#! /usr/bin/env python
#
# socket_crash.py -- Demonstrate a bug in socketmodule.c: internal_select()
#
# Requires Python 2.3, since it introduced settimeout().
#
# You probably need to be root and do 'ulimit -n 4000' from your shell
# immediately before running this test so you get more than the default
# number of file descriptors (which is likely to be less or equal than
# FD_SETSIZE).
#
# On my machine it crashes at fd ~ 1200. Under real world conditions you
# get random crashes. If you strace it you will see corrupt arguments
# to select() way before:
#
# select(1096, [1026 1060 1063 1065 1066 1067 1068 1069 1071 1072 1073
#        1074 1083 1091 1094 1095], NULL, NULL, {0, 1000}) = ...
#

import os, socket

# Pre-allocate lots of file descriptors
fds=[ os.open('/dev/null', os.O_RDONLY) for i in range(1000) ]

while 1:
  # Give it a shot with a simple UDP socket
  s=socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
  s.bind(('', 0))
  print s.fileno()
  s.settimeout(0.001)
  try:
    s.recv(1)
  except socket.error:
    pass
  s.close()
  # What? No crash yet? So, up the ante!
  fds.append(os.open('/dev/null', os.O_RDONLY))