vip_manager.py
#!/usr/bin/env python
# -*- coding: iso8859-1 -*-
#
# Copyright (c) 2004-2006 Stian Søiland, Magnus Nordseth
#
# Permission is hereby granted, free of charge, to any person obtaining a
# copy of this software and associated documentation files (the
# "Software"), to deal in the Software without restriction, including
# without limitation the rights to use, copy, modify, merge, publish,
# distribute, sublicense, and/or sell copies of the Software, and to
# permit persons to whom the Software is furnished to do so, subject to
# the following conditions:
#
# The above copyright notice and this permission notice shall be included
# in all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
# OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
# IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
# CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
# TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
# SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
#
# Authors: Stian Soiland <stian@soiland.no>
# Magnus Nordseth <magnus@nordseth.net>
# Lasse Karstensen <lkarsten@samfundet.no>
#
# License: MIT
#
"""Manages VIP interfaces according to keepalived.conf.
Parses keepalived.conf to find active VIP (virtual_server) addresses
that should be active for a real_server (RIP).
Activates current VIPs on dummy interface, and disactivates
no longer active IPs.
See http://soiland.no/software/vip_manager/ or README.txt for
documentation.
USAGE: vip_manager.py [-d] [real_ip]
-d Show debug messages
real_ip Manually set real_server IP
(default: resolve from hostname)
"""
__version__ = "0.2.2006-04-10"
(True, False) = (1==1, 0==1)
# Revision history
# ================
#
# 0.1-2004-05-04
# First release
#
# 0.2-2006-04-10
# Added support for Linux 2.6 by Lasse Karstensen
# Default keepalived.conf path is now /etc/keepalived/keepalived.conf
import re
import socket
import sys
import os
from sets import Set
from systemArgs import systemArgs, ErrorcodeException
# Which dummy device to add/remove IP addresses to
DUMMY="dummy0"
# Our keepalived-conf ready for parsing
CONF="/etc/keepalived/keepalived.conf"
# Whether to print debug
DEBUG = False
# Our own IP to match for as real_server
REAL_IP = None
class VipManagerException(Exception):
pass
def _message(args):
"""Stringify a list of arguments, join with space"""
args = [str(arg) for arg in args]
return " ".join(args)
def _debug(*args):
if not DEBUG:
return
"""Prints debug"""
print _message(args)
def _warning(*args):
"""Prints warning"""
print >>sys.stderr, _message(args)
def _error(errorcode, *args):
"""Prints error exits with errorcode"""
if __name__ == "__main__":
# Only abort if we're run as a program
_warning(*args)
_warning("Aborting.")
sys.exit(errorcode)
else:
raise VipManagerException, (errorcode, _message(args))
def get_all_servers(conf=None):
"""Reads keepalived.conf and finds defined virtual_servers and their
matching real_servers.
Returns a dictionary, the keys are virtual_server IPs, and
the values are sets of 0 or more real_server IPs.
"""
conf = conf or CONF
try:
config = open(conf)
except IOError, e:
_error(4, "Could not read config file", conf, e)
virtualservers = {}
realservers = None
line_nr = 0
for line in config.readlines():
line_nr += 1
vmatch = re.search(r"^\s*virtual_server\s+([\d.]+)", line)
if vmatch:
vserver = vmatch.group(1)
# Add new list to virtualservers if non-existing
realservers = virtualservers.setdefault(vserver, Set())
rmatch = re.search(r"^\s*real_server\s+([\d.]+)", line)
if rmatch:
rserver = rmatch.group(1)
if realservers is None:
_error(1, "Parse error: found real_server", rserver, "for",
"unknown virtual_server on line", line_nr)
realservers.add(rserver)
sanity_check(virtualservers)
return virtualservers
def sanity_check(virtualservers):
"""Make sure the virtualservers list seems reasonable"""
if not virtualservers:
_error(2, "No virtual servers defined, probably misconfiguration")
# Check if any of the virtual servers actually has a real_server
any_real = [realservers for realservers in
virtualservers.values() if realservers]
if not any_real:
_error(3, "No real servers defined, probably misconfiguration")
def get_my_virtualservers(real_ip=None, conf=None):
"""Gets a list over VIP addresses served by real_ip.
If real_ip is not supplied, current hostname is used
to resolve it.
conf may specify the path to keepalived.conf.
"""
virtualservers = get_all_servers(conf)
# get my real address
my_real = real_ip or REAL_IP
if not my_real:
try:
my_real = socket.gethostbyname(socket.getfqdn())
except socket.error, e:
_error(5, "Could not resolve real_server IP", e)
if not my_real[:1].isdigit():
# this might happen with /store/bin/python (!)
# (gethostbyname simply returns the same name)
_error(6, "Invalid IP, got", my_real)
my_servers = [vserv for (vserv, realservers) in virtualservers.items()
if my_real in realservers]
# my_servers.sort()
return Set(my_servers)
def get_current_interfaces(dummy=None):
"""Retrieves current IPs active for given/default dummy interface"""
dummy = dummy or DUMMY
try:
ip_output = systemArgs('ip', 'addr')
except ErrorcodeException, e:
_error(7, "Could not run 'ip addr', error", *e)
interfaces = Set()
for line in ip_output.split("\n"):
inetmatch = re.search(r"^\s+inet ([\d.]+)/32.*%s$" % dummy, line)
if inetmatch:
interfaces.add(inetmatch.group(1))
return interfaces
def update_interfaces(dummy=None, real_ip=None, conf=None):
"""Removes inactive IPs and adds new IPs to dummy interface"""
dummy = dummy or DUMMY
should_have = get_my_virtualservers(real_ip=real_ip, conf=conf)
has_already = get_current_interfaces(dummy)
# must_delete = filter(lambda x:x not in should_have, has_already)
# must_delete = [ip for ip in has_already if ip not in should_have]
# Using sets is a lot more sexy.... :)
must_delete = has_already - should_have
must_add = should_have - has_already
_debug("Deleting", must_delete)
for ip in must_delete:
try:
systemArgs('ip', 'addr', 'del', ip, 'dev', dummy)
except ErrorcodeException, e:
# The error code if 'ip addr del' says
# "RTNETLINK answers: Cannot assign requested address"
if e[0] == 2:
_warning("Ignoring already removed ip", ip)
else:
_error(10, "Could not remove", ip)
_debug("Adding", must_add)
for ip in must_add:
try:
systemArgs('ip', 'addr', 'add', ip, 'dev', dummy)
except ErrorcodeException, e:
# The error code if 'ip addr add' says
# "RTNETLINK answers: File exists"
if e[0] == 2:
_warning("Ignoring already added ip", ip)
else:
_error(11, "Could not add", ip)
if should_have:
# make interface hidden if we have any active IPs
# (if no IPv4-addresses are on interface, hide_interface()
# won't work)
hide_interface(dummy)
def activate_interface(dummy=None):
"""Turns the dummy interface 'up'"""
dummy = dummy or DUMMY
try:
systemArgs('ifconfig', dummy, 'up')
except ErrorcodeException, e:
_error(9, "Could not activate interface", dummy, *e)
def hide_interface(dummy=None):
"""Makes the dummy interface 'hidden' to avoid ARP responses and
related problems."""
dummy = dummy or DUMMY
try:
if os.uname()[2].startswith('2.4'):
open("/proc/sys/net/ipv4/conf/%s/hidden" % dummy, "w").write("1\n")
# This global setting is also needed
open("/proc/sys/net/ipv4/conf/all/hidden", "w").write("1\n")
else:
# Assume 2.6 or later
# Linux 2.6 does things slightly more verbose
open("/proc/sys/net/ipv4/conf/%s/arp_announce" % dummy, "w").write("2\n")
open("/proc/sys/net/ipv4/conf/%s/arp_ignore" % dummy, "w").write("1\n")
# This global setting is also needed
open("/proc/sys/net/ipv4/conf/all/arp_announce", "w").write("2\n")
open("/proc/sys/net/ipv4/conf/all/arp_ignore" , "w").write("1\n")
except IOError, e:
# Turning off interface since we can't hide it
try:
systemArgs('ifconfig', dummy, 'down')
except ErrorcodeException:
pass
_error(8, "Could not set interface", dummy, "hidden", *e)
def main():
activate_interface()
update_interfaces()
if __name__ == "__main__":
# This is dirty, but small code
args = sys.argv[1:]
if "-h" in args:
print __doc__
sys.exit(0)
if "-d" in args:
DEBUG=True
args.remove("-d")
if args:
REAL_IP = args[0]
main()
