From: Peter Hessler <phessler@theapt.org>
Subject: Re: fix net80211 802.11g compatibility check
To: tech@openbsd.org
Date: Thu, 31 Jul 2025 17:42:34 +0200

On 2025 Jul 31 (Thu) at 16:16:49 +0200 (+0200), Stefan Sperling wrote:
:On Thu, Jul 31, 2025 at 12:26:48PM +0100, Tom Smyth wrote:
:> so it would be better to  check for at least one of the supported rates to
:> detect a particular standard of AP be it 802.11  b, or a or g or n or ac
:> etc...
:> 
:
:If we make any of the extended rates count, then we could use a
:simpler heuristic: Check for the presence of the "extended rates"
:info element in beacons, probe responses, assoc requests etc. on
:2GHz channels.
:

OK




:M  sys/dev/ic/qwx.c               |  1+   1-
:M  sys/net80211/ieee80211_node.c  |  7+  29-
:
:2 files changed, 8 insertions(+), 30 deletions(-)
:
:commit - 9af86e4b4d937c32c5d083ec0b7952c1b34fada6
:commit + 1403242634014294ccb5ea5de1aabc3d401721b2
:blob - f7921f80d7b005454efa677b714d90697dd06468
:blob + 6d640b2d7627eb188213ca0960b21ac99914f4fa
:--- sys/dev/ic/qwx.c
:+++ sys/dev/ic/qwx.c
:@@ -23135,7 +23135,7 @@ qwx_mac_vdev_start_restart(struct qwx_softc *sc, struc
: 	/* Deduce a legacy mode based on the channel characteristics. */
: 	if (IEEE80211_IS_CHAN_5GHZ(chan))
: 		arg.channel.mode = MODE_11A;
:-	else if (ieee80211_iserp_sta(ic->ic_bss))
:+	else if (ic->ic_bss->ni_flags & IEEE80211_NODE_ERP)
: 		arg.channel.mode = MODE_11G;
: 	else
: 		arg.channel.mode = MODE_11B;
:blob - c6ca10f5df7c13a01d8cddd8f552e3abf2b41184
:blob + 3a5f05057cc85ece31e8cd14ea58fd79445a68e4
:--- sys/net80211/ieee80211_node.c
:+++ sys/net80211/ieee80211_node.c
:@@ -2633,6 +2633,10 @@ ieee80211_setup_rates(struct ieee80211com *ic, struct 
: 		}
: 		memcpy(rs->rs_rates + rs->rs_nrates, xrates+2, nxrates);
: 		rs->rs_nrates += nxrates;
:+
:+		/* 11g support implies ERP support */
:+		if (nxrates > 0 && IEEE80211_IS_CHAN_2GHZ(ni->ni_chan))
:+			ni->ni_flags |= IEEE80211_NODE_ERP;
: 	}
: 	return ieee80211_fix_rate(ic, ni, flags);
: }
:@@ -2684,31 +2688,6 @@ ieee80211_node_addba_request_ac_vo_to(void *arg)
: 	ieee80211_node_addba_request(ni, EDCA_AC_VO);
: }
: 
:-/*
:- * Check if the specified node supports ERP / 802.11g.
:- */
:-int
:-ieee80211_iserp_sta(const struct ieee80211_node *ni)
:-{
:-	static const u_int8_t rates[] = { 2, 4, 11, 22, 12, 24, 48 };
:-	const struct ieee80211_rateset *rs = &ni->ni_rates;
:-	int i, j;
:-
:-	/*
:-	 * A STA supports ERP operation if it includes all the Clause 19
:-	 * mandatory rates in its supported rate set.
:-	 */
:-	for (i = 0; i < nitems(rates); i++) {
:-		for (j = 0; j < rs->rs_nrates; j++) {
:-			if ((rs->rs_rates[j] & IEEE80211_RATE_VAL) == rates[i])
:-				break;
:-		}
:-		if (j == rs->rs_nrates)
:-			return 0;
:-	}
:-	return 1;
:-}
:-
: #ifndef IEEE80211_STA_ONLY
: /*
:  * This function is called to notify the 802.1X PACP machine that a new
:@@ -2804,7 +2783,7 @@ ieee80211_count_nonerpsta(void *arg, struct ieee80211_
: 	if (ni->ni_associd == 0 || ni->ni_state == IEEE80211_STA_COLLECT)
: 		return;
: 
:-	if (!ieee80211_iserp_sta(ni))
:+	if ((ni->ni_flags & IEEE80211_NODE_ERP) == 0)
: 		(*nonerpsta)++;
: }
: 
:@@ -2857,7 +2836,7 @@ ieee80211_node_join_11g(struct ieee80211com *ic, struc
: 		    ether_sprintf(ni->ni_macaddr), longslotsta));
: 	}
: 
:-	if (!ieee80211_iserp_sta(ni)) {
:+	if ((ni->ni_flags & IEEE80211_NODE_ERP) == 0) {
: 		/*
: 		 * Joining STA is non-ERP.
: 		 */
:@@ -2874,8 +2853,7 @@ ieee80211_node_join_11g(struct ieee80211com *ic, struc
: 
: 		if (!(ni->ni_capinfo & IEEE80211_CAPINFO_SHORT_PREAMBLE))
: 			ic->ic_flags &= ~IEEE80211_F_SHPREAMBLE;
:-	} else
:-		ni->ni_flags |= IEEE80211_NODE_ERP;
:+	}
: }
: 
: void
:

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