[Olsr-dev] Feedback on current OL

David Murray (spam-protected)
Mon Jun 9 12:34:52 CEST 2008

Quoting Hannes Gredler <(spam-protected)>:

> hmm (as bernd has stated) olsrd just passes any outgoing OLSR packet 
> down the UDP
> network stack and relies on the kernel (or a offload driver)
> to calculate the UDP checksum.
> looks like something is broken there.

I think you are correct there, just fired up another machine running 
OLSRD over the same link/switch. Wireshark on that machine is not 
showing any errors. Looks like the problem is related to just that 

This new machine is getting a metric of 1.061 over the Ethernet link 
instead of 1.150 like the suspect machine. Just a question, why is the 
metric 1.061 instead of 1.000. I think that it is unlikely that an 
uncongested Ethernet link would drop a packet.

> /hannes
> David Murray wrote:
>> Quoting Hannes Gredler <(spam-protected)>:
>>> david,
>>> did you see UDP checksum errors in outgoing or incoming packets ?
>> They are outgoing hellos. The interface is an Ethernet Interface.
>>> /hannes
>>> David Murray wrote:
>>>> Hi guys, just a bit of feedback on the latest development branch 
>>>> found here [1]. I have had it running in my test setup (8 dual 
>>>> radio ALIX nodes) for about 3-4 days. It seems to be working 
>>>> great, however, one problem I have found is with the the metric.
>>>> Currently, I have a 100mbit Ethernet link that is being given a 
>>>> metric of ~1.150. Iperf shows that this link provides ~100 mbit 
>>>> which means that there is nothing physically wrong with the link. 
>>>> To investigate a little further I pulled up wireshark and took a 
>>>> look at the OLSR hellos.
>>>> The wireshark output was showing some UDP checksum errors "maybe 
>>>> caused by UDP checkum offload" on some olsr hello packets. Perhaps 
>>>> if anyone else is using this branch they could confirm whether 
>>>> they are also getting the errors or if it is something specific 
>>>> with my equipment.
>>>> Thanks
>>>> Dave
>>>> [1] http://gredler.at/hg/olsrd/archive/tip.tar.gz

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