dovecot - Oct 2007 - Sometimes Dovecot v1.0.3 does not accept new connections

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Hello,

occasionally Dovecot stops to accept new connections. Already existing 
ones do function properly. Strace'ing dovecot-auth reveals that it is 
running and is authentificating users, the logfile logs new connections. 
However, lots of other connects just stall, before the IMAP server 
responds with the greeting.

My user backend is a LDAP server.

I've sniffed the interface, but I also don't see numerous connection 
attempts, so I suppose, that there is no DoS attack running.

The logfile contains no warning or error except:
dovecot: Oct 17 15:34:44 Warning: auth(default): Growing pool 
'plain_auth_request' with: 2048
dovecot: Oct 17 15:34:49 Warning: auth(default): Growing pool 
'plain_auth_request' with: 2048
dovecot: Oct 17 15:34:52 Warning: auth(default): Growing pool 
'plain_auth_request' with: 2048
dovecot: Oct 17 15:35:02 Warning: auth(default): Growing pool 
'plain_auth_request' with: 2048
dovecot: Oct 17 15:35:05 Warning: auth(default): Growing pool 
'plain_auth_request' with: 2048
dovecot: Oct 17 15:35:12 Warning: auth(default): Growing pool 
'plain_auth_request' with: 2048
dovecot: Oct 17 15:35:19 Warning: auth(default): Growing pool 
'plain_auth_request' with: 2048
dovecot: Oct 17 15:35:20 Warning: auth(default): Growing pool 
'plain_auth_request' with: 2048
dovecot: Oct 17 15:35:25 Warning: auth(default): Growing pool 
'plain_auth_request' with: 2048
dovecot: Oct 17 15:35:26 Warning: auth(default): Growing pool 
'plain_auth_request' with: 2048
dovecot: Oct 17 15:35:27 Warning: auth(default): Growing pool 
'plain_auth_request' with: 2048
dovecot: Oct 17 15:35:27 Warning: auth(default): Growing pool 
'plain_auth_request' with: 2048
dovecot: Oct 17 15:35:41 Warning: auth(default): Growing pool 
'plain_auth_request' with: 2048
dovecot: Oct 17 15:35:42 Warning: auth(default): Growing pool 
'plain_auth_request' with: 2048
dovecot: Oct 17 15:35:47 Warning: auth(default): Growing pool 
'plain_auth_request' with: 2048
dovecot: Oct 17 15:35:49 Warning: auth(default): Growing pool 
'plain_auth_request' with: 2048
dovecot: Oct 17 15:35:49 Warning: auth(default): Growing pool 
'plain_auth_request' with: 2048
dovecot: Oct 17 15:35:50 Warning: auth(default): Growing pool 
'plain_auth_request' with: 2048
dovecot: Oct 17 15:35:56 Warning: auth(default): Growing pool 
'plain_auth_request' with: 2048
dovecot: Oct 17 15:36:03 Warning: auth(default): Growing pool 
'plain_auth_request' with: 2048

Does somebody has an idea, where to go to look into the issue?

Bye,

- -- 
Steffen Kaiser
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On Wed, 2007-10-17 at 16:12 +0200, Steffen Kaiser wrote:
> occasionally Dovecot stops to accept new connections. Already existing 
> ones do function properly. Strace'ing dovecot-auth reveals that it is 
> running and is authentificating users, the logfile logs new connections. 
> However, lots of other connects just stall, before the IMAP server 
> responds with the greeting.
Do you have login_greeting_capability=yes?

Maybe these patches help figuring out what hangs:
http://hg.dovecot.org/dovecot-1.0/rev/4bdab7e04a61
http://hg.dovecot.org/dovecot-1.0/rev/4dab9295cd95
http://hg.dovecot.org/dovecot-1.0/rev/9c74f599bb2f

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On Sat, 27 Oct 2007, Timo Sirainen wrote:
> Do you have login_greeting_capability=yes?
No, I don't.
> Maybe these patches help figuring out what hangs:
OK, I'll try

$ dovecot -n
# 1.0.3: /usr/local/dovecot-1.0.3/etc/dovecot.conf
base_dir: /var/run/dovecot/
log_path: /var/log/dovecot/dovecot.log
protocols: imap imaps pop3 pop3s managesieve
listen(default): *
listen(imap): *
listen(pop3): *
listen(managesieve): *:2000
ssl_ca_file: /etc/ssl/certs/ca.crt
ssl_cert_file(default): /etc/ssl/certs/imap.pem
ssl_cert_file(imap): /etc/ssl/certs/imap.pem
ssl_cert_file(pop3): /etc/ssl/certs/pop3.pem
ssl_cert_file(managesieve): /etc/ssl/certs/imap.pem
ssl_key_file(default): /etc/ssl/private/imap.key
ssl_key_file(imap): /etc/ssl/private/imap.key
ssl_key_file(pop3): /etc/ssl/private/pop3.key
ssl_key_file(managesieve): /etc/ssl/private/imap.key
disable_plaintext_auth: no
verbose_ssl: yes
login_dir(default): /var/run/dovecot//login
login_dir(imap): /var/run/dovecot//login
login_dir(pop3): /var/run/dovecot//login
login_dir(managesieve): /var/run/dovecot/login
login_executable(default): 
/usr/local/dovecot-1.0.3/libexec/dovecot/imap-login
login_executable(imap): 
/usr/local/dovecot-1.0.3/libexec/dovecot/imap-login
login_executable(pop3): 
/usr/local/dovecot-1.0.3/libexec/dovecot/pop3-login
login_executable(managesieve): 
/usr/local/dovecot-1.0.3/libexec/dovecot/managesieve-login
login_log_format_elements: %p: user=<%u> method=%m rip=%r lip=%l %c
verbose_proctitle: yes
first_valid_uid: 10
mail_location(default): 
maildir:%h/Maildir:CONTROL=/var/cache/dovecot/%i/control:INDEX=/var/cache/dovecot/%i/index
mail_location(imap): 
maildir:%h/Maildir:CONTROL=/var/cache/dovecot/%i/control:INDEX=/var/cache/dovecot/%i/index
mail_location(pop3): 
maildir:%h/Maildir:CONTROL=/var/cache/dovecot/%i/control:INDEX=/var/cache/dovecot/%i/index
mail_location(managesieve): maildir:%h/Maildir
mail_debug: yes
dotlock_use_excl: yes
maildir_copy_with_hardlinks: yes
maildir_copy_preserve_filename: yes
umask: 7
mail_executable(default): /usr/local/dovecot-1.0.3/libexec/dovecot/rawlog 
/usr/local/dovecot-1.0.3/libexec/dovecot/imap
mail_executable(imap): /usr/local/dovecot-1.0.3/libexec/dovecot/rawlog 
/usr/local/dovecot-1.0.3/libexec/dovecot/imap
mail_executable(pop3): /usr/local/dovecot-1.0.3/libexec/dovecot/pop3
mail_executable(managesieve): 
/usr/local/dovecot-1.0.3/libexec/dovecot/managesieve
mail_plugins(default): quota imap_quota mail_log zlib
mail_plugins(imap): quota imap_quota mail_log zlib
mail_plugins(pop3): quota mail_log
mail_plugins(managesieve):
mail_plugin_dir(default): /usr/local/dovecot-1.0.3/lib/dovecot/imap
mail_plugin_dir(imap): /usr/local/dovecot-1.0.3/lib/dovecot/imap
mail_plugin_dir(pop3): /usr/local/dovecot-1.0.3/lib/dovecot/pop3
mail_plugin_dir(managesieve): 
/usr/local/dovecot-1.0.3/lib/dovecot/managesieve
mail_log_prefix: %Us(%u) [%p]:
mail_log_max_lines_per_sec: 0
pop3_uidl_format(default):
pop3_uidl_format(imap):
pop3_uidl_format(pop3): %08Xu%08Xv
pop3_uidl_format(managesieve):
pop3_client_workarounds(default):
pop3_client_workarounds(imap):
pop3_client_workarounds(pop3): oe-ns-eoh
pop3_client_workarounds(managesieve):
namespace:
   type: private
   separator: .
   inbox: yes
auth default:
   mechanisms: plain login
   cache_size: 10
   username_chars: 
abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ01234567890-
   verbose: yes
   debug: yes
   passdb:
     driver: ldap
     args: /usr/local/dovecot-1.0.3/etc/dovecot-ldap.conf
   passdb:
     driver: shadow
   userdb:
     driver: ldap
     args: /usr/local/dovecot-1.0.3/etc/dovecot-ldap.conf
   userdb:
     driver: passwd
   socket:
     type: listen
     master:
       path: /var/run/dovecot/auth-master
       mode: 432
       group: mail
plugin:
   quota: fs

- -- 
Steffen Kaiser
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