Only open the NETLINK interface when needed

Do not open a NETLINK connection when loading the module, but rahter
open it when needed.  In a case where multiple users needs the
connection, it will be shared and only closed when the last active
user is done.

Signed-off-by: David Sommerseth <davids@redhat.com>

Author: David Sommerseth

python-ethtool/etherinfo.c

@@ -1,6 +1,6 @@
 /* etherinfo.c - Retrieve ethernet interface info via NETLINK
  *
- * Copyright (C) 2009-2010 Red Hat Inc.
+ * Copyright (C) 2009-2011 Red Hat Inc.
  *
  * David Sommerseth <davids@redhat.com>
  * Parts of this code is based on ideas and solutions in iproute2
@@ -27,9 +27,12 @@
 #include <netlink/route/rtnl.h>
 #include <assert.h>
 #include <errno.h>
+#include <pthread.h>
 #include "etherinfo_struct.h"
 #include "etherinfo.h"
 
+pthread_mutex_t nlc_counter_mtx = PTHREAD_MUTEX_INITIALIZER;
+
 /*
  *
  *   Internal functions for working with struct etherinfo
@@ -274,15 +277,25 @@ void dump_etherinfo(FILE *fp, struct etherinfo *ptr)
  *
  * @return Returns 1 on success, otherwise 0.
  */
-int get_etherinfo(struct etherinfo *ethinf, struct nl_handle *nlc, nlQuery query)
+int get_etherinfo(struct etherinfo_obj_data *data, nlQuery query)
 {
 	struct nl_cache *link_cache;
 	struct nl_cache *addr_cache;
 	struct rtnl_addr *addr;
 	struct rtnl_link *link;
+	struct etherinfo *ethinf = NULL;
 	int ret = 0;
 
-	if( !ethinf || !nlc ) {
+	if( !data || !data->ethinfo ) {
+		return 0;
+	}
+	ethinf = data->ethinfo;
+
+	/* Open a NETLINK connection on-the-fly */
+	if( !open_netlink(data) ) {
+		PyErr_Format(PyExc_RuntimeError,
+			     "Could not open a NETLINK connection for %s",
+			     ethinf->device);
 		return 0;
 	}
 
@@ -291,7 +304,7 @@ int get_etherinfo(struct etherinfo *ethinf, struct nl_handle *nlc, nlQuery query
 	 * interface index if we have that
 	 */
 	if( ethinf->index < 0 ) {
-		link_cache = rtnl_link_alloc_cache(nlc);
+		link_cache = rtnl_link_alloc_cache(*data->nlc);
 		ethinf->index = rtnl_link_name2i(link_cache, ethinf->device);
 		if( ethinf->index < 0 ) {
 			return 0;
@@ -303,7 +316,7 @@ int get_etherinfo(struct etherinfo *ethinf, struct nl_handle *nlc, nlQuery query
 	switch( query ) {
 	case NLQRY_LINK:
 		/* Extract MAC/hardware address of the interface */
-		link_cache = rtnl_link_alloc_cache(nlc);
+		link_cache = rtnl_link_alloc_cache(*data->nlc);
 		link = rtnl_link_alloc();
 		rtnl_link_set_ifindex(link, ethinf->index);
 		nl_cache_foreach_filter(link_cache, (struct nl_object *)link, callback_nl_link, ethinf);
@@ -314,7 +327,7 @@ int get_etherinfo(struct etherinfo *ethinf, struct nl_handle *nlc, nlQuery query
 
 	case NLQRY_ADDR:
 		/* Extract IP address information */
-		addr_cache = rtnl_addr_alloc_cache(nlc);
+		addr_cache = rtnl_addr_alloc_cache(*data->nlc);
 		addr = rtnl_addr_alloc();
 		rtnl_addr_set_ifindex(addr, ethinf->index);
 
@@ -337,3 +350,75 @@ int get_etherinfo(struct etherinfo *ethinf, struct nl_handle *nlc, nlQuery query
 	return ret;
 }
 
+
+/**
+ * Connects to the NETLINK interface.  This will be called
+ * for each etherinfo object being generated, and it will
+ * keep a separate file descriptor open for each object
+ *
+ * @param data etherinfo_obj_data structure
+ *
+ * @return Returns 1 on success, otherwise 0.
+ */
+int open_netlink(struct etherinfo_obj_data *data)
+{
+	if( !data ) {
+		return 0;
+	}
+
+	/* Reuse already established NETLINK connection, if a connection exists */
+	if( *data->nlc ) {
+		/* If this object has not used NETLINK earlier, tag it as a user */
+		if( !data->nlc_active ) {
+			pthread_mutex_lock(&nlc_counter_mtx);
+			(*data->nlc_users)++;
+			pthread_mutex_unlock(&nlc_counter_mtx);
+		}
+		data->nlc_active = 1;
+		return 1;
+	}
+
+	/* No earlier connections exists, establish a new one */
+	*data->nlc = nl_handle_alloc();
+	nl_connect(*data->nlc, NETLINK_ROUTE);
+	if( (*data->nlc != NULL) ) {
+		/* Tag this object as an active user */
+		pthread_mutex_lock(&nlc_counter_mtx);
+		(*data->nlc_users)++;
+		pthread_mutex_unlock(&nlc_counter_mtx);
+		data->nlc_active = 1;
+		return 1;
+	} else {
+		return 0;
+	}
+}
+
+
+/**
+ * Closes the NETLINK connection.  This should be called automatically whenever
+ * the corresponding etherinfo object is deleted.
+ *
+ * @param ptr  Pointer to the pointer of struct nl_handle, which contains the NETLINK connection
+ */
+void close_netlink(struct etherinfo_obj_data *data)
+{
+	if( !data || !(*data->nlc) ) {
+		return;
+	}
+
+	/* Untag this object as a NETLINK user */
+	data->nlc_active = 0;
+	pthread_mutex_lock(&nlc_counter_mtx);
+	(*data->nlc_users)--;
+	pthread_mutex_unlock(&nlc_counter_mtx);
+
+	/* Don't close the connection if there are more users */
+	if( *data->nlc_users > 0) {
+		return;
+	}
+
+	/* Close NETLINK connection */
+	nl_close(*data->nlc);
+	nl_handle_destroy(*data->nlc);
+	*data->nlc = NULL;
+}

python-ethtool/etherinfo.h

@@ -1,6 +1,6 @@
 /* etherinfo.h - Retrieve ethernet interface info via NETLINK
  *
- * Copyright (C) 2009-2010 Red Hat Inc.
+ * Copyright (C) 2009-2011 Red Hat Inc.
  *
  * David Sommerseth <davids@redhat.com>
  *
@@ -26,10 +26,13 @@
 
 typedef enum {NLQRY_LINK, NLQRY_ADDR} nlQuery; /**<  Supported query types in the etherinfo code */
 
-int get_etherinfo(struct etherinfo *ethinf, struct nl_handle *nlc, nlQuery query);
+int get_etherinfo(struct etherinfo_obj_data *data, nlQuery query);
 void free_etherinfo(struct etherinfo *ptr);
 void dump_etherinfo(FILE *, struct etherinfo *);
 
 void free_ipv6addresses(struct ipv6address *ptr);
 
+int open_netlink(struct etherinfo_obj_data *);
+void close_netlink(struct etherinfo_obj_data *);
+
 #endif

python-ethtool/etherinfo_obj.c

@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2009-2010 Red Hat Inc.
+ * Copyright (C) 2009-2011 Red Hat Inc.
  *
  * David Sommerseth <davids@redhat.com>
  *
@@ -40,6 +40,8 @@ extern PyTypeObject ethtool_etherinfoIPv6Type;
 void _ethtool_etherinfo_dealloc(etherinfo_py *self)
 {
 	if( self->data ) {
+		close_netlink(self->data);
+
 		if( self->data->ethinfo ) {
 			free_etherinfo(self->data->ethinfo);
 		}
@@ -110,20 +112,21 @@ PyObject *_ethtool_etherinfo_getter(etherinfo_py *self, PyObject *attr_o)
 	if( strcmp(attr, "device") == 0 ) {
 		ret = RETURN_STRING(self->data->ethinfo->device);
 	} else if( strcmp(attr, "mac_address") == 0 ) {
-		get_etherinfo(self->data->ethinfo, self->data->nlc, NLQRY_LINK);
+		get_etherinfo(self->data, NLQRY_LINK);
 		ret = RETURN_STRING(self->data->ethinfo->hwaddress);
 	} else if( strcmp(attr, "ipv4_address") == 0 ) {
-		get_etherinfo(self->data->ethinfo, self->data->nlc, NLQRY_ADDR);
+		get_etherinfo(self->data, NLQRY_ADDR);
 		ret = RETURN_STRING(self->data->ethinfo->ipv4_address);
 	} else if( strcmp(attr, "ipv4_netmask") == 0 ) {
-		get_etherinfo(self->data->ethinfo, self->data->nlc, NLQRY_ADDR);
+		get_etherinfo(self->data, NLQRY_ADDR);
 		ret = PyInt_FromLong(self->data->ethinfo->ipv4_netmask);
 	} else if( strcmp(attr, "ipv4_broadcast") == 0 ) {
-		get_etherinfo(self->data->ethinfo, self->data->nlc, NLQRY_ADDR);
+		get_etherinfo(self->data, NLQRY_ADDR);
 		ret = RETURN_STRING(self->data->ethinfo->ipv4_broadcast);
 	} else {
 		ret = PyObject_GenericGetAttr((PyObject *)self, attr_o);
 	}
+
 	return ret;
 }
 
@@ -160,8 +163,8 @@ PyObject *_ethtool_etherinfo_str(etherinfo_py *self)
 		return NULL;
 	}
 
-	get_etherinfo(self->data->ethinfo, self->data->nlc, NLQRY_LINK);
-	get_etherinfo(self->data->ethinfo, self->data->nlc, NLQRY_ADDR);
+	get_etherinfo(self->data, NLQRY_LINK);
+	get_etherinfo(self->data, NLQRY_ADDR);
 
 	ret = PyString_FromFormat("Device %s:\n", self->data->ethinfo->device);
 	if( self->data->ethinfo->hwaddress ) {
@@ -223,7 +226,7 @@ PyObject * _ethtool_etherinfo_get_ipv6_addresses(etherinfo_py *self, PyObject *n
 		return NULL;
 	}
 
-	get_etherinfo(self->data->ethinfo, self->data->nlc, NLQRY_ADDR);
+	get_etherinfo(self->data, NLQRY_ADDR);
 	ipv6 = self->data->ethinfo->ipv6_addresses;
 	ret = PyTuple_New(1);
 	if( !ret ) {

python-ethtool/etherinfo_struct.h

@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2009-2010 Red Hat Inc.
+ * Copyright (C) 2009-2011 Red Hat Inc.
  *
  * David Sommerseth <davids@redhat.com>
  *
@@ -58,7 +58,9 @@ struct ipv6address {
  *
  */
 struct etherinfo_obj_data {
-	struct nl_handle *nlc;          /**< Contains NETLINK connection info */
+	struct nl_handle **nlc;         /**< Contains NETLINK connection info (global) */
+	unsigned int *nlc_users;	/**< Resource counter for the NETLINK connection (global) */
+	unsigned short nlc_active;	/**< Is this instance using NETLINK? */
 	struct etherinfo *ethinfo;      /**< Contains info about our current interface */
 };
 

python-ethtool/ethtool.c

@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2008-2010 Red Hat Inc.
+ * Copyright (C) 2008-2011 Red Hat Inc.
  *
  * Arnaldo Carvalho de Melo <acme@redhat.com>
  * David Sommerseth <davids@redhat.com>
@@ -32,6 +32,7 @@
 #include "etherinfo.h"
 
 static struct nl_handle *nlconnection = NULL;
+unsigned int nlconnection_users = 0;  /* How many NETLINK users are active? */
 extern PyTypeObject ethtool_etherinfoType;
 extern PyTypeObject ethtool_etherinfoIPv6Type;
 
@@ -314,7 +315,8 @@ static PyObject *get_interfaces_info(PyObject *self __unused, PyObject *args) {
 		 */
 		objdata->ethinfo->device = strdup(fetch_devs[i]);
 		objdata->ethinfo->index = -1;
-		objdata->nlc = nlconnection; /* Global variable */
+		objdata->nlc = &nlconnection;
+		objdata->nlc_users = &nlconnection_users;
 
 		/* Instantiate a new etherinfo object with the device information */
 		ethinf_py = PyCObject_FromVoidPtr(objdata, NULL);
@@ -979,52 +981,6 @@ static struct PyMethodDef PyEthModuleMethods[] = {
 };
 
 
-/**
- * Connects to the NETLINK interface.  This should only be
- * called once as part of the main ethtool module init.
- *
- * @param nlc Structure which keeps the NETLINK connection handle (struct nl_handle)
- *
- * @return Returns 1 on success, otherwise 0.
- */
-int open_netlink(struct nl_handle **nlc)
-{
-	if( *nlc ) {
-		return 0;
-	}
-
-	*nlc = nl_handle_alloc();
-	nl_connect(*nlc, NETLINK_ROUTE);
-	return (*nlc != NULL);
-}
-
-
-/**
- * Closes the NETLINK connection.  This should be called automatically whenever
- * the ethtool module is unloaded from Python.
- *
- * @param ptr  Pointer to the pointer of struct nl_handle, which contains the NETLINK connection
- */
-void close_netlink(void **ptr)
-{
-	struct nl_handle *nlc;
-
-	if( !ptr && !*ptr ) {
-		return;
-	}
-
-	nlc = (struct nl_handle *) *ptr;
-	if( !nlc ) {
-		return;
-	}
-
-	/* Close NETLINK connection */
-	nl_close(nlc);
-	nl_handle_destroy(nlc);
-	*ptr = NULL; /* reset the pointers pointer address */
-}
-
-
 PyMODINIT_FUNC initethtool(void)
 {
 	PyObject *m;
@@ -1042,12 +998,6 @@ PyMODINIT_FUNC initethtool(void)
 	Py_INCREF(&ethtool_etherinfoIPv6Type);
 	PyModule_AddObject(m, "etherinfo_ipv6addr", (PyObject *)&ethtool_etherinfoIPv6Type);
 
-	// Prepare an internal netlink connection object
-	if( open_netlink(&nlconnection) ) {
-		PyModule_AddObject(m, "__nlconnection",
-				   PyCObject_FromVoidPtr(&nlconnection, close_netlink));
-	}
-
 	// Setup constants
 	PyModule_AddIntConstant(m, "IFF_UP", IFF_UP);			/* Interface is up. */
 	PyModule_AddIntConstant(m, "IFF_BROADCAST", IFF_BROADCAST);	/* Broadcast address valid. */

setup.py

@@ -4,7 +4,7 @@
 import commands
 import sys
 
-version = '0.6'
+version = '0.7'
 
 ethtool = Extension('ethtool',
 		    sources = ['python-ethtool/ethtool.c',
@@ -53,8 +53,8 @@ def _str2list(pkgstr, onlystr):
 setup(name='ethtool',
       version=version,
       description='Python module to interface with ethtool',
-      author='Harald Hoyer & Arnaldo Carvalho de Melo',
-      author_email='acme@redhat.com',
+      author='Harald Hoyer, Arnaldo Carvalho de Melo, David Sommerseth',
+      author_email='davids@redhat.com',
       url='http://fedoraproject.org/wiki/python-ethtool',
       ext_modules=[
         Extension(