Module Racket::L3::Misc
In: lib/racket/l3/misc.rb  (CVS)

Miscelaneous L3 helper methods

Methods

Public Class methods

Calculate the checksum. 16 bit one‘s complement of the one‘s complement sum of all 16 bit words

[Source]

# File lib/racket/l3/misc.rb, line 144
    def Misc.checksum(data)
      num_shorts = data.length / 2
      checksum = 0
      count = data.length
      
      data.unpack("S#{num_shorts}").each { |x|
        checksum += x
        count -= 2
      }

      if (count == 1)
        checksum += data[data.length - 1]
      end

      checksum = (checksum >> 16) + (checksum & 0xffff)
      checksum = ~((checksum >> 16) + checksum) & 0xffff
      ([checksum].pack("S*")).unpack("n*")[0]
    end

Compress an IPv6 address Inspired by Daniele Bellucci and jacked from ipaddr

[Source]

# File lib/racket/l3/misc.rb, line 75
    def Misc.compressipv6(ipv6)
      ipv6.gsub!(/\b0{1,3}([\da-f]+)\b/i, '\1')
      loop do
        break if ipv6.sub!(/\A0:0:0:0:0:0:0:0\Z/, '::')
        break if ipv6.sub!(/\b0:0:0:0:0:0:0\b/, ':')
        break if ipv6.sub!(/\b0:0:0:0:0:0\b/, ':')
        break if ipv6.sub!(/\b0:0:0:0:0\b/, ':')
        break if ipv6.sub!(/\b0:0:0:0\b/, ':')
        break if ipv6.sub!(/\b0:0:0\b/, ':')
        break if ipv6.sub!(/\b0:0\b/, ':')
        break
      end

      ipv6.sub!(/:{3,}/, '::')

      if /\A::(ffff:)?([\da-f]{1,4}):([\da-f]{1,4})\Z/i =~ ipv6
        ipv6 = sprintf('::%s%d.%d.%d.%d', $1, $2.hex / 256, $2.hex % 256, $3.hex / 256, $3.hex % 256)
      end

      ipv6
    end

given a "dotted quad" representing an IPv4 address, return the integer representation

[Source]

# File lib/racket/l3/misc.rb, line 138
    def Misc.ipv42long(ip)
      IPAddr.new(ip).to_i
    end

given a string representing an IPv6 address, return the integer representation

[Source]

# File lib/racket/l3/misc.rb, line 103
    def Misc.ipv62long(ip)
      IPAddr.new(ip).to_i
    end

Compute link local address for a given mac address From Daniele Bellucci

[Source]

# File lib/racket/l3/misc.rb, line 50
    def Misc.linklocaladdr(mac)
      mac = mac.split(":")
      mac[0] = (mac[0].to_i(16) ^ (1 << 1)).to_s(16)
      ["fe80", "", mac[0,2].join, mac[2,2].join("ff:fe"), mac[4,2].join].join(":")
    end

given an IPv4 address packed as an integer return the friendly "dotted quad"

[Source]

# File lib/racket/l3/misc.rb, line 35
    def Misc.long2ipv4(long)
      quad = Array.new(4)
      quad[0] = (long >> 24) & 255
      quad[1] = (long >> 16) & 255
      quad[2] = (long >> 8 ) & 255
      quad[3] = long & 255
      quad.join(".")
    end

Given a long, convert it to an IPv6 address, optionally compressing the address returned

[Source]

# File lib/racket/l3/misc.rb, line 58
    def Misc.long2ipv6(long, compress=true)
      ipv6 = []
      ipv6[0] = long >> 112
      ipv6[1] = (long >> 96) & (0xFFFF)
      ipv6[2] = (long >> 80) & (0xFFFF)
      ipv6[3] = (long >> 64) & (0xFFFF)
      ipv6[4] = (long >> 48) & (0xFFFF)
      ipv6[5] = (long >> 32) & (0xFFFF)
      ipv6[6] = (long >> 16) & (0xFFFF)
      ipv6[7] = long & (0xFFFF)

      ipv6 = ipv6.map { |o| o.to_s(16) }.join(":")
      compress ? Misc.compressipv6(ipv6) : ipv6
    end

[Source]

# File lib/racket/l3/misc.rb, line 44
    def Misc.randomipv4
      Misc.long2ipv4(rand(2**32))
    end

[Source]

# File lib/racket/l3/misc.rb, line 97
    def Misc.randomipv6
      Misc.long2ipv6(rand(2**128))
    end

In addition to the regular multicast addresses, each unicast address has a special multicast address called its solicited-node address. This address is created through a special mapping from the device’s unicast address. Solicited-node addresses are used by the IPv6 Neighbor Discovery (ND) protocol to provide more efficient address resolution than the ARP technique used in IPv4. From Daniele Bellucci

[Source]

# File lib/racket/l3/misc.rb, line 114
    def Misc.soll_mcast_addr6(addr)
      h = addr.split(':')[-2, 2] 
      m = []
      m << 'ff'
      m << (h[0].to_i(16) & 0xff).to_s(16)
      m << ((h[1].to_i(16) & (0xff << 8)) >> 8).to_s(16)
      m << (h[1].to_i(16) & 0xff).to_s(16)
      'ff02::1:' + [m[0,2].join, m[2,2].join].join(':')
    end

[Source]

# File lib/racket/l3/misc.rb, line 125
    def Misc.soll_mcast_mac(addr)
      h = addr.split(':')[-2, 2] 
      m = []
      m << 'ff'
      m << (h[0].to_i(16) & 0xff).to_s(16)
      m << ((h[1].to_i(16) & (0xff << 8)) >> 8).to_s(16)
      m << (h[1].to_i(16) & 0xff).to_s(16)   
      '33:33:' + m.join(':') 
    end

[Validate]