wifi: don't query nl80211 for non-WiFi devices (bgo #740131)

The upstream kernel added module aliases for nl80211 in commit
fb4e156886ce6e8309e912d8b370d192330d19d3, so querying nl80211
now auto-loads the module.  Previously NM was doing this to
determine whether an ethernet-like device was a Wi-Fi device
that supported nl80211, but this leads to the nl80211 loading
on platforms that will never have or use Wi-Fi.

Since every nl80211-capable device will already have
DEVTYPE=wlan set (from /sys/class/net/wlan0/uevent), we can use
that as an indicator that the ethernet-like device is WiFi
instead of asking nl80211.

https://bugzilla.gnome.org/show_bug.cgi?id=740131

src/platform/nm-linux-platform.c

@@ -766,7 +766,7 @@ link_type_from_udev (NMPlatform *platform, int ifindex, const char *ifname, int
 
 	prop = g_udev_device_get_property (udev_device, "DEVTYPE");
 	sysfs_path = g_udev_device_get_sysfs_path (udev_device);
-	if (g_strcmp0 (prop, "wlan") == 0 || wifi_utils_is_wifi (ifname, sysfs_path))
+	if (wifi_utils_is_wifi (ifname, sysfs_path, prop))
 		return_type (NM_LINK_TYPE_WIFI, "wifi");
 	else if (g_strcmp0 (prop, "wwan") == 0)
 		return_type (NM_LINK_TYPE_WWAN_ETHERNET, "wwan");

src/platform/wifi/wifi-utils-nl80211.c

@@ -934,48 +934,3 @@ error:
 	return NULL;
 }
 
-gboolean
-wifi_nl80211_is_wifi (const char *iface)
-{
-	struct nl_sock *nl_sock;
-	struct nl_cb *nl_cb = NULL;
-	struct nl_msg *msg = NULL;
-	int id, ifindex;
-	struct nl80211_iface_info iface_info = {
-		.mode = NM_802_11_MODE_UNKNOWN,
-	};
-	gboolean is_wifi = FALSE;
-
-	nl_sock = nl_socket_alloc ();
-	if (nl_sock == NULL)
-		return FALSE;
-
-	if (genl_connect (nl_sock))
-		goto error;
-
-	ifindex = nm_platform_link_get_ifindex (iface);
-	if (ifindex < 0)
-		goto error;
-
-	id = genl_ctrl_resolve (nl_sock, "nl80211");
-	if (id < 0)
-		goto error;
-
-	nl_cb = nl_cb_alloc (NL_CB_DEFAULT);
-	if (nl_cb) {
-		msg = _nl80211_alloc_msg (id, ifindex, -1, NL80211_CMD_GET_INTERFACE, 0);
-		if (_nl80211_send_and_recv (nl_sock,
-			                        nl_cb,
-			                        msg,
-			                        nl80211_iface_info_handler,
-			                        &iface_info) >= 0)
-			is_wifi = (iface_info.mode != NM_802_11_MODE_UNKNOWN);
-	}
-
- error:
-	if (nl_cb)
-		nl_cb_put (nl_cb);
-	nl_socket_free (nl_sock);
-	return is_wifi;
-}
-

src/platform/wifi/wifi-utils-nl80211.h

@@ -25,6 +25,4 @@
 
 WifiData *wifi_nl80211_init (const char *iface, int ifindex);
 
-gboolean wifi_nl80211_is_wifi (const char *iface);
-
 #endif  /* __WIFI_UTILS_NL80211_H__ */

src/platform/wifi/wifi-utils.c

@@ -162,13 +162,20 @@ wifi_utils_deinit (WifiData *data)
 }
 
 gboolean
-wifi_utils_is_wifi (const char *iface, const char *sysfs_path)
+wifi_utils_is_wifi (const char *iface, const char *sysfs_path, const char *devtype)
 {
 	char phy80211_path[255];
 	struct stat s;
 
 	g_return_val_if_fail (iface != NULL, FALSE);
 
+	if (g_strcmp0 (devtype, "wlan") == 0) {
+		/* All Wi-Fi drivers should set DEVTYPE=wlan.  Since the kernel's
+		 * cfg80211/nl80211 stack does, this check should match any nl80211
+		 * capable driver (including mac82011-based ones). */
+		return TRUE;
+	}
+
 	if (sysfs_path) {
 		/* Check for nl80211 sysfs paths */
 		g_snprintf (phy80211_path, sizeof (phy80211_path), "%s/phy80211", sysfs_path);
@@ -176,9 +183,6 @@ wifi_utils_is_wifi (const char *iface, const char *sysfs_path)
 			return TRUE;
 	}
 
-	if (wifi_nl80211_is_wifi (iface))
-		return TRUE;
-
 #if HAVE_WEXT
 	if (wifi_wext_is_wifi (iface))
 		return TRUE;

src/platform/wifi/wifi-utils.h

@@ -29,7 +29,7 @@
 
 typedef struct WifiData WifiData;
 
-gboolean wifi_utils_is_wifi (const char *iface, const char *sysfs_path);
+gboolean wifi_utils_is_wifi (const char *iface, const char *sysfs_path, const char *devtype);
 
 WifiData *wifi_utils_init (const char *iface, int ifindex, gboolean check_scan);