Too many references: cannot splice

[Luis Ugalde]

Sebastian,

On October 13th I sent a new email with subject "Too many references:
cannot splice" with a reference to a lklm post.

You will find more info. and a patch there. I can confirm the patch is
working for us.

Regards,
Luis Ugalde

On Fri, Dec 2, 2016 at 5:23 PM, Sebastian Köhler <sk at tyrion.de> wrote:

> Hello,
>
> multiple times per day one of our Dovecot servers has the problem that it
> suddenly refuses to accept new connections and then floods the logs with
> these messages:
>
> Dec  2 12:43:06 alfa3201 dovecot: pop3-login: Error: fd_send(pop3, 18)
> failed: Too many references: cannot splice
> Dec  2 12:43:07 alfa3201 dovecot: pop3-login: Error: fd_send(pop3, 18)
> failed: Too many references: cannot splice
> Dec  2 12:43:07 alfa3201 dovecot: imap-login: Error: fd_send(imap, 16)
> failed: Too many references: cannot splice
> Dec  2 12:43:07 alfa3201 dovecot: imap-login: Error: fd_send(imap, 16)
> failed: Too many references: cannot splice
>
>
> We have to either do a restart of the server or a doveadm kick on all
> users to make it reachable again. On my search for a solution I found a
> similar report from March[1] however without a fix.
>
>
> [1] http://dovecot.org/pipermail/dovecot/2016-March/103514.html
>
>
> dovecot -n
>
> # 2.2.24 (a82c823): /etc/dovecot/dovecot.conf
> # Pigeonhole version 0.4.13 (7b14904)
> # OS: Linux 4.4.17-040417-generic x86_64 Debian 8.6
> auth_mechanisms = plain login
> debug_log_path = /var/log/dovecot-debug.log
> default_client_limit = 8003
> default_process_limit = 2000
> default_vsz_limit = 512 M
> disable_plaintext_auth = no
> listen = *
> login_greeting = [CENSORED] - ready.
> mail_location = maildir:~/Maildir:CONTROL=/opt/dovecot/control/%n-
> control:INDEX=/opt/dovecot/index/%n
> mail_plugins = " stats quota"
> namespace inbox {
>   inbox = yes
>   location =
>   mailbox Drafts {
>     auto = subscribe
>     special_use = \Drafts
>   }
>   mailbox Spam {
>     auto = subscribe
>     special_use = \Junk
>   }
>   mailbox Sent {
>     auto = subscribe
>     special_use = \Sent
>   }
>   mailbox "Sent Messages" {
>     special_use = \Sent
>   }
>   mailbox Trash {
>     auto = subscribe
>     special_use = \Trash
>   }
>   prefix = INBOX.
>   separator = .
> }
> passdb {
>   args = dovecot-%s
>   driver = pam
> }
> plugin {
>   quota = fs:%n(soft quota)
>   sieve = ~/.dovecot.sieve
>   sieve_dir = ~/sieve
>   stats_command_min_time = 1 mins
>   stats_domain_min_time = 12 hours
>   stats_ip_min_time = 12 hours
>   stats_memory_limit = 16 M
>   stats_refresh = 30 secs
>   stats_session_min_time = 15 mins
>   stats_track_cmds = no
>   stats_user_min_time = 24 hours
> }
> protocols = " imap pop3"
> service auth {
>   unix_listener /var/spool/postfix/private/auth {
>     group = postfix
>     mode = 0666
>     user = postfix
>   }
> }
> service imap-login {
>   inet_listener imaps {
>     ssl = yes
>   }
> }
> service imap-postlogin {
>   executable = script-login /etc/dovecot/post-login/expire.sh
> }
> service imap {
>   executable = imap imap-postlogin
> }
> service pop3-login {
>   inet_listener pop3 {
>     port = 110
>   }
>   inet_listener pop3s {
>     port = 995
>     ssl = yes
>   }
> }
> service pop3-postlogin {
>   executable = script-login /etc/dovecot/post-login/expire.sh
> }
> service pop3 {
>   executable = pop3 pop3-postlogin
> }
> service quota-status {
>   executable = quota-status -p postfix
>   unix_listener /var/spool/postfix/private/quota {
>     group = postfix
>     mode = 0660
>     user = postfix
>   }
> }
> service stats {
>   fifo_listener stats-mail {
>     mode = 0666
>     user = dovecot
>   }
> }
> ssl_ca = </etc/ssl.crt/ca-admin.crt
> ssl_cert = </etc/ssl.crt/admin.crt
> ssl_key = </etc/ssl.key/admin.key
> ssl_protocols = !SSLv2 !SSLv3
> userdb {
>   driver = passwd
> }
> protocol imap {
>   imap_capability = +XLIST +NAMESPACE METADATA QUOTA
>   imap_idle_notify_interval = 1 mins
>   mail_max_userip_connections = 500
>   mail_plugins = " stats quota imap_quota imap_stats"
> }
> protocol pop3 {
>   mail_max_userip_connections = 500
>   mail_plugins = " stats quota"
>   pop3_client_workarounds = outlook-no-nuls oe-ns-eoh
> }
>