<filename>ovs_dbg/filter.py
""" Defines a Flow Filtering syntax
"""
import pyparsing as pp
import netaddr
from functools import reduce
from operator import and_, or_

from ovs_dbg.decoders import (
    decode_default,
    decode_int,
    Decoder,
    IPMask,
    EthMask,
)


class EvaluationResult:
    """An EvaluationResult is the result of an evaluation. It contains the
    boolean result and the list of key-values that were evaluated

    Note that since boolean operations (and, not, or) are based only on
    __bool__ we use bitwise alternatives (&, ||, ~)
    """

    def __init__(self, result, *kv):
        self.result = result
        self.kv = kv if kv else list()

    def __and__(self, other):
        """Logical and operation"""
        return EvaluationResult(
            self.result and other.result, *self.kv, *other.kv
        )

    def __or__(self, other):
        """Logical or operation"""
        return EvaluationResult(
            self.result or other.result, *self.kv, *other.kv
        )

    def __invert__(self):
        """Logical not operation"""
        return EvaluationResult(not self.result, *self.kv)

    def __bool__(self):
        """Boolean operation"""
        return self.result

    def __repr__(self):
        return "{} [{}]".format(self.result, self.kv)


class ClauseExpression:
    operators = {}
    type_decoders = {
        int: decode_int,
        netaddr.IPAddress: IPMask,
        netaddr.EUI: EthMask,
        bool: bool,
    }

    def __init__(self, tokens):
        self.field = tokens[0]
        self.value = ""
        self.operator = ""

        if len(tokens) > 1:
            self.operator = tokens[1]
            self.value = tokens[2]

    def __repr__(self):
        return "{}(field: {}, operator: {}, value: {})".format(
            self.__class__.__name__, self.field, self.operator, self.value
        )

    def _find_data_in_kv(self, kv_list):
        """Find a KeyValue for evaluation in a list of KeyValue

        Args:
            kv_list (list[KeyValue]): list of KeyValue to look into

        Returns:
            If found, tuple (kv, data) where kv is the KeyValue that matched
            and data is the data to be used for evaluation. None if not found.
        """
        key_parts = self.field.split(".")
        field = key_parts[0]
        kvs = [kv for kv in kv_list if kv.key == field]
        if not kvs:
            return None

        for kv in kvs:
            if kv.key == self.field:
                # exact match
                return (kv, kv.value)
            if len(key_parts) > 1:
                data = kv.value
                for subkey in key_parts[1:]:
                    try:
                        data = data.get(subkey)
                    except Exception:
                        data = None
                        break
                    if not data:
                        break
                if data:
                    return (kv, data)
        return None

    def _find_keyval_to_evaluate(self, flow):
        """Finds the key-value and data to use for evaluation on a flow

        Args:
            flow(Flow): The flow where the lookup is performed

        Returns:
            If found, tuple (kv, data) where kv is the KeyValue that matched
            and data is the data to be used for evaluation. None if not found.

        """
        for section in flow.sections:
            data = self._find_data_in_kv(section.data)
            if data:
                return data
        return None

    def evaluate(self, flow):
        """
        Return whether the clause is satisfied by the flow

        Args:
            flow (Flow): the flow to evaluate
        """
        result = self._find_keyval_to_evaluate(flow)

        if not result:
            return EvaluationResult(False)

        keyval, data = result

        if not self.value and not self.operator:
            # just asserting the existance of the key
            return EvaluationResult(True, keyval)

        # Decode the value based on the type of data
        if isinstance(data, Decoder):
            decoder = data.__class__
        else:
            decoder = self.type_decoders.get(data.__class__) or decode_default

        decoded_value = decoder(self.value)

        if self.operator == "=":
            return EvaluationResult(decoded_value == data, keyval)
        elif self.operator == "<":
            return EvaluationResult(data < decoded_value, keyval)
        elif self.operator == ">":
            return EvaluationResult(data > decoded_value, keyval)
        elif self.operator == "~=":
            return EvaluationResult(decoded_value in data, keyval)


class BoolNot:
    def __init__(self, t):
        self.op, self.args = t[0]

    def __repr__(self):
        return "NOT({})".format(self.args)

    def evaluate(self, flow):
        return ~self.args.evaluate(flow)


class BoolAnd:
    def __init__(self, pattern):
        self.args = pattern[0][0::2]

    def __repr__(self):
        return "AND({})".format(self.args)

    def evaluate(self, flow):
        return reduce(and_, [arg.evaluate(flow) for arg in self.args])


class BoolOr:
    def __init__(self, pattern):
        self.args = pattern[0][0::2]

    def evaluate(self, flow):
        return reduce(or_, [arg.evaluate(flow) for arg in self.args])

    def __repr__(self):
        return "OR({})".format(self.args)


class OFFilter:
    w = pp.Word(pp.alphanums + "." + ":" + "_" + "/" + "-")
    operators = (
        pp.Literal("=")
        | pp.Literal("~=")
        | pp.Literal("<")
        | pp.Literal(">")
        | pp.Literal("!=")
    )

    clause = (w + operators + w) | w
    clause.setParseAction(ClauseExpression)

    statement = pp.infixNotation(
        clause,
        [
            ("!", 1, pp.opAssoc.RIGHT, BoolNot),
            ("not", 1, pp.opAssoc.RIGHT, BoolNot),
            ("&&", 2, pp.opAssoc.LEFT, BoolAnd),
            ("and", 2, pp.opAssoc.LEFT, BoolAnd),
            ("||", 2, pp.opAssoc.LEFT, BoolOr),
            ("or", 2, pp.opAssoc.LEFT, BoolOr),
        ],
    )

    def __init__(self, expr):
        self._filter = self.statement.parseString(expr)

    def evaluate(self, flow):
        return self._filter[0].evaluate(flow)

<filename>ovs_dbg/filter.py
""" Defines a Flow Filtering syntax
"""
import pyparsing as pp
import netaddr
from functools import reduce
from operator import and_, or_

from ovs_dbg.decoders import (
    decode_default,
    decode_int,
    Decoder,
    IPMask,
    EthMask,
)


class EvaluationResult:
    """An EvaluationResult is the result of an evaluation. It contains the
    boolean result and the list of key-values that were evaluated

    Note that since boolean operations (and, not, or) are based only on
    __bool__ we use bitwise alternatives (&, ||, ~)
    """

    def __init__(self, result, *kv):
        self.result = result
        self.kv = kv if kv else list()

    def __and__(self, other):
        """Logical and operation"""
        return EvaluationResult(
            self.result and other.result, *self.kv, *other.kv
        )

    def __or__(self, other):
        """Logical or operation"""
        return EvaluationResult(
            self.result or other.result, *self.kv, *other.kv
        )

    def __invert__(self):
        """Logical not operation"""
        return EvaluationResult(not self.result, *self.kv)

    def __bool__(self):
        """Boolean operation"""
        return self.result

    def __repr__(self):
        return "{} [{}]".format(self.result, self.kv)


class ClauseExpression:
    operators = {}
    type_decoders = {
        int: decode_int,
        netaddr.IPAddress: IPMask,
        netaddr.EUI: EthMask,
        bool: bool,
    }

    def __init__(self, tokens):
        self.field = tokens[0]
        self.value = ""
        self.operator = ""

        if len(tokens) > 1:
            self.operator = tokens[1]
            self.value = tokens[2]

    def __repr__(self):
        return "{}(field: {}, operator: {}, value: {})".format(
            self.__class__.__name__, self.field, self.operator, self.value
        )

    def _find_data_in_kv(self, kv_list):
        """Find a KeyValue for evaluation in a list of KeyValue

        Args:
            kv_list (list[KeyValue]): list of KeyValue to look into

        Returns:
            If found, tuple (kv, data) where kv is the KeyValue that matched
            and data is the data to be used for evaluation. None if not found.
        """
        key_parts = self.field.split(".")
        field = key_parts[0]
        kvs = [kv for kv in kv_list if kv.key == field]
        if not kvs:
            return None

        for kv in kvs:
            if kv.key == self.field:
                # exact match
                return (kv, kv.value)
            if len(key_parts) > 1:
                data = kv.value
                for subkey in key_parts[1:]:
                    try:
                        data = data.get(subkey)
                    except Exception:
                        data = None
                        break
                    if not data:
                        break
                if data:
                    return (kv, data)
        return None

    def _find_keyval_to_evaluate(self, flow):
        """Finds the key-value and data to use for evaluation on a flow

        Args:
            flow(Flow): The flow where the lookup is performed

        Returns:
            If found, tuple (kv, data) where kv is the KeyValue that matched
            and data is the data to be used for evaluation. None if not found.

        """
        for section in flow.sections:
            data = self._find_data_in_kv(section.data)
            if data:
                return data
        return None

    def evaluate(self, flow):
        """
        Return whether the clause is satisfied by the flow

        Args:
            flow (Flow): the flow to evaluate
        """
        result = self._find_keyval_to_evaluate(flow)

        if not result:
            return EvaluationResult(False)

        keyval, data = result

        if not self.value and not self.operator:
            # just asserting the existance of the key
            return EvaluationResult(True, keyval)

        # Decode the value based on the type of data
        if isinstance(data, Decoder):
            decoder = data.__class__
        else:
            decoder = self.type_decoders.get(data.__class__) or decode_default

        decoded_value = decoder(self.value)

        if self.operator == "=":
            return EvaluationResult(decoded_value == data, keyval)
        elif self.operator == "<":
            return EvaluationResult(data < decoded_value, keyval)
        elif self.operator == ">":
            return EvaluationResult(data > decoded_value, keyval)
        elif self.operator == "~=":
            return EvaluationResult(decoded_value in data, keyval)


class BoolNot:
    def __init__(self, t):
        self.op, self.args = t[0]

    def __repr__(self):
        return "NOT({})".format(self.args)

    def evaluate(self, flow):
        return ~self.args.evaluate(flow)


class BoolAnd:
    def __init__(self, pattern):
        self.args = pattern[0][0::2]

    def __repr__(self):
        return "AND({})".format(self.args)

    def evaluate(self, flow):
        return reduce(and_, [arg.evaluate(flow) for arg in self.args])


class BoolOr:
    def __init__(self, pattern):
        self.args = pattern[0][0::2]

    def evaluate(self, flow):
        return reduce(or_, [arg.evaluate(flow) for arg in self.args])

    def __repr__(self):
        return "OR({})".format(self.args)


class OFFilter:
    w = pp.Word(pp.alphanums + "." + ":" + "_" + "/" + "-")
    operators = (
        pp.Literal("=")
        | pp.Literal("~=")
        | pp.Literal("<")
        | pp.Literal(">")
        | pp.Literal("!=")
    )

    clause = (w + operators + w) | w
    clause.setParseAction(ClauseExpression)

    statement = pp.infixNotation(
        clause,
        [
            ("!", 1, pp.opAssoc.RIGHT, BoolNot),
            ("not", 1, pp.opAssoc.RIGHT, BoolNot),
            ("&&", 2, pp.opAssoc.LEFT, BoolAnd),
            ("and", 2, pp.opAssoc.LEFT, BoolAnd),
            ("||", 2, pp.opAssoc.LEFT, BoolOr),
            ("or", 2, pp.opAssoc.LEFT, BoolOr),
        ],
    )

    def __init__(self, expr):
        self._filter = self.statement.parseString(expr)

    def evaluate(self, flow):
        return self._filter[0].evaluate(flow)

Defines a Flow Filtering syntax An EvaluationResult is the result of an evaluation. It contains the     boolean result and the list of key-values that were evaluated      Note that since boolean operations (and, not, or) are based only on     __bool__ we use bitwise alternatives (&, ||, ~) Logical and operation Logical or operation Logical not operation Boolean operation Find a KeyValue for evaluation in a list of KeyValue          Args:             kv_list (list[KeyValue]): list of KeyValue to look into          Returns:             If found, tuple (kv, data) where kv is the KeyValue that matched             and data is the data to be used for evaluation. None if not found. # exact match Finds the key-value and data to use for evaluation on a flow          Args:             flow(Flow): The flow where the lookup is performed          Returns:             If found, tuple (kv, data) where kv is the KeyValue that matched             and data is the data to be used for evaluation. None if not found. Return whether the clause is satisfied by the flow          Args:             flow (Flow): the flow to evaluate # just asserting the existance of the key # Decode the value based on the type of data