[dns-operations] NS1 nameservers response size

Paul Vixie paul at redbarn.org
Fri May 24 13:16:45 UTC 2019

On Friday, 24 May 2019 11:34:38 UTC Mark Andrews wrote:
> ...
> > On 24 May 2019, at 21:10, Jan Včelák <jv at fcelda.cz> wrote:
> > I can confirm we do not respect the buffer size. We are aware of this
> > deficiency but it also doesn't have high priority at the moment.
> > 
> > Have you encountered a situation where it has been causing trouble for a
> > real application? Or is this an accidental discovery?

when they tell you their buffer size, they are telling you that nothing larger 
than that will be received. this signaling is not advisory; if you ignore it, 
your response will appear to be truncated or malformed (if you're lucky).

you would literally be better off, and more correct, if you just ignored or 
servfailed any query whose buffer size parameter was smaller than your 
intended answer. (or you could respond with TC=1 and no answers.)


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