command for creating virtual interface

Jithu Jance jithujance at gmail.com
Mon Oct 27 10:41:08 EDT 2014


Hi Jouni,

Thanks for the inputs. Please find my comments inline.

>That patch seems to be adding only WPA_IF_STATION type interfaces which
would be fine for another station, but maybe not ideal for AP.

Yes. But by setting an AP profile (mode=2), we should be able change
the role to AP (I tried locally and it works). Having an AP
concurrently with STA restricts the operation to same channel
concurrency though.

>Could you please clarify why this functionality should be in wpa_supplicant?
This would enable us to have an additional wireless IP connection
(another STA-AP) to another device while the primary STA interface is
being used for internet connectivity. Since it is the standard virtual
STA functionality being added, I thought it is good to add support in
the supplicant.

Basically the sequence I thought of is like as below.

interface_create //creates a virtual network interface
interface_add //initializes the interface with appropriate conf file
interface_remove // de-initializes the interface
interface_del // deletes the network interface.

The virtual interface creation part can be integrated to already
existing "interface_add" command by adding an additional argument.  I
just kept the commands separate for testing and getting the initial
feedback.

>Since driver_nl80211.c is tracking interfaces added and removed through
if_add() and if_remove() some of these operations triggered by external
control could result in unexpected results. As such, this does not look
like the safest way of addressing a need to add/remove a virtual
interface for independent of internal wpa_supplicant needs.

It might be useful to get the internal status of the peer STA
interface for later optimizations (to force single channel concurrency
in case of role change to AP). since interface_add is getting called,
the newly added STA initialization and connection is controlled via
supplicant. so internal tracking is useful for this case as well,
right?

Can some additional checks help to address the safety concern? Like
for e.g, adding code to remove the externally added interfaces in case
of a terminate signal.


Thanks,


- Jithu Jance




On Sat, Oct 25, 2014 at 9:21 PM, Jouni Malinen <j at w1.fi> wrote:
> On Wed, Oct 22, 2014 at 01:18:35PM +0530, Jithu Jance wrote:
>> Could you share your thoughts on having commands for virtual interface
>> creation and deletion?
>>
>> I have submitted a patch for the same:
>> http://patchwork.ozlabs.org/patch/351403/
>>
>> The purpose is to create a virtual interface for a secondary STA or
>> supplicant based AP interface on the fly.
>
> That patch seems to be adding only WPA_IF_STATION type interfaces which
> would be fine for another station, but maybe not ideal for AP. Could you
> please clarify why this functionality should be in wpa_supplicant?
>
> Since driver_nl80211.c is tracking interfaces added and removed through
> if_add() and if_remove() some of these operations triggered by external
> control could result in unexpected results. As such, this does not look
> like the safest way of addressing a need to add/remove a virtual
> interface for independent of internal wpa_supplicant needs. If I
> understood the use case correctly, doing this without storing any state
> in driver_nl80211.c for the interface that was used to remove/add and
> interface could be more appropriate for this.
>
> --
> Jouni Malinen                                            PGP id EFC895FA
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