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

[Robert Sombrutzki]

Hi Javier,
i set the channel in ieee80211_hardstart() before ieee80211_monitor_encap() is 
called:

if (vap->iv_opmode == IEEE80211_M_MONITOR) {
 if ( ( (vap->iv_flags_ext & IEEE80211_FEXT_CHANNELSWITCH) != 0 ) && ( 
skb->dev->type == ARPHRD_IEEE80211_ATHDESC2 ) )
 {
   /*I edit the current channel structure, the other option is to create new 
structure*/
   chan = ic->ic_curchan;
   ath2_h = ( struct ath2_header*)(skb->data + ATHDESC_HEADER_SIZE);
                
   if ( ( ath2_h->anno.tx_anno.channel != 0 ) && ( 
ath2_h->anno.tx_anno.channel != chan->ic_ieee ) ) {
      //printk("channelswitch: %d 
to %d\n",chan->ic_ieee,ath2_h->anno.tx_anno.channel);
      chan->ic_ieee = ath2_h->anno.tx_anno.channel;
      chan->ic_freq = ieee80211_ieee2mhz( chan->ic_ieee , chan->ic_flags);
      //see ieee80211_input.c and what is done here
     ic->ic_set_channel(ic);
   }
   /*end of channel switching*/
 }
 
 ieee80211_monitor_encap(vap, skb);
 ieee80211_parent_queue_xmit(skb);
 return NETDEV_TX_OK;
}

I add a new header-type (ATHDESC2), which is nearly the same as athdesc, but 
with some extention. IEEE80211_FEXT_CHANNELSWITCH is related to a sysctl, 
which i add to control the feature (enable/disable).

Regards
Robert

On Montag, 27. Juli 2009, Javier Sánchez wrote:
> 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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> > click at amsterdam.lcs.mit.edu
> > https://amsterdam.lcs.mit.edu/mailman/listinfo/click