NAME¶
Net::DHCP::Packet - Object methods to create a DHCP packet.
SYNOPSIS¶
use Net::DHCP::Packet;
my $p = new Net::DHCP::Packet->new(
'Chaddr' => '000BCDEF',
'Xid' => 0x9F0FD,
'Ciaddr' => '0.0.0.0',
'Siaddr' => '0.0.0.0',
'Hops' => 0);
DESCRIPTION¶
Represents a DHCP packet as specified in RFC 1533, RFC 2132.
CONSTRUCTOR¶
This module only provides basic constructor. For "easy" constructors,
you can use the Net::DHCP::Session module.
- new( )
- new( BUFFER )
- new( ARG => VALUE, ARG => VALUE... )
- Creates an "Net::DHCP::Packet" object, which can
be used to send or receive DHCP network packets. BOOTP is not supported.
Without argument, a default empty packet is created.
$packet = Net::DHCP::Packet();
A "BUFFER" argument is interpreted as a binary buffer like one
provided by the socket "recv()" function. if the packet is
malformed, a fatal error is issued.
use IO::Socket::INET;
use Net::DHCP::Packet;
$sock = IO::Socket::INET->new(LocalPort => 67, Proto => "udp", Broadcast => 1)
or die "socket: $@";
while ($sock->recv($newmsg, 1024)) {
$packet = Net::DHCP::Packet->new($newmsg);
print $packet->toString();
}
To create a fresh new packet "new()" takes arguments as a
key-value pairs :
ARGUMENT FIELD OCTETS DESCRIPTION
-------- ----- ------ -----------
Op op 1 Message op code / message type.
1 = BOOTREQUEST, 2 = BOOTREPLY
Htype htype 1 Hardware address type, see ARP section in "Assigned
Numbers" RFC; e.g., '1' = 10mb ethernet.
Hlen hlen 1 Hardware address length (e.g. '6' for 10mb
ethernet).
Hops hops 1 Client sets to zero, optionally used by relay agents
when booting via a relay agent.
Xid xid 4 Transaction ID, a random number chosen by the
client, used by the client and server to associate
messages and responses between a client and a
server.
Secs secs 2 Filled in by client, seconds elapsed since client
began address acquisition or renewal process.
Flags flags 2 Flags (see figure 2).
Ciaddr ciaddr 4 Client IP address; only filled in if client is in
BOUND, RENEW or REBINDING state and can respond
to ARP requests.
Yiaddr yiaddr 4 'your' (client) IP address.
Siaddr siaddr 4 IP address of next server to use in bootstrap;
returned in DHCPOFFER, DHCPACK by server.
Giaddr giaddr 4 Relay agent IP address, used in booting via a
relay agent.
Chaddr chaddr 16 Client hardware address.
Sname sname 64 Optional server host name, null terminated string.
File file 128 Boot file name, null terminated string; "generic"
name or null in DHCPDISCOVER, fully qualified
directory-path name in DHCPOFFER.
IsDhcp isDhcp 4 Controls whether the packet is BOOTP or DHCP.
DHCP conatains the "magic cookie" of 4 bytes.
0x63 0x82 0x53 0x63.
DHO_*code Optional parameters field. See the options
documents for a list of defined options.
See Net::DHCP::Constants.
Padding padding * Optional padding at the end of the packet
See below methods for values and syntax descrption.
Note: DHCP options are created in the same order as key-value pairs.
METHODS¶
ATTRIBUTE METHODS¶
- comment( [STRING] )
- Sets or gets the comment attribute (object meta-data
only)
- op( [BYTE] )
- Sets/gets the BOOTP opcode.
Normal values are:
BOOTREQUEST()
BOOTREPLY()
- htype( [BYTE] )
- Sets/gets the hardware address type.
Common value is: "HTYPE_ETHER()" (1) = ethernet
- hlen ( [BYTE] )
- Sets/gets the hardware address length. Value must be
between 0 and 16.
For most NIC's, the MAC address has 6 bytes.
- hops ( [BYTE] )
- Sets/gets the number of hops.
This field is incremented by each encountered DHCP relay agent.
- xid ( [INTEGER] )
- Sets/gets the 32 bits transaction id.
This field should be a random value set by the DHCP client.
- secs ( [SHORT] )
- Sets/gets the 16 bits elapsed boot time in
seconds.
- flags ( [SHORT] )
- Sets/gets the 16 bits flags.
0x8000 = Broadcast reply requested.
- ciaddr ( [STRING] )
- Sets/gets the client IP address.
IP address is only accepted as a string like '10.24.50.3'.
Note: IP address is internally stored as a 4 bytes binary string. See
"Special methods" below.
- yiaddr ( [STRING] )
- Sets/gets the your IP address.
IP address is only accepted as a string like '10.24.50.3'.
Note: IP address is internally stored as a 4 bytes binary string. See
"Special methods" below.
- siaddr ( [STRING] )
- Sets/gets the next server IP address.
IP address is only accepted as a string like '10.24.50.3'.
Note: IP address is internally stored as a 4 bytes binary string. See
"Special methods" below.
- giaddr ( [STRING] )
- Sets/gets the relay agent IP address.
IP address is only accepted as a string like '10.24.50.3'.
Note: IP address is internally stored as a 4 bytes binary string. See
"Special methods" below.
- chaddr ( [STRING] )
- Sets/gets the client hardware address. Its length is
given by the "hlen" attribute.
Valude is formatted as an Hexadecimal string representation.
Example: "0010A706DFFF" for 6 bytes mac address.
Note : internal format is packed bytes string. See "Special
methods" below.
- sname ( [STRING] )
- Sets/gets the "server host name". Maximum size is
63 bytes. If greater a warning is issued.
- file ( [STRING] )
- Sets/gets the "boot file name". Maximum size is
127 bytes. If greater a warning is issued.
- isDhcp ( [BOOLEAN] )
- Sets/gets the DHCP cookie. Returns whether the
cookie is valid or not, hence whether the packet is DHCP or BOOTP.
Default value is 1, valid DHCP cookie.
- padding ( [BYTES] )
- Sets/gets the optional padding at the end of the DHCP
packet, i.e. after DHCP options.
DHCP OPTIONS METHODS¶
This section describes how to read or set DHCP options. Methods are given in two
flavours : (i) text format with automatic type conversion, (ii) raw binary
format.
Standard way of accessing options is through automatic type conversion,
described in the "DHCP OPTION TYPES" section. Only a subset of types
is supported, mainly those defined in rfc 2132.
Raw binary functions are provided for pure performance optimization, and for
unsupported types manipulation.
- addOptionValue ( CODE, VALUE )
- Adds a DHCP option field. Common code values are listed in
"Net::DHCP::Constants" "DHO_"*.
Values are automatically converted according to their data types, depending
on their format as defined by RFC 2132. Please see "DHCP OPTION
TYPES" for supported options and corresponding formats.
If you nedd access to the raw binary values, please use
"addOptionRaw()".
$pac = Net::DHCP::Packet->new();
$pac->addOption(DHO_DHCP_MESSAGE_TYPE(), DHCPINFORM());
$pac->addOption(DHO_NAME_SERVERS(), "10.0.0.1", "10.0.0.2"));
- addSubOptionValue ( CODE, SUBCODE, VALUE )
- Adds a DHCP sub-option field. Common code values are listed
in "Net::DHCP::Constants" "SUBOPTION_"*.
Values are automatically converted according to their data types, depending
on their format as defined by RFC 2132. Please see "DHCP OPTION
TYPES" for supported options and corresponding formats.
If you nedd access to the raw binary values, please use
"addSubOptionRaw()".
$pac = Net::DHCP::Packet->new();
# FIXME update exampls
$pac->addSubOption(DHO_DHCP_MESSAGE_TYPE(), DHCPINFORM());
$pac->addSubOption(DHO_NAME_SERVERS(), "10.0.0.1", "10.0.0.2"));
- getOptionValue ( CODE )
- Returns the value of a DHCP option.
Automatic type conversion is done according to their data types, as defined
in RFC 2132. Please see "DHCP OPTION TYPES" for supported
options and corresponding formats.
If you nedd access to the raw binary values, please use
"getOptionRaw()".
Return value is either a string or an array, depending on the context.
$ip = $pac->getOptionValue(DHO_SUBNET_MASK());
$ips = $pac->getOptionValue(DHO_NAME_SERVERS());
- addOptionRaw ( CODE, VALUE )
- Adds a DHCP OPTION provided in packed binary format. Please
see corresponding RFC for manual type conversion.
- addSubOptionRaw ( CODE, SUBCODE, VALUE )
- Adds a DHCP SUB-OPTION provided in packed binary format.
Please see corresponding RFC for manual type conversion.
- getOptionRaw ( CODE )
- Gets a DHCP OPTION provided in packed binary format. Please
see corresponding RFC for manual type conversion.
- getSubOptionRaw ( CODE, SUBCODE )
- Gets a DHCP SUB-OPTION provided in packed binary format.
Please see corresponding RFC for manual type conversion.
- getSubOptionValue ()
- This is an empty stub for now
- removeSubOption ()
- This is an empty stub for now
- removeOption ( CODE )
- Remove option from option list.
- encodeRelayAgent ()
- These are half baked, but will encode the relay agent
options in the future
- decodeRelayAgent ()
- These are half baked, but will decode the relay agent
options in the future
- unpackRelayAgent ( HASH )
- returns a human readable 'relay agent options', not to be
confused with "decodeRelayAgent"
- addOption ( CODE, VALUE )
- Removed as of version 0.60. Please use
"addOptionRaw()" instead.
- getOption ( CODE )
- Removed as of version 0.60. Please use
"getOptionRaw()" instead.
-
DHCP OPTIONS TYPES¶
This section describes supported option types (cf. rfc 2132).
For unsupported data types, please use "getOptionRaw()" and
"addOptionRaw" to manipulate binary format directly.
- dhcp message type
- Only supported for DHO_DHCP_MESSAGE_TYPE (053) option.
Converts a integer to a single byte.
Option code for 'dhcp message' format:
(053) DHO_DHCP_MESSAGE_TYPE
Example:
$pac->addOptionValue(DHO_DHCP_MESSAGE_TYPE(), DHCPINFORM());
- string
- Pure string attribute, no type conversion.
Option codes for 'string' format:
(012) DHO_HOST_NAME
(014) DHO_MERIT_DUMP
(015) DHO_DOMAIN_NAME
(017) DHO_ROOT_PATH
(018) DHO_EXTENSIONS_PATH
(047) DHO_NETBIOS_SCOPE
(056) DHO_DHCP_MESSAGE
(060) DHO_VENDOR_CLASS_IDENTIFIER
(062) DHO_NWIP_DOMAIN_NAME
(064) DHO_NIS_DOMAIN
(065) DHO_NIS_SERVER
(066) DHO_TFTP_SERVER
(067) DHO_BOOTFILE
(086) DHO_NDS_TREE_NAME
(098) DHO_USER_AUTHENTICATION_PROTOCOL
Example:
$pac->addOptionValue(DHO_TFTP_SERVER(), "foobar");
- single ip address
- Exactly one IP address, in dotted numerical format
'192.168.1.1'.
Option codes for 'single ip address' format:
(001) DHO_SUBNET_MASK
(016) DHO_SWAP_SERVER
(028) DHO_BROADCAST_ADDRESS
(032) DHO_ROUTER_SOLICITATION_ADDRESS
(050) DHO_DHCP_REQUESTED_ADDRESS
(054) DHO_DHCP_SERVER_IDENTIFIER
(118) DHO_SUBNET_SELECTION
Example:
$pac->addOptionValue(DHO_SUBNET_MASK(), "255.255.255.0");
- multiple ip addresses
- Any number of IP address, in dotted numerical format
'192.168.1.1'. Empty value allowed.
Option codes for 'multiple ip addresses' format:
(003) DHO_ROUTERS
(004) DHO_TIME_SERVERS
(005) DHO_NAME_SERVERS
(006) DHO_DOMAIN_NAME_SERVERS
(007) DHO_LOG_SERVERS
(008) DHO_COOKIE_SERVERS
(009) DHO_LPR_SERVERS
(010) DHO_IMPRESS_SERVERS
(011) DHO_RESOURCE_LOCATION_SERVERS
(041) DHO_NIS_SERVERS
(042) DHO_NTP_SERVERS
(044) DHO_NETBIOS_NAME_SERVERS
(045) DHO_NETBIOS_DD_SERVER
(048) DHO_FONT_SERVERS
(049) DHO_X_DISPLAY_MANAGER
(068) DHO_MOBILE_IP_HOME_AGENT
(069) DHO_SMTP_SERVER
(070) DHO_POP3_SERVER
(071) DHO_NNTP_SERVER
(072) DHO_WWW_SERVER
(073) DHO_FINGER_SERVER
(074) DHO_IRC_SERVER
(075) DHO_STREETTALK_SERVER
(076) DHO_STDA_SERVER
(085) DHO_NDS_SERVERS
Example:
$pac->addOptionValue(DHO_NAME_SERVERS(), "10.0.0.11 192.168.1.10");
- pairs of ip addresses
- Even number of IP address, in dotted numerical format
'192.168.1.1'. Empty value allowed.
Option codes for 'pairs of ip address' format:
(021) DHO_POLICY_FILTER
(033) DHO_STATIC_ROUTES
Example:
$pac->addOptionValue(DHO_STATIC_ROUTES(), "10.0.0.1 192.168.1.254");
- byte, short and integer
- Numerical value in byte (8 bits), short (16 bits) or
integer (32 bits) format.
Option codes for 'byte (8)' format:
(019) DHO_IP_FORWARDING
(020) DHO_NON_LOCAL_SOURCE_ROUTING
(023) DHO_DEFAULT_IP_TTL
(027) DHO_ALL_SUBNETS_LOCAL
(029) DHO_PERFORM_MASK_DISCOVERY
(030) DHO_MASK_SUPPLIER
(031) DHO_ROUTER_DISCOVERY
(034) DHO_TRAILER_ENCAPSULATION
(036) DHO_IEEE802_3_ENCAPSULATION
(037) DHO_DEFAULT_TCP_TTL
(039) DHO_TCP_KEEPALIVE_GARBAGE
(046) DHO_NETBIOS_NODE_TYPE
(052) DHO_DHCP_OPTION_OVERLOAD
(116) DHO_AUTO_CONFIGURE
Option codes for 'short (16)' format:
(013) DHO_BOOT_SIZE
(022) DHO_MAX_DGRAM_REASSEMBLY
(026) DHO_INTERFACE_MTU
(057) DHO_DHCP_MAX_MESSAGE_SIZE
Option codes for 'integer (32)' format:
(002) DHO_TIME_OFFSET
(024) DHO_PATH_MTU_AGING_TIMEOUT
(035) DHO_ARP_CACHE_TIMEOUT
(038) DHO_TCP_KEEPALIVE_INTERVAL
(051) DHO_DHCP_LEASE_TIME
(058) DHO_DHCP_RENEWAL_TIME
(059) DHO_DHCP_REBINDING_TIME
Examples:
$pac->addOptionValue(DHO_DHCP_OPTION_OVERLOAD(), 3);
$pac->addOptionValue(DHO_INTERFACE_MTU(), 1500);
$pac->addOptionValue(DHO_DHCP_RENEWAL_TIME(), 24*60*60);
- multiple bytes, shorts
- A list a bytes or shorts.
Option codes for 'multiple bytes (8)' format:
(055) DHO_DHCP_PARAMETER_REQUEST_LIST
Option codes for 'multiple shorts (16)' format:
(025) DHO_PATH_MTU_PLATEAU_TABLE
(117) DHO_NAME_SERVICE_SEARCH
Examples:
$pac->addOptionValue(DHO_DHCP_PARAMETER_REQUEST_LIST(), "1 3 6 12 15 28 42 72");
SERIALIZATION METHODS¶
- serialize ()
- Converts a Net::DHCP::Packet to a string, ready to put on
the network.
- marshall ( BYTES )
- The inverse of serialize. Converts a string, presumably a
received UDP packet, into a Net::DHCP::Packet.
If the packet is malformed, a fatal error is produced.
HELPER METHODS¶
- toString ()
- Returns a textual representation of the packet, for
debugging.
- packinet ( STRING )
- Transforms a IP address "xx.xx.xx.xx" into a
packed 4 bytes string.
These are simple never failing versions of inet_ntoa and inet_aton.
- packinets ( STRING )
- Transforms a list of space delimited IP addresses into a
packed bytes string.
- packinets_array( LIST )
- Transforms an array (list) of IP addresses into a packed
bytes string.
- unpackinet ( STRING )
- Transforms a packed bytes IP address into a
"xx.xx.xx.xx" string.
- unpackinets ( STRING )
- Transforms a packed bytes liste of IP addresses into a list
of "xx.xx.xx.xx" space delimited string.
- unpackinets_array ( STRING )
- Transforms a packed bytes liste of IP addresses into a
array of "xx.xx.xx.xx" strings.
SPECIAL METHODS¶
These methods are provided for performance tuning only. They give access to
internal data representation , thus avoiding unnecessary type conversion.
- ciaddrRaw ( [STRING])
- Sets/gets the client IP address in packed 4
characters binary strings.
- yiaddrRaw ( [STRING] )
- Sets/gets the your IP address in packed 4 characters
binary strings.
- siaddrRaw ( [STRING] )
- Sets/gets the next server IP address in packed 4
characters binary strings.
- giaddrRaw ( [STRING] )
- Sets/gets the relay agent IP address in packed 4
characters binary strings.
- chaddrRaw ( [STRING] )
- Sets/gets the client hardware address in packed
binary string. Its length is given by the "hlen" attribute.
EXAMPLES¶
Sending a simple DHCP packet:
#!/usr/bin/perl
# Simple DHCP client - sending a broadcasted DHCP Discover request
use IO::Socket::INET;
use Net::DHCP::Packet;
use Net::DHCP::Constants;
# creat DHCP Packet
$discover = Net::DHCP::Packet->new(
xid => int(rand(0xFFFFFFFF)), # random xid
Flags => 0x8000, # ask for broadcast answer
DHO_DHCP_MESSAGE_TYPE() => DHCPDISCOVER()
);
# send packet
$handle = IO::Socket::INET->new(Proto => 'udp',
Broadcast => 1,
PeerPort => '67',
LocalPort => '68',
PeerAddr => '255.255.255.255')
or die "socket: $@"; # yes, it uses $@ here
$handle->send($discover->serialize())
or die "Error sending broadcast inform:$!\n";
Sniffing DHCP packets.
#!/usr/bin/perl
# Simple DHCP server - listen to DHCP packets and print them
use IO::Socket::INET;
use Net::DHCP::Packet;
$sock = IO::Socket::INET->new(LocalPort => 67, Proto => "udp", Broadcast => 1)
or die "socket: $@";
while ($sock->recv($newmsg, 1024)) {
$packet = Net::DHCP::Packet->new($newmsg);
print STDERR $packet->toString();
}
Sending a LEASEQUERY (provided by John A. Murphy).
#!/usr/bin/perl
# Simple DHCP client - send a LeaseQuery (by IP) and receive the response
use IO::Socket::INET;
use Net::DHCP::Packet;
use Net::DHCP::Constants;
$usage = "usage: $0 DHCP_SERVER_IP DHCP_CLIENT_IP\n"; $ARGV[1] || die $usage;
# create a socket
$handle = IO::Socket::INET->new(Proto => 'udp',
Broadcast => 1,
PeerPort => '67',
LocalPort => '67',
PeerAddr => $ARGV[0])
or die "socket: $@"; # yes, it uses $@ here
# create DHCP Packet
$inform = Net::DHCP::Packet->new(
op => BOOTREQUEST(),
Htype => '0',
Hlen => '0',
Ciaddr => $ARGV[1],
Giaddr => $handle->sockhost(),
Xid => int(rand(0xFFFFFFFF)), # random xid
DHO_DHCP_MESSAGE_TYPE() => DHCPLEASEQUERY
);
# send request
$handle->send($inform->serialize()) or die "Error sending LeaseQuery: $!\n";
#receive response
$handle->recv($newmsg, 1024) or die;
$packet = Net::DHCP::Packet->new($newmsg);
print $packet->toString();
A simple DHCP Server is provided in the "examples" directory. It is
composed of "dhcpd.pl" a *very* simple server example, and
"dhcpd_test.pl" a simple tester for this server.
AUTHOR¶
Dean Hamstead <djzort@cpan.org> Previously Stephan Hadinger
<shadinger@cpan.org>. Original version by F. van Dun.
BUGS¶
See
https://rt.cpan.org/Dist/Display.html?Queue=Net-DHCP
<
https://rt.cpan.org/Dist/Display.html?Queue=Net-DHCP>
COPYRIGHT¶
This is free software. It can be distributed and/or modified under the same
terms as Perl itself.
SEE ALSO¶
Net::DHCP::Options, Net::DHCP::Constants.
