class Net::DNS::Resolver

Net::DNS::Resolver - DNS resolver class

The Net::DNS::Resolver class implements a complete DNS resolver written in pure Ruby, without a single C line of code. It has all of the tipical properties of an evoluted resolver, and a bit of OO which comes from having used Ruby.

This project started as a porting of the Net::DNS Perl module, written by Martin Fuhr, but turned out (in the last months) to be an almost complete rewriting. Well, maybe some of the features of the Perl version are still missing, but guys, at least this is readable code!

Environment

The Following Environment variables can also be used to configure the resolver:

Constants

C
Defaults

An hash with the defaults values of almost all the configuration parameters of a resolver object. See the description for each parameter to have an explanation of its usage.

Public Class Methods

new(config = {}) click to toggle source

Creates a new resolver object.

Argument config can either be empty or be an hash with some configuration parameters. To know what each parameter do, look at the description of each. Some example:

# Use the sistem defaults
res = Net::DNS::Resolver.new

# Specify a configuration file
res = Net::DNS::Resolver.new(:config_file => '/my/dns.conf')

# Set some option
res = Net::DNS::Resolver.new(:nameservers => "172.16.1.1",
                             :recursive => false,
                             :retry => 10)

Config file

Net::DNS::Resolver uses a config file to read the usual values a resolver needs, such as nameserver list and domain names. On UNIX systems the defaults are read from the following files, in the order indicated:

  • /etc/resolv.conf

  • $HOME/.resolv.conf

  • ./.resolv.conf

The following keywords are recognized in resolver configuration files:

  • domain: the default domain.

  • search: a space-separated list of domains to put in the search list.

  • nameserver: a space-separated list of nameservers to query.

Files except for /etc/resolv.conf must be owned by the effective userid running the program or they won't be read. In addition, several environment variables can also contain configuration information; see Environment in the main description for Resolver class.

On Windows Systems, an attempt is made to determine the system defaults using the registry. This is still a work in progress; systems with many dynamically configured network interfaces may confuse Net::DNS.

You can include a configuration file of your own when creating a resolver object:

# Use my own configuration file
my $res = Net::DNS::Resolver->new(config_file => '/my/dns.conf');

This is supported on both UNIX and Windows. Values pulled from a custom configuration file override the the system's defaults, but can still be overridden by the other arguments to ::new.

Explicit arguments to ::new override both the system's defaults and the values of the custom configuration file, if any.

Parameters

The following arguments to ::new are supported:

  • nameservers: an array reference of nameservers to query.

  • searchlist: an array reference of domains.

  • recurse

  • debug

  • domain

  • port

  • srcaddr

  • srcport

  • #tcp_timeout

  • #udp_timeout

  • retrans

  • retry

  • usevc

  • stayopen

  • igntc

  • defnames

  • dnsrch

  • persistent_tcp

  • persistent_udp

  • dnssec

For more information on any of these options, please consult the method of the same name.

Disclaimer

Part of the above documentation is taken from the one in the Net::DNS::Resolver Perl module.

# File lib/net/dns/resolver.rb, line 239
def initialize(config = {})
  raise ArgumentError, "Expected `config' to be a Hash" unless config.is_a?(Hash)

  # config.downcase_keys!
  @config = Defaults.merge config
  @raw = false

  # New logger facility
  @logger = Logger.new(@config[:log_file])
  @logger.level = $DEBUG ? Logger::DEBUG : Logger::WARN

  #------------------------------------------------------------
  # Resolver configuration will be set in order from:
  # 1) initialize arguments
  # 2) ENV variables
  # 3) config file
  # 4) defaults (and /etc/resolv.conf for config)
  #------------------------------------------------------------



  #------------------------------------------------------------
  # Parsing config file
  #------------------------------------------------------------
  parse_config_file

  #------------------------------------------------------------
  # Parsing ENV variables
  #------------------------------------------------------------
  parse_environment_variables

  #------------------------------------------------------------
  # Parsing arguments
  #------------------------------------------------------------
  config.each do |key,val|
    next if key == :log_file or key == :config_file
    begin
      eval "self.#{key.to_s} = val"
    rescue NoMethodError
      raise ArgumentError, "Option #{key} not valid"
    end
  end
end
platform_windows?() click to toggle source

Returns true if running on a Windows platform.

Note. This method doesn't rely on the RUBY_PLATFORM constant because the comparison will fail when running on JRuby. On JRuby RUBY_PLATFORM == 'java'.

# File lib/net/dns/resolver.rb, line 142
def platform_windows?
  !!(C["host_os"] =~ /msdos|mswin|djgpp|mingw/i)
end
start(*params) click to toggle source

Quick resolver method. Bypass the configuration using the defaults.

Net::DNS::Resolver.start "www.google.com"
# File lib/net/dns/resolver.rb, line 133
def start(*params)
  new.search(*params)
end

Public Instance Methods

axfr(name, cls = Net::DNS::IN) click to toggle source

Performs a zone transfer for the zone passed as a parameter.

It is actually only a wrapper to a send with type set as Net::DNS::AXFR, since it is using the same infrastucture.

# File lib/net/dns/resolver.rb, line 1036
def axfr(name, cls = Net::DNS::IN)
  @logger.info "Requested AXFR transfer, zone #{name} class #{cls}"
  query(name, Net::DNS::AXFR, cls)
end
defname()
Alias for: defname?
defname=(bool) click to toggle source

Set the flag defname in a boolean state. if defname is true, calls to #query will append the default domain to names that contain no dots. Example:

# Domain example.com
res.defname = true
res.query("machine1")
  #=> This will perform a query for machine1.example.com

Default is true.

# File lib/net/dns/resolver.rb, line 634
def defname=(bool)
  case bool
  when TrueClass,FalseClass
    @config[:defname] = bool
    @logger.info("Defname state changed to #{bool}")
  else
    raise ArgumentError, "Argument must be boolean"
  end
end
defname?() click to toggle source

Checks whether the defname flag has been activate.

# File lib/net/dns/resolver.rb, line 617
def defname?
  @config[:defname]
end
Also aliased as: defname
dns_search=(bool) click to toggle source

Set the flag dns_search in a boolean state. If dns_search is true, when using the #search method will be applied the search list. Default is true.

# File lib/net/dns/resolver.rb, line 653
def dns_search=(bool)
  case bool
  when TrueClass,FalseClass
    @config[:dns_search] = bool
    @logger.info("DNS search state changed to #{bool}")
  else
    raise ArgumentError, "Argument must be boolean"
  end
end
dnsrch()
Alias for: dns_search
domain() click to toggle source

Return a string with the default domain.

# File lib/net/dns/resolver.rb, line 381
def domain
  @config[:domain].inspect
end
domain=(name) click to toggle source

Set the domain for the query.

# File lib/net/dns/resolver.rb, line 386
def domain=(name)
  @config[:domain] = name if valid? name
end
ignore_truncated()
Alias for: ignore_truncated?
ignore_truncated=(bool) click to toggle source
# File lib/net/dns/resolver.rb, line 698
def ignore_truncated=(bool)
  case bool
  when TrueClass,FalseClass
    @config[:ignore_truncated] = bool
    @logger.info("Ignore truncated flag changed to #{bool}")
  else
    raise ArgumentError, "Argument must be boolean"
  end
end
ignore_truncated?() click to toggle source
# File lib/net/dns/resolver.rb, line 693
def ignore_truncated?
  @config[:ignore_truncated]
end
Also aliased as: ignore_truncated
inspect()
Alias for: state
log_file=(log) click to toggle source

Set a new log file for the logger facility of the resolver class. Could be a file descriptor too:

res.log_file = $stderr

Note that a new logging facility will be create, destroing the old one, which will then be impossibile to recover.

# File lib/net/dns/resolver.rb, line 785
def log_file=(log)
  @logger.close
  @config[:log_file] = log
  @logger = Logger.new(@config[:log_file])
  @logger.level = $DEBUG ? Logger::DEBUG : Logger::WARN
end
log_level=(level) click to toggle source

Set the log level for the built-in logging facility.

The log level can be one of the following:

  • Net::DNS::DEBUG

  • Net::DNS::INFO

  • Net::DNS::WARN

  • Net::DNS::ERROR

  • Net::DNS::FATAL

Note that if the global variable $DEBUG is set (like when the -d switch is used at the command line) the logger level is automatically set at DEGUB.

For further informations, see Logger documentation in the Ruby standard library.

# File lib/net/dns/resolver.rb, line 835
def log_level=(level)
  @logger.level = level
end
logger=(logger) click to toggle source

This one permits to have a personal logger facility to handle resolver messages, instead of new built-in one, which is set up for a +$stdout+ (or +$stderr+) use.

If you want your own logging facility you can create a new instance of the Logger class:

log = Logger.new("/tmp/resolver.log","weekly",2*1024*1024)
log.level = Logger::DEBUG
log.progname = "ruby_resolver"

and then pass it to the resolver:

res.logger = log

Note that this will destroy the precedent logger.

# File lib/net/dns/resolver.rb, line 809
def logger=(logger)
  if logger.kind_of? Logger
    @logger.close
    @logger = logger
  else
    raise ArgumentError, "Argument must be an instance of Logger class"
  end
end
mx(name, cls = Net::DNS::IN) click to toggle source

Performs an MX query for the domain name passed as parameter.

It actually uses the same methods a normal Resolver query would use, but automatically sort the results based on preferences and returns an ordered array.

res = Net::DNS::Resolver.new
res.mx("google.com")
# File lib/net/dns/resolver.rb, line 1050
def mx(name, cls = Net::DNS::IN)
  arr = []
  query(name, Net::DNS::MX, cls).answer.each do |entry|
    arr << entry if entry.type == 'MX'
  end
  arr.sort_by { |a| a.preference }
end
nameserver()
Alias for: nameservers
nameservers() click to toggle source

Get the list of resolver nameservers, in a dotted decimal format-

res.nameservers
  #=> ["192.168.0.1","192.168.0.2"]
# File lib/net/dns/resolver.rb, line 324
def nameservers
  @config[:nameservers].map(&:to_s)
end
Also aliased as: nameserver
nameservers=(arg) click to toggle source

Set the list of resolver nameservers. arg can be a single ip address or an array of addresses.

res.nameservers = "192.168.0.1"
res.nameservers = ["192.168.0.1","192.168.0.2"]

If you want you can specify the addresses as IPAddr instances.

ip = IPAddr.new("192.168.0.3")
res.nameservers << ip
#=> ["192.168.0.1","192.168.0.2","192.168.0.3"]

The default is 127.0.0.1 (localhost)

# File lib/net/dns/resolver.rb, line 344
def nameservers=(arg)
  case arg
  when String
    begin
      @config[:nameservers] = [IPAddr.new(arg)]
      @logger.info "Nameservers list changed to value #{@config[:nameservers].inspect}"
    rescue ArgumentError # arg is in the name form, not IP
      nameservers_from_name(arg)
    end
  when IPAddr
    @config[:nameservers] = [arg]
    @logger.info "Nameservers list changed to value #{@config[:nameservers].inspect}"
  when Array
    @config[:nameservers] = []
    arg.each do |x|
      @config[:nameservers] << case x
                               when String
                                 begin
                                   IPAddr.new(x)
                                 rescue ArgumentError
                                   nameservers_from_name(arg)
                                   return
                                 end
                               when IPAddr
                                 x
                               else
                                 raise ArgumentError, "Wrong argument format"
                               end
    end
    @logger.info "Nameservers list changed to value #{@config[:nameservers].inspect}"
  else
    raise ArgumentError, "Wrong argument format, neither String, Array nor IPAddr"
  end
end
packet_size() click to toggle source

Return the defined size of the packet.

# File lib/net/dns/resolver.rb, line 391
def packet_size
  @config[:packet_size]
end
port() click to toggle source

Get the port number to which the resolver sends queries.

puts "Sending queries to port #{res.port}"
# File lib/net/dns/resolver.rb, line 399
def port
  @config[:port]
end
port=(num) click to toggle source

Set the port number to which the resolver sends queries. This can be useful for testing a nameserver running on a non-standard port.

res.port = 10053

The default is port 53.

# File lib/net/dns/resolver.rb, line 410
def port=(num)
  if (0..65535).include? num
    @config[:port] = num
    @logger.info "Port number changed to #{num}"
  else
    raise ArgumentError, "Wrong port number #{num}"
  end
end
print()
Alias for: state
query(name,type=Net::DNS::A,cls=Net::DNS::IN) click to toggle source

Performs a DNS query for the given name; the search list is not applied. If the name doesn't contain any dots and defname is true then the default domain will be appended.

The record type and class can be omitted; they default to A and IN. If the name looks like an IP address (IPv4 or IPv6), then an appropriate PTR query will be performed.

packet = res.query('mailhost')
packet = res.query('mailhost.example.com')
packet = res.query('example.com', Net::DNS::MX)
packet = res.query('user.passwd.example.com', Net::DNS::TXT, Net::DNS::HS)

If the name is an IP address (Ipv4 or IPv6), in the form of a string or a IPAddr object, then an appropriate PTR query will be performed:

ip = IPAddr.new("172.16.100.2")
packet = res.query(ip)
packet = res.query("192.168.10.254")

Returns a Net::DNS::Packet object. If you need to examine the response packet whether it contains any answers or not, use the #query method instead.

# File lib/net/dns/resolver.rb, line 915
def query(name,type=Net::DNS::A,cls=Net::DNS::IN)

  return send(name,type,cls) if name.class == IPAddr

  # If the name doesn't contain any dots then append the default domain.
  if name !~ /\./ and name !~ /:/ and @config[:defname]
    name += "." + @config[:domain]
  end

  @logger.debug "Query(#{name},#{Net::DNS::RR::Types.new(type)},#{Net::DNS::RR::Classes.new(cls)})"

  send(name,type,cls)

end
recurse()
Alias for: recursive?
recurse=(bool)
Alias for: recursive=
recursive()
Alias for: recursive?
recursive=(bool) click to toggle source

Sets whether or not the resolver should perform recursive queries. Default is true.

res.recursive = false # perform non-recursive query
# File lib/net/dns/resolver.rb, line 582
def recursive=(bool)
  case bool
  when TrueClass,FalseClass
    @config[:recursive] = bool
    @logger.info("Recursive state changed to #{bool}")
  else
    raise ArgumentError, "Argument must be boolean"
  end
end
Also aliased as: recurse=
recursive?() click to toggle source

This method will return true if the resolver is configured to perform recursive queries.

print "The resolver will perform a "
print res.recursive? ? "" : "not "
puts "recursive query"
# File lib/net/dns/resolver.rb, line 571
def recursive?
  @config[:recursive]
end
Also aliased as: recurse, recursive
retrans()
Alias for: retry_interval
retrans=(num)
Alias for: retry_interval=
retry_interval() click to toggle source

Return the retrasmission interval (in seconds) the resolvers has been set on.

# File lib/net/dns/resolver.rb, line 528
def retry_interval
  @config[:retry_interval]
end
Also aliased as: retrans
retry_interval=(num) click to toggle source

Set the retrasmission interval in seconds. Default 5 seconds.

# File lib/net/dns/resolver.rb, line 534
def retry_interval=(num)
  if num > 0
    @config[:retry_interval] = num
    @logger.info "Retransmission interval changed to #{num} seconds"
  else
    raise ArgumentError, "Interval must be positive"
  end
end
Also aliased as: retrans=
retry_number() click to toggle source

The number of times the resolver will try a query.

puts "Will try a max of #{res.retry_number} queries"
# File lib/net/dns/resolver.rb, line 548
def retry_number
  @config[:retry_number]
end
retry_number=(num) click to toggle source

Set the number of times the resolver will try a query. Default 4 times.

# File lib/net/dns/resolver.rb, line 554
def retry_number=(num)
  if num.kind_of? Integer and num > 0
    @config[:retry_number] = num
    @logger.info "Retrasmissions number changed to #{num}"
  else
    raise ArgumentError, "Retry value must be a positive integer"
  end
end
searchlist() click to toggle source

Get the resolver search list, returned as an array of entries.

res.searchlist
#=> ["example.com","a.example.com","b.example.com"]
# File lib/net/dns/resolver.rb, line 288
def searchlist
  @config[:searchlist].inspect
end
searchlist=(arg) click to toggle source

Set the resolver searchlist. arg can be a single string or an array of strings.

res.searchstring = "example.com"
res.searchstring = ["example.com","a.example.com","b.example.com"]

Note that you can also append a new name to the searchlist.

res.searchlist << "c.example.com"
res.searchlist
#=> ["example.com","a.example.com","b.example.com","c.example.com"]

The default is an empty array.

# File lib/net/dns/resolver.rb, line 306
def searchlist=(arg)
  case arg
  when String
    @config[:searchlist] = [arg] if valid? arg
    @logger.info "Searchlist changed to value #{@config[:searchlist].inspect}"
  when Array
    @config[:searchlist] = arg if arg.all? {|x| valid? x}
    @logger.info "Searchlist changed to value #{@config[:searchlist].inspect}"
  else
    raise ArgumentError, "Wrong argument format, neither String nor Array"
  end
end
source_address() click to toggle source

Get the local address from which the resolver sends queries

puts "Sending queries using source address #{res.source_address}"
# File lib/net/dns/resolver.rb, line 455
def source_address
  @config[:source_address].to_s
end
Also aliased as: srcaddr
source_address=(addr) click to toggle source

Set the local source address from which the resolver sends its queries.

res.source_address = "172.16.100.1"
res.source_address = IPAddr.new("172.16.100.1")

You can specify arg as either a string containing the ip address or an instance of IPAddr class.

Normally this can be used to force queries out a specific interface on a multi-homed host. In this case, you should of course need to know the addresses of the interfaces.

Another way to use this option is for some kind of spoofing attacks towards weak nameservers, to probe the security of your network. This includes specifing ranged attacks such as DoS and others. For a paper on DNS security, checks www.marcoceresa.com/security/

Note that if you want to set a non-binded source address you need root priviledges, as raw sockets will be used to generate packets. The class will then generate an exception if you're not root.

The default is 0.0.0.0, meaning any local address (chosen on routing needs).

# File lib/net/dns/resolver.rb, line 489
def source_address=(addr)
  unless addr.respond_to? :to_s
    raise ArgumentError, "Wrong address argument #{addr}"
  end

  begin
    port = rand(64000)+1024
    @logger.warn "Try to determine state of source address #{addr} with port #{port}"
    a = TCPServer.new(addr.to_s,port)
  rescue SystemCallError => e
    case e.errno
    when 98 # Port already in use!
      @logger.warn "Port already in use"
      retry
    when 99 # Address is not valid: raw socket
      @raw = true
      @logger.warn "Using raw sockets"
    else
      raise SystemCallError, e
    end
  ensure
    a.close
  end

  case addr
  when String
    @config[:source_address] = IPAddr.new(string)
    @logger.info "Using new source address: #{@config[:source_address]}"
  when IPAddr
    @config[:source_address] = addr
    @logger.info "Using new source address: #{@config[:source_address]}"
  else
    raise ArgumentError, "Unknown dest_address format"
  end
end
Also aliased as: srcaddr=
source_address_inet6() click to toggle source

Get the local ipv6 address from which the resolver sends queries

# File lib/net/dns/resolver.rb, line 462
def source_address_inet6
  @config[:source_address_inet6].to_s
end
source_port() click to toggle source

Get the value of the source port number.

puts "Sending queries using port #{res.source_port}"
# File lib/net/dns/resolver.rb, line 423
def source_port
  @config[:source_port]
end
Also aliased as: srcport
source_port=(num) click to toggle source

Set the local source port from which the resolver sends its queries.

res.source_port = 40000

Note that if you want to set a port you need root priviledges, as raw sockets will be used to generate packets. The class will then generate the exception ResolverPermissionError if you're not root.

The default is 0, which means that the port will be chosen by the underlaying layers.

# File lib/net/dns/resolver.rb, line 439
def source_port=(num)
  unless root?
    raise ResolverPermissionError, "Are you root?"
  end
  if (0..65535).include?(num)
    @config[:source_port] = num
  else
    raise ArgumentError, "Wrong port number #{num}"
  end
end
Also aliased as: srcport=
srcaddr()
Alias for: source_address
srcaddr=(addr)
Alias for: source_address=
srcport()
Alias for: source_port
srcport=(num)
Alias for: source_port=
state() click to toggle source

Return a string representing the resolver state, suitable for printing on the screen.

puts "Resolver state:"
puts res.state
# File lib/net/dns/resolver.rb, line 599
def state
  str = ";; RESOLVER state:\n;; "
  i = 1
  @config.each do |key,val|
    if key == :log_file or key == :config_file
      str << "#{key}: #{val} \t"
    else
      str << "#{key}: #{eval(key.to_s)} \t"
    end
    str << "\n;; " if i % 2 == 0
    i += 1
  end
  str
end
Also aliased as: print, inspect
tcp_timeout() click to toggle source

Return an object representing the value of the stored TCP timeout the resolver will use in is queries. This object is an instance of the class TcpTimeout, and two methods are available for printing informations: Net::DNS::Resolver::DnsTimeout#to_s and Net::DNS::Resolver::DnsTimeout#pretty_to_s.

Here's some example:

puts "Timeout of #{res.tcp_timeout} seconds" # implicit to_s
  #=> Timeout of 150 seconds

puts "You set a timeout of " + res.tcp_timeout.pretty_to_s
  #=> You set a timeout of 2 minutes and 30 seconds

If the timeout is infinite, a string “infinite” will be returned.

# File lib/net/dns/resolver.rb, line 724
def tcp_timeout
  @config[:tcp_timeout].to_s
end
tcp_timeout=(secs) click to toggle source

Set the value of TCP timeout for resolver queries that will be performed using TCP. A value of 0 means that the timeout will be infinite. The value is stored internally as a TcpTimeout object, see the description for #tcp_timeout

Default is 5 seconds.

# File lib/net/dns/resolver.rb, line 736
def tcp_timeout=(secs)
  @config[:tcp_timeout] = TcpTimeout.new(secs)
  @logger.info("New TCP timeout value: #{@config[:tcp_timeout]} seconds")
end
udp_timeout() click to toggle source

Return an object representing the value of the stored UDP timeout the resolver will use in is queries. This object is an instance of the class UdpTimeout, and two methods are available for printing information: Net::DNS::Resolver::DnsTimeout#to_s and Net::DNS::Resolver::DnsTimeout#pretty_to_s.

Here's some example:

puts "Timeout of #{res.udp_timeout} seconds" # implicit to_s
  #=> Timeout of 150 seconds

puts "You set a timeout of " + res.udp_timeout.pretty_to_s
  #=> You set a timeout of 2 minutes and 30 seconds

If the timeout is zero, a string “not defined” will be returned.

# File lib/net/dns/resolver.rb, line 758
def udp_timeout
  @config[:udp_timeout].to_s
end
udp_timeout=(secs) click to toggle source

Set the value of UDP timeout for resolver queries that will be performed using UDP. A value of 0 means that the timeout will not be used, and the resolver will use only retry_number and retry_interval parameters.

Default is 5 seconds.

The value is stored internally as a UdpTimeout object, see the description for #udp_timeout.

# File lib/net/dns/resolver.rb, line 772
def udp_timeout=(secs)
  @config[:udp_timeout] = UdpTimeout.new(secs)
  @logger.info("New UDP timeout value: #{@config[:udp_timeout]} seconds")
end
use_tcp()
Alias for: use_tcp?
use_tcp=(bool) click to toggle source

If use_tcp is true, the resolver will perform all queries using TCP virtual circuits instead of UDP datagrams, which is the default for the DNS protocol.

res.use_tcp = true
res.query "host.example.com"
  #=> Sending TCP segments...

Default is false.

# File lib/net/dns/resolver.rb, line 682
def use_tcp=(bool)
  case bool
  when TrueClass,FalseClass
    @config[:use_tcp] = bool
    @logger.info("Use tcp flag changed to #{bool}")
  else
    raise ArgumentError, "Argument must be boolean"
  end
end
Also aliased as: usevc=
use_tcp?() click to toggle source

Get the state of the #use_tcp flag.

# File lib/net/dns/resolver.rb, line 666
def use_tcp?
  @config[:use_tcp]
end
Also aliased as: usevc, use_tcp
usevc()
Alias for: use_tcp?
usevc=(bool)
Alias for: use_tcp=

Private Instance Methods

make_query_packet(string, type, cls) click to toggle source
# File lib/net/dns/resolver.rb, line 1118
def make_query_packet(string, type, cls)
  case string
  when IPAddr
    name = string.reverse
    type = Net::DNS::PTR
    @logger.warn "PTR query required for address #{string}, changing type to PTR"
  when /\d/ # Contains a number, try to see if it's an IP or IPv6 address
    begin
      name = IPAddr.new(string.chomp(".")).reverse
      type = Net::DNS::PTR
    rescue ArgumentError
      name = string if valid? string
    end
  else
    name = string if valid? string
  end

  # Create the packet
  packet = Net::DNS::Packet.new(name, type, cls)

  if packet.query?
    packet.header.recursive = @config[:recursive] ? 1 : 0
  end

  # DNSSEC and TSIG stuff to be inserted here

  packet
end
nameservers_from_name(arg) click to toggle source
# File lib/net/dns/resolver.rb, line 1108
def nameservers_from_name(arg)
  arr = []
  arg.split(" ").each do |name|
    Resolver.new.search(name).each_address do |ip|
      arr << ip
    end
  end
  @config[:nameservers] << arr
end
parse_config_file() click to toggle source

Parses a configuration file specified as the argument.

# File lib/net/dns/resolver.rb, line 1061
def parse_config_file
  if self.class.platform_windows?
    require 'win32/resolv'
    arr = Win32::Resolv.get_resolv_info
    self.domain = arr[0].to_s
    self.nameservers = arr[1]
  else
    nameservers = []
    IO.foreach(@config[:config_file]) do |line|
      line.gsub!(/\s*[;#].*/,"")
      next unless line =~ /\S/
      case line
      when /^\s*domain\s+(\S+)/
        self.domain = $1
      when /^\s*search\s+(.*)/
        self.searchlist = $1.split(" ")
      when /^\s*nameserver\s+(.*)/
        nameservers << $1.split(" ")
      end
    end
    self.nameservers = nameservers.flatten
  end
end
parse_environment_variables() click to toggle source

Parses environment variables.

# File lib/net/dns/resolver.rb, line 1086
def parse_environment_variables
  if ENV['RES_NAMESERVERS']
    self.nameservers = ENV['RES_NAMESERVERS'].split(" ")
  end
  if ENV['RES_SEARCHLIST']
    self.searchlist = ENV['RES_SEARCHLIST'].split(" ")
  end
  if ENV['LOCALDOMAIN']
    self.domain = ENV['LOCALDOMAIN']
  end
  if ENV['RES_OPTIONS']
    ENV['RES_OPTIONS'].split(" ").each do |opt|
      name,val = opt.split(":")
      begin
        eval("self.#{name} = #{val}")
      rescue NoMethodError
        raise ArgumentError, "Invalid ENV option #{name}"
      end
    end
  end
end
query_tcp(packet, packet_data) click to toggle source
# File lib/net/dns/resolver.rb, line 1147
def query_tcp(packet, packet_data)

  ans = nil
  length = [packet_data.size].pack("n")

  @config[:nameservers].each do |ns|
    begin
      buffer = ""
      socket = Socket.new(Socket::AF_INET,Socket::SOCK_STREAM,0)
      socket.bind(Socket.pack_sockaddr_in(@config[:source_port],@config[:source_address].to_s))

      sockaddr = Socket.pack_sockaddr_in(@config[:port],ns.to_s)

      @config[:tcp_timeout].timeout do
        socket.connect(sockaddr)
        @logger.info "Contacting nameserver #{ns} port #{@config[:port]}"
        socket.write(length+packet_data)
        ans = socket.recv(Net::DNS::INT16SZ)
        len = ans.unpack("n")[0]

        @logger.info "Receiving #{len} bytes..."

        if len == 0
          @logger.warn "Receiving 0 lenght packet from nameserver #{ns}, trying next."
          next
        end

        while (buffer.size < len)
          left = len - buffer.size
          temp,from = socket.recvfrom(left)
          buffer += temp
        end

        unless buffer.size == len
          @logger.warn "Malformed packet from nameserver #{ns}, trying next."
          next
        end
      end
      return [buffer,["",@config[:port],ns.to_s,ns.to_s]]
    rescue TimeoutError
      @logger.warn "Nameserver #{ns} not responding within TCP timeout, trying next one"
      next
    ensure
      socket.close
    end
  end
end
query_udp(packet, packet_data) click to toggle source
# File lib/net/dns/resolver.rb, line 1195
def query_udp(packet, packet_data)
  socket4 = UDPSocket.new
  socket4.bind(@config[:source_address].to_s,@config[:source_port])
  socket6 = UDPSocket.new(Socket::AF_INET6)
  socket6.bind(@config[:source_address_inet6].to_s,@config[:source_port])

  ans = nil
  response = ""
  @config[:nameservers].each do |ns|
    begin
      @config[:udp_timeout].timeout do
        @logger.info "Contacting nameserver #{ns} port #{@config[:port]}"
        ans = if ns.ipv6?
          socket6.send(packet_data, 0, ns.to_s, @config[:port])
          socket6.recvfrom(@config[:packet_size])
        else
          socket4.send(packet_data, 0, ns.to_s, @config[:port])
          socket4.recvfrom(@config[:packet_size])
        end
      end
      break if ans
    rescue TimeoutError
      @logger.warn "Nameserver #{ns} not responding within UDP timeout, trying next one"
      next
    end
  end
  ans
end
valid?(name) click to toggle source

FIXME: a ? method should never raise.

# File lib/net/dns/resolver.rb, line 1225
def valid?(name)
  if name =~ /[^-\w\.]/
    raise ArgumentError, "Invalid domain name #{name}"
  else
    true
  end
end