svn commit: r240946 - head/sys/dev/ath

Adrian Chadd adrian at FreeBSD.org
Wed Sep 26 03:45:43 UTC 2012


Author: adrian
Date: Wed Sep 26 03:45:42 2012
New Revision: 240946
URL: http://svn.freebsd.org/changeset/base/240946

Log:
  Map the non-QoS TID to the voice queue, in order to ensure important
  things like EAPOL frames make it out.
  
  After a whole bunch of hacking/testing, I discovered that they weren't
  being early-dropped by the stack (but I should look at ensuring that
  later..) but were even making to the hardware transmit queue.
  They were mostly even being received by the remote end.  However, the
  remote end was completely ignoring them.
  
  This didn't happen under 150-170MBit TCP tests as I'm guessing the TX
  queue stayed very busy and the STA didn't do any scanning. However, when
  doing 100Mbit/s of TCP traffic, the STA would do background scanning -
  which involves it coming in and out of powersave mode with the AP.
  
  Now, this is a total and utter hack around the real problems, which are:
  
  * I need to implement proper power save handling and integrate it into
    the filtered frames support, so the driver/stack doesn't send frames
    whilst the station is actually in sleep;
  
  * .. but frames were actually making it to the STA (macbook pro) and
    the AP did receive an ACK; but a tcpdump on the receiving side showed
    the EAPOL frame never made it. So the stack was dropping it for
    some reason;
  
  * Importantly - the EAPOL frames are currently going into the non-QoS
    TID, which maps to the BE queue and is susceptible to that queue being
    busy doing other things, but;
  
  * There's other traffic going on in the non-QoS TID from other contexts
    when scanning is going on and it's possible there's some races causing
    sequence number/IV issues, but;
  
  * Importantly importantlly, I think the interaction with TID 16 multicast
    traffic in power save mode is causing issues - since I -believe- the
    sequence number space being used by the EAPOL frames on TID 16 overlaps
    with the multicast frames that have sequence numbers allocated and
    are then stuffed on the cabq.  Since with EAPOL frames being in TID 16
    and queued to the BE queue, it's going to be waiting to be serviced
    with all of the aggregate traffic going on - and if the CABQ gets
    emptied beforehand, those TID 16 multicast frames with sequence numbers
    will go out beforehand.
  
  Now, there's quite likely a bunch of "stuff happening slightly out of
  sequence" going on due to the nature of the TX path (read: lots of
  overlapping and concurrent ath_start() and ath_raw_xmit() calls going
  on, sigh) but I thought I had caught them all and stuffed each TID TX
  behind a lock (that lasted as long as it needed to in order to get
  the frame onto the relevant destination queue - thus keeping things
  in order.)
  
  Unfortunately the last problem is the big one and I'm going to stare at
  it some more.  If it _is_
  
  So this is a work around for now to ensure that EAPOL frames actually
  make it out before any other stuff in the non-QoS TID and HOPEFULLY
  before the CABQ gets active.
  
  I'm now going to spend a little time in the TX path figuring out exactly
  why the sender is rejecting things. There's two (well, three if you count
  EAPOL contents invalid) possibilities:
  
  * The sequence number is out of order (ie, something else like the multicast
    traffic on CABQ) is going out first on TID 16;
  * The CCMP IV is out of order (similar to above - but less likely,  as the
    TX key for multicast traffic is different to unicast traffic);
  * EAPOL contents strangely invalid.
  
  AP: Ubiquiti RSPRO, AR9160/AR9220 NICs
  STA: Macbook Pro, Broadcom 11n NIC

Modified:
  head/sys/dev/ath/if_ath_tx.c

Modified: head/sys/dev/ath/if_ath_tx.c
==============================================================================
--- head/sys/dev/ath/if_ath_tx.c	Wed Sep 26 01:09:19 2012	(r240945)
+++ head/sys/dev/ath/if_ath_tx.c	Wed Sep 26 03:45:42 2012	(r240946)
@@ -106,6 +106,11 @@ __FBSDID("$FreeBSD$");
  */
 #define	SWMAX_RETRIES		10
 
+/*
+ * What queue to throw the non-QoS TID traffic into
+ */
+#define	ATH_NONQOS_TID_AC	WME_AC_VO
+
 static int ath_tx_ampdu_pending(struct ath_softc *sc, struct ath_node *an,
     int tid);
 static int ath_tx_ampdu_running(struct ath_softc *sc, struct ath_node *an,
@@ -191,7 +196,7 @@ ath_tx_getac(struct ath_softc *sc, const
 	if (IEEE80211_QOS_HAS_SEQ(wh))
 		return pri;
 
-	return WME_AC_BE;
+	return ATH_NONQOS_TID_AC;
 }
 
 void
@@ -2861,7 +2866,7 @@ ath_tx_tid_init(struct ath_softc *sc, st
 		atid->cleanup_inprogress = 0;
 		atid->clrdmask = 1;	/* Always start by setting this bit */
 		if (i == IEEE80211_NONQOS_TID)
-			atid->ac = WME_AC_BE;
+			atid->ac = ATH_NONQOS_TID_AC;
 		else
 			atid->ac = TID_TO_WME_AC(i);
 	}


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