[Dovecot] 2.0.beta4, Panic: stream doesn't support seeking backwards (and beta5 too)

[Mark Sapiro]

On Monday, May 10, Mark Sapiro wrote:
> On Sat Apr 24 12:27:40 EEST 2010, Juergen Daubert wrote:
> 
>> On Mon, Mar 29, 2010 at 02:14:28PM +0200, Juergen Daubert wrote:
>>> Hi,
>>> 
>>> got the following with beta4 while uploading messages from a local 
>>> mbox to the dovecot server in my LAN, tested with mutt and sylpheed, 
>>> the same action works with 1.2.11: 
>>> 
>>> 
>>> Mar 29 13:42:46 [dovecot] imap(juergen): Panic: stream doesn't support
>>> seeking backwards
>> 
>> FYI, got the same crash with a build from nightly 20100422. If you 
>> need further informations, please let me know.
> 
> 
> I have started seeing apparently the same crash. I have a new android
> phone with K-9 imap client and I see this error in the log every time
> the phone polls the server.
> 
> I upgraded to 2.0.beta5 yesterday and the crash is still happening.
> 
> The phone logs an error "readQuotedString(): end of stream reached", but
> otherwise seems OK. I suspect this is a bug in the K-9, but it would be
> nice if dovecot didn't crash.


I am aware of <http://hg.dovecot.org/dovecot-2.0/rev/6e32dbc4cd8f> which
is presumably the reason for the Panic.

What I don't understand is whether this is strictly the client's
problem, or if there is some issue in Dovecot as well. If there is a
Dovecot issue, I can try to collect and report more information about
these Panics if that would be helpful.

On the other hand, if the comment:

  file istream: If trying to seek backwards in unseekable stream, panic.
  The previous way of just setting an error flag was getting ignored too
  easily and causing silent corruption in such situations.

means getting ignored by buggy clients, and this is just Dovecot trying
to cope with buggy clients as best as it can, then I can accept that,
but it would be helpful to me to understand that that is the case.

I would appreciate knowing just what the situation is with these Panics.

-- 
Mark Sapiro <mark at msapiro.net>        The highway is for gamblers,
San Francisco Bay Area, California    better use your sense - B. Dylan