Hi,
   in sys/mbuf.h there exists some macros to store/extract private context
information in a mbuf, so.

/*
 * Allow drivers and/or protocols to use the rcvif member of
 * PKTHDR mbufs to store private context information.
 */
#define	M_GETCTX(m, t)		((t) (m)->m_pkthdr.rcvif + 0)
#define	M_SETCTX(m, c)		((void) ((m)->m_pkthdr.rcvif = (void *) (c)))


is there a good reason for the '+ 0' in M_GETCTX? I get compiler
complaints extracting a 'void *' because of the pointer arithmetic..

The type is actually irrelevant for me since all I am doing is passing
unknown context information to a far away function which knows what the
type is. I ended up using

	void *arg = M_GETCTX(m, uint8_t *);

which looks .. strange.

iain