Subject: Re: /dev/tap and tcpdump don't go together very well?
To: Greg Troxel <firstname.lastname@example.org>
From: Rhialto <email@example.com>
Date: 04/08/2007 15:24:46
On Sun 08 Apr 2007 at 06:47:14 -0400, Greg Troxel wrote:
> Please be far more clear about how this is all supposed to work.
I wish I could point to some easy example program, but alas. What I'm
using involves a pdp-10 emulator with TOPS-20 (http://panda.trailing-edge.com)
plus some private patches to add /dev/tap to it.
(http://www.falu.nl/~rhialto/klh-diffs should be all, if I did it right)
Is there some system program or possibly something in pkgsrc that I can
try, that uses /dev/tap, so that we can verify independently? Writing a
separate program that injects some packets into /dev/tap isn't so
difficult but I am currently wondering how one would verify that they
arrive at the other end.
> Running tcpdump on the host as '-i tap0' will put the tap device in
> promiscuous mode. But packets should still function in both directions.
I looked at the source (of course) and I could find no obvious
explanation. That's why I was wondering if perhaps it was some
non-obvious but known problem.
> Try adding -p to not force promiscuous mode.
Interesting. I still see (the? all?) packets with tcpdump, but the
telnet connection still functions. This may be a clue towards finding
> Greg Troxel <firstname.lastname@example.org>
___ Olaf 'Rhialto' Seibert -- You author it, and I'll reader it.
\X/ rhialto/at/xs4all.nl -- Cetero censeo "authored" delendum esse.