Parsers

linuxnet.qos uses a number of parser classes to parse the output of the tc(8) command:

• QDiscParser

• QClassParser

• TrafficFilterParser

The following classes are also used in parsing:

• QDiscOutput

• QClassOutput

• FilterOutput

• FilterOutputLine

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Queuing discipline parsing

The QDiscParser class is responsible for parsing the output of tc -s qdisc ls dev <interface>.

The QDiscParser.register_qdisc() method must be invoked to register queueing discipline classes.

class QDiscParser(allow_parsing_errors: bool)

Helper class that creates QDisc objects from the output of the tc(8) command.

classmethod register_qdisc(ident: str, klass) → None

Register the given class (which should be a subclass of the QDisc class).

This method is intended to be used for adding support for new queuing disciplines.

Parameters:

• ident – the qdisc name that appears in the tc -s qdisc ls output.

• klass – the Python class for this queuing discipline

class QDiscOutput(line_group: List[str])

Helper class used for parsing tc qdisc ls output for a single qdisc

Parameters:

line_group – list of lines, guaranteed not to be empty

get_handle() → Handle

Returns the (parsed) Handle of the queuing discipline.

get_parent_handle() → Optional[Handle]

Returns the (parsed) Handle of the parent of this queueing discipline, or None if this is a root qdisc

get_refcnt() → Optional[int]

Returns reference count of qdisc (None for non-root qdiscs, and for some root qdiscs like mq)

get_qdisc_line() → str

Returns the tc(8) output qdisc line

get_field_iter() → Iterator[str]

Return an iterator for the (remaining) fields of the qdisc line

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Queuing class parsing

The QClassParser class is responsible for parsing the output of tc -s class ls dev <interface>.

The QClassParser.register_qclass() method must be invoked to register Python classes providing support for classes of classful queueing disciplines.

class QClassParser(allow_parsing_errors: bool)

Helper class that creates QClass objects from the output of the tc(8) command.

classmethod register_qclass(ident: str, klass) → None

Register the given class (which should be a subclass of the QClass class).

This method is intended to be used for adding support for new queuing discipline classes.

Parameters:

• ident – the queuing class name that appears in the tc -s class ls output.

• klass – the Python class for this queuing class

class QClassOutput(line_group: List[str])

Helper class used for parsing tc class ls output for a single qclass

Parameters:

line_group – list of lines, guaranteed not to be empty

get_handle() → Handle

Returns the (parsed) Handle of the queuing class.

get_parent_handle() → Handle

Returns the (parsed) Handle of the parent of the queuing class.

get_qdisc_handle() → Optional[Handle]

Returns the Handle of a (leaf) qdisc

get_class_line() → str

Returns the tc(8) output class line

get_field_iter() → Iterator[str]

Return an iterator for the (remaining) fields of the class line

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Traffic filter parsing

The TrafficFilterParser class is responsible for parsing the output of tc -s filter ls dev <interface>.

The TrafficFilterParser.register_filter() method must be invoked to register classes traffic filter classes.

class TrafficFilterParser(allow_parsing_errors: bool)

Helper class that creates TrafficFilter objects from the output of the tc(8) command.

classmethod register_filter(*, filter_type: str, protocol: str, klass) → None

Register the given class (which should be a subclass of the TrafficFilter class).

This method is intended to be used for adding support for new traffic filter types.

Parameters:

• filter_type – a tc(8) filter type, e.g. u32

• protocol – a tc(8) protocol name, e.g. ip

• klass – the Python class for this (filter_type, protocol)

classmethod register_action(*, action_name: str, klass) → None

Register the given class (which should be a subclass of the TrafficAction class).

This method is intended to be used for adding support for new traffic actions.

Parameters:

• action_name – tc(8) action, e.g. police

• klass – the Python class for this action

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class FilterOutput(proto: str, prio: int, filter_type: str, owner: QNode)

An instance of this class contains the tc(8) output for a single filter. This includes the filter description lines, followed by action description lines. The lines are grouped, with groups separated by empty lines. The first line group contains the filter lines. Each successive line group describes an action.

Parameters:

• proto – filter protocol

• prio – filter priority

• filter_type – filter type

• owner – QDisc/QClass that owns the filter

get_prio() → int

Returns the priority value

get_proto() → str

Returns the protocol value

get_filter_type() → str

Returns the filter type

get_filter_owner() → QNode

Returns the QDisc/QClass that owns the filter

get_first_line() → str

Returns the first line from the tc(8) output for this filter

has_nonfilter_lines() → bool

Returns True if the filter output has any lines not starting with the word filter

action_in_filter_line(action_fields: List[str]) → None

This method can be used by a filter parser to indicate that an action is part of a filter line (happens with the fw filter). The rest of the lines, if any, are assumed to be action-related lines.

filter_lines_iter() → Iterator[FilterOutputLine]

Returns an iterator that returns FilterOutputLine instances.

nonfilter_lines_iter() → LineGroupIterator

Returns an iterator that returns lines (strings). The same iterator instance is always returned.

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class FilterOutputLine(line: str, fields: List[str])

A class that holds a line of filter output.

One can iterate over the fields of the line:

def parse_fields(fline: FilterOutputLine):
    for field in fline:
        if field == 'xxx':
            ...

The entire line can be returned by using the str() builtin function.

Parameters:

• line – the complete tc(8) filter line

• fields – list of fields of the line after the filter type