net80211: allow to configure LDPC support

[avos]

Summary

Test Plan

Tested with RTL8821AU, STA mode (Tx support only)

[avos]

I'm unsure about IEEE80211_NODE_* flags setup in ieee80211_ht.c - if user will play enough with ifconfig(8) parameters some nodes may be created without the flag but with ni->ni_htcap and vap->iv_flags_ht bits set.

[adrian]

Ideally nodes without NODE_HT / NODE_VHT set won't even do HT/VHT bits. If we have that happening we should fix it. :-)

This looks good; you've verified that LDPC frames actually are being transmitted appropriately? and negotation is working right?

[avos]

Fix few typos

[avos]

In D9268#191641, @adrian wrote:

Ideally nodes without NODE_HT / NODE_VHT set won't even do HT/VHT bits. If we have that happening we should fix it. :-)

As an example:

• driver handles IEEE80211_IOC_SHORTGI without restart;
• user disables it via 'ifconfig wlan0 -shortgi'
• some node with short GI support associates; since IEEE80211_FHT_SHORTGI20 bit is not set, htcap_update_shortgi() will not set IEEE80211_NODE_SGI20 for this node;
• user re-enables it via 'ifconfig wlan0 shortgi'; but IEEE80211_NODE_SGI20 for the node will not be set.

(for rtwn(4) I prefer to check ni->ni_htcap and vap->iv_flags_ht instead until this bug exists)

This looks good; you've verified that LDPC frames actually are being transmitted appropriately? and negotation is working right?

When LDPC (for Tx only) is enabled:

• RTL8188CE in monitor mode can see only received frames (sent without LDPC) + all control frames.

When it is disabled:

• all frames are seen (by RTL8188CE - RTL8188EU can't see Tx data frames in both cases).

In both cases, Tx / Rx between STA (RTL8821AU) and AP (Netis AC1200, RTL8812AR) works fine.

Association request is sent without LDPC capability bit set; assoc response has this bit set.