Authentication/Penalty disabled (socket mode=0) introduces constant 5 sec delays (2.27 on debian 9)

Thu Dec 20 19:09:54 EET 2018

Hi,

I hit a bizare problem with dovecot 2.2.7 on debian 9 with LMTP enabled and auth/penalty disabled as documented here :
  https://wiki.dovecot.org/Authentication/Penalty

Use case : I run a swaks command to send an email to an exim4 that tries to make a callout to dovecot-lmtp.
At RCPT TO: swaks hangs 5.0<something-small> seconds then process normally (exim is waiting for callout completion).

with strace, I see 5 second delay with many tries to socket connection.

(PID 9652 was an auth process freshly forked)

[pid  9652] socket(AF_UNIX, SOCK_STREAM, 0) = 14
[pid  9652] fcntl(14, F_GETFL)          = 0x2 (flags O_RDWR)
[pid  9652] fcntl(14, F_SETFL, O_RDWR|O_NONBLOCK) = 0
[pid  9652] connect(14, {sa_family=AF_UNIX, sun_path="anvil-auth-penalty"}, 110) = -1 ECONNREFUSED (Connection refused)
[pid  9652] close(14)                   = 0
[pid  9652] nanosleep({tv_sec=0, tv_nsec=20000000}, NULL) = 0
[pid  9652] socket(AF_UNIX, SOCK_STREAM, 0) = 14
[pid  9652] fcntl(14, F_GETFL)          = 0x2 (flags O_RDWR)
[pid  9652] fcntl(14, F_SETFL, O_RDWR|O_NONBLOCK) = 0
[pid  9652] connect(14, {sa_family=AF_UNIX, sun_path="anvil-auth-penalty"}, 110) = -1 ECONNREFUSED (Connection refused)
[pid  9652] close(14)                   = 0
[pid  9652] nanosleep({tv_sec=0, tv_nsec=50000000}, NULL) = 0
[pid  9652] socket(AF_UNIX, SOCK_STREAM, 0) = 14
[pid  9652] fcntl(14, F_GETFL)          = 0x2 (flags O_RDWR)
[pid  9652] fcntl(14, F_SETFL, O_RDWR|O_NONBLOCK) = 0
[pid  9652] connect(14, {sa_family=AF_UNIX, sun_path="anvil-auth-penalty"}, 110) = -1 ECONNREFUSED (Connection refused)
[pid  9652] close(14)                   = 0
[pid  9652] nanosleep({tv_sec=0, tv_nsec=90000000}, NULL) = 0

with ddd I get to:
src/lib-master/anvil-client.c: int anvil_client_connect(struct anvil_client *client, bool retry) {
//[...]
fd = retry ? net_connect_unix_with_retries(client->path, 5000) : net_connect_unix(client->path);
//[...]

and retry is forced to TRUE by the caller and net_connect_unix_with_retries retries in case of ECONNREFUSED.

How I get into it :

ssh -X root at telegraphe-test

apt install dovecot-dbg
cd /dev/shm
apt source dovecot
cd dovecot-2.2.27
pidof dovecot
ddd /usr/sbin/dovecot
set follow-fork-mode child
attach 11833
cont

# Send an e-mail from swaks to exim that use transport=smtp in LMTP mode to dovecot-lmtp, press interrupt while exim is blocking after RCPT TO:

(gdb) bt
#0  0x00007f81528af270 in __nanosleep_nocancel () at ../sysdeps/unix/syscall-template.S:84
#1  0x00007f81528d8b84 in usleep (useconds=<optimized out>) at ../sysdeps/posix/usleep.c:32
#2  0x00007f815329368e in net_connect_unix_with_retries (path=0x562dc200ce10 <error: Cannot access memory at address 0x562dc200ce10>, msecs=msecs at entry=5000) at net.c:347
#3  0x00007f815320ce0d in anvil_client_connect (client=0x562dc200cda0, retry=retry at entry=true) at anvil-client.c:136
#4  0x0000562dc1429f5d in auth_penalty_init (path=0x562dc1451846 <error: Cannot access memory at address 0x562dc1451846>) at auth-penalty.c:37
#5  0x0000562dc1424166 in main_preinit () at main.c:202
#6  main (argc=<optimized out>, argv=<optimized out>) at main.c:396

(gdb) bt full
#1  0x00007f81528d8b84 in usleep (useconds=<optimized out>) at ../sysdeps/posix/usleep.c:32
         ts = {tv_sec = 0, tv_nsec = 80000000}
#2  0x00007f815329368e in net_connect_unix_with_retries (path=0x562dc200ce10 <error: Cannot access memory at address 0x562dc200ce10>, msecs=msecs at entry=5000) at net.c:347
         start = {tv_sec = 1545319486, tv_usec = 241864}
         now = {tv_sec = 1545319490, tv_usec = 198061}
         fd = -1
#3  0x00007f815320ce0d in anvil_client_connect (client=0x562dc200cda0, retry=retry at entry=true) at anvil-client.c:136
         fd = <optimized out>
         __FUNCTION__ = <error reading variable __FUNCTION__ (Cannot access memory at address 0x7f81532a8260)>
#4  0x0000562dc1429f5d in auth_penalty_init (path=0x562dc1451846 <error: Cannot access memory at address 0x562dc1451846>) at auth-penalty.c:37
No locals.
#5  0x0000562dc1424166 in main_preinit () at main.c:202
         mod_set = <error reading variable mod_set (Cannot access memory at address 0x7ffda885db80)>
#6  main (argc=<optimized out>, argv=<optimized out>) at main.c:396
         c = <optimized out>
Backtrace stopped: Cannot access memory at address 0x7ffda885dbf8
(gdb)

Code I've read :

src/auth/main.c: static void main_preinit(void)

         if (!worker)
                 auth_penalty = auth_penalty_init(AUTH_PENALTY_ANVIL_PATH);
         auth_request_stats_init();

src/auth/auth-penalty.c: struct auth_penalty *auth_penalty_init(const char *path)

         if (anvil_client_connect(penalty->client, TRUE) < 0)
                 penalty->disabled = TRUE;
         else {

src/lib-master/anvil-client.c: int anvil_client_connect(struct anvil_client *client, bool retry)

         fd = retry ? net_connect_unix_with_retries(client->path, 5000) :
                 net_connect_unix(client->path);

src/lib/net.c : int net_connect_unix_with_retries(const char *path, unsigned int msecs) {
         struct timeval start, now;
         int fd;

         if (gettimeofday(&start, NULL) < 0)
                 i_panic("gettimeofday() failed: %m");

         do {
                 fd = net_connect_unix(path);
                 if (fd != -1 || (errno != EAGAIN && errno != ECONNREFUSED))  // <------------------ HERE, I go into ECONNREFUSED case during 5 seconds
                         break;

                 /* busy. wait for a while. */
                 usleep(((rand() % 10) + 1) * 10000);
                 if (gettimeofday(&now, NULL) < 0)
                         i_panic("gettimeofday() failed: %m");
         } while (timeval_diff_msecs(&now, &start) < (int)msecs);
         return fd;
}

Additionnal environment infos (mailboxes are NFS-backed) :

lsb_release -a
No LSB modules are available.
Distributor ID:	Debian
Description:	Debian GNU/Linux 9.2 (stretch)
Release:	9.2
Codename:	stretch

mount | grep ^/
/dev/sda1 on / type ext4 (rw,relatime,errors=remount-ro,data=ordered)

mount | grep nfs
nfs1:/mail/maildir on /var/maildir type nfs (rw,relatime,vers=3,rsize=65536,wsize=65536,namlen=255,hard,proto=tcp,timeo=600,retrans=2,sec=sys,mountaddr=172.16.2.28,mountvers=3,mountport=635,mountproto=udp,local_lock=none,addr=172.16.2.28)
nfs1:/mail on /var/mail type nfs (rw,relatime,vers=3,rsize=65536,wsize=65536,namlen=255,hard,proto=tcp,timeo=600,retrans=2,sec=sys,mountaddr=172.16.2.28,mountvers=3,mountport=635,mountproto=udp,local_lock=none,addr=172.16.2.28)
cifs1:/homepermanents/info/lpouzenc on /home/lpouzenc type nfs (rw,nosuid,nodev,relatime,vers=3,rsize=65536,wsize=65536,namlen=255,hard,proto=tcp,timeo=600,retrans=2,sec=sys,mountaddr=172.16.2.29,mountvers=3,mountport=635,mountproto=udp,local_lock=none,addr=172.16.2.29)

telegraphe-test:~# apt-cache policy dovecot-core
dovecot-core:
   Installé : 1:2.2.27-3+deb9u2
   Candidat : 1:2.2.27-3+deb9u2
  Table de version :
  *** 1:2.2.27-3+deb9u2 500
         500 http://miroir/debian stretch/main amd64 Packages
         500 http://security.debian.org/debian-security stretch/updates/main amd64 Packages
         100 /var/lib/dpkg/status

telegraphe-test:~# dovecot -n
# 2.2.27 (c0f36b0): /etc/dovecot/dovecot.conf
# Pigeonhole version 0.4.16 (fed8554)
doveconf: Warning: service auth { client_limit=10000 } is lower than required under max. load (10240)
# OS: Linux 4.9.0-4-amd64 x86_64 Debian 9.2 nfs
auth_verbose = yes
default_client_limit = 10000
default_process_limit = 2048
lda_mailbox_autocreate = yes
lda_mailbox_autosubscribe = yes
mail_debug = yes
mail_fsync = always
mail_location = maildir:/var/mail/maildir/%u
managesieve_notify_capability = mailto
managesieve_sieve_capability = fileinto reject envelope encoded-character vacation subaddress comparator-i;ascii-numeric relational regex imap4flags copy include variables body enotify environment mailbox date index ihave duplicate mime foreverypart extracttext
mmap_disable = yes
namespace inbox {
   inbox = yes
   location =
   mailbox Drafts {
     special_use = \Drafts
   }
   mailbox Junk {
     special_use = \Junk
   }
   mailbox Sent {
     special_use = \Sent
   }
   mailbox "Sent Messages" {
     special_use = \Sent
   }
   mailbox Trash {
     special_use = \Trash
   }
   prefix =
   separator = /
}
passdb {
   driver = pam
}
plugin {
   sieve = file:/var/mail/mailconf/%1u/%u/sieve;active=/var/mail/mailconf/%1u/%u/.dovecot.sieve
   sieve_before = /var/mail/mailconf/global/sieve/before.d
   sieve_global = /var/mail/mailconf/global/sieve
   sieve_vacation_dont_check_recipient = yes
}
protocols = " imap lmtp sieve sieve"
service anvil {
   unix_listener anvil-auth-penalty {
     mode = 00
   }
}
service lmtp {
   inet_listener lmtp {
     port = 24
   }
}
service managesieve {
   process_limit = 16
}
ssl_cert = </etc/ssl/certs/telegraphe7_cert.pem
ssl_key =  # hidden, use -P to show it
syslog_facility = local0
userdb {
   driver = passwd
}
verbose_proctitle = yes
protocol lmtp {
   auth_username_format = %n
   mail_plugins = " sieve"
}
protocol imap {
   mail_max_userip_connections = 20
}

Could you see a config tuning that keeps auth-penalty out of the way (it seems to behaves badly here, because we have perdition IMAP proxy in front, and it keeps track only of his IP and adds 2/4/8/15s delays to "random" legit clients.

Could it be saved with a dedicated config entry to disable auth-penalty ?

Is there solution to have auth-penalty working while having perdition IMAP proxy ?

Regards,
Ludovic Pouzenc

-- 
Ludovic POUZENC - Ingénieur Système
IMT Mines Albi  (http://www.imt-mines-albi.fr)
81013 ALBI CT Cedex 09 - Tel : 05 63 49 33 56

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