From a7c14c842a3bcfdc3bba0dfa1500f6a20902bb46 Mon Sep 17 00:00:00 2001
From: Jason Antman <jason@jasonantman.com>
Date: Sat, 26 Aug 2017 14:29:21 -0400
Subject: [PATCH] fixes #129 - libnethogs support for limiting to specific
 devices

---
 contrib/python-wrapper.py | 46 ++++++++++++++++++++++++++++++++++++---
 src/libnethogs.cpp        | 11 +++++++---
 src/libnethogs.h          | 18 +++++++++++++++
 3 files changed, 69 insertions(+), 6 deletions(-)

diff --git a/contrib/python-wrapper.py b/contrib/python-wrapper.py
index 11f6329..f4e1895 100644
--- a/contrib/python-wrapper.py
+++ b/contrib/python-wrapper.py
@@ -62,7 +62,29 @@ def signal_handler(signal, frame):
     lib.nethogsmonitor_breakloop()
 
 
-def run_monitor_loop(lib):
+def dev_args(devnames):
+    """
+    Return the appropriate ctypes arguments for a device name list, to pass
+    to libnethogs ``nethogsmonitor_loop_devices``. The return value is a
+    2-tuple of devc (``ctypes.c_int``) and devicenames (``ctypes.POINTER``)
+    to an array of ``ctypes.c_char``).
+
+    :param devnames: list of device names to monitor
+    :type devnames: list
+    :return: 2-tuple of devc, devicenames ctypes arguments
+    :rtype: tuple
+    """
+    devc = len(devnames)
+    devnames_type = ctypes.c_char_p * devc
+    devnames_arg = devnames_type()
+    for idx, val in enumerate(devnames):
+        devnames_arg[idx] = (val + chr(0)).encode('ascii')
+    return ctypes.c_int(devc), ctypes.cast(
+        devnames_arg, ctypes.POINTER(ctypes.c_char_p)
+    )
+
+
+def run_monitor_loop(lib, devnames):
     # 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().
@@ -70,7 +92,19 @@ def run_monitor_loop(lib):
     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 len(devnames) < 1:
+        # monitor all devices
+        rc = lib.nethogsmonitor_loop(
+            CALLBACK_FUNC_TYPE(network_activity_callback)
+        )
+    else:
+        devc, devicenames = dev_args(devnames)
+        rc = lib.nethogsmonitor_loop_devices(
+            CALLBACK_FUNC_TYPE(network_activity_callback),
+            devc,
+            devicenames,
+            ctypes.c_bool(False)
+        )
 
     if rc != LoopStatus.OK:
         print('nethogsmonitor_loop returned {}'.format(LoopStatus.MAP[rc]))
@@ -102,7 +136,13 @@ signal.signal(signal.SIGTERM, signal_handler)
 
 lib = ctypes.CDLL(LIBRARY_NAME)
 
-monitor_thread = threading.Thread(target=run_monitor_loop, args=(lib,))
+device_names = []
+# You can use this to monitor only certain devices, like:
+# device_names = ['enp4s0', 'docker0']
+
+monitor_thread = threading.Thread(
+    target=run_monitor_loop, args=(lib, device_names,)
+)
 
 monitor_thread.start()
 
diff --git a/src/libnethogs.cpp b/src/libnethogs.cpp
index 18a30e2..b45ebca 100644
--- a/src/libnethogs.cpp
+++ b/src/libnethogs.cpp
@@ -72,10 +72,10 @@ static bool wait_for_next_trigger() {
   return true;
 }
 
-static int nethogsmonitor_init() {
+static int nethogsmonitor_init(int devc, char **devicenames, bool all) {
   process_init();
 
-  device *devices = get_default_devices();
+  device *devices = get_devices(devc, devicenames, all);
   if (devices == NULL) {
     std::cerr << "No devices to monitor" << std::endl;
     return NETHOGS_STATUS_NO_DEVICE;
@@ -272,11 +272,16 @@ static void nethogsmonitor_clean_up() {
 }
 
 int nethogsmonitor_loop(NethogsMonitorCallback cb) {
+  return nethogsmonitor_loop_devices(cb, 0, NULL, false);
+}
+
+int nethogsmonitor_loop_devices(NethogsMonitorCallback cb,
+                                int devc, char **devicenames, bool all) {
   if (monitor_run_flag) {
     return NETHOGS_STATUS_FAILURE;
   }
 
-  int return_value = nethogsmonitor_init();
+  int return_value = nethogsmonitor_init(devc, devicenames, all);
   if (return_value != NETHOGS_STATUS_OK) {
     return return_value;
   }
diff --git a/src/libnethogs.h b/src/libnethogs.h
index 75340fe..4caacb8 100644
--- a/src/libnethogs.h
+++ b/src/libnethogs.h
@@ -57,6 +57,24 @@ typedef void (*NethogsMonitorCallback)(int action,
 
 NETHOGS_DSO_VISIBLE int nethogsmonitor_loop(NethogsMonitorCallback cb);
 
+/**
+ * @brief Enter the process monitoring loop and reports updates using the
+ * callback provided as parameter. Specify which network devices to monitor.
+ * All parameters other than cb are passed through to get_devices().
+ * This call will block until nethogsmonitor_breakloop() is called or a failure
+ * occurs.
+ * @param cb A pointer to a callback function following the
+ * NethogsMonitorCallback definition
+ * @param devc number of values in devicenames array
+ * @param devicenames pointer to array of devicenames (char arrays)
+ * @param all when false, loopback interface and down/not running interfaces
+ * will be avoided. When true, find all interfaces including down/not running.
+ */
+
+NETHOGS_DSO_VISIBLE int nethogsmonitor_loop_devices(NethogsMonitorCallback cb,
+                                                    int devc, char **devicenames,
+                                                    bool all);
+
 /**
  * @brief Makes the call to nethogsmonitor_loop return.
  */