#!/bin/bash
# RUN PPPD DAEMON
#
# Oliver Molini 2021
# 
# Billy Stoughton II for bug fixes and contributions
#
# Licensed under Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International Public License
# https://creativecommons.org/licenses/by-nc-sa/4.0/
#
# Note on PPPD settings:
# - Make sure the noauth option is set (instead of auth)
# - Make sure DNS servers are defined (add ms-dns 1.2.3.4 twice)
#

# Variable: etherp
# Override the ethernet device to use to connect to your network.
# This is set in vmodem.sh, but can be overridden here.
#
# Default:    #etherp=eth0 (commented out)
#etherp=eth0

# Variable: lcpidle
# Specifies the idle timeout period in seconds for lcp-echo-interval.
# This is to ensure that pppd will not run indefinitely after sudden
# hangup and will relinquish control back to the vmodem.sh.
#
# Default:    lcpidle=5
lcpidle=10

#
# Trumpet Winsock 3.0 revision D for Windows 3.1
# by default requires a fake login shell.
#
# Windows 95 and 98 will not care for a login shell
# unless specifically told to expect one.
#

sleep 2
sendtty "\n\n`uname -sn`****\n\n"
sendtty  "Username: "; sleep 1; sendtty "\n"
sendtty  "Password: "; sleep 1; sendtty "\n"
sendtty  "Starting pppd...\n"
sendtty  "PPP>"
# End of fake login prompt.

# Set the kernel to router mode
sysctl -q net.ipv4.ip_forward=1

# Share eth0 over ppp0
iptables -t nat -A POSTROUTING -o $etherp -j MASQUERADE
iptables -t filter -A FORWARD -i ppp0 -o $etherp -m state --state RELATED,ESTABLISHED -j ACCEPT
iptables -t filter -A FORWARD -i $etherp -o ppp0 -j ACCEPT

# Run PPP daemon and establish a link.
pppd noauth nodetach local lock lcp-echo-interval $lcpidle lcp-echo-failure 3 proxyarp ms-dns 8.8.4.4 ms-dns 8.8.8.8 10.0.100.1:10.0.100.2 /dev/$serport $baud

# Flush iptables
iptables -t filter -F FORWARD
iptables -t nat -F POSTROUTING

printf "\nPPP link terminated.\n"