[Dovecot] BUG dovecot and nginx

[Tobias Oetiker]

we have setup a two level proxy configuration for our zimbra server:

  [ dovecot 2.2.12 (imap proxy mode) ]
         V
  [ nginx (imap proxy mode) ]
         V
  [ zimbra imap server]

and it does not work ... after tying a login, the connection just
hangs and ends after 30 seconds with a timeout.

- if I try again rightaway in the same dovecot connection, the login
  goes though without trouble.

- looking at this with tshark I can see that on the second attempt,
  there is no capabilities query, dovecot just goes ahead and
  connects.

if we drop nginx from the setup all is well also (login works
directly as expected)

- investigating the traffic differences between the setups with and
  without nginx, we find that for some reason dovecot does not
  react to the capabily answer from nginx.  while it seems to
  happily accept the same answer when it is coming from zimbra
  directly.

- the only difference I can see on the wire is that nginx is much
  quicker (2.5ms) in responding than the zimbra (25ms) server and
  that the position of the STARTTLS and SASL=PLAIN capabilities in
  the capability answer differs between the two.

any ideas ?

cheers
tobi

-- 
Tobi Oetiker, OETIKER+PARTNER AG, Aarweg 15 CH-4600 Olten, Switzerland
www.oetiker.ch tobi at oetiker.ch +41 62 775 9902
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