mac80211: reject/clear user rate mask if not usable

If the user rate mask results in no (basic) rates being usable,
clear it. Also, if we're already operating when it's set, reject
it instead.

Technically, selecting basic rates as the criterion is a bit too
restrictive, but calculating the usable rates over all stations
(e.g. in AP mode) is harder, and all stations must support the
basic rates. Similarly, in client mode, the basic rates will be
used anyway for control frames.

This fixes the "no supported rates (...) in rate_mask ..." warning
that occurs on TX when you've selected a rate mask that's not
compatible with the connection (e.g. an AP that enables only the
rates 36, 48, 54 and you've selected only 6, 9, 12.)

Reported-by: Kirtika Ruchandani <kirtika@google.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

1 files changed, 27 insertions, 0 deletions

diff --git a/net/mac80211/rate.c b/net/mac80211/rate.c
index 094c15645228..3bddd9bbb76f 100644
--- a/net/mac80211/rate.c
+++ b/net/mac80211/rate.c
@@ -2,6 +2,7 @@
  * Copyright 2002-2005, Instant802 Networks, Inc.
  * Copyright 2005-2006, Devicescape Software, Inc.
  * Copyright (c) 2006 Jiri Benc <jbenc@suse.cz>
+ * Copyright 2017	Intel Deutschland GmbH
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 2 as
@@ -241,6 +242,32 @@ static void rate_control_free(struct ieee80211_local *local,
 	kfree(ctrl_ref);
 }
 
+void ieee80211_check_rate_mask(struct ieee80211_sub_if_data *sdata)
+{
+	struct ieee80211_local *local = sdata->local;
+	struct ieee80211_supported_band *sband;
+	u32 user_mask, basic_rates = sdata->vif.bss_conf.basic_rates;
+	enum nl80211_band band;
+
+	if (WARN_ON(!sdata->vif.bss_conf.chandef.chan))
+		return;
+
+	if (WARN_ON_ONCE(!basic_rates))
+		return;
+
+	band = sdata->vif.bss_conf.chandef.chan->band;
+	user_mask = sdata->rc_rateidx_mask[band];
+	sband = local->hw.wiphy->bands[band];
+
+	if (user_mask & basic_rates)
+		return;
+
+	sdata_dbg(sdata,
+		  "no overlap between basic rates (0x%x) and user mask (0x%x on band %d) - clearing the latter",
+		  basic_rates, user_mask, band);
+	sdata->rc_rateidx_mask[band] = (1 << sband->n_bitrates) - 1;
+}
+
 static bool rc_no_data_or_no_ack_use_min(struct ieee80211_tx_rate_control *txrc)
 {
 	struct sk_buff *skb = txrc->skb;