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From: Dmitry Vyukov <dvyukov@google.com>
Date: Mon, 8 Jan 2018 13:01:16 +0100
Message-ID: <CACT4Y+bn8U1KcwLVp3unxMOa8gx_zeS92DQx9vrofwN7Ut2F4Q@mail.gmail.com>
Subject: Re: LKML admins (syzbot emails are not delivered)
To: "Theodore Ts'o" <tytso@mit.edu>,
        Dmitry Vyukov <dvyukov@google.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        syzkaller <syzkaller@googlegroups.com>,
        David Miller <davem@davemloft.net>
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Sender: linux-kernel-owner@vger.kernel.org

On Fri, Jan 5, 2018 at 12:50 AM, Theodore Ts'o <tytso@mit.edu> wrote:
> On Thu, Jan 04, 2018 at 12:04:34PM +0100, Dmitry Vyukov wrote:
>>
>> The problem is that it's not _me_, it's a computer program which uses
>> some mail delivery system which I don't have full visibility into. I
>> don't know if it even gets bounce emails (as far as I understand it's
>> not LKML that generates them, LKML SMTP server just returns some error
>> code and then it's a responsibility of somebody else to represent it
>> by a reply email). If the only way to probe the behavior is to send
>> actual emails to LKML (which have high chances to be actually
>> delivered to all subscribers), it makes testing somewhat problematic.
>
> It looks like you're using the App Engine Mail API.  You can configure
> it to get bounce e-mails[1].  From what I can tell looking at the mail
> headers, the mail gets sent via an intermediate SMTP host, such as
> mail-it0-f69.google.com before it is delievered to vger.  So if vger's
> mailer bounces it via an SMTP error, it would be
> mail-it0-f69.google.com's responsibility to generate a bounce message,
> which you then should be able to catch.
>
> [1] https://cloud.google.com/appengine/docs/standard/go/mail/bounce
>
> You should be able to test this by having your app-engine send a
> message to "invalid-address@vger.kernel.org".  I've verified that this
> will cause an immediate SMTP error:
>
> 554 5.0.0 Hi [74.207.234.97], unresolvable address: <invalid-address@vger.kernel.org>; nosuchuser; invalid-address@vger.kernel.org
>
> If it doesn't, you should file an internal bug report since that's
> clearly a bug in the App Engine's mail infrastructure.  If you can't
> get satisfaction that way, my recommendation would be to set up an
> Linode server (you can't use GCE because GCE blocks outgoing SMTP
> connections) to be your mail gateway, and send the notifications from
> a domain such as syzkaller.org, where you have full control of your
> mail infrastructure, and you don't have to deal with nonsense such as
> DMARC.


Thanks, Ted! This is helpful. I've added handler for bounce emails:
https://github.com/google/syzkaller/commit/19c05fffcb1860b2dcf17989b40ca16ed259fdea
And I do see them after sending to invalid-address@vger.kernel.org. So
now hopefully it will sched some light when we get another bounce.