Re: Re: [BUGS] BUG #13611: test_postmaster_connection failed (Windows, listen_addresses = '0.0.0.0' or '::')

On Mon, Oct 12, 2015 at 08:07:37PM -0400, Tom Lane wrote:
> Robert Haas <robertmhaas@gmail.com> writes:
> > On Fri, Oct 9, 2015 at 10:16 PM, Noah Misch <noah@leadboat.com> wrote:
> >> The listening side is in good shape today.  This thread is about the address
> >> that pg_ctl uses in PQping("host=...").  Listening on 0.0.0.0 is portable.
> >> PQping("host='0.0.0.0'") relies on non-portable semantics in the underlying
> >> connect() syscall.  PQping("host='127.0.0.1'") is a portable substitute.
> 
> > Ah.  So in this case 0.0.0.0 is interpreted to mean "any IP that's a
> > way to reach the local host", and using 127.0.0.1 makes sense because
> > we know that will always be one of them?  I could buy that line of
> > reasoning.
> 
> I do *not* buy that we can safely replace "localhost" by "127.0.0.1".

Nobody proposed that.  The word "localhost" did not appear in this thread.

> Consider a system that's only set up with IPv6 local addressing.
> 
> AFAICS the complaint in this bug is about a system with broken DNS (ie,
> unable to resolve "localhost" properly, which is something mandated by
> relevant RFCs, I believe).

The original post used only "0.0.0.0" and "::", not "localhost" or anything
else entailing name resolution.  As I wrote above, Kondo proposed for pg_ctl
to use PQping("host='127.0.0.1'") in place of PQping("host='0.0.0.0'").
That's all.  pg_ctl would continue to use PQping("host='localhost'") where
it's doing so today.  A patch that changes the 0.0.0.0 case in this way should
also change PQping("host='::'") to PQping("host='::1'"); I suspect that was
implicit in the original proposal.

nm