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On Tue, Oct 18, 2005 at 05:00:52PM -0400, Steven M. Bellovin wrote:
> Sometimes, it works very well; in my house over the weekend (two access 
> points, with WEP), it worked flawlessly.  Other places, it's worked 
> poorly or not at all, so much so that I'm contemplating starting to 
> travel with a wi card again.

Steve,

I think I have figured it out by re-reading some logs Perry sent me.
I will tell you what I think is happening.  When ath(4) doesn't receive
the AP's beacon for a while, it times out and tries to reassociate with
the AP.  In a zone where there's 802.11 congestion, your ath might
miss a lot of beacons and time-out often.  Congestion may also cause
reassociation to fail.  If reassociation fails, then ath will scan
for access points again.  This is where things go haywire: a bug in
the scanning code makes ath disregard your AP, because it failed to
associate with it, until the AP is flushed from the scan table with
ifconfig down/up.

You and Perry should try this patch.

Dave

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David Young             OJC Technologies
dyoung@ojctech.com      Urbana, IL * (217) 278-3933

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Index: ieee80211_node.c
===================================================================
RCS file: /cvsroot/src/sys/net80211/ieee80211_node.c,v
retrieving revision 1.44
diff -u -u -r1.44 ieee80211_node.c
--- ieee80211_node.c	25 Sep 2005 00:03:06 -0000	1.44
+++ ieee80211_node.c	18 Oct 2005 22:18:24 -0000
@@ -619,7 +619,7 @@
 ieee80211_end_scan(struct ieee80211com *ic)
 {
 	struct ieee80211_node_table *nt = &ic->ic_scan;
-	struct ieee80211_node *ni, *selbs;
+	struct ieee80211_node *next_ni, *ni, *selbs;
 
 	ieee80211_cancel_scan(ic);
 	ieee80211_notify_scan_done(ic);
@@ -707,7 +707,8 @@
 	IEEE80211_DPRINTF(ic, IEEE80211_MSG_SCAN, "\t%s\n",
 	    "macaddr          bssid         chan  rssi rate flag  wep  essid");
 	IEEE80211_NODE_LOCK(nt);
-	TAILQ_FOREACH(ni, &nt->nt_node, ni_list) {
+	for (ni = TAILQ_FIRST(&nt->nt_node); ni != NULL; ni = next_ni) {
+		next_ni = TAILQ_NEXT(ni, ni_list);
 		if (ni->ni_fails) {
 			/*
 			 * The configuration of the access points may change
@@ -718,11 +719,8 @@
 				"%s: skip scan candidate %s, fails %u\n",
 				__func__, ether_sprintf(ni->ni_macaddr),
 				ni->ni_fails);
-			ni->ni_fails++;
-#if 0
 			if (ni->ni_fails++ > 2)
 				ieee80211_free_node(ni);
-#endif
 			continue;
 		}
 		if (ieee80211_match_bss(ic, ni) == 0) {

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