apt-avahi-discover.py

#!/usr/bin/python
#
# use avahi to find a _apt_proxy._tcp provider and return
# a http proxy string suitable for apt

import socket
from subprocess	import Popen, PIPE


def is_ipv6(a):
    return ':' in a


def get_proxy_host_port_from_avahi():
    service = '_apt_proxy._tcp'

    # Obtain all of the services addresses from avahi, pulling the IPv6
    # addresses to the top.
    addr4 = []
    addr6 = []
    p = Popen(['avahi-browse', '-kprt', service], stdout=PIPE)
    for line in p.stdout:
        if line.startswith('='):
            bits = line.split(';')
            if is_ipv6(bits[7]):
                addr6.append([bits[7], bits[8]])
            else:
                addr4.append([bits[7], bits[8]])

    # Run through the offered addresses and see if we we have a bound local
    # address for it.
    for (ip, port) in addr6 + addr4:
        try:
            res = socket.getaddrinfo(ip, port, 0, 0, 0, socket.AI_ADDRCONFIG)
            if res:
                return (ip, port)
        except socket.gaierror:
            pass
    # nothing found
    return None


if __name__ == "__main__":
    # Dump the approved address out in an appropriate format.
    address = get_proxy_host_port_from_avahi()
    if address:
        (ip, port) = address
        if is_ipv6(ip):
            print "http://[%s]:%s/" % (ip, port)
        else:
            print "http://%s:%s/" % (ip, port)

etc_apt_apt..conf.d_30autoproxy

Acquire::http::ProxyAutoDetect "/path/to/apt-avahi-discover.py";

etc_avahi_services_apt-cacher-ng.service

<?xml version="1.0" standalone='no'?>
<!DOCTYPE service-group SYSTEM "avahi-service.dtd">
<service-group>
	<name replace-wildcards="yes">apt-cacher-ng proxy on %h</name>
	<service protocol="ipv4">
		<type>_apt_proxy._tcp</type>
		<port>3142</port>
	</service>
</service-group>

etc_schroot_setup.d_51aptproxy

#!/bin/sh
# Copyright © 2013  Dmitrijs Ledkovs <xnox@debian.org>
#
# schroot is free software: you can redistribute it and/or modify it
# under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# schroot is distributed in the hope that it will be useful, but
# WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
# General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see
# <http://www.gnu.org/licenses/>.
#
#####################################################################

set -e

. "$SETUP_DATA_DIR/common-data"
. "$SETUP_DATA_DIR/common-functions"
. "$SETUP_DATA_DIR/common-config"

APT_AVAHI_DISCOVER=/usr/share/squid-deb-proxy-client/apt-avahi-discover

if [ $STAGE = "setup-start" ] || [ $STAGE = "setup-recover" ]; then
    if type apt-avahi-discover 1>/dev/null; then
        APT_AVAHI_DISCOVER=apt-avahi-discover
    fi
    APT_PROXY=`$APT_AVAHI_DISCOVER`
    if [ -n "$APT_PROXY" ]; then
        info "Setting apt-proxy to avahi proxy at ${APT_PROXY}"
        printf 'Acquire::http { Proxy "%s";};\n' ${APT_PROXY} > "${CHROOT_PATH}/etc/apt/apt.conf.d/30schrootautoproxy"
    fi
fi