1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
|
# -*- coding: binary -*-
module PacketFu
# Implements flags for TCPHeader.
#
# ==== Header Definition
#
# Integer(1 bit) :urg
# Integer(1 bit) :ack
# Integer(1 bit) :psh
# Integer(1 bit) :rst
# Integer(1 bit) :syn
# Integer(1 bit) :fin
#
# Flags can typically be set by setting them either to 1 or 0, or to true or false.
class TcpFlags < Struct.new(:urg, :ack, :psh, :rst, :syn, :fin)
include StructFu
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
# Returns the TcpFlags as an integer.
# Also not a great candidate for to_s due to the short bitspace.
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
# Helper to determine if this flag is a 1 or a 0.
def zero_or_one(i=0)
if i == 0 || i == false || i == nil
0
else
1
end
end
# Setter for the Urgent flag.
def urg=(i); self[:urg] = zero_or_one(i); end
# Setter for the Acknowlege flag.
def ack=(i); self[:ack] = zero_or_one(i); end
# Setter for the Push flag.
def psh=(i); self[:psh] = zero_or_one(i); end
# Setter for the Reset flag.
def rst=(i); self[:rst] = zero_or_one(i); end
# Setter for the Synchronize flag.
def syn=(i); self[:syn] = zero_or_one(i); end
# Setter for the Finish flag.
def fin=(i); self[:fin] = zero_or_one(i); end
# Reads a string to populate the object.
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
end
end
|
