hostapd: Add Transmit Power Envelope IE when VHT is enabled

Add Transmit Power Envelope element defined in IEEE P802.11-REVmc/D4.3,
8.4.2.161.

Git-commit: 3c417499e71b0c7f2dfae69fb1b67eb31e467ba6
Git-repo : git://w1.fi/srv/git/hostap.git
CRs-Fixed: 979946
Change-Id: Ib3e11ee78cbe8e4d875d6c43dc2ec5539043fdb1
Signed-off-by: Rajkumar Manoharan <rmanohar@qti.qualcomm.com>

3 files changed, 117 insertions, 0 deletions

diff --git a/src/ap/beacon.c b/src/ap/beacon.c
index 54d0d6f4..c319372b 100644
--- a/src/ap/beacon.c
+++ b/src/ap/beacon.c
@@ -466,6 +466,7 @@ static u8 * hostapd_gen_probe_resp(struct hostapd_data *hapd,
 	if (hapd->iconf->ieee80211ac && !hapd->conf->disable_11ac) {
 		pos = hostapd_eid_vht_capabilities(hapd, pos);
 		pos = hostapd_eid_vht_operation(hapd, pos);
+		pos = hostapd_eid_txpower_envelope(hapd, pos);
 	}
 	if (hapd->conf->vendor_vht)
 		pos = hostapd_eid_vendor_vht(hapd, pos);
@@ -925,6 +926,7 @@ int ieee802_11_build_ap_params(struct hostapd_data *hapd,
 	if (hapd->iconf->ieee80211ac && !hapd->conf->disable_11ac) {
 		tailpos = hostapd_eid_vht_capabilities(hapd, tailpos);
 		tailpos = hostapd_eid_vht_operation(hapd, tailpos);
+		tailpos = hostapd_eid_txpower_envelope(hapd, tailpos);
 	}
 	if (hapd->conf->vendor_vht)
 		tailpos = hostapd_eid_vendor_vht(hapd, tailpos);
diff --git a/src/ap/ieee802_11.h b/src/ap/ieee802_11.h
index 44c1bff3..6f505409 100644
--- a/src/ap/ieee802_11.h
+++ b/src/ap/ieee802_11.h
@@ -52,6 +52,8 @@ u8 * hostapd_eid_ht_operation(struct hostapd_data *hapd, u8 *eid);
 u8 * hostapd_eid_vht_capabilities(struct hostapd_data *hapd, u8 *eid);
 u8 * hostapd_eid_vht_operation(struct hostapd_data *hapd, u8 *eid);
 u8 * hostapd_eid_vendor_vht(struct hostapd_data *hapd, u8 *eid);
+u8 * hostapd_eid_txpower_envelope(struct hostapd_data *hapd, u8 *eid);
+
 int hostapd_ht_operation_update(struct hostapd_iface *iface);
 void ieee802_11_send_sa_query_req(struct hostapd_data *hapd,
 				  const u8 *addr, const u8 *trans_id);
diff --git a/src/ap/ieee802_11_vht.c b/src/ap/ieee802_11_vht.c
index 5bf1b5d7..d31ab730 100644
--- a/src/ap/ieee802_11_vht.c
+++ b/src/ap/ieee802_11_vht.c
@@ -17,6 +17,7 @@
 #include "sta_info.h"
 #include "beacon.h"
 #include "ieee802_11.h"
+#include "dfs.h"
 
 
 u8 * hostapd_eid_vht_capabilities(struct hostapd_data *hapd, u8 *eid)
@@ -131,6 +132,118 @@ static int check_valid_vht_mcs(struct hostapd_hw_modes *mode,
 }
 
 
+u8 * hostapd_eid_txpower_envelope(struct hostapd_data *hapd, u8 *eid)
+{
+	struct hostapd_iface *iface = hapd->iface;
+	struct hostapd_config *iconf = iface->conf;
+	struct hostapd_hw_modes *mode = iface->current_mode;
+	struct hostapd_channel_data *chan;
+	int dfs, i;
+	u8 channel, tx_pwr_count, local_pwr_constraint;
+	int max_tx_power;
+	u8 tx_pwr;
+
+	if (!mode)
+		return eid;
+
+	if (ieee80211_freq_to_chan(iface->freq, &channel) == NUM_HOSTAPD_MODES)
+		return eid;
+
+	for (i = 0; i < mode->num_channels; i++) {
+		if (mode->channels[i].freq == iface->freq)
+			break;
+	}
+	if (i == mode->num_channels)
+		return eid;
+
+	switch (iface->conf->vht_oper_chwidth) {
+	case VHT_CHANWIDTH_USE_HT:
+		if (iconf->secondary_channel == 0) {
+			/* Max Transmit Power count = 0 (20 MHz) */
+			tx_pwr_count = 0;
+		} else {
+			/* Max Transmit Power count = 1 (20, 40 MHz) */
+			tx_pwr_count = 1;
+		}
+		break;
+	case VHT_CHANWIDTH_80MHZ:
+		/* Max Transmit Power count = 2 (20, 40, and 80 MHz) */
+		tx_pwr_count = 2;
+		break;
+	case VHT_CHANWIDTH_80P80MHZ:
+	case VHT_CHANWIDTH_160MHZ:
+		/* Max Transmit Power count = 3 (20, 40, 80, 160/80+80 MHz) */
+		tx_pwr_count = 3;
+		break;
+	default:
+		return eid;
+	}
+
+	/*
+	 * Below local_pwr_constraint logic is referred from
+	 * hostapd_eid_pwr_constraint.
+	 *
+	 * Check if DFS is required by regulatory.
+	 */
+	dfs = hostapd_is_dfs_required(hapd->iface);
+	if (dfs < 0)
+		dfs = 0;
+
+	/*
+	 * In order to meet regulations when TPC is not implemented using
+	 * a transmit power that is below the legal maximum (including any
+	 * mitigation factor) should help. In this case, indicate 3 dB below
+	 * maximum allowed transmit power.
+	 */
+	if (hapd->iconf->local_pwr_constraint == -1)
+		local_pwr_constraint = (dfs == 0) ? 0 : 3;
+	else
+		local_pwr_constraint = hapd->iconf->local_pwr_constraint;
+
+	/*
+	 * A STA that is not an AP shall use a transmit power less than or
+	 * equal to the local maximum transmit power level for the channel.
+	 * The local maximum transmit power can be calculated from the formula:
+	 * local max TX pwr = max TX pwr - local pwr constraint
+	 * Where max TX pwr is maximum transmit power level specified for
+	 * channel in Country element and local pwr constraint is specified
+	 * for channel in this Power Constraint element.
+	 */
+	chan = &mode->channels[i];
+	max_tx_power = chan->max_tx_power - local_pwr_constraint;
+
+	/*
+	 * Local Maximum Transmit power is encoded as two's complement
+	 * with a 0.5 dB step.
+	 */
+	max_tx_power *= 2; /* in 0.5 dB steps */
+	if (max_tx_power > 127) {
+		/* 63.5 has special meaning of 63.5 dBm or higher */
+		max_tx_power = 127;
+	}
+	if (max_tx_power < -128)
+		max_tx_power = -128;
+	if (max_tx_power < 0)
+		tx_pwr = 0x80 + max_tx_power + 128;
+	else
+		tx_pwr = max_tx_power;
+
+	*eid++ = WLAN_EID_VHT_TRANSMIT_POWER_ENVELOPE;
+	*eid++ = 2 + tx_pwr_count;
+
+	/*
+	 * Max Transmit Power count and
+	 * Max Transmit Power units = 0 (EIRP)
+	 */
+	*eid++ = tx_pwr_count;
+
+	for (i = 0; i <= tx_pwr_count; i++)
+		*eid++ = tx_pwr;
+
+	return eid;
+}
+
+
 u16 copy_sta_vht_capab(struct hostapd_data *hapd, struct sta_info *sta,
 		       const u8 *vht_capab)
 {