range or an Array

If an invalid port is selected (one reserved by
IANA), then an ArgumentError will be raised.

       res.src_port=0
       res.src_port=[60001,60005,60010]
       res.src_port=60015..60115



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# File 'lib/dnsruby/resolver.rb', line 582

def src_port=(p)
  if Resolver.check_port(p)
    @src_port = Resolver.get_ports_from(p)
    update
  end
end

#update ⇒ Object

:nodoc: all



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# File 'lib/dnsruby/resolver.rb', line 512

def update # :nodoc: all
  #  Update any resolvers we have with the latest config
  @single_res_mutex.synchronize do
    @single_resolvers.delete(nil) # Just in case...
    @single_resolvers.each { |res| update_internal_res(res) }
  end
end

#update_internal_res(res) ⇒ Object 



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# File 'lib/dnsruby/resolver.rb', line 535

def update_internal_res(res)
  [:port, :use_tcp, :no_tcp, :tsig, :ignore_truncation, :packet_timeout,
    :src_address, :src_address6, :src_port, :recurse,
    :udp_size, :dnssec].each do |param|

    res.send(param.to_s + '=', instance_variable_get('@' + param.to_s))
  end
end