| Net::DHCP::Packet(3pm) | User Contributed Perl Documentation | Net::DHCP::Packet(3pm) |
Net::DHCP::Packet - Object methods to create a DHCP packet.
version 0.696
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.
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 description.
Note: DHCP options are created in the same order as key-value pairs.
Normal values are:
BOOTREQUEST()
BOOTREPLY()
Common value is: "HTYPE_ETHER()" (1) = ethernet
For most NIC's, the MAC address has 6 bytes.
This field is incremented by each encountered DHCP relay agent.
This field should be a random value set by the DHCP client.
0x8000 = Broadcast reply requested.
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.
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.
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.
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.
Value 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.
Default value is 1, valid DHCP cookie.
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.
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()".
$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"));
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 "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"));
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()".
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());
This section describes supported option types (cf. RFC 2132).
For unsupported data types, please use "getOptionRaw()" and "addOptionRaw" to manipulate binary format directly.
Option code for 'dhcp message' format:
(053) DHO_DHCP_MESSAGE_TYPE
Example:
$pac->addOptionValue(DHO_DHCP_MESSAGE_TYPE(), DHCPINFORM());
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");
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");
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");
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");
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);
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");
If the packet is malformed, a fatal error is produced.
These are simple never failing versions of inet_ntoa and inet_aton.
These methods are provided for performance tuning only. They give access to internal data representation , thus avoiding unnecessary type conversion.
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.
Dean Hamstead <djzort@cpan.org> Previously Stephan Hadinger <shadinger@cpan.org>. Original version by F. van Dun.
See <https://rt.cpan.org/Dist/Display.html?Queue=Net-DHCP>
Many young people like to use Github, so by all means send me pull requests at
https://github.com/djzort/Net-DHCP
This is free software. It can be distributed and/or modified under the same terms as Perl itself.
Net::DHCP::Options, Net::DHCP::Constants.
| 2022-11-19 | perl v5.36.0 |