vpn through pppd

vpn.sh

#!/bin/bash

interface=eth0
address=
gateway=
broadcast=
netmask=
vpn_local=10.0.0.1
vpn_remote=10.0.0.2
ssh_user=root
ssh_address=107.182.226.113
ssh_port=22
dnses=('8.8.8.8', '8.8.4.4')
ssh_opts="-c chacha20-poly1305@openssh.com -i /home/bart/.ssh/id_rsa"
pppd_opts="nodeflate nobsdcomp"

msg() {
    cols=$(tput cols)
    len=${#1}
    let columns="cols - len - 6"
    printf "\e[1;97m%s%*s" "$1" $columns
}

msgend() {
    printf "\e[1;92m[DONE]\e[0m\n" 
}

msgendfail() {
    printf "\e[1;91m[FAIL]\e[0m\n" 
    exit 1
}

detect() {
    msg "Reading /etc/conf.d/vpn configuration..."
    #[ -e /etc/conf.d/vpn ] || msgendfail
    #source /etc/conf.d/vpn || msgendfail
    if [ -z "$ssh_user" ] || [ -z "$ssh_address" ] || [ -z "$ssh_port" ] || [ -z "$vpn_local" ] || [ -z "$vpn_remote" ]; then
        msgendfail
    fi
    msgend

    msg "Detecting network configuration..."
    if [ -z "$gateway" ]; then
      gateway=`ip route | grep -E "default via [0-9.]* dev $interface" | sed "s/.*via \([0-9].*\) dev $interface.*/\1/"`
      if [ -z "$gateway" ]; then
          gateway=`ip route | grep -E "$ssh_address via [0-9.]* dev $interface" | sed "s/.*via \([0-9].*\) dev $interface.*/\1/"`
      fi
    fi
    if [ -z "$address" ]; then
        address=`ip addr show $interface | grep "inet " | sed 's/.*inet \([0-9.]*\)\/.*/\1/'`
    fi
    if [ -z "$broadcast" ]; then
        broadcast=`ip addr show $interface | grep "inet " | sed 's/.*brd \([0-9.]*\).*/\1/'`
    fi
    if [ -z "$netmask" ]; then
        netmask=`ip addr show $interface | grep "inet " | sed 's/.*inet [0-9.]*\/\([0-9]*\).*/\1/'`
    fi
    if [ -z "$address" ] || [ -z "$gateway" ] || [ -z "$broadcast" ] || [ -z "$netmask" ]; then
        msgendfail
    fi
    msgend
}

start() {
    msg "Writing nameservers..."
    echo -n > /etc/resolv.conf
    for dns in ${dnses[*]}; do
      echo "nameserver $dns" >> /etc/resolv.conf
    done
    msgend

    msg "Killing dhcpcd and pppd daemons..."
    killall -qw dhcpcd
    killall -qw pppd
    msgend

    msg "Configuring network..."
    ip addr flush dev $interface || msgendfail
    ip link set dev $interface up || msgendfail
    ip addr add $address/$netmask broadcast $broadcast dev $interface || msgendfail
    ip route replace default via $gateway dev $interface || msgendfail
    ip route replace $ssh_address via $gateway dev $interface || msgendfail
    msgend

    msg "Connecting to VPN through pppd..."
    /usr/sbin/pppd \
        updetach noauth $pppd_opts silent pty \
        "/usr/bin/ssh $ssh_opts -p $ssh_port $ssh_user@$ssh_address sudo /usr/sbin/pppd nodetach notty noauth" \
        ipparam vpn $vpn_local:$vpn_remote || msgendfail
    gotvpnaddr=`ip addr show ppp0 | grep "inet " |  sed 's/.*inet \([0-9.]*\)[\/ ].*/\1/'`
    if [ ! "$gotvpnaddr" == "$vpn_local" ]; then
      killall -q pppd
      msgendfail
    fi
    msgend

    msg "Changing default gateway..."
    ip route replace default via $vpn_remote || msgendfail
    msgend
}

stop() {
    msg "Replacing old gateway..."
    ip route replace default via $gateway dev $interface || msgendfail
    msgend

    msg "Waiting pppd to finish..."
    killall -qw pppd
    msgend
}

case "$1" in
    start)
        detect
        start;;
    stop)
        detect
        stop;;
    info)
        detect
        echo interface $interface $address/$netmask broadcast $broadcast gw $gateway
        echo vpn local $vpn_local remote $vpn_remote
        echo dnses ${dnses[@]}
        echo remote ssh $ssh_user@$ssh_address:$ssh_port
        ;;
    restart)
        detect
        stop
        sleep 1
        start;;
    *)
        echo "usage: $0 {start|stop|restart|info}";;
esac