#!/bin/bash
#
#  Copyright (c) 2017, The OpenThread Authors.
#  All rights reserved.
#
#  Redistribution and use in source and binary forms, with or without
#  modification, are permitted provided that the following conditions are met:
#  1. Redistributions of source code must retain the above copyright
#     notice, this list of conditions and the following disclaimer.
#  2. Redistributions in binary form must reproduce the above copyright
#     notice, this list of conditions and the following disclaimer in the
#     documentation and/or other materials provided with the distribution.
#  3. Neither the name of the copyright holder nor the
#     names of its contributors may be used to endorse or promote products
#     derived from this software without specific prior written permission.
#
#  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
#  AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
#  IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
#  ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
#  LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
#  CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
#  SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
#  INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
#  CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
#  ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
#  POSSIBILITY OF SUCH DAMAGE.
#
#----------------------------------------
# Purpose:
#  To understand the purpose of this script see: print_big_ugly_warning() below.
#----------------------------------------
#

# remember the name of this script
SCRIPT_NAME=$0

CWD=$(pwd)
DATE=$(date)

# shellcheck source=script/_initrc
. "$(dirname "$0")"/_initrc

ETH0_IPV6_BASE_PREFIX=fd11:33

debug_echo()
{
    if [ "${_DEBUG_IPV6}" == "true" ]; then
        echo "${@}"
    fi
}

determine_eth0_name()
{
    ETH0_NAME=''

    #
    # this gives us a sorted list of network interface names
    for devname in $(
        cd /sys/class/net || exit
        ls
    ); do
        # We want the physical device
        # Not things like "usb0" or "wpan0"
        # And we assume the first one is what we want
        debug_echo "Consider: ${devname}"
        ignore=false
        case ${devname} in
            usb* | can* | wpan* | br* | wlan* | lo)
                # by name we can ignore USB-gadget, CANbus, Thread, wireless and loopback
                ignore=true
                ;;
            *)
                ignore=false
                ;;
        esac

        if $ignore; then
            debug_echo "Ignore ${devname} by name"
            continue
        fi

        debug_echo "Consider: ${devname}"
        if [ ! -L /sys/class/net/"${devname}"/device ]; then
            debug_echo "Not a DEVICE ${devname}"
            continue
        fi

        type=$(cat /sys/class/net/"${devname}"/type)
        # Type1 = ARPHRD_ETHER
        if [ "$type" -ne 1 ]; then
            debug_echo "Not ARPHRD_ETHER"
            continue
        fi
        # We assume the first thing we find is our device
        ETH0_NAME=${devname}
        break
    done

    if [ -z "${ETH0_NAME}" ]; then
        echo "Cannot determine ETH0 name...."
        exit 1
    fi
    echo "Assuming: Primary ETHERNET name is $ETH0_NAME"
}

install_radvd()
{
    echo "Fetching RADVD..."
    echo "apt-get install --no-install-recommends radvd"
    sudo apt-get install --no-install-recommends radvd
}

choose_random_eth0_address()
{
    # steps below are
    #   Using "od" see http://man7.org/linux/man-pages/man1/od.1.html
    #      read from /dev/urandom
    #
    # We use /dev/urandom not /dev/random for these reasons:
    # 1) This is for private (not public) test purposes
    # 2) urandom might stall ... and not give us bytes
    #
    # We want data in 16bit hex, hence: --format=x2
    # We want only 4 bytes, hence --read-bytes=4
    #
    # The output looks like:
    #      0000000 1234 5678
    #      0000008
    #
    # head gives us the first line
    # cut gives us the items 2 and 3 on the line
    # tr  converts the space into a ':'
    #
    RANDOM_32BIT_VALUE=$(od --read-bytes=4 --format=x2 /dev/urandom \
        | head -1 \
        | cut -d' ' -f2,3 \
        | tr ' ' ':')

    # thus, "RANDOM_32BIT_VALUE=1234:5678"

    # We'll use this for the radvd config
    ETH0_IPV6_PREFIX=${ETH0_IPV6_BASE_PREFIX}:${RANDOM_32BIT_VALUE}

    # and this for the static network address
    ETH0_IPV6_STATIC_ADDRESS=${ETH0_IPV6_PREFIX}::1
}

configure_radvd()
{
    # this creates a configuration file for radvd
    CFG_FILE=/etc/radvd.conf
    if [ -f $CFG_FILE ]; then
        echo "radvd config file exists: $CFG_FILE"
        echo "SKIPPING radvd configuration"
    else
        sudo tee -a /etc/radvd.conf <<__EOF__
#
# This RADVD configuration file was created
# by the OpenThread configuration script $SCRIPT_NAME
# Executed in the directory ${CWD} on ${DATE}
#
# The purpose is to configure IPV6 in an issolated and
# standalone network configuration for the purpose of test only
#
# This is by no means a complete IPv6 configuration
# it is sufficent to allow coap transactions
# with thread devices on the thread mesh network
# attched to this boarder router
#
interface ${ETH0_NAME} {
    # We want to send router adverts
    AdvSendAdvert on;

    # This is not a proper IPv6 router
    # it is only for openthread
    AdvDefaultPreference low;

    # We should advertize this prefix
    prefix ${ETH0_IPV6_PREFIX}::/64 {
         # we want this "on link"
         AdvOnLink on;
         # devices should self-assign addresses with this prefix
         AdvAutonomous on;
         AdvRouterAddr on;
    };
};
__EOF__
    fi
}

assign_eth0_static_ipv6()
{

    # this creates a static IPv6 address for Eth0
    sudo tee -a /etc/network/interfaces <<__EOF__

# This configuration was created by
# the openthread ${SCRIPT_NAME}
# executing in the directory ${CWD}
# and executed on ${DATE}
#
# for the purposes of testing ipv6 addresses
# in an issolated network configuration

# ensure ETH0 is configured at boot
auto ${ETH0_NAME}

# Configure the IPv6 address static
# Note: IPv4 is not effected by this
iface ${ETH0_NAME} inet6 static
    address ${ETH0_IPV6_STATIC_ADDRESS}
    netmask 64
__EOF__

}

# on BBB we do this.
# other platforms might do something simular
bbb_main()
{
    install_radvd
    determine_eth0_name
    choose_random_eth0_address
    configure_radvd
    assign_eth0_static_ipv6

    echo "You should now reboot your Device"
}

print_big_ugly_warning()
{
    # Scare our victim.

    cat <<_EOF_

Please understand the purpose of this script.

This script is not intended to be an complete and proper IPv6
configuration script.

This is only hack that turns on just enough IPv6 to perform simple
CoAP requests on or across an issolated test network to the Thread
network.

The example issolated test network consists of these parts:

1) A thread RF radio network.

2) The OpenThread Border router attached to the Thread network

3) The Openthread Border router would typically be connected
   to a residential home network in some way (wifi, or wired)

   In this case, it is connected to a router that is not
   connected to an upstream provider - it is issolated.

4) In order to test & develop applications other things on the
   "home/test network" need to talk to the various Thread end nodes
   via IPv6

   Examples include:

   * Laptop, or desktop machine
   * Android/Apple Phone or Tablet
   * other network devices

To test/develop your applications a means for these other devices on
your test network to talk to devices on the Thread Network must exist.

The problem:


   Most home network routers provide only IPv4 services. They most
   typically assume the upstream ISP network provider will provide
   IPv6 addresses and configuration. A test network is often issolated
   and not connected to the large world wide web, it is completely an
   island. The upstream ISP provider does not exist.

   In the end something needs to provide a minimal IPv6 configuration.

=========================================================
The above is the purpose of this ipv6 standalone hack script

Never consider this script a proper IPv6 configuration.
=========================================================

It is only a quick hack that enables enough IPv6 to work such that:

1) Your local test laptop/cellphone has an IPv6 address and
2) can perform CoAP transfers between a node on thread network

Now that you have read and understood the above, execute this script
again like this:

      ${SCRIPT_NAME}   enable_ipv6_hack

_EOF_

}

# ensure user/victim has read the ugly warning.
if [ "${1}" != "enable_ipv6_hack" ]; then
    print_big_ugly_warning
    exit 1
fi

# platforms specifc
case ${PLATFORM} in
    "beagleboneblack")
        bbb_main
        ;;
    *)
        die "Unsupported/unknown platform ${PLATFORM}"
        ;;
esac