<div dir="ltr"><div>I'm encountering connection issues to Dovecot when reuse_port is activated. Some of the connections work fine, but about every 3rd of them does not receive the banner after the TCP connection has established:</div><div><br></div># nc -v 10.6.7.133 143<br>Connection to 10.6.7.133 143 port [tcp/imap2] succeeded!<br>* OK [CAPABILITY IMAP4rev1 LITERAL+ SASL-IR LOGIN-REFERRALS ID ENABLE IDLE STARTTLS AUTH=PLAIN AUTH=LOGIN] Hello.<br><div>^C</div><div><br></div><div>
# nc -v 10.6.7.133 143<br>Connection to 10.6.7.133 143 port [tcp/imap2] succeeded!<br>* OK [CAPABILITY IMAP4rev1 LITERAL+ SASL-IR LOGIN-REFERRALS ID ENABLE IDLE STARTTLS AUTH=PLAIN AUTH=LOGIN] Hello.<br><div>^C</div><div><br></div>
</div><div></div><div># nc -v 10.6.7.133 143<br>Connection to 10.6.7.133 143 port [tcp/imap2] succeeded!<br>^C<br></div><div><br></div><div>The relevant processes listening on this port:<br></div><div><br></div><div># netstat -nap|grep 143<br>tcp 0 0 <a href="http://0.0.0.0:143">0.0.0.0:143</a> 0.0.0.0:* LISTEN 15110/dovecot/imap-<br>tcp 0 0 <a href="http://0.0.0.0:143">0.0.0.0:143</a> 0.0.0.0:* LISTEN 15103/dovecot/imap-<br>tcp 5 0 <a href="http://0.0.0.0:143">0.0.0.0:143</a> 0.0.0.0:* LISTEN 15100/dovecot</div><div><br></div><div>After removing the reuse_port = yes configuration directive there is only one single process listening (and the service is running without any issues):<br></div><div><br></div><div># netstat -nap|grep 143<br>tcp 0 0 <a href="http://0.0.0.0:143">0.0.0.0:143</a> 0.0.0.0:* LISTEN 15292/dovecot</div><div><br></div><div>The test config was Linux 4.9.0-4-amd64 on debian-stretch and dovecot-2.2.36.4 (compiled by me) running on a VM with 1 CPU core. If that matters, dovecot was started in a docker container but using the hosts's network namespace.<br></div><div><br></div><div>What am I missing? <br></div><div><br></div><div>Thanks,</div><div>Imre<br></div><div><br></div></div>