Beispiel #1
0
def main():
    if helpers.verbose >= 1:
        helpers.logprefix = ' s: '
    else:
        helpers.logprefix = 'server: '
        
    # synchronization header
    sys.stdout.write('SSHUTTLE0001')
    sys.stdout.flush()

    handlers = []
    mux = Mux(socket.fromfd(sys.stdin.fileno(),
                            socket.AF_INET, socket.SOCK_STREAM),
              socket.fromfd(sys.stdout.fileno(),
                            socket.AF_INET, socket.SOCK_STREAM))
    handlers.append(mux)

    def new_channel(channel, data):
        (dstip,dstport) = data.split(',', 1)
        dstport = int(dstport)
        outwrap = ssnet.connect_dst(dstip,dstport)
        handlers.append(Proxy(MuxWrapper(mux, channel), outwrap))
    
    mux.new_channel = new_channel

    while mux.ok:
        r = set()
        w = set()
        x = set()
        handlers = filter(lambda s: s.ok, handlers)
        for s in handlers:
            s.pre_select(r,w,x)
        debug2('Waiting: %d[%d,%d,%d] (fullness=%d/%d)...\n' 
               % (len(handlers), len(r), len(w), len(x),
                  mux.fullness, mux.too_full))
        (r,w,x) = select.select(r,w,x)
        #log('r=%r w=%r x=%r\n' % (r,w,x))
        ready = set(r) | set(w) | set(x)
        for s in handlers:
            #debug2('check: %r: %r\n' % (s, s.socks & ready))
            if s.socks & ready:
                s.callback()
        mux.check_fullness()
        mux.callback()
Beispiel #2
0
    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))
    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)")
Beispiel #3
0
        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)")
Beispiel #4
0
def main():
    if helpers.verbose >= 1:
        helpers.logprefix = ' s: '
    else:
        helpers.logprefix = 'server: '
    assert latency_control is not None
    debug1('latency control setting = %r\n' % latency_control)

    routes = list(list_routes())
    debug1('available routes:\n')
    for r in routes:
        debug1('  %d/%s/%d\n' % r)

    # synchronization header
    sys.stdout.write('\0\0SSHUTTLE0001')
    sys.stdout.flush()

    handlers = []
    mux = Mux(
        socket.fromfd(sys.stdin.fileno(), socket.AF_INET, socket.SOCK_STREAM),
        socket.fromfd(sys.stdout.fileno(), socket.AF_INET, socket.SOCK_STREAM))
    handlers.append(mux)
    routepkt = ''
    for r in routes:
        routepkt += '%d,%s,%d\n' % r
    mux.send(0, ssnet.CMD_ROUTES, routepkt)

    hw = Hostwatch()
    hw.leftover = ''

    def hostwatch_ready():
        assert (hw.pid)
        content = hw.sock.recv(4096)
        if content:
            lines = (hw.leftover + content).split('\n')
            if lines[-1]:
                # no terminating newline: entry isn't complete yet!
                hw.leftover = lines.pop()
                lines.append('')
            else:
                hw.leftover = ''
            mux.send(0, ssnet.CMD_HOST_LIST, '\n'.join(lines))
        else:
            raise Fatal('hostwatch process died')

    def got_host_req(data):
        if not hw.pid:
            (hw.pid, hw.sock) = start_hostwatch(data.strip().split())
            handlers.append(Handler(socks=[hw.sock], callback=hostwatch_ready))

    mux.got_host_req = got_host_req

    def new_channel(channel, data):
        (family, dstip, dstport) = data.split(',', 2)
        family = int(family)
        dstport = int(dstport)
        outwrap = ssnet.connect_dst(family, dstip, dstport)
        handlers.append(Proxy(MuxWrapper(mux, channel), outwrap))

    mux.new_channel = new_channel

    dnshandlers = {}

    def dns_req(channel, data):
        debug2('Incoming DNS request channel=%d.\n' % channel)
        h = DnsProxy(mux, channel, data)
        handlers.append(h)
        dnshandlers[channel] = h

    mux.got_dns_req = dns_req

    udphandlers = {}

    def udp_req(channel, cmd, data):
        debug2('Incoming UDP request channel=%d, cmd=%d\n' % (channel, cmd))
        if cmd == ssnet.CMD_UDP_DATA:
            (dstip, dstport, data) = data.split(",", 2)
            dstport = int(dstport)
            debug2('is incoming UDP data. %r %d.\n' % (dstip, dstport))
            h = udphandlers[channel]
            h.send((dstip, dstport), data)
        elif cmd == ssnet.CMD_UDP_CLOSE:
            debug2('is incoming UDP close\n')
            h = udphandlers[channel]
            h.ok = False
            del mux.channels[channel]

    def udp_open(channel, data):
        debug2('Incoming UDP open.\n')
        family = int(data)
        mux.channels[channel] = lambda cmd, data: udp_req(channel, cmd, data)
        if channel in udphandlers:
            raise Fatal('UDP connection channel %d already open' % channel)
        else:
            h = UdpProxy(mux, channel, family)
            handlers.append(h)
            udphandlers[channel] = h

    mux.got_udp_open = udp_open

    while mux.ok:
        if hw.pid:
            assert (hw.pid > 0)
            (rpid, rv) = os.waitpid(hw.pid, os.WNOHANG)
            if rpid:
                raise Fatal('hostwatch exited unexpectedly: code 0x%04x\n' %
                            rv)

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

        if dnshandlers:
            now = time.time()
            for channel, h in dnshandlers.items():
                if h.timeout < now or not h.ok:
                    debug3('expiring dnsreqs channel=%d\n' % channel)
                    del dnshandlers[channel]
                    h.ok = False
        if udphandlers:
            for channel, h in udphandlers.items():
                if not h.ok:
                    debug3('expiring UDP channel=%d\n' % channel)
                    del udphandlers[channel]
                    h.ok = False
Beispiel #5
0
def main():
    if helpers.verbose >= 1:
        helpers.logprefix = ' s: '
    else:
        helpers.logprefix = 'server: '
    assert latency_control is not None
    debug1('latency control setting = %r\n' % latency_control)

    routes = list(list_routes())
    debug1('available routes:\n')
    for r in routes:
        debug1('  %d/%s/%d\n' % r)

    # synchronization header
    sys.stdout.write('\0\0SSHUTTLE0001')
    sys.stdout.flush()

    handlers = []
    mux = Mux(socket.fromfd(sys.stdin.fileno(),
                            socket.AF_INET, socket.SOCK_STREAM),
              socket.fromfd(sys.stdout.fileno(),
                            socket.AF_INET, socket.SOCK_STREAM))
    handlers.append(mux)
    routepkt = ''
    for r in routes:
        routepkt += '%d,%s,%d\n' % r
    mux.send(0, ssnet.CMD_ROUTES, routepkt)

    hw = Hostwatch()
    hw.leftover = ''

    def hostwatch_ready():
        assert(hw.pid)
        content = hw.sock.recv(4096)
        if content:
            lines = (hw.leftover + content).split('\n')
            if lines[-1]:
                # no terminating newline: entry isn't complete yet!
                hw.leftover = lines.pop()
                lines.append('')
            else:
                hw.leftover = ''
            mux.send(0, ssnet.CMD_HOST_LIST, '\n'.join(lines))
        else:
            raise Fatal('hostwatch process died')

    def got_host_req(data):
        if not hw.pid:
            (hw.pid, hw.sock) = start_hostwatch(data.strip().split())
            handlers.append(Handler(socks=[hw.sock],
                                    callback=hostwatch_ready))
    mux.got_host_req = got_host_req

    def new_channel(channel, data):
        (family, dstip, dstport) = data.split(',', 2)
        family = int(family)
        dstport = int(dstport)
        outwrap = ssnet.connect_dst(family, dstip, dstport)
        handlers.append(Proxy(MuxWrapper(mux, channel), outwrap))
    mux.new_channel = new_channel

    dnshandlers = {}

    def dns_req(channel, data):
        debug2('Incoming DNS request channel=%d.\n' % channel)
        h = DnsProxy(mux, channel, data)
        handlers.append(h)
        dnshandlers[channel] = h
    mux.got_dns_req = dns_req

    udphandlers = {}

    def udp_req(channel, cmd, data):
        debug2('Incoming UDP request channel=%d, cmd=%d\n' % (channel, cmd))
        if cmd == ssnet.CMD_UDP_DATA:
            (dstip, dstport, data) = data.split(",", 2)
            dstport = int(dstport)
            debug2('is incoming UDP data. %r %d.\n' % (dstip, dstport))
            h = udphandlers[channel]
            h.send((dstip, dstport), data)
        elif cmd == ssnet.CMD_UDP_CLOSE:
            debug2('is incoming UDP close\n')
            h = udphandlers[channel]
            h.ok = False
            del mux.channels[channel]

    def udp_open(channel, data):
        debug2('Incoming UDP open.\n')
        family = int(data)
        mux.channels[channel] = lambda cmd, data: udp_req(channel, cmd, data)
        if channel in udphandlers:
            raise Fatal('UDP connection channel %d already open' % channel)
        else:
            h = UdpProxy(mux, channel, family)
            handlers.append(h)
            udphandlers[channel] = h
    mux.got_udp_open = udp_open

    while mux.ok:
        if hw.pid:
            assert(hw.pid > 0)
            (rpid, rv) = os.waitpid(hw.pid, os.WNOHANG)
            if rpid:
                raise Fatal(
                    'hostwatch exited unexpectedly: code 0x%04x\n' % rv)

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

        if dnshandlers:
            now = time.time()
            for channel, h in dnshandlers.items():
                if h.timeout < now or not h.ok:
                    debug3('expiring dnsreqs channel=%d\n' % channel)
                    del dnshandlers[channel]
                    h.ok = False
        if udphandlers:
            for channel, h in udphandlers.items():
                if not h.ok:
                    debug3('expiring UDP channel=%d\n' % channel)
                    del udphandlers[channel]
                    h.ok = False
Beispiel #6
0
        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))
    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:
        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)
Beispiel #7
0
    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))
    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)")
Beispiel #8
0
def main():
    if helpers.verbose >= 1:
        helpers.logprefix = ' s: '
    else:
        helpers.logprefix = 'server: '

    routes = list(list_routes())
    debug1('available routes:\n')
    for r in routes:
        debug1('  %s/%d\n' % r)
        
    # synchronization header
    sys.stdout.write('SSHUTTLE0001')
    sys.stdout.flush()

    handlers = []
    mux = Mux(socket.fromfd(sys.stdin.fileno(),
                            socket.AF_INET, socket.SOCK_STREAM),
              socket.fromfd(sys.stdout.fileno(),
                            socket.AF_INET, socket.SOCK_STREAM))
    handlers.append(mux)
    routepkt = ''
    for r in routes:
        routepkt += '%s,%d\n' % r
    mux.send(0, ssnet.CMD_ROUTES, routepkt)

    hw = Hostwatch()
    hw.leftover = ''
        
    def hostwatch_ready():
        assert(hw.pid)
        content = hw.sock.recv(4096)
        if content:
            lines = (hw.leftover + content).split('\n')
            if lines[-1]:
                # no terminating newline: entry isn't complete yet!
                hw.leftover = lines.pop()
                lines.append('')
            else:
                hw.leftover = ''
            mux.send(0, ssnet.CMD_HOST_LIST, '\n'.join(lines))
        else:
            raise Fatal('hostwatch process died')

    def got_host_req(data):
        if not hw.pid:
            (hw.pid,hw.sock) = start_hostwatch(data.strip().split())
            handlers.append(Handler(socks = [hw.sock],
                                    callback = hostwatch_ready))
    mux.got_host_req = got_host_req

    def new_channel(channel, data):
        (dstip,dstport) = data.split(',', 1)
        dstport = int(dstport)
        outwrap = ssnet.connect_dst(dstip,dstport)
        handlers.append(Proxy(MuxWrapper(mux, channel), outwrap))
    mux.new_channel = new_channel

    while mux.ok:
        if hw.pid:
            (rpid, rv) = os.waitpid(hw.pid, os.WNOHANG)
            if rpid:
                raise Fatal('hostwatch exited unexpectedly: code 0x%04x\n' % rv)
        
        ssnet.runonce(handlers, mux)
        mux.check_fullness()
        mux.callback()
Beispiel #9
0
def main():
    if helpers.verbose >= 1:
        helpers.logprefix = ' s: '
    else:
        helpers.logprefix = 'server: '

    routes = list(list_routes())
    debug1('available routes:\n')
    for r in routes:
        debug1('  %s/%d\n' % r)
        
    # synchronization header
    sys.stdout.write('SSHUTTLE0001')
    sys.stdout.flush()

    handlers = []
    mux = Mux(socket.fromfd(sys.stdin.fileno(),
                            socket.AF_INET, socket.SOCK_STREAM),
              socket.fromfd(sys.stdout.fileno(),
                            socket.AF_INET, socket.SOCK_STREAM))
    handlers.append(mux)
    routepkt = ''.join('%s,%d\n' % r
                       for r in routes)
    mux.send(0, ssnet.CMD_ROUTES, routepkt)

    hw = Hostwatch()

    def hostwatch_ready():
        assert(hw.pid)
        content = hw.sock.recv(4096)
        if content:
            mux.send(0, ssnet.CMD_HOST_LIST, content)
        else:
            raise Fatal('hostwatch process died')

    def got_host_req(data):
        if not hw.pid:
            (hw.pid,hw.sock) = start_hostwatch(data.strip().split())
            handlers.append(Handler(socks = [hw.sock],
                                    callback = hostwatch_ready))
    mux.got_host_req = got_host_req

    def new_channel(channel, data):
        (dstip,dstport) = data.split(',', 1)
        dstport = int(dstport)
        outwrap = ssnet.connect_dst(dstip,dstport)
        handlers.append(Proxy(MuxWrapper(mux, channel), outwrap))
    mux.new_channel = new_channel

    while mux.ok:
        if hw.pid:
            (rpid, rv) = os.waitpid(hw.pid, os.WNOHANG)
            if rpid:
                raise Fatal('hostwatch exited unexpectedly: code 0x%04x\n' % rv)
        
        r = set()
        w = set()
        x = set()
        handlers = filter(lambda s: s.ok, handlers)
        for s in handlers:
            s.pre_select(r,w,x)
        debug2('Waiting: %d[%d,%d,%d] (fullness=%d/%d)...\n' 
               % (len(handlers), len(r), len(w), len(x),
                  mux.fullness, mux.too_full))
        (r,w,x) = select.select(r,w,x)
        #log('r=%r w=%r x=%r\n' % (r,w,x))
        ready = set(r) | set(w) | set(x)
        for s in handlers:
            #debug2('check: %r: %r\n' % (s, s.socks & ready))
            if s.socks & ready:
                s.callback()
        mux.check_fullness()
        mux.callback()
Beispiel #10
0
def _main(listener, fw, use_server, remotename, seed_hosts, auto_nets):
    handlers = []
    if use_server:
        if helpers.verbose >= 1:
            helpers.logprefix = "c : "
        else:
            helpers.logprefix = "client: "
        (serverproc, serversock) = ssh.connect(remotename)
        mux = Mux(serversock, serversock)
        handlers.append(mux)

        expected = "SSHUTTLE0001"
        initstring = serversock.recv(len(expected))

        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))

    def onroutes(routestr):
        if auto_nets:
            for line in routestr.strip().split("\n"):
                (ip, width) = line.split(",", 1)
                fw.auto_nets.append((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

    def onaccept():
        sock, srcip = listener.accept()
        dstip = original_dst(sock)
        debug1("Accept: %r:%r -> %r:%r.\n" % (srcip[0], srcip[1], dstip[0], dstip[1]))
        if dstip == listener.getsockname():
            debug1("-- ignored: that's my address!\n")
            sock.close()
            return
        if use_server:
            chan = mux.next_channel()
            mux.send(chan, ssnet.CMD_CONNECT, "%s,%s" % dstip)
            outwrap = MuxWrapper(mux, chan)
        else:
            outwrap = ssnet.connect_dst(dstip[0], dstip[1])
        handlers.append(Proxy(SockWrapper(sock, sock), outwrap))

    handlers.append(Handler([listener], onaccept))

    if seed_hosts != None:
        debug1("seed_hosts: %r\n" % seed_hosts)
        mux.send(0, ssnet.CMD_HOST_REQ, "\n".join(seed_hosts))

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

        r = set()
        w = set()
        x = set()
        handlers = filter(lambda s: s.ok, handlers)
        for s in handlers:
            s.pre_select(r, w, x)
        debug2("Waiting: %d[%d,%d,%d]...\n" % (len(handlers), len(r), len(w), len(x)))
        (r, w, x) = select.select(r, w, x)
        # log('r=%r w=%r x=%r\n' % (r,w,x))
        ready = set(r) | set(w) | set(x)
        for s in handlers:
            if s.socks & ready:
                s.callback()
        if use_server:
            mux.callback()
            mux.check_fullness()
Beispiel #11
0
def main():
    if helpers.verbose >= 1:
        helpers.logprefix = ' s: '
    else:
        helpers.logprefix = 'server: '
    debug1('latency control setting = %r\n' % latency_control)

    routes = list(list_routes())
    debug1('available routes:\n')
    for r in routes:
        debug1('  %s/%d\n' % r)

    # synchronization header
    sys.stdout.write('SSHUTTLE0001')
    sys.stdout.flush()

    handlers = []
    mux = Mux(
        socket.fromfd(sys.stdin.fileno(), socket.AF_INET, socket.SOCK_STREAM),
        socket.fromfd(sys.stdout.fileno(), socket.AF_INET, socket.SOCK_STREAM))
    handlers.append(mux)
    routepkt = ''
    for r in routes:
        routepkt += '%s,%d\n' % r
    mux.send(0, ssnet.CMD_ROUTES, routepkt)

    hw = Hostwatch()
    hw.leftover = ''

    def hostwatch_ready():
        assert (hw.pid)
        content = hw.sock.recv(4096)
        if content:
            lines = (hw.leftover + content).split('\n')
            if lines[-1]:
                # no terminating newline: entry isn't complete yet!
                hw.leftover = lines.pop()
                lines.append('')
            else:
                hw.leftover = ''
            mux.send(0, ssnet.CMD_HOST_LIST, '\n'.join(lines))
        else:
            raise Fatal('hostwatch process died')

    def got_host_req(data):
        if not hw.pid:
            (hw.pid, hw.sock) = start_hostwatch(data.strip().split())
            handlers.append(Handler(socks=[hw.sock], callback=hostwatch_ready))

    mux.got_host_req = got_host_req

    def new_channel(channel, data):
        (dstip, dstport) = data.split(',', 1)
        dstport = int(dstport)
        outwrap = ssnet.connect_dst(dstip, dstport)
        handlers.append(Proxy(MuxWrapper(mux, channel), outwrap))

    mux.new_channel = new_channel

    dnshandlers = {}

    def dns_req(channel, data):
        debug2('Incoming DNS request.\n')
        h = DnsProxy(mux, channel, data)
        handlers.append(h)
        dnshandlers[channel] = h

    mux.got_dns_req = dns_req

    while mux.ok:
        if hw.pid:
            assert (hw.pid > 0)
            (rpid, rv) = os.waitpid(hw.pid, os.WNOHANG)
            if rpid:
                raise Fatal('hostwatch exited unexpectedly: code 0x%04x\n' %
                            rv)

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

        if dnshandlers:
            now = time.time()
            for channel, h in dnshandlers.items():
                if h.timeout < now or not h.ok:
                    del dnshandlers[channel]
                    h.ok = False
Beispiel #12
0
def _main(listener, fw, use_server, remotename):
    handlers = []
    if use_server:
        if helpers.verbose >= 1:
            helpers.logprefix = "c : "
        else:
            helpers.logprefix = "client: "
        (serverproc, serversock) = ssh.connect(remotename)
        mux = Mux(serversock, serversock)
        handlers.append(mux)

        expected = "SSHUTTLE0001"
        initstring = serversock.recv(len(expected))

        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))

    # we definitely want to do this *after* starting ssh, or we might end
    # up intercepting the ssh connection!
    fw.start()

    def onaccept():
        sock, srcip = listener.accept()
        dstip = original_dst(sock)
        debug1("Accept: %r:%r -> %r:%r.\n" % (srcip[0], srcip[1], dstip[0], dstip[1]))
        if dstip == listener.getsockname():
            debug1("-- ignored: that's my address!\n")
            sock.close()
            return
        if use_server:
            chan = mux.next_channel()
            mux.send(chan, ssnet.CMD_CONNECT, "%s,%s" % dstip)
            outwrap = MuxWrapper(mux, chan)
        else:
            outwrap = ssnet.connect_dst(dstip[0], dstip[1])
        handlers.append(Proxy(SockWrapper(sock, sock), outwrap))

    handlers.append(Handler([listener], onaccept))

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

        r = set()
        w = set()
        x = set()
        handlers = filter(lambda s: s.ok, handlers)
        for s in handlers:
            s.pre_select(r, w, x)
        debug2("Waiting: %d[%d,%d,%d]...\n" % (len(handlers), len(r), len(w), len(x)))
        (r, w, x) = select.select(r, w, x)
        # log('r=%r w=%r x=%r\n' % (r,w,x))
        ready = set(r) | set(w) | set(x)
        for s in handlers:
            if s.socks & ready:
                s.callback()
        if use_server:
            mux.callback()
            mux.check_fullness()