Summary: tcp_wrapper w/ telnet problem

From: Janet Leung (
Date: Thu Aug 21 1997 - 18:31:44 CDT

Thanks to:
Ian MacPhedran <>
Brian Mullen <>
Steve Kives <>
Michael Baumann <>
Mark Bergman <>
Mike Frisch <>
Marina Daniels <>
1. Likely you compiled tcpd with PARANOID defined. Recompile it without
   this switch. If you still need PARANOID behaviour, compile with
   PROCESS_OPTIONS defined, and use the hosts_access(5) controls.
2. tcp_wrappers does a double look-up from IP->hostname and then
   hostname->IP, and any discrepancy is treated as a spoofing attack and
   the connection refused. Try nslookups both directions to see if
   that's the problem.

Original question/problem
We have installed tcp_wrappers version 7.6 on our solaris system. When we
enable tcpd on telnet, we have problem with "connection closed by foreign
host" when people from outside telnet to our domain, and the console
window shows the following:

in.telnetd[nnn]: Warning: host name/address mismatch, 123.456.789.1 !=

That is, the outside host IP address does not match with its name.
However, you could do nslookup for their name and IP addresses. This
might seem to be the case when one host has several IP addresses.

However, if we just run:
telnet stream tcp nowait root /usr/sbin/in.telnetd in.telnetd

Everything seems fine. Does anybody know what went sour here? How can
tcp_wrapper deal with those mismatch warnings?

Janet Leung, TACTech Inc., Yorba Linda, CA 92887

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