network-config-template-engine/engine.py

# Config Generator
# Written by Hex Ripley
import re
import ipaddress
 
#### Regex Templates ####
 
# Valid IP/CIDR notation pattern
ip_cidr_pattern = re.compile(r'^(\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}|\[?[a-fA-F0-9:\.]+\]?)\/(\d{1,2})$') # Regex identifies valid ip/cidr input
# use with ValueError | if ip_cidr_pattern.match(ip_cidr):
# when building       |     ...
# interpreters and    | else:
# evaluators          |    raise ValueError("Invalid IP/CIDR notation")
 
# Valid JUNOS interface pattern E.G. ae0 or xe-0/1/2
interface_pattern = re.compile(r'^(ae[0-9]{1,2}|[gx]e-[0-9]\/[0-9]\/[0-9])$')
 
#### Input interpreters ####
 
def get_cidr(ip_cidr): # Grab the CIDR notation off a user's input
    if ip_cidr_pattern.match(ip_cidr):
        network = ipaddress.ip_network(ip_cidr, strict=False)
        prefix_length = network.prefixlen
        return prefix_length
    else:
        raise ValueError("Invalid ip/cidr notation on get_cidr call")
 
def get_network_block(ip_cidr): # If the user gives an address that is not the network address, find the network address.
    if ip_cidr_pattern.match(ip_cidr):
        network = ipaddress.ip_network(ip_cidr, strict=False)
        network_address = network.network_address
        prefix_length = network.prefixlen
        network_block = f"{network_address}/{prefix_length}"
        return network_block
    else:
        raise ValueError("Invalid ip/cidr notation on get_network_block call")
 
def get_next_ip_in_subnet(ip_cidr): # Return the next IP within the subnet
    if ip_cidr_pattern.match(ip_cidr):
        network = ipaddress.ip_network(ip_cidr, strict=False)
        ip = ipaddress.ip_address(ip_cidr.split('/')[0])
        if ip == network.broadcast_address:
            raise ValueError("IP address is the broadcast address; no next IP in the subnet.")
        next_ip = ip + 1
        if next_ip in network: # Make sure next IP is within subnet
            return f"{next_ip}/{network.prefixlen}"
        else:
            raise ValueError("Next IP address is outside the subnet.")
 
#### Evaluator Engine ####
 
def template_engine(config_data_template): # Does the work!
    data_strings = {}
    template_strings = config_data_template["template_output"]
    evaluation_functions = config_data_template["evaluation_functions"]
    interpreter_functions = config_data_template["interpreter_functions"]
     
    for evaluator in evaluation_functions.items():
        template_string = evaluator[0]
        prompt_and_evaluator = evaluator[1]
        evaluated_input = get_valid_input(prompt_and_evaluator[0],prompt_and_evaluator[1])
        data_strings[template_string] = evaluated_input
     
    for interpreter in interpreter_functions.items():
        template_string = interpreter[0]
        interpreter_and_key = interpreter[1]
        interpreted_value = interpreter_and_key[0](data_strings[interpreter_and_key[1]])
        data_strings[template_string] = interpreted_value
     
    adjusted_strings = replace_target_words(template_strings,data_strings)
    print("\n ---- \n")
    for string in adjusted_strings:
        print(string)
    print("\n")
 
def replace_target_words(strings, replacements): # Function to replace words in a string
    def replace_in_string(s):
        # Find all target words in braces (e.g., {word})
        return re.sub(r'\{([a-zA-Z0-9_]+)\}', lambda match: replacements.get(match.group(1), match.group(1)), s)
 
    # Apply replacement to all strings
    return [replace_in_string(s) for s in strings]
 
def get_valid_input(prompt, eval_func): # Input validater, does not proceed until validation function is satisfied.
    while True:
        user_input = input(prompt+" > ")
        try:
            # Attempt to evaluate the input using the provided function
            result = eval_func(user_input)
            return result
        except Exception as e:
            # Print error message and prompt again
            print(f"Invalid input: {e}. Please try again.")
 
#### Evaluator Functions ####
 
def eval_interface(interface): # Check if interface is valid.
    if interface_pattern.match(interface):
        return interface
    else:
        raise ValueError("Invalid Interface: Correct examples ae0, ge-1/2/4")
     
def eval_unit_number(unit_number): # Check if unit number is valid for what we expect to be configured.
    try:
        if unit_number is not None and 0 < int(unit_number) < 30000:
            return unit_number
        else:
            return ValueError()
    except:
        raise ValueError("Invalid Unit Number: Enter a unit greater than 0 and less than 30,000")
     
def eval_access_block(access_block):
    if ip_cidr_pattern.match(access_block):
        return access_block
    else:
        raise ValueError("Invalid ip/cidr notation")
 
def eval_transport_block(transport_block):
    if ip_cidr_pattern.match(transport_block):
        if get_cidr(transport_block) == 64:
            return transport_block
        else:
            raise ValueError("Transport Block CIDR must be 64")
    else:
        raise ValueError("Invalid ip/cidr notation")
 
#### Data Template ####
 
#### Data Templates are a dict with three keys:
 
## template_output ##
 
#template_output is a list of lines of strings containing lines of config with desired variables in braces.
 
## evaluation_functions ##
 
#evaluation_functions is a dict with the keys being the target variable and the values being a list containing the input for the get_valid_input function, which takes the first value as a prompt to show to the user and the second value as an evaluator function to run on the user's input.
 
## interpreter_functions ##
 
#interpreter_functions is a dict with keys being the target variable and the values being a list containing the desired interpreter function and the target value for the interpreter function. The target value for the interpreter function can be the key of a previous evaluation function or previous interpreter_function.
 
config_ipv6_junos = {
"template_output" : [
  "set interfaces {interface} unit {unit_number} family inet6 address {access_first}",
  "set routing-options rib inet6.0 static route {transport_block} next-hop {access_second}",
  "set routing-options rib inet6.0 static route {transport_block} tag 101",
  "set policy-options prefix-list bgp-advertise-v6 {access_block}"
] ,
"evaluation_functions" : {
  "interface" : ["What is the user's interface?",eval_interface],
  "unit_number" : ["What is the user's unit number?",eval_unit_number],
  "access_block" : ["What is the IPv6 Access Block?",eval_access_block],
  "transport_block" : ["What is the IPv6 Transport Block?",eval_transport_block]
} ,
"interpreter_functions" : {
  "access_first" : [get_next_ip_in_subnet,"access_block"],
  "access_second" : [get_next_ip_in_subnet,"access_first"]
} }
 
### Run this example
 
template_engine(config_ipv6_junos)