#!/usr/bin/python2
#
# Copyright 2005,2006,2011 Free Software Foundation, Inc.
# 
# This file is part of GNU Radio
# 
# GNU Radio 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 2, or (at your option)
# any later version.
# 
# GNU Radio 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 GNU Radio; see the file COPYING.  If not, write to
# the Free Software Foundation, Inc., 51 Franklin Street,
# Boston, MA 02110-1301, USA.
# 


# /////////////////////////////////////////////////////////////////////////////
#
#    This code sets up up a virtual ethernet interface (typically gr0),
#    and relays packets between the interface and the GNU Radio PHY+MAC
#
#    What this means in plain language, is that if you've got a couple
#    of USRPs on different machines, and if you run this code on those
#    machines, you can talk between them using normal TCP/IP networking.
#
# /////////////////////////////////////////////////////////////////////////////


from gnuradio import gr, digital
from gnuradio import eng_notation
from gnuradio.eng_option import eng_option
from optparse import OptionParser

# from current dir
from receive_path import receive_path
from transmit_path import transmit_path
from uhd_interface import uhd_transmitter
from uhd_interface import uhd_receiver

import os, sys
import random, time, struct

#print os.getpid()
#raw_input('Attach and press enter')


# /////////////////////////////////////////////////////////////////////////////
#
#   Use the Universal TUN/TAP device driver to move packets to/from kernel
#
#   See /usr/src/linux/Documentation/networking/tuntap.txt
#
# /////////////////////////////////////////////////////////////////////////////

# Linux specific...
# TUNSETIFF ifr flags from <linux/tun_if.h>

IFF_TUN		= 0x0001   # tunnel IP packets
IFF_TAP		= 0x0002   # tunnel ethernet frames
IFF_NO_PI	= 0x1000   # don't pass extra packet info
IFF_ONE_QUEUE	= 0x2000   # beats me ;)

def open_tun_interface(tun_device_filename):
    from fcntl import ioctl
    
    mode = IFF_TAP | IFF_NO_PI
    TUNSETIFF = 0x400454ca

    tun = os.open(tun_device_filename, os.O_RDWR)
    ifs = ioctl(tun, TUNSETIFF, struct.pack("16sH", "gr%d", mode))
    ifname = ifs[:16].strip("\x00")
    return (tun, ifname)
    

# /////////////////////////////////////////////////////////////////////////////
#                             the flow graph
# /////////////////////////////////////////////////////////////////////////////

class my_top_block(gr.top_block):
    def __init__(self, callback, options):
        gr.top_block.__init__(self)

        self.source = uhd_receiver(options.args,
                                   options.bandwidth,
                                   options.rx_freq,
                                   options.lo_offset, options.rx_gain,
                                   options.spec, options.antenna,
                                   options.clock_source, options.verbose)

        self.sink = uhd_transmitter(options.args,
                                    options.bandwidth, options.tx_freq,
                                    options.lo_offset, options.tx_gain,
                                    options.spec, options.antenna,
                                    options.clock_source, options.verbose)

        self.txpath = transmit_path(options)
        self.rxpath = receive_path(callback, options)

        self.connect(self.txpath, self.sink)
        self.connect(self.source, self.rxpath)

    def carrier_sensed(self):
        """
        Return True if the receive path thinks there's carrier
        """
        return self.rxpath.carrier_sensed()

    def set_freq(self, target_freq):
        """
        Set the center frequency we're interested in.
        """
        self.u_snk.set_freq(target_freq)
        self.u_src.set_freq(target_freq)
        

# /////////////////////////////////////////////////////////////////////////////
#                           Carrier Sense MAC
# /////////////////////////////////////////////////////////////////////////////

class cs_mac(object):
    """
    Prototype carrier sense MAC

    Reads packets from the TUN/TAP interface, and sends them to the PHY.
    Receives packets from the PHY via phy_rx_callback, and sends them
    into the TUN/TAP interface.

    Of course, we're not restricted to getting packets via TUN/TAP, this
    is just an example.
    """
    def __init__(self, tun_fd, verbose=False):
        self.tun_fd = tun_fd       # file descriptor for TUN/TAP interface
        self.verbose = verbose
        self.tb = None             # top block (access to PHY)

    def set_flow_graph(self, tb):
        self.tb = tb

    def phy_rx_callback(self, ok, payload):
        """
        Invoked by thread associated with PHY to pass received packet up.

        Args:
            ok: bool indicating whether payload CRC was OK
            payload: contents of the packet (string)
        """
        if self.verbose:
            print "Rx: ok = %r  len(payload) = %4d" % (ok, len(payload))
        if ok:
            os.write(self.tun_fd, payload)

    def main_loop(self):
        """
        Main loop for MAC.
        Only returns if we get an error reading from TUN.

        FIXME: may want to check for EINTR and EAGAIN and reissue read
        """
        min_delay = 0.001               # seconds

        while 1:
            payload = os.read(self.tun_fd, 10*1024)
            if not payload:
                self.tb.txpath.send_pkt(eof=True)
                break

            if self.verbose:
                print "Tx: len(payload) = %4d" % (len(payload),)

            delay = min_delay
            while self.tb.carrier_sensed():
                sys.stderr.write('B')
                time.sleep(delay)
                if delay < 0.050:
                    delay = delay * 2       # exponential back-off

            self.tb.txpath.send_pkt(payload)


# /////////////////////////////////////////////////////////////////////////////
#                                   main
# /////////////////////////////////////////////////////////////////////////////

def main():

    parser = OptionParser (option_class=eng_option, conflict_handler="resolve")
    expert_grp = parser.add_option_group("Expert")

    parser.add_option("-m", "--modulation", type="choice", choices=['bpsk', 'qpsk'],
                      default='bpsk',
                      help="Select modulation from: bpsk, qpsk [default=%%default]")
    
    parser.add_option("-v","--verbose", action="store_true", default=False)
    expert_grp.add_option("-c", "--carrier-threshold", type="eng_float", default=30,
                          help="set carrier detect threshold (dB) [default=%default]")
    expert_grp.add_option("","--tun-device-filename", default="/dev/net/tun",
                          help="path to tun device file [default=%default]")

    digital.ofdm_mod.add_options(parser, expert_grp)
    digital.ofdm_demod.add_options(parser, expert_grp)
    transmit_path.add_options(parser, expert_grp)
    receive_path.add_options(parser, expert_grp)
    uhd_receiver.add_options(parser)
    uhd_transmitter.add_options(parser)

    (options, args) = parser.parse_args ()
    if len(args) != 0:
        parser.print_help(sys.stderr)
        sys.exit(1)

    if options.rx_freq is None or options.tx_freq is None:
        sys.stderr.write("You must specify -f FREQ or --freq FREQ\n")
        parser.print_help(sys.stderr)
        sys.exit(1)

    # open the TUN/TAP interface
    (tun_fd, tun_ifname) = open_tun_interface(options.tun_device_filename)

    # Attempt to enable realtime scheduling
    r = gr.enable_realtime_scheduling()
    if r == gr.RT_OK:
        realtime = True
    else:
        realtime = False
        print "Note: failed to enable realtime scheduling"

    # instantiate the MAC
    mac = cs_mac(tun_fd, verbose=True)


    # build the graph (PHY)
    tb = my_top_block(mac.phy_rx_callback, options)

    mac.set_flow_graph(tb)    # give the MAC a handle for the PHY

    print "modulation:     %s"   % (options.modulation,)
    print "freq:           %s"      % (eng_notation.num_to_str(options.tx_freq))

    tb.rxpath.set_carrier_threshold(options.carrier_threshold)
    print "Carrier sense threshold:", options.carrier_threshold, "dB"
    
    print
    print "Allocated virtual ethernet interface: %s" % (tun_ifname,)
    print "You must now use ifconfig to set its IP address. E.g.,"
    print
    print "  $ sudo ifconfig %s 192.168.200.1" % (tun_ifname,)
    print
    print "Be sure to use a different address in the same subnet for each machine."
    print


    tb.start()    # Start executing the flow graph (runs in separate threads)

    mac.main_loop()    # don't expect this to return...

    tb.stop()     # but if it does, tell flow graph to stop.
    tb.wait()     # wait for it to finish
                

if __name__ == '__main__':
    try:
        main()
    except KeyboardInterrupt:
        pass
