[pups] Networking With 2.11 BSD and Begemot Emulator

Greg Lehey grog at lemis.com
Thu Oct 5 13:03:25 AEST 2000

On Wednesday,  4 October 2000 at  8:24:07 -0700, Steven M. Schultz wrote:
> Hi -
>> From: Greg Lehey <grog at lemis.com>
>> No, that wasn't me.  FreeBSD doesn't have a tap driver.  Do you mean
>> Frank?
> 	Sure it does.  The FreeBSD 4.1.1 release notes say so  ;)
> 	Before that the 'if_tap.c' module was available (for some time)
> 	as a download that could be retrieved from the author's site.

I stand corrected:

> revision 1.1
> date: 2000/07/20 17:01:10;  author: nsayer;  state: Exp;
> Add the tap driver.
> The tap driver is used to present a virtual Ethernet interface to the
> system. Packets presented by the network stack to the interface are
> made available to a character device in /dev. With tap and the bridge
> code, you can make remote bridge configurations where both sides of
> the bridge are separated by userland daemons.
> This driver also has a special naming hack to allow it to serve a similar
> purpose to the vmware port.
> Submitted by:   myevmenkin at att.com, vsilyaev at mindspring.com

Ah well, I still haven't used it.

>>> 	The missing piece I forgot earlier was on the hosting machine's
>>> 	side to publish an ARP entry for the simulated 11.
>> I'm pretty sure we weren't using arp at all.  tun is a point-to-point
>> interface.
> 	The reason for publishing an ARP entry on the hosting system is
> 	so that other systems on the LAN know how to get to the simulated
> 	11 via the P11 hosting system.   If the hosting system doesn't
> 	publish an ARP entry the gateway, etc won't know to send the packets
> 	to the machine running P11.

I did that with a static route entry.

>>> 	I'm not sure how ARP can be made to work thru the 'tun' device.
>> I don't think it can.  I think Harti used some magic there.
> 	I know it can't - I asked him about it :)   That's when I first
> 	discovered that nothing was able to communicate with the simulated
> 	11 - the 11 will not send anything unless it's able to get a
> 	response to its ARP request.   On the hosting side it would be
> 	possible perhaps to use a "interface route" but 2.11 can not do that
> 	and will block waiting for an ARPREPLY.

As I say, it's not that simple.  I used it without trouble for years.
Recently something broke, and I suspect it trashed my root file
system, and I haven't had time to go back and fix it.  Since others
have the rest running, it's obviously nothing fundamental.

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