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Dan Christensen

2009-Oct-08 00:55 UTC

[Dovecot] very frequent disconnections

I've installed dovecot 1:1.1.11-0ubuntu4.1 on my jaunty system.
Access from the same host works well, but when I access remotely
(from various MUAs and networks) I get *very* frequent disconnects.
Authentication is fine, and I can usually open a mail folder,
but larger operations such as copying 20 messages into an imap
folder always get disconnected.

I can reconnect, but I often get disconnected again in a few seconds,
especially if I do more than very light access.

I've enabled all the logging I'm aware of, but I don't see any
explanations.  I get things like

Oct  7 20:19:38 jdc dovecot: auth(default): new auth connection: pid=390
Oct  7 20:19:39 jdc dovecot: auth(default): client in:
AUTH^I1^IPLAIN^Iservice=imap^Isecured^Ilip=129.100.75.85^Irip=65.95.132.250^Ilport=143^Irport=62044^Iresp=<hidden>
Oct  7 20:19:39 jdc dovecot: auth-worker(default): pam(jdc,65.95.132.250):
lookup service=dovecot
Oct  7 20:19:39 jdc dovecot: auth-worker(default): pam(jdc,65.95.132.250): #1/1
style=1 msg=Password:
Oct  7 20:19:39 jdc dovecot: auth(default): client out: OK^I1^Iuser=jdc
Oct  7 20:19:39 jdc dovecot: auth(default): master in: REQUEST^I2^I367^I1
Oct  7 20:19:39 jdc dovecot: auth(default): passwd(jdc,65.95.132.250): lookup
Oct  7 20:19:39 jdc dovecot: auth(default): master out:
USER^I2^Ijdc^Isystem_user=jdc^Iuid=1000^Igid=1000^Ihome=/home/jdc
Oct  7 20:19:39 jdc dovecot: IMAP(jdc): Effective uid=1000, gid=1000,
home=/home/jdc
Oct  7 20:19:39 jdc dovecot: IMAP(jdc): maildir: data=~/Maildir
Oct  7 20:19:39 jdc dovecot: IMAP(jdc): maildir++: root=/home/jdc/Maildir,
index=, control=, inbox=/home/jdc/Maildir
Oct  7 20:19:40 jdc dovecot: IMAP(jdc): Connection closed bytes=303/1423

and

Oct  7 20:43:54 jdc dovecot: auth(default): new auth connection: pid=6620
Oct  7 20:43:55 jdc dovecot: auth(default): client in:
AUTH^I1^IPLAIN^Iservice=imap^Isecured^Ilip=129.100.75.85^Irip=65.95.132.250^Ilport=143^Irport=62633^Iresp=<hidden>
Oct  7 20:43:55 jdc dovecot: auth-worker(default): pam(jdc,65.95.132.250):
lookup service=dovecot
Oct  7 20:43:55 jdc dovecot: auth-worker(default): pam(jdc,65.95.132.250): #1/1
style=1 msg=Password:
Oct  7 20:43:55 jdc dovecot: auth(default): client out: OK^I1^Iuser=jdc
Oct  7 20:43:55 jdc dovecot: auth(default): master in: REQUEST^I5^I6594^I1
Oct  7 20:43:55 jdc dovecot: auth(default): passwd(jdc,65.95.132.250): lookup
Oct  7 20:43:55 jdc dovecot: auth(default): master out:
USER^I5^Ijdc^Isystem_user=jdc^Iuid=1000^Igid=1000^Ihome=/home/jdc
Oct  7 20:43:55 jdc dovecot: imap-login: Login: user=<jdc>, method=PLAIN,
rip=65.95.132.250, lip=129.100.75.85, TLS
Oct  7 20:43:55 jdc dovecot: IMAP(jdc): Effective uid=1000, gid=1000,
home=/home/jdc
Oct  7 20:43:55 jdc dovecot: IMAP(jdc): maildir: data=~/Maildir
Oct  7 20:43:55 jdc dovecot: IMAP(jdc): maildir++: root=/home/jdc/Maildir,
index=, control=, inbox=/home/jdc/Maildir
Oct  7 20:44:00 jdc dovecot: IMAP(jdc): Disconnected in APPEND bytes=1081/1965

The output of dovecot -n is:

# 1.1.11: /etc/dovecot/dovecot.conf
# OS: Linux 2.6.28-15-generic x86_64 Ubuntu 9.04 
log_timestamp: %Y-%m-%d %H:%M:%S 
ssl_cert_file: /etc/ssl/certs/dovecot.pem
ssl_key_file: /etc/ssl/private/dovecot.pem
verbose_ssl: yes
login_dir: /var/run/dovecot/login
login_executable: /usr/lib/dovecot/imap-login
login_greeting_capability: yes
max_mail_processes: 25
mail_max_userip_connections: 20
mail_privileged_group: mail
mail_location: maildir:~/Maildir
mail_debug: yes
maildir_copy_preserve_filename: yes
auth default:
  verbose: yes
  debug: yes
  passdb:
    driver: pam
  userdb:
    driver: passwd

The clients I have tried are Gnus (with starttls and gnutls-cli) and
evolution, on a jaunty system;  and k9mail-beta on an HTC Dream cell
phone.  All four configurations show similar connection issues, and
the jaunty client system has a solid DSL connection to the server.
The clients don't have informative error messages either.  To them it
just appears that the connection was closed.

Any idea what could be causing this?  Or how to debug it?

Thanks,

Dan

-- 
Dan Christensen
jdc at uwo.ca

Dan Christensen

2009-Oct-08 17:22 UTC

head link

[Dovecot] very frequent disconnections

Dan Christensen <jdc at uwo.ca> writes:
> I've installed dovecot 1:1.1.11-0ubuntu4.1 on my jaunty system.
> Access from the same host works well, but when I access remotely
> (from various MUAs and networks) I get *very* frequent disconnects.
> Authentication is fine, and I can usually open a mail folder,
> but larger operations such as copying 20 messages into an imap
> folder always get disconnected.
...> The clients I have tried are Gnus (with starttls and gnutls-cli) and
> evolution, on a jaunty system;  and k9mail-beta on an HTC Dream cell
> phone.  All four configurations show similar connection issues, and
> the jaunty client system has a solid DSL connection to the server.
If I configure dovecot to listen on a different port, I don't have these
troubles.  So I suspect some network throttling of imap data somewhere.
My contact at the university doesn't think this happens, and I'd be
surprised if my ISP does this, but I can't think of any other
explanation.

Dan

Timo Sirainen

2009-Oct-08 17:36 UTC

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[Dovecot] very frequent disconnections

On Wed, 2009-10-07 at 20:55 -0400, Dan Christensen
wrote:> Oct  7 20:19:40 jdc dovecot: IMAP(jdc): Connection closed bytes=303/1423
> Oct  7 20:44:00 jdc dovecot: IMAP(jdc): Disconnected in APPEND
bytes=1081/1965
The connection just got closed from Dovecot's point of view.

Have you tried without SSL?

Anyway I can't think of anything besides some weird network issue or
maybe some firewall/antivirus in the middle.

Some clients also support "imap over ssh", you could try that.
Basically
use "ssh server dovecot --exec-mail imap" as the command.

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Dan Christensen

2009-Oct-09 20:09 UTC

head link

[Dovecot] very frequent disconnections

Timo Sirainen <tss at iki.fi> writes:
> On Wed, 2009-10-07 at 20:55 -0400, Dan Christensen wrote:
>> Oct  7 20:19:40 jdc dovecot: IMAP(jdc): Connection closed
bytes=303/1423
>> Oct  7 20:44:00 jdc dovecot: IMAP(jdc): Disconnected in APPEND
bytes=1081/1965
>
> The connection just got closed from Dovecot's point of view.
>
> Have you tried without SSL?
The very frequent dropped connections don't happen if I don't use TLS.
To summarize:

- they happen with TLS to port 143
- they don't happen with a plain connection to port 143
- they don't happen with a TLS connection to port 11143
- they don't happen if I connect using
    ssh jdc.math.uwo.ca dovecot --exec-mail imap

Very strange.  I can trigger the drop 100% of the time by copying 20 or
30 messages from a local folder to a remote imap folder.
> Anyway I can't think of anything besides some weird network issue or
> maybe some firewall/antivirus in the middle.
Could be.  But now it's clear that it's not affecting all traffic
to port 143, only tls traffic.  Weird.
> Some clients also support "imap over ssh", you could try that.
Basically
> use "ssh server dovecot --exec-mail imap" as the command.
That works well and is also quite fast to connect, so I'll probably
stick with it.

Thanks for the help,

Dan

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