Subject: Re: Strange packet redirection
To: Rick Byers <firstname.lastname@example.org>
From: John F. Woods <email@example.com>
Date: 05/20/1999 17:38:06
> I've got a NetBSD-1.4 machine doing for my local network (192.168.149.*)
> over my cable modem. I have a WEIRD situation where the gateway machine
> is redirecting packets to itself when it should just be translating the
> source address.
> For example, if (from my PC at 192.168.149.16) I telnet to 126.96.36.199,
> it establishes a connetion with the gateway machine instead! tcpdump on
> the internal network shows what I would expect, but the gateway machine
> never sends the packets out, it just handles them itself. This has
> happened with a few other (seemingly random, but I didn't look hard)
> destination IP addresses. If I clear ALL NAT rules and flush the NAT
> table, this still happens.
This is happening on my PC without NAT being configured at all! I believe
there is something badly broken in the forwarding code that is allowing the
forwarder to conclude that completely random addresses are local, but there
is nothing obvious in a quick inspection of the code.