Re: Neon and reverse address lookup

[ludo@gnu.org (Ludovic Courtès)]

Mark H Weaver <mhw@netris.org> skribis:

> Andreas Enge <andreas@enge.fr> writes:
>
>> when trying to package the neon library:
>>    http://www.webdav.org/neon/ ,
>> the tests fail inside the chroot with
>>    addr_reverse (reverse lookup for 127.0.0.1 failed)
>>
>> Should I disable the corresponding test?
>
> I think we should include /etc/hosts in the chroot with an entry for
> localhost.  We might also need /etc/nsswitch.conf; I'm not sure.  I see
> no reason not to do this, and I suspect it would ultimately take less
> time and effort than disabling tests.

Actually, I just discovered that it’s been the case since before Guix
was even started.  :-)

nix/libstore/build.cc reads this:

      /* Create /etc/hosts with localhost entry. */
      writeFile(chrootRootDir + "/etc/hosts", "127.0.0.1 localhost\n");

So lookups of ‘localhost’ should just work.

To make sure this is the case, try this:

--8<---------------cut here---------------start------------->8---
#!/path/to/bin/guile -s
!#

(use-modules (guix) (guix monads))

(define (with-/etc/hosts?)
  (define b
    '(and (file-exists? "/etc/hosts")
          (getaddrinfo "localhost")
          (call-with-output-file (assoc-ref %outputs "out")
            (const #t))))

  (mlet* %store-monad ((d (derivation-expression "etc-hosts" b)))
    (built-derivations (list d))))

(let* ((s (open-connection)))
  (run-with-store s (with-/etc/hosts?)))
--8<---------------cut here---------------end--------------->8---

I don’t think nsswitch.conf will be necessary.

Thanks,
Ludo’.