setup-network

#!/run/current-system/sw/bin/bash

set -u

## Inspect what we can
echo "Inspecting eth0 and eth1..."
interfaces=/etc/network/interfaces
gateway=$(grep gateway "$interfaces" | awk '{print $2}')
ns1=$(grep "dns-nameservers" "$interfaces" | awk '{print $2}')
ns2=$(grep "dns-nameservers" "$interfaces" | awk '{print $3}')

eth0_enabled=$(grep eth0 "$interfaces")
eth0_address=$(grep address "$interfaces" | awk '{print $2}' | head -1)
eth0_prefix_length=$(grep -Eo "/..?" "$interfaces" | sed 's_/__' | head -1)

eth1_enabled=$(grep eth1 "$interfaces")
eth1_address=$(grep address "$interfaces" | awk '{print $2}' | tail -1)
eth1_prefix_length=$(grep -Eo "/..?" "$interfaces" | sed 's_/__' | tail -1)

## Takes 1) interface name; 2) address; 3) prefix length
function enable_interface
{
  echo "Enabling $1..."
  ip link set "$1" up
  ip addr add "$2/$3" dev "$1"
}

## Takes 1) nameserver 1; 2) nameserver 2; 3) gateway
function enable_dns
{
  echo "Enabling DNS..."
  resolvconf -m 1 -a static <<EOF
  nameserver $1
  nameserver $2
EOF
  ip route add default via "$3" || true
}

[ -n "$eth0_enabled" ] && enable_interface eth0 "$eth0_address" "$eth0_prefix_length"
[ -n "$eth1_enabled" ] && enable_interface eth1 "$eth1_address" "$eth1_prefix_length"

# NixOS 16.03 uses newer naming
[ -n "$eth0_enabled" ] && enable_interface enp0s3 "$eth0_address" "$eth0_prefix_length"
[ -n "$eth1_enabled" ] && enable_interface enp0s4 "$eth1_address" "$eth1_prefix_length"

# NixOS 17.09 uses newer naming
[ -n "$eth0_enabled" ] && enable_interface ens3 "$eth0_address" "$eth0_prefix_length"
[ -n "$eth1_enabled" ] && enable_interface ens8 "$eth1_address" "$eth1_prefix_length"

enable_dns "$ns1" "$ns2" "$gateway"

echo "All set!"

## Example data:
#iface eth0 inet static
#        address 188.166.222.72
#        netmask 255.255.240.0
#        gateway 188.166.208.1
#        up ip addr add 10.15.0.7/16 dev eth0
#        dns-nameservers 8.8.8.8 8.8.4.4