tech-net: purpose of mbuf type MT

Subject: purpose of mbuf type MT_HEADER
To: None <tech-net@netbsd.org>
From: Pavel Cahyna <pcah8322@artax.karlin.mff.cuni.cz>
List: tech-net
Date: 10/01/2004 11:38:10

Hello,

what is the purpose of mbuf type MT_HEADER? How is it different from
MT_DATA? The manual page says only "data is a packet header", which is not
clear - aren't headers of upper-layer protocols just data for lower-layer
ones?

(I'm trying to resolve PR kern/26937, the problem happens when m_cat is
called to join a MT_HEADER mbuf with a MT_DATA one.)

Bye	Pavel