Ethereal-users: Re: [ethereal-users] Cannot initiate a capture session

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From: Guy Harris <gharris@xxxxxxxxxxxx>
Date: Tue, 4 Jul 2000 11:38:29 -0700
On Tue, Jul 04, 2000 at 06:51:56PM +0200, Andrea wrote:
> So the Linux box has 3 interfaces: eth0, ippp0 and lo.
> I have to trace which packets coming from the win98 client cause unwanted
> dial on demand on the linux box, so I try to capture packets on the eth0
> interface.
> But I receive the following message: "The capture session could not be
> initiated (socket: invalid argument). Please check to make sure you have
> sufficient permissions, and that you have the proper interface specified".
> Well, I have sufficient permissions, since I run as root, and I think I
> have the proper interface specified, since everything is working.
> This happens if I try to capture on ippp0 too.

What happens if you try to use tcpdump on the same interface?

If it works, you can use tcpdump (you may want to use a "-s 65535"
argument, so that it captures all the packet data) as a workaround; let
us know if that happens.

If it *doesn't* work (I suspect it won't), you may not have the
mechanism used for packet capture configured into your kernel; I don't
know what option that is (and it may differ between the 2.0[.x] and
2.2[.x]/2.3[.x]/2.4[.x] kernels) - others may be able to tell you which
switch you have to flip.