gnlpy: Generic NetLink in PYthon

netlink sockets are used to communicate with various kernel subsystems as an RPC system. man 7 netlink for more information. You can also see a detailed description of how this library works in the documentation for the netlink.py python file.

This project provides a python-only implementation of generic netlink sockets. It was written for ipvs initially, but can be easily adapted to other implementations (taskstats.py is provided as an example).

Example Implementation (taskstats.py)

See linux/Documentation/accounting/taskstats.txt for information about what taskstats actually is and look at taskstats.py for the full implementation.

class Taskstats:
    fields = ['version', 'exitcode', ...]

    def __init__(self, **kwargs):
        self.__dict__.update(kwargs)

    def __repr__(self):
        arr = ['%s=%s' % (f, repr(self.__dict__[f])) for f in self.fields]
        return 'TaskStats(%s)' % ', '.join(arr)

    @staticmethod
    def unpack(val):
        fmt = 'HIBBQQQQQQQQ32sQxxxIIIIIQQQQQQQQQQQQQQQQQQQQQQQ'
        attrs = dict(zip(Taskstats.fields, struct.unpack(fmt, val)))
        assert attrs['version'] == 8, "Bad version: %d" % attrs["version"]
        attrs['comm'] = attrs['comm'].rstrip('\0')
        return Taskstats(**attrs)

TaskstatsType = netlink.create_attr_list_type(
    'TaskstatsType',
    ('PID', netlink.U32Type),
    ('TGID', netlink.U32Type),
    ('STATS', Taskstats),
    ('AGGR_PID', netlink.RecursiveSelf),
    ('AGGR_TGID', netlink.RecursiveSelf),
    ('NULL', netlink.IgnoreType),
)

TaskstatsAttrList = netlink.create_attr_list_type(
    'TaskstatsAttrList',
    ('PID', netlink.U32Type),
    ('TGID', netlink.U32Type),
    ('REGISTER_CPUMASK', netlink.IgnoreType),
    ('DEREGISTER_CPUMASK', netlink.IgnoreType),
)

TaskstatsMessage = netlink.create_genl_message_type(
    'TaskstatsMessage', 'TASKSTATS',
    ('GET', TaskstatsAttrList),
    ('NEW', TaskstatsType),
    required_modules=[],
)

class TaskstatsClient:
    """A python client to interact with taskstats
    """

    def __init__(self, verbose=False):
        self.verbose = verbose
        self.nlsock = netlink.NetlinkSocket()

    def get_pid_stats(self, pid):
        replies = self.nlsock.query(TaskstatsMessage(
            'GET', flags=netlink.MessageFlags.ACK_REQUEST,
            attr_list=TaskstatsAttrList(pid=pid)
        ))
        return replies[0].get_attr_list().get('aggr_pid').get('stats')

Using it (taskstats_dump.py)

from gnlpy.taskstats import TaskstatsClient

def main(argv):
    c = TaskstatsClient()
    stats = c.get_pid_stats(int(argv[1]))
    print(stats)

Contributing

Contribututions to gnlpy are more than welcome. Read the guidelines in CONTRIBUTING.md. Make sure you've signed the CLA before sending in a pull request.

Whitehat

Facebook has a bounty program for the safe disclosure of security bugs. If you find a vulnerability, please go through the process outlined on that page and do not file a public issue.