#4131 BLOC First D: WLAN appears to die after some number of suspend/resumes

Zarro Boogs per Child bugtracker at laptop.org
Wed Oct 17 15:42:41 EDT 2007


#4131: WLAN appears to die after some number of suspend/resumes
-----------------------+----------------------------------------------------
  Reporter:  wad       |       Owner:  jcardona              
      Type:  defect    |      Status:  assigned              
  Priority:  blocker   |   Milestone:  First Deployment, V1.0
 Component:  wireless  |     Version:                        
Resolution:            |    Keywords:  mesh                  
  Verified:  0         |  
-----------------------+----------------------------------------------------
Changes (by jcardona):

  * owner:  rchokshi => jcardona
  * status:  new => assigned


Comment:

 The following was observed on one of the devices under test that failed:

  1. dut does not wake up via wireless.
  2. dut does wake up via power button.
  3. while dut awake it cannot ping other nodes in infrastructure.
  4. sniffer reveals that ARP packets are being transmitted, but no
 response is received.
  5. after populating the arp table manually ICMP echo requests starts
 being transmitted ({{{dut MAC: 00:17:c4:05:2d:fa}}})

 {{{
 sniff at sniff:~$ sudo tcpdump -i ath1 -s 1500 -e | grep -i
 SA:00:17:c4:05:2d:fa

 15:35:38.328464 DA:00:13:10:7d:b5:fb (oui Unknown) SA:00:17:c4:05:2d:fa
 (oui Unknown) BSSID:02:2f:af:93:ef:6b (oui Unknown) LLC, dsap SNAP (0xaa),
 ssap SNAP (0xaa), cmd 0x03: oui Ethernet (0x000000), ethertype IPv4
 (0x0800): 192.168.5.62 > 192.168.5.2: ICMP echo request, id 19724, seq
 514, length 64
 }}}

  6. sniffer reveals no reply is transmitted to the dut:

 {{{
 sniff at sniff:~$ sudo tcpdump -i ath1 -s 1500 -e | grep -i
 RA:00:17:c4:05:2d:fa

 15:37:23.590191 RA:00:17:c4:05:2d:fa (oui Unknown) Acknowledgment
 <only 802.11 acknowledgments>
 }}}

  7. sniffer reveals that AP (b5:fb), instead sending data to dut, is
 sending it to another AP (b5:fd).  Lazy-WDS can cause routing loops, and
 this appears to be what we see here:

 {{{
 sniff at sniff:~$ sudo tcpdump -i ath1 -s 1500 -e | grep -i
 DA:00:17:c4:05:2d:fa

 15:29:50.253762 RA:00:17:c4:05:2c:e3 (oui Unknown) TA:00:13:10:7d:b5:fd
 (oui Unknown) DA:00:17:c4:05:2d:fa (oui Unknown) SA:00:13:10:7d:b5:fb (oui
 Unknown) LLC, dsap Unknown (0x10), ssap Unknown (0xfa), cmd 0xaaaa:
 Information, send seq 85, rcv seq 85, Flags [Command, Poll], length 94
 }}}

 This is certainly one problem.  If this is the '''only''' problem causing
 the symptoms described in this ticket, pinging over the mesh should work
 (the description of the ticket says it does not).

 Can someone verify?

 '''Suggestion:'''  Can't we blacklist this AP?  Or provide a firmware
 image for it (this model's firmware can be replaced by
 [http://openwrt.org/ OpenWRT]) with Lazy-WDS disabled?  The Lazy-WDS
 "feature" on the WRT54G is not based on any standard, not documented and
 has well known weaknesses.

-- 
Ticket URL: <https://dev.laptop.org/ticket/4131#comment:7>
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