NAME

Net::DNS::ToolKit - tools for working with DNS packets

SYNOPSIS

  use Net::DNS::ToolKit qw(

	get1char
	get16
	get32
	put1char
	put16
	put32
	getIPv4
	putIPv4
	putIPv6
	getIPv6
	getstring
	putstring
	dn_comp
	dn_expand
	parse_char
	gethead
	newhead
	getflags
	putflags
	get_qdcount
	get_ancount
	get_nscount
	get_arcount
	put_qdcount
	put_ancount
	put_nscount
	put_arcount
	inet_aton
	inet_ntoa
	ipv6_aton
	ipv6_n2x
	ipv6_n2d   
	sec2time
	ttlAlpha2Num
	collapse
	strip
	get_ns
	gettimeofday
  );

  $char = get1char(\$buffer,$offset);
  ($int, $newoff)  = get16(\$buffer,$offset);
  ($long, $newoff) = get32(\$buffer,$offset);
  $newoff = put1char(\$buffer,$offset,$u_char);
  $newoff = put16(\$buffer,$offset,$int);
  $newoff = put32(\$buffer,$offset,$long);
  $flags = getflags(\$buffer);
  true = putflags(\$buffer,$flags);
  $int = get_qdcount(\$buffer);
  $int = get_ancount(\$buffer);
  $int = get_nscount(\$buffer);
  $int = get_arcount(\$buffer);
  $newoff = put_qdcount(\$buffer,$int);
  $newoff = put_ancount(\$buffer,$int);
  $newoff = put_nscount(\$buffer,$int);
  $newoff = put_arcount(\$buffer,$int);
  ($netaddr,$newoff)=getIPv4(\$buffer,$offset);
  $newoff = putIPv4(\$buffer,$offset,$netaddr);
  ($ipv6addr,$newoff)=getIPv6(\$buffer,$offset);
  $newoff = putIPv6(\$buffer,$offset,$ipv6addr);
  ($offset,
   $id,$qr,$opcode,$aa,$tc,$rd,$ra,$mbz,$ad,$cd,$rcode,
   $qdcount,$ancount,$nscount,$arcount)
	= gethead(\$buffer);
  $newoff = newhead(\$buffer,$id,$flags,
	$qdcount,$ancount,$nscount,$arcount);
  ($b,$h,$d,$a)=parse_char($char);
  ($newoff,$name) = dn_expand(\$buffer,$offset);
  ($newoff,@dnptrs)=dn_comp(\$buffer,$offset,\$name,\@dnptrs);
  $dotquad = inet_ntoa($netaddr);
  $netaddr = inet_aton($dotquad);
  $ipv6addr = ipv6_aton($ipv6_text);
  $hex_text = ipv6_n2x($ipv6addr);
  $dec_text = ipv6_n2d($ipv6addr);
  $timetxt = sec2time($seconds);
  $seconds = ttlAlpha2Num($timetext);
  $shorthost = collapse($zonename,$longhost);
  $tag = strip($P_tag);
  @nameservers = get_ns();
  ($secs,$usecs) = gettimeofday();

DESCRIPTION

Routines to pick apart, examine and put together DNS packets. They can be used for diagnostic purposes or as building blocks for DNS applications such as DNS servers and clients or to allow user applications to interact directly with remote DNS servers.

  See: Net::DNS::ToolKit:RR and the subdirectory
	lib/Net/DNS/ToolKit/RR/
  for individual Resource Record methods.

  Net::DNS::ToolKit does not handle every type of RR with context
  help for the record format. HOWEVER, it does handle all unknown
  record types per RFC-3597 so if your program can manipulate the
  binary and/or hex representation of the data as proscribed in RFC-3597 this
  module will always work for you.

A good example of full utilization of this module is Net::DNS::Dig/module.

See: Net::DNS::ToolKit::RR (included in this distribution) for a complete description of how to use this module and the accompanying Resource Records tools.

FUNCTIONS

These functions return a value and offset in list context and first value only in scalar context.

($int,$newoff)	= get16(...
($long,$newoff)	= get32(...
($netaddr,$newoff)	= getIPv4(...
($ipv6addr,$newoff)	= getIPv6(...
($string,$newoff)	= getstring(...
($newoff,$name)	= dn_expand(...
($secs,$usecs)	= gettimeofday(...

These functions return only a value or an offset.

$newoff	= put1char(...
$newoff	= put16(...  
$newoff	= put32(...
$newoff	= put_qdcount(...
$newoff	= put_ancount(...
$newoff	= put_nscount(...
$newoff	= put_arcount(...
$newoff	= putIPv4(...
$newoff	= putIPv4(...
$newoff	= putstring(...
$newoff	= newhead(...
$flags	= getflags(...
true		= putflags(...
$int		= get_qdcount(...
$int		= get_ancount(...
$int		= get_nscount(...
$int		= get_arcount(...
$char		= get1char(...
$dotquad	= inet_ntoa(...
$netaddr	= inet_aton(...
$timetxt	= sec2time(...
$seconds	= ttlAlpha2Num(...
$tag		= strip(...
$shorthost	= collapse(...

This function always return list context prefixed by a new offset.

($newoff,@dnptrs) = dn_comp(...
($offset,@list)   = gethead(...

These functions always return list context.

@list		= parse_char(...
@nameservers	= get_ns(...

$char = get1char(\$buffer,$offset);

Get a single character from the buffer at $offset

  input:	pointer to buffer,
		offset into buffer
  output:	the "character"   
           or	undef if the pointer
		is outside the buffer

($int, $newoff) = get16(\$buffer,$offset);

Get a 16 bit integer from the buffer at $offset. Return the value and a new offset pointing at the next character.

Returns and empty array on error.
```
  input:	pointer to buffer,
		offset into buffer
  returns:	16 bit integer,
		offset + size of int
```
In SCALAR context, returns just the value.
$newoff = put1char(\$buffer,$offset,$u_char);

Put an unsigned 8 bit value into the buffer at $offset. Return the value of the new offset pointer to the next char (usually end of buffer).
$newoff = put16(\$buffer,$offset,$int);

Put a 16 bit integer into the buffer at $offset. Return the value of the new offset pointer to the the next char (usually end of buffer).
```
  input:	pointer to buffer,
		offset into buffer,
		16 bit integer
  returns:	offset + size of int
```
($long, $newoff) = get32(\$buffer,$offset);

Get a 32 bit long from the buffer at $offset. Return the long and a new offset pointing at the next character.

Returns and empty array on error.
```
  input:	pointer to buffer,
		offset into buffer
  returns:	32 bit long,
		offset + size long
```
In SCALAR context, returns just the value.
$newoff = put32(\$buffer,$offset,$long);

Put a 32 bit long into the buffer at $offset. Return the value of the new offset pointer to the the next char (usually end of buffer).
```
  input:	pointer to buffer,
		offset into buffer,
		32 bit long
  returns:	offset + size of int
```
$flags = getflags(\$buffer);

Get the flag bits from the header
```
input:	pointer to buffer,
returns:	flag bits
```

putflags(\$buffer,$flags);

Put flags bits back in header

  input:	pointer to buffer,
		flags bits
  returns:	n/a

$int = get_qdcount(\$buffer);

Get the contents of the qdcount.
```
input:	pointer to buffer,
returns:	16 bit integer,
```
$int = get_ancount(\$buffer);

Get the contents of the ancount.
```
input:	pointer to buffer,
returns:	16 bit integer,
```
$int = get_nscount(\$buffer);

Get the contents of the nscount.
```
input:	pointer to buffer,
returns:	16 bit integer,
```
$int = get_arcount(\$buffer);

Get the contents of the arcount.
```
input:	pointer to buffer,
returns:	16 bit integer,
```
$newoff = put_qdcount(\$buffer,$int);

Put a 16 bit integer into qdcount. Return an offset to ancount.
```
  input:	pointer to buffer,
		16 bit integer,
  returns:	offset to ancount
```
$newoff = put_ancount(\$buffer,$int);

Put a 16 bit integer into ancount. Return an offset to nscount.
```
  input:	pointer to buffer,
		16 bit integer,
  returns:	offset to nscount
```
$newoff = put_nscount(\$buffer,$int);

Put a 16 bit chunk into nscount. Return an offset to arcount.
```
  input:	pointer to buffer,
		16 bit integer,
  returns:	offset to arcount
```
$newoff = put_arcount(\$buffer,$int);

Put a 16 bit integer into arcount. Return an offset to answer section.
```
  input:	pointer to buffer,
		16 bit integer,
  returns:	offset to question section
```
($netaddr,$newoff)=getIPv4(\$buffer,$offset);

Get an IPv4 network address from the buffer at $offset. Return the netaddr and a new offset pointing at the next character beyond.

Returns and empty array on error.
```
  input:	pointer to buffer,
		offset into buffer
  returns:	netaddr,
		offset + size of ipaddr
```
In SCALAR context, returns just netaddr.
$newoff = putIPv4(\$buffer,$offset,$netaddr);

Put a netaddr into the buffer. Return the value of the new offset pointer to the next char (usually end of buffer).
```
  input:	pointer to buffer,
		offset into buffer,
		packed IPv4 net address
  returns:	pointer to end of buffer
```
($ipv6addr,$newoff)=getIPv6(\$buffer,$offset);

Get an IPv6 network address from the buffer at $offset. Return the ipv6addr and a new offset pointing at the next character beyond.

Returns and empty array on error.
```
  input:	pointer to buffer,
		offset into buffer
  returns:	ipv6addr,
		offset + size of ipv6addr
```
IN SCALAR context, returns just ipv6addr.
$newoff = putIPv6(\$buffer,$offset,$ipv6addr);

Put an ipv6addr into the buffer. Return the value of the new offset pointer to the next char (usually end of buffer).
```
  input:	pointer to buffer,
		offset into buffer,
		128 bit IPv6 net address
  returns:	pointer to end of buffer
```

($string,$newoff) = getstring(\$buffer,$offset,$length);

Return a string of $length from the buffer.

  input:	pointer to buffer,
		offset,
		length of string
  returns:	string,
		new offset to end
		off string in buffer

$newoff = putstring(\$buffer,$offset,\$string);

Append a string to $buffer at $offset.

  input:	pointer to buffer,
		offset into buffer,
		pointer to string
  returns:	new offset to end of buffer

($offset,@headitems) = gethead(\$buffer);

  ($offset,
  $id,$qr,$opcode,$aa,$tc,$rd,$ra,$mbz,$ad,$cd,$rcode,
   $qdcount,$ancount,$nscount,$arcount)
        = gethead(\$buffer);

  Get the numeric codes for header variables

    0  1  2  3  4  5  6  7  8  9 10 11 12 13 14 15
  -------------------------------------------------
   15 14 13 12 11 10  9  8  7  6  5  4  3  2  1  0
  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
  |                      ID                       |
  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
  |QR|   Opcode  |AA|TC|RD|RA| Z|AD|CD|   RCODE   |
  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
  |                    QDCOUNT                    |
  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
  |                    ANCOUNT                    |
  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
  |                    NSCOUNT                    |
  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
  |                    ARCOUNT                    |
  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+

  The length of this header is NS_HFIXEDSZ

  input:	pointer to message buffer
  returns:	offset to question section,
		array of variables

$newoff=newhead(\$buffer, $id,$flags,$qdcount,$ancount,$nscount,$arcount);

Creat a new header and return the offset to question

  input:	\$buffer
		$id,
		$flags,
		$qdcount,
		$ancount,
		$nscount,
		$arcount
  returns:	offset to question = NS_HFIXEDSZ
	    or	undefined on error

  If qdcount, ancount, nscount, arcount are
  not present, then they will be set to zero.

  example dump script:

  use lib qw(blib/lib blib/arch);
  use Net::DNS::Codes qw(:all);
  use Net::DNS::ToolKit::Debug qw(
	print_head
	print_buf
  );
  use Net::DNS::ToolKit qw(
        get1char
        parse_char
        newhead
  );
  my $buffer = '';
  newhead(\$buffer,
        1234,                   # ID
        QR | BITS_QUERY | RD,
        1,                      # questions
        5,                      # answers
        2,                      # ns authority
        3,                      # glue records
  );

  print_head(\$buffer);
  print_buf(\$buffer);

  Will produce the following output:

  ID     => 1234    
  QR      => 1    
  OPCODE  => QUERY
  AA      => 0
  TC      => 0
  RD      => 1
  RA      => 0
  Z       => 0
  AD      => 0
  CD      => 0
  RCODE   => NOERROR
  QDCOUNT => 1
  ANCOUNT => 5
  NSCOUNT => 2
  ARCOUNT => 3
  0     :  0000_0100  0x04    4    
  1     :  1101_0010  0xD2  210    
  2     :  1000_0001  0x81  129    
  3     :  0000_0000  0x00    0    
  4     :  0000_0000  0x00    0    
  5     :  0000_0001  0x01    1    
  6     :  0000_0000  0x00    0    
  7     :  0000_0101  0x05    5    
  8     :  0000_0000  0x00    0    
  9     :  0000_0010  0x02    2    
  10    :  0000_0000  0x00    0    
  11    :  0000_0011  0x03    3

($b,$h,$d,$a) = parse_char($char);
```
return strings for the character in:

  binary    hex   decimal   ascii
0011_1001  0x39      57      9

as appropriate. Ascii is only 
returned if printable.
```
A simple script using this routine can provide a view into a DNS packet to examine the bits and byte. Very useful while writing DNS client and server routines. See the example below.
($name,$newoff) = dn_expand(\$buffer,$offset);

Expands a compressed domain name into a full domain name.
```
  input:	pointer to buffer,
		offset into buffer
  returns:	expanded name,
		pointer to next RR
```

($newoff,@dnptrs)=dn_comp(\$buffer,$offset,\$name,\@dnptrs);

Compress a domain name and append it to the buffer.

  input:	pointer to buffer,
		offset to insertion point,
	(usually end of buffer)
		pointer to name,
		pointer to array of offsets of
		  previously compressed names,
  returns:	new offset to end of buffer,
		updated array of offsets to 
		  previous compressed names,

  NOTES:   1)	When the first domain name
		is compressed, the \@dnptrs
		array is ommited. dn_comp
		will return an initialized
		array that can then be used
		for subsequent calls.

	  i.e.	initial call

  ($newoff,@dnptrs)=dn_comp(\$buffer,$offset,\$name);

	   2) if \@dnptrs is null, no compression takes place

$dotquad = inet_ntoa($netaddr);

Convert a packed IPv4 network address to a dot-quad IP address.
```
input:	packed network address
returns:	IP address i.e. 10.4.12.123
```
Imported/Exported from NetAdder::IP::Util
$netaddr = inet_aton($dotquad);

Convert a dot-quad IP address into an IPv4 packed network address.
```
input:	IP address i.e. 192.5.16.32
returns:	packed network address
```
Imported/Exported from NetAdder::IP::Util
$ipv6addr = ipv6_aton($ipv6_text);

Takes an IPv6 address of the form described in rfc1884 and returns a 128 bit binary RDATA string.
```
input:	ipv6 text
returns:	128 bit RDATA string
```
Imported/Exported from NetAdder::IP::Util
$hex_text = ipv6_n2x($ipv6addr);

Takes an IPv6 RDATA string and returns an 8 segment IPv6 hex address
```
input:	128 bit RDATA string
returns:	x:x:x:x:x:x:x:x
```
Imported/Exported from NetAdder::IP::Util
$dec_text = ipv6_n2d($ipv6addr);

Takes an IPv6 RDATA string and returns a mixed hex - decimal IPv6 address with the 6 uppermost chunks in hex and the lower 32 bits in dot-quad representation.
```
input:	128 bit RDATA string
returns:	x:x:x:x:x:x:d.d.d.d
```
Imported/Exported from NetAdder::IP::Util
$timetxt = sec2time($seconds);

Convert numeric seconds into a string of the form
```
NNw NNd NNh NNm NNs
```
for weeks, days, hours, minutes, seconds respectively.
```
input:	seconds
returns:	elapsed time text
```
$seconds = ttlAlpha2Num($timetext);

Convert a string of time text of the form
```
NNw NNd NNh NNm NNs
```
into seconds. Upper case is OK.
```
  input:	ttl in form numeric
		or alpha numeric
  returns:	seconds
```
$shorthost = collapse($zonename,$longhost);

Remove the zone portion of a fully qualified domain name and return the host portion.
```
  input:	zone name,
		fqdn
  returns:	short host name

  i.e.	zone = bar.com
	fqdn = foo.bar.com

  foo = collapse(zone,fqdn);
```
Testing is not case sensitive. If the fqdn does not end in the zone name then the fqdn is returned.
$tag = strip($P_tag);

Remove the leading character(s) from a type/class label.
```
input:     label  # like T_MX or C_IN
returns:   tag    # MX, IN
```
@nameservers = get_ns();

Return a list of name server addresses in packed network form for use by this host.
($secs,$usecs) = gettimeofday();

Returns a time value that is accurate to the nearest microsecond but also has a range of years.
```
  input:    none
  returns:  seconds since epoch,
	    microseconds (of current sec)
```

INSTALLATION

To install this module, type:

perl Makefile.PL
make
make test
make install

DEPENDENCIES

perl 5.00503
Net::DNS::Codes 0.06

EXAMPLES

See the scripts directory in this distribution

dig.pl

A script that functions like dig in the BIND distribution. It provides additional functionality in that it will dump the packet buffer contents for inspection in debug mode. It is easily modified to add features.

Syntax:
dig.pl [@server] [+tcp] [-d] [-p port#] [-t type] name

server is the name or IP address of the name server to query.  An IPv4
       address can be provided in dotted-decimal notation.  When the
       supplied server argument is a hostname, dig resolves that name
       before querying that name server.

 +tcp  only use TCP protocol

 -d    print the query to the console

 -p    port# is the port number that dig.pl will send its queries 
       instead of the standard DNS port number 53.

 -t    indicates what type of query is required. This script supports
       only A, MX, NS, CNAME, SOA, TXT, and ANY queries as well as
       AXFR record transfers. If no type argument is supplied, dig.pl
       will perform a lookup for an A record

name   is the name of the resource record that is to be looked up.

rdns_blk.pl

A script to lookup an entire class "C" set of PTR records recursively. This is useful hunting spam domains where many DNS's do not allow AXFR record transfers to inspect what is in a range of IP addresses.
```
Syntax:
 ./rdns_blk.pl nn.nn.nn[.nn]

 at least the first three groups of 
 dot.quad.addr numbers

 returns PTR results for 1..255 of address range
 skips non-existent records, notes timeouts
```

EXPORT

None

EXPORT_OK

get1char get16 get32 put1char put16 put32 getIPv4 putIPv4 getIPv6 putIPv6 getstring putstring dn_comp dn_expand parse_char gethead newhead getflags putflags get_qdcount get_ancount get_nscount get_arcount put_qdcount put_ancount put_nscount put_arcount inet_aton inet_ntoa ipv6_aton ipv6_n2x ipv6_n2d sec2time ttlAlpha2Num collapse strip get_ns gettimeofday

BUGS

There have been some reports of the "C" library function for

"int res_init(void);

not properly returning the local resolver nameserver configuration information for certain Perl 5.6 -> 5.8 hosts. This is for the ToolKit function "get_ns()".

I have been unable to duplicate this on any of the ix86 Linux or Sun-Sparc systems that I have. If you have a system that exhibits this problem and can provide a user account, I'd appreciate it if you would contact me so I can fix it.

Update v0.38 Thu Oct 2 14:49:26 PDT 2008 This may be an issue with sharing of the __res_state structure. The update uses a private __res_state structure rather than the shared one and calling res_ninit(*private_res). Hopefully this will fix the problem.

AUTHOR

Michael Robinton <michael@bizsystems.com>

ACKNOWLEDGEMENTS

The following functions are used in whole or in part as include files to ToolKit.xs. The copyrights are include in the respective files.

file:           functions:

dn_expand.inc   dn_expand

COPYRIGHT

 Copyright 2003 - 2014, Michael Robinton <michael@bizsystems.com>

Michael Robinton <michael@bizsystems.com>

This program is free software; you can redistribute it and/or modify it under the terms of either:

a) the GNU General Public License as published by the Free
Software Foundation; either version 2, or (at your option) any
later version, or

b) the "Artistic License" which comes with this distribution.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See either the GNU General Public License or the Artistic License for more details.

You should have received a copy of the Artistic License with this distribution, in the file named "Artistic". If not, I'll be glad to provide one.

You should also have received a copy of the GNU General Public License along with this program in the file named "Copying". If not, write to the

Free Software Foundation, Inc.
59 Temple Place, Suite 330
Boston, MA  02111-1307, USA

or visit their web page on the internet at:

http://www.gnu.org/copyleft/gpl.html.

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