Automatically inferring %d on multi-domain virtual install ?

[Gabriel L. Somlo]

Hi,

I'm trying to allow domain-less logins for a multi-domain virtual IMAP
server, and wondering if I can automatically infer the domain (value of
variable %d) from the local IP (%l) or the hostname used by the client
when connecting to my server.

Let's say I have two host names: mail.foo.org (10.0.0.100) and
mail.bar.com (10.0.0.200), with forward and reverse DNS configured to
resolve A and PTR records in either direction.

Let's also say I have 10.0.0.100 and 10.0.0.200 set up as secondaries
on my server's loopback interface, and routing is set up to bring client
traffic to me for both of those IP addresses.

The relevant bits of my dovecot.conf are:

---%<------------------------------------------------------------------
mail_location = maildir:/var/lib/vmail/%d/%n
passdb {
  driver = passwd-file
  args = /var/lib/vmail/etc/postfix/userdb
}
userdb {
  driver = static
  args = uid=dovenull gid=dovenull home=/var/lib/vmail/%d/%n
}
---%<------------------------------------------------------------------

And my userdb passwd-file right now includes:

---%<------------------------------------------------------------------
user1 at foo.org:{PLAIN}user1foo
user2 at foo.org:{PLAIN}user2foo
user1 at bar.com:{PLAIN}user1bar
user2 at bar.com:{PLAIN}user2bar
---%<------------------------------------------------------------------

Right now, user1 at foo.org must configure their imap client like so:

	IMAP server: mail.foo.org
	username: user1 at foo.org
	password: user1foo

I would like to require this (and other) users to only have to set:

	IMAP server: mail.foo.org
	username: user1
	password: ...

and have dovecot somehow infer the "@foo.org" domain based on the fact
that the connection was made to 10.0.0.100, which is mail.foo.org, and
therefore the domain can *only* be "@foo.org".

I could start out by splitting my user database into two files:

userdb.foo.org
---%<------------------------------------------------------------------
user1:{PLAIN}user1foo
user2:{PLAIN}user2foo
---%<------------------------------------------------------------------

userdb.bar.com
---%<------------------------------------------------------------------
user1:{PLAIN}user1bar
user2:{PLAIN}user2bar
---%<------------------------------------------------------------------

... then modify dovecot.conf's passdb setup like so:

---%<------------------------------------------------------------------
passdb {
  driver = passwd-file
  args = /var/lib/vmail/etc/postfix/userdb.%d
}
---%<------------------------------------------------------------------

... but how would I insure that %d is set to the proper value based
on e.g. a reverse lookup of %l, which, in foo.org's case would be
10.0.0.100, and resolve to mail.foo.org, and *somehow* that would
match %d == "@foo.org" ?

Is this even possible in the first place, or am I just being too fussy
about the aesthetics of my users' imap client config files ? :) :)

Thanks much,
--Gabriel