networks: Prefill proper Wi-Fi device in add form

Add access points found on a particular Wi-Fi device only to that device
as it is not gauranteed that other Wi-Fi devices will be able to find
them.  For example, an access point operating in 5 GHz frequency will
only be found and used by Wi-Fi devices capable for 5 GHz communication.

plinth/modules/networks/networks.py

@@ -354,15 +354,15 @@ def add_pppoe(request):
                              'form': form})
 
 
-def add_wifi(request, ssid=None):
+def add_wifi(request, ssid=None, interface_name=None):
     """Serve wifi connection create form."""
     form = None
     form_data = None
 
     if ssid:
-        device = network.get_first_wifi_device()
+        device = network.get_device_by_interface_name(interface_name)
         form_data = {'name': ssid,
-                     'interface': device,
+                     'interface': interface_name if device else None,
                      'zone': 'external',
                      'ssid': ssid,
                      'mode': 'infrastructure',

plinth/modules/networks/templates/wifi_scan.html

@@ -29,7 +29,7 @@
         <div class="list-group-item clearfix">
           {% if access_point.ssid %}
           <a display="inline-block" width="40%"
-             href="{% url 'networks:add_wifi' access_point.ssid %}">
+             href="{% url 'networks:add_wifi' access_point.ssid access_point.interface_name %}">
              {{ access_point.ssid }}
           </a>
           {% else %}

plinth/modules/networks/urls.py

@@ -37,7 +37,7 @@ urlpatterns = patterns(
     url(r'^sys/networks/add/$', 'add', name='add'),
     url(r'^sys/networks/add/ethernet/$', 'add_ethernet', name='add_ethernet'),
     url(r'^sys/networks/add/pppoe/$', 'add_pppoe', name='add_pppoe'),
-    url(r'^sys/networks/add/wifi/(?:(?P<ssid>[^/]+)/)?$', 'add_wifi',
+    url(r'^sys/networks/add/wifi/(?:(?P<ssid>[^/]+)/(?P<interface_name>[^/]+)/)?$', 'add_wifi',
         name='add_wifi'),
     url(r'^sys/networks/(?P<uuid>[\w.@+-]+)/delete/$',
         'delete', name='delete'),

plinth/network.py

@@ -624,6 +624,7 @@ def wifi_scan():
             ssid = access_point.get_ssid()
             ssid_string = ssid.get_data() if ssid else ''
             access_points.append({
+                'interface_name': device.get_iface(),
                 'ssid': ssid_string,
                 'strength': access_point.get_strength()})