[PATCH v2] hostapd: add Transmit Power Envelope IE

[Rajkumar Manoharan]

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

Signed-off-by: Rajkumar Manoharan <rmanohar at qti.qualcomm.com>
---
v2:
 * "VHT" removed from the name
 * removed channel switch conditions
 * handled 80+80/160 MHz case
 * corrected max tx power calculation

 src/ap/beacon.c         |   2 +
 src/ap/ieee802_11.h     |   1 +
 src/ap/ieee802_11_vht.c | 103 ++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 106 insertions(+)

diff --git a/src/ap/beacon.c b/src/ap/beacon.c
index 5f65b7d..d4054cb 100644
--- a/src/ap/beacon.c
+++ b/src/ap/beacon.c
@@ -481,6 +481,7 @@ 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_vht_txpwr_env(hapd, pos);
 		pos = hostapd_eid_wb_chsw_wrapper(hapd, pos);
 	}
 	if (hapd->conf->vendor_vht)
@@ -1096,6 +1097,7 @@ 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_vht_txpwr_env(hapd, tailpos);
 		tailpos = hostapd_eid_wb_chsw_wrapper(hapd, tailpos);
 	}
 	if (hapd->conf->vendor_vht)
diff --git a/src/ap/ieee802_11.h b/src/ap/ieee802_11.h
index a2dd132..4788e6b 100644
--- a/src/ap/ieee802_11.h
+++ b/src/ap/ieee802_11.h
@@ -54,6 +54,7 @@ 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_wb_chsw_wrapper(struct hostapd_data *hapd, u8 *eid);
+u8 * hostapd_eid_vht_txpwr_env(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,
diff --git a/src/ap/ieee802_11_vht.c b/src/ap/ieee802_11_vht.c
index 8d2c428..59522a7 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)
@@ -184,6 +185,108 @@ u8 * hostapd_eid_wb_chsw_wrapper(struct hostapd_data *hapd, u8 *eid)
 }
 
 
+u8 * hostapd_eid_vht_txpwr_env(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, max_tx_power, tx_pwr_count, local_pwr_constraint;
+
+	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 (20MHz) */
+			tx_pwr_count = 0;
+		} else {
+			/* Max Transmit Power count = 1 (20, 40MHz) */
+			tx_pwr_count = 1;
+		}
+		break;
+	case VHT_CHANWIDTH_80MHZ:
+		/* Max Transmit Power count = 2 (20, 40 and 80MHz) */
+		tx_pwr_count = 2;
+		break;
+	case VHT_CHANWIDTH_80P80MHZ:
+	case VHT_CHANWIDTH_160MHZ:
+		/* Max Transmit Power count = 3 (20, 40, 80, 160/80+80MHz) */
+		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 2's complement
+	 * with a 0.5 dB step
+	 */
+	max_tx_power = ~(max_tx_power * 2) + 1;
+
+	*eid++ = WLAN_EID_VHT_TRANSMIT_POWER_ENVELOPE;
+	*eid++ = 4;
+
+	/*
+	 * Max Transmit Power count and
+	 * Max Transmit Power units = 0 (EIRP)
+	 */
+	*eid++ = tx_pwr_count;
+
+	i = 0;
+	while (i++ <= tx_pwr_count)
+		*eid++ = max_tx_power;
+
+	return eid;
+}
+
+
 u16 copy_sta_vht_capab(struct hostapd_data *hapd, struct sta_info *sta,
 		       const u8 *vht_capab)
 {
-- 
2.6.2