This is a workaround for VHT-enabled STAs which break the spec
and have the VHT-MCS Rx map filled in with value 3 for all eight
spacial streams, an example is AR9462 in AP mode.
As per spec, in section 22.1.1 Introduction to the VHT PHY
A VHT STA shall support at least single spactial stream VHT-MCSs
0 to 7 (transmit and receive) in all supported channel widths.
Some devices in STA mode will get firmware assert when trying to
associate, examples are QCA9377 & QCA6174.
Packet example of broken VHT Cap IE of AR9462:
Tag: VHT Capabilities (IEEE Std 802.11ac/D3.1)
Tag Number: VHT Capabilities (IEEE Std 802.11ac/D3.1) (191)
Tag length: 12
VHT Capabilities Info: 0x00000000
VHT Supported MCS Set
Rx MCS Map: 0xffff
.... .... .... ..11 = Rx 1 SS: Not Supported (0x0003)
.... .... .... 11.. = Rx 2 SS: Not Supported (0x0003)
.... .... ..11 .... = Rx 3 SS: Not Supported (0x0003)
.... .... 11.. .... = Rx 4 SS: Not Supported (0x0003)
.... ..11 .... .... = Rx 5 SS: Not Supported (0x0003)
.... 11.. .... .... = Rx 6 SS: Not Supported (0x0003)
..11 .... .... .... = Rx 7 SS: Not Supported (0x0003)
11.. .... .... .... = Rx 8 SS: Not Supported (0x0003)
...0 0000 0000 0000 = Rx Highest Long GI Data Rate (in Mb/s, 0 = subfield not in use): 0x0000
Tx MCS Map: 0xffff
...0 0000 0000 0000 = Tx Highest Long GI Data Rate (in Mb/s, 0 = subfield not in use): 0x0000
Signed-off-by: Filip Matusiak <filip.matusiak@xxxxxxxxx>
---
net/mac80211/vht.c | 16 ++++++++++++++++
1 file changed, 16 insertions(+)
diff --git a/net/mac80211/vht.c b/net/mac80211/vht.c
index ee71576..6832bf6 100644
--- a/net/mac80211/vht.c
+++ b/net/mac80211/vht.c
@@ -270,6 +270,22 @@ ieee80211_vht_cap_ie_to_sta_vht_cap(struct ieee80211_sub_if_data *sdata,
vht_cap->vht_mcs.tx_mcs_map |= cpu_to_le16(peer_tx << i * 2);
}
+ /*
+ * This is a workaround for VHT-enabled STAs which break the spec
+ * and have the VHT-MCS Rx map filled in with value 3 for all eight
+ * spacial streams, an example is AR9462.
+ *
+ * As per spec, in section 22.1.1 Introduction to the VHT PHY
+ * A VHT STA shall support at least single spactial stream VHT-MCSs
+ * 0 to 7 (transmit and receive) in all supported channel widths.
+ */
+ if (vht_cap->vht_mcs.rx_mcs_map == cpu_to_le16(0xFFFF)) {
+ vht_cap->vht_supported = false;
+ sdata_info(sdata, "Ignoring VHT IE from %pM due to invalid rx_mcs_map\n",
+ sta->addr);
+ return;
+ }
+
/* finally set up the bandwidth */
switch (vht_cap->cap & IEEE80211_VHT_CAP_SUPP_CHAN_WIDTH_MASK) {
case IEEE80211_VHT_CAP_SUPP_CHAN_WIDTH_160MHZ:
--
2.7.4
