Re: Psql wants to use IP6 when connecting to self using tcp...

On 2021-06-23 20:33:33 -0400, Tom Lane wrote:
> Jerry LeVan <jerry(dot)levan(at)gmail(dot)com> writes:
> > bigbox has a freshly installed Fedora 34 system and it runs postgresql 13.3
>
> > the following are being run ON bigbox
>
> > nslookup bigbox returns the correct ipv4 address
> > nslookup bigbox.skynet returns the correct ipv4 address
>
> > psql -h bigbox.skynet allows me to connect to the database
> > psql -h bigbox fails because the ipv6 address is returned and there is no hba entry..
>
> It's quite odd that nslookup isn't agreeing with glibc's name
> resolution code.

AFAIK nslookup uses only DNS. Glibc uses all methods in nsswitch.conf.
Typically that also includes "files", and at least on Debian/Ubuntu that
has higher priority than "dns", which is why I advised the OP to
check /etc/hosts. As Alan noted, mdns4_minimal is also often there and
might return spurious results.

> I suspect that the problem lies with systemd,

This is the next one, yes. On my Ubuntu laptop, the hosts line reads:

hosts:
files
mdns4_minimal [NOTFOUND=return]
resolve [!UNAVAIL=return]
dns
myhostname
mymachines

(wrapped for readability)

So glibc first looks in /etc/hosts, then does an MDNS (Avahi) lookup,
then asks systemd-resolved, and only then gets around to do a
traditional DNS lookup.

(And systemd-resolved does do some magic for the local hostname, so that
might indeed be the problem)

hp

--
_ | Peter J. Holzer | Story must make more sense than reality.
|_|_) | |
| | | hjp(at)hjp(dot)at | -- Charles Stross, "Creative writing
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