Fix the behavior of preferring weaker-but-still-good 5Ghz APs over

2Ghz APs because the 5Ghz band is generally less saturated.

The previous implementation was dependent upon the order of walking
APs.

ok stsp

diff --git a/sys/net80211/ieee80211_node.c b/sys/net80211/ieee80211_node.c
index c0675b1..f77766c 100644 (file)
--- a/sys/net80211/ieee80211_node.c
+++ b/sys/net80211/ieee80211_node.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: ieee80211_node.c,v 1.122 2017/12/08 21:16:01 stsp Exp $       */
+/*     $OpenBSD: ieee80211_node.c,v 1.123 2017/12/12 00:24:21 jcs Exp $        */
 /*     $NetBSD: ieee80211_node.c,v 1.14 2004/05/09 09:18:47 dyoung Exp $       */
 
 /*-
@@ -665,10 +665,12 @@ void
 ieee80211_end_scan(struct ifnet *ifp)
 {
        struct ieee80211com *ic = (void *)ifp;
-       struct ieee80211_node *ni, *nextbs, *selbs, *curbs;
+       struct ieee80211_node *ni, *nextbs, *selbs = NULL, *curbs = NULL,
+           *selbs2 = NULL, *selbs5 = NULL;
        int bgscan = ((ic->ic_flags & IEEE80211_F_BGSCAN) &&
            ic->ic_opmode == IEEE80211_M_STA &&
            ic->ic_state == IEEE80211_S_RUN);
+       uint8_t min_5ghz_rssi;
 
        if (ifp->if_flags & IFF_DEBUG)
                printf("%s: end %s scan\n", ifp->if_xname,
@@ -749,8 +751,6 @@ ieee80211_end_scan(struct ifnet *ifp)
                ieee80211_next_scan(ifp);
                return;
        }
-       selbs = NULL;
-       curbs = NULL;
 
        for (; ni != NULL; ni = nextbs) {
                nextbs = RBT_NEXT(ieee80211_tree, ni);
@@ -771,31 +771,34 @@ ieee80211_end_scan(struct ifnet *ifp)
                if (ieee80211_match_bss(ic, ni) != 0)
                        continue;
 
-               /* Pick the AP/IBSS match with the best RSSI. */
-               if (selbs == NULL)
-                       selbs = ni;
-               else if ((ic->ic_caps & IEEE80211_C_SCANALLBAND) &&
-                   IEEE80211_IS_CHAN_5GHZ(selbs->ni_chan) &&
+               if ((ic->ic_caps & IEEE80211_C_SCANALLBAND) &&
                    IEEE80211_IS_CHAN_2GHZ(ni->ni_chan) &&
-                   ni->ni_rssi > selbs->ni_rssi) {
-                       uint8_t min_rssi;
-
-                       /* 
-                        * Prefer 5GHz (with reasonable RSSI) over 2GHz since
-                        * the 5GHz band is usually less saturated.
-                        */
-                       if (ic->ic_max_rssi)
-                               min_rssi = IEEE80211_RSSI_THRES_RATIO_5GHZ;
-                       else
-                               min_rssi = (uint8_t)IEEE80211_RSSI_THRES_5GHZ;
+                   (selbs2 == NULL || ni->ni_rssi > selbs2->ni_rssi))
+                       selbs2 = ni;
+               else if ((ic->ic_caps & IEEE80211_C_SCANALLBAND) &&
+                   IEEE80211_IS_CHAN_5GHZ(ni->ni_chan) &&
+                   (selbs5 == NULL || ni->ni_rssi > selbs5->ni_rssi))
+                       selbs5 = ni;
+       }
 
-                       if (selbs->ni_rssi >= min_rssi)
-                               continue;
-               }
+       if (ic->ic_max_rssi)
+               min_5ghz_rssi = IEEE80211_RSSI_THRES_RATIO_5GHZ;
+       else
+               min_5ghz_rssi = (uint8_t)IEEE80211_RSSI_THRES_5GHZ;
 
-               if (ni->ni_rssi > selbs->ni_rssi)
-                       selbs = ni;
-       }
+       /*
+        * Prefer a 5Ghz AP even if its RSSI is weaker than the best 2Ghz AP
+        * (as long as it meets the minimum RSSI threshold) since the 5Ghz band
+        * is usually less saturated.
+        */
+       if (selbs5 && selbs5->ni_rssi > min_5ghz_rssi)
+               selbs = selbs5;
+       else if (selbs5 && selbs2)
+               selbs = (selbs5->ni_rssi >= selbs2->ni_rssi ? selbs5 : selbs2);
+       else if (selbs2)
+               selbs = selbs2;
+       else if (selbs5)
+               selbs = selbs5;
 
        if (bgscan) {
                struct ieee80211_node_switch_bss_arg *arg;