Re: [PATCH] Implementation of the IEEE80211_RADIOTAP_RATE option

["Gábor Stefanik" <netrolller.3d@gmail.com>]

On Fri, Aug 21, 2009 at 10:18 AM, Johannes
Berg<johannes@sipsolutions.net> wrote:
> On Thu, 2009-08-20 at 17:40 -0700, Rafael Laufer wrote:
>> This patch implements the IEEE80211_RADIOTAP_RATE
>> option when parsing radiotap headers to allow rate
>> selection on a per-packet basis.
>>
>>
>> Signed-off-by: Rafael Laufer <rlaufer@cs.ucla.edu>
>> ---
>>  Implementation of the IEEE80211_RADIOTAP_RATE
>>  option when parsing radiotap headers to allow
>>  rate selection on a per-packet basis.
>>
>>  net/mac80211/tx.c |   18 +++++++++++++++++-
>>  1 files changed, 17 insertions(+), 1 deletions(-)
>>
>> diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c
>> index 10a1099..41d636b 100644
>> --- a/net/mac80211/tx.c
>> +++ b/net/mac80211/tx.c
>> @@ -549,7 +549,10 @@ ieee80211_tx_h_rate_ctrl(struct ieee80211_tx_data *tx)
>>        * If we're associated with the sta at this point we know we can at
>>        * least send the frame at the lowest bit rate.
>>        */
>> -     rate_control_get_rate(tx->sdata, tx->sta, &txrc);
>> +
>> +     /* in monitor mode, we already have the rate from the radiotap header */
>> +     if (likely(!(info->flags & IEEE80211_TX_CTL_INJECTED)))
>> +             rate_control_get_rate(tx->sdata, tx->sta, &txrc);
>
> NAK, the rate is optional in the radiotap header, and if not given then
> regular rate control must be used.
>
> johannes
>

Also, I think something more powerful than the current "rate" field
would be needed, with support for MCS indexes, channel width, retry
count, etc. - one that can configure all values rate_control_get_rate
would perform. I'm planning a Radiotap meeting on Freenode with the
radiotap.h maintainers in various OSes participating, so the field 14+
mess can be cleaned up once for all - that's when I'll probably
propose this field.

Maybe a new IEEE80211_TX_CTL_ or IEEE80211_TX_RC_ flag will also be
needed, so Radiotap can indicate whether rate_control_get_rate needs
to be called.

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