sshuttle/src/client.py

import struct
import errno
import re
import signal
import time
import compat.ssubprocess as ssubprocess
import helpers
import os
import ssnet
import ssh
import ssyslog
import sys
from ssnet import SockWrapper, Handler, Proxy, Mux, MuxWrapper
from helpers import log, debug1, debug2, debug3, Fatal, islocal
from fcntl import ioctl
from ctypes import *

recvmsg = None
try:
    # try getting recvmsg from python
    import socket as pythonsocket
    getattr(pythonsocket.socket, "recvmsg")
    socket = pythonsocket
    recvmsg = "python"
except AttributeError:
    # try getting recvmsg from socket_ext library
    try:
        import socket_ext
        getattr(socket_ext.socket, "recvmsg")
        socket = socket_ext
        recvmsg = "socket_ext"
    except ImportError:
        import socket

_extra_fd = os.open('/dev/null', os.O_RDONLY)


def got_signal(signum, frame):
    log('exiting on signal %d\n' % signum)
    sys.exit(1)


_pidname = None
IP_TRANSPARENT = 19
IP_ORIGDSTADDR = 20
IP_RECVORIGDSTADDR = IP_ORIGDSTADDR
SOL_IPV6 = 41
IPV6_ORIGDSTADDR = 74
IPV6_RECVORIGDSTADDR = IPV6_ORIGDSTADDR


if recvmsg == "python":
    def recv_udp(listener, bufsize):
        debug3('Accept UDP python using recvmsg.\n')
        data, ancdata, msg_flags, srcip = listener.recvmsg(
            4096, socket.CMSG_SPACE(24))
        dstip = None
        family = None
        for cmsg_level, cmsg_type, cmsg_data in ancdata:
            if cmsg_level == socket.SOL_IP and cmsg_type == IP_ORIGDSTADDR:
                family, port = struct.unpack('=HH', cmsg_data[0:4])
                port = socket.htons(port)
                if family == socket.AF_INET:
                    start = 4
                    length = 4
                else:
                    raise Fatal("Unsupported socket type '%s'" % family)
                ip = socket.inet_ntop(family, cmsg_data[start:start + length])
                dstip = (ip, port)
                break
            elif cmsg_level == SOL_IPV6 and cmsg_type == IPV6_ORIGDSTADDR:
                family, port = struct.unpack('=HH', cmsg_data[0:4])
                port = socket.htons(port)
                if family == socket.AF_INET6:
                    start = 8
                    length = 16
                else:
                    raise Fatal("Unsupported socket type '%s'" % family)
                ip = socket.inet_ntop(family, cmsg_data[start:start + length])
                dstip = (ip, port)
                break
        return (srcip, dstip, data)
elif recvmsg == "socket_ext":
    def recv_udp(listener, bufsize):
        debug3('Accept UDP using socket_ext recvmsg.\n')
        srcip, data, adata, flags = listener.recvmsg(
            (bufsize,), socket.CMSG_SPACE(24))
        dstip = None
        family = None
        for a in adata:
            if a.cmsg_level == socket.SOL_IP and a.cmsg_type == IP_ORIGDSTADDR:
                family, port = struct.unpack('=HH', a.cmsg_data[0:4])
                port = socket.htons(port)
                if family == socket.AF_INET:
                    start = 4
                    length = 4
                else:
                    raise Fatal("Unsupported socket type '%s'" % family)
                ip = socket.inet_ntop(
                    family, a.cmsg_data[start:start + length])
                dstip = (ip, port)
                break
            elif a.cmsg_level == SOL_IPV6 and a.cmsg_type == IPV6_ORIGDSTADDR:
                family, port = struct.unpack('=HH', a.cmsg_data[0:4])
                port = socket.htons(port)
                if family == socket.AF_INET6:
                    start = 8
                    length = 16
                else:
                    raise Fatal("Unsupported socket type '%s'" % family)
                ip = socket.inet_ntop(
                    family, a.cmsg_data[start:start + length])
                dstip = (ip, port)
                break
        return (srcip, dstip, data[0])
else:
    def recv_udp(listener, bufsize):
        debug3('Accept UDP using recvfrom.\n')
        data, srcip = listener.recvfrom(bufsize)
        return (srcip, None, data)


def check_daemon(pidfile):
    global _pidname
    _pidname = os.path.abspath(pidfile)
    try:
        oldpid = open(_pidname).read(1024)
    except IOError, e:
        if e.errno == errno.ENOENT:
            return  # no pidfile, ok
        else:
            raise Fatal("can't read %s: %s" % (_pidname, e))
    if not oldpid:
        os.unlink(_pidname)
        return  # invalid pidfile, ok
    oldpid = int(oldpid.strip() or 0)
    if oldpid <= 0:
        os.unlink(_pidname)
        return  # invalid pidfile, ok
    try:
        os.kill(oldpid, 0)
    except OSError, e:
        if e.errno == errno.ESRCH:
            os.unlink(_pidname)
            return  # outdated pidfile, ok
        elif e.errno == errno.EPERM:
            pass
        else:
            raise
    raise Fatal("%s: sshuttle is already running (pid=%d)"
                % (_pidname, oldpid))


def daemonize():
    if os.fork():
        os._exit(0)
    os.setsid()
    if os.fork():
        os._exit(0)

    outfd = os.open(_pidname, os.O_WRONLY | os.O_CREAT | os.O_EXCL, 0666)
    try:
        os.write(outfd, '%d\n' % os.getpid())
    finally:
        os.close(outfd)
    os.chdir("/")

    # Normal exit when killed, or try/finally won't work and the pidfile won't
    # be deleted.
    signal.signal(signal.SIGTERM, got_signal)

    si = open('/dev/null', 'r+')
    os.dup2(si.fileno(), 0)
    os.dup2(si.fileno(), 1)
    si.close()

    ssyslog.stderr_to_syslog()


def daemon_cleanup():
    try:
        os.unlink(_pidname)
    except OSError, e:
        if e.errno == errno.ENOENT:
            pass
        else:
            raise


class pf_state_xport(Union):
    _fields_ = [("port", c_uint16),
                ("call_id", c_uint16),
                ("spi", c_uint32)]

class pf_addr(Structure):
    class _pfa(Union):
        _fields_ = [("v4",            c_uint32),      # struct in_addr
                    ("v6",            c_uint32 * 4),  # struct in6_addr
                    ("addr8",         c_uint8 * 16),
                    ("addr16",        c_uint16 * 8),
                    ("addr32",        c_uint32 * 4)]

    _fields_ = [("pfa",               _pfa)]
    _anonymous_ = ("pfa",)

class pfioc_natlook(Structure):
    _fields_ = [("saddr", pf_addr),
                ("daddr", pf_addr),
                ("rsaddr", pf_addr),
                ("rdaddr", pf_addr),
                ("sxport", pf_state_xport),
                ("dxport", pf_state_xport),
                ("rsxport", pf_state_xport),
                ("rdxport", pf_state_xport),
                ("af", c_uint8),                      # sa_family_t  
                ("proto", c_uint8),
                ("proto_variant", c_uint8),
                ("direction", c_uint8)]

DIOCNATLOOK = ((0x40000000L | 0x80000000L) | ((sizeof(pfioc_natlook) & 0x1fff) << 16) | ((ord('D')) << 8) | (23))
PF_OUT = 2

_pf_fd = None

def pf_dst(sock):
    global _pf_fd
    try:
        peer = sock.getpeername()
        proxy = sock.getsockname()

        pnl = pfioc_natlook()
        pnl.proto = socket.IPPROTO_TCP
        pnl.direction = PF_OUT
        if sock.family == socket.AF_INET:
            pnl.af = socket.AF_INET
            memmove(addressof(pnl.saddr), socket.inet_pton(socket.AF_INET, peer[0]), 4)
            pnl.sxport.port = socket.htons(peer[1])
            memmove(addressof(pnl.daddr), socket.inet_pton(socket.AF_INET, proxy[0]), 4)
            pnl.dxport.port = socket.htons(proxy[1])
        elif sock.family == socket.AF_INET6:
            pnl.af = socket.AF_INET6
            memmove(addressof(pnl.saddr), socket.inet_pton(socket.AF_INET6, peer[0]), 16)
            pnl.sxport.port = socket.htons(peer[1])
            memmove(addressof(pnl.daddr), socket.inet_pton(socket.AF_INET6, proxy[0]), 16)
            pnl.dxport.port = socket.htons(proxy[1])

        if _pf_fd == None:
            _pf_fd = open('/dev/pf', 'r')

        ioctl(_pf_fd, DIOCNATLOOK, (c_char * sizeof(pnl)).from_address(addressof(pnl)))

        if pnl.af == socket.AF_INET:
            ip = socket.inet_ntop(socket.AF_INET, (c_char * 4).from_address(addressof(pnl.rdaddr)))
        elif pnl.af == socket.AF_INET6:
            ip = socket.inet_ntop(socket.AF_INET6, (c_char * 16).from_address(addressof(pnl.rdaddr)))
        port = socket.ntohs(pnl.rdxport.port)
        return (ip, port)
    except IOError, e:
        return sock.getsockname()
        raise


def original_dst(sock):
    try:
        SO_ORIGINAL_DST = 80
        SOCKADDR_MIN = 16
        sockaddr_in = sock.getsockopt(socket.SOL_IP,
                                      SO_ORIGINAL_DST, SOCKADDR_MIN)
        (proto, port, a, b, c, d) = struct.unpack('!HHBBBB', sockaddr_in[:8])
        assert(socket.htons(proto) == socket.AF_INET)
        ip = '%d.%d.%d.%d' % (a, b, c, d)
        return (ip, port)
    except socket.error, e:
        if e.args[0] == errno.ENOPROTOOPT:
            return sock.getsockname()
        raise


class MultiListener:

    def __init__(self, type=socket.SOCK_STREAM, proto=0):
        self.v6 = socket.socket(socket.AF_INET6, type, proto)
        self.v4 = socket.socket(socket.AF_INET, type, proto)

    def setsockopt(self, level, optname, value):
        if self.v6:
            self.v6.setsockopt(level, optname, value)
        if self.v4:
            self.v4.setsockopt(level, optname, value)

    def add_handler(self, handlers, callback, method, mux):
        if self.v6:
            handlers.append(
                Handler(
                    [self.v6],
                    lambda: callback(self.v6, method, mux, handlers)))
        if self.v4:
            handlers.append(
                Handler(
                    [self.v4],
                    lambda: callback(self.v4, method, mux, handlers)))

    def listen(self, backlog):
        if self.v6:
            self.v6.listen(backlog)
        if self.v4:
            try:
                self.v4.listen(backlog)
            except socket.error, e:
                # on some systems v4 bind will fail if the v6 suceeded,
                # in this case the v6 socket will receive v4 too.
                if e.errno == errno.EADDRINUSE and self.v6:
                    self.v4 = None
                else:
                    raise e

    def bind(self, address_v6, address_v4):
        if address_v6 and self.v6:
            self.v6.bind(address_v6)
        else:
            self.v6 = None
        if address_v4 and self.v4:
            self.v4.bind(address_v4)
        else:
            self.v4 = None

    def print_listening(self, what):
        if self.v6:
            listenip = self.v6.getsockname()
            debug1('%s listening on %r.\n' % (what, listenip))
        if self.v4:
            listenip = self.v4.getsockname()
            debug1('%s listening on %r.\n' % (what, listenip))


class FirewallClient:

    def __init__(self, port_v6, port_v4, subnets_include, subnets_exclude,
                 dnsport_v6, dnsport_v4, method, udp):
        self.auto_nets = []
        self.subnets_include = subnets_include
        self.subnets_exclude = subnets_exclude
        argvbase = ([sys.argv[1], sys.argv[0], sys.argv[1]] +
                    ['-v'] * (helpers.verbose or 0) +
                    ['--firewall', str(port_v6), str(port_v4),
                     str(dnsport_v6), str(dnsport_v4),
                     method, str(int(udp))])
        if ssyslog._p:
            argvbase += ['--syslog']
        argv_tries = [
            ['sudo', '-p', '[local sudo] Password: '] + argvbase,
            ['su', '-c', ' '.join(argvbase)],
            argvbase
        ]

        # we can't use stdin/stdout=subprocess.PIPE here, as we normally would,
        # because stupid Linux 'su' requires that stdin be attached to a tty.
        # Instead, attach a *bidirectional* socket to its stdout, and use
        # that for talking in both directions.
        (s1, s2) = socket.socketpair()

        def setup():
            # run in the child process
            s2.close()
        e = None
        if os.getuid() == 0:
            argv_tries = argv_tries[-1:]  # last entry only
        for argv in argv_tries:
            try:
                if argv[0] == 'su':
                    sys.stderr.write('[local su] ')
                self.p = ssubprocess.Popen(argv, stdout=s1, preexec_fn=setup)
                e = None
                break
            except OSError, e:
                pass
        self.argv = argv
        s1.close()
        self.pfile = s2.makefile('wb+')
        if e:
            log('Spawning firewall manager: %r\n' % self.argv)
            raise Fatal(e)
        line = self.pfile.readline()
        self.check()
        if line[0:5] != 'READY':
            raise Fatal('%r expected READY, got %r' % (self.argv, line))
        self.method = line[6:-1]

    def check(self):
        rv = self.p.poll()
        if rv:
            raise Fatal('%r returned %d' % (self.argv, rv))

    def start(self):
        self.pfile.write('ROUTES\n')
        for (family, ip, width) in self.subnets_include + self.auto_nets:
            self.pfile.write('%d,%d,0,%s\n' % (family, width, ip))
        for (family, ip, width) in self.subnets_exclude:
            self.pfile.write('%d,%d,1,%s\n' % (family, width, ip))
        self.pfile.write('GO\n')
        self.pfile.flush()
        line = self.pfile.readline()
        self.check()
        if line != 'STARTED\n':
            raise Fatal('%r expected STARTED, got %r' % (self.argv, line))

    def sethostip(self, hostname, ip):
        assert(not re.search(r'[^-\w]', hostname))
        assert(not re.search(r'[^0-9.]', ip))
        self.pfile.write('HOST %s,%s\n' % (hostname, ip))
        self.pfile.flush()

    def done(self):
        self.pfile.close()
        rv = self.p.wait()
        if rv:
            raise Fatal('cleanup: %r returned %d' % (self.argv, rv))


dnsreqs = {}
udp_by_src = {}


def expire_connections(now, mux):
    for chan, timeout in dnsreqs.items():
        if timeout < now:
            debug3('expiring dnsreqs channel=%d\n' % chan)
            del mux.channels[chan]
            del dnsreqs[chan]
    debug3('Remaining DNS requests: %d\n' % len(dnsreqs))
    for peer, (chan, timeout) in udp_by_src.items():
        if timeout < now:
            debug3('expiring UDP channel channel=%d peer=%r\n' % (chan, peer))
            mux.send(chan, ssnet.CMD_UDP_CLOSE, '')
            del mux.channels[chan]
            del udp_by_src[peer]
    debug3('Remaining UDP channels: %d\n' % len(udp_by_src))


def onaccept_tcp(listener, method, mux, handlers):
    global _extra_fd
    try:
        sock, srcip = listener.accept()
    except socket.error, e:
        if e.args[0] in [errno.EMFILE, errno.ENFILE]:
            debug1('Rejected incoming connection: too many open files!\n')
            # free up an fd so we can eat the connection
            os.close(_extra_fd)
            try:
                sock, srcip = listener.accept()
                sock.close()
            finally:
                _extra_fd = os.open('/dev/null', os.O_RDONLY)
            return
        else:
            raise
    if method == "tproxy":
        dstip = sock.getsockname()
    elif method == "pf":
        dstip = pf_dst(sock)
    else:
        dstip = original_dst(sock)
    debug1('Accept TCP: %s:%r -> %s:%r.\n' % (srcip[0], srcip[1],
                                              dstip[0], dstip[1]))
    if dstip[1] == sock.getsockname()[1] and islocal(dstip[0], sock.family):
        debug1("-- ignored: that's my address!\n")
        sock.close()
        return
    chan = mux.next_channel()
    if not chan:
        log('warning: too many open channels.  Discarded connection.\n')
        sock.close()
        return
    mux.send(chan, ssnet.CMD_TCP_CONNECT, '%d,%s,%s' %
             (sock.family, dstip[0], dstip[1]))
    outwrap = MuxWrapper(mux, chan)
    handlers.append(Proxy(SockWrapper(sock, sock), outwrap))
    expire_connections(time.time(), mux)


def udp_done(chan, data, method, family, dstip):
    (src, srcport, data) = data.split(",", 2)
    srcip = (src, int(srcport))
    debug3('doing send from %r to %r\n' % (srcip, dstip,))

    try:
        sender = socket.socket(family, socket.SOCK_DGRAM)
        sender.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
        sender.setsockopt(socket.SOL_IP, IP_TRANSPARENT, 1)
        sender.bind(srcip)
        sender.sendto(data, dstip)
        sender.close()
    except socket.error, e:
        debug1('-- ignored socket error sending UDP data: %r\n' % e)


def onaccept_udp(listener, method, mux, handlers):
    now = time.time()
    srcip, dstip, data = recv_udp(listener, 4096)
    if not dstip:
        debug1(
            "-- ignored UDP from %r: "
            "couldn't determine destination IP address\n" % (srcip,))
        return
    debug1('Accept UDP: %r -> %r.\n' % (srcip, dstip,))
    if srcip in udp_by_src:
        chan, timeout = udp_by_src[srcip]
    else:
        chan = mux.next_channel()
        mux.channels[chan] = lambda cmd, data: udp_done(
            chan, data, method, listener.family, dstip=srcip)
        mux.send(chan, ssnet.CMD_UDP_OPEN, listener.family)
    udp_by_src[srcip] = chan, now + 30

    hdr = "%s,%r," % (dstip[0], dstip[1])
    mux.send(chan, ssnet.CMD_UDP_DATA, hdr + data)

    expire_connections(now, mux)


def dns_done(chan, data, method, sock, srcip, dstip, mux):
    debug3('dns_done: channel=%d src=%r dst=%r\n' % (chan, srcip, dstip))
    del mux.channels[chan]
    del dnsreqs[chan]
    if method == "tproxy":
        debug3('doing send from %r to %r\n' % (srcip, dstip,))
        sender = socket.socket(sock.family, socket.SOCK_DGRAM)
        sender.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
        sender.setsockopt(socket.SOL_IP, IP_TRANSPARENT, 1)
        sender.bind(srcip)
        sender.sendto(data, dstip)
        sender.close()
    else:
        debug3('doing sendto %r\n' % (dstip,))
        sock.sendto(data, dstip)


def ondns(listener, method, mux, handlers):
    now = time.time()
    srcip, dstip, data = recv_udp(listener, 4096)
    if method == "tproxy" and not dstip:
        debug1(
            "-- ignored UDP from %r: "
            "couldn't determine destination IP address\n" % (srcip,))
        return
    debug1('DNS request from %r to %r: %d bytes\n' % (srcip, dstip, len(data)))
    chan = mux.next_channel()
    dnsreqs[chan] = now + 30
    mux.send(chan, ssnet.CMD_DNS_REQ, data)
    mux.channels[chan] = lambda cmd, data: dns_done(
        chan, data, method, listener, srcip=dstip, dstip=srcip, mux=mux)
    expire_connections(now, mux)


def _main(tcp_listener, udp_listener, fw, ssh_cmd, remotename,
          python, latency_control,
          dns_listener, method, seed_hosts, auto_nets,
          syslog, daemon):
    handlers = []
    if helpers.verbose >= 1:
        helpers.logprefix = 'c : '
    else:
        helpers.logprefix = 'client: '
    debug1('connecting to server...\n')

    try:
        (serverproc, serversock) = ssh.connect(
            ssh_cmd, remotename, python,
            stderr=ssyslog._p and ssyslog._p.stdin,
            options=dict(latency_control=latency_control, method=method))
    except socket.error, e:
        if e.args[0] == errno.EPIPE:
            raise Fatal("failed to establish ssh session (1)")
        else:
            raise
    mux = Mux(serversock, serversock)
    handlers.append(mux)

    expected = 'SSHUTTLE0001'

    try:
        v = 'x'
        while v and v != '\0':
            v = serversock.recv(1)
        v = 'x'
        while v and v != '\0':
            v = serversock.recv(1)
        initstring = serversock.recv(len(expected))
    except socket.error, e:
        if e.args[0] == errno.ECONNRESET:
            raise Fatal("failed to establish ssh session (2)")
        else:
            raise

    rv = serverproc.poll()
    if rv:
        raise Fatal('server died with error code %d' % rv)

    if initstring != expected:
        raise Fatal('expected server init string %r; got %r'
                    % (expected, initstring))
    debug1('connected.\n')
    print 'Connected.'
    sys.stdout.flush()
    if daemon:
        daemonize()
        log('daemonizing (%s).\n' % _pidname)
    elif syslog:
        debug1('switching to syslog.\n')
        ssyslog.stderr_to_syslog()

    def onroutes(routestr):
        if auto_nets:
            for line in routestr.strip().split('\n'):
                (family, ip, width) = line.split(',', 2)
                fw.auto_nets.append((family, ip, int(width)))

        # we definitely want to do this *after* starting ssh, or we might end
        # up intercepting the ssh connection!
        #
        # Moreover, now that we have the --auto-nets option, we have to wait
        # for the server to send us that message anyway.  Even if we haven't
        # set --auto-nets, we might as well wait for the message first, then
        # ignore its contents.
        mux.got_routes = None
        fw.start()
    mux.got_routes = onroutes

    def onhostlist(hostlist):
        debug2('got host list: %r\n' % hostlist)
        for line in hostlist.strip().split():
            if line:
                name, ip = line.split(',', 1)
                fw.sethostip(name, ip)
    mux.got_host_list = onhostlist

    tcp_listener.add_handler(handlers, onaccept_tcp, method, mux)

    if udp_listener:
        udp_listener.add_handler(handlers, onaccept_udp, method, mux)

    if dns_listener:
        dns_listener.add_handler(handlers, ondns, method, mux)

    if seed_hosts is not None:
        debug1('seed_hosts: %r\n' % seed_hosts)
        mux.send(0, ssnet.CMD_HOST_REQ, '\n'.join(seed_hosts))

    while 1:
        rv = serverproc.poll()
        if rv:
            raise Fatal('server died with error code %d' % rv)

        ssnet.runonce(handlers, mux)
        if latency_control:
            mux.check_fullness()
        mux.callback()


def main(listenip_v6, listenip_v4,
         ssh_cmd, remotename, python, latency_control, dns,
         method, seed_hosts, auto_nets,
         subnets_include, subnets_exclude, syslog, daemon, pidfile):

    if syslog:
        ssyslog.start_syslog()
    if daemon:
        try:
            check_daemon(pidfile)
        except Fatal, e:
            log("%s\n" % e)
            return 5
    debug1('Starting sshuttle proxy.\n')

    if recvmsg is not None:
        debug1("recvmsg %s support enabled.\n" % recvmsg)

    if method == "tproxy":
        if recvmsg is not None:
            debug1("tproxy UDP support enabled.\n")
            udp = True
        else:
            debug1("tproxy UDP support requires recvmsg function.\n")
            udp = False
        if dns and recvmsg is None:
            debug1("tproxy DNS support requires recvmsg function.\n")
            dns = False
    else:
        debug1("UDP support requires tproxy; disabling UDP.\n")
        udp = False

    if listenip_v6 and listenip_v6[1] and listenip_v4 and listenip_v4[1]:
        # if both ports given, no need to search for a spare port
        ports = [0, ]
    else:
        # if at least one port missing, we have to search
        ports = xrange(12300, 9000, -1)

    # search for free ports and try to bind
    last_e = None
    redirectport_v6 = 0
    redirectport_v4 = 0
    bound = False
    debug2('Binding redirector:')
    for port in ports:
        debug2(' %d' % port)
        tcp_listener = MultiListener()
        tcp_listener.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)

        if udp:
            udp_listener = MultiListener(socket.SOCK_DGRAM)
            udp_listener.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
        else:
            udp_listener = None

        if listenip_v6 and listenip_v6[1]:
            lv6 = listenip_v6
            redirectport_v6 = lv6[1]
        elif listenip_v6:
            lv6 = (listenip_v6[0], port)
            redirectport_v6 = port
        else:
            lv6 = None
            redirectport_v6 = 0

        if listenip_v4 and listenip_v4[1]:
            lv4 = listenip_v4
            redirectport_v4 = lv4[1]
        elif listenip_v4:
            lv4 = (listenip_v4[0], port)
            redirectport_v4 = port
        else:
            lv4 = None
            redirectport_v4 = 0

        try:
            tcp_listener.bind(lv6, lv4)
            if udp_listener:
                udp_listener.bind(lv6, lv4)
            bound = True
            break
        except socket.error, e:
            if e.errno == errno.EADDRINUSE:
                last_e = e
            else:
                raise e
    debug2('\n')
    if not bound:
        assert(last_e)
        raise last_e
    tcp_listener.listen(10)
    tcp_listener.print_listening("TCP redirector")
    if udp_listener:
        udp_listener.print_listening("UDP redirector")

    bound = False
    if dns:
        # search for spare port for DNS
        debug2('Binding DNS:')
        ports = xrange(12300, 9000, -1)
        for port in ports:
            debug2(' %d' % port)
            dns_listener = MultiListener(socket.SOCK_DGRAM)

            if listenip_v6:
                lv6 = (listenip_v6[0], port)
                dnsport_v6 = port
            else:
                lv6 = None
                dnsport_v6 = 0

            if listenip_v4:
                lv4 = (listenip_v4[0], port)
                dnsport_v4 = port
            else:
                lv4 = None
                dnsport_v4 = 0

            try:
                dns_listener.bind(lv6, lv4)
                bound = True
                break
            except socket.error, e:
                if e.errno == errno.EADDRINUSE:
                    last_e = e
                else:
                    raise e
        debug2('\n')
        dns_listener.print_listening("DNS")
        if not bound:
            assert(last_e)
            raise last_e
    else:
        dnsport_v6 = 0
        dnsport_v4 = 0
        dns_listener = None

    fw = FirewallClient(redirectport_v6, redirectport_v4, subnets_include,
                        subnets_exclude, dnsport_v6, dnsport_v4, method, udp)

    if fw.method == "tproxy":
        tcp_listener.setsockopt(socket.SOL_IP, IP_TRANSPARENT, 1)
        if udp_listener:
            udp_listener.setsockopt(socket.SOL_IP, IP_TRANSPARENT, 1)
            if udp_listener.v4 is not None:
                udp_listener.v4.setsockopt(
                    socket.SOL_IP, IP_RECVORIGDSTADDR, 1)
            if udp_listener.v6 is not None:
                udp_listener.v6.setsockopt(SOL_IPV6, IPV6_RECVORIGDSTADDR, 1)
        if dns_listener:
            dns_listener.setsockopt(socket.SOL_IP, IP_TRANSPARENT, 1)
            if dns_listener.v4 is not None:
                dns_listener.v4.setsockopt(
                    socket.SOL_IP, IP_RECVORIGDSTADDR, 1)
            if dns_listener.v6 is not None:
                dns_listener.v6.setsockopt(SOL_IPV6, IPV6_RECVORIGDSTADDR, 1)

    try:
        return _main(tcp_listener, udp_listener, fw, ssh_cmd, remotename,
                     python, latency_control, dns_listener,
                     fw.method, seed_hosts, auto_nets, syslog,
                     daemon)
    finally:
        try:
            if daemon:
                # it's not our child anymore; can't waitpid
                fw.p.returncode = 0
            fw.done()
        finally:
            if daemon:
                daemon_cleanup()