Class: PacketGen::Header::DHCP

Inherits:
Base show all
Defined in:
lib/packetgen/header/dhcp.rb,
lib/packetgen/header/dhcp.rb,
lib/packetgen/header/dhcp/option.rb,
lib/packetgen/header/dhcp/options.rb

Overview

Dynamic Host Configuration Protocol, RFC 2131

A DHCP header is quite simple. It is composed of:

In PacketGen, a DHCP header is always a secondary header after BOOTP one.

Create a DHCP header

# standalone
dhcp = PacketGen::Header::DHCP.new
# in a packet
pkt = PacketGen.gen('IP').add('BOOTP').add('DHCP')
# access to DHCP header
pkt.dhcp      # => PacketGen::Header::DHCP

Add options

Options may be added these ways:

dhcp = PacketGen::Header::DHCP.new
# Add a lease_time option
dhcp.options << { type: 'lease_time', value: 3600 }
# Add a domain option. Here, use integer type
dhcp.options << { type: 15, value: 'example.net'}
# Add an end option
dhcp.options << { type: 'end' }
# And finish with padding
dhcp.options << { type: 'pad' }

Author:

  • Sylvain Daubert

Since:

  • 2.2.0

Defined Under Namespace

Classes: End, Option, Options, Pad

Constant Summary collapse

DHCP_MAGIC =

DHCP magic value in BOOTP options

Since:

  • 2.2.0

0x63825363
DHCP_OPTIONS =

define DHCP Options. keys are option type, value are arrays containing option names as strings, and a hash passed to Option#initialize.

Since:

  • 2.7.0

{
  1  => ['subnet_mask', length: 4, v: IP::Addr],
  2  => ['time_zone'],
  3  => ['router', length: 4, v: IP::Addr],
  4  => ['time_server', length: 4, v: IP::Addr],
  5  => ['IEN_name_server', length: 4, v: IP::Addr],
  6  => ['name_server', length: 4, v: IP::Addr],
  7  => ['log_server', length: 4, v: IP::Addr],
  8  => ['cookie_server', length: 4, v: IP::Addr],
  9  => ['lpr_server', length: 4, v: IP::Addr],
  12 => ['hostname'],
  14 => ['dump_path'],
  15 => ['domain'],
  17 => ['root_disk_path'],
  23 => ['default_ttl'],
  24 => ['pmtu_timeout'],
  28 => ['broadcast_address', length: 4, v: IP::Addr],
  40 => ['NIS_domain'],
  41 => ['NIS_server', length: 4, v: IP::Addr],
  42 => ['NTP_server', length: 4, v: IP::Addr],
  43 => ['vendor_specific'],
  44 => ['NetBIOS_server', length: 4, v: IP::Addr],
  45 => ['NetBIOS_dist_server', length: 4, v: IP::Addr],
  50 => ['requested_addr', length: 4, v: IP::Addr],
  51 => ['lease_time', length: 4, v: Types::Int32, value: 43_200],
  53 => ['message-type', length: 1, v: Types::Int8],
  54 => ['server_id', length: 4, v: IP::Addr],
  55 => ['param_req_list'],
  56 => ['error_message'],
  57 => ['max_dhcp_size', length: 2, v: Types::Int16, value: 1_500],
  58 => ['renewal_time', length: 4, v: Types::Int32, value: 21_600],
  59 => ['rebinding_time', length: 4, v: Types::Int32, value: 37_800],
  60 => ['vendor_class_id'],
  61 => ['client_id'],
  64 => ['NISplus_domain'],
  65 => ['NISplus_server', length: 4, v: IP::Addr],
  69 => ['SMTP_server', length: 4, v: IP::Addr],
  70 => ['POP3_server', length: 4, v: IP::Addr],
  71 => ['NNTP_server', length: 4, v: IP::Addr],
  72 => ['WWW_server', length: 4, v: IP::Addr],
  73 => ['finger_server', length: 4, v: IP::Addr],
  74 => ['IRC_server', length: 4, v: IP::Addr]
}.freeze

Instance Attribute Summary collapse

Instance Method Summary collapse

Methods inherited from Base

bind, calculate_and_set_length, #header_id, inherited, #initialize, #ip_header, known_headers, #ll_header

Methods included from PacketGen::Headerable

#added_to_packet, included, #method_name, #packet, #packet=, #protocol_name, #read

Methods inherited from Types::Fields

#[], #[]=, #bits_on, define_bit_fields_on, define_field, define_field_after, define_field_before, #fields, fields, inherited, #initialize, #inspect, #offset_of, #optional?, #optional_fields, #present?, #read, remove_bit_fields_on, remove_field, #sz, #to_h, #to_s, update_field

Constructor Details

This class inherits a constructor from PacketGen::Header::Base

Instance Attribute Details

#magic ⇒ Integer

Returns:

  • (Integer) 


52
 
# File 'lib/packetgen/header/dhcp.rb', line 52

define_field :magic, Types::Int32, default: 0x63825563

#options ⇒ DHCP::Options

Returns:



55
 
# File 'lib/packetgen/header/dhcp.rb', line 55

define_field :options, DHCP::Options

Instance Method Details

#parse? ⇒ Boolean

differentiate from BOOTP by checking presence of DHCP magic

Returns:

  • (Boolean)

Since:

  • 2.2.0



59
60
61
 
# File 'lib/packetgen/header/dhcp.rb', line 59

def parse?
  self.magic == DHCP_MAGIC
end