[546] in linux-net channel archive
Re: How to hook PPP frames into tcpdump?
daemon@ATHENA.MIT.EDU (Alan Cox)
Tue Jun 20 06:23:15 1995
From: iialan@iifeak.swan.ac.uk (Alan Cox)
To: callahan@maths.ox.ac.uk (Michael Callahan)
Date: Tue, 20 Jun 1995 09:33:10 +0100 (BST)
Cc: longyear@netcom.com, linux-net@vger.rutgers.edu
In-Reply-To: <Pine.3.89.9506200023.A14585-0100000@stlawrence.maths> from "Michael Callahan" at Jun 20, 95 01:03:40 am
> packet.c contains the code that actually handles forwarding the packets
> up to the tcpdump process.
>
> 1) what skb->len should be when you call the ptype->func function
Length of frame - length of hardware header. Thats about to change but
since it changes both sides of net_bh() it doesnt matter. [Getting ready
for variable length 16byte aligned stuff]
> 2) how the PPP framing is disentangled by tcpdump, which I assume expects
> to get packets with ethernet framing
The SOCK_PACKET code hands up the frame after HDLC framing has been removed.
Its up to tcpdump to check the type of the device the packet came from so it
knows how to interpret the frame.
Alan
