Michael Robinton

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

dn_expand is from Michael Fuhr's Net::DNS package (DNS.pm), copyright (c) 1997-2002. Thank you Michael.

COPYRIGHT

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

Michael Robinton <michael@bizsystems.com>

All rights reserved.

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.

See also:

Net::DNS::Codes(3), Net::DNS::ToolKit::RR(3), Net::DNS::ToolKit::Debug(3), Net::DNS::ToolKit::Utilities, NetAdder::IP::Util