#!/usr/bin/env sh
#
# This injects hooks into the network management service of the
# droplet with content to add routes into host for vpc peering.

peering_route_script='/var/lib/cloud/scripts/peering.sh'

# Detects the network service used by the system
detect_network_service () {
        if systemctl --quiet is-active NetworkManager; then
                netsvc='NetworkManager'
        elif systemctl --quiet is-active systemd-networkd; then
                netsvc='networkd'
        elif systemctl --quiet is-active networking; then
                netsvc='ifupdown'
        else
                >&2 echo "Unable to detect network service to properly inject vpc peering routes"
                exit 1
        fi
}

# Place the peering script in peering_route_script location
place_route_injection_script() {
        cat > "$peering_route_script" << 'EOM'
#!/bin/sh

for i in $(seq 1 10); do
    VPC_PEERING_ENABLED=$(curl -fs --connect-timeout 5 169.254.169.254/metadata/v1/features/vpc_peering_enabled)
    if [ $? -ne 0 ]; then
        sleep 5
        continue
    fi

    if [ "${VPC_PEERING_ENABLED}" != "true" ]; then
        exit 0
    fi

    VPC_GATEWAY_IP=$(curl -fs --connect-timeout 5 169.254.169.254/metadata/v1/interfaces/private/0/ipv4/gateway)
    if [ $? -ne 0 ]; then
        sleep 5
        continue
    fi

    ip route replace 192.168.0.0/16 via "${VPC_GATEWAY_IP}" dev eth1 mtu 1500 metric 101 && \
        ip route replace 10.0.0.0/8 via "${VPC_GATEWAY_IP}" dev eth1 mtu 1500 metric 101 && \
        ip route replace 172.16.0.0/12 via "${VPC_GATEWAY_IP}" dev eth1 mtu 1500 metric 101;
    if [ $? -eq 0 ]; then
        exit 0
    fi

    sleep 5
done

exit 1
EOM

        chmod +x "$peering_route_script"
}

# Inject hook into /etc/network/if-up.d/
inject_ifupdown() {
        cat > /etc/network/if-up.d/vpc-peering << EOM
#!/bin/sh

[ "\$IFACE" = "eth1" ] && ${peering_route_script}

exit 0
EOM

        chmod +x /etc/network/if-up.d/vpc-peering
        "$peering_route_script"
}

# Inject hook into /etc/NetworkManager/dispatcher.d/
inject_network_manager() {
        cat > /etc/NetworkManager/dispatcher.d/vpc-peering << EOM
#!/bin/sh

interface=\$1
event=\$2

if [ "\$interface" != "eth1" ] || [ "\$event" != "up" ]; then
        exit 0
fi

${peering_route_script}
EOM

        chmod +x /etc/NetworkManager/dispatcher.d/vpc-peering
        "$peering_route_script"
}

# systemd-networkd does not supports hooks, we inject a oneshot
# systemd unit that is invoked after eth0/1 is online and if systemd-networkd restarts.
inject_networkd() {
        cat > /etc/systemd/system/vpc-peering.service << EOM
[Unit]
Description=VPC Peering Route Injection
Requires=systemd-networkd-wait-online.service systemd-networkd.service
After=systemd-networkd-wait-online.service systemd-networkd.service
PartOf=systemd-networkd.service

[Service]
Type=oneshot
ExecStart=${peering_route_script}
RemainAfterExit=yes

[Install]
WantedBy=multi-user.target
EOM

        systemctl daemon-reload
        systemctl enable --now vpc-peering.service
}

detect_network_service
place_route_injection_script

case $netsvc in
        ifupdown) inject_ifupdown ;;
        networkd) inject_networkd ;;
        NetworkManager) inject_network_manager ;;
esac