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iwd
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ie: Fix VHT Capabilities to Data Rate conversion 

Code that walked the VHT TX/RX MCS maps seemed to assume that bit_field
operated on bits that start at '1'.  But this utility actually operates
on bits that start at '0'.  I.e. the least significant bit is at
position 0.

While we're at it, rename the mcs variable into bitoffset to make it
clearer how the maps are being iterated over.  Supported MCS is actually
the value found in the map.
This commit is contained in:
Denis Kenzior 2021-05-25 17:17:37 -05:00
parent 5120f46199
commit e265f95f45
1 changed files with 8 additions and 7 deletions
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15
src/ie.c
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@ -1941,6 +1941,7 @@ static int ie_parse_vht_capability(struct ie_tlv_iter *vht_iter,
uint64_t *data_rate)
{
int width;
int bitoffset;
int mcs;
unsigned int nss;
unsigned int len;
@ -1995,11 +1996,11 @@ static int ie_parse_vht_capability(struct ie_tlv_iter *vht_iter,
tx_mcs_map[1] = *data++;
/* NSS->MCS map values are grouped in 2-bit values */
for (mcs = 15; mcs >= 0; mcs -= 2) {
uint8_t rx_val = bit_field(rx_mcs_map[mcs / 8],
mcs % 8, 2);
uint8_t tx_val = bit_field(tx_mcs_map[mcs / 8],
mcs % 8, 2);
for (bitoffset = 14; bitoffset >= 0; bitoffset -= 2) {
uint8_t rx_val = bit_field(rx_mcs_map[bitoffset / 8],
bitoffset % 8, 2);
uint8_t tx_val = bit_field(tx_mcs_map[bitoffset / 8],
bitoffset % 8, 2);
/*
* 0 indicates support for MCS 0-7
@ -2010,12 +2011,12 @@ static int ie_parse_vht_capability(struct ie_tlv_iter *vht_iter,
*/
if (!max_rx_mcs && rx_val < 3) {
max_rx_mcs = 7 + rx_val;
rx_nss = (mcs / 2) + 1;
rx_nss = (bitoffset / 2) + 1;
}
if (!max_tx_mcs && tx_val < 3) {
max_tx_mcs = 7 + tx_val;
tx_nss = (mcs / 2) + 1;
tx_nss = (bitoffset / 2) + 1;
}
if (max_rx_mcs && max_tx_mcs)