[Click] How to write to /proc in a click element

[Javier Sánchez]

Hi Robert,

Are u sure on this?

Packets for monitor device comes from ieee80211_output.c ->
ieee80211_monitor_encap()

on this function the channel value is not processed into
ieee80211_phy_params ph, for example:

rate is processed:

case IEEE80211_RADIOTAP_RATE:
ph->rate0 = *p;
p++;
break;


channel is not processed:

case IEEE80211_RADIOTAP_CHANNEL:
/* 2 x 16-bit */
p = start + roundup(p - start, 2) + 4;
break;

Regards
Javier


On Mon, Jul 27, 2009 at 5:49 PM, Robert
Sombrutzki<sombrutz at informatik.hu-berlin.de> wrote:
> Hi,
> i think, it's not the best way to use a sysctl to set the channel, because you
> can not control which packets are sent on which channel, since you have
> several queues. Example: you have packet a and b , you want to sent packet a
> on channel 1 and b on 2. How do you want to control that the new channel is
> set between these two packets ? Of course, you can delay packet b until the
> new channel is set, but that has no good performance. I think it better to
> set the channel using an annotation on the packet. You can extend the
> ath-header (use AthdescEncap) with an extra field for the channel, which
> should used for the packet. In the madwifi-driver (e.g. in
> ieee80211_output.c), you check for the encap-type, the field in the header
> and the channel and switch to the new channel ( struct ieee80211com includes
> pointer to the channel-switch-function: ic_set_channel). The problem here is,
> that you have to sent a packet to switch the channel, but therefor it is
> precise. To switch the channel without transmitting a packet, you can
> generate a packet which just initiates the changing the channel, but which is
> discard by the driver afterwards. According to the channel you can mark such
> kind of packets using an extention to the ath-header.
> I use this solution and it works well.
>
> Regards,
> Robert
>>Hi,
>>
>>Can someone please advise me how to write something in /proc/sys in a click
>>event? I need to change the channel in MadWifi upon reception of a control
>>packet. I am planning on writing a sysctl handler in madwifi to change the
>>channel upon request, and I need to trigger it using Click. If someone has a
>>better suggestion to do this - I'll be glad to know!
>>
>>Thanks for your help and time.
>>
>>Ashish
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