Add python wrapper by Philip Semanchuk as 'contrib' script

contrib/README.md

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+This folder contains user-contributed scripts.
+
+The Nethogs project does not make claims about the quality of the scripts, maintains
+them in any way, or necessarily think they're a good idea in the first place :).

contrib/python-wrapper.py

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+import ctypes
+import signal
+import datetime
+import threading
+
+# This is a Python 3 demo of how to interact with the Nethogs library via Python. The Nethogs
+# library operates via a callback. The callback implemented here just formats the data it receives
+# and prints it to stdout. This must be run as root (`sudo python3 python-wrapper.py`).
+# By Philip Semanchuk (psemanchuk@caktusgroup.com) November 2016
+# Copyright waived; released into public domain as is.
+
+# The code is multi-threaded to allow it to respond to SIGTERM and SIGINT (Ctrl+C).  In single-
+# threaded mode, while waiting in the Nethogs monitor loop, this Python code won't receive Ctrl+C
+# until network activity occurs and the callback is executed. By using 2 threads, we can have the
+# main thread listen for SIGINT while the secondary thread is blocked in the monitor loop.
+
+
+# LIBRARY_NAME has to be exact, although it doesn't need to include the full path.
+# The version tagged as 0.8.5 (download link below) builds a library with this name.
+# https://github.com/raboof/nethogs/archive/v0.8.5.tar.gz
+LIBRARY_NAME = 'libnethogs.so.0.8.5'
+
+# Here are some definitions from libnethogs.h
+# https://github.com/raboof/nethogs/blob/master/src/libnethogs.h
+# Possible actions are NETHOGS_APP_ACTION_SET & NETHOGS_APP_ACTION_REMOVE
+# Action REMOVE is sent when nethogs decides a connection or a process has died. There are two
+# timeouts defined, PROCESSTIMEOUT (150 seconds) and CONNTIMEOUT (50 seconds). AFAICT, the latter
+# trumps the former so we see a REMOVE action after ~45-50 seconds of inactivity.
+class Action():
+    SET = 1
+    REMOVE = 2
+
+    MAP = {SET: 'SET', REMOVE: 'REMOVE'}
+
+class LoopStatus():
+    """Return codes from nethogsmonitor_loop()"""
+    OK = 0
+    FAILURE = 1
+    NO_DEVICE = 2
+
+    MAP = {OK: 'OK', FAILURE: 'FAILURE', NO_DEVICE: 'NO_DEVICE'}
+
+# The sent/received KB/sec values are averaged over 5 seconds; see PERIOD in nethogs.h.
+# https://github.com/raboof/nethogs/blob/master/src/nethogs.h#L43
+# sent_bytes and recv_bytes are a running total
+class NethogsMonitorRecord(ctypes.Structure):
+    """ctypes version of the struct of the same name from libnethogs.h"""
+    _fields_ = (('record_id', ctypes.c_int),
+                ('name', ctypes.c_char_p),
+                ('pid', ctypes.c_int),
+                ('uid', ctypes.c_uint32),
+                ('device_name', ctypes.c_char_p),
+                ('sent_bytes', ctypes.c_uint32),
+                ('recv_bytes', ctypes.c_uint32),
+                ('sent_kbs', ctypes.c_float),
+                ('recv_kbs', ctypes.c_float),
+                )
+
+
+def signal_handler(signal, frame):
+    print('SIGINT received; requesting exit from monitor loop.')
+    lib.nethogsmonitor_breakloop()
+
+
+def run_monitor_loop(lib):
+    # Create a type for my callback func. The callback func returns void (None), and accepts as
+    # params an int and a pointer to a NethogsMonitorRecord instance.
+    # The params and return type of the callback function are mandated by nethogsmonitor_loop().
+    # See libnethogs.h.
+    CALLBACK_FUNC_TYPE = ctypes.CFUNCTYPE(ctypes.c_void_p, ctypes.c_int,
+                                          ctypes.POINTER(NethogsMonitorRecord))
+
+    rc = lib.nethogsmonitor_loop(CALLBACK_FUNC_TYPE(network_activity_callback))
+
+    if rc != LoopStatus.OK:
+        print('nethogsmonitor_loop returned {}'.format(LoopStatus.MAP[rc]))
+    else:
+        print('exiting monitor loop')
+
+
+def network_activity_callback(action, data):
+    print(datetime.datetime.now().strftime('@%H:%M:%S.%f'))
+
+    # Action type is either SET or REMOVE. I have never seen nethogs send an unknown action
+    # type, and I don't expect it to do so.
+    action_type = Action.MAP.get(action, 'Unknown')
+
+    print('Action: {}'.format(action_type))
+    print('Record id: {}'.format(data.contents.record_id))
+    print('Name: {}'.format(data.contents.name))
+    print('PID: {}'.format(data.contents.pid))
+    print('UID: {}'.format(data.contents.uid))
+    print('Device name: {}'.format(data.contents.device_name.decode('ascii')))
+    print('Sent/Recv bytes: {} / {}'.format(data.contents.sent_bytes, data.contents.recv_bytes))
+    print('Sent/Recv kbs: {} / {}'.format(data.contents.sent_kbs, data.contents.recv_kbs))
+    print('-' * 30)
+
+#############       Main begins here      ##############
+
+signal.signal(signal.SIGINT, signal_handler)
+signal.signal(signal.SIGTERM, signal_handler)
+
+lib = ctypes.CDLL(LIBRARY_NAME)
+
+monitor_thread = threading.Thread(target=run_monitor_loop, args=(lib,))
+
+monitor_thread.start()
+
+done = False
+while not done:
+    monitor_thread.join(0.3)
+    done = not monitor_thread.is_alive()