Class: Xlat::Protocols::Ip

Inherits:
Object
  • Object
show all
Defined in:
lib/xlat/protocols/ip.rb,
lib/xlat/protocols/ip/ipv4.rb,
lib/xlat/protocols/ip/ipv6.rb

Defined Under Namespace

Modules: Ipv4, Ipv6

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(icmp_payload: false) ⇒ Ip

Returns a new instance of Ip.



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# File 'lib/xlat/protocols/ip.rb', line 43

def initialize(icmp_payload: false)
  @icmp_payload = icmp_payload
  @_tcp = Tcp.new(self, icmp_payload:)
  @_udp = Udp.new(self, icmp_payload:)
end

Instance Attribute Details

#bytes ⇒ Object

IO::Buffer containing L3 header



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# File 'lib/xlat/protocols/ip.rb', line 29

def bytes
  @bytes
end

#bytes_length ⇒ Object

Length of L3 datagram within ‘bytes`



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# File 'lib/xlat/protocols/ip.rb', line 31

def bytes_length
  @bytes_length
end

#bytes_offset ⇒ Object

Offset where L3 header begins within ‘bytes`



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# File 'lib/xlat/protocols/ip.rb', line 30

def bytes_offset
  @bytes_offset
end

#cs_delta ⇒ Object

Accumulated changes to be applied to L4 checksum



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# File 'lib/xlat/protocols/ip.rb', line 39

def cs_delta
  @cs_delta
end

#l4 ⇒ Object

Returns the value of attribute l4.



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# File 'lib/xlat/protocols/ip.rb', line 35

def l4
  @l4
end

#l4_bytes ⇒ Object

IO::Buffer containing L4 packet



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# File 'lib/xlat/protocols/ip.rb', line 36

def l4_bytes
  @l4_bytes
end

#l4_bytes_length ⇒ Object

Length of L4 datagram within ‘l4_bytes`, possibly truncated



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# File 'lib/xlat/protocols/ip.rb', line 38

def l4_bytes_length
  @l4_bytes_length
end

#l4_bytes_offset ⇒ Object

Offset where L4 header begins within ‘l4_bytes`



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# File 'lib/xlat/protocols/ip.rb', line 37

def l4_bytes_offset
  @l4_bytes_offset
end

#l4_length ⇒ Object

Length of L4 packet, as specified in L3 header



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# File 'lib/xlat/protocols/ip.rb', line 34

def l4_length
  @l4_length
end

#l4_start ⇒ Object

L3 header length



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# File 'lib/xlat/protocols/ip.rb', line 33

def l4_start
  @l4_start
end

#proto ⇒ Object

L4 protocol ID



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# File 'lib/xlat/protocols/ip.rb', line 32

def proto
  @proto
end

#version ⇒ Object (readonly)

Returns the value of attribute version.



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# File 'lib/xlat/protocols/ip.rb', line 41

def version
  @version
end

Class Method Details

.addr_to_s(addr) ⇒ Object 



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# File 'lib/xlat/protocols/ip.rb', line 190

def self.addr_to_s(addr)
  case addr.length
  when 4
    addr.unpack('C4').join('.')
  when 16
    addr.unpack('n8').map { |f| format '%x', f }.join(':').gsub(/(:0)+(?=:)/, ':')
  else
    raise "unexpected address length of #{addr.length}"
  end
end

.checksum(bytes, from = nil, len = nil) ⇒ Object 



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# File 'lib/xlat/protocols/ip.rb', line 150

def self.checksum(bytes, from = nil, len = nil)
  from = 0 if from.nil?
  len = bytes.size - from if len.nil?
  to = from + len - 1

  sum = Common.sum16be(bytes.slice(from, len))
  sum += bytes.get_value(:U8, to) * 256 if len.odd?
  sum = (sum & 0xffff) + (sum >> 16) while sum > 65535
  ~sum & 0xffff
end

.checksum_adjust(checksum, delta) ⇒ Object

this function assumes 0 <= sum <= 65534



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# File 'lib/xlat/protocols/ip.rb', line 182

def self.checksum_adjust(checksum, delta)
  delta %= 65535

  mod65535 = 65534 - checksum
  mod65535 = (mod65535 + delta) % 65535
  65534 - mod65535
end

.checksum_list(buffers) ⇒ Object 



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# File 'lib/xlat/protocols/ip.rb', line 161

def self.checksum_list(buffers)
  sum = 0
  offset = 0
  buffers.each do |buf|
    if offset.odd?
      sum += buf.get_value(:U8, 0)
      buf = buf.slice(1)
      offset += 1
    end
    sum += Common.sum16be(buf)
    len = buf.size
    if len.odd?
      sum += buf.get_value(:U8, len - 1) << 8
    end
    offset += len
  end
  sum = (sum & 0xffff) + (sum >> 16) while sum > 65535
  ~sum & 0xffff
end

.parse(bytes) ⇒ Object 



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# File 'lib/xlat/protocols/ip.rb', line 49

def self.parse(bytes)
  new.parse(bytes:)
end

Instance Method Details

#apply_changes ⇒ Object 



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# File 'lib/xlat/protocols/ip.rb', line 143

def apply_changes
  cs_delta = @cs_delta
  @version.apply(@bytes, @bytes_offset, cs_delta, @icmp_payload)
  @l4&.apply(cs_delta)
  @cs_delta = 0
end

#convert_version!(version, new_header_bytes, cs_delta) ⇒ Ip

Convert this packet into different IP version using the supplied buffer as header.

Parameters:

  • version (Module) —

    New version

  • new_header_bytes (IO::Buffer) —

    Buffer to hold L3 header. The caller is responsible for populating the buffer with a proper content.

  • cs_delta (Integer) —

    Checksum delta in the pseudo header to be cancelled with the L4 checksum.

Returns:

  • (Ip) —

    self



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# File 'lib/xlat/protocols/ip.rb', line 129

def convert_version!(version, new_header_bytes, cs_delta)
  @bytes = new_header_bytes
  @bytes_offset = 0
  @bytes_length = new_header_bytes.size
  @version = version
  @l4_start = new_header_bytes.size
  @cs_delta += cs_delta
  self
end

#parse(bytes:, bytes_offset: 0, bytes_length: bytes.size - bytes_offset, l4_bytes: nil, l4_bytes_offset: nil) ⇒ Object 



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# File 'lib/xlat/protocols/ip.rb', line 53

def parse(bytes:, bytes_offset: 0, bytes_length: bytes.size - bytes_offset, l4_bytes: nil, l4_bytes_offset: nil)
  @bytes = bytes
  @bytes_offset = bytes_offset
  @bytes_length = bytes_length
  @proto = nil
  @version = nil
  @l4_start = nil
  @l4_length = nil
  @l4 = nil
  @l4_bytes = l4_bytes
  @l4_bytes_offset = l4_bytes_offset
  @l4_bytes_length = nil
  @cs_delta = 0

  # mimimum size for IPv4
  return nil if bytes_length < 20

  b0 = bytes.get_value(:U8, bytes_offset)
  case b0 >> 4
  when 4
    @version = Ipv4
  when 6
    @version = Ipv6
  else
    return nil
  end

  return nil unless @version.parse(self, b0)

  case @proto
  when Protocols::Udp::PROTOCOL_ID
    @l4 = @_udp.parse
  when Protocols::Tcp::PROTOCOL_ID
    @l4 = @_tcp.parse
  when @version.icmp_protocol_id
    @l4 = Protocols::Icmp.parse(self)
  end

  self
end

#set_l4_region(start, length) ⇒ true, false

Returns Whether the given range is valid.

Parameters:

  • start (Integer) —

    Length of L3 header in octets

  • length (Integer) —

    Length of L4 datagram in octets, as specified in L3 header

Returns:

  • (true, false) —

    Whether the given range is valid



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# File 'lib/xlat/protocols/ip.rb', line 97

def set_l4_region(start, length)
  @l4_start = start
  @l4_length = length

  unless @l4_bytes
    @l4_bytes = @bytes
    @l4_bytes_offset = @bytes_offset + start
    @l4_bytes_length = @bytes_length - start
  end

  if @l4_bytes_length < length
    if @icmp_payload
      # allow truncation in ICMP payload
      length = @l4_bytes_length
      return false if length < 0
    else
      return false
    end
  end

  @l4_bytes_length = length

  true
end

#tuple ⇒ Object 



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# File 'lib/xlat/protocols/ip.rb', line 139

def tuple
  @version.tuple(@bytes, @bytes_offset)
end