#!/usr/local/bin/python
# 
# Copyright 2005 John-Mark Gurney
# All rights reserved.
# 
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions
# are met:
# 1. Redistributions of source code must retain the above copyright
#    notice, this list of conditions and the following disclaimer.
# 2. Redistributions in binary form must reproduce the above copyright
#    notice, this list of conditions and the following disclaimer in the
#    documentation and/or other materials provided with the distribution.
# 
# THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
# ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
# OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
# HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
# OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
# SUCH DAMAGE.
# 

import socket
import select

__all__ = [ 'divert' ]

IPPROTO_DIVERT = 258

class Divert:
	def __init__(self, port, block = True, bufsize = 2048):
		self.sock = socket.socket(socket.AF_INET, socket.SOCK_RAW,
		    IPPROTO_DIVERT)
		self.sock.bind(('127.0.0.1', port))
		self.block = block
		self.bufsize = bufsize
		self.sock.setblocking(block)

	def handlepkt(self, buf, addr):
		raise NotImplementedError

	def sendpkt(self, buf, addr = None):
		if addr != None:
			return self.sock.sendto(buf, addr)
		else:
			return self.sock.send(buf)

	def checkandhandle(self, timeout = None):
		args = [ [self.sock], [], [] ]
		if timeout != None:
			args.append(timeout)
		rd, foo, foo = apply(select.select, args)
		if rd:
			buf, addr = self.sock.recvfrom(self.bufsize)
			if buf:
				self.handlepkt(buf, addr)