On Sat, 27 Oct 2018 13:36:17 -0300, David Bremner wrote:

> > Source: nullmailer
> > Version: 1:2.1-7
> > Severity: serious
> > Tags: ftbfs
> >
> > From my pbuilder build log:
> 
> It's not reproducible in for me sbuild. I guess there's something
> pbuilder specific about this failer. Of course I'd like a fix, but I'll
> need to be convinced it's RC.

I can reproduce the failure, unsurprisingly, as I'm using cowbuilder.

If I'm understanding the tests correctly, the failure is:

Running test /build/nullmailer-2.1/test/tests/protocols...
…
Testing host not found error with smtp.
Result was 5, should be 2.

And this comes from test/tests/protocols:

        echo "Testing host not found error with $p."
        error 2 protocol $p --host=this.host.can.not.exist 3<testmail

which seems to imply that the expected error code is something like
"non existing host" whereas in practice this is "no response from any
DNS server" -- I'm guessing here, but I see lots of (failing)
attempts to talk to DNS servers, and those connection attempts are
policy violations themselves in my understanding.


When playing around a bit (with giving an IP address to this.host.can.not.exist
in /etc/hosts in the chroot) I get:

# ./runtests tests/protocols 
Running test tests/protocols...
…
Testing host not found error with smtp.
Result was 7, should be 2.
******************************Failed!******************************


Ah, the error codes are from lib/errcodes.h:
#define ERR_HOST_NOT_FOUND 2    // gethostbyname failed with HOST_NOT_FOUND
#define ERR_GHBN_TEMP 5         // gethostbyname failed with TRY_AGAIN
#define ERR_CONN_REFUSED 7      // connect failed with ECONNREFUSED


While not pretending to understand fully what's going on here, I'm
quite sure that
- the problems are related to DNS resolution (of
  this.host.can.not.exist)
- that calling out to DNS servers is not only unreliable but also a
  policy violation
- that the bug is really connected to sbuild, {p,cow}builder, etc.


Cheers,
gregor

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