[ovs-discuss] RSTP may send BPDUs with uninitialized bytes

David van Moolenbroek dvmoolenbroek at aimvalley.nl
Tue Jun 5 11:42:56 UTC 2018


Ben,

On 6/4/2018 10:43 PM, Ben Pfaff wrote:
> Thanks for the report.  I think that all of these problems are easy to
> fix.  I sent a patch:
>          https://patchwork.ozlabs.org/patch/925221/
>
> If it is convenient for you to test, I'd be pleased to hear whether this
> fixes the problems you observed with the noncompliant implementation you
> mentioned.

Thank you for the patch! I can confirm that, when applied to the 
customized OVS 2.5.0 source on the ethernet switch, the patch resolves 
all our issues. I should mention there that the customized code does its 
own frame padding, so what I ended up testing does not qualify as a 
proper test for OVS itself, but it certainly looks good.

Just for completeness, I feel obliged to remark that while OVS now does 
generate RSTP BPDUs with the correct ethernet frame length field (39 
bytes), the Configuration and TCN BPDUs are still sent out with extra 
bytes (namely, with a length of 39 bytes instead of 38 and 7 bytes 
respectively). That has not been a problem during our experiments, but 
it might still be worth fixing, e.g. with offsetof() or a #define for 
those BPDUs' lengths or so. Either way, we are very happy with this fix 
- thank you again!

Kind regards,
David

-- 
Dr. David C. van Moolenbroek
Software Developer, AimValley
https://www.aimvalley.com/



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