POP3 stops accepting connections?

Thu Apr 21 21:51:00 EDT 2005

Hi,

I've just installed Cyrus 2.2.12 as a mailbox solution, but an having a small problem with POP3 - it seems to stop processing connections. For example - I've just done a whole load of consecutive send and recieves, which flew through. Then all of a sudden it stops, and connections can take anything up to a fair few minutes to get the POP3 banner. It's not a big deal at the moment, but I have no doubt users will start complaining soon!

I've tried the same thing with IMAP and don't seem to get the problem, it solely seems to be POP3 that is affected.

Has anyone come across this before? What can I do to diagnose the problem?

netstat shows the connection as being in the established state, but the session isn't actually set up. I had a quick tinker with the prefork values to see f that made any difference but as the connection was established I didn't think it would, and it didn't.

Restarting doesn't seem to immediately cure the problem, but a while after that it comes back to life, then after probably around 20 or so POP3 connections in rapid succession it fails again. I've taken a packet capture from when the fault occurs, but it doesn't reveal anything to me. I've chopped this to remove irrelevant traffic such as smtp, ssh and ntp.

02:33:53.661576 IP xxx-xxx-xxx-xxx.dsl.pipex.com.38281 > delilah.unifiedgroup.co.uk.pop3: S 1220713841:1220713841(0) win 65535 <mss 1402,nop,nop,sackOK>
02:33:53.661612 IP delilah.unifiedgroup.co.uk.pop3 > xxx-xxx-xxx-xxx.dsl.pipex.com.38281: S 265982648:265982648(0) ack 1220713842 win 5840 <mss 1460,nop,nop,sackOK>
02:33:53.697353 IP xxx-xxx-xxx-xxx.dsl.pipex.com.38281 > delilah.unifiedgroup.co.uk.pop3: . ack 1 win 65535
02:34:01.132917 IP samson.unifiedgroup.co.uk.microsoft-ds > delilah.unifiedgroup.co.uk.3087: . 1583174566:1583174567(1) ack 3877690427 win 65027
02:34:01.132979 IP delilah.unifiedgroup.co.uk.3087 > samson.unifiedgroup.co.uk.microsoft-ds: . ack 1 win 1728 <nop,nop,timestamp 46699679 1137810,nop,nop,sack sack 1 {0:1} >

02:35:43.855948 IP xxx-xxx-xxx-xxx.dsl.pipex.com.38285 > delilah.unifiedgroup.co.uk.imap2: S 1521578317:1521578317(0) win 65535 <mss 1402,nop,nop,sackOK>
02:35:43.856014 IP delilah.unifiedgroup.co.uk.imap2 > xxx-xxx-xxx-xxx.dsl.pipex.com.38285: S 379649352:379649352(0) ack 1521578318 win 5840 <mss 1460,nop,nop,sackOK>
02:35:43.891510 IP xxx-xxx-xxx-xxx.dsl.pipex.com.38285 > delilah.unifiedgroup.co.uk.imap2: . ack 1 win 65535
02:35:43.896521 IP delilah.unifiedgroup.co.uk.imap2 > xxx-xxx-xxx-xxx.dsl.pipex.com.38285: P 1:55(54) ack 1 win 5840
02:35:44.080735 IP xxx-xxx-xxx-xxx.dsl.pipex.com.38285 > delilah.unifiedgroup.co.uk.imap2: . ack 55 win 65481
02:35:48.136670 IP xxx-xxx-xxx-xxx.dsl.pipex.com.38285 > delilah.unifiedgroup.co.uk.imap2: F 1:1(0) ack 55 win 65481
02:35:48.136917 IP delilah.unifiedgroup.co.uk.imap2 > xxx-xxx-xxx-xxx.dsl.pipex.com.38285: . ack 2 win 5840
02:35:48.137353 IP delilah.unifiedgroup.co.uk.imap2 > xxx-xxx-xxx-xxx.dsl.pipex.com.38285: F 55:55(0) ack 2 win 5840
02:35:48.175638 IP xxx-xxx-xxx-xxx.dsl.pipex.com.38285 > delilah.unifiedgroup.co.uk.imap2: . ack 56 win 65481

02:35:52.661274 IP delilah.unifiedgroup.co.uk.pop3 > xxx-xxx-xxx-xxx.dsl.pipex.com.38278: P 56067399:56067483(84) ack 826240789 win 5840
02:35:52.662135 IP delilah.unifiedgroup.co.uk.pop3 > xxx-xxx-xxx-xxx.dsl.pipex.com.38278: F 84:84(0) ack 1 win 5840
02:35:52.662816 IP delilah.unifiedgroup.co.uk.pop3 > xxx-xxx-xxx-xxx.dsl.pipex.com.38277: P 53953223:53953307(84) ack 806390175 win 5840
02:35:52.663724 IP delilah.unifiedgroup.co.uk.pop3 > xxx-xxx-xxx-xxx.dsl.pipex.com.38277: F 84:84(0) ack 1 win 5840
02:35:52.664411 IP delilah.unifiedgroup.co.uk.pop3 > xxx-xxx-xxx-xxx.dsl.pipex.com.38276: P 44691622:44691706(84) ack 4084763733 win 5840
02:35:52.665310 IP delilah.unifiedgroup.co.uk.pop3 > xxx-xxx-xxx-xxx.dsl.pipex.com.38276: F 84:84(0) ack 1 win 5840
02:35:52.665561 IP delilah.unifiedgroup.co.uk.pop3 > xxx-xxx-xxx-xxx.dsl.pipex.com.38281: P 1:85(84) ack 1 win 5840
02:35:52.666043 IP delilah.unifiedgroup.co.uk.pop3 > xxx-xxx-xxx-xxx.dsl.pipex.com.38280: P 258057498:258057582(84) ack 3600355369 win 5840
02:35:52.666992 IP delilah.unifiedgroup.co.uk.pop3 > xxx-xxx-xxx-xxx.dsl.pipex.com.38280: F 84:84(0) ack 1 win 5840
02:35:52.699581 IP xxx-xxx-xxx-xxx.dsl.pipex.com.38278 > delilah.unifiedgroup.co.uk.pop3: R 826240789:826240789(0) win 0
02:35:52.708412 IP xxx-xxx-xxx-xxx.dsl.pipex.com.38277 > delilah.unifiedgroup.co.uk.pop3: R 806390175:806390175(0) win 0
02:35:52.714476 IP xxx-xxx-xxx-xxx.dsl.pipex.com.38276 > delilah.unifiedgroup.co.uk.pop3: R 4084763733:4084763733(0) win 0
02:35:52.726493 IP xxx-xxx-xxx-xxx.dsl.pipex.com.38280 > delilah.unifiedgroup.co.uk.pop3: R 3600355369:3600355369(0) win 0
02:35:52.939491 IP xxx-xxx-xxx-xxx.dsl.pipex.com.38281 > delilah.unifiedgroup.co.uk.pop3: . ack 85 win 65451

You can see in the middle there, I established an IMAP connection quickly, to prove that at the time POP3 was the only thing working - that the POP3 connection came back into play straight after is purely co-incidental as it doesn't usually. As you can see by the time stamp, that POP3 session took 2 minutes to establish. The default for Outlook is to warn that there is a server problem after 60 seconds of attempting to connect, so I'm expecting lots of complaints!

cyrus.conf:

START {
  recover	cmd="ctl_cyrusdb -r"
}

SERVICES {
  imap		cmd="imapd" listen="imap2" prefork=5
  pop3		cmd="pop3d" listen="pop-3" prefork=15
  imaps		cmd="imapd -s" listen="imaps" prefork=0
  pop3s		cmd="pop3d -s" listen="pop3s" prefork=0
  sieve		cmd="timsieved" listen="sieve" prefork=0
  #lmtp		cmd="lmtpd" listen="lmtp" prefork=0
  lmtpunix	cmd="lmtpd" listen="/var/imap/socket/lmtp" prefork=0
  #notify	cmd="notifyd" listen="/var/imap/socket/notify" proto="udp" prefork=1
}

EVENTS {
  checkpoint	cmd="ctl_cyrusdb -c" period=30
  delprune	cmd="ctl_deliver -E 3" period=1440
  tlsprune	cmd="tls_prune" period=1440
}
imapd.conf:

configdirectory:	                /var/imap
partition-default:	                /var/spool/imap
sievedir:		                /var/imap/sieve

tls_ca_path:                              /etc/ssl/certs
tls_cert_file:		/etc/ssl/cyrus/server.crt
tls_key_file:		/etc/ssl/cyrus/server.key

admins:			root

hashimapspool:		yes
allowanonymouslogin:	no
allowplaintext:		yes
lmtp_downcase_rcpt:	yes

sasl_pwcheck_method:	saslauthd
sasl_mech_list:                          LOGIN

The authentication is passed off to Active Directory via PAM hence the use of saslauthd and the use of the login mechanism.

Any help with this would be gratefully recieved!

Regards,

Scott

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