MEXTADD
MEXTADD(m, mcl, MYX_RXBIG_SIZE, M_EXTWR, MEXTFREE_POOL, myx_mcl_pool);
MEXTADD(m, block + off, PAGE_SIZE, M_EXTWR,
MEXTADD(m, buf, pp->pr_size, M_EXTWR, MEXTFREE_POOL, pp);
MEXTADD(m, pkt, sizeof(*pkt), M_EXTWR,