Module: Xlat::Protocols::Ip::Ipv6

Extended by:
Common
Defined in:
lib/xlat/protocols/ip/ipv6.rb

Constant Summary collapse

EXTENSIONS =

www.iana.org/assignments/ipv6-parameters/ipv6-parameters.xhtml#extension-header except Fragment (44), ESP (50), AH (51)

Ractor.make_shareable([0, 43, 60, 135, 139, 140, 253, 254].to_h { |id| [id, true] })

Class Method Summary collapse

Methods included from Common

sum16be

Class Method Details

.apply(bytes, offset, _cs_delta, icmp_payload) ⇒ Object 



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# File 'lib/xlat/protocols/ip/ipv6.rb', line 116

def self.apply(bytes, offset, _cs_delta, icmp_payload)
  # decrement hop limit
  unless icmp_payload
    hop_limit = bytes.get_value(:U8, offset + 7)
    if hop_limit > 0
      hop_limit -= 1
      bytes.set_value(:U8, offset + 7, hop_limit)
    end
  end

  # IPv6 has no checksum
end

.icmp_cs_delta(packet) ⇒ Object 



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# File 'lib/xlat/protocols/ip/ipv6.rb', line 51

def self.icmp_cs_delta(packet)
  upper_layer_packet_length = packet.l4_bytes.size - packet.l4_bytes_offset
  Common.sum16be(tuple) + upper_layer_packet_length + packet.proto
end

.icmp_protocol_id ⇒ Object 



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# File 'lib/xlat/protocols/ip/ipv6.rb', line 47

def self.icmp_protocol_id
  Icmp::Base::V6_PROTOCOL_ID
end

.new_icmp(packet, type) ⇒ Object 



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# File 'lib/xlat/protocols/ip/ipv6.rb', line 56

def self.new_icmp(packet, type)
  case type
  when Icmp::Echo::V6_TYPE_REQUEST
    Icmp::Echo.new(packet, true)
  when Icmp::Echo::V6_TYPE_REPLY
    Icmp::Echo.new(packet, true)
  when Icmp::Error::V6_TYPE_DEST_UNREACH, Icmp::Error::V6_TYPE_PACKET_TOO_BIG, Icmp::Error::V6_TYPE_TIME_EXCEEDED, Icmp::Error::V6_TYPE_PARAMETER_PROBLEM
    Icmp::Error.new(packet)
  else
    Icmp::Base.new(packet)
  end
end

.parse(packet, _b0) ⇒ Object 



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# File 'lib/xlat/protocols/ip/ipv6.rb', line 69

def self.parse(packet, _b0)
  bytes = packet.bytes
  bytes_length = packet.bytes_length
  offset = packet.bytes_offset

  return false if bytes_length < 40

  payload_length = bytes.get_value(:U16, offset + 4)
  proto = bytes.get_value(:U8, offset + 6)

  # [draft-ietf-6man-eh-limits-19] Section 4 suggests IPv6 nodes
  # to process at least 64 bytes long chain of EHs.
  extensions_length_limit = [payload_length, 64].min
  extensions_length = 0

  while EXTENSIONS[proto]
    extension_start = 40 + extensions_length
    return false if extension_start + 8 > bytes_length  # EH is at least 8 byte long

    proto = bytes.get_value(:U8, offset + extension_start)
    length = bytes.get_value(:U8, offset + extension_start + 1) * 8 + 8

    extensions_length += length
    return false if extensions_length > extensions_length_limit

    # TODO: Routing header
  end

  if proto == 51  # AH
    # AH has a non-standard EH format. It doesn't work with NAT anyway.
    return false
  end

  # We assume Fragment is at the last of EH chain.
  if proto == 44  # Fragment
    # TODO: handle fragmentation
    return false
  end

  # ESP is handled as L4 protocol

  return false unless packet.set_l4_region(40 + extensions_length, payload_length - extensions_length)
  packet.proto = proto

  true
end

.to_i ⇒ Object 



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# File 'lib/xlat/protocols/ip/ipv6.rb', line 39

def self.to_i
  6
end

.tuple(bytes, offset) ⇒ Object 



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# File 'lib/xlat/protocols/ip/ipv6.rb', line 43

def self.tuple(bytes, offset)
  bytes.slice(offset + 8, 32)
end