virtual-deployment/libvirt/config.py

#!/usr/bin/python3

import ipaddress
import sys
import yaml

# Interface names are limited to 15 characters. 5 are reserved for VLANS
# ('.####'), it also add a single digit for the four enumerated bridges
# of the virtual lab. Meaning that 9 characters are left for the end
# user to choose.

BRIDGE_LIMIT = 9

# Fields that should be set in a Yaml configuration file

GEN_FIELDS = ('bridge_interface', 'controller', 'worker',
              'domain_dir', 'storage')

IP_FIELDS = ('ext_network', 'ext_IP')

NODES_NUM = ('worker_nodes_num', 'storage_nodes_num')

FIELDS = GEN_FIELDS + IP_FIELDS + NODES_NUM


# Allows the user to see how this script is used
def print_help():
    print("use: ./config.py <config_file> <key>"
          " or use: ./config.py --validate <config_file>",
          file=sys.stderr)


# Checks if there are any unexpected fields in the file
def existence_check(data):
    for key in data:
        if key not in FIELDS:
            print('unexpected field: %s' % key)


# Opens the config file and returns its contents
def reader(config_file):
    try:
        with open(config_file, 'r', encoding="utf-8") as f:
            content = yaml.load(f, Loader=yaml.Loader)

        return content

    except yaml.YAMLError as e:
        print('YAMLError: %s' % e, file=sys.stderr)
        sys.exit(1)
    except OSError as e:
        print('OSError: %s' % e, file=sys.stderr)
        sys.exit(1)


# Allows the user to check if their configuration values
# exist and are valid
def validator(config_file):

    ERROR = 0

    data = reader(config_file)

    existence_check(data)

    # For every field checks if they exist and has various checks to
    # ensure all values are valid
    for field in FIELDS:

        try:
            value = data[field]
        except KeyError:
            print(' %s does not exist' % field)
            ERROR += 1
            continue

        # Checking that most fields are alphanumerical
        if (field in GEN_FIELDS):

            # Checks if bridge_interface is smaller that nine
            # characters long

            if (field == 'bridge_interface' and len(value) > BRIDGE_LIMIT):

                print(field + ' variable too long')
                ERROR += 1

            if value.isalnum() is False:
                print(field + ' is not alphanumerical')
                ERROR += 1

        # Checking that there are valid IPv4 addresses
        elif (field in IP_FIELDS):
            # Removing the /24 subnet mask
            try:
                IP, netmask = value.split('/')
            except ValueError:
                print(field + ' does not look like IP/mask', file=sys.stderr)
                ERROR += 1
                continue

            try:
                netmask = int(netmask)
            except ValueError:
                print(field + ': not a valid netmask')
                ERROR += 1

            try:
                ipaddress.ip_address(IP)
            except (ValueError):
                print(field + ' is not a valid IP address', file=sys.stderr)
                ERROR += 1

        # Checking that node counts are numbers
        elif (field in NODES_NUM):
            try:
                int(value)
            except ValueError:
                print(field + ' does not have an integer', file=sys.stderr)
                ERROR += 1

    if ERROR > 0:
        print('total errors: %s ' % ERROR)
        sys.exit(1)


# Allows the user to read any value in their configuration file
def readvalue(config_file, key):
    data = reader(config_file)

    try:
        value = data[key]
        print(value)

    except KeyError as e:
        print('KeyError: %s' % e, file=sys.stderr)


if __name__ == "__main__":
    args = sys.argv[1:]

    if '--help' in args:
        print_help()
        sys.exit(0)

    if '--validate' == args[0]:
        if len(args) == 2:
            validator(args[1])
            sys.exit(0)

        else:
            print('Validate requires only one parameter: config_file',
                  file=sys.stderr)
            print_help()
            sys.exit(1)

    if len(args) == 2:
        input_file = args[0]
        input_key = args[1]
        readvalue(input_file, input_key)

    elif len(args) < 2:
        print("Error: missing required arguments.",
              file=sys.stderr)
        print_help()
        sys.exit(1)

    else:
        print("Error: too many arguments.",
              file=sys.stderr)
        print_help()
        sys.exit(1)