Dovecot Proxy LTMP client connect to TCP port 0

[Wido den Hollander]

I looked into the further and it seems that there is no default port for LMTP in
Dovecot.

I patched the code and this seems right:
https://github.com/wido/core/commit/a5917908850eb570ca441517e6bc33f6ce63ed7a

This will make the LMTP client connect to TCP port 24 if no port has been
provided.

I will submitted it as a Pull Request on Github:
https://github.com/dovecot/core/pull/6

Wido

> Op 9 april 2016 om 11:25 schreef Wido den Hollander <wido at widodh.nl>:
> 
> 
> Hi,
> 
> I am trying to set up a Dovecot proxy which proxies through POP3, IMAP and
> LTMP
> towards a different Dovecot machine.
> 
> On the proxy machine I use a MySQL database as a userdb and passwdb backend
> and
> it returns the proper information as described here:
> http://wiki2.dovecot.org/PasswordDatabase/ExtraFields/Proxy
> 
> IMAP and POP3 works just fine, but with LMTP I run into a problem.
> 
> On the 'proxy' machine Postfix is also running and it deliver locally to LTMP
> via Socket:
> 
> virtual_transport = lmtp:unix:private/dovecot-lmtp
> 
> Dovecot there is also configured to proxy LTMP:
> 
> lmtp_proxy = yes
> 
> service lmtp {
>   unix_listener /var/spool/postfix/private/dovecot-lmtp {
>     group = postfix
>     mode = 0600
>     user = postfix
>   }
> }
> 
> So far so good. A telnet to localhost 110 or 143 allows me to log in to the
> POP3/IMAP.
> 
> When Postfix delivers the message locally to Dovecot through LTMP it tries to
> proxy it though.
> 
> When doing so it tries to connect to TCP port 0 (zero).
> 
> dovecot: lmtp(22580): Error: lmtp client: connect(mbox01.XXXX.nl, 0) failed:
> Connection refused
> 
> I know I can return the 'port' field in the userdb query, but the same query
> is
> used for POP3, IMAP and LMTP. So that can't be hardcoded.
> 
> I fixed it for now with a CASE statement in SQL:
> 
> password_query = SELECT b.hostname AS host, NULL AS password, \
>        'Y' AS nopassword, u.email AS destuser, 'Y' AS proxy, \
>        CASE '%s' WHEN 'lmtp' THEN 2525 WHEN 'pop3' THEN 110 WHEN 'imap' THEN
> 143
> END AS port \
> FROM User u, Backend b, Domain d \
> WHERE u.domainID = d.domainID \
> AND b.backendID = d.backendID \
> AND u.email = '%u'
> 
> %s is a variable containing the service Dovecot is trying to look up.
> 
> This is however rather hacky.
> 
> On my destination machine LMTP is listening on port 2525. Is there any way to
> tell the Dovecot LTMP client to connect to port 2525 by default?
> 
> Thanks,
> 
> Wido