Add comment explaining why we read basic MCS set only from beacon/probereq.

requested by mpi@

diff --git a/sys/net80211/ieee80211_node.c b/sys/net80211/ieee80211_node.c
index d3164e8..6fcbf93 100644 (file)
--- a/sys/net80211/ieee80211_node.c
+++ b/sys/net80211/ieee80211_node.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: ieee80211_node.c,v 1.139 2018/08/07 18:13:14 stsp Exp $       */
+/*     $OpenBSD: ieee80211_node.c,v 1.140 2018/08/11 10:58:39 stsp Exp $       */
 /*     $NetBSD: ieee80211_node.c,v 1.14 2004/05/09 09:18:47 dyoung Exp $       */
 
 /*-
@@ -1940,6 +1940,11 @@ ieee80211_setup_htop(struct ieee80211_node *ni, const uint8_t *data,
        ni->ni_htop1 = (data[2] | (data[3] << 8));
        ni->ni_htop2 = (data[3] | (data[4] << 8));
 
+       /*
+        * According to 802.11-2012 Table 8-130 the Basic MCS set is
+        * only "present in Beacon, Probe Response, Mesh Peering Open
+        * and Mesh Peering Confirm frames. Otherwise reserved."
+        */
        if (isprobe)
                memcpy(ni->ni_basic_mcs, &data[6], sizeof(ni->ni_basic_mcs));