#!/usr/bin/python

#
# Creative Commons Attribution License
# http://creativecommons.org/licenses/by/2.5/
#
# Trevor Strohman, 2006
#

import sys
import os
import socket
import threading
import time

class DNSFetch(threading.Thread):
  def __init__( self, host, queue, lock ):
    threading.Thread.__init__(self)
    self.host = host
    self.lock = lock
    self.queue = queue

  def run(self):
    try:
      (hostname, something, addr) = socket.gethostbyaddr( self.host )
      self.lock.acquire()
      self.queue.append(hostname)
      self.lock.release()
    except:
      self.lock.acquire()
      self.queue.append(self.host + ".unknown.ip")
      self.lock.release()
      pass

def trim_threads( threads ):
  while len(threads) > 20:
    dead = filter( lambda x: (x.isAlive() == 0), threads )
    for thread in dead:
      thread.join()
      threads.remove(thread)
    if len(threads) > 20:
      time.sleep(1)

def wait_threads( threads ):
  for t in threads:
    t.join()

def hostname( s ):
  one = s.rfind( "." )
  two = s.rfind( ".", 0, one-1 )
  if two >= 0:
    return s[two+1:]
  return s
  
f = None

if len(sys.argv) > 1:
	f = file(sys.argv[1])
else:
	f = sys.stdin

hosts = {}

for line in f:
  fields = line.split()
  ip = fields[0]
  if ':' in ip:
    ip = ip.split(':')[1]
  hosts[ ip ] = 1

hosts = list(hosts.keys())
hosts.sort()

lock = threading.Lock()
queue = []
threads = []

for host in hosts:
  print "finding ", host
  t = DNSFetch(host,queue,lock)
  t.start()
  threads.append(t)
  trim_threads( threads )

wait_threads( threads )

queue.sort()
domains = {}
for host in queue:
  hn = hostname(host)
  if hn not in domains:
    domains[hn] = []
  domains[hostname(host)].append(host)

domainKeys = list(domains.keys())
domainKeys.sort()

for key in domainKeys:
  print key
  d = domains[key]
  for line in d:
    print "\t", line