#! /bin/bash

# - Take over 10.11.0.1.
# - Force default route to NordLynx 

TOR_GW="172.20.0.111"
VPN_GW="172.20.0.254"
GOOD_ROUTES+=("10.11.0.0/16")
GOOD_ROUTES+=("10.111.0.0/16") # TOR
GOOD_ROUTES+=("172.20.0.0/24") # VPN gateways
GOOD_ROUTES+=("172.20.1.0/24")
GOOD_ROUTES+=("172.22.0.0/24")
GOOD_ROUTES+=("172.23.0.0/24")
GOOD_ROUTES+=("172.28.0.0/24")

# https://en.wikipedia.org/wiki/Reserved_IP_addresses
BAD_ROUTES+=("0.0.0.0/8")
BAD_ROUTES+=("10.0.0.0/8")
BAD_ROUTES+=("172.16.0.0/12")
BAD_ROUTES+=("100.64.0.0/10")
BAD_ROUTES+=("169.254.0.0/16")
BAD_ROUTES+=("192.0.0.0/24")
BAD_ROUTES+=("192.0.2.0/24")
BAD_ROUTES+=("192.88.99.0/24")
BAD_ROUTES+=("192.168.0.0/16")
BAD_ROUTES+=("198.18.0.0/15")
BAD_ROUTES+=("198.51.100.0/15")
BAD_ROUTES+=("203.0.113.0/24")
BAD_ROUTES+=("224.0.0.0/4")
BAD_ROUTES+=("233.252.0.0/24")
BAD_ROUTES+=("240.0.0.0/24")
BAD_ROUTES+=("255.255.255.255/32")

blacklist_routes()
{
	for ip in "${GOOD_ROUTES[@]}"; do
		iptables -A FORWARD -d "$ip" -j ACCEPT
	done

	for ip in "${BAD_ROUTES[@]}"; do
		iptables -A FORWARD -d "$ip" -j REJECT
	done
}

devbyip()
{
	local dev
	dev="$(ip addr show | grep -F "inet $1" | head -n1 | awk '{print $7;}')"
	[[ -n $dev ]] && { echo "$dev"; return; }
	echo -e >&2 "DEV for '${1}' not found. Using $2"
	echo "${2:?}"
}

# Stop routing via VPN
vpn_unset()
{
	ip route del default via "${VPN_GW}"
}

# Start routing via VPN
vpn_set()
{
	ip route add default via "${VPN_GW}"
}

tor_unset()
{
	unset IS_SET_TOR
	ip route del default via "${TOR_GW}"
}

tor_set()
{
	IS_SET_TOR=1
	ip route add default via "${TOR_GW}"
}

monitor_failover()
{
	# ts=$(date +%s)

	while :; do
		if [[ -n $IS_SET_TOR ]]; then
			# HERE: TOR is set
			if [[ -f /config/guest/vpn_status ]]; then
				# HERE: VPN is back
				echo -e >&2 "$(date) WARN: Switching route to VPN."
				tor_unset
				vpn_set
			fi
		else
			# HERE: TOR is NOT set
			# Run a ping test. On failure 
			if [[ ! -f /config/guest/vpn_status ]]; then
				# HERE: VPN is gone
				echo -e >&2 "$(date) WARN: Switching route to TOR."
				vpn_unset
				tor_set
			fi
		fi
		bash -c "exec -a '[sleep router failover]' sleep 5"
	done
}

DEV_I22="$(devbyip 172.28.0. eth0)"

DEV="$(devbyip 10.11. eth1)"

DEV_SSHD="$(devbyip 172.22.0. eth2)"

DEV_GW="$(devbyip 172.20.0. eth3)"

DEV_DMZ="$(devbyip 172.20.1. eth4)"

[[ -n $SF_DEBUG ]] && {
	ip link show >&2
	ip addr show >&2
	ip route show >&2

	echo >&2 "DEV=${DEV} DEV_GW=${DEV_GW}"
}

blacklist_routes

ip route del default && \
# -----BEGIN SSH traffic is routed via Internet-----
# A bit more tricky to forward incoming SSH traffic to our SSHD
# because we also like to see the source IP (User's Workstation's IP).
#
# Must rp_filter=2 (see docker-compose.yml)
# # iptables -t raw -A PREROUTING -p tcp -d 172.20.0.2 --dport 22 -j TRACE
# # iptables -t raw -L -v -n --line-numbers
# # modprobe nf_log_ipv4 && sysctl net.netfilter.nf_log.2=nf_log_ipv4
# - iptables -L PREROUTING -t mangle -n
# - ip rule show
# - ip route show table 207
# Forward all SSHD traffic to sf-host:22.
iptables -A PREROUTING -i ${DEV_I22} -t mangle -p tcp -d 172.28.0.2 --dport 22 -j MARK --set-mark 722 && \
ip rule add fwmark 722 table 207 && \
ip route add default via 172.22.0.22 dev ${DEV_SSHD} table 207 && \

# Any return traffic from the SSHD shall go out (directly) to the Internet.
iptables -A PREROUTING -i ${DEV_SSHD} -t mangle -p tcp -s 172.22.0.22 --sport 22 -j MARK --set-mark 22 && \
ip rule add fwmark 22 table 201 && \
ip route add default via 172.28.0.1 dev ${DEV_I22} table 201 && \

# Forward packets to SSHD (172.22.0.22)
iptables -t nat -A PREROUTING -p tcp -d 172.28.0.2 --dport 22 -j DNAT --to-destination 172.22.0.22 && \
# Make packets appear as if this router was listening on port 22
iptables -t nat -A POSTROUTING -p tcp -s 172.22.0.22 --sport 22 -j SNAT --to-source 172.28.0.2 && \
# When connecting from Docker's host:
# Note: Traffic from router to shell leaves with src=172.28.0.1 and dst=172.22.0.22
# However, at the SSHD they appear to be comming from src=172.22.0.254 because
# Docker's host side bridge performs NAT. On the SSHD side we can not send
# the traffic back to 172.28.0.1 (via 172.22.0.254; this router) because both share the
# same MAC.
# Instead use a hack to force traffic from 172.28.0.1 to be coming
# from 172.22.0.254 (This router's IP)
iptables -t nat -A POSTROUTING -s 172.28.0.1 -o ${DEV_SSHD} -j MASQUERADE && \
# -----END SSH traffic is routed via Internet-----

# -----BEGIN GSNC traffic is routed via Internet----
# GSNC TCP traffic to 443 and 7350 goes to (direct) Internet
iptables -A PREROUTING -i ${DEV_SSHD} -t mangle -p tcp -s 172.22.0.21 -j MARK --set-mark 22
# -----END GSNC traffic is routed via Internet----

ifconfig "$DEV" 10.11.0.1/16 && \
# MASQ all traffic because the VPN/TOR instances dont know the route back
# to sf-guest (10.11.0.0/16).
iptables -t nat -A POSTROUTING -o "${DEV_GW}" -j MASQUERADE && \
# MASQ SSHD's access to DNS (for ssh -D socks5h resolving)
iptables -t nat -A POSTROUTING -s 172.22.0.22 -o "${DEV}" -j MASQUERADE && \
# MASQ GSNC to (direct) Internet
iptables -t nat -A POSTROUTING -s 172.22.0.21 -o "${DEV_I22}" -j MASQUERADE && \
# MASQ traffic from TOR to DMZ (nginx)
iptables -t nat -A POSTROUTING -o "${DEV_DMZ}" -j MASQUERADE && \
# TOR traffic (10.111.0.0/16) always goes to TOR (transparent proxy)
ip route add 10.111.0.0/16 via "${TOR_GW}" && \
echo -e >&2 "FW: SUCCESS" && \
/tc.sh "${DEV}" "${DEV_GW}" "${DEV_I22}" && \
echo -e >&2 "TC: SUCCESS" && \

# By default go via TOR until vpn_status exists
tor_set && \
monitor_failover

# REACHED IF ANY CMD FAILS
ip route del default
echo -e >&2 "FAILED to set routes"
exit 250