[ILUG] Checking for IP protocols

[Martin Feeney]

On Sun, 02 Sep 2001 12:50:49 kevin lyda wrote:
> On Fri, Aug 31, 2001 at 06:04:11PM +0100, kevin lyda wrote:
> > On Fri, Aug 31, 2001 at 05:14:59PM +0100, Martin Feeney wrote:
> > > Anyone know of any tool along the lines of netstat, lsof or fuser that'll
> > > let you check for the existance of progs listening on IP protocols other
> > > than tcp/udp? I'm talking about protocols such as GRE(47), ESP(50) and
> > > AH(51).
> > no clue, but do you have good places for info on the protocols you
> > mentioned?

A little background:

I'm currently using poptop (http://poptop.lineo.com/) to link two LANs
together and to provide VPN "dial-in" support. That has some issues with
the latest 2.4 kernels (i.e. LAN<->LAN doesn't work anymore).

I'm looking to replace the LAN<->LAN support with freeswan/ipsec
(http://www.freeswan.org) and have both serve VPN "dial-in".

Now while trying to debug what was going wrong with the 2.4.9 kernel
installation, I kept wondering to myself if a tool like the one I
mentioned above existed. On both sides it would have been nice to see
which (if any) or both open up their gre connection(and when) in relation
to each other. Tcpdump would only tell me when there was traffic happening
on those protos. I could tell that the communication was failing, but not
whether the client had failed to open the socket or whether it had
prematurely closed it.

In the end I had a very good idea of what was happening, but not exactly
why, so I rolled back to 2.4.7 and all was happy.

It'd be nice to know what's going on at an IP level if and when the tunnel
goes down for any reason.

Martin.