From owner-freebsd-net  Mon Apr  8  7:27: 0 2002
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	(envelope-from nick@rogness.net)
Date: Mon, 8 Apr 2002 09:34:18 -0500 (CDT)
From: Nick Rogness <nick@rogness.net>
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To: cjclark@alum.mit.edu
Cc: "Matthew D. Fuller" <fullermd@over-yonder.net>,
	Alex Rousskov <rousskov@measurement-factory.com>,
	freebsd-net@FreeBSD.ORG
Subject: Re: Forcing packets to the wire
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On Sun, 7 Apr 2002, Crist J. Clark wrote:

> On Sun, Apr 07, 2002 at 08:25:33PM -0500, Nick Rogness wrote:
> > 

[SNIP]
> > 
> > AFAIK, the route to get from 1 interface to the other is not
> > through the lo0.  I'm not sure if the kernel sends these packets
> > across lo0 (internally) or not.  But the routing table would
> > suggest not.
> 
> It sure looks like they do. I checked before suggesting this.
> 
>   $ ifconfig dc0
>   dc0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
>           inet 192.168.64.60 netmask 0xffffff00 broadcast 192.168.64.255
>           inet6 fe80::2c0:f0ff:fe5a:6c0a%dc0 prefixlen 64 scopeid 0x1 
>           inet 192.168.64.61 netmask 0xffffffff broadcast 192.168.64.61
>           ether 00:c0:f0:5a:6c:0a 
>           media: Ethernet autoselect (10baseT/UTP)
>           status: active
>    $telnet -s 192.168.64.60 192.168.64.61
>    Trying 192.168.64.61...
>    telnet: connect to address 192.168.64.61: Connection refused
>    telnet: Unable to connect to remote host
> 
> And I was sniffing the loopback when I did this,
> 
>   # tcpdump -n -ilo0
>   tcpdump: listening on lo0

>   20:02:34.300094 192.168.64.60.1979 > 192.168.64.61.23: S
> 2453490862:2453490862(0) win 65535 <mss 16344,nop,wscale
> 1,nop,nop,timestamp 11409532 0> (DF) [tos 0x10]
>   20:02:34.300138 192.168.64.61.23 > 192.168.64.60.1979: R 0:0(0) ack
> 2453490863 win 0

> 
> I also put in some ipfw(8) 'count' rules like, 
> 
>   # ipfw add count ip from 192.168.64.60 to 192.168.64.61 out via lo0
> 
> And they were hit by these packets.


	WOW, that's interesting.  Thanks for the heads up.

Nick Rogness <nick@rogness.net>
 - Don't mind me...I'm just sniffing your packets


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