> On Thu, Oct 22, 2015 at 10:37:53PM -0700, Tim Hockin wrote:
> > I saw from a different thread that musl doesn't or didn't do TCP
> > fallbacks - is that still the case?  I know we need that for things
> > like large multi-SRV sets (which I do not expect libc to support), and
> > we have some people who have large A sets (which I do expect libc to
> > support).

>Indeed. The only way you can overflow the UDP size limit with the
>records the stub resolver uses is with a max-length CNAME pointing to
>a max or near-max length record with little or no overlap to allow for
>compression.

Most DNS servers are actually well able to send records greater than 512 bytes over UDP. This is part of the EDNS0 DNS extension. I think it's worth discussing to implement EDNS0 in the musl resolver. Codewise you just have to set the UDP receive buffer to the desired size and include an OPT RR in every query indicating the supported max UDP size.