[PATCH] mac80211: Parse IEEE80211_RADIOTAP_RATE on TX

[PATCH] mac80211: Parse IEEE80211_RADIOTAP_RATE on TX

[Rostislav Lisovy]

Add support for parsing radiotap field IEEE80211_RADIOTAP_RATE
for transmitted frames. Use the provided datarate value in
info->control.rates[] array so it will be used for transmission.

Signed-off-by: Rostislav Lisovy <rostislav.lisovy@fel.cvut.cz>
---
This feature is essential for Transmit Datarate Control (TDC)
in future implementation of IEEE 802.11-2012 "Wireless Access
for the Vehicular Environment" support.


 include/net/mac80211.h |  2 ++
 net/mac80211/rate.c    |  4 ++++
 net/mac80211/tx.c      | 43 +++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 49 insertions(+)

diff --git a/include/net/mac80211.h b/include/net/mac80211.h
index 9ce5cb1..7ba8faa 100644
--- a/include/net/mac80211.h
+++ b/include/net/mac80211.h
@@ -549,11 +549,13 @@ enum mac80211_tx_info_flags {
  *
  * @IEEE80211_TX_CTRL_PORT_CTRL_PROTO: this frame is a port control
  *	protocol frame (e.g. EAP)
+ * @IEEE80211_TX_CTRL_USERRATE: Fixed datarate set by the user
  *
  * These flags are used in tx_info->control.flags.
  */
 enum mac80211_tx_control_flags {
 	IEEE80211_TX_CTRL_PORT_CTRL_PROTO	= BIT(0),
+	IEEE80211_TX_CTRL_USERRATE		= BIT(1),
 };
 
 /*
diff --git a/net/mac80211/rate.c b/net/mac80211/rate.c
index 8fdadfd..1111dee 100644
--- a/net/mac80211/rate.c
+++ b/net/mac80211/rate.c
@@ -673,6 +673,10 @@ void rate_control_get_rate(struct ieee80211_sub_if_data *sdata,
 		priv_sta = sta->rate_ctrl_priv;
 	}
 
+	if ((info->flags & IEEE80211_TX_CTL_INJECTED) &&
+	    (info->control.flags & IEEE80211_TX_CTRL_USERRATE))
+		return;
+
 	for (i = 0; i < IEEE80211_TX_MAX_RATES; i++) {
 		info->control.rates[i].idx = -1;
 		info->control.rates[i].flags = 0;
diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c
index 865bdaf..2099c70 100644
--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -1541,7 +1541,11 @@ static bool ieee80211_parse_tx_radiotap(struct sk_buff *skb)
 	struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
 	int ret = ieee80211_radiotap_iterator_init(&iterator, rthdr, skb->len,
 						   NULL);
+	struct ieee80211_sub_if_data *sdata;
+	struct ieee80211_supported_band *sband;
+	int rate;
 	u16 txflags;
+	int i, j;
 
 	info->flags |= IEEE80211_TX_INTFL_DONT_ENCRYPT |
 		       IEEE80211_TX_CTL_DONTFRAG;
@@ -1592,6 +1596,45 @@ static bool ieee80211_parse_tx_radiotap(struct sk_buff *skb)
 				info->flags |= IEEE80211_TX_CTL_NO_ACK;
 			break;
 
+		case IEEE80211_RADIOTAP_RATE:
+			if (!(*iterator.this_arg))
+				break;
+
+			rate = 0;
+			sdata = vif_to_sdata(info->control.vif);
+			sband = sdata->wdev.wiphy->bands[info->band];
+			for (i = 0; i < sband->n_bitrates; i++) {
+				/* Radiotap datarate: Units of 500 Kbps
+				 * ieee80211_rate.bitrate: Units of 100 Kbps
+				 */
+				if ((sband->bitrates[i].bitrate * 2) ==
+				    ((*iterator.this_arg) * 10)) {
+					rate = i;
+					break;
+				}
+			}
+
+			if (!rate)
+				break;
+
+			info->flags |= IEEE80211_TX_CTRL_USERRATE;
+
+			for (i = 0; i < IEEE80211_TX_MAX_RATES; i++) {
+				if (info->control.rates[i].idx < 0)
+					break;
+
+				/* Rate masking supports only legacy
+				 * rates for now
+				 */
+				if (info->control.rates[i].flags &
+				    IEEE80211_TX_RC_MCS)
+					continue;
+
+				for (j = 0; j < sband->n_bitrates; j++)
+					info->control.rates[i].idx = rate;
+			}
+			break;
+
 		/*
 		 * Please update the file
 		 * Documentation/networking/mac80211-injection.txt
-- 
2.0.0.rc4

Re: [PATCH] mac80211: Parse IEEE80211_RADIOTAP_RATE on TX

[Johannes Berg]

On Thu, 2014-07-10 at 14:27 +0200, Rostislav Lisovy wrote:
> Add support for parsing radiotap field IEEE80211_RADIOTAP_RATE
> for transmitted frames. Use the provided datarate value in
> info->control.rates[] array so it will be used for transmission.
> 
> Signed-off-by: Rostislav Lisovy <rostislav.lisovy@fel.cvut.cz>
> ---
> This feature is essential for Transmit Datarate Control (TDC)
> in future implementation of IEEE 802.11-2012 "Wireless Access
> for the Vehicular Environment" support.

It seems like an extremely bad idea to base your implementation of WAVE
on monitor mode with injection.

Why can't you add a proper datapath?

johannes

Re: [PATCH] mac80211: Parse IEEE80211_RADIOTAP_RATE on TX

[Rostislav Lisovy]

On Mon, 2014-07-21 at 12:20 +0200, Johannes Berg wrote:
> On Thu, 2014-07-10 at 14:27 +0200, Rostislav Lisovy wrote:
> > Add support for parsing radiotap field IEEE80211_RADIOTAP_RATE
> > for transmitted frames. Use the provided datarate value in
> > info->control.rates[] array so it will be used for transmission.
> > 
> > Signed-off-by: Rostislav Lisovy <rostislav.lisovy@fel.cvut.cz>
> > ---
> > This feature is essential for Transmit Datarate Control (TDC)
> > in future implementation of IEEE 802.11-2012 "Wireless Access
> > for the Vehicular Environment" support.
> 
> It seems like an extremely bad idea to base your implementation of WAVE
> on monitor mode with injection.
> 
> Why can't you add a proper datapath?
> 

You are right. I was overthinking the per-packet datarate setting a
little bit.
If I am not mistaken it is not possible to say that this feature may be
useful as the general method for monitor-mode injection with datarate
until there is some user-space utility really using/needing it?

Best regards;
Rostislav

Re: [PATCH] mac80211: Parse IEEE80211_RADIOTAP_RATE on TX

[Johannes Berg]

On Mon, 2014-08-25 at 09:52 +0200, Rostislav Lisovy wrote:

> If I am not mistaken it is not possible to say that this feature may be
> useful as the general method for monitor-mode injection with datarate
> until there is some user-space utility really using/needing it?

Yes, this wasn't as much a comment on the patch as rather on your
implied approach for your userspace :)

That said, it's tricky, be cause much hardware doesn't allow to do this.
Maybe we should then have a feature flag or so rather than silently
ignoring the data?

johannes