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Calculate the duration/id field in driver:

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Linux only sets that field for non-ht, and leaves the field blank for ht. Linux expects lower level set it. This is realized after checking the mac80211 source code. After studying the duration/id field of COTS WiFi chip by wireshark, we calculate it in driver sdr.c gen_ht_duration_id(). The concrete logic/method of the calculation is in the comments of the function gen_ht_duration_id().
This commit is contained in:
Xianjun Jiao 2022-03-29 11:04:35 +02:00
parent 86032d0bc7
commit 5c65530f0b
1 changed files with 72 additions and 1 deletions
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73
driver/sdr.c
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@ -707,6 +707,72 @@ static inline struct gpio_led_data * //please align with the implementation in l
return container_of(led_cdev, struct gpio_led_data, cdev);
}
inline int calc_n_ofdm(int num_octet, int n_dbps)
{
int num_bit, num_ofdm_sym;
num_bit = 22+num_octet*8;
num_ofdm_sym = (num_bit/n_dbps) + ((num_bit%n_dbps)!=0);
return (num_ofdm_sym);
}
inline __le16 gen_ht_duration_id(__le16 frame_control, __le16 aid, u8 qos_hdr, bool use_ht_aggr, u16 rate_hw_value, u16 sifs)
{
// COTS wifi ht QoS data duration field analysis (lots of capture):
// ht non-aggr QoS data: 44, type 2 (data frame) sub-type 8 (1000) 21.7/52/57.8/58.5/65Mbps
// ack ht 36 + 4*[(22+14*8)/78] = 36 + 4*2 = 44
// ack legacy 20 + 4*[(22+14*8)/72] = 20 + 4*2 = 28
// ht non-aggr QoS data: 60, type 2 (data frame) sub-type 8 (1000) 6.5Mbps
// ack ht 36 + 4*[(22+14*8)/26] = 36 + 4*6 = 60
// ack legacy 20 + 4*[(22+14*8)/24] = 20 + 4*6 = 44
// ht aggr QoS data: 52, type 2 (data frame) sub-type 8 (1000) 19.5/28.9/39/57.8/65/72.2Mbps
// ack ht 36 + 4*[(22+32*8)/78] = 36 + 4*4 = 52
// ack legacy 20 + 4*[(22+32*8)/72] = 20 + 4*4 = 36
// ht aggr QoS data: 60, type 2 (data frame) sub-type 8 (1000) 13/14.4Mbps
// ack ht 36 + 4*[(22+32*8)/52] = 36 + 4*6 = 60
// ack legacy 20 + 4*[(22+32*8)/48] = 20 + 4*6 = 44
// ht and legacy rate mapping is ont one on one, instead it is modulation combined with coding rate
// modulate coding ht-mcs ht-n_dbps legacy-mcs legacy-n_dbps
// BPSK 1/2 0 26 4 24
// QPSK 1/2 1 52 6 48
// QPSK 3/4 2 78 7 72
// 16QAM 1/2 3 104 8 96
// 16QAM 3/4 4 156 9 144
// 64QAM 2/3 5 208 10 192
// 64QAM 3/4 6 234 11 216
// conclusion: duration is: assume ack/blk-ack uses legacy, plus SIFS
// other observation: ht always use QoS data, not data (sub-type)
// other observation: management/control frame always in non-ht
__le16 dur = 0;
u16 n_dbps;
int num_octet, num_ofdm_sym;
if (ieee80211_is_pspoll(frame_control)) {
dur = (aid|0xc000);
} else if (ieee80211_is_data_qos(frame_control) && (~(qos_hdr&IEEE80211_QOS_CTL_ACK_POLICY_NOACK))) {
rate_hw_value = (rate_hw_value>6?6:rate_hw_value);
n_dbps = (rate_hw_value==0?wifi_n_dbps_table[4]:wifi_n_dbps_table[rate_hw_value+5]);
num_octet = (use_ht_aggr?32:14); //32 bytes for compressed block ack; 14 bytes for normal ack
num_ofdm_sym = calc_n_ofdm(num_octet, n_dbps);
dur = sifs + 20 + 4*num_ofdm_sym; // 20us legacy preamble
// printk("%s gen_ht_duration_id: num_octet %d n_dbps %d num_ofdm_sym %d dur %d\n", sdr_compatible_str,
// num_octet, n_dbps, num_ofdm_sym, dur);
} else {
printk("%s openwifi_tx: WARNING gen_ht_duration_id wrong pkt type!\n", sdr_compatible_str);
}
return dur;
}
static void openwifi_tx(struct ieee80211_hw *dev,
struct ieee80211_tx_control *control,
struct sk_buff *skb)
@ -791,7 +857,6 @@ static void openwifi_tx(struct ieee80211_hw *dev,
addr3_high16 = *((u16*)(hdr->addr3));
}
duration_id = hdr->duration_id;
frame_control=hdr->frame_control;
pkt_need_ack = (!(info->flags&IEEE80211_TX_CTL_NO_ACK));
@ -826,6 +891,12 @@ static void openwifi_tx(struct ieee80211_hw *dev,
sifs = (priv->actual_rx_lo<2500?10:16);
if (use_ht_rate) {
// printk("%s openwifi_tx: rate_hw_value %d aggr %d sifs %d\n", sdr_compatible_str, rate_hw_value, use_ht_aggr, sifs);
hdr->duration_id = gen_ht_duration_id(frame_control, control->sta->aid, qos_hdr, use_ht_aggr, rate_hw_value, sifs); //linux only do it for 11a/g, not for 11n and later
}
duration_id = hdr->duration_id;
if (use_rts_cts)
printk("%s openwifi_tx: WARNING sn %d use_rts_cts is not supported!\n", sdr_compatible_str, ring->bd_wr_idx);