[PATCH v5 13/17] mesh: do not allow pri/sec channel switch

Ben Greear greearb at candelatech.com
Mon Jun 11 11:23:32 PDT 2018

On 06/11/2018 09:55 AM, Jouni Malinen wrote:
> On Thu, May 31, 2018 at 04:19:21PM -0700, Peter Oh wrote:
>> On 05/31/2018 02:07 AM, Jouni Malinen wrote:
>>> On Tue, May 29, 2018 at 02:39:17PM -0700, peter.oh at bowerswilkins.com wrote:
>>>> We don't want mesh to switch the channel from primary to secondary,
>>>> since mesh points are not able to join each other in that case.
>>>> diff --git a/wpa_supplicant/mesh.c b/wpa_supplicant/mesh.c
>>>> @@ -336,7 +336,10 @@ static int wpa_supplicant_mesh_init(struct wpa_supplicant *wpa_s,
>>>> -
>>>> +	/* Do not allow primary/secondary channel switch in mesh mode,
>>>> +	  * since mesh is not able to establish a physical link for it
>>>> +	  */
>>>> +	conf->no_pri_sec_switch = 1;
>>> What do you mean with "a physical link"? Physical?
>> Yes, Physical. the comment will be updated like this in the next revision.
>> +       /* Do not allow primary/secondary channel switch in mesh mode,
>> +        * since mesh is only able to establish Physical link with peers
>> +        * on the same channel.
>> +        */
> What do you mean with "Physical" in this context? Where is physical
> link (or "Physical link"?!) defined? There is no such thing in the IEEE
> 802.11 standard and it would be better to use terms that people can
> understand easily. Maybe just delete "physical"?
> That said, this comment is still quite confusing even if "Physical" were
> removed. Are you trying to say that a link cannot be established if
> different primary channel is used? ".. only able to establishing a link
> with peers using the same primary channel"?

I (and some customers) needed similar behaviour for STA + AP mode in the past, the reason is that
if you know for certain (due to user configuration typically) that a station
has to communicate with an AP on a certain bandwidth, and you want to run an
AP on the same radio, then you cannot have the AP interface using some different center
frequency.  Think police cruisers that need to provide hot-spot sometimes and also
use an STA vdev to connect to head-quarter's AP when in the parking-lot.

With MESH, if you are trying to join some existing mesh on a certain
frequency, it cannot physically work if somehow the hostapd/supplicant decides to use
a different frequency, right?


Ben Greear <greearb at candelatech.com>
Candela Technologies Inc  http://www.candelatech.com

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