[Olsr-users] 802.1Q vlan frames causing asymmetric neighbor problem

[Justin Lewis]

Hello,

First of all, thanks for the great software :)

I'm having a problem with olsrd on Android, which I am hoping I can get 
some help with. The problem is causing one of my devices to become and 
remain an asymmetric neighbor. I have 3 devices in my network:

- 192.168.1.95 (Linux box)
- 192.168.1.50 (Android device)
- 192.168.1.51 (Android device)

Now, .95 and .50 have no problems seeing each other, but neither of them 
can see .51, the problematic device. He sees .50 and .95 as asymmetric 
(from olsrd):

Received TC from NON SYM neighbor 192.168.1.95
Received TC from NON SYM neighbor 192.168.1.50

I can ping .51 from .50 and vice versa. I took a tcpdump and noticed the 
following on .50:

(spam-protected):~$ adb -s SH139PY05892 shell su -c "tcpdump -n -e"
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth0, link-type EN10MB (Ethernet), capture size 96 bytes
17:31:53.176326 90:21:55:56:77:fb > ff:ff:ff:ff:ff:ff, ethertype IPv4 
(0x0800), length 90: 192.168.1.50.698 > 192.168.1.255.698: OLSR, seq 
0xd320, length 48
17:31:54.401973 8c:77:12:a7:43:93 > ff:ff:ff:ff:ff:ff, ethertype 802.1Q 
(0x8100), length 78: vlan 0, p 6, ethertype IPv4, 192.168.1.51.698 > 
192.168.1.255.698: OLSR, seq 0x423e, length 32
17:31:55.143062 90:21:55:56:77:fb > ff:ff:ff:ff:ff:ff, ethertype IPv4 
(0x0800), length 74: 192.168.1.50.698 > 192.168.1.255.698: OLSR, seq 
0xd321, length 32
17:31:56.012782 8c:77:12:a7:43:93 > ff:ff:ff:ff:ff:ff, ethertype 802.1Q 
(0x8100), length 78: vlan 0, p 6, ethertype IPv4, 192.168.1.51.698 > 
192.168.1.255.698: OLSR, seq 0x423f, length 32

As you can see, .51 seems to be wrapping the HELLO packets with these 
802.1Q vlan frames. I have no idea what these are, or what to do about them.

I tested and have found the same behaviour on olsrd 0.6.6, 0.6.5, 0.6.4 
and 0.6.3, all compiled locally on an Ubuntu 10.04 x64_64 box and using 
the exact same config.

Interestingly, I have a pre-built binary of olsrd-0.6.3 (using exact 
same config) which does not exhibit this problem (the frames are not 
wrapped with the vlan tags). Here is the version output:

*** olsr.org -  pre-0.6.3-git_98cbd3d-hash_ ***
  Build date: 2012-06-27 17:21:39 on ubuntu

I looked for this hash in the git repo, but couldn't find it.

Does anyone have any idea about this? Is this a bug? I'd be really 
grateful if an expert could give me some pointers on this.

Cheers,
Justin