301 lines
10 KiB
Ruby
301 lines
10 KiB
Ruby
require 'netlink/constants'
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require 'ipaddr'
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module Netlink
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EMPTY_STRING = "".freeze #:nodoc:
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EMPTY_ARRAY = [].freeze #:nodoc:
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# This is the base class from which all Netlink messages are derived.
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# To define a new Netlink message, make a subclass and then call the
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# "field" metaprogramming method to define the parts of the message, in
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# order. The "code" metaprogramming method defines which incoming message
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# types are to be built using this structure.
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#
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# You can then instantiate the message by calling 'new' as usual. It is
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# usually most convenient to pass in a hash of values when creating a message.
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#
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# class Foo < Message
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# code 10, 11, 12
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# field :foo, :char, :default=>255
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# field :bar, :long
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# end
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# msg = Foo.new(:bar => 123) # or Foo.new("bar" => 123)
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# msg.bar = 456
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# msg2 = Foo.new(:qux => 999) # error: no method "qux="
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# msg2 = Foo.new(msg) # cloning an existing message
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#
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# Use RtattrMessage instead for messages which are followed by variable rtattrs.
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class Message
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TYPE_INFO = {} #:nodoc
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# Define a new type for use with field and rtattr. You supply the
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# symbolic name for the type, and a set of options. field supports only:
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# :pattern => "str" # format string for Array#pack / String#unpack
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# :default => val # default (if not 0)
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# rtattr optionally also supports:
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# :pack => lambda # code to convert value to binary string
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# :unpack => lambda # code to convert binary string to value
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def self.define_type(name, opt)
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TYPE_INFO[name] = opt
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end
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define_type :uchar, :pattern => "C"
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define_type :uint16, :pattern => "S"
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define_type :uint32, :pattern => "L"
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define_type :char, :pattern => "c"
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define_type :int16, :pattern => "s"
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define_type :int32, :pattern => "l"
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define_type :ushort, :pattern => "S_"
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define_type :uint, :pattern => "I"
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define_type :ulong, :pattern => "L_"
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define_type :short, :pattern => "s_"
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define_type :int, :pattern => "i"
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define_type :long, :pattern => "l_"
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define_type :binary, :pattern => "a*", :default => EMPTY_STRING
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define_type :cstring, :pattern => "Z*", :default => EMPTY_STRING
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# L2 addresses are presented as ASCII hex. You may optionally include
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# colons, hyphens or dots.
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# Link.new(:address => "00:11:22:33:44:55") # this is OK
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define_type :l2addr,
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:pack => lambda { |val,obj| [val.delete(":-.")].pack("H*") },
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:unpack => lambda { |val,obj| val.unpack("H*").first }
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# L3 addresses are presented as IPAddr objects where possible. When
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# setting an address, you may provide an IPAddr object, an IP in readable
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# string form, or an integer. All of the following are acceptable:
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# Addr.new(:family=>Socket::AF_INET, :address=>IPAddr.new("1.2.3.4"))
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# Addr.new(:family=>Socket::AF_INET, :address=>"1.2.3.4")
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# Addr.new(:family=>Socket::AF_INET, :address=>0x01020304)
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# Furthermore, the 'family' will be set automatically if it is unset
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# at the time the message is encoded:
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# Addr.new(:address=>IPAddr.new("1.2.3.4")).to_s # ok
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# Addr.new(:address=>"1.2.3.4").to_s # ok
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# Addr.new(:address=>0x01020304).to_s # error, unknown family
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# Addr.new(:address=>"1.2.3.4", :local=>"::1").to_s # error, mismatched families
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define_type :l3addr,
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:pack => lambda { |val,obj|
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case obj.family
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when Socket::AF_INET, Socket::AF_INET6
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ip = case val
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when IPAddr
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val
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when Integer
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IPAddr.new(val, obj.family)
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else
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IPAddr.new(val)
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end
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raise "Mismatched address family" unless ip.family == obj.family
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ip.hton
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when nil, Socket::AF_UNSPEC
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ip = case val
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when IPAddr
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val
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when Integer
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raise "Missing address family"
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else
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IPAddr.new(val)
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end
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obj.family = ip.family
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ip.hton
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else
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raise "Mismatched address family" if val.is_a?(IPAddr)
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val
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end
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},
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:unpack => lambda { |val,obj|
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case obj.family
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when Socket::AF_INET, Socket::AF_INET6
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IPAddr.new_ntoh(val)
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else
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val
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end
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}
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def initialize(h=nil)
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if h.instance_of?(self.class)
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@attrs = h.to_hash.dup
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else
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@attrs = self.class::DEFAULTS.dup
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h.each { |k,v| self[k] = v } if h
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end
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end
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def to_hash
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@attrs
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end
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def each(&blk)
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@attrs.each(&blk)
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end
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# Set a field by name. Can use either symbol or string as key.
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def []=(k,v)
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send "#{k}=", v
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end
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# Retrieve a field by name. Must use symbol as key.
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def [](k)
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@attrs[k]
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end
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def self.inherited(subclass) #:nodoc:
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subclass.const_set(:FIELDS, [])
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subclass.const_set(:FORMAT, "")
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subclass.const_set(:DEFAULTS, {})
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end
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# Map of numeric message type code => message class
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CODE_TO_MESSAGE = {}
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# Define which message type code(s) to build using this structure
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def self.code(*codes)
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codes.each { |code| CODE_TO_MESSAGE[code] = self }
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end
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# Define a field for this message, which creates accessor methods and
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# sets up data required to pack and unpack the structure.
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# field :foo, :uchar
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# field :foo, :uchar, :default=>0xff # use this default value
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def self.field(name, type, opt={})
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info = TYPE_INFO[type]
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self::FIELDS << name
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self::FORMAT << info[:pattern]
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self::DEFAULTS[name] = opt.fetch(:default) { info.fetch(:default, 0) }
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define_method name do
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@attrs.fetch name
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end
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define_method "#{name}=" do |val|
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@attrs.store name, val
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end
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end
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# Returns the packed binary representation of this message (without
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# header, and not padded to NLMSG_ALIGNTO bytes)
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def to_s
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self.class::FIELDS.map { |key| self[key] }.pack(self.class::FORMAT)
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end
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def inspect
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"#<#{self.class} #{@attrs.inspect}>"
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end
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# Convert a binary representation of this message into an object instance
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def self.parse(data)
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res = new
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data.unpack(self::FORMAT).zip(self::FIELDS).each do |val, key|
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res[key] = val
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end
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res
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end
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NLMSG_ALIGNTO_1 = NLMSG_ALIGNTO-1 #:nodoc:
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NLMSG_ALIGNTO_1_MASK = ~NLMSG_ALIGNTO_1 #:nodoc:
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# Round up a length to a multiple of NLMSG_ALIGNTO bytes
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def self.align(n)
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(n + NLMSG_ALIGNTO_1) & NLMSG_ALIGNTO_1_MASK
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end
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PADDING = ("\000" * NLMSG_ALIGNTO).freeze #:nodoc:
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# Pad a string up to a multiple of NLMSG_ALIGNTO bytes. Returns str.
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def self.pad(str)
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str << PADDING[0, align(str.bytesize) - str.bytesize]
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end
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end
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# Extends Message to support variable Rtattr attributes. Use 'field'
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# to define the fixed parts of the message, and 'rtattr' to define the
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# permitted rtattrs. We assume that any particular rtattr is not repeated,
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# so we store them in the same underlying hash and create simple accessors
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# for them.
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class RtattrMessage < Message
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RTATTR_PACK = "S_S_".freeze #:nodoc:
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RTATTR_SIZE = [0,0].pack(RTATTR_PACK).bytesize #:nodoc:
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def self.inherited(subclass) #:nodoc:
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super
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subclass.const_set(:RTATTRS, {})
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end
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# Define an rtattr. You need to provide the code, and optionally the
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# type (if not provided, it will just be returned as a raw binary string)
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# rtattr :foo, 12
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# rtattr :foo, 12, :uint
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def self.rtattr(name, code, type=nil, opt={})
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info = TYPE_INFO[type]
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self::RTATTRS[code] = [name, info]
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define_method name do
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@attrs[name] # rtattrs are optional, non-existent returns nil
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end
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define_method "#{name}=" do |val|
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@attrs.store name, val
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end
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end
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# Return the byte offset to the first rtattr
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def self.attr_offset
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@attr_offset ||= Message.align(new.to_s.bytesize)
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end
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# Returns the packed binary representation of this message.
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# The main message is processed *after* the rtattrs; this is so that
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# the address family can be set automatically while processing any
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# optional l3 address rtattrs.
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def to_s
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data = ""
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self.class::RTATTRS.each do |code, (name, info)|
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if val = @attrs[name]
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Message.pad(data) # assume NLMSG_ALIGNTO == NLA_ALIGNTO
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if pack = info[:pack]
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val = pack[val,self]
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elsif pattern = info[:pattern]
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val = Array(val).pack(pattern)
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end
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data << [val.bytesize+RTATTR_SIZE, code].pack(RTATTR_PACK) << val
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end
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end
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data.empty? ? super : Message.pad(super) + data
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end
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# Convert a binary representation of this message into an object instance.
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# The main message is processed *before* the rtattrs, so that the
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# address family is available for l3 address rtattrs.
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def self.parse(data)
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res = super
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attrs = res.to_hash
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unpack_rtattr(data, attr_offset) do |code, val|
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name, info = self::RTATTRS[code]
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if name
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if !info
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# skip
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elsif unpack = info[:unpack]
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val = unpack[val,res]
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elsif pattern = info[:pattern]
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val = val.unpack(pattern).first
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end
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warn "Duplicate attribute #{name} (#{code}): #{attrs[name].inspect} -> #{val.inspect}" if attrs[name]
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attrs[name] = val
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else
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warn "Unknown attribute #{code}, value #{val.inspect}"
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attrs[code] = val
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end
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end
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res
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end
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# Unpack a string containing a sequence of rtattrs, yielding each in turn.
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def self.unpack_rtattr(data, ptr=0) #:nodoc:
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while ptr < data.bytesize
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raise "Truncated rtattr header!" if ptr + RTATTR_SIZE > data.bytesize
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len, code = data[ptr, RTATTR_SIZE].unpack(RTATTR_PACK)
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raise "Truncated rtattr body!" if ptr + len > data.bytesize
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raise "Invalid rtattr len!" if len < RTATTR_SIZE
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yield code, data[ptr+RTATTR_SIZE, len-RTATTR_SIZE]
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ptr = Message.align(ptr + len) # assume NLMSG_ALIGNTO == NLA_ALIGNTO
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end
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end
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end
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end
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