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33 * @(#)uipc_mbuf.c 8.2 (Berkeley) 1/4/94
34 * $FreeBSD: src/sys/kern/uipc_mbuf.c,v 1.51.2.24 2003/04/15 06:59:29 silby Exp $
35 * $DragonFly: src/sys/kern/uipc_mbuf.c,v 1.6 2003/07/19 21:09:24 dillon Exp $
38 #include "opt_param.h"
39 #include "opt_mbuf_stress_test.h"
40 #include <sys/param.h>
41 #include <sys/systm.h>
42 #include <sys/malloc.h>
44 #include <sys/kernel.h>
45 #include <sys/sysctl.h>
46 #include <sys/domain.h>
47 #include <sys/protosw.h>
48 #include <sys/thread.h>
49 #include <sys/globaldata.h>
52 #include <vm/vm_kern.h>
53 #include <vm/vm_extern.h>
56 #include <machine/cpu.h>
59 static void mbinit __P((void *));
60 SYSINIT(mbuf, SI_SUB_MBUF, SI_ORDER_FIRST, mbinit, NULL)
65 u_long mbtypes[MT_NTYPES];
67 union mcluster *mclfree;
76 #ifdef MBUF_STRESS_TEST
77 int m_defragrandomfailures;
82 u_int m_mballoc_wid = 0;
83 u_int m_clalloc_wid = 0;
85 SYSCTL_DECL(_kern_ipc);
86 SYSCTL_INT(_kern_ipc, KIPC_MAX_LINKHDR, max_linkhdr, CTLFLAG_RW,
88 SYSCTL_INT(_kern_ipc, KIPC_MAX_PROTOHDR, max_protohdr, CTLFLAG_RW,
89 &max_protohdr, 0, "");
90 SYSCTL_INT(_kern_ipc, KIPC_MAX_HDR, max_hdr, CTLFLAG_RW, &max_hdr, 0, "");
91 SYSCTL_INT(_kern_ipc, KIPC_MAX_DATALEN, max_datalen, CTLFLAG_RW,
93 SYSCTL_INT(_kern_ipc, OID_AUTO, mbuf_wait, CTLFLAG_RW,
95 SYSCTL_STRUCT(_kern_ipc, KIPC_MBSTAT, mbstat, CTLFLAG_RW, &mbstat, mbstat, "");
96 SYSCTL_OPAQUE(_kern_ipc, OID_AUTO, mbtypes, CTLFLAG_RD, mbtypes,
97 sizeof(mbtypes), "LU", "");
98 SYSCTL_INT(_kern_ipc, KIPC_NMBCLUSTERS, nmbclusters, CTLFLAG_RD,
99 &nmbclusters, 0, "Maximum number of mbuf clusters available");
100 SYSCTL_INT(_kern_ipc, OID_AUTO, nmbufs, CTLFLAG_RD, &nmbufs, 0,
101 "Maximum number of mbufs available");
102 SYSCTL_INT(_kern_ipc, OID_AUTO, m_defragpackets, CTLFLAG_RD,
103 &m_defragpackets, 0, "");
104 SYSCTL_INT(_kern_ipc, OID_AUTO, m_defragbytes, CTLFLAG_RD,
105 &m_defragbytes, 0, "");
106 SYSCTL_INT(_kern_ipc, OID_AUTO, m_defraguseless, CTLFLAG_RD,
107 &m_defraguseless, 0, "");
108 SYSCTL_INT(_kern_ipc, OID_AUTO, m_defragfailure, CTLFLAG_RD,
109 &m_defragfailure, 0, "");
110 #ifdef MBUF_STRESS_TEST
111 SYSCTL_INT(_kern_ipc, OID_AUTO, m_defragrandomfailures, CTLFLAG_RW,
112 &m_defragrandomfailures, 0, "");
115 static void m_reclaim __P((void));
118 #define NMBCLUSTERS (512 + maxusers * 16)
121 #define NMBUFS (nmbclusters * 4)
125 * Perform sanity checks of tunables declared above.
128 tunable_mbinit(void *dummy)
132 * This has to be done before VM init.
134 nmbclusters = NMBCLUSTERS;
135 TUNABLE_INT_FETCH("kern.ipc.nmbclusters", &nmbclusters);
137 TUNABLE_INT_FETCH("kern.ipc.nmbufs", &nmbufs);
139 if (nmbufs < nmbclusters * 2)
140 nmbufs = nmbclusters * 2;
144 SYSINIT(tunable_mbinit, SI_SUB_TUNABLES, SI_ORDER_ANY, tunable_mbinit, NULL);
146 /* "number of clusters of pages" */
158 mmbfree = NULL; mclfree = NULL;
159 mbstat.m_msize = MSIZE;
160 mbstat.m_mclbytes = MCLBYTES;
161 mbstat.m_minclsize = MINCLSIZE;
162 mbstat.m_mlen = MLEN;
163 mbstat.m_mhlen = MHLEN;
166 if (m_mballoc(NMB_INIT, M_DONTWAIT) == 0)
168 #if MCLBYTES <= PAGE_SIZE
169 if (m_clalloc(NCL_INIT, M_DONTWAIT) == 0)
172 /* It's OK to call contigmalloc in this context. */
173 if (m_clalloc(16, M_WAIT) == 0)
183 * Allocate at least nmb mbufs and place on mbuf free list.
184 * Must be called at splimp.
197 * If we've hit the mbuf limit, stop allocating from mb_map,
198 * (or trying to) in order to avoid dipping into the section of
199 * mb_map which we've "reserved" for clusters.
201 if ((nmb + mbstat.m_mbufs) > nmbufs)
205 * Once we run out of map space, it will be impossible to get
206 * any more (nothing is ever freed back to the map)
207 * -- however you are not dead as m_reclaim might
208 * still be able to free a substantial amount of space.
210 * XXX Furthermore, we can also work with "recycled" mbufs (when
211 * we're calling with M_WAIT the sleep procedure will be woken
212 * up when an mbuf is freed. See m_mballoc_wait()).
217 nbytes = round_page(nmb * MSIZE);
218 p = (caddr_t)kmem_malloc(mb_map, nbytes, M_NOWAIT);
219 if (p == 0 && how == M_WAIT) {
221 p = (caddr_t)kmem_malloc(mb_map, nbytes, M_WAITOK);
225 * Either the map is now full, or `how' is M_NOWAIT and there
231 nmb = nbytes / MSIZE;
232 for (i = 0; i < nmb; i++) {
233 ((struct mbuf *)p)->m_next = mmbfree;
234 mmbfree = (struct mbuf *)p;
237 mbstat.m_mbufs += nmb;
238 mbtypes[MT_FREE] += nmb;
243 * Once the mb_map has been exhausted and if the call to the allocation macros
244 * (or, in some cases, functions) is with M_WAIT, then it is necessary to rely
245 * solely on reclaimed mbufs. Here we wait for an mbuf to be freed for a
246 * designated (mbuf_wait) time.
249 m_mballoc_wait(int caller, int type)
256 if ((tsleep(&m_mballoc_wid, PVM, "mballc", mbuf_wait)) == EWOULDBLOCK)
261 * Now that we (think) that we've got something, we will redo an
262 * MGET, but avoid getting into another instance of m_mballoc_wait()
263 * XXX: We retry to fetch _even_ if the sleep timed out. This is left
264 * this way, purposely, in the [unlikely] case that an mbuf was
265 * freed but the sleep was not awakened in time.
270 MGET(p, M_DONTWAIT, type);
273 MGETHDR(p, M_DONTWAIT, type);
276 panic("m_mballoc_wait: invalid caller (%d)", caller);
280 if (p != NULL) { /* We waited and got something... */
282 /* Wake up another if we have more free. */
290 #if MCLBYTES > PAGE_SIZE
291 static int i_want_my_mcl;
299 tsleep(&i_want_my_mcl, PVM, "mclalloc", 0);
301 for (; i_want_my_mcl; i_want_my_mcl--) {
302 if (m_clalloc(1, M_WAIT) == 0)
303 printf("m_clalloc failed even in process context!\n");
308 static struct thread *mclallocthread;
309 static struct kproc_desc mclalloc_kp = {
314 SYSINIT(mclallocthread, SI_SUB_KTHREAD_UPDATE, SI_ORDER_ANY, kproc_start,
319 * Allocate some number of mbuf clusters
320 * and place on cluster free list.
321 * Must be called at splimp.
334 * If we've hit the mcluster number limit, stop allocating from
335 * mb_map, (or trying to) in order to avoid dipping into the section
336 * of mb_map which we've "reserved" for mbufs.
338 if ((ncl + mbstat.m_clusters) > nmbclusters)
342 * Once we run out of map space, it will be impossible
343 * to get any more (nothing is ever freed back to the
344 * map). From this point on, we solely rely on freed
350 #if MCLBYTES > PAGE_SIZE
352 i_want_my_mcl += ncl;
353 wakeup(&i_want_my_mcl);
357 p = contigmalloc1(MCLBYTES * ncl, M_DEVBUF, M_WAITOK, 0ul,
358 ~0ul, PAGE_SIZE, 0, mb_map);
362 p = (caddr_t)kmem_malloc(mb_map, ctob(npg),
363 how != M_WAIT ? M_NOWAIT : M_WAITOK);
364 ncl = ncl * PAGE_SIZE / MCLBYTES;
367 * Either the map is now full, or `how' is M_NOWAIT and there
371 static int last_report ; /* when we did that (in ticks) */
374 if (ticks < last_report || (ticks - last_report) >= hz) {
376 printf("All mbuf clusters exhausted, please see tuning(7).\n");
381 for (i = 0; i < ncl; i++) {
382 ((union mcluster *)p)->mcl_next = mclfree;
383 mclfree = (union mcluster *)p;
387 mbstat.m_clusters += ncl;
392 * Once the mb_map submap has been exhausted and the allocation is called with
393 * M_WAIT, we rely on the mclfree union pointers. If nothing is free, we will
394 * sleep for a designated amount of time (mbuf_wait) or until we're woken up
395 * due to sudden mcluster availability.
404 /* If in interrupt context, and INVARIANTS, maintain sanity and die. */
405 KASSERT(mycpu->gd_intr_nesting_level == 0, ("CLALLOC: CANNOT WAIT IN INTERRUPT"));
408 /* Sleep until something's available or until we expire. */
410 if ((tsleep(&m_clalloc_wid, PVM, "mclalc", mbuf_wait)) == EWOULDBLOCK)
414 * Now that we (think) that we've got something, we will redo and
415 * MGET, but avoid getting into another instance of m_clalloc_wait()
418 MCLALLOC(p, M_DONTWAIT);
421 if (p != NULL) { /* We waited and got something... */
423 /* Wake up another if we have more free. */
433 * When MGET fails, ask protocols to free space when short of memory,
434 * then re-attempt to allocate an mbuf.
444 * Must only do the reclaim if not in an interrupt context.
448 KASSERT(mycpu->gd_intr_nesting_level == 0,
449 ("MBALLOC: CANNOT WAIT IN INTERRUPT"));
456 (void)m_mballoc(1, i);
465 m->m_data = m->m_dat;
470 static int last_report ; /* when we did that (in ticks) */
473 if (ticks < last_report || (ticks - last_report) >= hz) {
475 printf("All mbufs exhausted, please see tuning(7).\n");
483 * As above; retry an MGETHDR.
493 * Must only do the reclaim if not in an interrupt context.
497 KASSERT(mycpu->gd_intr_nesting_level == 0,
498 ("MBALLOC: CANNOT WAIT IN INTERRUPT"));
505 (void)m_mballoc(1, i);
514 m->m_data = m->m_pktdat;
515 m->m_flags = M_PKTHDR;
516 m->m_pkthdr.rcvif = NULL;
517 SLIST_INIT(&m->m_pkthdr.tags);
518 m->m_pkthdr.csum_flags = 0;
522 static int last_report ; /* when we did that (in ticks) */
526 if (ticks < last_report || (ticks - last_report) >= hz) {
528 printf("All mbufs exhausted, please see tuning(7).\n");
538 register struct domain *dp;
539 register struct protosw *pr;
542 for (dp = domains; dp; dp = dp->dom_next)
543 for (pr = dp->dom_protosw; pr < dp->dom_protoswNPROTOSW; pr++)
551 * Space allocation routines.
552 * These are also available as macros
553 * for critical paths.
564 (void)m_mballoc(1, how);
573 m->m_data = m->m_dat;
578 m = m_retry(how, type);
579 if (m == NULL && how == M_WAIT)
580 m = m_mballoc_wait(MGET_C, type);
594 (void)m_mballoc(1, how);
603 m->m_data = m->m_pktdat;
604 m->m_flags = M_PKTHDR;
605 m->m_pkthdr.rcvif = NULL;
606 SLIST_INIT(&m->m_pkthdr.tags);
607 m->m_pkthdr.csum_flags = 0;
611 m = m_retryhdr(how, type);
612 if (m == NULL && how == M_WAIT)
613 m = m_mballoc_wait(MGETHDR_C, type);
622 register struct mbuf *m;
627 bzero(mtod(m, caddr_t), MLEN);
632 * m_getcl() returns an mbuf with an attached cluster.
633 * Because many network drivers use this kind of buffers a lot, it is
634 * convenient to keep a small pool of free buffers of this kind.
635 * Even a small size such as 10 gives about 10% improvement in the
636 * forwarding rate in a bridge or router.
637 * The size of this free list is controlled by the sysctl variable
638 * mcl_pool_max. The list is populated on m_freem(), and used in
639 * m_getcl() if elements are available.
641 static struct mbuf *mcl_pool;
642 static int mcl_pool_now;
643 static int mcl_pool_max = 0;
645 SYSCTL_INT(_kern_ipc, OID_AUTO, mcl_pool_max, CTLFLAG_RW, &mcl_pool_max, 0,
646 "Maximum number of mbufs+cluster in free list");
647 SYSCTL_INT(_kern_ipc, OID_AUTO, mcl_pool_now, CTLFLAG_RD, &mcl_pool_now, 0,
648 "Current number of mbufs+cluster in free list");
651 m_getcl(int how, short type, int flags)
656 if (flags & M_PKTHDR) {
657 if (type == MT_DATA && mcl_pool) {
659 mcl_pool = mp->m_nextpkt;
662 mp->m_nextpkt = NULL;
663 mp->m_data = mp->m_ext.ext_buf;
664 mp->m_flags = M_PKTHDR|M_EXT;
665 mp->m_pkthdr.rcvif = NULL;
666 mp->m_pkthdr.csum_flags = 0;
669 MGETHDR(mp, how, type);
674 if ( (mp->m_flags & M_EXT) == 0) {
685 * m_getm(m, len, how, type)
687 * This will allocate len-worth of mbufs and/or mbuf clusters (whatever fits
688 * best) and return a pointer to the top of the allocated chain. If m is
689 * non-null, then we assume that it is a single mbuf or an mbuf chain to
690 * which we want len bytes worth of mbufs and/or clusters attached, and so
691 * if we succeed in allocating it, we will just return a pointer to m.
693 * If we happen to fail at any point during the allocation, we will free
694 * up everything we have already allocated and return NULL.
698 m_getm(struct mbuf *m, int len, int how, int type)
700 struct mbuf *top, *tail, *mp, *mtail = NULL;
702 KASSERT(len >= 0, ("len is < 0 in m_getm"));
707 else if (len > MINCLSIZE) {
709 if ((mp->m_flags & M_EXT) == 0) {
715 len -= M_TRAILINGSPACE(mp);
718 for (mtail = m; mtail->m_next != NULL; mtail = mtail->m_next);
730 if (len > MINCLSIZE) {
732 if ((mp->m_flags & M_EXT) == 0)
737 len -= M_TRAILINGSPACE(mp);
750 * MFREE(struct mbuf *m, struct mbuf *n)
751 * Free a single mbuf and associated external storage.
752 * Place the successor, if any, in n.
754 * we do need to check non-first mbuf for m_aux, since some of existing
755 * code does not call M_PREPEND properly.
756 * (example: call to bpf_mtap from drivers)
758 #define MFREE(m, n) MBUFLOCK( \
759 struct mbuf *_mm = (m); \
761 KASSERT(_mm->m_type != MT_FREE, ("freeing free mbuf")); \
762 mbtypes[_mm->m_type]--; \
763 if ((_mm->m_flags & M_PKTHDR) != 0) \
764 m_tag_delete_chain(_mm, NULL); \
765 if (_mm->m_flags & M_EXT) \
768 _mm->m_type = MT_FREE; \
769 mbtypes[MT_FREE]++; \
770 _mm->m_next = mmbfree; \
779 register struct mbuf *n;
792 * Try to keep a small pool of mbuf+cluster for quick use in
793 * device drivers. A good candidate is a M_PKTHDR buffer with
794 * only one cluster attached. Other mbufs, or those exceeding
795 * the pool size, are just m_free'd in the usual way.
796 * The following code makes sure that m_next, m_type,
797 * m_pkthdr.aux and m_ext.* are properly initialized.
798 * Other fields in the mbuf are initialized in m_getcl()
801 if (mcl_pool_now < mcl_pool_max && m && m->m_next == NULL &&
802 (m->m_flags & (M_PKTHDR|M_EXT)) == (M_PKTHDR|M_EXT) &&
803 m->m_type == MT_DATA && M_EXT_WRITABLE(m) ) {
804 m_tag_delete_chain(m, NULL);
805 m->m_nextpkt = mcl_pool;
816 * Mbuffer utility routines.
820 * Lesser-used path for M_PREPEND:
821 * allocate new mbuf to prepend to chain,
825 m_prepend(m, len, how)
826 register struct mbuf *m;
831 MGET(mn, how, m->m_type);
832 if (mn == (struct mbuf *)NULL) {
834 return ((struct mbuf *)NULL);
836 if (m->m_flags & M_PKTHDR)
837 M_MOVE_PKTHDR(mn, m);
847 * Make a copy of an mbuf chain starting "off0" bytes from the beginning,
848 * continuing for "len" bytes. If len is M_COPYALL, copy to end of mbuf.
849 * The wait parameter is a choice of M_WAIT/M_DONTWAIT from caller.
850 * Note that the copy is read-only, because clusters are not copied,
851 * only their reference counts are incremented.
853 #define MCFail (mbstat.m_mcfail)
856 m_copym(m, off0, len, wait)
857 register struct mbuf *m;
861 register struct mbuf *n, **np;
862 register int off = off0;
866 KASSERT(off >= 0, ("m_copym, negative off %d", off));
867 KASSERT(len >= 0, ("m_copym, negative len %d", len));
868 if (off == 0 && m->m_flags & M_PKTHDR)
871 KASSERT(m != NULL, ("m_copym, offset > size of mbuf chain"));
881 KASSERT(len == M_COPYALL,
882 ("m_copym, length > size of mbuf chain"));
885 MGET(n, wait, m->m_type);
890 if (!m_dup_pkthdr(n, m, wait))
892 if (len == M_COPYALL)
893 n->m_pkthdr.len -= off0;
895 n->m_pkthdr.len = len;
898 n->m_len = min(len, m->m_len - off);
899 if (m->m_flags & M_EXT) {
900 n->m_data = m->m_data + off;
901 if (m->m_ext.ext_ref == NULL) {
903 &mclrefcnt[mtocl(m->m_ext.ext_buf)], 1);
907 (*m->m_ext.ext_ref)(m->m_ext.ext_buf,
914 bcopy(mtod(m, caddr_t)+off, mtod(n, caddr_t),
916 if (len != M_COPYALL)
932 * Copy an entire packet, including header (which must be present).
933 * An optimization of the common case `m_copym(m, 0, M_COPYALL, how)'.
934 * Note that the copy is read-only, because clusters are not copied,
935 * only their reference counts are incremented.
936 * Preserve alignment of the first mbuf so if the creator has left
937 * some room at the beginning (e.g. for inserting protocol headers)
938 * the copies also have the room available.
945 struct mbuf *top, *n, *o;
947 MGET(n, how, m->m_type);
952 if (!m_dup_pkthdr(n, m, how))
955 if (m->m_flags & M_EXT) {
956 n->m_data = m->m_data;
957 if (m->m_ext.ext_ref == NULL)
958 atomic_add_char(&mclrefcnt[mtocl(m->m_ext.ext_buf)], 1);
962 (*m->m_ext.ext_ref)(m->m_ext.ext_buf,
969 n->m_data = n->m_pktdat + (m->m_data - m->m_pktdat );
970 bcopy(mtod(m, char *), mtod(n, char *), n->m_len);
975 MGET(o, how, m->m_type);
983 if (m->m_flags & M_EXT) {
984 n->m_data = m->m_data;
985 if (m->m_ext.ext_ref == NULL) {
987 &mclrefcnt[mtocl(m->m_ext.ext_buf)], 1);
991 (*m->m_ext.ext_ref)(m->m_ext.ext_buf,
998 bcopy(mtod(m, char *), mtod(n, char *), n->m_len);
1011 * Copy data from an mbuf chain starting "off" bytes from the beginning,
1012 * continuing for "len" bytes, into the indicated buffer.
1015 m_copydata(m, off, len, cp)
1016 register struct mbuf *m;
1021 register unsigned count;
1023 KASSERT(off >= 0, ("m_copydata, negative off %d", off));
1024 KASSERT(len >= 0, ("m_copydata, negative len %d", len));
1026 KASSERT(m != NULL, ("m_copydata, offset > size of mbuf chain"));
1033 KASSERT(m != NULL, ("m_copydata, length > size of mbuf chain"));
1034 count = min(m->m_len - off, len);
1035 bcopy(mtod(m, caddr_t) + off, cp, count);
1044 * Copy a packet header mbuf chain into a completely new chain, including
1045 * copying any mbuf clusters. Use this instead of m_copypacket() when
1046 * you need a writable copy of an mbuf chain.
1053 struct mbuf **p, *top = NULL;
1054 int remain, moff, nsize;
1059 KASSERT((m->m_flags & M_PKTHDR) != 0, ("%s: !PKTHDR", __FUNCTION__));
1061 /* While there's more data, get a new mbuf, tack it on, and fill it */
1062 remain = m->m_pkthdr.len;
1065 while (remain > 0 || top == NULL) { /* allow m->m_pkthdr.len == 0 */
1068 /* Get the next new mbuf */
1069 MGET(n, how, m->m_type);
1072 if (top == NULL) { /* first one, must be PKTHDR */
1073 if (!m_dup_pkthdr(n, m, how))
1076 } else /* not the first one */
1078 if (remain >= MINCLSIZE) {
1080 if ((n->m_flags & M_EXT) == 0) {
1088 /* Link it into the new chain */
1092 /* Copy data from original mbuf(s) into new mbuf */
1093 while (n->m_len < nsize && m != NULL) {
1094 int chunk = min(nsize - n->m_len, m->m_len - moff);
1096 bcopy(m->m_data + moff, n->m_data + n->m_len, chunk);
1100 if (moff == m->m_len) {
1106 /* Check correct total mbuf length */
1107 KASSERT((remain > 0 && m != NULL) || (remain == 0 && m == NULL),
1108 ("%s: bogus m_pkthdr.len", __FUNCTION__));
1119 * Concatenate mbuf chain n to m.
1120 * Both chains must be of the same type (e.g. MT_DATA).
1121 * Any m_pkthdr is not updated.
1125 register struct mbuf *m, *n;
1130 if (m->m_flags & M_EXT ||
1131 m->m_data + m->m_len + n->m_len >= &m->m_dat[MLEN]) {
1132 /* just join the two chains */
1136 /* splat the data from one into the other */
1137 bcopy(mtod(n, caddr_t), mtod(m, caddr_t) + m->m_len,
1139 m->m_len += n->m_len;
1149 register int len = req_len;
1150 register struct mbuf *m;
1153 if ((m = mp) == NULL)
1159 while (m != NULL && len > 0) {
1160 if (m->m_len <= len) {
1171 if (mp->m_flags & M_PKTHDR)
1172 m->m_pkthdr.len -= (req_len - len);
1175 * Trim from tail. Scan the mbuf chain,
1176 * calculating its length and finding the last mbuf.
1177 * If the adjustment only affects this mbuf, then just
1178 * adjust and return. Otherwise, rescan and truncate
1179 * after the remaining size.
1185 if (m->m_next == (struct mbuf *)0)
1189 if (m->m_len >= len) {
1191 if (mp->m_flags & M_PKTHDR)
1192 mp->m_pkthdr.len -= len;
1199 * Correct length for chain is "count".
1200 * Find the mbuf with last data, adjust its length,
1201 * and toss data from remaining mbufs on chain.
1204 if (m->m_flags & M_PKTHDR)
1205 m->m_pkthdr.len = count;
1206 for (; m; m = m->m_next) {
1207 if (m->m_len >= count) {
1214 (m = m->m_next) ->m_len = 0;
1219 * Rearange an mbuf chain so that len bytes are contiguous
1220 * and in the data area of an mbuf (so that mtod and dtom
1221 * will work for a structure of size len). Returns the resulting
1222 * mbuf chain on success, frees it and returns null on failure.
1223 * If there is room, it will add up to max_protohdr-len extra bytes to the
1224 * contiguous region in an attempt to avoid being called next time.
1226 #define MPFail (mbstat.m_mpfail)
1230 register struct mbuf *n;
1233 register struct mbuf *m;
1238 * If first mbuf has no cluster, and has room for len bytes
1239 * without shifting current data, pullup into it,
1240 * otherwise allocate a new mbuf to prepend to the chain.
1242 if ((n->m_flags & M_EXT) == 0 &&
1243 n->m_data + len < &n->m_dat[MLEN] && n->m_next) {
1244 if (n->m_len >= len)
1252 MGET(m, M_DONTWAIT, n->m_type);
1256 if (n->m_flags & M_PKTHDR)
1257 M_MOVE_PKTHDR(m, n);
1259 space = &m->m_dat[MLEN] - (m->m_data + m->m_len);
1261 count = min(min(max(len, max_protohdr), space), n->m_len);
1262 bcopy(mtod(n, caddr_t), mtod(m, caddr_t) + m->m_len,
1272 } while (len > 0 && n);
1286 * Partition an mbuf chain in two pieces, returning the tail --
1287 * all but the first len0 bytes. In case of failure, it returns NULL and
1288 * attempts to restore the chain to its original state.
1290 * Note that the resulting mbufs might be read-only, because the new
1291 * mbuf can end up sharing an mbuf cluster with the original mbuf if
1292 * the "breaking point" happens to lie within a cluster mbuf. Use the
1293 * M_WRITABLE() macro to check for this case.
1296 m_split(m0, len0, wait)
1297 register struct mbuf *m0;
1300 register struct mbuf *m, *n;
1301 unsigned len = len0, remain;
1303 for (m = m0; m && len > m->m_len; m = m->m_next)
1307 remain = m->m_len - len;
1308 if (m0->m_flags & M_PKTHDR) {
1309 MGETHDR(n, wait, m0->m_type);
1312 n->m_pkthdr.rcvif = m0->m_pkthdr.rcvif;
1313 n->m_pkthdr.len = m0->m_pkthdr.len - len0;
1314 m0->m_pkthdr.len = len0;
1315 if (m->m_flags & M_EXT)
1317 if (remain > MHLEN) {
1318 /* m can't be the lead packet */
1320 n->m_next = m_split(m, len, wait);
1321 if (n->m_next == 0) {
1329 MH_ALIGN(n, remain);
1330 } else if (remain == 0) {
1335 MGET(n, wait, m->m_type);
1341 if (m->m_flags & M_EXT) {
1342 n->m_flags |= M_EXT;
1343 n->m_ext = m->m_ext;
1344 if (m->m_ext.ext_ref == NULL)
1345 atomic_add_char(&mclrefcnt[mtocl(m->m_ext.ext_buf)], 1);
1349 (*m->m_ext.ext_ref)(m->m_ext.ext_buf,
1353 n->m_data = m->m_data + len;
1355 bcopy(mtod(m, caddr_t) + len, mtod(n, caddr_t), remain);
1359 n->m_next = m->m_next;
1364 * Routine to copy from device local memory into mbufs.
1367 m_devget(buf, totlen, off0, ifp, copy)
1371 void (*copy) __P((char *from, caddr_t to, u_int len));
1373 register struct mbuf *m;
1374 struct mbuf *top = 0, **mp = ⊤
1375 register int off = off0, len;
1382 cp += off + 2 * sizeof(u_short);
1383 totlen -= 2 * sizeof(u_short);
1385 MGETHDR(m, M_DONTWAIT, MT_DATA);
1388 m->m_pkthdr.rcvif = ifp;
1389 m->m_pkthdr.len = totlen;
1392 while (totlen > 0) {
1394 MGET(m, M_DONTWAIT, MT_DATA);
1401 len = min(totlen, epkt - cp);
1402 if (len >= MINCLSIZE) {
1403 MCLGET(m, M_DONTWAIT);
1404 if (m->m_flags & M_EXT)
1405 m->m_len = len = min(len, MCLBYTES);
1410 * Place initial small packet/header at end of mbuf.
1412 if (len < m->m_len) {
1413 if (top == 0 && len + max_linkhdr <= m->m_len)
1414 m->m_data += max_linkhdr;
1420 copy(cp, mtod(m, caddr_t), (unsigned)len);
1422 bcopy(cp, mtod(m, caddr_t), (unsigned)len);
1434 * Copy data from a buffer back into the indicated mbuf chain,
1435 * starting "off" bytes from the beginning, extending the mbuf
1436 * chain if necessary.
1439 m_copyback(m0, off, len, cp)
1446 register struct mbuf *m = m0, *n;
1451 while (off > (mlen = m->m_len)) {
1454 if (m->m_next == 0) {
1455 n = m_getclr(M_DONTWAIT, m->m_type);
1458 n->m_len = min(MLEN, len + off);
1464 mlen = min (m->m_len - off, len);
1465 bcopy(cp, off + mtod(m, caddr_t), (unsigned)mlen);
1473 if (m->m_next == 0) {
1474 n = m_get(M_DONTWAIT, m->m_type);
1477 n->m_len = min(MLEN, len);
1482 out: if (((m = m0)->m_flags & M_PKTHDR) && (m->m_pkthdr.len < totlen))
1483 m->m_pkthdr.len = totlen;
1487 m_print(const struct mbuf *m)
1490 const struct mbuf *m2;
1492 len = m->m_pkthdr.len;
1495 printf("%p %*D\n", m2, m2->m_len, (u_char *)m2->m_data, "-");
1503 * "Move" mbuf pkthdr from "from" to "to".
1504 * "from" must have M_PKTHDR set, and "to" must be empty.
1507 m_move_pkthdr(struct mbuf *to, struct mbuf *from)
1509 KASSERT((to->m_flags & M_EXT) == 0, ("m_move_pkthdr: to has cluster"));
1511 to->m_flags = from->m_flags & M_COPYFLAGS;
1512 to->m_data = to->m_pktdat;
1513 to->m_pkthdr = from->m_pkthdr; /* especially tags */
1514 SLIST_INIT(&from->m_pkthdr.tags); /* purge tags from src */
1515 from->m_flags &= ~M_PKTHDR;
1519 * Duplicate "from"'s mbuf pkthdr in "to".
1520 * "from" must have M_PKTHDR set, and "to" must be empty.
1521 * In particular, this does a deep copy of the packet tags.
1524 m_dup_pkthdr(struct mbuf *to, struct mbuf *from, int how)
1526 to->m_flags = (from->m_flags & M_COPYFLAGS) | (to->m_flags & M_EXT);
1527 if ((to->m_flags & M_EXT) == 0)
1528 to->m_data = to->m_pktdat;
1529 to->m_pkthdr = from->m_pkthdr;
1530 SLIST_INIT(&to->m_pkthdr.tags);
1531 return (m_tag_copy_chain(to, from, how));
1535 * Defragment a mbuf chain, returning the shortest possible
1536 * chain of mbufs and clusters. If allocation fails and
1537 * this cannot be completed, NULL will be returned, but
1538 * the passed in chain will be unchanged. Upon success,
1539 * the original chain will be freed, and the new chain
1542 * If a non-packet header is passed in, the original
1543 * mbuf (chain?) will be returned unharmed.
1546 m_defrag(struct mbuf *m0, int how)
1548 struct mbuf *m_new = NULL, *m_final = NULL;
1549 int progress = 0, length;
1551 if (!(m0->m_flags & M_PKTHDR))
1554 #ifdef MBUF_STRESS_TEST
1555 if (m_defragrandomfailures) {
1556 int temp = arc4random() & 0xff;
1562 if (m0->m_pkthdr.len > MHLEN)
1563 m_final = m_getcl(how, MT_DATA, M_PKTHDR);
1565 m_final = m_gethdr(how, MT_DATA);
1567 if (m_final == NULL)
1570 if (m_dup_pkthdr(m_final, m0, how) == NULL)
1575 while (progress < m0->m_pkthdr.len) {
1576 length = m0->m_pkthdr.len - progress;
1577 if (length > MCLBYTES)
1580 if (m_new == NULL) {
1582 m_new = m_getcl(how, MT_DATA, 0);
1584 m_new = m_get(how, MT_DATA);
1589 m_copydata(m0, progress, length, mtod(m_new, caddr_t));
1591 m_new->m_len = length;
1592 if (m_new != m_final)
1593 m_cat(m_final, m_new);
1596 if (m0->m_next == NULL)
1601 m_defragbytes += m0->m_pkthdr.len;