Dean Hamstead > Net-DHCP-0.693 > Net::DHCP::Packet

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Module Version: 0.693   Source   Latest Release: Net-DHCP-0.695

NAME ^

Net::DHCP::Packet - Object methods to create a DHCP packet.

SYNOPSIS ^

   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);

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

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.

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