[RFCv4 1/3] cfg80211: add VHT support for IBSS

[RFCv4 1/3] cfg80211: add VHT support for IBSS

[Janusz Dziedzic]

Add NL80211_EXT_FEATURE_VHT_IBSS flag and VHT
support for IBSS.

Signed-off-by: Janusz Dziedzic <janusz.dziedzic@tieto.com>
---
 include/uapi/linux/nl80211.h |  2 ++
 net/wireless/nl80211.c       | 14 ++++++++++++--
 2 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/include/uapi/linux/nl80211.h b/include/uapi/linux/nl80211.h
index 735ab43..ed491b2 100644
--- a/include/uapi/linux/nl80211.h
+++ b/include/uapi/linux/nl80211.h
@@ -4204,11 +4204,13 @@ enum nl80211_feature_flags {
 
 /**
  * enum nl80211_ext_feature_index - bit index of extended features.
+ * @NL80211_EXT_FEATURE_VHT_IBSS: This driver supports IBSS with VHT datarates.
  *
  * @NUM_NL80211_EXT_FEATURES: number of extended features.
  * @MAX_NL80211_EXT_FEATURES: highest extended feature index.
  */
 enum nl80211_ext_feature_index {
+	NL80211_EXT_FEATURE_VHT_IBSS,
 
 	/* add new features before the definition below */
 	NUM_NL80211_EXT_FEATURES,
diff --git a/net/wireless/nl80211.c b/net/wireless/nl80211.c
index 39753de..a662cd1 100644
--- a/net/wireless/nl80211.c
+++ b/net/wireless/nl80211.c
@@ -7092,8 +7092,18 @@ static int nl80211_join_ibss(struct sk_buff *skb, struct genl_info *info)
 		break;
 	case NL80211_CHAN_WIDTH_20:
 	case NL80211_CHAN_WIDTH_40:
-		if (rdev->wiphy.features & NL80211_FEATURE_HT_IBSS)
-			break;
+		if (!(rdev->wiphy.features & NL80211_FEATURE_HT_IBSS))
+			return -EINVAL;
+		break;
+	case NL80211_CHAN_WIDTH_80:
+	case NL80211_CHAN_WIDTH_80P80:
+	case NL80211_CHAN_WIDTH_160:
+		if (!(rdev->wiphy.features & NL80211_FEATURE_HT_IBSS))
+			return -EINVAL;
+		if (!wiphy_ext_feature_isset(&rdev->wiphy,
+					     NL80211_EXT_FEATURE_VHT_IBSS))
+			return -EINVAL;
+		break;
 	default:
 		return -EINVAL;
 	}
-- 
1.9.1

[RFCv4 2/3] mac80211: IBSS fix scan request

[Janusz Dziedzic]

In case of wide bandwidth scan all channels we have
in chandef, not only control one.

Signed-off-by: Janusz Dziedzic <janusz.dziedzic@tieto.com>
---
 net/mac80211/ibss.c        | 80 ++++++++++++++++++++++++++++++++++++++++++++--
 net/mac80211/ieee80211_i.h |  3 +-
 net/mac80211/scan.c        | 25 +++++++++------
 3 files changed, 96 insertions(+), 12 deletions(-)

diff --git a/net/mac80211/ibss.c b/net/mac80211/ibss.c
index b606b53..14acc21 100644
--- a/net/mac80211/ibss.c
+++ b/net/mac80211/ibss.c
@@ -1273,7 +1273,7 @@ static void ieee80211_sta_merge_ibss(struct ieee80211_sub_if_data *sdata)
 
 	scan_width = cfg80211_chandef_to_scan_width(&ifibss->chandef);
 	ieee80211_request_ibss_scan(sdata, ifibss->ssid, ifibss->ssid_len,
-				    NULL, scan_width);
+				    NULL, 0, scan_width);
 }
 
 static void ieee80211_sta_create_ibss(struct ieee80211_sub_if_data *sdata)
@@ -1312,6 +1312,75 @@ static void ieee80211_sta_create_ibss(struct ieee80211_sub_if_data *sdata)
 				  capability, 0, true);
 }
 
+static unsigned ibss_setup_channels(struct wiphy *wiphy,
+				    struct ieee80211_channel **channels,
+				    unsigned int channels_max,
+				    u32 center_freq, u32 width)
+{
+	struct ieee80211_channel *chan = NULL;
+	unsigned int n_chan = 0;
+	u32 start_freq, end_freq, freq;
+
+	if (width <= 20) {
+		start_freq = center_freq;
+		end_freq = center_freq;
+	} else {
+		start_freq = center_freq - width/2 + 10;
+		end_freq = center_freq + width/2 - 10;
+	}
+
+	for (freq = start_freq; freq <= end_freq; freq += 20) {
+		chan = ieee80211_get_channel(wiphy, freq);
+		if (!chan)
+			continue;
+		if (n_chan >= channels_max)
+			return n_chan;
+
+		channels[n_chan] = chan;
+		n_chan++;
+	}
+
+	return n_chan;
+}
+
+static unsigned int
+ieee80211_ibss_setup_scan_channels(struct wiphy *wiphy,
+				   const struct cfg80211_chan_def *chandef,
+				   struct ieee80211_channel **channels,
+				   unsigned int channels_max)
+{
+	unsigned int n_chan = 0;
+	u32 width, cf1, cf2 = 0;
+
+	switch (chandef->width) {
+	case NL80211_CHAN_WIDTH_40:
+		width = 40;
+		break;
+	case NL80211_CHAN_WIDTH_80P80:
+		cf2 = chandef->center_freq2;
+	case NL80211_CHAN_WIDTH_80:
+		width = 80;
+		break;
+	case NL80211_CHAN_WIDTH_160:
+		width = 160;
+		break;
+	default:
+		width = 20;
+		break;
+	}
+
+	cf1 = chandef->center_freq1;
+
+	n_chan = ibss_setup_channels(wiphy, channels, channels_max, cf1, width);
+
+	if (cf2)
+		n_chan += ibss_setup_channels(wiphy, &channels[n_chan],
+					      channels_max - n_chan, cf2,
+					      width);
+
+	return n_chan;
+}
+
 /*
  * This function is called with state == IEEE80211_IBSS_MLME_SEARCH
  */
@@ -1381,11 +1450,18 @@ static void ieee80211_sta_find_ibss(struct ieee80211_sub_if_data *sdata)
 	/* Selected IBSS not found in current scan results - try to scan */
 	if (time_after(jiffies, ifibss->last_scan_completed +
 					IEEE80211_SCAN_INTERVAL)) {
+		struct ieee80211_channel *channels[8];
+		unsigned int num = 0;
+
 		sdata_info(sdata, "Trigger new scan to find an IBSS to join\n");
 
+		num = ieee80211_ibss_setup_scan_channels(local->hw.wiphy,
+							 &ifibss->chandef,
+							 channels,
+							 ARRAY_SIZE(channels));
 		scan_width = cfg80211_chandef_to_scan_width(&ifibss->chandef);
 		ieee80211_request_ibss_scan(sdata, ifibss->ssid,
-					    ifibss->ssid_len, chan,
+					    ifibss->ssid_len, channels, num,
 					    scan_width);
 	} else {
 		int interval = IEEE80211_SCAN_INTERVAL;
diff --git a/net/mac80211/ieee80211_i.h b/net/mac80211/ieee80211_i.h
index cc6e964..9254546 100644
--- a/net/mac80211/ieee80211_i.h
+++ b/net/mac80211/ieee80211_i.h
@@ -1558,7 +1558,8 @@ int ieee80211_mesh_finish_csa(struct ieee80211_sub_if_data *sdata);
 void ieee80211_scan_work(struct work_struct *work);
 int ieee80211_request_ibss_scan(struct ieee80211_sub_if_data *sdata,
 				const u8 *ssid, u8 ssid_len,
-				struct ieee80211_channel *chan,
+				struct ieee80211_channel **channels,
+				unsigned int n_channels,
 				enum nl80211_bss_scan_width scan_width);
 int ieee80211_request_scan(struct ieee80211_sub_if_data *sdata,
 			   struct cfg80211_scan_request *req);
diff --git a/net/mac80211/scan.c b/net/mac80211/scan.c
index ae84267..f76a5d1 100644
--- a/net/mac80211/scan.c
+++ b/net/mac80211/scan.c
@@ -923,11 +923,12 @@ int ieee80211_request_scan(struct ieee80211_sub_if_data *sdata,
 
 int ieee80211_request_ibss_scan(struct ieee80211_sub_if_data *sdata,
 				const u8 *ssid, u8 ssid_len,
-				struct ieee80211_channel *chan,
+				struct ieee80211_channel **channels,
+				unsigned int n_channels,
 				enum nl80211_bss_scan_width scan_width)
 {
 	struct ieee80211_local *local = sdata->local;
-	int ret = -EBUSY;
+	int ret = -EBUSY, i, n_ch = 0;
 	enum ieee80211_band band;
 
 	mutex_lock(&local->mtx);
@@ -937,9 +938,8 @@ int ieee80211_request_ibss_scan(struct ieee80211_sub_if_data *sdata,
 		goto unlock;
 
 	/* fill internal scan request */
-	if (!chan) {
-		int i, max_n;
-		int n_ch = 0;
+	if (!channels) {
+		int max_n;
 
 		for (band = 0; band < IEEE80211_NUM_BANDS; band++) {
 			if (!local->hw.wiphy->bands[band])
@@ -964,12 +964,19 @@ int ieee80211_request_ibss_scan(struct ieee80211_sub_if_data *sdata,
 
 		local->int_scan_req->n_channels = n_ch;
 	} else {
-		if (WARN_ON_ONCE(chan->flags & (IEEE80211_CHAN_NO_IR |
-						IEEE80211_CHAN_DISABLED)))
+		for (i = 0; i < n_channels; i++) {
+			if (channels[i]->flags & (IEEE80211_CHAN_NO_IR |
+						  IEEE80211_CHAN_DISABLED))
+				continue;
+
+			local->int_scan_req->channels[n_ch] = channels[i];
+			n_ch++;
+		}
+
+		if (WARN_ON_ONCE(n_ch == 0))
 			goto unlock;
 
-		local->int_scan_req->channels[0] = chan;
-		local->int_scan_req->n_channels = 1;
+		local->int_scan_req->n_channels = n_ch;
 	}
 
 	local->int_scan_req->ssids = &local->scan_ssid;
-- 
1.9.1

[RFCv4 3/3] mac80211: add VHT support for IBSS

[Janusz Dziedzic]

Add VHT80/VHT160 support for IBSS.
Drivers could activate this feature by
setting NL80211_FEATURE_VHT_IBSS flag.

Signed-off-by: Janusz Dziedzic <janusz.dziedzic@tieto.com>
---
 net/mac80211/ht.c          |  2 --
 net/mac80211/ibss.c        | 62 ++++++++++++++++++++++++++++++++--------
 net/mac80211/ieee80211_i.h |  5 ++++
 net/mac80211/mesh_plink.c  |  4 +++
 net/mac80211/util.c        | 70 ++++++++++++++++++++++++++++++++++++++++++++++
 5 files changed, 129 insertions(+), 14 deletions(-)

diff --git a/net/mac80211/ht.c b/net/mac80211/ht.c
index ff630be..7a76ce6 100644
--- a/net/mac80211/ht.c
+++ b/net/mac80211/ht.c
@@ -252,8 +252,6 @@ bool ieee80211_ht_cap_ie_to_sta_ht_cap(struct ieee80211_sub_if_data *sdata,
 		break;
 	}
 
-	if (bw != sta->sta.bandwidth)
-		changed = true;
 	sta->sta.bandwidth = bw;
 
 	sta->cur_max_bandwidth =
diff --git a/net/mac80211/ibss.c b/net/mac80211/ibss.c
index 14acc21..b9e9f70 100644
--- a/net/mac80211/ibss.c
+++ b/net/mac80211/ibss.c
@@ -188,6 +188,15 @@ ieee80211_ibss_build_presp(struct ieee80211_sub_if_data *sdata,
 		 */
 		pos = ieee80211_ie_build_ht_oper(pos, &sband->ht_cap,
 						 chandef, 0);
+
+		if (chandef->width != NL80211_CHAN_WIDTH_20 &&
+		    chandef->width != NL80211_CHAN_WIDTH_40 &&
+		    sband->vht_cap.vht_supported) {
+			pos = ieee80211_ie_build_vht_cap(pos, &sband->vht_cap,
+							 sband->vht_cap.cap);
+			pos = ieee80211_ie_build_vht_oper(pos, &sband->vht_cap,
+							  chandef);
+		}
 	}
 
 	if (local->hw.queues >= IEEE80211_NUM_ACS)
@@ -411,6 +420,11 @@ static void ieee80211_sta_join_ibss(struct ieee80211_sub_if_data *sdata,
 		chan_type = cfg80211_get_chandef_type(&sdata->u.ibss.chandef);
 		cfg80211_chandef_create(&chandef, cbss->channel, chan_type);
 		break;
+	case NL80211_CHAN_WIDTH_80:
+	case NL80211_CHAN_WIDTH_160:
+		chandef = sdata->u.ibss.chandef;
+		chandef.chan = cbss->channel;
+		break;
 	case NL80211_CHAN_WIDTH_5:
 	case NL80211_CHAN_WIDTH_10:
 		cfg80211_chandef_create(&chandef, cbss->channel,
@@ -995,6 +1009,7 @@ static void ieee80211_rx_bss_info(struct ieee80211_sub_if_data *sdata,
 	enum ieee80211_band band = rx_status->band;
 	enum nl80211_bss_scan_width scan_width;
 	struct ieee80211_supported_band *sband = local->hw.wiphy->bands[band];
+	enum nl80211_chan_width width = sdata->u.ibss.chandef.width;
 	bool rates_updated = false;
 
 	channel = ieee80211_get_channel(local->hw.wiphy, rx_status->freq);
@@ -1042,12 +1057,16 @@ static void ieee80211_rx_bss_info(struct ieee80211_sub_if_data *sdata,
 			sta->sta.wme = true;
 
 		if (sta && elems->ht_operation && elems->ht_cap_elem &&
-		    sdata->u.ibss.chandef.width != NL80211_CHAN_WIDTH_20_NOHT &&
-		    sdata->u.ibss.chandef.width != NL80211_CHAN_WIDTH_5 &&
-		    sdata->u.ibss.chandef.width != NL80211_CHAN_WIDTH_10) {
+		    width != NL80211_CHAN_WIDTH_20_NOHT &&
+		    width != NL80211_CHAN_WIDTH_5 &&
+		    width != NL80211_CHAN_WIDTH_10) {
 			/* we both use HT */
 			struct ieee80211_ht_cap htcap_ie;
 			struct cfg80211_chan_def chandef;
+			struct ieee80211_vht_cap vhtcap_ie;
+			struct ieee80211_sta_vht_cap vht_cap;
+			const struct ieee80211_vht_operation *vht_oper;
+			enum ieee80211_sta_rx_bandwidth bw = sta->sta.bandwidth;
 
 			ieee80211_ht_oper_to_chandef(channel,
 						     elems->ht_operation,
@@ -1055,17 +1074,36 @@ static void ieee80211_rx_bss_info(struct ieee80211_sub_if_data *sdata,
 
 			memcpy(&htcap_ie, elems->ht_cap_elem, sizeof(htcap_ie));
 
-			/*
-			 * fall back to HT20 if we don't use or use
-			 * the other extension channel
-			 */
-			if (chandef.center_freq1 !=
-			    sdata->u.ibss.chandef.center_freq1)
-				htcap_ie.cap_info &=
-					cpu_to_le16(~IEEE80211_HT_CAP_SUP_WIDTH_20_40);
-
 			rates_updated |= ieee80211_ht_cap_ie_to_sta_ht_cap(
 						sdata, sband, &htcap_ie, sta);
+
+			if (elems->vht_operation && elems->vht_cap_elem &&
+			    width != NL80211_CHAN_WIDTH_20 &&
+			    width != NL80211_CHAN_WIDTH_40) {
+				/* we both use VHT */
+				vht_cap = sta->sta.vht_cap;
+				vht_oper = elems->vht_operation;
+
+				ieee80211_vht_oper_to_chandef(channel, vht_oper,
+							      &chandef);
+				memcpy(&vhtcap_ie, elems->vht_cap_elem,
+				       sizeof(vhtcap_ie));
+				ieee80211_vht_cap_ie_to_sta_vht_cap(sdata,
+								    sband,
+								    &vhtcap_ie,
+								    sta);
+				if (memcmp(&vht_cap, &sta->sta.vht_cap,
+					   sizeof(vht_cap)))
+						rates_updated |= true;
+			}
+
+			if (bw != sta->sta.bandwidth)
+				rates_updated |= true;
+
+			if (!cfg80211_chandef_compatible(&sdata->u.ibss.chandef,
+							 &chandef))
+				/* TODO handle incompatible chandefs if sta already added */
+				WARN_ON_ONCE(1);
 		}
 
 		if (sta && rates_updated) {
diff --git a/net/mac80211/ieee80211_i.h b/net/mac80211/ieee80211_i.h
index 9254546..2915880 100644
--- a/net/mac80211/ieee80211_i.h
+++ b/net/mac80211/ieee80211_i.h
@@ -1937,6 +1937,8 @@ u8 *ieee80211_ie_build_ht_oper(u8 *pos, struct ieee80211_sta_ht_cap *ht_cap,
 			       u16 prot_mode);
 u8 *ieee80211_ie_build_vht_cap(u8 *pos, struct ieee80211_sta_vht_cap *vht_cap,
 			       u32 cap);
+u8 *ieee80211_ie_build_vht_oper(u8 *pos, struct ieee80211_sta_vht_cap *vht_cap,
+				const struct cfg80211_chan_def *chandef);
 int ieee80211_parse_bitrates(struct cfg80211_chan_def *chandef,
 			     const struct ieee80211_supported_band *sband,
 			     const u8 *srates, int srates_len, u32 *rates);
@@ -1952,6 +1954,9 @@ u8 *ieee80211_add_wmm_info_ie(u8 *buf, u8 qosinfo);
 void ieee80211_ht_oper_to_chandef(struct ieee80211_channel *control_chan,
 				  const struct ieee80211_ht_operation *ht_oper,
 				  struct cfg80211_chan_def *chandef);
+void ieee80211_vht_oper_to_chandef(struct ieee80211_channel *control_chan,
+				   const struct ieee80211_vht_operation *oper,
+				   struct cfg80211_chan_def *chandef);
 u32 ieee80211_chandef_downgrade(struct cfg80211_chan_def *c);
 
 int __must_check
diff --git a/net/mac80211/mesh_plink.c b/net/mac80211/mesh_plink.c
index b488e18..9875d82 100644
--- a/net/mac80211/mesh_plink.c
+++ b/net/mac80211/mesh_plink.c
@@ -382,6 +382,7 @@ static void mesh_sta_info_init(struct ieee80211_sub_if_data *sdata,
 	enum ieee80211_band band = ieee80211_get_sdata_band(sdata);
 	struct ieee80211_supported_band *sband;
 	u32 rates, basic_rates = 0, changed = 0;
+	enum ieee80211_sta_rx_bandwidth bw = sta->sta.bandwidth;
 
 	sband = local->hw.wiphy->bands[band];
 	rates = ieee80211_sta_get_rates(sdata, elems, band, &basic_rates);
@@ -401,6 +402,9 @@ static void mesh_sta_info_init(struct ieee80211_sub_if_data *sdata,
 					      elems->ht_cap_elem, sta))
 		changed |= IEEE80211_RC_BW_CHANGED;
 
+	if (bw != sta->sta.bandwidth)
+		changed |= IEEE80211_RC_BW_CHANGED;
+
 	/* HT peer is operating 20MHz-only */
 	if (elems->ht_operation &&
 	    !(elems->ht_operation->ht_param &
diff --git a/net/mac80211/util.c b/net/mac80211/util.c
index 974ebe7..c3f7a27 100644
--- a/net/mac80211/util.c
+++ b/net/mac80211/util.c
@@ -2326,6 +2326,43 @@ u8 *ieee80211_ie_build_ht_oper(u8 *pos, struct ieee80211_sta_ht_cap *ht_cap,
 	return pos + sizeof(struct ieee80211_ht_operation);
 }
 
+u8 *ieee80211_ie_build_vht_oper(u8 *pos, struct ieee80211_sta_vht_cap *vht_cap,
+				const struct cfg80211_chan_def *chandef)
+{
+	struct ieee80211_vht_operation *vht_oper;
+
+	/* Build VHT Operation */
+	*pos++ = WLAN_EID_VHT_OPERATION;
+	*pos++ = sizeof(struct ieee80211_vht_operation);
+
+	vht_oper = (struct ieee80211_vht_operation *)pos;
+
+	vht_oper->center_freq_seg1_idx =
+			ieee80211_frequency_to_channel(chandef->center_freq1);
+	vht_oper->center_freq_seg2_idx = 0;
+
+	/* 1 stream, MCS0-7 as a min Basic VHT MCS rates */
+	vht_oper->basic_mcs_set = cpu_to_le16(0xfffc);
+
+	switch (chandef->width) {
+	case NL80211_CHAN_WIDTH_80:
+		vht_oper->chan_width = IEEE80211_VHT_CHANWIDTH_80MHZ;
+		break;
+	case NL80211_CHAN_WIDTH_80P80:
+		vht_oper->chan_width = IEEE80211_VHT_CHANWIDTH_80P80MHZ;
+		vht_oper->center_freq_seg2_idx =
+			ieee80211_frequency_to_channel(chandef->center_freq2);
+		break;
+	case NL80211_CHAN_WIDTH_160:
+		vht_oper->chan_width = IEEE80211_VHT_CHANWIDTH_160MHZ;
+		break;
+	default:
+		return pos;
+	}
+
+	return pos + sizeof(struct ieee80211_vht_operation);
+}
+
 void ieee80211_ht_oper_to_chandef(struct ieee80211_channel *control_chan,
 				  const struct ieee80211_ht_operation *ht_oper,
 				  struct cfg80211_chan_def *chandef)
@@ -2355,6 +2392,39 @@ void ieee80211_ht_oper_to_chandef(struct ieee80211_channel *control_chan,
 	cfg80211_chandef_create(chandef, control_chan, channel_type);
 }
 
+void ieee80211_vht_oper_to_chandef(struct ieee80211_channel *control_chan,
+				   const struct ieee80211_vht_operation *oper,
+				   struct cfg80211_chan_def *chandef)
+{
+	if (!oper)
+		return;
+
+	chandef->chan = control_chan;
+
+	switch (oper->chan_width) {
+	case IEEE80211_VHT_CHANWIDTH_USE_HT:
+		break;
+	case IEEE80211_VHT_CHANWIDTH_80MHZ:
+		chandef->width = NL80211_CHAN_WIDTH_80;
+		break;
+	case IEEE80211_VHT_CHANWIDTH_160MHZ:
+		chandef->width = NL80211_CHAN_WIDTH_160;
+		break;
+	case IEEE80211_VHT_CHANWIDTH_80P80MHZ:
+		chandef->width = NL80211_CHAN_WIDTH_80P80;
+		break;
+	default:
+		break;
+	}
+
+	chandef->center_freq1 =
+		ieee80211_channel_to_frequency(oper->center_freq_seg1_idx,
+					       control_chan->band);
+	chandef->center_freq2 =
+		ieee80211_channel_to_frequency(oper->center_freq_seg2_idx,
+					       control_chan->band);
+}
+
 int ieee80211_parse_bitrates(struct cfg80211_chan_def *chandef,
 			     const struct ieee80211_supported_band *sband,
 			     const u8 *srates, int srates_len, u32 *rates)
-- 
1.9.1

Re: [RFCv4 3/3] mac80211: add VHT support for IBSS

[Johannes Berg]

On Tue, 2015-01-27 at 09:44 +0100, Janusz Dziedzic wrote:

> +u8 *ieee80211_ie_build_vht_oper(u8 *pos, struct ieee80211_sta_vht_cap *vht_cap,
> +				const struct cfg80211_chan_def *chandef)

> +	/* 1 stream, MCS0-7 as a min Basic VHT MCS rates */
> +	vht_oper->basic_mcs_set = cpu_to_le16(0xfffc);

Unless I'm mistaken in my reading of the spec, this will make any
well-behaved client (i.e. not mac80211) not join this network since it
supports VHT MCSes.

We seem to do the same for HT:

        /* It seems that Basic MCS set and Supported MCS set
           are identical for the first 10 bytes */
        memset(&ht_oper->basic_set, 0, 16);
        memcpy(&ht_oper->basic_set, &ht_cap->mcs, 10);

but I'm not convinced it's right. It probably only works because nobody
ever tested against a well-behaved non-HT client? Or perhaps there isn't
even one?

I for one am not really comfortable with this restriction - there's very
little point in making such a restriction in IBSS since if you have it
then the other node will just form its own network on the same channel
and you've won nothing - only lost interoperability.

johannes

Re: [RFCv4 3/3] mac80211: add VHT support for IBSS

[Janusz Dziedzic]

On 27 January 2015 at 11:24, Johannes Berg <johannes@sipsolutions.net> wrote:
> On Tue, 2015-01-27 at 09:44 +0100, Janusz Dziedzic wrote:
>
>> +u8 *ieee80211_ie_build_vht_oper(u8 *pos, struct ieee80211_sta_vht_cap *vht_cap,
>> +                             const struct cfg80211_chan_def *chandef)
>
>> +     /* 1 stream, MCS0-7 as a min Basic VHT MCS rates */
>> +     vht_oper->basic_mcs_set = cpu_to_le16(0xfffc);
>
> Unless I'm mistaken in my reading of the spec, this will make any
> well-behaved client (i.e. not mac80211) not join this network since it
> supports VHT MCSes.
>
> We seem to do the same for HT:
>
>         /* It seems that Basic MCS set and Supported MCS set
>            are identical for the first 10 bytes */
>         memset(&ht_oper->basic_set, 0, 16);
>         memcpy(&ht_oper->basic_set, &ht_cap->mcs, 10);
>
> but I'm not convinced it's right. It probably only works because nobody
> ever tested against a well-behaved non-HT client? Or perhaps there isn't
> even one?
>
for HT (spec, 20.3.5) - MCS0 .. MSC7 are mandatory - but this is for
all stations (not sure about ibss)
for VHT (22.5, table 22-30) - MCS0...MCS7 are mandatory for nss=1 (20,40,80)
Seems such set is secure?

If I understand correctly case you describe with non-HT client:
non-HT client should not understand HT ies, and HT-only client should
not understand VHT ies?

> I for one am not really comfortable with this restriction - there's very
> little point in making such a restriction in IBSS since if you have it
> then the other node will just form its own network on the same channel
> and you've won nothing - only lost interoperability.
>
> johannes
>

Re: [RFCv4 3/3] mac80211: add VHT support for IBSS

[Johannes Berg]

On Tue, 2015-01-27 at 12:39 +0100, Janusz Dziedzic wrote:
> On 27 January 2015 at 11:24, Johannes Berg <johannes@sipsolutions.net> wrote:
> > On Tue, 2015-01-27 at 09:44 +0100, Janusz Dziedzic wrote:
> >
> >> +u8 *ieee80211_ie_build_vht_oper(u8 *pos, struct ieee80211_sta_vht_cap *vht_cap,
> >> +                             const struct cfg80211_chan_def *chandef)
> >
> >> +     /* 1 stream, MCS0-7 as a min Basic VHT MCS rates */
> >> +     vht_oper->basic_mcs_set = cpu_to_le16(0xfffc);
> >
> > Unless I'm mistaken in my reading of the spec, this will make any
> > well-behaved client (i.e. not mac80211) not join this network since it
> > supports VHT MCSes.
> >
> > We seem to do the same for HT:
> >
> >         /* It seems that Basic MCS set and Supported MCS set
> >            are identical for the first 10 bytes */
> >         memset(&ht_oper->basic_set, 0, 16);
> >         memcpy(&ht_oper->basic_set, &ht_cap->mcs, 10);
> >
> > but I'm not convinced it's right. It probably only works because nobody
> > ever tested against a well-behaved non-HT client? Or perhaps there isn't
> > even one?
> >
> for HT (spec, 20.3.5) - MCS0 .. MSC7 are mandatory - but this is for
> all stations (not sure about ibss)
> for VHT (22.5, table 22-30) - MCS0...MCS7 are mandatory for nss=1 (20,40,80)
> Seems such set is secure?
> 
> If I understand correctly case you describe with non-HT client:
> non-HT client should not understand HT ies, and HT-only client should
> not understand VHT ies?

Yeah that's a good point, I guess older clients won't even look at this,
and we don't include the HT or VHT marker in the basic rate set IE.

johannes