Date: Thu, 28 Jul 2005 16:15:27 +0000 From: "Karl O. Pinc" <kop@meme.com> To: pf@benzedrine.cx Cc: freebsd-pf@freebsd.org Subject: Re: pinging same host on the internet from two different LAN stations Message-ID: <1122567327l.19571l.1l@mofo> In-Reply-To: <20050728093738.GH15154@insomnia.benzedrine.cx> (from daniel@benzedrine.cx on Thu Jul 28 04:37:38 2005) References: <31BA35C490DBFC40B5C331C7987835AE61236C@mbafmail.internal.mba-cpa.com> <42E88BEC.4060007@xs4all.nl> <20050728093738.GH15154@insomnia.benzedrine.cx>
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On 07/28/2005 04:37:38 AM, Daniel Hartmeier wrote:
> Assuming Windows ping is not doing that, you'll have to provide an
> alternative way to decide which client to send replies to. There's
> ICMP
> sequence numbers, but they can and will overlap for concurrent ping
> invokations. The ICMP echo reply quotes the ICMP payload of the query.
> But most ping tools will use a constant payload, so that's no
> distinguishing criterion. The NAT device could tamper with the payload
> and insert its own ID there, but that's modifying the packet in an
> intrusive and unexpected way.
>
> I'm curious how any NAT device would do that correctly without relying
> on unique/random ICMP ids.
I cannot speak to how anything is implemented anywhere, but it seems to
me that the NAT device could substitute it's own ICMP ID,
which it saves in a state table associated with the sending
IP. When the ICMP reply returns it would then put the original
ICMP id back. This scheme swaps ICMP IDs in a fashion analogous
to the swapping of ports in TCP/UDP NAT port mapping.
I imagine this would require another kind of pf translation
declaration.
Regards,
Karl <kop@meme.com>
Free Software: "You don't pay back, you pay forward."
-- Robert A. Heinlein
P.S. I remain anxious to hear whether I'd be wasting
my time pursuing inbound traffic bandwidth management.
The thread is:
http://marc.theaimsgroup.com/?t=112139406900001&r=1&w=2
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