From: Stefan Sperling <stsp@stsp.name>
Subject: Re: sys/net80211: announce 160MHz channels only when driver supports it
To: tech@openbsd.org
Date: Mon, 30 Mar 2026 15:16:18 +0200

On Mon, Mar 30, 2026 at 03:07:49PM +0200, Kirill A. Korinsky wrote:
> tech@,
> 
> support of 160Mhz window brings a regression for drivers which do not
> supprot 160MHz window which leads to the wrong channel center.
> 
> It was tested on iwx with and without 160Mhz window support in the code
> agaisnt 2.4Ghz network with 20Mhz and 40Mhz, and 5Ghz with 40Mhz, 60Mhz,
> 80Mhz and 160Mhz window.
> 
> Reported as iwm issue by martijn@
> 
> Ok?

Makes sense to me, ok stsp@

> Index: sys/net80211/ieee80211_node.c
> ===================================================================
> RCS file: /home/cvs/src/sys/net80211/ieee80211_node.c,v
> diff -u -p -r1.213 ieee80211_node.c
> --- sys/net80211/ieee80211_node.c	29 Mar 2026 21:16:21 -0000	1.213
> +++ sys/net80211/ieee80211_node.c	30 Mar 2026 12:15:23 -0000
> @@ -2602,8 +2602,10 @@ int
>  ieee80211_setup_vhtop(struct ieee80211_node *ni, const uint8_t *data,
>      uint8_t len, int isprobe)
>  {
> +	struct ieee80211com *ic = ni->ni_ic;
>  	uint8_t sco, ccfs0, ccfs1, ccfs2, supp_chwidth, ext_nss_bw_supp;
> -	int have_40mhz, width, ccf1;
> +	uint8_t local_chwidth, local_ext_nss_bw_supp;
> +	int have_40mhz, local_supports_160, width, ccf1;
>  
>  	if (len != 5)
>  		return 0;
> @@ -2636,6 +2638,18 @@ ieee80211_setup_vhtop(struct ieee80211_n
>  		ext_nss_bw_supp =
>  		    (ni->ni_vhtcaps & IEEE80211_VHTCAP_EXT_NSS_BW_MASK) >>
>  		    IEEE80211_VHTCAP_EXT_NSS_BW_SHIFT;
> +		local_chwidth = (ic->ic_vhtcaps &
> +		    IEEE80211_VHTCAP_CHAN_WIDTH_MASK) >>
> +		    IEEE80211_VHTCAP_CHAN_WIDTH_SHIFT;
> +		local_ext_nss_bw_supp = (ic->ic_vhtcaps &
> +		    IEEE80211_VHTCAP_EXT_NSS_BW_MASK) >>
> +		    IEEE80211_VHTCAP_EXT_NSS_BW_SHIFT;
> +		local_supports_160 = IEEE80211_CHAN_160MHZ_ALLOWED(ni->ni_chan) &&
> +		    (local_chwidth == IEEE80211_VHTCAP_CHAN_WIDTH_160 ||
> +		    local_chwidth == IEEE80211_VHTCAP_CHAN_WIDTH_160_8080 ||
> +		    (local_ext_nss_bw_supp != 0 &&
> +		    (ic->ic_vht_tx_max_lgi_mbit_s &
> +		    IEEE80211_VHT_EXT_NSS_BW_CAPABLE) != 0));
>  
>  		/* See 802.11-2024 Table 9-314 */
>  		switch ((supp_chwidth << 4) | ext_nss_bw_supp) {
> @@ -2672,11 +2686,20 @@ ieee80211_setup_vhtop(struct ieee80211_n
>  
>  			diff = abs(ccf1 - ccfs0);
>  			if (diff == 8) {
> -				ni->ni_vht_chan_center_freq_idx0 = ccf1;
> +				if (local_supports_160) {
> +					ni->ni_vht_chan_center_freq_idx0 = ccf1;
> +					width = IEEE80211_VHTOP0_CHAN_WIDTH_160;
> +				}
>  				ni->ni_vht_chan_center_freq_idx1 = 0;
> -				width = IEEE80211_VHTOP0_CHAN_WIDTH_160;
>  			}
>  		} else if (width == IEEE80211_VHTOP0_CHAN_WIDTH_160) {
> +			if (!local_supports_160) {
> +				if (ni->ni_primary_chan < ccfs0)
> +					ni->ni_vht_chan_center_freq_idx0 = ccfs0 - 4;
> +				else if (ni->ni_primary_chan > ccfs0)
> +					ni->ni_vht_chan_center_freq_idx0 = ccfs0 + 4;
> +				width = IEEE80211_VHTOP0_CHAN_WIDTH_80;
> +			}
>  			ni->ni_vht_chan_center_freq_idx1 = 0;
>  		}
>  
> 
> 
> -- 
> wbr, Kirill
>