#!/bin/sh
# Use separate addresses for gateway, DHCP, and host, in order to force using ARP and ND
BRIDGE=mg_bridge0
BRIDGE_BROADCAST=192.168.32.255
BRIDGE_IP=192.168.32.2
BRIDGE_NETWORK=192.168.32.0/24
BRIDGE_MASK=255.255.255.0
GATEWAY_IP=192.168.32.1 # dhcp.conf serves 192.168.32.1 as gateway
HOST_IP=192.168.32.3
BRIDGE_IPV6=fe80::01ff:fe02:0301 # radvd.conf uses this address as its own
HOST_IPV6=fe80::01ff:fe02:0303
# Host outside network interface is 'eth0'
TAP=tap0

# see our network configuration
echo "Network configuration:"
timeout 1s ifconfig
timeout 1s sudo route -n    # see our gateway
timeout 1s bridge link
timeout 1s bridge fdb
timeout 1s sudo ip -6 route show
echo

# Package installation
echo "Package installation"
sudo apt-get -y install isc-dhcp-server net-tools radvd
sudo systemctl stop radvd # just in case they think it is cool to start it
# sudo apt-get -y install build-essential sshpass
echo

echo "Network configuration script: Bridge"
sudo ip link add $BRIDGE type bridge	# Create brige
sudo ifconfig $BRIDGE $BRIDGE_IP netmask $BRIDGE_MASK up
sudo ifconfig $BRIDGE:1 $GATEWAY_IP netmask $BRIDGE_MASK up
sudo ifconfig $BRIDGE:2 $HOST_IP netmask $BRIDGE_MASK up
sudo ip -6 addr add $BRIDGE_IPV6/64 dev $BRIDGE
sudo ip -6 addr add $HOST_IPV6/64 dev $BRIDGE:1
echo

echo "Network configuration script: TAP"
echo "Create $TAP attached to $BRIDGE"
sudo ip tuntap add dev $TAP mode tap	# Create tuntap
sudo ip link set $TAP master $BRIDGE	# Link tap-bridge
sudo ip link set $TAP up
echo

echo "Network configuration script: NAT"
sudo iptables -A FORWARD -d $BRIDGE_NETWORK -o $BRIDGE -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT
sudo iptables -A FORWARD -s $BRIDGE_NETWORK -i $BRIDGE -j ACCEPT
sudo iptables -A FORWARD -i $BRIDGE -o $BRIDGE -j ACCEPT
sudo iptables -A FORWARD -o $BRIDGE -j REJECT --reject-with icmp-port-unreachable
sudo iptables -A FORWARD -i $BRIDGE -j REJECT --reject-with icmp-port-unreachable
sudo iptables -t nat -A POSTROUTING -s $BRIDGE_NETWORK -d 224.0.0.0/24 -j RETURN
sudo iptables -t nat -A POSTROUTING -s $BRIDGE_NETWORK -d 255.255.255.255/32 -j RETURN
sudo iptables -t nat -A POSTROUTING -s $BRIDGE_NETWORK ! -d $BRIDGE_NETWORK -p tcp -j MASQUERADE --to-ports 1024-65535
sudo iptables -t nat -A POSTROUTING -s $BRIDGE_NETWORK ! -d $BRIDGE_NETWORK -p udp -j MASQUERADE --to-ports 1024-65535
sudo iptables -t nat -A POSTROUTING -s $BRIDGE_NETWORK ! -d $BRIDGE_NETWORK -j MASQUERADE
echo 1 | sudo tee /proc/sys/net/ipv4/ip_forward
echo

HOST_IFC=$BRIDGE
export HOST_IFC
echo "Host inside network interface is $BRIDGE"
echo

# Setup DHCP server
echo "Network configuration script: DHCP server"
echo "Serving from $BRIDGE_IP, gateway should be $GATEWAY_IP"
echo "dhcpd.conf:"
cat test/dhcpd.conf
echo
sudo cp test/dhcpd.conf /etc/dhcp/dhcpd.conf
sudo chmod a+w /var/lib/dhcp/*
sudo dhcpd mg_bridge0 &
echo
echo "radvd listening at $BRIDGE_IPV6"
sudo ip link set $BRIDGE up # there's no physical port, so we need to set link up for radvd to work
sudo radvd -n -d 5 -C test/radvd.conf &
echo
echo "Host listening at $HOST_IP and $HOST_IPV6"
export HOST_IP
export HOST_IPV6
echo

# Do we have connectivity ?
echo "Check connectivity:"
wget https://cesanta.com/robots.txt
echo robots.txt:
cat  robots.txt
rm   robots.txt
wget https://ipv6.google.com/
rm index.html
echo

# Confirm OK
echo "Done:"
timeout 1s ifconfig       
timeout 1s sudo route -n
timeout 1s bridge fdb
timeout 1s bridge link
timeout 1s sudo ip -6 route show