Why does Samba do reverse DNS lookups for clients?

Daryl L. Biberdorf darylb at superserve.com
Mon Sep 14 03:04:04 GMT 1998

Thanks to a couple of pointers from readers here, plus the
PROFILES.txt documentation (that wasn't in the old 1.9.17xx 
distribution I was using), I got profiles/policies working.

However, another issue has cropped up for us. We had a network
outage last week that cut our subnet off from any DNS nameservers.
At that point, Samba quit working. Looking at the logs, client
computers (named LAB01, LAB02, etc.) were trying to communicate
to the Samba server. The server, however, is apparently trying
to do a reverse DNS lookup using Gethostbyaddr(). This call is
failing, and the client-server connection is never completed. I 
took at look at the code, and it appears that util.c defines
a function client_name() that is making the call. (Please forgive
me if the source file and function name aren't quite right.)

Everything was working fine until the DNS outage, even though
NONE of the client computers have entries in the DNS server
or in the server's /etc/hosts file.

I'm concerned about this because I can't figure out why
Samba needs to do a reverse DNS lookup. My system in
particular uses DHCP to assign IP address to clients dynamically.

Our system is running Samba 1.9.18p10 on Linux with a 2.0.35
kernel. Clients are Windows 95.

Can anyone give me any suggestions as to how to deal with this?
Or why Samba needs the reverse DNS? Will the presence of
a minimal caching DNS server on our subnet fix the problem? Why?

Thanks very much in advance for any help.

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