Class: Resolv::DNS

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

Overview

Resolv::DNS is a DNS stub resolver.

Information taken from the following places:

  • STD0013
  • RFC 1035
  • ftp://ftp.isi.edu/in-notes/iana/assignments/dns-parameters
  • etc.

Defined Under Namespace

Modules: Label, OpCode, RCode Classes: Config, DecodeError, EncodeError, Message, Name, Query, Requester, Resource

Constant Summary collapse

Port =

Default DNS Port

53
UDPSize =

Default DNS UDP packet size

512
DNSThreadGroup =

Group of DNS resolver threads

ThreadGroup.new

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(config_info = nil) ⇒ DNS

Creates a new DNS resolver.

config_info can be:

nil

Uses /etc/resolv.conf.

String

Path to a file using /etc/resolv.conf's format.

Hash

Must contain :nameserver, :search and :ndots keys.

Example:

Resolv::DNS.new(:nameserver => ['210.251.121.21'],
              :search => ['ruby-lang.org'],
              :ndots => 1)


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# File 'lib/resolv.rb', line 323

def initialize(config_info=nil)
  @mutex = Mutex.new
  @config = Config.new(config_info)
  @initialized = nil
end

Class Method Details

.open(*args) ⇒ Object

Creates a new DNS resolver. See Resolv::DNS.new for argument details.

Yields the created DNS resolver to the block, if given, otherwise returns it.



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# File 'lib/resolv.rb', line 298

def self.open(*args)
  dns = new(*args)
  return dns unless block_given?
  begin
    yield dns
  ensure
    dns.close
  end
end

Instance Method Details

#close ⇒ Object

Closes the DNS resolver.



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# File 'lib/resolv.rb', line 349

def close
  @mutex.synchronize {
    if @initialized
      @requester.close if @requester
      @requester = nil
      @initialized = false
    end
  }
end

#each_address(name) ⇒ Object

Iterates over all IP addresses for name retrieved from the DNS resolver.

name can be a Resolv::DNS::Name or a String. Retrieved addresses will be a Resolv::IPv4 or Resolv::IPv6



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# File 'lib/resolv.rb', line 389

def each_address(name)
  each_resource(name, Resource::IN::A) {|resource| yield resource.address}
  each_resource(name, Resource::IN::AAAA) {|resource| yield resource.address}
end

#each_name(address) ⇒ Object

Iterates over all hostnames for address retrieved from the DNS resolver.

address must be a Resolv::IPv4, Resolv::IPv6 or a String. Retrieved names will be Resolv::DNS::Name instances.



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# File 'lib/resolv.rb', line 424

def each_name(address)
  case address
  when Name
    ptr = address
  when IPv4::Regex
    ptr = IPv4.create(address).to_name
  when IPv6::Regex
    ptr = IPv6.create(address).to_name
  else
    raise ResolvError.new("cannot interpret as address: #{address}")
  end
  each_resource(ptr, Resource::IN::PTR) {|resource| yield resource.name}
end

#each_resource(name, typeclass, &proc) ⇒ Object

Iterates over all typeclass DNS resources for name. See #getresource for argument details.



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# File 'lib/resolv.rb', line 480

def each_resource(name, typeclass, &proc)
  lazy_initialize
  q = Queue.new
  senders = {}
  begin
    @config.resolv(name) {|candidate, tout, nameserver|
      msg = Message.new
      msg.rd = 1
      msg.add_question(candidate, typeclass)
      unless sender = senders[[candidate, nameserver]]
        sender = senders[[candidate, nameserver]] =
          @requester.sender(msg, candidate, q, nameserver)
      end
      sender.send
      reply = reply_name = nil
      timeout(tout, ResolvTimeout) { reply, reply_name = q.pop }
      case reply.rcode
      when RCode::NoError
        extract_resources(reply, reply_name, typeclass, &proc)
        return
      when RCode::NXDomain
        raise Config::NXDomain.new(reply_name.to_s)
      else
        raise Config::OtherResolvError.new(reply_name.to_s)
      end
    }
  ensure
    @requester.delete(q)
  end
end

#extract_resources(msg, name, typeclass) ⇒ Object

:nodoc:



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# File 'lib/resolv.rb', line 511

def extract_resources(msg, name, typeclass) # :nodoc:
  if typeclass < Resource::ANY
    n0 = Name.create(name)
    msg.each_answer {|n, ttl, data|
      yield data if n0 == n
    }
  end
  yielded = false
  n0 = Name.create(name)
  msg.each_answer {|n, ttl, data|
    if n0 == n
      case data
      when typeclass
        yield data
        yielded = true
      when Resource::CNAME
        n0 = data.name
      end
    end
  }
  return if yielded
  msg.each_answer {|n, ttl, data|
    if n0 == n
      case data
      when typeclass
        yield data
      end
    end
  }
end

#getaddress(name) ⇒ Object

Gets the IP address of name from the DNS resolver.

name can be a Resolv::DNS::Name or a String. Retrieved address will be a Resolv::IPv4 or Resolv::IPv6

Raises:



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# File 'lib/resolv.rb', line 365

def getaddress(name)
  each_address(name) {|address| return address}
  raise ResolvError.new("DNS result has no information for #{name}")
end

#getaddresses(name) ⇒ Object

Gets all IP addresses for name from the DNS resolver.

name can be a Resolv::DNS::Name or a String. Retrieved addresses will be a Resolv::IPv4 or Resolv::IPv6



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# File 'lib/resolv.rb', line 376

def getaddresses(name)
  ret = []
  each_address(name) {|address| ret << address}
  return ret
end

#getname(address) ⇒ Object

Gets the hostname for address from the DNS resolver.

address must be a Resolv::IPv4, Resolv::IPv6 or a String. Retrieved name will be a Resolv::DNS::Name.

Raises:



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# File 'lib/resolv.rb', line 400

def getname(address)
  each_name(address) {|name| return name}
  raise ResolvError.new("DNS result has no information for #{address}")
end

#getnames(address) ⇒ Object

Gets all hostnames for address from the DNS resolver.

address must be a Resolv::IPv4, Resolv::IPv6 or a String. Retrieved names will be Resolv::DNS::Name instances.



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# File 'lib/resolv.rb', line 411

def getnames(address)
  ret = []
  each_name(address) {|name| ret << name}
  return ret
end

#getresource(name, typeclass) ⇒ Object

Look up the typeclass DNS resource of name.

name must be a Resolv::DNS::Name or a String.

typeclass should be one of the following:

  • Resolv::DNS::Resource::IN::A
  • Resolv::DNS::Resource::IN::AAAA
  • Resolv::DNS::Resource::IN::ANY
  • Resolv::DNS::Resource::IN::CNAME
  • Resolv::DNS::Resource::IN::HINFO
  • Resolv::DNS::Resource::IN::MINFO
  • Resolv::DNS::Resource::IN::MX
  • Resolv::DNS::Resource::IN::NS
  • Resolv::DNS::Resource::IN::PTR
  • Resolv::DNS::Resource::IN::SOA
  • Resolv::DNS::Resource::IN::TXT
  • Resolv::DNS::Resource::IN::WKS

Returned resource is represented as a Resolv::DNS::Resource instance, i.e. Resolv::DNS::Resource::IN::A.

Raises:



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# File 'lib/resolv.rb', line 461

def getresource(name, typeclass)
  each_resource(name, typeclass) {|resource| return resource}
  raise ResolvError.new("DNS result has no information for #{name}")
end

#getresources(name, typeclass) ⇒ Object

Looks up all typeclass DNS resources for name. See #getresource for argument details.



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# File 'lib/resolv.rb', line 470

def getresources(name, typeclass)
  ret = []
  each_resource(name, typeclass) {|resource| ret << resource}
  return ret
end

#lazy_initialize ⇒ Object

:nodoc:



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# File 'lib/resolv.rb', line 329

def lazy_initialize # :nodoc:
  @mutex.synchronize {
    unless @initialized
      @config.lazy_initialize

      if nameserver = @config.single?
        @requester = Requester::ConnectedUDP.new(nameserver)
      else
        @requester = Requester::UnconnectedUDP.new
      end

      @initialized = true
    end
  }
  self
end