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Re: Slow and Fast IP addresses on http ?

  • From: Richard A Steenbergen
  • Date: Tue Jun 17 13:58:41 2003

On Tue, Jun 17, 2003 at 05:14:49PM +0000, Paul Vixie wrote:
> ("Steven M. Bellovin") writes:
> > It might also be port 113 -- some sites try to query your tcp port 113, 
> > and wait for a timeout if the port is firewalled.  A better solution 
> > than blocking it is to send an immediate RST.
> people who depend on tcp/113 deserve everything stupid that happens to them.
> dropping SYN packets or returning a fixed string are both better than sending
> an immediate RST.  (false confidence being valued less than low confidence.)
> i was rather shocked to discover tcp/113 clientness enabled by default in
> postfix and sendmail.  but even widespread ignorance does not call for
> widespread coddling such as returning immediate RST's.

If you are the only user of your machine, feel free to return whatever you
want. However, there are still people out there running these things
called servers, where multiple users have accounts, and ident is a 
perfectly valid and useful protocol for providing some accountability 
against non-root abuse.

You could also run a DNS server which doesn't return any kind of answer
for your reverse DNS if you so desired, but you should be prepared to have
the rest of the world delay your connections on certain services while
they try to figure out why you can't play nice like everyone else. Any 
time you decide not to return an RST, you are making the decision to 
violate rfc's and may be punished with timeouts accordingly. Rate limiting 
RSTs is a perfectly valid method of handling this.

Richard A Steenbergen <>
GPG Key ID: 0xF8B12CBC (7535 7F59 8204 ED1F CC1C 53AF 4C41 5ECA F8B1 2CBC)

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