=begin
 Copyright(c) 2001,2003 arton, under GPL2.
 
 1.0.1 fix timeout value rounding problem and add checking host address.
       These fixes were formed by Winfried, thanks. 

 1.0.2 fix adress fetch problem when the host without reverse lookup records.
       This fix was contributed by Daniel J. Bell, thanks Daniel.

== SYNOPSIS
 require 'icmpping'
 result = ICMPPing.ping hostname [, timeout(millisecs) [, packetsize(<1024)]]

== Return Value

 -1 : Any Socket Error
 -2 : Timeout
 >=0: round trip time (in milliseconds)

== Testing Platforms

 Windows2000 (must be Administrator)
 Linux (Vine2.1) (must be root)
 Windows98SE

=end

require 'socket'
require 'timeout'

module ICMPPing
  DEF_PACKET_SIZE = 64
  MAX_PACKET_SIZE = 1024
 private
  def ping(*args) ICMPPing.ping(*args) end
end

class << ICMPPing

  IPPROTO_ICMP = 1

  ICMP_ECHO = 8
  ICMP_ECHOREPLY = 0

  def inetaddr(host)
    dest = ''
    TCPSocket.getaddress(host).split(/\./).each do |byte| 
      dest += byte.to_i.chr
    end
    dest
  end

  def ping(host, timeout = 1000, dlen = self::DEF_PACKET_SIZE)

    return -3 if dlen > self::MAX_PACKET_SIZE
    dest = inetaddr(host)
    begin
      hp = [Socket::AF_INET, 0, dest, 0, 0]
    rescue
      $stderr.printf($!.message + "\n") if $VERBOSE
      return -1
    end

    s = Socket.new(Socket::AF_INET, Socket::SOCK_RAW, IPPROTO_ICMP)

    start = tick
    id = $$ & 0xffff
    icmph = [ ICMP_ECHO, 0, 0, id, 0, start.to_i & 0xffffffff, nil ]
    icmph[6] = "E" * dlen
    dat = icmph.pack("C2n3Na*")
    cksum = checksum(((dat.length & 1) ? (dat + "\0") : dat).unpack("n*"))
    dat[2], dat[3] = cksum >> 8, cksum & 0xff
    begin
      s.send dat, 0, hp.pack("v2a*N2")
      timeout(timeout / 1000.0) do
        while true
          rdat = s.recvfrom(self::MAX_PACKET_SIZE + 500)
          rhost = rdat[1].unpack("v2a4")[2]
          icmpdat = rdat[0].slice((rdat[0][0] & 0x0f) * 4..-1)
          resp = icmpdat.unpack("C2n3N")
          next if resp[0] != ICMP_ECHOREPLY || resp[3] != id || dest != rhost
          break
        end
      end
    rescue TimeoutError
      $stderr.printf($!.message + "\n") if $VERBOSE
      return -2
    rescue
      $stderr.printf($!.message + "\n") if $VERBOSE
      return -1
    end

    tick - start
  end

 private
  begin
    require 'Win32API'
    GetTickCount = Win32API.new("kernel32", "GetTickCount", ['V'], 'L')
    def tick
      GetTickCount.call
    end
  rescue LoadError
    def tick
      Time.now.to_f * 1000
    end
  end

  def checksum(n)
    ck = 0
    n.each do |v|
      ck += v
    end
    ck = (ck >> 16) + (ck & 0xffff)
    ck += ck >> 16
    ~ck
  end
end

if $0 == __FILE__
  if ARGV.size <= 0
    print "usage: ping.rb host\n"
    exit 1
  else
    rd = ICMPPing.ping(ARGV[0])
    exit(rd) if rd < 0
    print "#{ICMPPing::DEF_PACKET_SIZE}bytes to #{ARGV[0]} time=#{rd}msec\n"
  end
end