Net::DHCP::Packet - Object methods to create a DHCP packet.
version 0.7_007
use Net::DHCP::Packet; my $p = Net::DHCP::Packet->new( 'Chaddr' => '000BCDEF', 'Xid' => 0x9F0FD, 'Ciaddr' => '0.0.0.0', 'Siaddr' => '0.0.0.0', 'Hops' => 0 );
Represents a DHCP packet as specified in RFC 1533, RFC 2132.
This module only provides basic constructor. For "easy" constructors, you can use the Net::DHCP::Session module.
Creates an Net::DHCP::Packet object, which can be used to send or receive DHCP network packets. BOOTP is not supported.
Net::DHCP::Packet
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.
BUFFER
recv()
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 :
new()
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 description.
Note: DHCP options are created in the same order as key-value pairs.
See Net::DHCP::Packet::Attributes
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.
Adds a DHCP option field. Common code values are listed in Net::DHCP::Constants DHO_*.
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 need access to the raw binary values, please use addOptionRaw().
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"));
Adds a DHCP sub-option field. Common code values are listed in Net::DHCP::Constants SUBOPTION_*.
SUBOPTION_
If you need access to the raw binary values, please use addSubOptionRaw().
addSubOptionRaw()
$pac = Net::DHCP::Packet->new(); # FIXME update examples $pac->addSubOption(DHO_DHCP_MESSAGE_TYPE(), DHCPINFORM()); $pac->addSubOption(DHO_NAME_SERVERS(), "10.0.0.1", "10.0.0.2"));
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 need access to the raw binary values, please use getOptionRaw().
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());
Adds a DHCP OPTION provided in packed binary format. Please see corresponding RFC for manual type conversion.
BOOLEAN indicates if options should be inserted in the order provided. Default is to sort options to work around known quirky clients. See "QUIRK WORK-AROUNDS"
Adds a DHCP SUB-OPTION provided in packed binary format. Please see corresponding RFC for manual type conversion.
Gets a DHCP OPTION provided in packed binary format. Please see corresponding RFC for manual type conversion.
Gets a DHCP SUB-OPTION provided in packed binary format. Please see corresponding RFC for manual type conversion.
This is an empty stub for now
Remove option from option list.
returns the packed Client-identifier (pass-through currently)
returns the unpacked clientid.
Decodes: type 0 as a string type 1 as a mac address (hex string) everything is passed through
returns the packed sip server field (pass-through currently)
returns the unpacked sip server.
Decodes: type 1 as an ipv4 address everything is passed through
returns the packed Classless Static Route option built from a list of CIDR style address/mask combos
Not implemented, currently croaks.
Removed as of version 0.60. Please use addOptionRaw() instead.
Removed as of version 0.60. Please use getOptionRaw() instead.
This section describes supported option types (cf. RFC 2132).
For unsupported data types, please use getOptionRaw() and addOptionRaw to manipulate binary format directly.
addOptionRaw
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());
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
$pac->addOptionValue(DHO_TFTP_SERVER(), "foobar");
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
$pac->addOptionValue(DHO_SUBNET_MASK(), "255.255.255.0");
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
$pac->addOptionValue(DHO_NAME_SERVERS(), "10.0.0.11 192.168.1.10");
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
$pac->addOptionValue(DHO_STATIC_ROUTES(), "10.0.0.1 192.168.1.254");
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);
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
$pac->addOptionValue(DHO_DHCP_PARAMETER_REQUEST_LIST(), "1 3 6 12 15 28 42 72");
Converts a Net::DHCP::Packet to a string, ready to put on the network.
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.
Returns a textual representation of the packet, for debugging.
Transforms an list of lists into packed option. For option 43 (vendor specific), 82 (relay agent) etc.
Unpacks sub-options to a list of lists
See also Net::DHCP::Packet::IPv4Utils
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.
Net::DHCP::Options, Net::DHCP::Constants, Net::DHCP::IPv4Utils, Net::DHCP::Attributes, Net::DHCP::OrderOptions.
Dean Hamstead <dean@bytefoundry.com.au>
This software is copyright (c) 2016 by Dean Hamstad.
This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.
To install Net::DHCP, copy and paste the appropriate command in to your terminal.
cpanm
cpanm Net::DHCP
CPAN shell
perl -MCPAN -e shell install Net::DHCP
For more information on module installation, please visit the detailed CPAN module installation guide.