Re: [PATCH v2] mac80211: reject/clear user rate mask if not usable

[Wen Gong <wgong@codeaurora.org>]

On 2017-03-08 21:20, Johannes Berg wrote:
> From: Johannes Berg <johannes.berg@intel.com>
> 
> 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>
> ---
>  net/mac80211/cfg.c  | 18 +++++++++++++++++-
>  net/mac80211/mlme.c |  2 ++
>  net/mac80211/rate.c | 27 +++++++++++++++++++++++++++
>  net/mac80211/rate.h |  2 ++
>  4 files changed, 48 insertions(+), 1 deletion(-)
> 
> diff --git a/net/mac80211/cfg.c b/net/mac80211/cfg.c
> index 9c7490cb2243..8bc3d3669348 100644
> --- a/net/mac80211/cfg.c
> +++ b/net/mac80211/cfg.c
> @@ -3,7 +3,7 @@
>   *
>   * Copyright 2006-2010	Johannes Berg <johannes@sipsolutions.net>
>   * Copyright 2013-2015  Intel Mobile Communications GmbH
> - * Copyright (C) 2015-2016 Intel Deutschland GmbH
> + * Copyright (C) 2015-2017 Intel Deutschland GmbH
>   *
>   * This file is GPLv2 as found in COPYING.
>   */
> @@ -2042,6 +2042,7 @@ static int ieee80211_change_bss(struct wiphy 
> *wiphy,
>  					 params->basic_rates_len,
>  					 &sdata->vif.bss_conf.basic_rates);
>  		changed |= BSS_CHANGED_BASIC_RATES;
> +		ieee80211_check_rate_mask(sdata);
>  	}
> 
>  	if (params->ap_isolate >= 0) {
> @@ -2685,6 +2686,21 @@ static int ieee80211_set_bitrate_mask(struct
> wiphy *wiphy,
>  			return ret;
>  	}
> 
> +	/*
> +	 * If active validate the setting and reject it if it doesn't leave
> +	 * at least one basic rate usable, since we really have to be able
> +	 * to send something, and if we're an AP we have to be able to do
> +	 * so at a basic rate so that all clients can receive it.
> +	 */
> +	if (rcu_access_pointer(sdata->vif.chanctx_conf) &&
> +	    sdata->vif.bss_conf.chandef.chan) {
> +		u32 basic_rates = sdata->vif.bss_conf.basic_rates;
> +		enum nl80211_band band = sdata->vif.bss_conf.chandef.chan->band;
> +
> +		if (!(mask->control[band].legacy & basic_rates))
> +			return -EINVAL;
If user want to use “iw wlan0 set bitrates legacy-5 54” to set it to 
fixed in 54M and 54M is
not basic rate in AP's becaon as example of below, then the iw command 
will fail.

Tag: Supported Rates 6(B), 9, 12(B), 18, 24(B), 36, 48, 54, [Mbit/sec]
     Tag Number: Supported Rates (1)
     Tag length: 8
     Supported Rates: 6(B) (0x8c)
     Supported Rates: 9 (0x12)
     Supported Rates: 12(B) (0x98)
     Supported Rates: 18 (0x24)
     Supported Rates: 24(B) (0xb0)
     Supported Rates: 36 (0x48)
     Supported Rates: 48 (0x60)
     Supported Rates: 54 (0x6c)

> +	}
> +
>  	for (i = 0; i < NUM_NL80211_BANDS; i++) {
>  		struct ieee80211_supported_band *sband = wiphy->bands[i];
>  		int j;
...