Net::DNS::ToolKit - tools for working with DNS packets
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
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);
$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();
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 for individual Resource Record methods.
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(... $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(...
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
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.
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).
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
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.
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
Get the flag bits from the header
input: pointer to buffer, returns: flag bits
Get the contents of the qdcount.
input: pointer to buffer, returns: 16 bit integer,
Get the contents of the ancount.
input: pointer to buffer, returns: 16 bit integer,
Get the contents of the nscount.
input: pointer to buffer, returns: 16 bit integer,
Get the contents of the arcount.
input: pointer to buffer, returns: 16 bit integer,
Put a 16 bit integer into qdcount. Return an offset to ancount.
input: pointer to buffer,
16 bit integer,
returns: offset to ancount
Put a 16 bit integer into ancount. Return an offset to nscount.
input: pointer to buffer,
16 bit integer,
returns: offset to nscount
Put a 16 bit chunk into nscount. Return an offset to arcount.
input: pointer to buffer,
16 bit integer,
returns: offset to arcount
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
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.
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
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.
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
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
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,
$id,$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
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 $buffer = '';
newhead(\$buffer,
1234, # ID
QR | BITS_QUERY | RD,
1, # questions
5, # answers
2, # ns authority
3, # glue records
);
print_head(\$buffer);
print_buf(\$buffer);
Will produce the following output:
ID => 1234
QR => 1
OPCODE => QUERY
AA => 0
TC => 0
RD => 1
RA => 0
Z => 0
AD => 0
CD => 0
RCODE => NOERROR
QDCOUNT => 1
ANCOUNT => 5
NSCOUNT => 2
ARCOUNT => 3
0 : 0000_0100 0x04 4
1 : 1101_0010 0xD2 210
2 : 1000_0001 0x81 129
3 : 0000_0000 0x00 0
4 : 0000_0000 0x00 0
5 : 0000_0001 0x01 1
6 : 0000_0000 0x00 0
7 : 0000_0101 0x05 5
8 : 0000_0000 0x00 0
9 : 0000_0010 0x02 2
10 : 0000_0000 0x00 0
11 : 0000_0011 0x03 3
return strings for the character in:
binary hex decimal ascii
0011_1001 0x39 57 9
as appropriate. Ascii is only
returned if printable.
A simple script using this routine can provide a view into a DNS packet to examine the bits and byte. Very useful while writing DNS client and server routines. See the example below.
Expands a compressed domain name into a full domain name.
input: pointer to buffer,
offset into buffer
returns: expanded name,
pointer to next RR
Compress a domain name and append it to the buffer.
input: pointer to buffer,
offset to insertion point,
(usually end of buffer)
pointer to name,
pointer to array of offsets of
previously compressed names,
returns: new offset to end of buffer,
updated array of offsets to
previous compressed names,
NOTES: 1) When the first domain name
is compressed, the \@dnptrs
array is ommited. dn_comp
will return an initialized
array that can then be used
for subsequent calls.
i.e. initial call
($newoff,@dnptrs)=dn_comp(\$name,\$buffer,$offset);
2) compression can be suppressed
for test purposes if the pointer
to $name is stored in a glob
reference rather than a scalar.
i.e. $name = 'hostname.com';
local *glob = \$name;
($newoff,@dnptrs)=dn_comp(\$buffer,$offset,\*glob);
[use a pointer to *glob]
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
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
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
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
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
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
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
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.
Remove the leading character(s) from a type/class label.
input: label # like T_MX or C_IN returns: tag # MX, IN
Return a list of name server addresses in packed network form for use by this host.
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)
To install this module, type:
perl Makefile.PL
make
make test
make install
perl 5.00503
Net::DNS::Codes 0.06
See the scripts directory in this distribution
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.
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
None
get1char get16 get32 put1char put16 put32 getIPv4 putIPv4 getIPv6 putIPv6 getstring putstring dn_comp dn_expand parse_char gethead newhead getflags 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
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.
Michael Robinton <michael@bizsystems.com>
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 2003 - 2008, Michael Robinton <michael@bizsystems.com>
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
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 the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
Net::DNS::Codes(3), Net::DNS::ToolKit::RR(3), Net::DNS::ToolKit::Debug(3), Net::DNS::ToolKit::Utilities, NetAdder::IP::Util
