[Olsr-users] problem with asymmetric link

[Klaus Darilion]

Hi!

I want to simulate an ad-hoc net in my LAN. Therefore I have set up 3 
VWware linux boxes on my PC with olsrd 0.5.6-rc7 and did some tests.

    Host A: 10.10.0.151, 00:0C:29:CA:D1:41
    Host B: 10.10.0.152, 00:0c:29:03:5f:d4
    Host C: 10.10.0.153, 00:0C:29:E9:09:B6

1. First test:

    A <----> B
    ^        ^
    |        |
     \      /
      ->C<-

I start olsrd on all 3 boxes and everything works fine - that means: 
Every olsrd finds the other ones and they are added as host route to the 
routing table.


2. Now, I want to simulate the following - no link between A to C.

    A <----> B
             ^
             |
            /
        C<-

Therefore I added iptables rules to C to block incoming packets with 
source-MAC from A, and vice versa:

C# iptables -A INPUT -m mac --mac-source 00:0C:29:CA:D1:41 -j DROP
A# iptables -A INPUT -m mac --mac-source 00:0C:29:E9:09:B6 -j DROP

Now I start olsrd on all 3 boxes. Everthink works fine. A reports a link 
to B and a two hop neighbor C. There is also a GH route to C via B. A 
and C can ping each other.


3. Now, I want to simulate the following - no link from A to C.

    A <----> B
    ^        ^
    |        |
     \      /
      --C<-

Therefore I only add an iptables rule to C to block incoming packets 
with source-MAC from A:

C# iptables -A INPUT -m mac --mac-source 00:0C:29:CA:D1:41 -j DROP

Now I start olsrd on all 3 boxes. I would think that A should find a 
route to C via B, and C should find a route to A directly. But this is 
not the case.
A only finds links between A and B, and from B to C.
B finds links between A and B, and B and C.
C finds links between A and B, and B and C.

Why does C not find the link from C to A?
Why does A not find the link from C to A?
Why does A not find the link from C to B?

Is this the intended behavior? Below is the debug output.

thanks
Klaus

olsrd output PC A (.151)
===============================
--- 16:15:08.666736 ---------------------------------------------------- 
LINKS

IP address       hyst         LQ       ETX
10.10.0.152      0.000  1.000/0.718    1.393
10.10.0.153      0.000  1.000/0.000    INFINITE

--- 16:15:08.666791 ----------------------- TWO-HOP NEIGHBORS

IP addr (2-hop)  IP addr (1-hop)  Total cost
10.10.0.152      10.10.0.153      INFINITE
10.10.0.153      10.10.0.152      2.920

--- 16:15:08.666821 ------------------------------------------------- 
TOPOLOGY

Source IP addr  Dest IP addr          LQ        ETX
10.10.0.151     10.10.0.152     1.000/0.718    1.393
10.10.0.152     10.10.0.151     0.718/1.000    1.393
10.10.0.152     10.10.0.153     0.682/1.000    1.466



olsrd output PC B (.152)
===============================
--- 17:51:43.350598 ---------------------------------------------------- 
LINKS

IP address       hyst         LQ       ETX
10.10.0.153      0.000  0.643/1.000    1.555
10.10.0.151      0.000  0.608/1.000    1.645

--- 17:51:43.350637 ----------------------- TWO-HOP NEIGHBORS

IP addr (2-hop)  IP addr (1-hop)  Total cost

--- 17:51:43.350648 ------------------------------------------------- 
TOPOLOGY

Source IP addr  Dest IP addr          LQ        ETX
10.10.0.151     10.10.0.152     1.000/0.659    1.518
10.10.0.152     10.10.0.151     0.561/1.000    1.783
10.10.0.152     10.10.0.153     0.643/1.000    1.555
10.10.0.153     10.10.0.152     1.000/0.553    1.808


olsrd output PC C (.153)
===============================
--- 18:08:28.539149 ---------------------------------------------------- 
LINKS

IP address       hyst         LQ       ETX
10.10.0.152      0.000  1.000/0.549    1.821

--- 18:08:28.539187 ----------------------- TWO-HOP NEIGHBORS

IP addr (2-hop)  IP addr (1-hop)  Total cost
10.10.0.151      10.10.0.152      3.753

--- 18:08:28.539224 ------------------------------------------------- 
TOPOLOGY

Source IP addr  Dest IP addr          LQ        ETX
10.10.0.151     10.10.0.152     1.000/0.627    1.594
10.10.0.152     10.10.0.151     0.518/1.000    1.932
10.10.0.152     10.10.0.153     0.596/1.000    1.678
10.10.0.153     10.10.0.152     1.000/0.549    1.821