Date: Thu, 22 Jul 1999 15:47:08 -0700 (PDT) From: Divya Mehra <divya@nttmcl.com> To: Brian Somers <brian@FreeBSD.org.uk> Cc: Brian Somers <brian@Awfulhak.org>, freebsd-questions@FreeBSD.ORG Subject: Re: bpf and user PPP ( tun0 ) Message-ID: <Pine.GSO.3.95LJ1.1b4.990722152324.27027A-100000@alicia.nttmcl.com> In-Reply-To: <199907221104.MAA01143@keep.lan.Awfulhak.org>
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Thanks for the value input !
I am still not clear about the following :
Can tcpdump be used to capture ppp control packets ( req,ack etc)
After starting ppp0 and a ping over it, tcdump could dump the ping
packets. But I could not dump the PPP control packets.
Is there some way to dump the ppp control packets ?
Thanks,
Divya
**************************************************************************
Divyashikha Mehra NTT Multimedia Communications Laboratories
Computer Systems Designer 250 Cambridge Avenue, Suite 205
650-833-3655 (Voice) Palo Alto, CA 940040, USA.
mailto : divya@nttmcl.com
***************************************************************************
On Thu, 22 Jul 1999, Brian Somers wrote:
>
> > I invoked the BIOSETIF command before actually reading the the ppp
> > packets.
> >
> > 1) For tun0 i.e user PPP it returns error "Network down".
> > Only after PPP is up can I proceed further ( IPCP phase up). So I could
> > not capture any PPP packets. Is my approach correct ?
>
> As soon as ppp opens the tun device, it brings it UP. If you're
> getting "Network down" this should mean that ppp isn't running on
> that interface.
>
> > BIOGCGDLT returns DLT_NULL . Is that correct ? should it not be
> > returning DLT_PPP ?
>
> Dunno, I've never gone near the bpf device - tcpdump is the height of
> my knowledge in this area. However, DLT_NULL makes a lot of sense as
> bpf has no clue what's got the tun device open.
>
> > 2) For ppp0 what should BIOGDLT be returning ?
>
> I don't know much about the ppp interface - except that the code
> stinks :-I I would *expect* DLT_PPP, but again, bpf doesn't know, so
> I wouldn't be that surprised if it return DLT_NULL too.
>
> Disclaimer: I haven't looked at the if_ppp code to answer this, nor
> do I want to ;^1
>
> > thanks,
> > Divya
> >
> >
> > **************************************************************************
> > Divyashikha Mehra NTT Multimedia Communications Laboratories
> > Computer Systems Designer 250 Cambridge Avenue, Suite 205
> > 650-833-3655 (Voice) Palo Alto, CA 940040, USA.
> > mailto : divya@nttmcl.com
> > ***************************************************************************
> >
> >
> > On Tue, 20 Jul 1999, Brian Somers wrote:
> >
> > > > Hi,
> > > >
> > > > Can anyone tell me if bpf support user ppp packet ( tun 0 device) or it
> > > > can be used only for kernel ppp ( ppp0 device ) ?
> > >
> > > Yes.
> > >
> > > > If it can support user ppp then what value should BIOSETIF be returning
> > > > when bpf is to be used for reading ppp packets?
> > >
> > > >From the bpf man page:
> > >
> > > BIOCSETIF (struct ifreq) Sets the hardware interface associate with
> > > the file. This command must be performed before any pack-
> > > ets can be read. The device is indicated by name using
> > > the ifr_name field of the ifreq structure. Additionally,
> > > performs the actions of BIOCFLUSH.
> > >
> > > > Thanks,
> > > > Divya
> > > >
> > > > **************************************************************************
> > > > Divyashikha Mehra NTT Multimedia Communications Laboratories
> > > > Computer Systems Designer 250 Cambridge Avenue, Suite 205
> > > > 650-833-3655 (Voice) Palo Alto, CA 940040, USA.
> > > > mailto : divya@nttmcl.com
> > > > ***************************************************************************
>
> --
> Brian <brian@Awfulhak.org> <brian@FreeBSD.org>
> <http://www.Awfulhak.org>; <brian@OpenBSD.org>
> Don't _EVER_ lose your sense of humour ! <brian@FreeBSD.org.uk>
>
>
>
> --KAA00746.932634953/keep.lan.Awfulhak.org--
>
>
>
>
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