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Date:      Sat, 1 Jul 2000 12:37:20 +0100 (BST)
From:      Jan Grant <Jan.Grant@bristol.ac.uk>
To:        net@freebsd.org
Subject:   Ingress filtering to loopback address: is there any way to do this    without a full firewall install?
Message-ID:  <Pine.GHP.4.21.0007011234270.21667-100000@mail.ilrt.bris.ac.uk>

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Sorry about the repost; I sent this to questions with no response.

For a random service running on a random machine:

On machine A (192.168.0.1):
hostA:/> netstat -an | grep 5998
tcp4       0      0  127.0.0.1.5998         *.*          LISTEN

On machine B: (192.168.0.2):*
hostB:/> ifconfig lo down
hostB:/> route add -host 127.0.0.1 gw 192.168.0.1
hostB:/> telnet 127.0.0.1 5998
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
RANDOMSERVICE (hostA) welcomes you...

Is there a way to stop the delivery of non-localhost-originated packets
to services listening on a loopback address without building a firewall
into the kernel?

Cheers in advance,
jan 

PS. I'd appreciate a CC: directly; I'm not (currently) subscribed to
fbsd-net. Thanks!

* This machine was "another free unix-a-like" hence the interface name,
etc.

-- 
jan grant, ILRT, University of Bristol. http://www.ilrt.bris.ac.uk/
Tel +44(0)117 9287163 Fax +44 (0)117 9287112 RFC822 jan.grant@bris.ac.uk
If it's broken really badly - don't fix it either.




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