Introduce ieee80211_min_basic_rate() and ieee80211_max_basic_rate().

These helpers can be used by drivers to improve compatibility with APs
that disable some mandatory PHY rates in the basic rate set.

For instance, many of our drivers hard-code 11b rates on 2 Ghz and run
into problems when APs disable them. Since 11b rates are being disabled
by default by some vendors, hardcoding them is not a good idea anymore.

ok mpi@ phessler@

2 files changed, 41 insertions, 2 deletions

diff --git a/sys/net80211/ieee80211.c b/sys/net80211/ieee80211.c
index e330f8ec954..a5da6f1050b 100644
--- a/sys/net80211/ieee80211.c
+++ b/sys/net80211/ieee80211.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: ieee80211.c,v 1.58 2016/01/13 14:33:07 stsp Exp $	*/
+/*	$OpenBSD: ieee80211.c,v 1.59 2017/05/30 11:00:38 stsp Exp $	*/
 /*	$NetBSD: ieee80211.c,v 1.19 2004/06/06 05:45:29 dyoung Exp $	*/
 
 /*-
@@ -712,6 +712,43 @@ ieee80211_setbasicrates(struct ieee80211com *ic)
 	}
 }
 
+int
+ieee80211_min_basic_rate(struct ieee80211com *ic)
+{
+	struct ieee80211_rateset *rs = &ic->ic_bss->ni_rates;
+	int i;
+
+	for (i = 0; i < rs->rs_nrates; i++) {
+		if (rs->rs_rates[i] & IEEE80211_RATE_BASIC)
+			return i;
+	}
+
+	return 0;
+}
+
+int
+ieee80211_max_basic_rate(struct ieee80211com *ic)
+{
+	struct ieee80211_rateset *rs = &ic->ic_bss->ni_rates;
+	int i, best, rval, best_rval;
+
+	/* Defaults to 1 Mbit/s on 2GHz and 6 Mbit/s on 5GHz. */
+	best = 0;
+	best_rval = (rs->rs_rates[best] & IEEE80211_RATE_VAL);
+
+	for (i = 0; i < rs->rs_nrates; i++) {
+		if ((rs->rs_rates[i] & IEEE80211_RATE_BASIC) == 0)
+			continue;
+		rval = (rs->rs_rates[i] & IEEE80211_RATE_VAL);
+		if (rval > best_rval) {
+			best_rval = rval;
+			best = i;
+		}
+	}
+
+	return best;
+}
+
 /*
  * Set the current phy mode and recalculate the active channel
  * set based on the available channels for this mode.  Also
diff --git a/sys/net80211/ieee80211_var.h b/sys/net80211/ieee80211_var.h
index 627eaebc8f9..7d6bb1bd85e 100644
--- a/sys/net80211/ieee80211_var.h
+++ b/sys/net80211/ieee80211_var.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: ieee80211_var.h,v 1.77 2017/02/02 16:47:53 stsp Exp $	*/
+/*	$OpenBSD: ieee80211_var.h,v 1.78 2017/05/30 11:00:38 stsp Exp $	*/
 /*	$NetBSD: ieee80211_var.h,v 1.7 2004/05/06 03:07:10 dyoung Exp $	*/
 
 /*-
@@ -402,6 +402,8 @@ u_int	ieee80211_mhz2ieee(u_int, u_int);
 u_int	ieee80211_chan2ieee(struct ieee80211com *,
 		const struct ieee80211_channel *);
 u_int	ieee80211_ieee2mhz(u_int, u_int);
+int	ieee80211_min_basic_rate(struct ieee80211com *);
+int	ieee80211_max_basic_rate(struct ieee80211com *);
 int	ieee80211_setmode(struct ieee80211com *, enum ieee80211_phymode);
 enum ieee80211_phymode ieee80211_next_mode(struct ifnet *);
 enum ieee80211_phymode ieee80211_chan2mode(struct ieee80211com *,