tcpd - How can I disable reverse lookups

tcpd - How can I disable reverse lookups

Post by Ian » Thu, 13 May 1999 04:00:00

I have had a look at the source of tcpd to try to disable reverse lookups,
but I'm in over my head.

My problem is that if a use dhcp to assign IPs to my client, when they try
to get mail diald starts up. I've figured this out to be tcpd doing a
reverse lookup and the man pages says it's a compile time option but I can't
find how to knobble it.

Unfortunately my C is a bit crap. Any help would offered would be greatfully



1. Disable ns reverse lookup for telnet

when I telnet an host, its telnet daemon performs a reverse lookup to know
the name of the telnetter. This cause a certain delay to have the prompt,
and sometimes the connection fails.
Do you know how to disable this dns reverse lookup?
Note that the dns must stay enabled in nsswitch.conf, otherwise that host
won't use the dns anymore, and it is
needed for other purposes. And I cannot solve the telnetter ip address into
the name, since I can't know all the possible ip addresses to reverse-solve
into the names.

For example: the telnetter is, I need to disable the query to (as stated below).
Nov 19 17:08:14 nut named[23358]:

The environment: linux mandrake 7.1.

Any idea?
Thank you in advance.

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