Maintained by: NLnet Labs

EDNS RRs

W.C.A. Wijngaards
Fri Nov 20 11:34:30 CET 2015


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Hi,

On 11/20/2015 10:11 AM, W.C.A. Wijngaards via Unbound-users wrote:
> Hi Ian,
> 
> On 11/19/2015 09:47 PM, Ian Cohee via Unbound-users wrote:
>> Hello all,
> 
>> One of our engineers discovered some interesting behavior while 
>> testing bad EDNS RRs in Unbound. He discovered that Unbound 
>> properly checks and identifies a truncated OPT RR as a FORMERR,
>> but then returns the truncated OPT RR, resulting in a malformed 
>> response to a malformed request. I have attached a PCAP file
>> that should contain the malformed requests/responses.
> 
> There is a fix now, unbound will remove the EDNS section from that
> reply.
> 
> This may cause the sender to think the server does not support
> EDNS and then drop EDNS from its queries - and that is exactly
> right because its EDNS contents cannot be parsed.

And fixed to reply with a valid EDNS record without options in it in
the FORMERR message.  This is for RFC compliance, as Yuri points out.

Best regards, Wouter

> 
> Best regards, Wouter
> 
> 
>> Has anyone observed this behavior, and if so, had issues from
>> it?
> 
>> I'd also like to hear some opinions about this behavior.
> 
>> Thanks,
> 
> 
> 

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