NixOps migration script for https://github.com/NixOS/nixops/pull/1032

nixops-migrate-hetzner-no-local-commands-json.py

#!/usr/bin/env python3
import argparse
import copy
import json
import sys


def migrate(input_dict):
  j = copy.deepcopy(input_dict)

  net = j['networking']

  defgw_ip_str = net['defaultGateway']
  iface = list(net['interfaces'])[0]
  ipv4 = net['interfaces'][iface]['ipAddress']
  prefixLength_v4 = net['interfaces'][iface]['prefixLength']
  # Expected syntax:
  #   ip -6 addr add '2a01:4f8:192:5292::/64' dev 'eth0' || true
  #                      ^ field index 4
  ipv6_lines = [l for l in net['localCommands'].strip().split('\n') if l.startswith('ip -6')]
  ipv6_with_slash = ipv6_lines[0].split(' ')[4].strip("'")
  ipv6, prefixLength_v6_str = ipv6_with_slash.split('/')
  prefixLength_v6 = int(prefixLength_v6_str)

  # Delete localCommands
  del net['localCommands']

  # Add v4 gateway with interface device
  net['defaultGateway'] = {
    'interface': iface,
    'address': defgw_ip_str,
  }
  # Add v6 gateway with interface device
  net['defaultGateway6'] = {
    'interface': iface,
    'address': 'fe80::1',
  }
  # Move addresses to new interfaces.<iface>.ipv*.addresses = [{address, prefixLength}] style
  net['interfaces'][iface] = {
    "ipv4": {
      "addresses": [
        {
          "address": ipv4,
          "prefixLength": prefixLength_v4,
        }
      ]
    },
    "ipv6": {
      "addresses": [
        {
          "address": ipv6,
          "prefixLength": prefixLength_v6,
        }
      ]
    },
  }
  return j


# Example network spec in JSON format
example_json = '''
{
  "services": {
    "udev": {
      "extraRules": "ACTION==\\"add\\", SUBSYSTEM==\\"net\\", ATTR{address}==\\"00:1a:2b:3c:4d:5e\\", NAME=\\"eth0\\"\\n"
    }
  },
  "networking": {
    "nameservers": [
      "213.133.98.98",
      "213.133.99.99",
      "213.133.100.100",
      "2a01:4f8:0:a0a1::add:1010",
      "2a01:4f8:0:a102::add:9999",
      "2a01:4f8:0:a111::add:9898"
    ],
    "interfaces": {
      "eth0": {
        "prefixLength": 27,
        "ipAddress": "1.2.3.190"
      }
    },
    "defaultGateway": "1.2.3.161",
    "localCommands": "ip -6 addr add '2a01:4f8:123:4567::/64' dev 'eth0' || true\\nip -4 route change '1.2.3.160/27' via '1.2.3.161' dev 'eth0' || true\\nip -6 route add default via 'fe80::1' dev eth0 || true\\n"
  }
}
'''


def main():
  parser = argparse.ArgumentParser(description='Transform NixOps Hetzner network spec JSON from NixOS 17.09 ipAddress format to new NixOS 18.03 format')
  parser.add_argument('--file', metavar='FILE', help='JSON file to process')
  args = parser.parse_args()

  if args.file is None:
    j = json.loads(example_json)
    print('Example file output:')
  else:
    with open(args.file) as f:
      j = json.load(f)

  migrated_json = migrate(j)

  print(json.dumps(migrated_json, indent=2))


if __name__ == '__main__':
  main()