On 15 Mar 2014, at 00:48, Hooman Fazaeli <hoomanfazaeli at gmail.com> wrote: > What about the area started at (m->m_ext + 1) whose size is (MHLEN - sizeof(struct m_ext))? > Is there any known uses of this area in the stack? I'm not sure what you mean by m_ext + 1, but what are you trying to do? If you need to tag an mbuf, use mbuf tags. -- Rui Paulo