Class: Net::DNS::Resolver

Inherits:
Object
  • Object
show all
Defined in:
lib/Net/DNS/Resolver.rb,
lib/Net/DNS/Resolver/Recurse.rb

Overview

NAME

Net::DNS::Resolver - DNS resolver class

SYNOPSIS

require 'Net\DNS'

res = Net::DNS::Resolver.new

# Perform a lookup, using the searchlist if appropriate.
answer = res.search('example.com')

# Perform a lookup, without the searchlist
answer = res.query('example.com', 'MX')

# Perform a lookup, without pre or post-processing
answer = res.send('example.com', 'MX', 'CH')

# Send a prebuilt packet
answer = res.send(packet)

DESCRIPTION

Instances of the Net::DNS::Resolver class represent resolver objects. A program can have multiple resolver objects, each maintaining its own state information such as the nameservers to be queried, whether recursion is desired, etc.

head1 IPv6 transport

The Net::DNS::Resolver library will use IPv6 transport if the transport is available and the address the server tries to connect to is an IPv6 address.

The print() will method will report if IPv6 transport is available.

You can use the force_v4() method with a non-zero argument to force IPv4 transport.

The nameserver() method has IPv6 dependend behavior. If IPv6 is not available or IPv4 transport has been forced the nameserver() method will only return IPv4 addresses.

For example

res.nameservers=('192.168.1.1', '192.168.2.2', '2001:610:240:0:53:0:0:3')
res.force_v4=(true)
print res.nameservers.join(" "))

Will print: 192.168.1.1 192.168.2.2

ENVIRONMENT

The following environment variables can also be used to configure the resolver:

RES_NAMESERVERS

# Bourne Shell
RES_NAMESERVERS="192.168.1.1 192.168.2.2 192.168.3.3"
export RES_NAMESERVERS

# C Shell
setenv RES_NAMESERVERS "192.168.1.1 192.168.2.2 192.168.3.3"

A space-separated list of nameservers to query.

RES_SEARCHLIST

# Bourne Shell
RES_SEARCHLIST="example.com sub1.example.com sub2.example.com"
export RES_SEARCHLIST

# C Shell
setenv RES_SEARCHLIST "example.com sub1.example.com sub2.example.com"

A space-separated list of domains to put in the search list.

LOCALDOMAIN

# Bourne Shell
LOCALDOMAIN=example.com
export LOCALDOMAIN

# C Shell
setenv LOCALDOMAIN example.com

The default domain.

RES_OPTIONS

# Bourne Shell
RES_OPTIONS="retrans:3 retry:2 debug"
export RES_OPTIONS

# C Shell
setenv RES_OPTIONS "retrans:3 retry:2 debug"

A space-separated list of resolver options to set. Options that take values are specified as option:value.

BUGS

Error reporting and handling needs to be improved.

The current implementation supports TSIG only on outgoing packets. No validation of server replies is performed.

Asynchronous send not implemented.

Non-blocking version?

Windows configuration not implemented

COPYRIGHT

Copyright © 1997-2002 Michael Fuhr.

Portions Copyright © 2002-2004 Chris Reinhardt.

Portions Copyright © 2005 Olaf M. Kolkman, NLnet Labs.

Ruby version Copyright © 2006 AlexD, Nominet UK

All rights reserved. This program is free software; you may redistribute it and/or modify it under the same terms as Perl itself.

SEE ALSO

Net::DNS, Net::DNS::Packet, Net::DNS::Update, Net::DNS::Header, Net::DNS::Question, Net::DNS::RR, RFC 1035, RFC 1034 Section 4.3.5

Direct Known Subclasses

Recurse

Defined Under Namespace

Classes: Recurse

Constant Summary collapse

DEFAULT_ERROR_STRING = 
'unknown error or no error'
RESOLV_CONF = 
'/etc/resolv.conf'
DOTFILE = 
'.resolv.conf'

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(*input_args) ⇒ Resolver

# Use the system defaults

res = Net::DNS::Resolver.new

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

# Set options in the constructor
res = Net::DNS::Resolver.new(
	nameservers => ['10.1.1.128', '10.1.2.128'],
	recurse     => 0,
	debug       => 1)

Returns a resolver object. If given no arguments, new() returns an object configured to your system’s defaults. 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.

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 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. 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



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# File 'lib/Net/DNS/Resolver.rb', line 554

def initialize(*input_args)       
  @sockets=Hash.new
  @sockets['AF_INET']=Hash.new
  @sockets['AF_INET6']= Hash.new
  @sockets['AF_UNSPEC']=Hash.new
  
  set_defaults  
  
  config_path=[]
  config_path.push(ENV['HOME']) if ENV['HOME']
  config_path.push('.')
  
  begin
    read_config_file(RESOLV_CONF) # if -f Resolv_conf && -r _
    
    #	foreach my $dir (@config_path)
    config_path.each do |dir|
      file = "#{dir}/#{DOTFILE}"
      read_config_file(file) # if -f file && -r _ && -o _
    end
  rescue Exception
    # Don't worry if we couldn't find one of these files
  end
  
  read_env
  
  if (input_args.size > 0)
    if (!(input_args[0].instance_of?(Hash)))	
      raise ArgumentError, "Expecting input Hash"
    end
    args=Hash.new
    input_args[0].keys.each do |key|
      args[key] = input_args[0][key]
    end
    if (args[:config_file])
      read_config_file(args[:config_file])
    end
    
    args.keys.each do |attr|
      
      if (attr == :nameservers || attr == :searchlist)
        if (args[attr]==nil ||  !(args[attr].instance_of?(Array)))
          raise ArgumentError, "Net::DNS::Resolver.new(): #{attr} must be an Array\n"			  
        end
      end
      
      if (attr == :nameservers)
        @nameservers=(args[attr])
      else
        begin
          send_method(attr.to_s+"=", args[attr])
        rescue Exception
          print "Argument #{attr} not valid\n" 
        end
      end
    end
  end
end

Instance Attribute Details

#answerfrom ⇒ Object (readonly)

The IP address from which we received the last answer in response to a query.

print 'last answer was from: ', res.answerfrom, "\n"



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# File 'lib/Net/DNS/Resolver.rb', line 192

def answerfrom
  @answerfrom
end

#answersize ⇒ Object (readonly)

Returns the size in bytes of the last answer we received in response to a query.

print 'size of last answer: ', res.answersize, "\n"



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# File 'lib/Net/DNS/Resolver.rb', line 184

def answersize
  @answersize
end

#axfr_rr ⇒ Object (readonly)

Returns the value of attribute axfr_rr.



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# File 'lib/Net/DNS/Resolver.rb', line 201

def axfr_rr
  @axfr_rr
end

#axfr_sel ⇒ Object (readonly)

Returns the value of attribute axfr_sel.



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# File 'lib/Net/DNS/Resolver.rb', line 201

def axfr_sel
  @axfr_sel
end

#axfr_soa_count ⇒ Object (readonly)

Returns the value of attribute axfr_soa_count.



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# File 'lib/Net/DNS/Resolver.rb', line 201

def axfr_soa_count
  @axfr_soa_count
end

#cdflag ⇒ Object (readonly)

The CD bit for a dnssec query. This bit is always zero for non dnssec queries. When the dnssec is enabled the flag can be set to 1.

print "checking disabled flag: ", res.dnssec, "\n"
res.dnssec=(1)
res.cdflag=(1)



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# File 'lib/Net/DNS/Resolver.rb', line 238

def cdflag
  @cdflag
end

#debug ⇒ Object

Get or set the debug flag. If set, calls to search, query, and send will print debugging information on the standard output. The default is false.

print 'debug flag: ', res.debug, "\n"
res.debug=(1)



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# File 'lib/Net/DNS/Resolver.rb', line 392

def debug
  @debug
end

#defnames ⇒ Object

The defnames flag. If this is true, calls to query() will append the default domain to names that contain no dots. The default is true.

print 'defnames flag: ', res.defnames, "\n"
res.defnames=(0)



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# File 'lib/Net/DNS/Resolver.rb', line 348

def defnames
  @defnames
end

#dnsrch ⇒ Object

The dnsrch flag. If this is true, calls to search will apply the search list. The default is true.

print 'dnsrch flag: ', res.dnsrch, "\n"
res.dnsrch=(0)



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# File 'lib/Net/DNS/Resolver.rb', line 382

def dnsrch
  @dnsrch
end

#dnssec ⇒ Object

Enabled DNSSEC this will set the checking disabled flag in the query header and add EDNS0 data as in RFC2671 and RFC3225

When set to true the answer and additional section of queries from secured zones will contain DNSKEY, NSEC and RRSIG records.

Setting calling the dnssec method with a non-zero value will set the UDP packet size to the default value of 2048. If that is to small or to big for your environement you should call the udppacketsize=() method immeditatly after.

res.dnssec=(1)    # turns on DNSSEC and sets udp packetsize to 2048
res.udppacketsize=(1028)   # lowers the UDP pakcet size

The method will Croak::croak with the message “You called the Net::DNS::Resolver::dnssec() method but do not have Net::DNS::SEC installed at …” if you call it without Net::DNS::SEC being in your



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# File 'lib/Net/DNS/Resolver.rb', line 227

def dnssec
  @dnssec
end

#domain ⇒ Object

Returns the value of attribute domain.



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# File 'lib/Net/DNS/Resolver.rb', line 405

def domain
  @domain
end

#errorstring ⇒ Object (readonly)

Returns a string containing the status of the most recent query.

print 'query status: ', res.errorstring, "\n"



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# File 'lib/Net/DNS/Resolver.rb', line 199

def errorstring
  @errorstring
end

#force_v4 ⇒ Object

Set force_v4 to true to use IPv4 only



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# File 'lib/Net/DNS/Resolver.rb', line 403

def force_v4
  @force_v4
end

#ignqrid ⇒ Object

Returns the value of attribute ignqrid.



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# File 'lib/Net/DNS/Resolver.rb', line 405

def ignqrid
  @ignqrid
end

#igntc ⇒ Object

The igntc flag. If true, truncated packets will be ignored. If false, truncated packets will cause the query to be retried using TCP. The default is false.

print 'igntc flag: ', res.igntc, "\n"
res.igntc=(1)



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# File 'lib/Net/DNS/Resolver.rb', line 367

def igntc
  @igntc
end

#nameservers ⇒ Object Also known as: nameserver

The nameservers to be queried.

nameservers = res.nameservers
res.nameservers=('192.168.1.1', '192.168.2.2', '192.168.3.3')



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# File 'lib/Net/DNS/Resolver.rb', line 176

def nameservers
  @nameservers
end

#persistent_tcp ⇒ Object

The persistent TCP setting. If set to true, Net::DNS will keep a TCP socket open for each host:port to which it connects. This is useful if you’re using TCP and need to make a lot of queries or updates to the same nameserver.

This option defaults to false unless you’re running under a SOCKSified Perl, in which case it defaults to true.

print 'Persistent TCP flag: ', res.persistent_tcp, "\n"
res.persistent_tcp=(1)



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# File 'lib/Net/DNS/Resolver.rb', line 299

def persistent_tcp
  @persistent_tcp
end

#persistent_udp ⇒ Object

The persistent UDP setting. If set to true, Net::DNS will keep a single UDP socket open for all queries. This is useful if you’re using UDP and need to make a lot of queries or updates.

print 'Persistent UDP flag: ', res.persistent_udp, "\n"
res.persistent_udp=(1);



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# File 'lib/Net/DNS/Resolver.rb', line 310

def persistent_udp
  @persistent_udp
end

#port ⇒ Object

The port to which we send queries. This can be useful for testing a nameserver running on a non-standard port. The default is port 53.

print 'sending queries to port ', res.port, "\n"
res.port=(9732)



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# File 'lib/Net/DNS/Resolver.rb', line 266

def port
  @port
end

#querytime ⇒ Object (readonly)

Returns the value of attribute querytime.



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# File 'lib/Net/DNS/Resolver.rb', line 201

def querytime
  @querytime
end

#recurse ⇒ Object

The recursion flag. If this is true, nameservers will be requested to perform a recursive query. The default is true.

print 'recursion flag: ', res.recurse, "\n"
res.recurse=(0)



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# File 'lib/Net/DNS/Resolver.rb', line 338

def recurse
  @recurse
end

#retrans ⇒ Object

The retransmission interval. The default is 5.

print 'retrans interval: ', res.retrans, "\n"
res.retrans=(3)



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# File 'lib/Net/DNS/Resolver.rb', line 374

def retrans
  @retrans
end

#retry ⇒ Object

The number of times to try the query. The default is 4.

print 'number of tries: ', res.retry, "\n"
res.retry=(2)



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# File 'lib/Net/DNS/Resolver.rb', line 400

def retry
  @retry
end

#searchlist ⇒ Object

Gets or sets the resolver search list.

searchlist = res.searchlist
res.searchlist=('example.com', 'a.example.com', 'b.example.com')



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# File 'lib/Net/DNS/Resolver.rb', line 256

def searchlist
  @searchlist
end

#set ⇒ Object (readonly)

Returns the value of attribute set.



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# File 'lib/Net/DNS/Resolver.rb', line 201

def set
  @set
end

#sockets ⇒ Object (readonly)

Returns the value of attribute sockets.



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# File 'lib/Net/DNS/Resolver.rb', line 201

def sockets
  @sockets
end

#srcaddr ⇒ Object

The source address from which we send queries. Convenient for forcing queries out a specific interfaces on a multi-homed host. The default is 0.0.0.0, meaning any local address.

print 'sending queries from address ', res.srcaddr, "\n"
res.srcaddr=('192.168.1.1')



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# File 'lib/Net/DNS/Resolver.rb', line 285

def srcaddr
  @srcaddr
end

#srcport ⇒ Object

The port from which we send queries. The default is 0, meaning any port.

print 'sending queries from port ', res.srcport, "\n"
res.srcport=(5353)



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# File 'lib/Net/DNS/Resolver.rb', line 275

def srcport
  @srcport
end

#stayopen ⇒ Object

Returns the value of attribute stayopen.



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# File 'lib/Net/DNS/Resolver.rb', line 405

def stayopen
  @stayopen
end

#tcp_timeout ⇒ Object

The TCP timeout in seconds. A timeout of nil means indefinite. The default is 120 seconds (2 minutes).

print 'TCP timeout: ', res.tcp_timeout, "\n"
res.tcp_timeout=(10)



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# File 'lib/Net/DNS/Resolver.rb', line 319

def tcp_timeout
  @tcp_timeout
end

#tsig_rr ⇒ Object (readonly)

Returns the value of attribute tsig_rr.



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# File 'lib/Net/DNS/Resolver.rb', line 201

def tsig_rr
  @tsig_rr
end

#udp_timeout ⇒ Object

The UDP timeout in seconds. A timeout of nil means the retry and retrans settings will be just utilized to perform the retries until they are exhausted. The default is nil.

print 'UDP timeout: ', res.udp_timeout, "\n"
res.udp_timeout=(10)



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# File 'lib/Net/DNS/Resolver.rb', line 329

def udp_timeout
  @udp_timeout
end

#udppacketsize ⇒ Object (readonly)

udppacketsize will set or get the packet size. If set to a value greater than Net::DNS::PACKETSZ an EDNS extension will be added indicating suppport for MTU path recovery.

Default udppacketsize is Net::DNS::PACKETSZ (512)

print "udppacketsize: ", res.udppacketsize, "\n"
res.udppacketsize=(2048)



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# File 'lib/Net/DNS/Resolver.rb', line 250

def udppacketsize
  @udppacketsize
end

#usevc ⇒ Object

Get or set the usevc flag. If true, then queries will be performed using virtual circuits (TCP) instead of datagrams (UDP). The default is false.

print 'usevc flag: ', res.usevc, "\n"
res.usevc=(1)



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# File 'lib/Net/DNS/Resolver.rb', line 357

def usevc
  @usevc
end

Instance Method Details

#_create_tcp_socket(ns) ⇒ Object 



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# File 'lib/Net/DNS/Resolver.rb', line 2031

def _create_tcp_socket(ns)
  sock=nil
  
  srcport = @srcport
  srcaddr = @srcaddr
  dstport = @port
  
  timeout = @tcp_timeout
  # IO::Socket carps on errors if Perl's -w flag is
  # turned on.  Uncomment the next two lines and the
  # line following the "new" call to turn off these
  # messages.
  
  #my $old_wflag = $^W;
  #$^W = 0;
  
  if (! @force_v4 && IPAddr.new(ns).ipv6? )
    # Perl note : IO::Socket::INET6 fails in a cryptic way upon send()
    # on AIX5L if "0" is passed in as LocalAddr
    # $srcaddr="0" if $srcaddr eq "0.0.0.0";  # Otherwise the INET6 socket will just fail
    
    srcaddr6 = srcaddr == '0.0.0.0' ? '::' : srcaddr
    
    sock=nil
    if (/java/=~RUBY_PLATFORM)
      sock = TCPSocket.new(ns, dstport, srcaddr, srcport)
      #    We need to use Socket.new rather than TCPSocket.new because of 
      #    a bug with TCPSocket#recvfrom in Windows
      #    But this breaks JRuby
    else
      sock = Socket.new( Socket::AF_INET6, Socket::SOCK_STREAM, 0 )
      sockaddr = Socket.pack_sockaddr_in( srcport, srcaddr6 )
      sock.bind( sockaddr )
      sockaddr = Socket.pack_sockaddr_in( dstport, ns )
      sock.connect(sockaddr)
    end
    
    if sock==nil
      @errorstring=('connection failed(IPv6 socket failure)')
      print ";; ERROR: send_tcp: IPv6 connection to #{ns}" + 
 "failed: #{$!}\n" if @debug
      return();
    end
  end
  
  # At this point we have sucessfully obtained an
  # INET6 socket to an IPv6 nameserver, or we are
  # running forced v4, or we do not have v6 at all.
  # Try v4.
  
  if sock==nil
    if (IPAddr.new(ns).ipv6?)
      @errorstring=(
  'connection failed (trying IPv6 nameserver without having IPv6)')
      print 
 ';; ERROR: send_tcp: You are trying to connect to ' +
      ns + " but you do not have IPv6 available\n" if @debug
      return
    end
    
    
    sock=nil
    if (/java/=~RUBY_PLATFORM)
      sock = TCPSocket.new(ns, dstport, srcaddr, srcport)
      #    We need to use Socket.new rather than TCPSocket.new because of 
      #    a bug with TCPSocket#recvfrom in Windows
      #    But this breaks JRuby
    else
      sock = Socket.new( Socket::AF_INET, Socket::SOCK_STREAM, 0 )
      sockaddr = Socket.pack_sockaddr_in( srcport, srcaddr )
      sock.bind( sockaddr )
      sockaddr = Socket.pack_sockaddr_in( dstport, ns )
      sock.connect(sockaddr)
    end
    
    
  end
  
  if sock == nil
    @errorstring=('connection failed')
    print ';; ERROR: send_tcp: connection ' +
		"failed: #{$!}\n" if @debug
    return
  end
  
  return sock
end

#_packetsz ⇒ Object

if (@udppacketsize > Net::DNS::PACKETSZ() then we use EDNS and @udppacketsize should be taken as the maximum packet_data length



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# File 'lib/Net/DNS/Resolver.rb', line 810

def _packetsz
  ret = (@udppacketsize > Net::DNS::PACKETSZ ? @udppacketsize : Net::DNS::PACKETSZ) 
  return ret
end

#_reset_errorstring ⇒ Object 



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# File 'lib/Net/DNS/Resolver.rb', line 815

def _reset_errorstring
  @errorstring = DEFAULT_ERROR_STRING;
end

#axfr(*args) ⇒ Object

zone = res.axfr

zone = res.axfr('example.com')
zone = res.axfr('passwd.example.com', 'HS')

Performs a zone transfer from the first nameserver listed in nameservers. If the zone is omitted, it defaults to the first zone listed in the resolver’s search list. If the class is omitted, it defaults to IN.

Returns a list of Net::DNS::RR objects, or nil if the zone transfer failed.

The redundant SOA record that terminates the zone transfer is not returned to the caller.

See also /axfr_start and /axfr_next.

Here’s an example that uses a timeout:

res.tcp_timeout(10)
zone = res.axfr('example.com')

if (zone)
    zone.each do | rr |
        print rr.inspect
else
    print 'Zone transfer failed: ', res.errorstring, "\n"
end



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# File 'lib/Net/DNS/Resolver.rb', line 1702

def axfr(*args)
  zone=[]
  
  if (axfr_start(args[0], args[1]))
    continueLoop= true
    err = nil
    while (continueLoop)
      rr, err = axfr_next
      continueLoop = rr!=nil && err==nil
      if (continueLoop)
        zone.push(rr)
      end
    end
    zone = [] if err
  end
  
  return zone
end

#axfr_next ⇒ Object

Reads records from a zone transfer one at a time.

Returns nil at the end of the zone transfer. The redundant SOA record that terminates the zone transfer is not returned.

See also axfr

res.axfr_start('example.com')

while (rr = res.axfr_next)
 print rr.inspect
end



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# File 'lib/Net/DNS/Resolver.rb', line 1821

def axfr_next
  err  = ''
  
  # @todo this can't be right!!!
  unless (@axfr_rr!=[])
    unless (@axfr_sock!=nil)
      err = 'no zone transfer in progress'
      
      print ";; #{err}\n" if @debug
      @errorstring=(err)
      
      return nil, err
    end
    
    timeout = @tcp_timeout
    sock = @axfr_sock
    
    #--------------------------------------------------------------
    # Read the length of the response packet.
    #--------------------------------------------------------------
    
    #          ready = sock.wait(timeout)
    ready = IO.select([sock], nil, nil, timeout)
    unless (ready)
      err = 'timeout';
      @errorstring=(err);
      return nil, err
    end
    
    buf, from = read_tcp(sock, Net::DNS::INT16SZ, @debug)
    unless (buf.length > 0)
      err = 'truncated zone transfer'
      @errorstring=(err)
      return nil, err
    end
    
    len = buf.unpack('n')[0]
    unless (len != nil && len > 0)
      err = 'truncated zone transfer'
      @errorstring=(err)
      return nil, err
    end
    
    #--------------------------------------------------------------
    # Read the response packet.
    #--------------------------------------------------------------
    
    ready = IO.select([sock], nil, nil, timeout)
    #          ready = sel.wait(timeout) # should be sock.wait, anyway!
    unless (ready)
      err = 'timeout'
      @errorstring=(err)
      return nil, err
    end
    
    buf, from = read_tcp(sock, len, @debug)
    
    print ';; received ' + buf.length.to_s +  " bytes\n" if @debug
    
    unless (buf.length == len)
      err = "expected #{len} bytes, received " + buf.length.to_s
      @errorstring=(err)
      print ";; #{err}\n" if @debug
      return nil, err
    end
    
    ans, err = Net::DNS::Packet.new_from_binary(buf, @debug)
    
    if (ans)
      if (ans.header.rcode != 'NOERROR') 
        @errorstring=('Response code from server: ' + ans.header.rcode)
        print ';; Response code from server: ' + ans.header.rcode + "\n" if @debug
        return nil, err
      end
      if (ans.header.ancount < 1)
        err = 'truncated zone transfer'
        @errorstring=(err)
        print ";; #{err}\n" if @debug
        return nil, err
      end
    else
      err ||= 'unknown error during packet parsing'
      @errorstring=(err)
      print ";; #{err}\n" if @debug
      #			return wantarray ? (undef, $err) : undef;
      return nil, err
    end
    
    ans.answer.each do |rr|
      if (rr.type == 'SOA')
        @axfr_soa_count +=1
        if (@axfr_soa_count < 2)
          @axfr_rr.push(rr)
        end
      else
        @axfr_rr.push(rr)
      end
    end
    
    if (@axfr_soa_count >= 2)
      @axfr_sel = nil
      # we need to mark the transfer as over if the responce was in 
      # many answers.  Otherwise, the user will call axfr_next again
      # and that will cause a 'no transfer in progress' error.
      @axfr_rr.push(nil)
    end
  end
  
  rr = @axfr_rr.shift
  
  return rr # , nil)
end

#axfr_old ⇒ Object

Raises:

  • (NotImplementedError) 


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# File 'lib/Net/DNS/Resolver.rb', line 1721

def axfr_old
  raise NotImplementedError, "Use of Net::DNS::Resolver::axfr_old() is deprecated, use axfr() or axfr_start()."
end

#axfr_start(*args) ⇒ Object

res.axfr_start

res.axfr_start('example.com')
res.axfr_start('example.com', 'HS')

Starts a zone transfer from the first nameserver listed in nameservers. If the zone is omitted, it defaults to the first zone listed in the resolver’s search list. If the class is omitted, it defaults to IN.

Use axfr_next to read the zone records one at a time.



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# File 'lib/Net/DNS/Resolver.rb', line 1736

def axfr_start(*args)
  dname = args[0]
  klass = args[1]
  dname ||= @searchlist[0]
  klass ||= 'IN'
  timeout = @tcp_timeout
  
  unless (dname)
    print ";; ERROR: axfr: no zone specified\n" if @debug
    @errorstring=('no zone')
    return
  end
  
  
  print ";; axfr_start(#{dname}, #{klass})\n" if @debug
  
  unless (@nameservers.length > 0)
    @errorstring=('no nameservers')
    print ";; ERROR: no nameservers\n" if @debug
    return
  end
  
  packet = make_query_packet([dname, 'AXFR', klass])
  packet_data = packet.data
  
  ns = @nameservers[0]
  
  
  srcport = @srcport
  srcaddr = @srcaddr
  dstport = @port
  
  print ";; axfr_start nameserver = #{ns}\n" if @debug
  print ";; axfr_start srcport: #{srcport}, srcaddr: #{srcaddr}, dstport: #{dstport}\n" if @debug
  
  
  sock=""
  sock_key = "#{ns}:#{@port}"
  
  
  if (@persistent_tcp && @axfr_sockets['AF_UNSPEC'][sock_key]!=nil)
    sock = @axfr_sockets['AF_UNSPEC'][sock_key]
    print ";; using persistent socket\n" if @debug
  else
    sock=_create_tcp_socket(ns)
    
    return unless (sock!=nil);  # all error messages 
    # are set by _create_tcp_socket
    
    
    @axfr_sockets['AF_UNSPEC'][sock_key] = sock if  @persistent_tcp
  end
  
  lenmsg = [packet_data.length].pack('n')
  
  unless (sock.send(lenmsg,0))
    @errorstring=($!)
    return
  end
  
  unless (sock.send(packet_data,0))
    @errorstring=($!)
    return
  end
  
  @axfr_sock       = sock
  @axfr_rr        = []
  @axfr_soa_count = 0
  
  return sock
end

#bgisready(socket) ⇒ Object

Determines whether a socket is ready for reading. The argument is an IO::Socket object returned by res.bgsend.

Returns true if the socket is ready, false if not.

socket = res.bgsend('foo.example.com')
until (res.bgisready(socket))
    # do some other processing
end
packet = res.bgread(socket)
socket = nil



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# File 'lib/Net/DNS/Resolver.rb', line 1605

def bgisready(socket)
  ready = IO.select([socket], nil, nil, 0)
  return ready!=nil
  #        return socket.ready? > 0
end

#bgread(sock) ⇒ Object

Reads the answer from a background query (see bgsend). The argument is an IO::Socket object returned by bgsend.

Returns a Net::DNS::Packet object or nil on error.

The programmer should close or destroy the socket object after reading it.

packet = res.bgread(socket)
socket = nil



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# File 'lib/Net/DNS/Resolver.rb', line 1564

def bgread(sock)
  buf = '';
  
  begin
    
    buf, from = sock.recvfrom(_packetsz)
    
    if (from)
      print ';; answer from ', from[2], ':',
      from[1], ' : ', buf.length, " bytes\n" if @debug
      
      ans, err = Net::DNS::Packet.new_from_binary(buf, @debug)
      
      if (defined?ans)
        @errorstring=(ans.header.rcode)
      elsif (defined?err)
        @errorstring=(err)
      end
      
      return ans
    end
  rescue SocketError => e
    @errorstring=e.message
    return;
  end
end

#bgsend(*args) ⇒ Object

Performs a background DNS query for the given name, i.e., sends a query packet to the first nameserver listed in res.nameservers and returns immediately without waiting for a response. The program can then perform other tasks while waiting for a response from the nameserver.

The argument list can be either a Net::DNS::Packet object or a list of strings. The record type and class can be omitted; they default to A and IN. If the name looks like an IP address (4 dot-separated numbers), then an appropriate PTR query will be performed.

Returns an IO::Socket::INET object or nil on error in which case the reason for failure can be found through a call to the errorstring method.

The program must determine when the socket is ready for reading and call res.bgread to get the response packet. You can use res.bgisready or IO::Select to find out if the socket is ready before reading it.

socket = res.bgsend(packet_object) || die " #{res.errorstring}"

socket = res.bgsend('mailhost.example.com')
socket = res.bgsend('example.com', 'MX')
socket = res.bgsend('user.passwd.example.com', 'TXT', 'HS')



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# File 'lib/Net/DNS/Resolver.rb', line 1467

def bgsend(*args)
  if (@nameservers == nil || @nameservers.length == 0)
    @errorstring=('no nameservers')
    return
  end
  
  _reset_errorstring;
  
  packet = make_query_packet(args);
  packet_data = packet.data;
  
  srcaddr = @srcaddr
  srcport = @srcport
  
  res = []
  dst_sockaddr=""
  ns_address = (@nameservers)[0]
  dstport = @port
  sockfamily=""
  
  # The logic below determines ther $dst_sockaddr.
  # If getaddrinfo is available that is used for both INET4 and INET6
  # If getaddrinfo is not avialable (Socket6 failed to load) we revert
  # to the 'classic mechanism
  
  socktype_tmp=""
  proto_tmp=""
  canonname_tmp=""
  
  begin
    # The AI_NUMERICHOST surpresses lookups.
    res = Socket::getaddrinfo(ns_address, dstport)[0] # , Socket::AF_UNSPEC, 
    # Socket::SOCK_DGRAM, 0 , Socket::AI_NUMERICHOST)[0]
    
    sockfamily = res[0]
    socktype_tmp = res[1]
    proto_tmp = res[2]
    dst_sockaddr = res[3]
    canonname_tmp = res[4]
    
    #          if (res.length < 5)
  rescue SocketError
    raise RuntimeError, "can't resolve \"#{ns_address}\" to address (it could have been an IP address)"
  end
  sock=nil
  
  if (sockfamily == 'AF_INET')
    sock = UDPSocket.new()
    sock.bind(srcaddr, srcport)
    #          socket[sockfamily] = IO::Socket::INET.new({
    #            Proto => 'udp',
    #            Type => Socket::SOCK_DGRAM,
    #            LocalAddr => srcaddr,
    #            LocalPort => (srcport || nil),
    #          })
    #        elsif (sockfamily == AF_INET6 )
    #          # Otherwise the INET6 socket will just fail
    #          srcaddr6 = srcaddr == "0.0.0.0" ? '::' : srcaddr
    #          socket[sockfamily] = IO::Socket::INET6.new({
    #            Proto => 'udp',
    #            Type => SOCK_DGRAM,
    #            LocalAddr => srcaddr6,
    #            LocalPort => (srcport || nil),
    #          })
  else
    raise RuntimeError, " bgsend:Unsupported Socket Family: #{sockfamily}"
  end
  
  unless (sock != nil)
    @errorstring=("could not get socket")
    return;
  end
  
  print ";; bgsend(#{ns_address} : #{dstport})\n" if @debug
  
  unless (sock.send(packet_data,0,dst_sockaddr, dstport))
    err = $!
    print ";; send ERROR(#{ns_address}): #{err}\n" if @debug
    
    @errorstring=("Send: " + err)
    return
  end
  return sock
  
end

#cname_addr(names, packet) ⇒ Object 



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# File 'lib/Net/DNS/Resolver.rb', line 788

def cname_addr(names, packet)
  addr=[]
  
  oct2 = '(?:2[0-4]\d|25[0-5]|[0-1]?\d\d|\d)';
  
  packet.answer.each do |rr|
    if (names.index(rr.name) != nil)
      if (rr.type == 'CNAME')
        names.push(rr.cname)
      elsif (rr.type == 'A')
        if (rr.address =~ /^(#{oct2}\.#{oct2}\.#{oct2}\.#{oct2})$/o)
          addr.push($1)
        end
      end
    end
  end            
  return addr;
end

#inspect ⇒ Object

Returns a string representation of the resolver state.



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# File 'lib/Net/DNS/Resolver.rb', line 683

def inspect
  timeout = defined?@tcp_timeout ? @tcp_timeout : 'indefinite';
  hasINET6line= " (IPv6 Transport is available)"
  ignqrid=@ignqrid ? "\n;; ACCEPTING ALL PACKETS (IGNQRID)" : "";
  return ";\
;; RESOLVER state:\
;;  domain       = #{@domain}\
;;  searchlist   = #{@searchlist}}\
;;  nameservers  = #{@nameservers}\
;;  port         = #{@port}\
;;  srcport      = #{@srcport}\
;;  srcaddr      = #{@srcaddr}\
;;  tcp_timeout  = #{timeout}\
;;  retrans  = #{@retrans}  retry    = #{@retry}\
;;  usevc    = #{@usevc}  stayopen = #{@stayopen}    igntc = #{@igntc}\
;;  defnames = #{@defnames}  dnsrch   = #{dnsrch}\
;;  recurse  = #{@recurse}  debug    = #{debug}\
;;  force_v4 = #{@force_v4} #{hasINET6line} #{ignqrid}
"
end

#make_query_packet(args) ⇒ Object 



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# File 'lib/Net/DNS/Resolver.rb', line 1611

def make_query_packet(args)
  packet=""
  
  if (args[0]!=nil and args[0].class == Net::DNS::Packet)
    packet = args[0]
  else
    name, type, klass = args
    
    name  ||= ''
    type  ||= 'A'
    klass ||= 'IN'
    
    # If the name looks like an IP address then do an appropriate
    # PTR query.
    if (name =~ /^(\d+)\.(\d+)\.(\d+)\.(\d+)$/o)
      name = "#{$4}.#{$3}.#{$2}.#{$1}.in-addr.arpa."
      type = 'PTR'
    end
    
    packet = Net::DNS::Packet.new_from_values(name, type, klass)
  end
  
  if (packet.header.opcode == 'QUERY')
    packet.header.rd=(@recurse ? 1 : 0)
  end
  
  if (@dnssec)
    # RFC 3225
    print ";; Adding EDNS extention with UDP packetsize #{@udppacketsize} and DNS OK bit set\n"  if @debug
    
    optrr = Net::DNS::RR.create({
      :type         => 'OPT',
      :name         => '',
      :rrclass        => @udppacketsize,  # Decimal UDPpayload
      :ednsflags    => 0x8000, # first bit set see RFC 3225 
    })
    
    packet.push('additional', optrr)
    
  elsif (@udppacketsize > Net::DNS::PACKETSZ)
    print ";; Adding EDNS extention with UDP packetsize  #{@udppacketsize}.\n" if @debug
    # RFC 3225
    optrr = Net::DNS::RR.create( {
      :type         => 'OPT',
      :name         => '',
      :rrclass        => @udppacketsize,  # Decimal UDPpayload
      :ttl          => 0x0000 # RCODE 32bit Hex
    })
    
    packet.push('additional', optrr)
  end
  
  
  if (@tsig_rr != nil && @tsig_rr.length > 0)
    #          if (!grep { $_.type == 'TSIG' } packet.additional)
    if (packet.additional.select { |i| i.type == 'TSIG' }.length > 0)
      packet.push('additional', @tsig_rr)
    end
  end
  
  return packet
end

#query(*args) ⇒ Object

Performs a DNS query for the given name; the search list is not applied. If the name doesn’t contain any dots and defnames 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.

Returns a Net::DNS::Packet object, or nil if no answers were found. If you need to examine the response packet whether it contains any answers or not, use the send() method instead.

packet = res.query('mailhost')
packet = res.query('mailhost.example.com')
packet = res.query('192.168.1.1')
packet = res.query('example.com', 'MX')
packet = res.query('user.passwd.example.com', 'TXT', 'HS')



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# File 'lib/Net/DNS/Resolver.rb', line 913

def query(*args)
  name = args[0]
  type  = 'A';
  klass = 'IN';
  if (args.length > 1) 
    type = args[1]
    if (args.length > 2)
      klass = args[2]
    end
  end
  
  # If the name doesn't contain any dots then append the default domain.
  if ((name.index('.')==nil) && (name.index(':')==nil) && @defnames!=nil)
    name += ".#{@domain}";
  end
  
  # If the name looks like an IP address then do an appropriate
  # PTR query.
  if (name =~ /^(\d+)\.(\d+)\.(\d+)\.(\d+)$/)
    name = "#{$4}.#{$3}.#{$2}.#{$1}.in-addr.arpa";
    type = 'PTR';
  end
  
  # IPv4 address in IPv6 format (very lax regex)
  if (name =~ /^[0:]*:ffff:(\d+)\.(\d+)\.(\d+)\.(\d+)$/i)
    name = "#{$4}.#{$3}.#{$2}.#{$1}.in-addr.arpa";
    type = 'PTR';
  end
  
  # if the name looks like an IPv6 0-compressed IP address then expand
  # PTR query. (eg 2001:5c0:0:1::2)
  if (name =~ /::/)
    # avoid stupid "Use of implicit split to @_ is deprecated" warning
    while ((parts = name.split(/:/)).length < 8) do
      name.sub!(/::/, ":0::")
    end
    name.sub!(/::/, ":0:")
  end
  
  # if the name looks like an IPv6 address then do appropriate
  # PTR query. (eg 2001:5c0:0:1:0:0:0:2)
  if (name =~ /:/)
    stuff = name.split(/:/)
    if (stuff.length == 8)
      name = 'ip6.arpa.'
      type = 'PTR'
      stuff.each do |segment|
        segment = sprintf("%04s", segment)
        segment.gsub!(/ /, "0")
        segment =~ /(.)(.)(.)(.)/
        name = "#{$4}.#{$3}.#{$2}.#{$1}.#{name}"
      end
    else
      # no idea what this is
    end
  end
  
  print ";; query(#{name}, #{type}, #{klass})\n" if @debug;
  packet = Net::DNS::Packet.new_from_values(name, type, klass);
  
  ans = send(packet);
  
  #        return (ans && ans.header.ancount)   ? ans : nil;
  return ans
end

#read_config_file(conf_file) ⇒ Object 



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# File 'lib/Net/DNS/Resolver.rb', line 647

def read_config_file(conf_file)
  ns=[]
  searchlist=[]
  if !(File.exist? conf_file)
    if (/java/ =~ RUBY_PLATFORM && !(conf_file=~/:/))
      # Problem with paths and Windows on JRuby - see if we can munge the drive...
      wd = Dir.getwd
      drive = wd.split(':')[0]
      if (drive.length==1)
        conf_file = drive << ":" << conf_file
      end
    end
  end
  IO.foreach(conf_file) do |line|
    line.gsub!(/\s*[;#].*/,"")
    next unless line =~ /\S/
    case line
    when /^\s*domain\s+(\S+)/
      @domain = $1
    when /^\s*search\s+(.*)/
      @searchlist = $1.split(" ")
    when /^\s*nameserver\s+(.*)/
      @nameservers = []
      #              if @nameservers.length == 1 && @nameservers[0]=='127.0.0.1'
      #                @nameservers=[]
      #              end
      $1.split(" ").each do |ns|
        ns = "0.0.0.0" if ns == "0"
        next if ns =~ /:/ # skip IPv6 addresses
        @nameservers.push(ns)
      end
    end
  end
end

#read_env ⇒ Object 



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# File 'lib/Net/DNS/Resolver.rb', line 613

def read_env
  if ENV['RES_NAMESERVERS']
    @nameservers = ENV['RES_NAMESERVERS'].split(" ")
  end
  
  if ENV['RES_SEARCHLIST']
    @searchlist = ENV['RES_SEARCHLIST'].split(" ")
  end
  
  if ENV['LOCALDOMAIN']
    @domain = ENV['LOCALDOMAIN']
  end
  
  if ENV['RES_OPTIONS']
    ENV['RES_OPTIONS'].split(" ").each do |opt|
      name,val = opt.split(":")
      if (val != nil && val.length == 1)
        if val[0]>=48 && val[0]<=57
          val = val[0]-48
        end
      end
      val = 1 if val == nil
      #            if (name == "retry")
      #              name = "retrytime"
      #            end
      begin
        send_method(name+"=", val)
      rescue Exception
        print "Argument #{name} not valid\n"
      end
    end
  end
end

#read_tcp(sock, nbytes, debug = false) ⇒ Object

Usage: data, from = read_tcp(socket, nbytes, debug)



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# File 'lib/Net/DNS/Resolver.rb', line 1994

def read_tcp(sock, nbytes, debug=false)
  buf = ''
  from=nil
  
  while (buf.length < nbytes)
    nread = nbytes - buf.length;
    read_buf = ''
    
    print ";; read_tcp: expecting #{nread} bytes\n" if debug
    
    # During some of my tests recv() returned undef even
    # though there wasn't an error.  Checking for the amount
    # of data read appears to work around that problem.
    
    read_buf, from = sock.recvfrom(nread)
    if (read_buf.length < 1)
      errstr = $!
      
      print ";; ERROR: read_tcp: recv failed: #{$!}\n" if debug
      
      if (errstr == 'Resource temporarily unavailable')
        warn "ERROR: read_tcp: recv failed: #{errstr}\n";
        warn "ERROR: try setting res.timeout()\n";
      end
      
      break
    end
    
    print ';; read_tcp: received ', read_buf.length.inspect, " bytes\n" if debug
    
    break unless read_buf.length > 0
    buf += read_buf
  end
  
  return buf, from
end

#search(*args) ⇒ Object

Performs a DNS query for the given name, applying the searchlist if appropriate. The search algorithm is as follows:

  • If the name contains at least one dot, try it as is.

  • If the name doesn’t end in a dot then append each item in

the search list to the name.  This is only done if dnsrch
is true.

  • If the name doesn’t contain any dots, try it as is.

The record type and class can be omitted; they default to A and IN. If the name looks like an IP address (4 dot-separated numbers), then an appropriate PTR query will be performed.

Returns a Net::DNS::Packet object, or nil if no answers were found. If you need to examine the response packet whether it contains any answers or not, use the send() method instead.

packet = res.search('mailhost')
packet = res.search('mailhost.example.com')
packet = res.search('192.168.1.1')
packet = res.search('example.com', 'MX')
packet = res.search('user.passwd.example.com', 'TXT', 'HS')



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# File 'lib/Net/DNS/Resolver.rb', line 843

def search(*args)
  name = args[0]
  type = 'A'
  klass = "IN"
  if args.length >1
    type = args[1]
    if args.length > 2
      klass = args[2]
    end
  end
  ans=""
  
  # If the name looks like an IP address then do an appropriate
  # PTR query.
  if (name =~ /^(\d+)\.(\d+)\.(\d+)\.(\d+)$/)
    name = "#{$4}.#{$3}.#{$2}.#{$1}.in-addr.arpa.";
    type = 'PTR';
  end
  
  # pass IPv6 addresses right to query()
  if (name.index(':')!=nil and name.index('.')==nil)
    return query(name);
  end
  
  # If the name contains at least one dot then try it as is first.
  if (name.index('.') != nil)
    print ";; search(#{name}, #{type}, #{klass})\n" if @debug
    ans = query(name, type, klass)
    return ans if ans!=nil and ans.header.ancount > 0
  end
  
  # If the name doesn't end in a dot then apply the search list.
  if ((name !~ /\.$/) && @dnsrch)
    #		foreach my $domain (@{$self->{'searchlist'}}) {
    @searchlist.each do |domain|
      newname = "#{name}.#{domain}"
      print ";; search(#{newname}, #{type}, #{klass})\n" if @debug
      ans = query(newname, type, klass)
      return ans if ans!=nil and ans.header.ancount > 0
    end
  end
  
  # Finally, if the name has no dots then try it as is.
  if (name.index('.')==nil)
    print ";; search(#{name}, #{type}, #{klass})\n" if @debug
    ans = query("#{name}.", type, klass)
    return ans if ans!=nil and ans.header.ancount > 0
  end
  
  # No answer was found.
  return nil;
end

#send(*args) ⇒ Object

Performs a DNS query for the given name. Neither the searchlist nor the default domain will be appended.

The argument list can be either a Net::DNS::Packet object or a list of strings. 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.

Returns a Net::DNS::Packet object whether there were any answers or not. Use packet.header.ancount or packet.answer to find out if there were any records in the answer section. Returns nil if there was an error.

packet = res.send(packet_object)
packet = res.send('mailhost.example.com')
packet = res.send('example.com', 'MX')
packet = res.send('user.passwd.example.com', 'TXT', 'HS')



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# File 'lib/Net/DNS/Resolver.rb', line 996

def send(*args)
  packet = make_query_packet(args);
  packet_data = packet.data;
  
  
  ans = ""
  
  if (@usevc || packet_data.length > _packetsz)
    
    ans = send_tcp(packet, packet_data);
    
  else
    ans = send_udp(packet, packet_data);
    if (ans!=nil && !(!ans.header.tc || ans.header.tc == 0) && !@igntc)
      print ";;\n;; packet truncated: retrying using TCP\n" if @debug;
      ans = send_tcp(packet, packet_data);
    end
  end
  
  return ans;
end

#send_method ⇒ Object 



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# File 'lib/Net/DNS/Resolver.rb', line 411

alias_method :send_method,  :send

#send_tcp(packet, packet_data) ⇒ Object 



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# File 'lib/Net/DNS/Resolver.rb', line 1018

def send_tcp(packet, packet_data)
  lastanswer=""
  
  srcport = @srcport
  srcaddr = @srcaddr
  dstport = @port
  
  if ( @nameservers==nil)
    @errorstring=('no nameservers')
    print ";; ERROR: send_tcp: no nameservers\n" if @debug
    return;
  end
  
  _reset_errorstring
  
  
  #      NAMESERVER: foreach my $ns ($self->nameservers()) {
  @nameservers.each do |ns|	      
    print ";; attempt to send_tcp(#{ns}:#{dstport}) (src port = #{srcport})\n" if @debug
    
    sock=""
    sock_key = "#{ns}:#{dstport}";
    host,port=""
    if (@persistent_tcp && @sockets['AF_UNSPEC'][sock_key])
      sock = @sockets['AF_UNSPEC'][sock_key];
      print ";; using persistent socket\n" if @debug
    else
      sock= _create_tcp_socket(ns)
      next unless sock!=nil
      
      @sockets['AF_UNSPEC'][sock_key] = sock if @persistent_tcp
    end
    
    
    lenmsg = [packet_data.length].pack('n')
    print ';; sending ' + packet_data.length.to_s + " bytes\n" if @debug
    
    # note that we send the length and packet data in a single call
    # as this produces a single TCP packet rather than two. This
    # is more efficient and also makes things much nicer for sniffers.
    # (ethereal doesn't seem to reassemble DNS over TCP correctly)
    
    
    if (!sock.send( lenmsg + packet_data,0))
      @errorstring=($!)
      print ";; ERROR: send_tcp: data send failed: #{@errorstring}\n" if @debug
      next
    end
    
    begin
      Timeout::timeout(@tcp_timeout) {
        buf, from = read_tcp(sock, Net::DNS::INT16SZ, @debug)
        
        next unless buf.length # Failure to get anything
        len = buf.unpack('n')[0]
        next unless len         # Cannot determine size
        
        buf, from = read_tcp(sock, len, @debug)
        
        @answerfrom=(from[2])
        @answersize=(buf.length)
        
        print ';; received ' + buf.length.to_s + " bytes\n" if @debug
        
        unless (buf.length == len)
          @errorstring=("expected #{len} bytes, received " + buf.length)
          next
        end
        
        ans, err = Net::DNS::Packet.new_from_binary(buf, @debug)
        if (ans!=nil)
          @errorstring=(ans.header.rcode)
          ans.answerfrom=(@answerfrom)
          ans.answersize=(@answersize)
          
          if (ans.header.rcode != "NOERROR" && ans.header.rcode != "NXDOMAIN")
            # Remove this one from the stack
            print "RCODE: " + ans.header.rcode + "; trying next nameserver\n" if @debug
            lastanswer=ans
            next
          end
        elsif (err!=nil)
          @errorstring=(err)
        end
        return ans
      }
    rescue Timeout::Error => e
      @errorstring=('Timeout: #{e.message}')
      next
    ensure
      if (!@persistent_tcp)
        sock.close()
      end
    end
  end
  
  #          sel = IO::Select.new(sock)
  #          timeout=@tcp_timeout
  #          if (sel.can_read(timeout))
  #            buf = read_tcp(sock, Net::DNS::INT16SZ, @debug)
  #            next unless buf.length # Failure to get anything
  #            len = buf.unpack('n')[0]
  #            next unless len         # Cannot determine size
  #            
  #            unless (sel.can_read(timeout))
  #              @errorstring=('timeout')
  #              print ";; TIMEOUT\n" if @debug
  #              next
  #            end
  #            
  #            buf = read_tcp(sock, len, @debug)
  #            
  #            answerfrom(sock.peerhost)
  #            answersize(buf.length)
  #            
  #            print ';; received ' + buf.length + " bytes\n" if @debug
  #            
  #            unless (buf.length == len)
  #              @errorstring=("expected #{len} bytes, received " + buf.length)
  #              next
  #            end
  #            
  #            ans, err = Net::DNS::Packet.new_from_data(buf, @debug)
  #            if (ans!=nil)
  #              @errorstring=(ans.header.rcode)
  #              ans.answerfrom=(@answerfrom)
  #              ans.answersize=(@answersize)
  #              
  #              if (ans.header.rcode != "NOERROR" && ans.header.rcode != "NXDOMAIN")
  #                # Remove this one from the stack
  #                print "RCODE: " + ans.header.rcode + "; trying next nameserver\n" if @debug
  #                lastanswer=ans
  #                next
  #              end
  #            elsif (err!=nil)
  #              @errorstring=(err)
  #            end
  #            return ans
  #          else
  #            @errorstring=('timeout')
  #            next
  #          end
  #        end
  
  if (lastanswer!="")
    @errorstring=(lastanswer.header.rcode)
    return lastanswer
  end
  
  return
end

#send_udp(packet, packet_data) ⇒ Object 



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# File 'lib/Net/DNS/Resolver.rb', line 1170

def send_udp(packet, packet_data)
  retrans = @retrans
  timeout = retrans
  
  lastanswer=""
  
  stop_time = Time.now + @udp_timeout if (@udp_timeout && @udp_timeout > 0)
  
  _reset_errorstring;
  
  ns=[]
  dstport = @port
  srcport = @srcport
  srcaddr = @srcaddr
  
  sock=Hash.new
  
  if (@persistent_udp)
    if ( (@sockets['AF_INET6']['UDP'])!=nil)
      sock[AF_INET6] = @sockets['AF_INET6']['UDP']
      print ";; using persistent AF_INET6 family type socket\n" if @debug
    end
    if ( (@sockets['AF_INET']['UDP'])!=nil)
      sock['AF_INET'] = @sockets['AF_INET']['UDP'];
      print ";; using persistent AF_INET() family type socket\n" if @debug
    end
  end
  
  if (! @force_v4 && @sockets['AF_INET6']==nil )
    
    
    # '::' Otherwise the INET6 socket will fail.
    
    srcaddr6 = srcaddr == '0.0.0.0' ? '::' : srcaddr
    
    print ";; Trying to set up a AF_INET6 family type UDP socket with srcaddr: #{srcaddr} ... " if @debug
    
    
    # IO::Socket carps on errors if Perl's -w flag is turned on.
    # Uncomment the next two lines and the line following the "new"
    # call to turn off these messages.
    
    #my $old_wflag = $^W;
    #$^W = 0;
    
    sock['AF_INET6'] = UDPSocket.new
    sock['AF_INET6'].bind(srcaddr6, srcport)
    print(sock['AF_INET6']!=nil ? "done\n":"failed\n") if @debug
  end
  
  # Always set up an AF_INET socket. 
  # It will be used if the address familly of for the endpoint is V4.
  
  if (sock['AF_INET']==nil)
    print ";; setting up an AF_INET() family type UDP socket\n" if @debug
    
    sock['AF_INET'] = UDPSocket.new()
    sock['AF_INET'].bind(srcaddr, srcport)
  end
  
  
  
  unless (sock['AF_INET']!=nil || sock['AF_INET6']!=nil)
    
    @errorstring=("could not get socket")
    return;
  end
  
  @sockets['AF_INET']['UDP'] = sock['AF_INET'] if (@persistent_udp) && sock != nil
  @sockets['AF_INET6']['UDP'] = sock['AF_INET6'] if persistent_udp && (sock['AF_INET6']!=nil) && ! @force_v4
  
  # Constructing an array of arrays that contain 3 elements: The
  # nameserver IP address, its sockaddr and the sockfamily for
  # which the sockaddr structure is constructed.
  
  nmbrnsfailed=0;
  #        #        NSADDRESS: foreach my $ns_address ($self->nameservers()){
  #        #      NSADDRESS: @nameservers.each do |ns_address|
  @nameservers.each do |ns_address|
    # The logic below determines the $dst_sockaddr.
    # If getaddrinfo is available that is used for both INET4 and INET6
    # If getaddrinfo is not avialable (Socket6 failed to load) we revert
    # to the 'classic mechanism
    
    # we can use getaddrinfo
    #              no strict 'subs';   # Because of the eval statement in the BEGIN
    # AI_NUMERICHOST is not available at compile time.
    # The AI_NUMERICHOST surpresses lookups.
    
    if (IPAddr.new(ns_address).ipv6? && @force_v4)
      next
    end
    begin
      res = Socket::getaddrinfo(ns_address, dstport)[0] # , Socket::AF_UNSPEC, Socket::SOCK_DGRAM, 
      # 0, Socket::AI_NUMERICHOST)[0]
      
      
      sockfamily = res[0]
      socktype_tmp = res[1]
      proto_tmp = res[2]
      dst_sockaddr = res[3]
      canonname_tmp = res[4]
      
    rescue SocketError
      #            if (res.length < 5)
      raise RuntimeError, ('can\'t resolve ' + ns_address + ' to address')
    end
    
    ns.push([ns_address,dst_sockaddr,sockfamily])
  end   
  
  if (nameservers.length == 0)
    print "No nameservers" if @debug;
    @errorstring=('no nameservers');
    return;
  end
  
  
  select = []
  # We allready tested that one of the two socket exists
  
  select.push(sock['AF_INET']) if (sock['AF_INET'] != nil)
  select.push(sock['AF_INET6']) if ((sock['AF_INET6'] != nil) && !@force_v4)
  
  
  # Perform each round of retries.
  #      for (i = 0
  #           i < @retry;
  #        ++i, retrans *= 2, timeout = int(retrans / (ns.length || 1)))
  @retry.times do |i|
    
    if (i>0)         
      retrans *= 2
    end
    i += 1
    timeout = (retrans / (ns.length || 1)).to_int
    
    timeout = 1 if (timeout < 1)
    
    # Try each nameserver.
    #                  NAMESERVER: foreach my $ns (@ns) {
    #          NAMESERVER: ns.each do |nstemp|
    ns.each do |nstemp|
      next if nstemp[3]!=nil
      if (stop_time)
        now = Time.now
        if (stop_time < now)
          @errorstring=('query timed out')
          return;
        end
        if (timeout > 1 && timeout > (stop_time-now))
          timeout = stop_time-now;
        end
      end
      nsname = nstemp[0]
      nsaddr = nstemp[1]
      nssockfamily = nstemp[2]
      
      # If we do not have a socket for the transport
      # we are supposed to reach the namserver on we
      # should skip it.
      unless ((sock[ nssockfamily ])!=nil)
        print "Send error: cannot reach #{nsname} (" +                
         ( (nssockfamily == 'AF_INET6') ? "IPv6" : "" ) +
         ( (nssockfamily == 'AF_INET') ? "IPv4" : "" ) +
  				") not available" if @debug
        
        
        @errorstring=("Send error: cannot reach #{nsname} (" +
         ( (nssockfamily == 'AF_INET6') ? "IPv6" : "" ) +
         ( (nssockfamily == 'AF_INET') ? "IPv4" : "" ) +
  					       ") not available")
        next
      end
      
      print ";; send_udp(#{nsname}:#{dstport})\n" if @debug
      
      unless (sock[nssockfamily].send(packet_data, 0, nsaddr, @port))
        print ";; send error: #{$!}\n" if @debug
        @errorstring=("Send error: #{$!}")
        nmbrnsfailed+=1
        nstemp[3]="Send error" + @errorstring
        next
      end
      
      # See ticket 11931 but this works not quite yet
      oldpacket_timeout=Time.now+timeout
      while ( oldpacket_timeout > Time.now)
        #                      ready = sel.can_read(timeout)
        ready = IO.select(select, nil, nil, timeout)
        if (ready != nil)
          ready = ready[0]
          ready.each do |readytemp|
            buf = ''
            
            if (ret = readytemp.recvfrom(_packetsz))
              
              buf = ret[0]
              from = ret[1]
              @answerfrom=(from[2])
              @answersize=(buf.length)
              
              print ';; answer from ' + \
              from[2].inspect +  ':' + \
              from[3].inspect + ' : ' + \
              buf.length.inspect + " bytes\n" if @debug
              
              ans, err = Net::DNS::Packet.new_from_binary(buf, @debug)
              
              if (ans!= nil)
                next unless ( ans.header.qr || @ignqrid)
                next unless  ( (ans.header.id == packet.header.id) || @ignqrid )
                @errorstring=(ans.header.rcode)
                ans.answerfrom=(@answerfrom)
                ans.answersize=(@answersize)
                if (ans.header.rcode != "NOERROR" && ans.header.rcode != "NXDOMAIN")
                  #                      # Remove this one from the stack
                  
                  print "RCODE: " + ans.header.rcode + "; trying next nameserver\n" if @debug
                  nmbrnsfailed+=1
                  nstemp[3]="RCODE: " + ans.header.rcode()
                  lastanswer=ans
                  #                          throw :nameserver
                  break
                end
              elsif (err != nil)
                @errorstring=(err)
              end
              
              return ans
            else
              @errorstring=($!)
              print ';; recv ERROR(' + \
              readytemp.peerhost + ':' + \
              readytemp.peerport + '): ' + \
              @errorstring + "\n" if @debug
              nstemp[3]="Recv error " + @errorstring
              nmbrnsfailed+=1
              # We want to remain in the SELECTOR LOOP...
              # unless there are no more nameservers
              return unless (nmbrnsfailed < ns.length)
              print ';; Number of failed nameservers: #{nmbrnsfailed} out of ' + ns.length + "\n" if @debug
              
            end
          end # not ready
        end #SELECTOR LOOP
      end # until stop_time loop
      #           end # :nameserver
    end #NAMESERVER LOOP
  end # retry times
  
  if (lastanswer!="")
    @errorstring=(lastanswer.header.rcode )
    return lastanswer
  end
  if (select.length > 0)
    # If there are valid handles then we have either a timeout or 
    # a send error.
    @errorstring=('query timed out') unless (@errorstring =~ /Send error:/)
  else
    if (nmbrnsfailed < ns.length)
      @errorstring=('Unexpected Error') ;
    else
      @errorstring=('all nameservers failed');
    end
  end
  return
end

#set_defaults ⇒ Object 



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# File 'lib/Net/DNS/Resolver.rb', line 413

def set_defaults
  # class defaults
  @nameservers	   = ['127.0.0.1']
  @port		   = 53
  @srcaddr        = '0.0.0.0'
  @srcport        = 0
  @domain	       = ''
  @searchlist	   = []
  @retrans	       = 5
  @retry		   = 4
  @usevc		   = false
  @stayopen       = false
  @igntc          = false
  @recurse        = true
  @defnames       = true
  @dnsrch         = true
  @debug          = false
  @errorstring	   = DEFAULT_ERROR_STRING
  @tsig_rr        = nil
  @answerfrom     = ''
  @answersize     = 0
  @querytime      = nil
  @tcp_timeout    = 120
  @udp_timeout    = nil
  @axfr_sel       = nil
  @axfr_rr        = []
  @axfr_soa_count = 0
  @persistent_tcp = false
  @persistent_udp = false
  @dnssec         = false
  @udppacketsize  = 0  # The actual default is lower bound by Net::DNS::PACKETSZ
  @force_v4       = false # force_v4 is only relevant when we have
  # v6 support available
  @cdflag         = 1  # this is only used when {dnssec} == 1
  @ignqrid        = false  # normally packets with non-matching ID 
  # or with the qr bit of are thrown away
  # in 'ignqrid' these packets are 
  # are accepted.
  # USE WITH CARE, YOU ARE VULNARABLE TO
  # SPOOFING IF SET.
  # This is may be a temporary feature
  
  
  #	# If we're running under a SOCKSified Perl, use TCP instead of UDP
  #	# and keep the sockets open.
  if (@usesocks)
    @usevc = true
    @persistent_tcp = true
  end
end

#tsig ⇒ Object 



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# File 'lib/Net/DNS/Resolver.rb', line 1987

def tsig
  return @tsig_rr
end

#tsig=(*args) ⇒ Object

Get or set the TSIG record used to automatically sign outgoing queries and updates. Call with an argument of 0 or ” to turn off automatic signing.

The default resolver behavior is not to sign any packets. You must call this method to set the key if you’d like the resolver to sign packets automatically.

You can also sign packets manually – see the Net::DNS::Packet and Net::DNS::Update manual pages for examples. TSIG records in manually-signed packets take precedence over those that the resolver would add automatically.

tsig = res.tsig

res.tsig(Net::DNS::RR.create("#{key_name} TSIG #{key}"))

tsig = Net::DNS::RR.create("#{key_name} TSIG #{key}")
tsig.fudge=(60)
res.tsig=(tsig)

res.tsig=(#{key_name}, #{key})

res.tsig=(0)



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# File 'lib/Net/DNS/Resolver.rb', line 1972

def tsig=(*args)
  if (args.length == 1)
    if (args[0] != nil)
      @tsig_rr = args[0]		
    else
      @tsig_rr = nil
    end	
  elsif (args.length == 2)
    key_name, key = args
    @tsig_rr = Net::DNS::RR.new("#{key_name} TSIG #{key}")
  end
  
  return @tsig_rr
end