flowspec.py

import re

from flowapp.constants import MAX_PORT

NUMBER = re.compile(r"^\d+$", re.IGNORECASE)
RANGE = re.compile(r"^(\d+)-(\d+)$", re.IGNORECASE)
NOTRAN = re.compile(r"^>=(\d+)&<=(\d+)$", re.IGNORECASE)
GREATER = re.compile(r">[=]?(\d+)$", re.IGNORECASE)
LOWER = re.compile(r"<[=]?(\d+)$", re.IGNORECASE)


def translate_sequence(sequence, max_val=MAX_PORT):
    """
    translate command sequence sepparated by ; to ExaBGP command format
    @param string sequence
    @param integer max_val
    @return string ExaBgp rule string
    """
    result = [to_exabgp_string(item, max_val) for item in sequence.split(";") if item]
    result = " ".join(result)
    return "[{}]".format(result)


def to_exabgp_string(value_string, max_val):
    """
    Translate form string to flowspec value or packet size rule
    @param string value_string
    @param integer max_val
    @return string ExaBgp rule string
    @raises ValueError

    x (integer)  to =x
    x-y  to >=x&<=y
    >=x&<=y to >=x&<=y
    >x to >=x&<=MAX
    >=x to >=x&<=MAX
    <x to >=0&<=x
    <=x to >=0&<=x
    """
    # simple number
    if NUMBER.match(value_string):
        return "={}".format(check_limit(value_string, max_val))
    elif RANGE.match(value_string):
        m = RANGE.match(value_string)
        return ">={}&<={}".format(
            check_limit(m.group(1), max_val), check_limit(m.group(2), max_val)
        )
    elif NOTRAN.match(value_string):
        return value_string
    elif GREATER.match(value_string):
        m = GREATER.match(value_string)
        return ">={}&<={}".format(check_limit(m.group(1), max_val), max_val)
    elif LOWER.match(value_string):
        m = LOWER.match(value_string)
        return ">=0&<={}".format(check_limit(m.group(1), max_val))
    else:
        raise ValueError("string {} can not be converted".format(value_string))


def check_limit(value, max_value):
    """
    test if the value is lower than max_value
    raise exception otherwise
    """
    value = int(value)
    if value > max_value:
        raise ValueError(
            "Invalid value number: {} is too big. Max is {}.".format(value, max_value)
        )
    else:
        return value


def filter_rules_action(user_actions, rules):
    """
    Divide the list of rules by user_actions to editable and viewonly subsets
    :param user_actions: list of actions allowed for normal user
    :param rules: list of rules to be filtered
    :return: editable, viewonly lists
    """
    editable = []
    viewonly = []
    for rule in rules:
        if rule.action_id in user_actions:
            editable.append(rule)
        else:
            viewonly.append(rule)

    return editable, viewonly