class PacketFu::TcpFlags

Implements flags for TCPHeader.

Header Definition

Fixnum (1 bit)  :urg
Fixnum (1 bit)  :ack
Fixnum (1 bit)  :psh
Fixnum (1 bit)  :rst
Fixnum (1 bit)  :syn
Fixnum (1 bit)  :fin

Flags can typically be set by setting them either to 1 or 0, or to true or false.

Public Class Methods

new(args={}) click to toggle source
Calls superclass method
# File lib/packetfu/protos/tcp/flags.rb, line 18
def initialize(args={})
  # This technique attemts to ensure that flags are always 0 (off)
  # or 1 (on). Statements like nil and false shouldn't be lurking in here.
  if args.nil? || args.size.zero?
    super( 0, 0, 0, 0, 0, 0)
  else
    super(
      (args[:urg] ? 1 : 0), 
      (args[:ack] ? 1 : 0), 
      (args[:psh] ? 1 : 0), 
      (args[:rst] ? 1 : 0), 
      (args[:syn] ? 1 : 0), 
      (args[:fin] ? 1 : 0)
    )
  end
end

Public Instance Methods

ack=(i) click to toggle source

Setter for the Acknowlege flag.

# File lib/packetfu/protos/tcp/flags.rb, line 54
def ack=(i); self[:ack] = zero_or_one(i); end
fin=(i) click to toggle source

Setter for the Finish flag.

# File lib/packetfu/protos/tcp/flags.rb, line 62
def fin=(i); self[:fin] = zero_or_one(i); end
psh=(i) click to toggle source

Setter for the Push flag.

# File lib/packetfu/protos/tcp/flags.rb, line 56
def psh=(i); self[:psh] = zero_or_one(i); end
read(str) click to toggle source

Reads a string to populate the object.

# File lib/packetfu/protos/tcp/flags.rb, line 65
def read(str)
  force_binary(str)
  return self if str.nil?
  if 1.respond_to? :ord
    byte = str[0].ord
  else
    byte = str[0]
  end
  self[:urg] = byte & 0b00100000 == 0b00100000 ? 1 : 0
  self[:ack] = byte & 0b00010000 == 0b00010000 ? 1 : 0
  self[:psh] = byte & 0b00001000 == 0b00001000 ? 1 : 0
  self[:rst] = byte & 0b00000100 == 0b00000100 ? 1 : 0
  self[:syn] = byte & 0b00000010 == 0b00000010 ? 1 : 0
  self[:fin] = byte & 0b00000001 == 0b00000001 ? 1 : 0
  self
end
rst=(i) click to toggle source

Setter for the Reset flag.

# File lib/packetfu/protos/tcp/flags.rb, line 58
def rst=(i); self[:rst] = zero_or_one(i); end
syn=(i) click to toggle source

Setter for the Synchronize flag.

# File lib/packetfu/protos/tcp/flags.rb, line 60
def syn=(i); self[:syn] = zero_or_one(i); end
to_i() click to toggle source

Returns the TcpFlags as an integer. Also not a great candidate for to_s due to the short bitspace.

# File lib/packetfu/protos/tcp/flags.rb, line 37
def to_i
  (urg.to_i << 5) + (ack.to_i << 4) + (psh.to_i << 3) + 
  (rst.to_i << 2) + (syn.to_i << 1) + fin.to_i
end
urg=(i) click to toggle source

Setter for the Urgent flag.

# File lib/packetfu/protos/tcp/flags.rb, line 52
def urg=(i); self[:urg] = zero_or_one(i); end
zero_or_one(i=0) click to toggle source

Helper to determine if this flag is a 1 or a 0.

# File lib/packetfu/protos/tcp/flags.rb, line 43
def zero_or_one(i=0)
  if i == 0 || i == false || i == nil
    0
  else
    1
  end
end