Index: head/share/man/man9/mbpool.9
===================================================================
--- head/share/man/man9/mbpool.9
+++ head/share/man/man9/mbpool.9
@@ -27,7 +27,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd July 15, 2003
+.Dd September 27, 2017
 .Dt MBPOOL 9
 .Os
 .Sh NAME
@@ -50,7 +50,7 @@
 .Ft void
 .Fn mbp_free "struct mbpool *mbp" "void *p"
 .Ft void
-.Fn mbp_ext_free "void *" "void *"
+.Fn mbp_ext_free "struct mbuf *"
 .Ft void
 .Fn mbp_card_free "struct mbpool *mbp"
 .Ft void
@@ -223,8 +223,6 @@
 can be given to
 .Fn m_extadd
 as the free function.
-The user argument must be the pointer to
-the pool.
 .Pp
 Before using the contents of a buffer returned by the card, the driver
 must call
Index: head/share/man/man9/mbuf.9
===================================================================
--- head/share/man/man9/mbuf.9
+++ head/share/man/man9/mbuf.9
@@ -24,7 +24,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd October 10, 2016
+.Dd September 27, 2017
 .Dt MBUF 9
 .Os
 .\"
@@ -44,12 +44,12 @@
 .Fn MCLGET "struct mbuf *mbuf" "int how"
 .Fo MEXTADD
 .Fa "struct mbuf *mbuf"
-.Fa "caddr_t buf"
+.Fa "char *buf"
 .Fa "u_int size"
-.Fa "void (*free)(void *opt_arg1, void *opt_arg2)"
+.Fa "void (*free)(struct mbuf *)"
 .Fa "void *opt_arg1"
 .Fa "void *opt_arg2"
-.Fa "short flags"
+.Fa "int flags"
 .Fa "int type"
 .Fc
 .\"
@@ -416,8 +416,13 @@
 .Fa opt_arg1
 and
 .Fa opt_arg2
-arguments will be passed unmodified to
-.Fa free .
+arguments will be saved in
+.Va ext_arg1
+and
+.Va ext_arg2
+fields of the
+.Va struct m_ext
+of the mbuf.
 The
 .Fa flags
 argument specifies additional
Index: head/sys/compat/ndis/kern_ndis.c
===================================================================
--- head/sys/compat/ndis/kern_ndis.c
+++ head/sys/compat/ndis/kern_ndis.c
@@ -495,17 +495,21 @@
 	KeReleaseSpinLock(&block->nmb_returnlock, irql);
 }
 
+static void
+ndis_ext_free(struct mbuf *m)
+{
+
+	return (ndis_return_packet(m->m_ext.ext_arg1));
+}
+
 void
-ndis_return_packet(struct mbuf *m, void *buf, void *arg)
+ndis_return_packet(ndis_packet *p)
 {
-	ndis_packet		*p;
 	ndis_miniport_block	*block;
 
-	if (arg == NULL)
+	if (p == NULL)
 		return;
 
-	p = arg;
-
 	/* Decrement refcount. */
 	p->np_refcnt--;
 
@@ -676,9 +680,8 @@
 			return (ENOBUFS);
 		}
 		m->m_len = MmGetMdlByteCount(buf);
-		m->m_data = MmGetMdlVirtualAddress(buf);
-		MEXTADD(m, m->m_data, m->m_len, ndis_return_packet,
-		    m->m_data, p, 0, EXT_NDIS);
+		m_extadd(m, MmGetMdlVirtualAddress(buf), m->m_len,
+		    ndis_ext_free, p, NULL, 0, EXT_NDIS);
 		p->np_refcnt++;
 
 		totlen += m->m_len;
Index: head/sys/compat/ndis/ndis_var.h
===================================================================
--- head/sys/compat/ndis/ndis_var.h
+++ head/sys/compat/ndis/ndis_var.h
@@ -1743,7 +1743,7 @@
 extern int ndis_shutdown_nic(void *);
 extern int ndis_pnpevent_nic(void *, int);
 extern int ndis_init_nic(void *);
-extern void ndis_return_packet(struct mbuf *, void *, void *);
+extern void ndis_return_packet(ndis_packet *);
 extern int ndis_init_dma(void *);
 extern int ndis_destroy_dma(void *);
 extern int ndis_create_sysctls(void *);
Index: head/sys/dev/cas/if_cas.c
===================================================================
--- head/sys/dev/cas/if_cas.c
+++ head/sys/dev/cas/if_cas.c
@@ -133,7 +133,7 @@
 static int	cas_disable_rx(struct cas_softc *sc);
 static int	cas_disable_tx(struct cas_softc *sc);
 static void	cas_eint(struct cas_softc *sc, u_int status);
-static void	cas_free(struct mbuf *m, void *arg1, void* arg2);
+static void	cas_free(struct mbuf *m);
 static void	cas_init(void *xsc);
 static void	cas_init_locked(struct cas_softc *sc);
 static void	cas_init_regs(struct cas_softc *sc);
@@ -1732,16 +1732,10 @@
 				refcount_acquire(&rxds->rxds_refcount);
 				bus_dmamap_sync(sc->sc_rdmatag,
 				    rxds->rxds_dmamap, BUS_DMASYNC_POSTREAD);
-#if __FreeBSD_version < 800016
-				MEXTADD(m, (caddr_t)rxds->rxds_buf +
+				m_extadd(m, (char *)rxds->rxds_buf +
 				    off * 256 + ETHER_ALIGN, len, cas_free,
-				    rxds, M_RDONLY, EXT_NET_DRV);
-#else
-				MEXTADD(m, (caddr_t)rxds->rxds_buf +
-				    off * 256 + ETHER_ALIGN, len, cas_free,
 				    sc, (void *)(uintptr_t)idx,
 				    M_RDONLY, EXT_NET_DRV);
-#endif
 				if ((m->m_flags & M_EXT) == 0) {
 					m_freem(m);
 					m = NULL;
@@ -1779,16 +1773,10 @@
 				m->m_len = min(CAS_PAGE_SIZE - off, len);
 				bus_dmamap_sync(sc->sc_rdmatag,
 				    rxds->rxds_dmamap, BUS_DMASYNC_POSTREAD);
-#if __FreeBSD_version < 800016
-				MEXTADD(m, (caddr_t)rxds->rxds_buf + off,
-				    m->m_len, cas_free, rxds, M_RDONLY,
-				    EXT_NET_DRV);
-#else
-				MEXTADD(m, (caddr_t)rxds->rxds_buf + off,
+				m_extadd(m, (char *)rxds->rxds_buf + off,
 				    m->m_len, cas_free, sc,
 				    (void *)(uintptr_t)idx, M_RDONLY,
 				    EXT_NET_DRV);
-#endif
 				if ((m->m_flags & M_EXT) == 0) {
 					m_freem(m);
 					m = NULL;
@@ -1818,19 +1806,11 @@
 						    sc->sc_rdmatag,
 						    rxds2->rxds_dmamap,
 						    BUS_DMASYNC_POSTREAD);
-#if __FreeBSD_version < 800016
-						MEXTADD(m2,
-						    (caddr_t)rxds2->rxds_buf,
-						    m2->m_len, cas_free,
-						    rxds2, M_RDONLY,
-						    EXT_NET_DRV);
-#else
-						MEXTADD(m2,
-						    (caddr_t)rxds2->rxds_buf,
+						m_extadd(m2,
+						    (char *)rxds2->rxds_buf,
 						    m2->m_len, cas_free, sc,
 						    (void *)(uintptr_t)idx2,
 						    M_RDONLY, EXT_NET_DRV);
-#endif
 						if ((m2->m_flags & M_EXT) ==
 						    0) {
 							m_freem(m2);
@@ -1889,21 +1869,15 @@
 }
 
 static void
-cas_free(struct mbuf *m, void *arg1, void *arg2)
+cas_free(struct mbuf *m)
 {
 	struct cas_rxdsoft *rxds;
 	struct cas_softc *sc;
 	u_int idx, locked;
 
-#if __FreeBSD_version < 800016
-	rxds = arg2;
-	sc = rxds->rxds_sc;
-	idx = rxds->rxds_idx;
-#else
-	sc = arg1;
-	idx = (uintptr_t)arg2;
+	sc = m->m_ext.ext_arg1;
+	idx = (uintptr_t)m->m_ext.ext_arg2;
 	rxds = &sc->sc_rxdsoft[idx];
-#endif
 	if (refcount_release(&rxds->rxds_refcount) == 0)
 		return;
 
Index: head/sys/dev/cas/if_casvar.h
===================================================================
--- head/sys/dev/cas/if_casvar.h
+++ head/sys/dev/cas/if_casvar.h
@@ -119,10 +119,6 @@
 	void *rxds_buf;			/* receive buffer */
 	bus_dmamap_t rxds_dmamap;	/* our DMA map */
 	bus_addr_t rxds_paddr;		/* physical address of the segment */
-#if __FreeBSD_version < 800016
-	struct cas_softc *rxds_sc;	/* softc pointer */
-	u_int rxds_idx;			/* our index */
-#endif
 	u_int rxds_refcount;		/* hardware + mbuf references */
 };
 
@@ -239,18 +235,7 @@
 	__CAS_UPDATE_RXDESC(&(sc)->sc_rxdescs[(d)],			\
 	    &(sc)->sc_rxdsoft[(s)], (s))
 
-#if __FreeBSD_version < 800016
-#define	CAS_INIT_RXDESC(sc, d, s)					\
-do {									\
-	struct cas_rxdsoft *__rxds = &(sc)->sc_rxdsoft[(s)];		\
-									\
-	__rxds->rxds_sc = (sc);						\
-	__rxds->rxds_idx = (s);						\
-	__CAS_UPDATE_RXDESC(&(sc)->sc_rxdescs[(d)], __rxds, (s));	\
-} while (0)
-#else
 #define	CAS_INIT_RXDESC(sc, d, s)	CAS_UPDATE_RXDESC(sc, d, s)
-#endif
 
 #define	CAS_LOCK_INIT(_sc, _name)					\
 	mtx_init(&(_sc)->sc_mtx, _name, MTX_NETWORK_LOCK, MTX_DEF)
Index: head/sys/dev/cxgbe/t4_sge.c
===================================================================
--- head/sys/dev/cxgbe/t4_sge.c
+++ head/sys/dev/cxgbe/t4_sge.c
@@ -1670,10 +1670,10 @@
 }
 
 static void
-rxb_free(struct mbuf *m, void *arg1, void *arg2)
+rxb_free(struct mbuf *m)
 {
-	uma_zone_t zone = arg1;
-	caddr_t cl = arg2;
+	uma_zone_t zone = m->m_ext.ext_arg1;
+	void *cl = m->m_ext.ext_arg2;
 
 	uma_zfree(zone, cl);
 	counter_u64_add(extfree_rels, 1);
Index: head/sys/dev/cxgbe/tom/t4_cpl_io.c
===================================================================
--- head/sys/dev/cxgbe/tom/t4_cpl_io.c
+++ head/sys/dev/cxgbe/tom/t4_cpl_io.c
@@ -1979,9 +1979,9 @@
 }
 
 static void
-t4_aiotx_mbuf_free(struct mbuf *m, void *buffer, void *arg)
+t4_aiotx_mbuf_free(struct mbuf *m)
 {
-	struct aiotx_buffer *ab = buffer;
+	struct aiotx_buffer *ab = m->m_ext.ext_arg1;
 
 #ifdef VERBOSE_TRACES
 	CTR3(KTR_CXGBE, "%s: completed %d bytes for tid %d", __func__,
Index: head/sys/dev/dpaa/if_dtsec_rm.c
===================================================================
--- head/sys/dev/dpaa/if_dtsec_rm.c
+++ head/sys/dev/dpaa/if_dtsec_rm.c
@@ -337,11 +337,13 @@
  * @{
  */
 static void
-dtsec_rm_fqr_mext_free(struct mbuf *m, void *buffer, void *arg)
+dtsec_rm_fqr_mext_free(struct mbuf *m)
 {
 	struct dtsec_softc *sc;
+	void *buffer;
 
-	sc = arg;
+	buffer = m->m_ext.ext_arg1;
+	sc = m->m_ext.ext_arg2;
 	if (bman_count(sc->sc_rx_pool) <= DTSEC_RM_POOL_RX_MAX_SIZE)
 		bman_put_buffer(sc->sc_rx_pool, buffer);
 	else
Index: head/sys/dev/if_ndis/if_ndis.c
===================================================================
--- head/sys/dev/if_ndis/if_ndis.c
+++ head/sys/dev/if_ndis/if_ndis.c
@@ -1418,7 +1418,7 @@
 			p = packets[i];
 			if (p->np_oob.npo_status == NDIS_STATUS_SUCCESS) {
 				p->np_refcnt++;
-				(void)ndis_return_packet(NULL ,p, block);
+				ndis_return_packet(p);
 			}
 		}
 		return;
@@ -1431,7 +1431,7 @@
 		if (ndis_ptom(&m0, p)) {
 			device_printf(sc->ndis_dev, "ptom failed\n");
 			if (p->np_oob.npo_status == NDIS_STATUS_SUCCESS)
-				(void)ndis_return_packet(NULL, p, block);
+				ndis_return_packet(p);
 		} else {
 #ifdef notdef
 			if (p->np_oob.npo_status == NDIS_STATUS_RESOURCES) {
Index: head/sys/dev/iscsi_initiator/isc_soc.c
===================================================================
--- head/sys/dev/iscsi_initiator/isc_soc.c
+++ head/sys/dev/iscsi_initiator/isc_soc.c
@@ -70,12 +70,13 @@
  | function for freeing external storage for mbuf
  */
 static void
-ext_free(struct mbuf *m, void *a, void *b)
+ext_free(struct mbuf *m)
 {
-     pduq_t *pq = b;
+     pduq_t *pq = m->m_ext.ext_arg1;
 
      if(pq->buf != NULL) {
-	  debug(3, "ou_refcnt=%d a=%p b=%p", ou_refcnt, a, pq->buf);
+	  debug(3, "ou_refcnt=%d a=%p b=%p",
+	       ou_refcnt, m->m_ext.ext_buf, pq->buf);
 	  free(pq->buf, M_ISCSIBUF);
 	  pq->buf = NULL;
      }
@@ -137,11 +138,8 @@
 	       md->m_ext.ext_cnt = &ou_refcnt;
 	       l = min(MCLBYTES, len);
 	       debug(4, "setting ext_free(arg=%p len/l=%d/%d)", pq->buf, len, l);
-	       MEXTADD(md, pp->ds_addr + off, l, ext_free, 
-#if __FreeBSD_version >= 800000
-		       pp->ds_addr + off,
-#endif
-		       pq, 0, EXT_EXTREF);
+	       m_extadd(md, pp->ds_addr + off, l, ext_free, pq, NULL, 0,
+		    EXT_EXTREF);
 	       md->m_len = l;
 	       md->m_next = NULL;
 	       mh->m_pkthdr.len += l;
Index: head/sys/dev/lge/if_lge.c
===================================================================
--- head/sys/dev/lge/if_lge.c
+++ head/sys/dev/lge/if_lge.c
@@ -123,7 +123,7 @@
 static int lge_alloc_jumbo_mem(struct lge_softc *);
 static void lge_free_jumbo_mem(struct lge_softc *);
 static void *lge_jalloc(struct lge_softc *);
-static void lge_jfree(struct mbuf *, void *, void *);
+static void lge_jfree(struct mbuf *);
 
 static int lge_newbuf(struct lge_softc *, struct lge_rx_desc *, struct mbuf *);
 static int lge_encap(struct lge_softc *, struct mbuf *, u_int32_t *);
@@ -689,7 +689,7 @@
 	struct mbuf		*m;
 {
 	struct mbuf		*m_new = NULL;
-	caddr_t			*buf = NULL;
+	char			*buf = NULL;
 
 	if (m == NULL) {
 		MGETHDR(m_new, M_NOWAIT, MT_DATA);
@@ -710,10 +710,9 @@
 			return(ENOBUFS);
 		}
 		/* Attach the buffer to the mbuf */
-		m_new->m_data = (void *)buf;
 		m_new->m_len = m_new->m_pkthdr.len = LGE_JUMBO_FRAMELEN;
-		MEXTADD(m_new, buf, LGE_JUMBO_FRAMELEN, lge_jfree,
-		    buf, (struct lge_softc *)sc, 0, EXT_NET_DRV);
+		m_extadd(m_new, buf, LGE_JUMBO_FRAMELEN, lge_jfree, sc, NULL,
+		    0, EXT_NET_DRV);
 	} else {
 		m_new = m;
 		m_new->m_len = m_new->m_pkthdr.len = LGE_JUMBO_FRAMELEN;
@@ -848,20 +847,20 @@
  * Release a jumbo buffer.
  */
 static void
-lge_jfree(struct mbuf *m, void *buf, void *args)
+lge_jfree(struct mbuf *m)
 {
 	struct lge_softc	*sc;
 	int		        i;
 	struct lge_jpool_entry   *entry;
 
 	/* Extract the softc struct pointer. */
-	sc = args;
+	sc = m->m_ext.ext_arg1;
 
 	if (sc == NULL)
 		panic("lge_jfree: can't find softc pointer!");
 
 	/* calculate the slot this buffer belongs to */
-	i = ((vm_offset_t)buf
+	i = ((vm_offset_t)m->m_ext.ext_buf
 	     - (vm_offset_t)sc->lge_cdata.lge_jumbo_buf) / LGE_JLEN;
 
 	if ((i < 0) || (i >= LGE_JSLOTS))
Index: head/sys/dev/mwl/if_mwl.c
===================================================================
--- head/sys/dev/mwl/if_mwl.c
+++ head/sys/dev/mwl/if_mwl.c
@@ -2522,12 +2522,12 @@
 }
 
 static void
-mwl_ext_free(struct mbuf *m, void *data, void *arg)
+mwl_ext_free(struct mbuf *m)
 {
-	struct mwl_softc *sc = arg;
+	struct mwl_softc *sc = m->m_ext.ext_arg1;
 
 	/* XXX bounds check data */
-	mwl_putrxdma(sc, data);
+	mwl_putrxdma(sc, m->m_ext.ext_buf);
 	/*
 	 * If we were previously blocked by a lack of rx dma buffers
 	 * check if we now have enough to restart rx interrupt handling.
@@ -2746,8 +2746,8 @@
 		 * descriptor using the replacement dma
 		 * buffer we just installed above.
 		 */
-		MEXTADD(m, data, MWL_AGGR_SIZE, mwl_ext_free,
-		    data, sc, 0, EXT_NET_DRV);
+		m_extadd(m, data, MWL_AGGR_SIZE, mwl_ext_free, sc, NULL, 0,
+		    EXT_NET_DRV);
 		m->m_data += off - hdrlen;
 		m->m_pkthdr.len = m->m_len = pktlen;
 		/* NB: dma buffer assumed read-only */
Index: head/sys/dev/netmap/netmap_generic.c
===================================================================
--- head/sys/dev/netmap/netmap_generic.c
+++ head/sys/dev/netmap/netmap_generic.c
@@ -166,7 +166,7 @@
  * has a KASSERT(), checking that the mbuf dtor function is not NULL.
  */
 
-static void void_mbuf_dtor(struct mbuf *m, void *arg1, void *arg2) { }
+static void void_mbuf_dtor(struct mbuf *m) { }
 
 #define SET_MBUF_DESTRUCTOR(m, fn)	do {		\
 	(m)->m_ext.ext_free = (fn != NULL) ?		\
@@ -624,7 +624,7 @@
 	 * txsync. */
 	netmap_generic_irq(na, r, NULL);
 #ifdef __FreeBSD__
-	void_mbuf_dtor(m, NULL, NULL);
+	void_mbuf_dtor(m);
 #endif
 }
 
Index: head/sys/dev/wb/if_wb.c
===================================================================
--- head/sys/dev/wb/if_wb.c
+++ head/sys/dev/wb/if_wb.c
@@ -143,7 +143,7 @@
 static int wb_attach(device_t);
 static int wb_detach(device_t);
 
-static void wb_bfree(struct mbuf *, void *addr, void *args);
+static void wb_bfree(struct mbuf *);
 static int wb_newbuf(struct wb_softc *, struct wb_chain_onefrag *,
 		struct mbuf *);
 static int wb_encap(struct wb_softc *, struct wb_chain *, struct mbuf *);
@@ -824,7 +824,7 @@
 }
 
 static void
-wb_bfree(struct mbuf *m, void *buf, void *args)
+wb_bfree(struct mbuf *m)
 {
 }
 
@@ -843,10 +843,9 @@
 		MGETHDR(m_new, M_NOWAIT, MT_DATA);
 		if (m_new == NULL)
 			return(ENOBUFS);
-		m_new->m_data = c->wb_buf;
 		m_new->m_pkthdr.len = m_new->m_len = WB_BUFBYTES;
-		MEXTADD(m_new, c->wb_buf, WB_BUFBYTES, wb_bfree, c->wb_buf,
-		    NULL, 0, EXT_NET_DRV);
+		m_extadd(m_new, c->wb_buf, WB_BUFBYTES, wb_bfree, NULL, NULL,
+		    0, EXT_NET_DRV);
 	} else {
 		m_new = m;
 		m_new->m_len = m_new->m_pkthdr.len = WB_BUFBYTES;
Index: head/sys/kern/kern_mbuf.c
===================================================================
--- head/sys/kern/kern_mbuf.c
+++ head/sys/kern/kern_mbuf.c
@@ -504,7 +504,7 @@
 #endif
 	m = (struct mbuf *)arg;
 	if (m != NULL) {
-		m->m_ext.ext_buf = (caddr_t)mem;
+		m->m_ext.ext_buf = (char *)mem;
 		m->m_data = m->m_ext.ext_buf;
 		m->m_flags |= M_EXT;
 		m->m_ext.ext_free = NULL;
@@ -688,15 +688,13 @@
 		case EXT_DISPOSABLE:
 			KASSERT(m->m_ext.ext_free != NULL,
 				("%s: ext_free not set", __func__));
-			(*(m->m_ext.ext_free))(m, m->m_ext.ext_arg1,
-			    m->m_ext.ext_arg2);
+			m->m_ext.ext_free(m);
 			uma_zfree(zone_mbuf, mref);
 			break;
 		case EXT_EXTREF:
 			KASSERT(m->m_ext.ext_free != NULL,
 				("%s: ext_free not set", __func__));
-			(*(m->m_ext.ext_free))(m, m->m_ext.ext_arg1,
-			    m->m_ext.ext_arg2);
+			m->m_ext.ext_free(m);
 			break;
 		default:
 			KASSERT(m->m_ext.ext_type == 0,
@@ -918,9 +916,8 @@
  *    Nothing.
  */
 void
-m_extadd(struct mbuf *mb, caddr_t buf, u_int size,
-    void (*freef)(struct mbuf *, void *, void *), void *arg1, void *arg2,
-    int flags, int type)
+m_extadd(struct mbuf *mb, char *buf, u_int size, m_ext_free_t freef,
+    void *arg1, void *arg2, int flags, int type)
 {
 
 	KASSERT(type != EXT_CLUSTER, ("%s: EXT_CLUSTER not allowed", __func__));
Index: head/sys/kern/subr_mbpool.c
===================================================================
--- head/sys/kern/subr_mbpool.c
+++ head/sys/kern/subr_mbpool.c
@@ -281,10 +281,10 @@
  * Mbuf system external mbuf free routine
  */
 void
-mbp_ext_free(struct mbuf *m, void *buf, void *arg)
+mbp_ext_free(struct mbuf *m)
 {
 
-	mbp_free(arg, buf);
+	mbp_free(m->m_ext.ext_arg2, m->m_ext.ext_arg1);
 }
 
 /*
Index: head/sys/sys/mbpool.h
===================================================================
--- head/sys/sys/mbpool.h
+++ head/sys/sys/mbpool.h
@@ -69,7 +69,7 @@
 void mbp_free(struct mbpool *, void *);
 
 /* free a chunk that is an external mbuf */
-void mbp_ext_free(struct mbuf *, void *, void *);
+void mbp_ext_free(struct mbuf *);
 
 /* free all buffers that are marked to be on the card */
 void mbp_card_free(struct mbpool *);
Index: head/sys/sys/mbuf.h
===================================================================
--- head/sys/sys/mbuf.h
+++ head/sys/sys/mbuf.h
@@ -197,17 +197,17 @@
  * Compile-time assertions in uipc_mbuf.c test these values to ensure that
  * they are correct.
  */
+typedef	void m_ext_free_t(struct mbuf *);
 struct m_ext {
 	union {
 		volatile u_int	 ext_count;	/* value of ref count info */
 		volatile u_int	*ext_cnt;	/* pointer to ref count info */
 	};
-	caddr_t		 ext_buf;	/* start of buffer */
+	char		*ext_buf;	/* start of buffer */
 	uint32_t	 ext_size;	/* size of buffer, for ext_free */
 	uint32_t	 ext_type:8,	/* type of external storage */
 			 ext_flags:24;	/* external storage mbuf flags */
-	void		(*ext_free)	/* free routine if not the usual */
-			    (struct mbuf *, void *, void *);
+	m_ext_free_t	*ext_free;	/* free routine if not the usual */
 	void		*ext_arg1;	/* optional argument pointer */
 	void		*ext_arg2;	/* optional argument pointer */
 };
@@ -436,10 +436,10 @@
 
 #define	EXT_FLAG_NOFREE		0x000010	/* don't free mbuf to pool, notyet */
 
-#define	EXT_FLAG_VENDOR1	0x010000	/* for vendor-internal use */
-#define	EXT_FLAG_VENDOR2	0x020000	/* for vendor-internal use */
-#define	EXT_FLAG_VENDOR3	0x040000	/* for vendor-internal use */
-#define	EXT_FLAG_VENDOR4	0x080000	/* for vendor-internal use */
+#define	EXT_FLAG_VENDOR1	0x010000	/* These flags are vendor */
+#define	EXT_FLAG_VENDOR2	0x020000	/* or submodule specific, */
+#define	EXT_FLAG_VENDOR3	0x040000	/* not used by mbuf code. */
+#define	EXT_FLAG_VENDOR4	0x080000	/* Set/read by submodule. */
 
 #define	EXT_FLAG_EXP1		0x100000	/* for experimental use */
 #define	EXT_FLAG_EXP2		0x200000	/* for experimental use */
@@ -610,9 +610,8 @@
 		    void (*)(char *, caddr_t, u_int));
 struct mbuf	*m_dup(const struct mbuf *, int);
 int		 m_dup_pkthdr(struct mbuf *, const struct mbuf *, int);
-void		 m_extadd(struct mbuf *, caddr_t, u_int,
-		    void (*)(struct mbuf *, void *, void *), void *, void *,
-		    int, int);
+void		 m_extadd(struct mbuf *, char *, u_int, m_ext_free_t,
+		    void *, void *, int, int);
 u_int		 m_fixhdr(struct mbuf *);
 struct mbuf	*m_fragment(struct mbuf *, int, int);
 void		 m_freem(struct mbuf *);
@@ -667,8 +666,8 @@
  * Associated an external reference counted buffer with an mbuf.
  */
 static __inline void
-m_extaddref(struct mbuf *m, caddr_t buf, u_int size, u_int *ref_cnt,
-    void (*freef)(struct mbuf *, void *, void *), void *arg1, void *arg2)
+m_extaddref(struct mbuf *m, char *buf, u_int size, u_int *ref_cnt,
+    m_ext_free_t freef, void *arg1, void *arg2)
 {
 
 	KASSERT(ref_cnt != NULL, ("%s: ref_cnt not provided", __func__));
@@ -864,7 +863,7 @@
 #define	MGETHDR(m, how, type)	((m) = m_gethdr((how), (type)))
 #define	MCLGET(m, how)		m_clget((m), (how))
 #define	MEXTADD(m, buf, size, free, arg1, arg2, flags, type)		\
-    m_extadd((m), (caddr_t)(buf), (size), (free), (arg1), (arg2),	\
+    m_extadd((m), (char *)(buf), (size), (free), (arg1), (arg2),	\
     (flags), (type))
 #define	m_getm(m, len, how, type)					\
     m_getm2((m), (len), (how), (type), M_PKTHDR)