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#!/usr/bin/env python
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#
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# nfdcpd: A promiscuous, NFQUEUE-based DHCP server for virtual machine hosting
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# Copyright (c) 2010 GRNET SA
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#
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# This program is free software; you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation; either version 2 of the License, or
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# (at your option) any later version.
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#
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# This program is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License along
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# with this program; if not, write to the Free Software Foundation, Inc.,
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# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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#
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import os |
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import re |
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import glob |
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import logging |
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import logging.handlers |
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import subprocess |
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import daemon |
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import nfqueue |
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import pyinotify |
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import IPy |
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from select import select |
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from socket import AF_INET, AF_PACKET, AF_UNSPEC |
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from scapy.layers.l2 import Ether |
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from scapy.layers.inet import IP, UDP |
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from scapy.layers.dhcp import BOOTP, DHCP |
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from scapy.sendrecv import sendp |
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DEFAULT_PATH = "/var/run/ganeti-dhcpd"
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DEFAULT_NFQUEUE_NUM = 42
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DEFAULT_USER = "nobody"
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DEFAULT_LEASE_TIME = 604800 # 1 week |
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DEFAULT_RENEWAL_TIME = 600 # 10 min |
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LOG_FILENAME = "/var/log/nfdhcpd/nfdhcpd.log"
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SYSFS_NET = "/sys/class/net"
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MY_IP = "1.2.3.4"
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LOG_FORMAT = "%(asctime)-15s %(levelname)-6s %(message)s"
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DHCPDISCOVER = 1
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DHCPOFFER = 2
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DHCPREQUEST = 3
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DHCPDECLINE = 4
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DHCPACK = 5
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DHCPNAK = 6
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DHCPRELEASE = 7
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DHCPINFORM = 8
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DHCP_TYPES = { |
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DHCPDISCOVER: "DHCPDISCOVER",
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DHCPOFFER: "DHCPOFFER",
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DHCPREQUEST: "DHCPREQUEST",
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DHCPDECLINE: "DHCPDECLINE",
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DHCPACK: "DHCPACK",
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DHCPNAK: "DHCPNAK",
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DHCPRELEASE: "DHCPRELEASE",
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DHCPINFORM: "DHCPINFORM",
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} |
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DHCP_REQRESP = { |
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DHCPDISCOVER: DHCPOFFER, |
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DHCPREQUEST: DHCPACK, |
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DHCPINFORM: DHCPACK, |
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} |
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class DhcpBindingHandler(pyinotify.ProcessEvent): |
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def __init__(self, dhcp): |
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pyinotify.ProcessEvent.__init__(self)
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self.dhcp = dhcp
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def process_IN_DELETE(self, event): |
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self.dhcp.remove_iface(event.name)
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def process_IN_CLOSE_WRITE(self, event): |
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self.dhcp.add_iface(os.path.join(event.path, event.name))
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class DhcpBinding(object): |
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def __init__(self, mac=None, ips=None, link=None, hostname=None): |
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self.mac = mac
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self.ips = ips
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self.hostname = hostname
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self.link = link
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self.iface = None |
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@property
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def ip(self): |
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return self.ips[0] |
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def is_valid(self): |
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return self.mac is not None and self.ips is not None\ |
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and self.hostname is not None |
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class Subnet(object): |
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def __init__(self, net=None, gw=None, dev=None): |
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if isinstance(net, str): |
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self.net = IPy.IP(net)
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else:
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self.net = net
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self.gw = gw
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self.dev = dev
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@property
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def netmask(self): |
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return str(self.net.netmask()) |
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@property
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def broadcast(self): |
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return str(self.net.broadcast()) |
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class DhcpServer(object): |
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def __init__(self, data_path, queue_num): |
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self.data_path = data_path
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self.clients = {}
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self.subnets = {}
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self.ifaces = {}
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# Inotify setup
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self.wm = pyinotify.WatchManager()
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mask = pyinotify.EventsCodes.ALL_FLAGS["IN_DELETE"]
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mask |= pyinotify.EventsCodes.ALL_FLAGS["IN_CLOSE_WRITE"]
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handler = DhcpBindingHandler(self)
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self.notifier = pyinotify.Notifier(self.wm, handler) |
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self.wm.add_watch(self.data_path, mask, rec=True) |
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# NFQueue setup
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self.q = nfqueue.queue()
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self.q.set_callback(self.make_reply) |
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self.q.fast_open(queue_num, AF_INET)
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self.q.set_queue_maxlen(5000) |
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# This is mandatory for the queue to operate
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self.q.set_mode(nfqueue.NFQNL_COPY_PACKET)
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def build_config(self): |
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self.clients.clear()
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self.subnets.clear()
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for file in glob.glob(os.path.join(self.data_path, "*")): |
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self.add_iface(file) |
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def get_ifindex(self, iface): |
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""" Get the interface index from sysfs
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"""
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file = os.path.abspath(os.path.join(SYSFS_NET, iface, "ifindex"))
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if not file.startswith(SYSFS_NET): |
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return None |
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ifindex = None
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try:
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f = open(file, 'r') |
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ifindex = int(f.readline().strip())
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f.close() |
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except:
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pass
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return ifindex
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def get_iface_hw_addr(self, iface): |
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""" Get the interface hardware address from sysfs
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"""
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file = os.path.abspath(os.path.join(SYSFS_NET, iface, "address"))
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if not file.startswith(SYSFS_NET): |
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return None |
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addr = None
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try:
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f = open(file, 'r') |
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addr = f.readline().strip() |
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f.close() |
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except:
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pass
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return addr
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def parse_routing_table(self, table="main"): |
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""" Parse the given routing table to get connected route, gateway and
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default device.
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"""
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ipro = subprocess.Popen(["ip", "ro", "ls", "table", table], |
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stdout=subprocess.PIPE) |
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routes = ipro.stdout.readlines() |
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def_gw = None
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def_dev = None
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def_net = None
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for route in routes: |
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match = re.match(r'^default.*via ([^\s]+).*dev ([^\s]+)', route)
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if match:
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def_gw, def_dev = match.groups() |
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break
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for route in routes: |
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# Find the least-specific connected route
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try:
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def_net = re.match("^([^\\s]+) dev %s" %
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def_dev, route).groups()[0]
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def_net = IPy.IP(def_net) |
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except:
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pass
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return Subnet(net=def_net, gw=def_gw, dev=def_dev)
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def parse_binding_file(self, path): |
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""" Read a client configuration from a tap file
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"""
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try:
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iffile = open(path, 'r') |
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except:
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return (None, None, None, None) |
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mac = None
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ips = None
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link = None
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hostname = None
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for line in iffile: |
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if line.startswith("IP="): |
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ip = line.strip().split("=")[1] |
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ips = ip.split() |
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elif line.startswith("MAC="): |
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mac = line.strip().split("=")[1] |
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elif line.startswith("LINK="): |
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link = line.strip().split("=")[1] |
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elif line.startswith("HOSTNAME="): |
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hostname = line.strip().split("=")[1] |
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return DhcpBinding(mac=mac, ips=ips, link=link, hostname=hostname)
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def add_iface(self, path): |
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""" Add an interface to monitor
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"""
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iface = os.path.basename(path) |
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logging.debug("Updating configuration for %s" % iface)
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binding = self.parse_binding_file(path)
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ifindex = self.get_ifindex(iface)
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if ifindex is None: |
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logging.warn("Stale configuration for %s found" % iface)
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else:
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if binding.is_valid():
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binding.iface = iface |
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self.clients[binding.mac] = binding
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self.subnets[binding.link] = self.parse_routing_table( |
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binding.link) |
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logging.debug("Added client %s on %s" %
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(binding.hostname, iface)) |
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self.ifaces[ifindex] = iface
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def remove_iface(self, iface): |
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""" Cleanup clients on a removed interface
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"""
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for mac in self.clients.keys(): |
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if self.clients[mac].iface == iface: |
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del self.clients[mac] |
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for ifindex in self.ifaces.keys(): |
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if self.ifaces[ifindex] == iface: |
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del self.ifaces[ifindex] |
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logging.debug("Removed interface %s" % iface)
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def make_reply(self, i, payload): |
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""" Generate a reply to a BOOTP/DHCP request
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"""
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# Decode the response - NFQUEUE relays IP packets
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pkt = IP(payload.get_data()) |
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# Get the actual interface from the ifindex
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iface = self.ifaces[payload.get_indev()]
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# Signal the kernel that it shouldn't further process the packet
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payload.set_verdict(nfqueue.NF_DROP) |
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# Get the client MAC address
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resp = pkt.getlayer(BOOTP).copy() |
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hlen = resp.hlen |
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mac = resp.chaddr[:hlen].encode("hex")
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mac, _ = re.subn(r'([0-9a-fA-F]{2})', r'\1:', mac, hlen-1) |
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# Server responses are always BOOTREPLYs
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resp.op = "BOOTREPLY"
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del resp.payload
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try:
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binding = self.clients[mac]
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except KeyError: |
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logging.warn("Invalid client %s on %s" % (mac, iface))
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return
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if iface != binding.iface:
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logging.warn("Received spoofed DHCP request for %s from interface"
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" %s instead of %s" %
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(mac, iface, binding.iface)) |
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return
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resp = Ether(dst=mac, src=self.get_iface_hw_addr(iface))/\
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IP(src=MY_IP, dst=binding.ip)/\ |
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UDP(sport=pkt.dport, dport=pkt.sport)/resp |
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subnet = self.subnets[binding.link]
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if not DHCP in pkt: |
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logging.warn("Invalid request from %s on %s, no DHCP"
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" payload found" % (binding.mac, iface))
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return
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dhcp_options = [] |
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requested_addr = binding.ip |
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for opt in pkt[DHCP].options: |
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if type(opt) is tuple and opt[0] == "message-type": |
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req_type = opt[1]
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if type(opt) is tuple and opt[0] == "requested_addr": |
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requested_addr = opt[1]
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logging.info("%s from %s on %s" %
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(DHCP_TYPES.get(req_type, "UNKNOWN"), binding.mac, iface))
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if req_type == DHCPREQUEST and requested_addr != binding.ip: |
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resp_type = DHCPNAK |
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logging.info("Sending DHCPNAK to %s on %s: requested %s"
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" instead of %s" %
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(binding.mac, iface, requested_addr, binding.ip)) |
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elif req_type in (DHCPDISCOVER, DHCPREQUEST): |
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resp_type = DHCP_REQRESP[req_type] |
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resp.yiaddr = self.clients[mac].ip
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dhcp_options += [ |
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("hostname", binding.hostname),
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("domain", binding.hostname.split('.', 1)[-1]), |
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("router", subnet.gw),
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("name_server", "194.177.210.10"), |
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("name_server", "194.177.210.211"), |
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("broadcast_address", str(subnet.broadcast)), |
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("subnet_mask", str(subnet.netmask)), |
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("renewal_time", DEFAULT_RENEWAL_TIME),
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("lease_time", DEFAULT_LEASE_TIME),
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] |
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elif req_type == DHCPINFORM:
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resp_type = DHCP_REQRESP[req_type] |
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dhcp_options += [ |
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("hostname", binding.hostname),
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("domain", binding.hostname.split('.', 1)[-1]), |
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("name_server", "194.177.210.10"), |
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("name_server", "194.177.210.211"), |
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] |
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elif req_type == DHCPRELEASE:
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# Log and ignore
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logging.info("DHCPRELEASE from %s on %s" %
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(binding.mac, iface)) |
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return
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# Finally, always add the server identifier and end options
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dhcp_options += [ |
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("message-type", resp_type),
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("server_id", MY_IP),
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"end"
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] |
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resp /= DHCP(options=dhcp_options) |
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logging.info("%s to %s (%s) on %s" %
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(DHCP_TYPES[resp_type], mac, binding.ip, iface)) |
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sendp(resp, iface=iface, verbose=False)
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def serve(self): |
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""" Loop forever, serving DHCP requests
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"""
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self.build_config()
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iwfd = self.notifier._fd
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qfd = self.q.get_fd()
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while True: |
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rlist, _, xlist = select([iwfd, qfd], [], [], 1.0)
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# First check if there are any inotify (= configuration change)
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# events
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if iwfd in rlist: |
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self.notifier.read_events()
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self.notifier.process_events()
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rlist.remove(iwfd) |
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for fd in rlist: |
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self.q.process_pending()
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if __name__ == "__main__": |
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import optparse |
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from capng import * |
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from pwd import getpwnam, getpwuid |
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parser = optparse.OptionParser() |
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parser.add_option("-p", "--path", dest="data_path", |
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help="The location of the data files", metavar="DIR", |
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default=DEFAULT_PATH) |
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parser.add_option("-n", "--nfqueue-num", dest="queue_num", |
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help="The nfqueue to receive DHCP requests from",
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metavar="NUM", default=DEFAULT_NFQUEUE_NUM)
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parser.add_option("-u", "--user", dest="user", |
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help="An unprivileged user to run as" ,
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metavar="UID", default=DEFAULT_USER)
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parser.add_option("-d", "--debug", action="store_true", dest="debug", |
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help="Turn on debugging messages")
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parser.add_option("-f", "--foreground", action="store_false", dest="daemonize", |
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default=True, help="Do not daemonize, stay in the foreground") |
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opts, args = parser.parse_args() |
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if opts.daemonize:
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d = daemon.DaemonContext() |
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d.open() |
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pidfile = open("/var/run/nfdhcpd.pid", "w") |
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pidfile.write("%s" % os.getpid())
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pidfile.close() |
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logger = logging.getLogger() |
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if opts.debug:
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logger.setLevel(logging.DEBUG) |
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else:
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logger.setLevel(logging.INFO) |
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if opts.daemonize:
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handler = logging.handlers.RotatingFileHandler(LOG_FILENAME, |
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maxBytes=2097152)
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else:
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handler = logging.StreamHandler() |
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handler.setFormatter(logging.Formatter(LOG_FORMAT)) |
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logger.addHandler(handler) |
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logging.info("Starting up")
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dhcp = DhcpServer(opts.data_path, opts.queue_num) |
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# Drop all capabilities except CAP_NET_RAW and change uid
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try:
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uid = getpwuid(int(opts.user))
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except ValueError: |
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uid = getpwnam(opts.user) |
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logging.info("Setting capabilities and changing uid")
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logging.debug("User: %s, uid: %d, gid: %d" %
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(opts.user, uid.pw_uid, uid.pw_gid)) |
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capng_clear(CAPNG_SELECT_BOTH) |
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capng_update(CAPNG_ADD, CAPNG_EFFECTIVE|CAPNG_PERMITTED, CAP_NET_RAW) |
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capng_change_id(uid.pw_uid, uid.pw_gid, |
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CAPNG_DROP_SUPP_GRP | CAPNG_CLEAR_BOUNDING) |
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logging.info("Ready to serve requests")
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dhcp.serve() |
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# vim: set ts=4 sts=4 sw=4 et :
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