[OT]Tcp wrappers

[irvine.russell@edu.hel.fi]

Hello all

I have 2 questions that relate to tcp 
wrappers.

1) How exactly are the files hosts.allow 
and hosts.deny read.

>From what I have read, it works as follows:

  hosts.allow is read first. 
  The first rule that applies to the host 
  trying to make a connection is applied.
  If no rule that applies is found, then
  hosts.deny is read.

  In hosts.deny the first rule that applies
  to the connecting host is applied. If no
  rule is found in hosts.deny then the 
  connection is allowed.

I was wondering because a friend wanted to
deny a host by putting an entry for that host
in hosts.deny like the following:

  /etc/hosts.deny
  ALL: ALL
  sendmail:  irritating.spammer.ru
  <snip>

But then he had a hosts.allow file like the 
following:
  /etc/hosts.allow
  <snip>
  sendmail: ALL
  <snip>

His logic was that hosts.deny would deny
irritating.spammer.ru and hosts.allow would
allow all other hosts.

I was wondering 

  a) whether the sendmail entry in hosts.deny
     is of any use, and
  b) doesn't the hosts.allow entry allow the domain 
     irritating.spammer.ru anyway?

2) My second shorter question was, how can one
know if a program has been compiled with the
libwrap library.

Or at least how would I know if exim has been
compiled with libwrap. I had read on the list
that exim was compiled with libwrap but when 
I did ldd /usr/sbin/exim I see no mention of
libwrap. I use potato and exim version 3.12..

thanx in advance and a Very Merry Christmas
to everyone celebrating X-mas.

t:Irvine