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PacketFu::ICMPHeader

ICMPHeader is a complete ICMP struct, used in ICMPPacket. ICMP is typically used for network administration and connectivity testing.

For more on ICMP packets, see www.networksorcery.com/enp/protocol/icmp.htm

Header Definition

Int8    :icmp_type                        # Type
Int8    :icmp_code                        # Code
Int16   :icmp_sum    Default: calculated  # Checksum
String  :body

Public Class Methods

new(args={}) click to toggle source
# File lib/packetfu/protos/icmp/header.rb, line 18
def initialize(args={})
        super(
                Int8.new(args[:icmp_type]),
                Int8.new(args[:icmp_code]),
                Int16.new(args[:icmp_sum] || icmp_calc_sum),
                StructFu::String.new.read(args[:body])
        )
end

Public Instance Methods

icmp_calc_sum() click to toggle source

Calculates and sets the checksum for the object.

# File lib/packetfu/protos/icmp/header.rb, line 58
def icmp_calc_sum
        checksum = (icmp_type.to_i << 8)     + icmp_code.to_i
        chk_body = (body.to_s.size % 2 == 0 ? body.to_s : body.to_s + "\x00")
        if 1.respond_to? :ord
                chk_body.scan(/../).map { |x| (x[0].ord << 8) + x[1].ord }.each { |y| checksum += y }
        else
                chk_body.scan(/../).map { |x| (x[0] << 8) + x[1] }.each { |y| checksum += y }
        end
        checksum = checksum % 0xffff
        checksum = 0xffff - checksum
        checksum == 0 ? 0xffff : checksum
end
icmp_code() click to toggle source

Getter for the code.

# File lib/packetfu/protos/icmp/header.rb, line 50
def icmp_code; self[:icmp_code].to_i; end
icmp_code=(i) click to toggle source

Setter for the code.

# File lib/packetfu/protos/icmp/header.rb, line 48
def icmp_code=(i); typecast i; end
icmp_recalc(arg=:all) click to toggle source

Recalculates the calculatable fields for ICMP.

# File lib/packetfu/protos/icmp/header.rb, line 72
def icmp_recalc(arg=:all)
        # How silly is this, you can't intern a symbol in ruby 1.8.7pl72?
        # I'm this close to monkey patching Symbol so you can force it...
        arg = arg.intern if arg.respond_to? :intern
        case arg
        when :icmp_sum
                self.icmp_sum=icmp_calc_sum
        when :all
                self.icmp_sum=icmp_calc_sum
        else
                raise ArgumentError, "No such field `#{arg}'"
        end
end
icmp_sum() click to toggle source

Getter for the checksum.

# File lib/packetfu/protos/icmp/header.rb, line 55
def icmp_sum; self[:icmp_sum].to_i; end
icmp_sum=(i) click to toggle source

Setter for the checksum. Note, this is calculated automatically with icmp_calc_sum.

# File lib/packetfu/protos/icmp/header.rb, line 53
def icmp_sum=(i); typecast i; end
icmp_sum_readable() click to toggle source

Readability aliases

# File lib/packetfu/protos/icmp/header.rb, line 88
def icmp_sum_readable
        "0x%04x" % icmp_sum
end
icmp_type() click to toggle source

Getter for the type.

# File lib/packetfu/protos/icmp/header.rb, line 46
def icmp_type; self[:icmp_type].to_i; end
icmp_type=(i) click to toggle source

Setter for the type.

# File lib/packetfu/protos/icmp/header.rb, line 44
def icmp_type=(i); typecast i; end
read(str) click to toggle source

Reads a string to populate the object.

# File lib/packetfu/protos/icmp/header.rb, line 33
def read(str)
        force_binary(str)
        return self if str.nil?
        self[:icmp_type].read(str[0,1])
        self[:icmp_code].read(str[1,1])
        self[:icmp_sum].read(str[2,2])
        self[:body].read(str[4,str.size])
        self
end
to_s() click to toggle source

Returns the object in string form.

# File lib/packetfu/protos/icmp/header.rb, line 28
def to_s
        self.to_a.map {|x| x.to_s}.join
end

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