>It would appear that the behaviour of m_copy()/m_copym() is changed,
>depending on whether or not M_EXT is set.  If M_EXT is set, then the

	I believe the above is the normal behavior, and this has been there
	for a very long time.  See TCP/IP Illustrated volume 2, section 2.9.
	To handle, for example, IPsec ESP header (which requires total
	modification of the packet), we reimplement mbuf chain copying,
	without cluster sharing, in few places.

itojun