MSIZE
#define MLEN ((int)(MSIZE - MHSIZE))
#define MHLEN ((int)(MSIZE - MPKTHSIZE))
#ifndef MSIZE
CTASSERT(MSIZE - offsetof(struct mbuf, m_dat) == MLEN);
CTASSERT(MSIZE - offsetof(struct mbuf, m_pktdat) == MHLEN);
sMBufCache = create_object_cache("mbufs", MSIZE, 0);