The Design and Implementation of the FreeBSD Operating System, Second Edition
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FreeBSD/Linux Kernel Cross Reference
sys/kern/uipc_mbuf.c

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    1 /*
    2  * (MPSAFE)
    3  *
    4  * Copyright (c) 2004 Jeffrey M. Hsu.  All rights reserved.
    5  * Copyright (c) 2004 The DragonFly Project.  All rights reserved.
    6  * 
    7  * This code is derived from software contributed to The DragonFly Project
    8  * by Jeffrey M. Hsu.
    9  * 
   10  * Redistribution and use in source and binary forms, with or without
   11  * modification, are permitted provided that the following conditions
   12  * are met:
   13  * 1. Redistributions of source code must retain the above copyright
   14  *    notice, this list of conditions and the following disclaimer.
   15  * 2. Redistributions in binary form must reproduce the above copyright
   16  *    notice, this list of conditions and the following disclaimer in the
   17  *    documentation and/or other materials provided with the distribution.
   18  * 3. Neither the name of The DragonFly Project nor the names of its
   19  *    contributors may be used to endorse or promote products derived
   20  *    from this software without specific, prior written permission.
   21  * 
   22  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   23  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
   24  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
   25  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
   26  * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
   27  * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
   28  * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
   29  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
   30  * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
   31  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
   32  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   33  * SUCH DAMAGE.
   34  */
   35 
   36 /*
   37  * Copyright (c) 1982, 1986, 1988, 1991, 1993
   38  *      The Regents of the University of California.  All rights reserved.
   39  *
   40  * Redistribution and use in source and binary forms, with or without
   41  * modification, are permitted provided that the following conditions
   42  * are met:
   43  * 1. Redistributions of source code must retain the above copyright
   44  *    notice, this list of conditions and the following disclaimer.
   45  * 2. Redistributions in binary form must reproduce the above copyright
   46  *    notice, this list of conditions and the following disclaimer in the
   47  *    documentation and/or other materials provided with the distribution.
   48  * 3. Neither the name of the University nor the names of its contributors
   49  *    may be used to endorse or promote products derived from this software
   50  *    without specific prior written permission.
   51  *
   52  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   53  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   54  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   55  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   56  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   57  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   58  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   59  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   60  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   61  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   62  * SUCH DAMAGE.
   63  *
   64  * @(#)uipc_mbuf.c      8.2 (Berkeley) 1/4/94
   65  * $FreeBSD: src/sys/kern/uipc_mbuf.c,v 1.51.2.24 2003/04/15 06:59:29 silby Exp $
   66  */
   67 
   68 #include "opt_param.h"
   69 #include "opt_mbuf_stress_test.h"
   70 #include <sys/param.h>
   71 #include <sys/systm.h>
   72 #include <sys/file.h>
   73 #include <sys/malloc.h>
   74 #include <sys/mbuf.h>
   75 #include <sys/kernel.h>
   76 #include <sys/sysctl.h>
   77 #include <sys/domain.h>
   78 #include <sys/objcache.h>
   79 #include <sys/tree.h>
   80 #include <sys/protosw.h>
   81 #include <sys/uio.h>
   82 #include <sys/thread.h>
   83 #include <sys/globaldata.h>
   84 
   85 #include <sys/thread2.h>
   86 #include <sys/spinlock2.h>
   87 
   88 #include <machine/atomic.h>
   89 #include <machine/limits.h>
   90 
   91 #include <vm/vm.h>
   92 #include <vm/vm_kern.h>
   93 #include <vm/vm_extern.h>
   94 
   95 #ifdef INVARIANTS
   96 #include <machine/cpu.h>
   97 #endif
   98 
   99 /*
  100  * mbuf cluster meta-data
  101  */
  102 struct mbcluster {
  103         int32_t mcl_refs;
  104         void    *mcl_data;
  105 };
  106 
  107 /*
  108  * mbuf tracking for debugging purposes
  109  */
  110 #ifdef MBUF_DEBUG
  111 
  112 static MALLOC_DEFINE(M_MTRACK, "mtrack", "mtrack");
  113 
  114 struct mbctrack;
  115 RB_HEAD(mbuf_rb_tree, mbtrack);
  116 RB_PROTOTYPE2(mbuf_rb_tree, mbtrack, rb_node, mbtrack_cmp, struct mbuf *);
  117 
  118 struct mbtrack {
  119         RB_ENTRY(mbtrack) rb_node;
  120         int trackid;
  121         struct mbuf *m;
  122 };
  123 
  124 static int
  125 mbtrack_cmp(struct mbtrack *mb1, struct mbtrack *mb2)
  126 {
  127         if (mb1->m < mb2->m)
  128                 return(-1);
  129         if (mb1->m > mb2->m)
  130                 return(1);
  131         return(0);
  132 }
  133 
  134 RB_GENERATE2(mbuf_rb_tree, mbtrack, rb_node, mbtrack_cmp, struct mbuf *, m);
  135 
  136 struct mbuf_rb_tree     mbuf_track_root;
  137 static struct spinlock  mbuf_track_spin = SPINLOCK_INITIALIZER(mbuf_track_spin);
  138 
  139 static void
  140 mbuftrack(struct mbuf *m)
  141 {
  142         struct mbtrack *mbt;
  143 
  144         mbt = kmalloc(sizeof(*mbt), M_MTRACK, M_INTWAIT|M_ZERO);
  145         spin_lock(&mbuf_track_spin);
  146         mbt->m = m;
  147         if (mbuf_rb_tree_RB_INSERT(&mbuf_track_root, mbt)) {
  148                 spin_unlock(&mbuf_track_spin);
  149                 panic("mbuftrack: mbuf %p already being tracked", m);
  150         }
  151         spin_unlock(&mbuf_track_spin);
  152 }
  153 
  154 static void
  155 mbufuntrack(struct mbuf *m)
  156 {
  157         struct mbtrack *mbt;
  158 
  159         spin_lock(&mbuf_track_spin);
  160         mbt = mbuf_rb_tree_RB_LOOKUP(&mbuf_track_root, m);
  161         if (mbt == NULL) {
  162                 spin_unlock(&mbuf_track_spin);
  163                 panic("mbufuntrack: mbuf %p was not tracked", m);
  164         } else {
  165                 mbuf_rb_tree_RB_REMOVE(&mbuf_track_root, mbt);
  166                 spin_unlock(&mbuf_track_spin);
  167                 kfree(mbt, M_MTRACK);
  168         }
  169 }
  170 
  171 void
  172 mbuftrackid(struct mbuf *m, int trackid)
  173 {
  174         struct mbtrack *mbt;
  175         struct mbuf *n;
  176 
  177         spin_lock(&mbuf_track_spin);
  178         while (m) { 
  179                 n = m->m_nextpkt;
  180                 while (m) {
  181                         mbt = mbuf_rb_tree_RB_LOOKUP(&mbuf_track_root, m);
  182                         if (mbt == NULL) {
  183                                 spin_unlock(&mbuf_track_spin);
  184                                 panic("mbuftrackid: mbuf %p not tracked", m);
  185                         }
  186                         mbt->trackid = trackid;
  187                         m = m->m_next;
  188                 }
  189                 m = n;
  190         }
  191         spin_unlock(&mbuf_track_spin);
  192 }
  193 
  194 static int
  195 mbuftrack_callback(struct mbtrack *mbt, void *arg)
  196 {
  197         struct sysctl_req *req = arg;
  198         char buf[64];
  199         int error;
  200 
  201         ksnprintf(buf, sizeof(buf), "mbuf %p track %d\n", mbt->m, mbt->trackid);
  202 
  203         spin_unlock(&mbuf_track_spin);
  204         error = SYSCTL_OUT(req, buf, strlen(buf));
  205         spin_lock(&mbuf_track_spin);
  206         if (error)      
  207                 return(-error);
  208         return(0);
  209 }
  210 
  211 static int
  212 mbuftrack_show(SYSCTL_HANDLER_ARGS)
  213 {
  214         int error;
  215 
  216         spin_lock(&mbuf_track_spin);
  217         error = mbuf_rb_tree_RB_SCAN(&mbuf_track_root, NULL,
  218                                      mbuftrack_callback, req);
  219         spin_unlock(&mbuf_track_spin);
  220         return (-error);
  221 }
  222 SYSCTL_PROC(_kern_ipc, OID_AUTO, showmbufs, CTLFLAG_RD|CTLTYPE_STRING,
  223             0, 0, mbuftrack_show, "A", "Show all in-use mbufs");
  224 
  225 #else
  226 
  227 #define mbuftrack(m)
  228 #define mbufuntrack(m)
  229 
  230 #endif
  231 
  232 static void mbinit(void *);
  233 SYSINIT(mbuf, SI_BOOT2_MACHDEP, SI_ORDER_FIRST, mbinit, NULL)
  234 
  235 struct mbtypes_stat {
  236         u_long  stats[MT_NTYPES];
  237 } __cachealign;
  238 
  239 static struct mbtypes_stat      mbtypes[SMP_MAXCPU];
  240 
  241 static struct mbstat mbstat[SMP_MAXCPU] __cachealign;
  242 int     max_linkhdr;
  243 int     max_protohdr;
  244 int     max_hdr;
  245 int     max_datalen;
  246 int     m_defragpackets;
  247 int     m_defragbytes;
  248 int     m_defraguseless;
  249 int     m_defragfailure;
  250 #ifdef MBUF_STRESS_TEST
  251 int     m_defragrandomfailures;
  252 #endif
  253 
  254 struct objcache *mbuf_cache, *mbufphdr_cache;
  255 struct objcache *mclmeta_cache, *mjclmeta_cache;
  256 struct objcache *mbufcluster_cache, *mbufphdrcluster_cache;
  257 struct objcache *mbufjcluster_cache, *mbufphdrjcluster_cache;
  258 
  259 int             nmbclusters;
  260 static int      nmbjclusters;
  261 int             nmbufs;
  262 
  263 static int      mclph_cachefrac;
  264 static int      mcl_cachefrac;
  265 
  266 SYSCTL_INT(_kern_ipc, KIPC_MAX_LINKHDR, max_linkhdr, CTLFLAG_RW,
  267         &max_linkhdr, 0, "Max size of a link-level header");
  268 SYSCTL_INT(_kern_ipc, KIPC_MAX_PROTOHDR, max_protohdr, CTLFLAG_RW,
  269         &max_protohdr, 0, "Max size of a protocol header");
  270 SYSCTL_INT(_kern_ipc, KIPC_MAX_HDR, max_hdr, CTLFLAG_RW, &max_hdr, 0,
  271         "Max size of link+protocol headers");
  272 SYSCTL_INT(_kern_ipc, KIPC_MAX_DATALEN, max_datalen, CTLFLAG_RW,
  273         &max_datalen, 0, "Max data payload size without headers");
  274 SYSCTL_INT(_kern_ipc, OID_AUTO, mbuf_wait, CTLFLAG_RW,
  275         &mbuf_wait, 0, "Time in ticks to sleep after failed mbuf allocations");
  276 static int do_mbstat(SYSCTL_HANDLER_ARGS);
  277 
  278 SYSCTL_PROC(_kern_ipc, KIPC_MBSTAT, mbstat, CTLTYPE_STRUCT|CTLFLAG_RD,
  279         0, 0, do_mbstat, "S,mbstat", "mbuf usage statistics");
  280 
  281 static int do_mbtypes(SYSCTL_HANDLER_ARGS);
  282 
  283 SYSCTL_PROC(_kern_ipc, OID_AUTO, mbtypes, CTLTYPE_ULONG|CTLFLAG_RD,
  284         0, 0, do_mbtypes, "LU", "");
  285 
  286 static int
  287 do_mbstat(SYSCTL_HANDLER_ARGS)
  288 {
  289         struct mbstat mbstat_total;
  290         struct mbstat *mbstat_totalp;
  291         int i;
  292 
  293         bzero(&mbstat_total, sizeof(mbstat_total));
  294         mbstat_totalp = &mbstat_total;
  295 
  296         for (i = 0; i < ncpus; i++)
  297         {
  298                 mbstat_total.m_mbufs += mbstat[i].m_mbufs;      
  299                 mbstat_total.m_clusters += mbstat[i].m_clusters;        
  300                 mbstat_total.m_jclusters += mbstat[i].m_jclusters;      
  301                 mbstat_total.m_clfree += mbstat[i].m_clfree;    
  302                 mbstat_total.m_drops += mbstat[i].m_drops;      
  303                 mbstat_total.m_wait += mbstat[i].m_wait;        
  304                 mbstat_total.m_drain += mbstat[i].m_drain;      
  305                 mbstat_total.m_mcfail += mbstat[i].m_mcfail;    
  306                 mbstat_total.m_mpfail += mbstat[i].m_mpfail;    
  307 
  308         }
  309         /*
  310          * The following fields are not cumulative fields so just
  311          * get their values once.
  312          */
  313         mbstat_total.m_msize = mbstat[0].m_msize;       
  314         mbstat_total.m_mclbytes = mbstat[0].m_mclbytes; 
  315         mbstat_total.m_minclsize = mbstat[0].m_minclsize;       
  316         mbstat_total.m_mlen = mbstat[0].m_mlen; 
  317         mbstat_total.m_mhlen = mbstat[0].m_mhlen;       
  318 
  319         return(sysctl_handle_opaque(oidp, mbstat_totalp, sizeof(mbstat_total), req));
  320 }
  321 
  322 static int
  323 do_mbtypes(SYSCTL_HANDLER_ARGS)
  324 {
  325         u_long totals[MT_NTYPES];
  326         int i, j;
  327 
  328         for (i = 0; i < MT_NTYPES; i++)
  329                 totals[i] = 0;
  330 
  331         for (i = 0; i < ncpus; i++)
  332         {
  333                 for (j = 0; j < MT_NTYPES; j++)
  334                         totals[j] += mbtypes[i].stats[j];
  335         }
  336 
  337         return(sysctl_handle_opaque(oidp, totals, sizeof(totals), req));
  338 }
  339 
  340 /*
  341  * These are read-only because we do not currently have any code
  342  * to adjust the objcache limits after the fact.  The variables
  343  * may only be set as boot-time tunables.
  344  */
  345 SYSCTL_INT(_kern_ipc, KIPC_NMBCLUSTERS, nmbclusters, CTLFLAG_RD,
  346            &nmbclusters, 0, "Maximum number of mbuf clusters available");
  347 SYSCTL_INT(_kern_ipc, OID_AUTO, nmbufs, CTLFLAG_RD, &nmbufs, 0,
  348            "Maximum number of mbufs available");
  349 SYSCTL_INT(_kern_ipc, OID_AUTO, nmbjclusters, CTLFLAG_RD, &nmbjclusters, 0,
  350            "Maximum number of mbuf jclusters available");
  351 SYSCTL_INT(_kern_ipc, OID_AUTO, mclph_cachefrac, CTLFLAG_RD,
  352            &mclph_cachefrac, 0,
  353            "Fraction of cacheable mbuf clusters w/ pkthdr");
  354 SYSCTL_INT(_kern_ipc, OID_AUTO, mcl_cachefrac, CTLFLAG_RD,
  355            &mcl_cachefrac, 0, "Fraction of cacheable mbuf clusters");
  356 
  357 SYSCTL_INT(_kern_ipc, OID_AUTO, m_defragpackets, CTLFLAG_RD,
  358            &m_defragpackets, 0, "Number of defragment packets");
  359 SYSCTL_INT(_kern_ipc, OID_AUTO, m_defragbytes, CTLFLAG_RD,
  360            &m_defragbytes, 0, "Number of defragment bytes");
  361 SYSCTL_INT(_kern_ipc, OID_AUTO, m_defraguseless, CTLFLAG_RD,
  362            &m_defraguseless, 0, "Number of useless defragment mbuf chain operations");
  363 SYSCTL_INT(_kern_ipc, OID_AUTO, m_defragfailure, CTLFLAG_RD,
  364            &m_defragfailure, 0, "Number of failed defragment mbuf chain operations");
  365 #ifdef MBUF_STRESS_TEST
  366 SYSCTL_INT(_kern_ipc, OID_AUTO, m_defragrandomfailures, CTLFLAG_RW,
  367            &m_defragrandomfailures, 0, "");
  368 #endif
  369 
  370 static MALLOC_DEFINE(M_MBUF, "mbuf", "mbuf");
  371 static MALLOC_DEFINE(M_MBUFCL, "mbufcl", "mbufcl");
  372 static MALLOC_DEFINE(M_MCLMETA, "mclmeta", "mclmeta");
  373 
  374 static void m_reclaim (void);
  375 static void m_mclref(void *arg);
  376 static void m_mclfree(void *arg);
  377 static void m_mjclfree(void *arg);
  378 
  379 /*
  380  * NOTE: Default NMBUFS must take into account a possible DOS attack
  381  *       using fd passing on unix domain sockets.
  382  */
  383 #ifndef NMBCLUSTERS
  384 #define NMBCLUSTERS     (512 + maxusers * 16)
  385 #endif
  386 #ifndef MCLPH_CACHEFRAC
  387 #define MCLPH_CACHEFRAC 16
  388 #endif
  389 #ifndef MCL_CACHEFRAC
  390 #define MCL_CACHEFRAC   4
  391 #endif
  392 #ifndef NMBJCLUSTERS
  393 #define NMBJCLUSTERS    (NMBCLUSTERS / 2)
  394 #endif
  395 #ifndef NMBUFS
  396 #define NMBUFS          (nmbclusters * 2 + maxfiles)
  397 #endif
  398 
  399 /*
  400  * Perform sanity checks of tunables declared above.
  401  */
  402 static void
  403 tunable_mbinit(void *dummy)
  404 {
  405         /*
  406          * This has to be done before VM init.
  407          */
  408         nmbclusters = NMBCLUSTERS;
  409         TUNABLE_INT_FETCH("kern.ipc.nmbclusters", &nmbclusters);
  410         mclph_cachefrac = MCLPH_CACHEFRAC;
  411         TUNABLE_INT_FETCH("kern.ipc.mclph_cachefrac", &mclph_cachefrac);
  412         mcl_cachefrac = MCL_CACHEFRAC;
  413         TUNABLE_INT_FETCH("kern.ipc.mcl_cachefrac", &mcl_cachefrac);
  414 
  415         nmbjclusters = NMBJCLUSTERS;
  416         TUNABLE_INT_FETCH("kern.ipc.nmbjclusters", &nmbjclusters);
  417 
  418         nmbufs = NMBUFS;
  419         TUNABLE_INT_FETCH("kern.ipc.nmbufs", &nmbufs);
  420 
  421         /* Sanity checks */
  422         if (nmbufs < nmbclusters * 2)
  423                 nmbufs = nmbclusters * 2;
  424 }
  425 SYSINIT(tunable_mbinit, SI_BOOT1_TUNABLES, SI_ORDER_ANY,
  426         tunable_mbinit, NULL);
  427 
  428 /* "number of clusters of pages" */
  429 #define NCL_INIT        1
  430 
  431 #define NMB_INIT        16
  432 
  433 /*
  434  * The mbuf object cache only guarantees that m_next and m_nextpkt are
  435  * NULL and that m_data points to the beginning of the data area.  In
  436  * particular, m_len and m_pkthdr.len are uninitialized.  It is the
  437  * responsibility of the caller to initialize those fields before use.
  438  */
  439 
  440 static __inline boolean_t
  441 mbuf_ctor(void *obj, void *private, int ocflags)
  442 {
  443         struct mbuf *m = obj;
  444 
  445         m->m_next = NULL;
  446         m->m_nextpkt = NULL;
  447         m->m_data = m->m_dat;
  448         m->m_flags = 0;
  449 
  450         return (TRUE);
  451 }
  452 
  453 /*
  454  * Initialize the mbuf and the packet header fields.
  455  */
  456 static boolean_t
  457 mbufphdr_ctor(void *obj, void *private, int ocflags)
  458 {
  459         struct mbuf *m = obj;
  460 
  461         m->m_next = NULL;
  462         m->m_nextpkt = NULL;
  463         m->m_data = m->m_pktdat;
  464         m->m_flags = M_PKTHDR | M_PHCACHE;
  465 
  466         m->m_pkthdr.rcvif = NULL;       /* eliminate XXX JH */
  467         SLIST_INIT(&m->m_pkthdr.tags);
  468         m->m_pkthdr.csum_flags = 0;     /* eliminate XXX JH */
  469         m->m_pkthdr.fw_flags = 0;       /* eliminate XXX JH */
  470 
  471         return (TRUE);
  472 }
  473 
  474 /*
  475  * A mbcluster object consists of 2K (MCLBYTES) cluster and a refcount.
  476  */
  477 static boolean_t
  478 mclmeta_ctor(void *obj, void *private, int ocflags)
  479 {
  480         struct mbcluster *cl = obj;
  481         void *buf;
  482 
  483         if (ocflags & M_NOWAIT)
  484                 buf = kmalloc(MCLBYTES, M_MBUFCL, M_NOWAIT | M_ZERO);
  485         else
  486                 buf = kmalloc(MCLBYTES, M_MBUFCL, M_INTWAIT | M_ZERO);
  487         if (buf == NULL)
  488                 return (FALSE);
  489         cl->mcl_refs = 0;
  490         cl->mcl_data = buf;
  491         return (TRUE);
  492 }
  493 
  494 static boolean_t
  495 mjclmeta_ctor(void *obj, void *private, int ocflags)
  496 {
  497         struct mbcluster *cl = obj;
  498         void *buf;
  499 
  500         if (ocflags & M_NOWAIT)
  501                 buf = kmalloc(MJUMPAGESIZE, M_MBUFCL, M_NOWAIT | M_ZERO);
  502         else
  503                 buf = kmalloc(MJUMPAGESIZE, M_MBUFCL, M_INTWAIT | M_ZERO);
  504         if (buf == NULL)
  505                 return (FALSE);
  506         cl->mcl_refs = 0;
  507         cl->mcl_data = buf;
  508         return (TRUE);
  509 }
  510 
  511 static void
  512 mclmeta_dtor(void *obj, void *private)
  513 {
  514         struct mbcluster *mcl = obj;
  515 
  516         KKASSERT(mcl->mcl_refs == 0);
  517         kfree(mcl->mcl_data, M_MBUFCL);
  518 }
  519 
  520 static void
  521 linkjcluster(struct mbuf *m, struct mbcluster *cl, uint size)
  522 {
  523         /*
  524          * Add the cluster to the mbuf.  The caller will detect that the
  525          * mbuf now has an attached cluster.
  526          */
  527         m->m_ext.ext_arg = cl;
  528         m->m_ext.ext_buf = cl->mcl_data;
  529         m->m_ext.ext_ref = m_mclref;
  530         if (size != MCLBYTES)
  531                 m->m_ext.ext_free = m_mjclfree;
  532         else
  533                 m->m_ext.ext_free = m_mclfree;
  534         m->m_ext.ext_size = size;
  535         atomic_add_int(&cl->mcl_refs, 1);
  536 
  537         m->m_data = m->m_ext.ext_buf;
  538         m->m_flags |= M_EXT | M_EXT_CLUSTER;
  539 }
  540 
  541 static void
  542 linkcluster(struct mbuf *m, struct mbcluster *cl)
  543 {
  544         linkjcluster(m, cl, MCLBYTES);
  545 }
  546 
  547 static boolean_t
  548 mbufphdrcluster_ctor(void *obj, void *private, int ocflags)
  549 {
  550         struct mbuf *m = obj;
  551         struct mbcluster *cl;
  552 
  553         mbufphdr_ctor(obj, private, ocflags);
  554         cl = objcache_get(mclmeta_cache, ocflags);
  555         if (cl == NULL) {
  556                 ++mbstat[mycpu->gd_cpuid].m_drops;
  557                 return (FALSE);
  558         }
  559         m->m_flags |= M_CLCACHE;
  560         linkcluster(m, cl);
  561         return (TRUE);
  562 }
  563 
  564 static boolean_t
  565 mbufphdrjcluster_ctor(void *obj, void *private, int ocflags)
  566 {
  567         struct mbuf *m = obj;
  568         struct mbcluster *cl;
  569 
  570         mbufphdr_ctor(obj, private, ocflags);
  571         cl = objcache_get(mjclmeta_cache, ocflags);
  572         if (cl == NULL) {
  573                 ++mbstat[mycpu->gd_cpuid].m_drops;
  574                 return (FALSE);
  575         }
  576         m->m_flags |= M_CLCACHE;
  577         linkjcluster(m, cl, MJUMPAGESIZE);
  578         return (TRUE);
  579 }
  580 
  581 static boolean_t
  582 mbufcluster_ctor(void *obj, void *private, int ocflags)
  583 {
  584         struct mbuf *m = obj;
  585         struct mbcluster *cl;
  586 
  587         mbuf_ctor(obj, private, ocflags);
  588         cl = objcache_get(mclmeta_cache, ocflags);
  589         if (cl == NULL) {
  590                 ++mbstat[mycpu->gd_cpuid].m_drops;
  591                 return (FALSE);
  592         }
  593         m->m_flags |= M_CLCACHE;
  594         linkcluster(m, cl);
  595         return (TRUE);
  596 }
  597 
  598 static boolean_t
  599 mbufjcluster_ctor(void *obj, void *private, int ocflags)
  600 {
  601         struct mbuf *m = obj;
  602         struct mbcluster *cl;
  603 
  604         mbuf_ctor(obj, private, ocflags);
  605         cl = objcache_get(mjclmeta_cache, ocflags);
  606         if (cl == NULL) {
  607                 ++mbstat[mycpu->gd_cpuid].m_drops;
  608                 return (FALSE);
  609         }
  610         m->m_flags |= M_CLCACHE;
  611         linkjcluster(m, cl, MJUMPAGESIZE);
  612         return (TRUE);
  613 }
  614 
  615 /*
  616  * Used for both the cluster and cluster PHDR caches.
  617  *
  618  * The mbuf may have lost its cluster due to sharing, deal
  619  * with the situation by checking M_EXT.
  620  */
  621 static void
  622 mbufcluster_dtor(void *obj, void *private)
  623 {
  624         struct mbuf *m = obj;
  625         struct mbcluster *mcl;
  626 
  627         if (m->m_flags & M_EXT) {
  628                 KKASSERT((m->m_flags & M_EXT_CLUSTER) != 0);
  629                 mcl = m->m_ext.ext_arg;
  630                 KKASSERT(mcl->mcl_refs == 1);
  631                 mcl->mcl_refs = 0;
  632                 if (m->m_flags & M_EXT && m->m_ext.ext_size != MCLBYTES)
  633                         objcache_put(mjclmeta_cache, mcl);
  634                 else
  635                         objcache_put(mclmeta_cache, mcl);
  636         }
  637 }
  638 
  639 struct objcache_malloc_args mbuf_malloc_args = { MSIZE, M_MBUF };
  640 struct objcache_malloc_args mclmeta_malloc_args =
  641         { sizeof(struct mbcluster), M_MCLMETA };
  642 
  643 /* ARGSUSED*/
  644 static void
  645 mbinit(void *dummy)
  646 {
  647         int mb_limit, cl_limit, ncl_limit, jcl_limit;
  648         int limit;
  649         int i;
  650 
  651         /*
  652          * Initialize statistics
  653          */
  654         for (i = 0; i < ncpus; i++) {
  655                 mbstat[i].m_msize = MSIZE;
  656                 mbstat[i].m_mclbytes = MCLBYTES;
  657                 mbstat[i].m_mjumpagesize = MJUMPAGESIZE;
  658                 mbstat[i].m_minclsize = MINCLSIZE;
  659                 mbstat[i].m_mlen = MLEN;
  660                 mbstat[i].m_mhlen = MHLEN;
  661         }
  662 
  663         /*
  664          * Create objtect caches and save cluster limits, which will
  665          * be used to adjust backing kmalloc pools' limit later.
  666          */
  667 
  668         mb_limit = cl_limit = 0;
  669 
  670         limit = nmbufs;
  671         mbuf_cache = objcache_create("mbuf",
  672             limit, 0,
  673             mbuf_ctor, NULL, NULL,
  674             objcache_malloc_alloc, objcache_malloc_free, &mbuf_malloc_args);
  675         mb_limit += limit;
  676 
  677         limit = nmbufs;
  678         mbufphdr_cache = objcache_create("mbuf pkt hdr",
  679             limit, nmbufs / 4,
  680             mbufphdr_ctor, NULL, NULL,
  681             objcache_malloc_alloc, objcache_malloc_free, &mbuf_malloc_args);
  682         mb_limit += limit;
  683 
  684         ncl_limit = nmbclusters;
  685         mclmeta_cache = objcache_create("cluster mbuf",
  686             ncl_limit, 0,
  687             mclmeta_ctor, mclmeta_dtor, NULL,
  688             objcache_malloc_alloc, objcache_malloc_free, &mclmeta_malloc_args);
  689         cl_limit += ncl_limit;
  690 
  691         jcl_limit = nmbjclusters;
  692         mjclmeta_cache = objcache_create("jcluster mbuf",
  693             jcl_limit, 0,
  694             mjclmeta_ctor, mclmeta_dtor, NULL,
  695             objcache_malloc_alloc, objcache_malloc_free, &mclmeta_malloc_args);
  696         cl_limit += jcl_limit;
  697 
  698         limit = nmbclusters;
  699         mbufcluster_cache = objcache_create("mbuf + cluster",
  700             limit, nmbclusters / mcl_cachefrac,
  701             mbufcluster_ctor, mbufcluster_dtor, NULL,
  702             objcache_malloc_alloc, objcache_malloc_free, &mbuf_malloc_args);
  703         mb_limit += limit;
  704 
  705         limit = nmbclusters;
  706         mbufphdrcluster_cache = objcache_create("mbuf pkt hdr + cluster",
  707             limit, nmbclusters / mclph_cachefrac,
  708             mbufphdrcluster_ctor, mbufcluster_dtor, NULL,
  709             objcache_malloc_alloc, objcache_malloc_free, &mbuf_malloc_args);
  710         mb_limit += limit;
  711 
  712         limit = nmbjclusters;
  713         mbufjcluster_cache = objcache_create("mbuf + jcluster",
  714             limit, 0,
  715             mbufjcluster_ctor, mbufcluster_dtor, NULL,
  716             objcache_malloc_alloc, objcache_malloc_free, &mbuf_malloc_args);
  717         mb_limit += limit;
  718 
  719         limit = nmbjclusters;
  720         mbufphdrjcluster_cache = objcache_create("mbuf pkt hdr + jcluster",
  721             limit, 0,
  722             mbufphdrjcluster_ctor, mbufcluster_dtor, NULL,
  723             objcache_malloc_alloc, objcache_malloc_free, &mbuf_malloc_args);
  724         mb_limit += limit;
  725 
  726         /*
  727          * Adjust backing kmalloc pools' limit
  728          *
  729          * NOTE: We raise the limit by another 1/8 to take the effect
  730          * of loosememuse into account.
  731          */
  732         cl_limit += cl_limit / 8;
  733         kmalloc_raise_limit(mclmeta_malloc_args.mtype,
  734             mclmeta_malloc_args.objsize * (size_t)cl_limit);
  735         kmalloc_raise_limit(M_MBUFCL,
  736             (MCLBYTES * (size_t)ncl_limit) +
  737             (MJUMPAGESIZE * (size_t)jcl_limit));
  738 
  739         mb_limit += mb_limit / 8;
  740         kmalloc_raise_limit(mbuf_malloc_args.mtype,
  741             mbuf_malloc_args.objsize * (size_t)mb_limit);
  742 }
  743 
  744 /*
  745  * Return the number of references to this mbuf's data.  0 is returned
  746  * if the mbuf is not M_EXT, a reference count is returned if it is
  747  * M_EXT | M_EXT_CLUSTER, and 99 is returned if it is a special M_EXT.
  748  */
  749 int
  750 m_sharecount(struct mbuf *m)
  751 {
  752         switch (m->m_flags & (M_EXT | M_EXT_CLUSTER)) {
  753         case 0:
  754                 return (0);
  755         case M_EXT:
  756                 return (99);
  757         case M_EXT | M_EXT_CLUSTER:
  758                 return (((struct mbcluster *)m->m_ext.ext_arg)->mcl_refs);
  759         }
  760         /* NOTREACHED */
  761         return (0);             /* to shut up compiler */
  762 }
  763 
  764 /*
  765  * change mbuf to new type
  766  */
  767 void
  768 m_chtype(struct mbuf *m, int type)
  769 {
  770         struct globaldata *gd = mycpu;
  771 
  772         ++mbtypes[gd->gd_cpuid].stats[type];
  773         --mbtypes[gd->gd_cpuid].stats[m->m_type];
  774         m->m_type = type;
  775 }
  776 
  777 static void
  778 m_reclaim(void)
  779 {
  780         struct domain *dp;
  781         struct protosw *pr;
  782 
  783         kprintf("Debug: m_reclaim() called\n");
  784 
  785         SLIST_FOREACH(dp, &domains, dom_next) {
  786                 for (pr = dp->dom_protosw; pr < dp->dom_protoswNPROTOSW; pr++) {
  787                         if (pr->pr_drain)
  788                                 (*pr->pr_drain)();
  789                 }
  790         }
  791         ++mbstat[mycpu->gd_cpuid].m_drain;
  792 }
  793 
  794 static __inline void
  795 updatestats(struct mbuf *m, int type)
  796 {
  797         struct globaldata *gd = mycpu;
  798 
  799         m->m_type = type;
  800         mbuftrack(m);
  801 #ifdef MBUF_DEBUG
  802         KASSERT(m->m_next == NULL, ("mbuf %p: bad m_next in get", m));
  803         KASSERT(m->m_nextpkt == NULL, ("mbuf %p: bad m_nextpkt in get", m));
  804 #endif
  805 
  806         ++mbtypes[gd->gd_cpuid].stats[type];
  807         ++mbstat[gd->gd_cpuid].m_mbufs;
  808 
  809 }
  810 
  811 /*
  812  * Allocate an mbuf.
  813  */
  814 struct mbuf *
  815 m_get(int how, int type)
  816 {
  817         struct mbuf *m;
  818         int ntries = 0;
  819         int ocf = MBTOM(how);
  820 
  821 retryonce:
  822 
  823         m = objcache_get(mbuf_cache, ocf);
  824 
  825         if (m == NULL) {
  826                 if ((how & MB_TRYWAIT) && ntries++ == 0) {
  827                         struct objcache *reclaimlist[] = {
  828                                 mbufphdr_cache,
  829                                 mbufcluster_cache,
  830                                 mbufphdrcluster_cache,
  831                                 mbufjcluster_cache,
  832                                 mbufphdrjcluster_cache
  833                         };
  834                         const int nreclaims = NELEM(reclaimlist);
  835 
  836                         if (!objcache_reclaimlist(reclaimlist, nreclaims, ocf))
  837                                 m_reclaim();
  838                         goto retryonce;
  839                 }
  840                 ++mbstat[mycpu->gd_cpuid].m_drops;
  841                 return (NULL);
  842         }
  843 #ifdef MBUF_DEBUG
  844         KASSERT(m->m_data == m->m_dat, ("mbuf %p: bad m_data in get", m));
  845 #endif
  846         m->m_len = 0;
  847 
  848         updatestats(m, type);
  849         return (m);
  850 }
  851 
  852 struct mbuf *
  853 m_gethdr(int how, int type)
  854 {
  855         struct mbuf *m;
  856         int ocf = MBTOM(how);
  857         int ntries = 0;
  858 
  859 retryonce:
  860 
  861         m = objcache_get(mbufphdr_cache, ocf);
  862 
  863         if (m == NULL) {
  864                 if ((how & MB_TRYWAIT) && ntries++ == 0) {
  865                         struct objcache *reclaimlist[] = {
  866                                 mbuf_cache,
  867                                 mbufcluster_cache, mbufphdrcluster_cache,
  868                                 mbufjcluster_cache, mbufphdrjcluster_cache
  869                         };
  870                         const int nreclaims = NELEM(reclaimlist);
  871 
  872                         if (!objcache_reclaimlist(reclaimlist, nreclaims, ocf))
  873                                 m_reclaim();
  874                         goto retryonce;
  875                 }
  876                 ++mbstat[mycpu->gd_cpuid].m_drops;
  877                 return (NULL);
  878         }
  879 #ifdef MBUF_DEBUG
  880         KASSERT(m->m_data == m->m_pktdat, ("mbuf %p: bad m_data in get", m));
  881 #endif
  882         m->m_len = 0;
  883         m->m_pkthdr.len = 0;
  884 
  885         updatestats(m, type);
  886         return (m);
  887 }
  888 
  889 /*
  890  * Get a mbuf (not a mbuf cluster!) and zero it.
  891  * Deprecated.
  892  */
  893 struct mbuf *
  894 m_getclr(int how, int type)
  895 {
  896         struct mbuf *m;
  897 
  898         m = m_get(how, type);
  899         if (m != NULL)
  900                 bzero(m->m_data, MLEN);
  901         return (m);
  902 }
  903 
  904 static struct mbuf *
  905 m_getcl_cache(int how, short type, int flags, struct objcache *mbclc,
  906     struct objcache *mbphclc, u_long *cl_stats)
  907 {
  908         struct mbuf *m = NULL;
  909         int ocflags = MBTOM(how);
  910         int ntries = 0;
  911 
  912 retryonce:
  913 
  914         if (flags & M_PKTHDR)
  915                 m = objcache_get(mbphclc, ocflags);
  916         else
  917                 m = objcache_get(mbclc, ocflags);
  918 
  919         if (m == NULL) {
  920                 if ((how & MB_TRYWAIT) && ntries++ == 0) {
  921                         struct objcache *reclaimlist[1];
  922 
  923                         if (flags & M_PKTHDR)
  924                                 reclaimlist[0] = mbclc;
  925                         else
  926                                 reclaimlist[0] = mbphclc;
  927                         if (!objcache_reclaimlist(reclaimlist, 1, ocflags))
  928                                 m_reclaim();
  929                         goto retryonce;
  930                 }
  931                 ++mbstat[mycpu->gd_cpuid].m_drops;
  932                 return (NULL);
  933         }
  934 
  935 #ifdef MBUF_DEBUG
  936         KASSERT(m->m_data == m->m_ext.ext_buf,
  937                 ("mbuf %p: bad m_data in get", m));
  938 #endif
  939         m->m_type = type;
  940         m->m_len = 0;
  941         m->m_pkthdr.len = 0;    /* just do it unconditonally */
  942 
  943         mbuftrack(m);
  944 
  945         ++mbtypes[mycpu->gd_cpuid].stats[type];
  946         ++(*cl_stats);
  947         return (m);
  948 }
  949 
  950 struct mbuf *
  951 m_getjcl(int how, short type, int flags, size_t size)
  952 {
  953         struct objcache *mbclc, *mbphclc;
  954         u_long *cl_stats;
  955 
  956         switch (size) {
  957         case MCLBYTES:
  958                 mbclc = mbufcluster_cache;
  959                 mbphclc = mbufphdrcluster_cache;
  960                 cl_stats = &mbstat[mycpu->gd_cpuid].m_clusters;
  961                 break;
  962 
  963         default:
  964                 mbclc = mbufjcluster_cache;
  965                 mbphclc = mbufphdrjcluster_cache;
  966                 cl_stats = &mbstat[mycpu->gd_cpuid].m_jclusters;
  967                 break;
  968         }
  969         return m_getcl_cache(how, type, flags, mbclc, mbphclc, cl_stats);
  970 }
  971 
  972 /*
  973  * Returns an mbuf with an attached cluster.
  974  * Because many network drivers use this kind of buffers a lot, it is
  975  * convenient to keep a small pool of free buffers of this kind.
  976  * Even a small size such as 10 gives about 10% improvement in the
  977  * forwarding rate in a bridge or router.
  978  */
  979 struct mbuf *
  980 m_getcl(int how, short type, int flags)
  981 {
  982         return m_getcl_cache(how, type, flags,
  983             mbufcluster_cache, mbufphdrcluster_cache,
  984             &mbstat[mycpu->gd_cpuid].m_clusters);
  985 }
  986 
  987 /*
  988  * Allocate chain of requested length.
  989  */
  990 struct mbuf *
  991 m_getc(int len, int how, int type)
  992 {
  993         struct mbuf *n, *nfirst = NULL, **ntail = &nfirst;
  994         int nsize;
  995 
  996         while (len > 0) {
  997                 n = m_getl(len, how, type, 0, &nsize);
  998                 if (n == NULL)
  999                         goto failed;
 1000                 n->m_len = 0;
 1001                 *ntail = n;
 1002                 ntail = &n->m_next;
 1003                 len -= nsize;
 1004         }
 1005         return (nfirst);
 1006 
 1007 failed:
 1008         m_freem(nfirst);
 1009         return (NULL);
 1010 }
 1011 
 1012 /*
 1013  * Allocate len-worth of mbufs and/or mbuf clusters (whatever fits best)
 1014  * and return a pointer to the head of the allocated chain. If m0 is
 1015  * non-null, then we assume that it is a single mbuf or an mbuf chain to
 1016  * which we want len bytes worth of mbufs and/or clusters attached, and so
 1017  * if we succeed in allocating it, we will just return a pointer to m0.
 1018  *
 1019  * If we happen to fail at any point during the allocation, we will free
 1020  * up everything we have already allocated and return NULL.
 1021  *
 1022  * Deprecated.  Use m_getc() and m_cat() instead.
 1023  */
 1024 struct mbuf *
 1025 m_getm(struct mbuf *m0, int len, int type, int how)
 1026 {
 1027         struct mbuf *nfirst;
 1028 
 1029         nfirst = m_getc(len, how, type);
 1030 
 1031         if (m0 != NULL) {
 1032                 m_last(m0)->m_next = nfirst;
 1033                 return (m0);
 1034         }
 1035 
 1036         return (nfirst);
 1037 }
 1038 
 1039 /*
 1040  * Adds a cluster to a normal mbuf, M_EXT is set on success.
 1041  * Deprecated.  Use m_getcl() instead.
 1042  */
 1043 void
 1044 m_mclget(struct mbuf *m, int how)
 1045 {
 1046         struct mbcluster *mcl;
 1047 
 1048         KKASSERT((m->m_flags & M_EXT) == 0);
 1049         mcl = objcache_get(mclmeta_cache, MBTOM(how));
 1050         if (mcl != NULL) {
 1051                 linkcluster(m, mcl);
 1052                 ++mbstat[mycpu->gd_cpuid].m_clusters;
 1053         } else {
 1054                 ++mbstat[mycpu->gd_cpuid].m_drops;
 1055         }
 1056 }
 1057 
 1058 /*
 1059  * Updates to mbcluster must be MPSAFE.  Only an entity which already has
 1060  * a reference to the cluster can ref it, so we are in no danger of 
 1061  * racing an add with a subtract.  But the operation must still be atomic
 1062  * since multiple entities may have a reference on the cluster.
 1063  *
 1064  * m_mclfree() is almost the same but it must contend with two entities
 1065  * freeing the cluster at the same time.
 1066  */
 1067 static void
 1068 m_mclref(void *arg)
 1069 {
 1070         struct mbcluster *mcl = arg;
 1071 
 1072         atomic_add_int(&mcl->mcl_refs, 1);
 1073 }
 1074 
 1075 /*
 1076  * When dereferencing a cluster we have to deal with a N->0 race, where
 1077  * N entities free their references simultaniously.  To do this we use
 1078  * atomic_fetchadd_int().
 1079  */
 1080 static void
 1081 m_mclfree(void *arg)
 1082 {
 1083         struct mbcluster *mcl = arg;
 1084 
 1085         if (atomic_fetchadd_int(&mcl->mcl_refs, -1) == 1) {
 1086                 --mbstat[mycpu->gd_cpuid].m_clusters;
 1087                 objcache_put(mclmeta_cache, mcl);
 1088         }
 1089 }
 1090 
 1091 static void
 1092 m_mjclfree(void *arg)
 1093 {
 1094         struct mbcluster *mcl = arg;
 1095 
 1096         if (atomic_fetchadd_int(&mcl->mcl_refs, -1) == 1) {
 1097                 --mbstat[mycpu->gd_cpuid].m_jclusters;
 1098                 objcache_put(mjclmeta_cache, mcl);
 1099         }
 1100 }
 1101 
 1102 /*
 1103  * Free a single mbuf and any associated external storage.  The successor,
 1104  * if any, is returned.
 1105  *
 1106  * We do need to check non-first mbuf for m_aux, since some of existing
 1107  * code does not call M_PREPEND properly.
 1108  * (example: call to bpf_mtap from drivers)
 1109  */
 1110 
 1111 #ifdef MBUF_DEBUG
 1112 
 1113 struct mbuf  *
 1114 _m_free(struct mbuf *m, const char *func)
 1115 
 1116 #else
 1117 
 1118 struct mbuf *
 1119 m_free(struct mbuf *m)
 1120 
 1121 #endif
 1122 {
 1123         struct mbuf *n;
 1124         struct globaldata *gd = mycpu;
 1125 
 1126         KASSERT(m->m_type != MT_FREE, ("freeing free mbuf %p", m));
 1127         KASSERT(M_TRAILINGSPACE(m) >= 0, ("overflowed mbuf %p", m));
 1128         --mbtypes[gd->gd_cpuid].stats[m->m_type];
 1129 
 1130         n = m->m_next;
 1131 
 1132         /*
 1133          * Make sure the mbuf is in constructed state before returning it
 1134          * to the objcache.
 1135          */
 1136         m->m_next = NULL;
 1137         mbufuntrack(m);
 1138 #ifdef MBUF_DEBUG
 1139         m->m_hdr.mh_lastfunc = func;
 1140 #endif
 1141 #ifdef notyet
 1142         KKASSERT(m->m_nextpkt == NULL);
 1143 #else
 1144         if (m->m_nextpkt != NULL) {
 1145                 static int afewtimes = 10;
 1146 
 1147                 if (afewtimes-- > 0) {
 1148                         kprintf("mfree: m->m_nextpkt != NULL\n");
 1149                         print_backtrace(-1);
 1150                 }
 1151                 m->m_nextpkt = NULL;
 1152         }
 1153 #endif
 1154         if (m->m_flags & M_PKTHDR) {
 1155                 m_tag_delete_chain(m);          /* eliminate XXX JH */
 1156         }
 1157 
 1158         m->m_flags &= (M_EXT | M_EXT_CLUSTER | M_CLCACHE | M_PHCACHE);
 1159 
 1160         /*
 1161          * Clean the M_PKTHDR state so we can return the mbuf to its original
 1162          * cache.  This is based on the PHCACHE flag which tells us whether
 1163          * the mbuf was originally allocated out of a packet-header cache
 1164          * or a non-packet-header cache.
 1165          */
 1166         if (m->m_flags & M_PHCACHE) {
 1167                 m->m_flags |= M_PKTHDR;
 1168                 m->m_pkthdr.rcvif = NULL;       /* eliminate XXX JH */
 1169                 m->m_pkthdr.csum_flags = 0;     /* eliminate XXX JH */
 1170                 m->m_pkthdr.fw_flags = 0;       /* eliminate XXX JH */
 1171                 SLIST_INIT(&m->m_pkthdr.tags);
 1172         }
 1173 
 1174         /*
 1175          * Handle remaining flags combinations.  M_CLCACHE tells us whether
 1176          * the mbuf was originally allocated from a cluster cache or not,
 1177          * and is totally separate from whether the mbuf is currently
 1178          * associated with a cluster.
 1179          */
 1180         switch(m->m_flags & (M_CLCACHE | M_EXT | M_EXT_CLUSTER)) {
 1181         case M_CLCACHE | M_EXT | M_EXT_CLUSTER:
 1182                 /*
 1183                  * mbuf+cluster cache case.  The mbuf was allocated from the
 1184                  * combined mbuf_cluster cache and can be returned to the
 1185                  * cache if the cluster hasn't been shared.
 1186                  */
 1187                 if (m_sharecount(m) == 1) {
 1188                         /*
 1189                          * The cluster has not been shared, we can just
 1190                          * reset the data pointer and return the mbuf
 1191                          * to the cluster cache.  Note that the reference
 1192                          * count is left intact (it is still associated with
 1193                          * an mbuf).
 1194                          */
 1195                         m->m_data = m->m_ext.ext_buf;
 1196                         if (m->m_flags & M_EXT && m->m_ext.ext_size != MCLBYTES) {
 1197                                 if (m->m_flags & M_PHCACHE)
 1198                                         objcache_put(mbufphdrjcluster_cache, m);
 1199                                 else
 1200                                         objcache_put(mbufjcluster_cache, m);
 1201                                 --mbstat[mycpu->gd_cpuid].m_jclusters;
 1202                         } else {
 1203                                 if (m->m_flags & M_PHCACHE)
 1204                                         objcache_put(mbufphdrcluster_cache, m);
 1205                                 else
 1206                                         objcache_put(mbufcluster_cache, m);
 1207                                 --mbstat[mycpu->gd_cpuid].m_clusters;
 1208                         }
 1209                 } else {
 1210                         /*
 1211                          * Hell.  Someone else has a ref on this cluster,
 1212                          * we have to disconnect it which means we can't
 1213                          * put it back into the mbufcluster_cache, we
 1214                          * have to destroy the mbuf.
 1215                          *
 1216                          * Other mbuf references to the cluster will typically
 1217                          * be M_EXT | M_EXT_CLUSTER but without M_CLCACHE.
 1218                          *
 1219                          * XXX we could try to connect another cluster to
 1220                          * it.
 1221                          */
 1222                         m->m_ext.ext_free(m->m_ext.ext_arg); 
 1223                         m->m_flags &= ~(M_EXT | M_EXT_CLUSTER);
 1224                         if (m->m_ext.ext_size == MCLBYTES) {
 1225                                 if (m->m_flags & M_PHCACHE)
 1226                                         objcache_dtor(mbufphdrcluster_cache, m);
 1227                                 else
 1228                                         objcache_dtor(mbufcluster_cache, m);
 1229                         } else {
 1230                                 if (m->m_flags & M_PHCACHE)
 1231                                         objcache_dtor(mbufphdrjcluster_cache, m);
 1232                                 else
 1233                                         objcache_dtor(mbufjcluster_cache, m);
 1234                         }
 1235                 }
 1236                 break;
 1237         case M_EXT | M_EXT_CLUSTER:
 1238         case M_EXT:
 1239                 /*
 1240                  * Normal cluster association case, disconnect the cluster from
 1241                  * the mbuf.  The cluster may or may not be custom.
 1242                  */
 1243                 m->m_ext.ext_free(m->m_ext.ext_arg); 
 1244                 m->m_flags &= ~(M_EXT | M_EXT_CLUSTER);
 1245                 /* fall through */
 1246         case 0:
 1247                 /*
 1248                  * return the mbuf to the mbuf cache.
 1249                  */
 1250                 if (m->m_flags & M_PHCACHE) {
 1251                         m->m_data = m->m_pktdat;
 1252                         objcache_put(mbufphdr_cache, m);
 1253                 } else {
 1254                         m->m_data = m->m_dat;
 1255                         objcache_put(mbuf_cache, m);
 1256                 }
 1257                 --mbstat[mycpu->gd_cpuid].m_mbufs;
 1258                 break;
 1259         default:
 1260                 if (!panicstr)
 1261                         panic("bad mbuf flags %p %08x", m, m->m_flags);
 1262                 break;
 1263         }
 1264         return (n);
 1265 }
 1266 
 1267 #ifdef MBUF_DEBUG
 1268 
 1269 void
 1270 _m_freem(struct mbuf *m, const char *func)
 1271 {
 1272         while (m)
 1273                 m = _m_free(m, func);
 1274 }
 1275 
 1276 #else
 1277 
 1278 void
 1279 m_freem(struct mbuf *m)
 1280 {
 1281         while (m)
 1282                 m = m_free(m);
 1283 }
 1284 
 1285 #endif
 1286 
 1287 void
 1288 m_extadd(struct mbuf *m, caddr_t buf, u_int size,  void (*reff)(void *),
 1289     void (*freef)(void *), void *arg)
 1290 {
 1291         m->m_ext.ext_arg = arg;
 1292         m->m_ext.ext_buf = buf;
 1293         m->m_ext.ext_ref = reff;
 1294         m->m_ext.ext_free = freef;
 1295         m->m_ext.ext_size = size;
 1296         reff(arg);
 1297         m->m_data = buf;
 1298         m->m_flags |= M_EXT;
 1299 }
 1300 
 1301 /*
 1302  * mbuf utility routines
 1303  */
 1304 
 1305 /*
 1306  * Lesser-used path for M_PREPEND: allocate new mbuf to prepend to chain and
 1307  * copy junk along.
 1308  */
 1309 struct mbuf *
 1310 m_prepend(struct mbuf *m, int len, int how)
 1311 {
 1312         struct mbuf *mn;
 1313 
 1314         if (m->m_flags & M_PKTHDR)
 1315             mn = m_gethdr(how, m->m_type);
 1316         else
 1317             mn = m_get(how, m->m_type);
 1318         if (mn == NULL) {
 1319                 m_freem(m);
 1320                 return (NULL);
 1321         }
 1322         if (m->m_flags & M_PKTHDR)
 1323                 M_MOVE_PKTHDR(mn, m);
 1324         mn->m_next = m;
 1325         m = mn;
 1326         if (len < MHLEN)
 1327                 MH_ALIGN(m, len);
 1328         m->m_len = len;
 1329         return (m);
 1330 }
 1331 
 1332 /*
 1333  * Make a copy of an mbuf chain starting "off0" bytes from the beginning,
 1334  * continuing for "len" bytes.  If len is M_COPYALL, copy to end of mbuf.
 1335  * The wait parameter is a choice of MB_WAIT/MB_DONTWAIT from caller.
 1336  * Note that the copy is read-only, because clusters are not copied,
 1337  * only their reference counts are incremented.
 1338  */
 1339 struct mbuf *
 1340 m_copym(const struct mbuf *m, int off0, int len, int wait)
 1341 {
 1342         struct mbuf *n, **np;
 1343         int off = off0;
 1344         struct mbuf *top;
 1345         int copyhdr = 0;
 1346 
 1347         KASSERT(off >= 0, ("m_copym, negative off %d", off));
 1348         KASSERT(len >= 0, ("m_copym, negative len %d", len));
 1349         if (off == 0 && (m->m_flags & M_PKTHDR))
 1350                 copyhdr = 1;
 1351         while (off > 0) {
 1352                 KASSERT(m != NULL, ("m_copym, offset > size of mbuf chain"));
 1353                 if (off < m->m_len)
 1354                         break;
 1355                 off -= m->m_len;
 1356                 m = m->m_next;
 1357         }
 1358         np = &top;
 1359         top = NULL;
 1360         while (len > 0) {
 1361                 if (m == NULL) {
 1362                         KASSERT(len == M_COPYALL, 
 1363                             ("m_copym, length > size of mbuf chain"));
 1364                         break;
 1365                 }
 1366                 /*
 1367                  * Because we are sharing any cluster attachment below,
 1368                  * be sure to get an mbuf that does not have a cluster
 1369                  * associated with it.
 1370                  */
 1371                 if (copyhdr)
 1372                         n = m_gethdr(wait, m->m_type);
 1373                 else
 1374                         n = m_get(wait, m->m_type);
 1375                 *np = n;
 1376                 if (n == NULL)
 1377                         goto nospace;
 1378                 if (copyhdr) {
 1379                         if (!m_dup_pkthdr(n, m, wait))
 1380                                 goto nospace;
 1381                         if (len == M_COPYALL)
 1382                                 n->m_pkthdr.len -= off0;
 1383                         else
 1384                                 n->m_pkthdr.len = len;
 1385                         copyhdr = 0;
 1386                 }
 1387                 n->m_len = min(len, m->m_len - off);
 1388                 if (m->m_flags & M_EXT) {
 1389                         KKASSERT((n->m_flags & M_EXT) == 0);
 1390                         n->m_data = m->m_data + off;
 1391                         m->m_ext.ext_ref(m->m_ext.ext_arg); 
 1392                         n->m_ext = m->m_ext;
 1393                         n->m_flags |= m->m_flags & (M_EXT | M_EXT_CLUSTER);
 1394                 } else {
 1395                         bcopy(mtod(m, caddr_t)+off, mtod(n, caddr_t),
 1396                             (unsigned)n->m_len);
 1397                 }
 1398                 if (len != M_COPYALL)
 1399                         len -= n->m_len;
 1400                 off = 0;
 1401                 m = m->m_next;
 1402                 np = &n->m_next;
 1403         }
 1404         if (top == NULL)
 1405                 ++mbstat[mycpu->gd_cpuid].m_mcfail;
 1406         return (top);
 1407 nospace:
 1408         m_freem(top);
 1409         ++mbstat[mycpu->gd_cpuid].m_mcfail;
 1410         return (NULL);
 1411 }
 1412 
 1413 /*
 1414  * Copy an entire packet, including header (which must be present).
 1415  * An optimization of the common case `m_copym(m, 0, M_COPYALL, how)'.
 1416  * Note that the copy is read-only, because clusters are not copied,
 1417  * only their reference counts are incremented.
 1418  * Preserve alignment of the first mbuf so if the creator has left
 1419  * some room at the beginning (e.g. for inserting protocol headers)
 1420  * the copies also have the room available.
 1421  */
 1422 struct mbuf *
 1423 m_copypacket(struct mbuf *m, int how)
 1424 {
 1425         struct mbuf *top, *n, *o;
 1426 
 1427         n = m_gethdr(how, m->m_type);
 1428         top = n;
 1429         if (!n)
 1430                 goto nospace;
 1431 
 1432         if (!m_dup_pkthdr(n, m, how))
 1433                 goto nospace;
 1434         n->m_len = m->m_len;
 1435         if (m->m_flags & M_EXT) {
 1436                 KKASSERT((n->m_flags & M_EXT) == 0);
 1437                 n->m_data = m->m_data;
 1438                 m->m_ext.ext_ref(m->m_ext.ext_arg); 
 1439                 n->m_ext = m->m_ext;
 1440                 n->m_flags |= m->m_flags & (M_EXT | M_EXT_CLUSTER);
 1441         } else {
 1442                 n->m_data = n->m_pktdat + (m->m_data - m->m_pktdat );
 1443                 bcopy(mtod(m, char *), mtod(n, char *), n->m_len);
 1444         }
 1445 
 1446         m = m->m_next;
 1447         while (m) {
 1448                 o = m_get(how, m->m_type);
 1449                 if (!o)
 1450                         goto nospace;
 1451 
 1452                 n->m_next = o;
 1453                 n = n->m_next;
 1454 
 1455                 n->m_len = m->m_len;
 1456                 if (m->m_flags & M_EXT) {
 1457                         KKASSERT((n->m_flags & M_EXT) == 0);
 1458                         n->m_data = m->m_data;
 1459                         m->m_ext.ext_ref(m->m_ext.ext_arg); 
 1460                         n->m_ext = m->m_ext;
 1461                         n->m_flags |= m->m_flags & (M_EXT | M_EXT_CLUSTER);
 1462                 } else {
 1463                         bcopy(mtod(m, char *), mtod(n, char *), n->m_len);
 1464                 }
 1465 
 1466                 m = m->m_next;
 1467         }
 1468         return top;
 1469 nospace:
 1470         m_freem(top);
 1471         ++mbstat[mycpu->gd_cpuid].m_mcfail;
 1472         return (NULL);
 1473 }
 1474 
 1475 /*
 1476  * Copy data from an mbuf chain starting "off" bytes from the beginning,
 1477  * continuing for "len" bytes, into the indicated buffer.
 1478  */
 1479 void
 1480 m_copydata(const struct mbuf *m, int off, int len, caddr_t cp)
 1481 {
 1482         unsigned count;
 1483 
 1484         KASSERT(off >= 0, ("m_copydata, negative off %d", off));
 1485         KASSERT(len >= 0, ("m_copydata, negative len %d", len));
 1486         while (off > 0) {
 1487                 KASSERT(m != NULL, ("m_copydata, offset > size of mbuf chain"));
 1488                 if (off < m->m_len)
 1489                         break;
 1490                 off -= m->m_len;
 1491                 m = m->m_next;
 1492         }
 1493         while (len > 0) {
 1494                 KASSERT(m != NULL, ("m_copydata, length > size of mbuf chain"));
 1495                 count = min(m->m_len - off, len);
 1496                 bcopy(mtod(m, caddr_t) + off, cp, count);
 1497                 len -= count;
 1498                 cp += count;
 1499                 off = 0;
 1500                 m = m->m_next;
 1501         }
 1502 }
 1503 
 1504 /*
 1505  * Copy a packet header mbuf chain into a completely new chain, including
 1506  * copying any mbuf clusters.  Use this instead of m_copypacket() when
 1507  * you need a writable copy of an mbuf chain.
 1508  */
 1509 struct mbuf *
 1510 m_dup(struct mbuf *m, int how)
 1511 {
 1512         struct mbuf **p, *top = NULL;
 1513         int remain, moff, nsize;
 1514 
 1515         /* Sanity check */
 1516         if (m == NULL)
 1517                 return (NULL);
 1518         KASSERT((m->m_flags & M_PKTHDR) != 0, ("%s: !PKTHDR", __func__));
 1519 
 1520         /* While there's more data, get a new mbuf, tack it on, and fill it */
 1521         remain = m->m_pkthdr.len;
 1522         moff = 0;
 1523         p = &top;
 1524         while (remain > 0 || top == NULL) {     /* allow m->m_pkthdr.len == 0 */
 1525                 struct mbuf *n;
 1526 
 1527                 /* Get the next new mbuf */
 1528                 n = m_getl(remain, how, m->m_type, top == NULL ? M_PKTHDR : 0,
 1529                            &nsize);
 1530                 if (n == NULL)
 1531                         goto nospace;
 1532                 if (top == NULL)
 1533                         if (!m_dup_pkthdr(n, m, how))
 1534                                 goto nospace0;
 1535 
 1536                 /* Link it into the new chain */
 1537                 *p = n;
 1538                 p = &n->m_next;
 1539 
 1540                 /* Copy data from original mbuf(s) into new mbuf */
 1541                 n->m_len = 0;
 1542                 while (n->m_len < nsize && m != NULL) {
 1543                         int chunk = min(nsize - n->m_len, m->m_len - moff);
 1544 
 1545                         bcopy(m->m_data + moff, n->m_data + n->m_len, chunk);
 1546                         moff += chunk;
 1547                         n->m_len += chunk;
 1548                         remain -= chunk;
 1549                         if (moff == m->m_len) {
 1550                                 m = m->m_next;
 1551                                 moff = 0;
 1552                         }
 1553                 }
 1554 
 1555                 /* Check correct total mbuf length */
 1556                 KASSERT((remain > 0 && m != NULL) || (remain == 0 && m == NULL),
 1557                         ("%s: bogus m_pkthdr.len", __func__));
 1558         }
 1559         return (top);
 1560 
 1561 nospace:
 1562         m_freem(top);
 1563 nospace0:
 1564         ++mbstat[mycpu->gd_cpuid].m_mcfail;
 1565         return (NULL);
 1566 }
 1567 
 1568 /*
 1569  * Copy the non-packet mbuf data chain into a new set of mbufs, including
 1570  * copying any mbuf clusters.  This is typically used to realign a data
 1571  * chain by nfs_realign().
 1572  *
 1573  * The original chain is left intact.  how should be MB_WAIT or MB_DONTWAIT
 1574  * and NULL can be returned if MB_DONTWAIT is passed.
 1575  *
 1576  * Be careful to use cluster mbufs, a large mbuf chain converted to non
 1577  * cluster mbufs can exhaust our supply of mbufs.
 1578  */
 1579 struct mbuf *
 1580 m_dup_data(struct mbuf *m, int how)
 1581 {
 1582         struct mbuf **p, *n, *top = NULL;
 1583         int mlen, moff, chunk, gsize, nsize;
 1584 
 1585         /*
 1586          * Degenerate case
 1587          */
 1588         if (m == NULL)
 1589                 return (NULL);
 1590 
 1591         /*
 1592          * Optimize the mbuf allocation but do not get too carried away.
 1593          */
 1594         if (m->m_next || m->m_len > MLEN)
 1595                 if (m->m_flags & M_EXT && m->m_ext.ext_size == MCLBYTES)
 1596                         gsize = MCLBYTES;
 1597                 else
 1598                         gsize = MJUMPAGESIZE;
 1599         else
 1600                 gsize = MLEN;
 1601 
 1602         /* Chain control */
 1603         p = &top;
 1604         n = NULL;
 1605         nsize = 0;
 1606 
 1607         /*
 1608          * Scan the mbuf chain until nothing is left, the new mbuf chain
 1609          * will be allocated on the fly as needed.
 1610          */
 1611         while (m) {
 1612                 mlen = m->m_len;
 1613                 moff = 0;
 1614 
 1615                 while (mlen) {
 1616                         KKASSERT(m->m_type == MT_DATA);
 1617                         if (n == NULL) {
 1618                                 n = m_getl(gsize, how, MT_DATA, 0, &nsize);
 1619                                 n->m_len = 0;
 1620                                 if (n == NULL)
 1621                                         goto nospace;
 1622                                 *p = n;
 1623                                 p = &n->m_next;
 1624                         }
 1625                         chunk = imin(mlen, nsize);
 1626                         bcopy(m->m_data + moff, n->m_data + n->m_len, chunk);
 1627                         mlen -= chunk;
 1628                         moff += chunk;
 1629                         n->m_len += chunk;
 1630                         nsize -= chunk;
 1631                         if (nsize == 0)
 1632                                 n = NULL;
 1633                 }
 1634                 m = m->m_next;
 1635         }
 1636         *p = NULL;
 1637         return(top);
 1638 nospace:
 1639         *p = NULL;
 1640         m_freem(top);
 1641         ++mbstat[mycpu->gd_cpuid].m_mcfail;
 1642         return (NULL);
 1643 }
 1644 
 1645 /*
 1646  * Concatenate mbuf chain n to m.
 1647  * Both chains must be of the same type (e.g. MT_DATA).
 1648  * Any m_pkthdr is not updated.
 1649  */
 1650 void
 1651 m_cat(struct mbuf *m, struct mbuf *n)
 1652 {
 1653         m = m_last(m);
 1654         while (n) {
 1655                 if (m->m_flags & M_EXT ||
 1656                     m->m_data + m->m_len + n->m_len >= &m->m_dat[MLEN]) {
 1657                         /* just join the two chains */
 1658                         m->m_next = n;
 1659                         return;
 1660                 }
 1661                 /* splat the data from one into the other */
 1662                 bcopy(mtod(n, caddr_t), mtod(m, caddr_t) + m->m_len,
 1663                     (u_int)n->m_len);
 1664                 m->m_len += n->m_len;
 1665                 n = m_free(n);
 1666         }
 1667 }
 1668 
 1669 void
 1670 m_adj(struct mbuf *mp, int req_len)
 1671 {
 1672         int len = req_len;
 1673         struct mbuf *m;
 1674         int count;
 1675 
 1676         if ((m = mp) == NULL)
 1677                 return;
 1678         if (len >= 0) {
 1679                 /*
 1680                  * Trim from head.
 1681                  */
 1682                 while (m != NULL && len > 0) {
 1683                         if (m->m_len <= len) {
 1684                                 len -= m->m_len;
 1685                                 m->m_len = 0;
 1686                                 m = m->m_next;
 1687                         } else {
 1688                                 m->m_len -= len;
 1689                                 m->m_data += len;
 1690                                 len = 0;
 1691                         }
 1692                 }
 1693                 m = mp;
 1694                 if (mp->m_flags & M_PKTHDR)
 1695                         m->m_pkthdr.len -= (req_len - len);
 1696         } else {
 1697                 /*
 1698                  * Trim from tail.  Scan the mbuf chain,
 1699                  * calculating its length and finding the last mbuf.
 1700                  * If the adjustment only affects this mbuf, then just
 1701                  * adjust and return.  Otherwise, rescan and truncate
 1702                  * after the remaining size.
 1703                  */
 1704                 len = -len;
 1705                 count = 0;
 1706                 for (;;) {
 1707                         count += m->m_len;
 1708                         if (m->m_next == NULL)
 1709                                 break;
 1710                         m = m->m_next;
 1711                 }
 1712                 if (m->m_len >= len) {
 1713                         m->m_len -= len;
 1714                         if (mp->m_flags & M_PKTHDR)
 1715                                 mp->m_pkthdr.len -= len;
 1716                         return;
 1717                 }
 1718                 count -= len;
 1719                 if (count < 0)
 1720                         count = 0;
 1721                 /*
 1722                  * Correct length for chain is "count".
 1723                  * Find the mbuf with last data, adjust its length,
 1724                  * and toss data from remaining mbufs on chain.
 1725                  */
 1726                 m = mp;
 1727                 if (m->m_flags & M_PKTHDR)
 1728                         m->m_pkthdr.len = count;
 1729                 for (; m; m = m->m_next) {
 1730                         if (m->m_len >= count) {
 1731                                 m->m_len = count;
 1732                                 break;
 1733                         }
 1734                         count -= m->m_len;
 1735                 }
 1736                 while (m->m_next)
 1737                         (m = m->m_next) ->m_len = 0;
 1738         }
 1739 }
 1740 
 1741 /*
 1742  * Set the m_data pointer of a newly-allocated mbuf
 1743  * to place an object of the specified size at the
 1744  * end of the mbuf, longword aligned.
 1745  */
 1746 void
 1747 m_align(struct mbuf *m, int len)
 1748 {
 1749         int adjust;
 1750 
 1751         if (m->m_flags & M_EXT)
 1752                 adjust = m->m_ext.ext_size - len;
 1753         else if (m->m_flags & M_PKTHDR)
 1754                 adjust = MHLEN - len;
 1755         else
 1756                 adjust = MLEN - len;
 1757         m->m_data += adjust &~ (sizeof(long)-1);
 1758 }
 1759 
 1760 /*
 1761  * Create a writable copy of the mbuf chain.  While doing this
 1762  * we compact the chain with a goal of producing a chain with
 1763  * at most two mbufs.  The second mbuf in this chain is likely
 1764  * to be a cluster.  The primary purpose of this work is to create
 1765  * a writable packet for encryption, compression, etc.  The
 1766  * secondary goal is to linearize the data so the data can be
 1767  * passed to crypto hardware in the most efficient manner possible.
 1768  */
 1769 struct mbuf *
 1770 m_unshare(struct mbuf *m0, int how)
 1771 {
 1772         struct mbuf *m, *mprev;
 1773         struct mbuf *n, *mfirst, *mlast;
 1774         int len, off;
 1775 
 1776         mprev = NULL;
 1777         for (m = m0; m != NULL; m = mprev->m_next) {
 1778                 /*
 1779                  * Regular mbufs are ignored unless there's a cluster
 1780                  * in front of it that we can use to coalesce.  We do
 1781                  * the latter mainly so later clusters can be coalesced
 1782                  * also w/o having to handle them specially (i.e. convert
 1783                  * mbuf+cluster -> cluster).  This optimization is heavily
 1784                  * influenced by the assumption that we're running over
 1785                  * Ethernet where MCLBYTES is large enough that the max
 1786                  * packet size will permit lots of coalescing into a
 1787                  * single cluster.  This in turn permits efficient
 1788                  * crypto operations, especially when using hardware.
 1789                  */
 1790                 if ((m->m_flags & M_EXT) == 0) {
 1791                         if (mprev && (mprev->m_flags & M_EXT) &&
 1792                             m->m_len <= M_TRAILINGSPACE(mprev)) {
 1793                                 /* XXX: this ignores mbuf types */
 1794                                 memcpy(mtod(mprev, caddr_t) + mprev->m_len,
 1795                                        mtod(m, caddr_t), m->m_len);
 1796                                 mprev->m_len += m->m_len;
 1797                                 mprev->m_next = m->m_next;      /* unlink from chain */
 1798                                 m_free(m);                      /* reclaim mbuf */
 1799                         } else {
 1800                                 mprev = m;
 1801                         }
 1802                         continue;
 1803                 }
 1804                 /*
 1805                  * Writable mbufs are left alone (for now).
 1806                  */
 1807                 if (M_WRITABLE(m)) {
 1808                         mprev = m;
 1809                         continue;
 1810                 }
 1811 
 1812                 /*
 1813                  * Not writable, replace with a copy or coalesce with
 1814                  * the previous mbuf if possible (since we have to copy
 1815                  * it anyway, we try to reduce the number of mbufs and
 1816                  * clusters so that future work is easier).
 1817                  */
 1818                 KASSERT(m->m_flags & M_EXT, ("m_flags 0x%x", m->m_flags));
 1819                 /* NB: we only coalesce into a cluster or larger */
 1820                 if (mprev != NULL && (mprev->m_flags & M_EXT) &&
 1821                     m->m_len <= M_TRAILINGSPACE(mprev)) {
 1822                         /* XXX: this ignores mbuf types */
 1823                         memcpy(mtod(mprev, caddr_t) + mprev->m_len,
 1824                                mtod(m, caddr_t), m->m_len);
 1825                         mprev->m_len += m->m_len;
 1826                         mprev->m_next = m->m_next;      /* unlink from chain */
 1827                         m_free(m);                      /* reclaim mbuf */
 1828                         continue;
 1829                 }
 1830 
 1831                 /*
 1832                  * Allocate new space to hold the copy...
 1833                  */
 1834                 /* XXX why can M_PKTHDR be set past the first mbuf? */
 1835                 if (mprev == NULL && (m->m_flags & M_PKTHDR)) {
 1836                         /*
 1837                          * NB: if a packet header is present we must
 1838                          * allocate the mbuf separately from any cluster
 1839                          * because M_MOVE_PKTHDR will smash the data
 1840                          * pointer and drop the M_EXT marker.
 1841                          */
 1842                         MGETHDR(n, how, m->m_type);
 1843                         if (n == NULL) {
 1844                                 m_freem(m0);
 1845                                 return (NULL);
 1846                         }
 1847                         M_MOVE_PKTHDR(n, m);
 1848                         MCLGET(n, how);
 1849                         if ((n->m_flags & M_EXT) == 0) {
 1850                                 m_free(n);
 1851                                 m_freem(m0);
 1852                                 return (NULL);
 1853                         }
 1854                 } else {
 1855                         n = m_getcl(how, m->m_type, m->m_flags);
 1856                         if (n == NULL) {
 1857                                 m_freem(m0);
 1858                                 return (NULL);
 1859                         }
 1860                 }
 1861                 /*
 1862                  * ... and copy the data.  We deal with jumbo mbufs
 1863                  * (i.e. m_len > MCLBYTES) by splitting them into
 1864                  * clusters.  We could just malloc a buffer and make
 1865                  * it external but too many device drivers don't know
 1866                  * how to break up the non-contiguous memory when
 1867                  * doing DMA.
 1868                  */
 1869                 len = m->m_len;
 1870                 off = 0;
 1871                 mfirst = n;
 1872                 mlast = NULL;
 1873                 for (;;) {
 1874                         int cc = min(len, MCLBYTES);
 1875                         memcpy(mtod(n, caddr_t), mtod(m, caddr_t) + off, cc);
 1876                         n->m_len = cc;
 1877                         if (mlast != NULL)
 1878                                 mlast->m_next = n;
 1879                         mlast = n;      
 1880 
 1881                         len -= cc;
 1882                         if (len <= 0)
 1883                                 break;
 1884                         off += cc;
 1885 
 1886                         n = m_getcl(how, m->m_type, m->m_flags);
 1887                         if (n == NULL) {
 1888                                 m_freem(mfirst);
 1889                                 m_freem(m0);
 1890                                 return (NULL);
 1891                         }
 1892                 }
 1893                 n->m_next = m->m_next; 
 1894                 if (mprev == NULL)
 1895                         m0 = mfirst;            /* new head of chain */
 1896                 else
 1897                         mprev->m_next = mfirst; /* replace old mbuf */
 1898                 m_free(m);                      /* release old mbuf */
 1899                 mprev = mfirst;
 1900         }
 1901         return (m0);
 1902 }
 1903 
 1904 /*
 1905  * Rearrange an mbuf chain so that len bytes are contiguous
 1906  * and in the data area of an mbuf (so that mtod will work for a structure
 1907  * of size len).  Returns the resulting mbuf chain on success, frees it and
 1908  * returns null on failure.  If there is room, it will add up to
 1909  * max_protohdr-len extra bytes to the contiguous region in an attempt to
 1910  * avoid being called next time.
 1911  */
 1912 struct mbuf *
 1913 m_pullup(struct mbuf *n, int len)
 1914 {
 1915         struct mbuf *m;
 1916         int count;
 1917         int space;
 1918 
 1919         /*
 1920          * If first mbuf has no cluster, and has room for len bytes
 1921          * without shifting current data, pullup into it,
 1922          * otherwise allocate a new mbuf to prepend to the chain.
 1923          */
 1924         if (!(n->m_flags & M_EXT) &&
 1925             n->m_data + len < &n->m_dat[MLEN] &&
 1926             n->m_next) {
 1927                 if (n->m_len >= len)
 1928                         return (n);
 1929                 m = n;
 1930                 n = n->m_next;
 1931                 len -= m->m_len;
 1932         } else {
 1933                 if (len > MHLEN)
 1934                         goto bad;
 1935                 if (n->m_flags & M_PKTHDR)
 1936                         m = m_gethdr(MB_DONTWAIT, n->m_type);
 1937                 else
 1938                         m = m_get(MB_DONTWAIT, n->m_type);
 1939                 if (m == NULL)
 1940                         goto bad;
 1941                 m->m_len = 0;
 1942                 if (n->m_flags & M_PKTHDR)
 1943                         M_MOVE_PKTHDR(m, n);
 1944         }
 1945         space = &m->m_dat[MLEN] - (m->m_data + m->m_len);
 1946         do {
 1947                 count = min(min(max(len, max_protohdr), space), n->m_len);
 1948                 bcopy(mtod(n, caddr_t), mtod(m, caddr_t) + m->m_len,
 1949                   (unsigned)count);
 1950                 len -= count;
 1951                 m->m_len += count;
 1952                 n->m_len -= count;
 1953                 space -= count;
 1954                 if (n->m_len)
 1955                         n->m_data += count;
 1956                 else
 1957                         n = m_free(n);
 1958         } while (len > 0 && n);
 1959         if (len > 0) {
 1960                 m_free(m);
 1961                 goto bad;
 1962         }
 1963         m->m_next = n;
 1964         return (m);
 1965 bad:
 1966         m_freem(n);
 1967         ++mbstat[mycpu->gd_cpuid].m_mcfail;
 1968         return (NULL);
 1969 }
 1970 
 1971 /*
 1972  * Partition an mbuf chain in two pieces, returning the tail --
 1973  * all but the first len0 bytes.  In case of failure, it returns NULL and
 1974  * attempts to restore the chain to its original state.
 1975  *
 1976  * Note that the resulting mbufs might be read-only, because the new
 1977  * mbuf can end up sharing an mbuf cluster with the original mbuf if
 1978  * the "breaking point" happens to lie within a cluster mbuf. Use the
 1979  * M_WRITABLE() macro to check for this case.
 1980  */
 1981 struct mbuf *
 1982 m_split(struct mbuf *m0, int len0, int wait)
 1983 {
 1984         struct mbuf *m, *n;
 1985         unsigned len = len0, remain;
 1986 
 1987         for (m = m0; m && len > m->m_len; m = m->m_next)
 1988                 len -= m->m_len;
 1989         if (m == NULL)
 1990                 return (NULL);
 1991         remain = m->m_len - len;
 1992         if (m0->m_flags & M_PKTHDR) {
 1993                 n = m_gethdr(wait, m0->m_type);
 1994                 if (n == NULL)
 1995                         return (NULL);
 1996                 n->m_pkthdr.rcvif = m0->m_pkthdr.rcvif;
 1997                 n->m_pkthdr.len = m0->m_pkthdr.len - len0;
 1998                 m0->m_pkthdr.len = len0;
 1999                 if (m->m_flags & M_EXT)
 2000                         goto extpacket;
 2001                 if (remain > MHLEN) {
 2002                         /* m can't be the lead packet */
 2003                         MH_ALIGN(n, 0);
 2004                         n->m_next = m_split(m, len, wait);
 2005                         if (n->m_next == NULL) {
 2006                                 m_free(n);
 2007                                 return (NULL);
 2008                         } else {
 2009                                 n->m_len = 0;
 2010                                 return (n);
 2011                         }
 2012                 } else
 2013                         MH_ALIGN(n, remain);
 2014         } else if (remain == 0) {
 2015                 n = m->m_next;
 2016                 m->m_next = NULL;
 2017                 return (n);
 2018         } else {
 2019                 n = m_get(wait, m->m_type);
 2020                 if (n == NULL)
 2021                         return (NULL);
 2022                 M_ALIGN(n, remain);
 2023         }
 2024 extpacket:
 2025         if (m->m_flags & M_EXT) {
 2026                 KKASSERT((n->m_flags & M_EXT) == 0);
 2027                 n->m_data = m->m_data + len;
 2028                 m->m_ext.ext_ref(m->m_ext.ext_arg); 
 2029                 n->m_ext = m->m_ext;
 2030                 n->m_flags |= m->m_flags & (M_EXT | M_EXT_CLUSTER);
 2031         } else {
 2032                 bcopy(mtod(m, caddr_t) + len, mtod(n, caddr_t), remain);
 2033         }
 2034         n->m_len = remain;
 2035         m->m_len = len;
 2036         n->m_next = m->m_next;
 2037         m->m_next = NULL;
 2038         return (n);
 2039 }
 2040 
 2041 /*
 2042  * Routine to copy from device local memory into mbufs.
 2043  * Note: "offset" is ill-defined and always called as 0, so ignore it.
 2044  */
 2045 struct mbuf *
 2046 m_devget(char *buf, int len, int offset, struct ifnet *ifp,
 2047     void (*copy)(volatile const void *from, volatile void *to, size_t length))
 2048 {
 2049         struct mbuf *m, *mfirst = NULL, **mtail;
 2050         int nsize, flags;
 2051 
 2052         if (copy == NULL)
 2053                 copy = bcopy;
 2054         mtail = &mfirst;
 2055         flags = M_PKTHDR;
 2056 
 2057         while (len > 0) {
 2058                 m = m_getl(len, MB_DONTWAIT, MT_DATA, flags, &nsize);
 2059                 if (m == NULL) {
 2060                         m_freem(mfirst);
 2061                         return (NULL);
 2062                 }
 2063                 m->m_len = min(len, nsize);
 2064 
 2065                 if (flags & M_PKTHDR) {
 2066                         if (len + max_linkhdr <= nsize)
 2067                                 m->m_data += max_linkhdr;
 2068                         m->m_pkthdr.rcvif = ifp;
 2069                         m->m_pkthdr.len = len;
 2070                         flags = 0;
 2071                 }
 2072 
 2073                 copy(buf, m->m_data, (unsigned)m->m_len);
 2074                 buf += m->m_len;
 2075                 len -= m->m_len;
 2076                 *mtail = m;
 2077                 mtail = &m->m_next;
 2078         }
 2079 
 2080         return (mfirst);
 2081 }
 2082 
 2083 /*
 2084  * Routine to pad mbuf to the specified length 'padto'.
 2085  */
 2086 int
 2087 m_devpad(struct mbuf *m, int padto)
 2088 {
 2089         struct mbuf *last = NULL;
 2090         int padlen;
 2091 
 2092         if (padto <= m->m_pkthdr.len)
 2093                 return 0;
 2094 
 2095         padlen = padto - m->m_pkthdr.len;
 2096 
 2097         /* if there's only the packet-header and we can pad there, use it. */
 2098         if (m->m_pkthdr.len == m->m_len && M_TRAILINGSPACE(m) >= padlen) {
 2099                 last = m;
 2100         } else {
 2101                 /*
 2102                  * Walk packet chain to find last mbuf. We will either
 2103                  * pad there, or append a new mbuf and pad it
 2104                  */
 2105                 for (last = m; last->m_next != NULL; last = last->m_next)
 2106                         ; /* EMPTY */
 2107 
 2108                 /* `last' now points to last in chain. */
 2109                 if (M_TRAILINGSPACE(last) < padlen) {
 2110                         struct mbuf *n;
 2111 
 2112                         /* Allocate new empty mbuf, pad it.  Compact later. */
 2113                         MGET(n, MB_DONTWAIT, MT_DATA);
 2114                         if (n == NULL)
 2115                                 return ENOBUFS;
 2116                         n->m_len = 0;
 2117                         last->m_next = n;
 2118                         last = n;
 2119                 }
 2120         }
 2121         KKASSERT(M_TRAILINGSPACE(last) >= padlen);
 2122         KKASSERT(M_WRITABLE(last));
 2123 
 2124         /* Now zero the pad area */
 2125         bzero(mtod(last, char *) + last->m_len, padlen);
 2126         last->m_len += padlen;
 2127         m->m_pkthdr.len += padlen;
 2128         return 0;
 2129 }
 2130 
 2131 /*
 2132  * Copy data from a buffer back into the indicated mbuf chain,
 2133  * starting "off" bytes from the beginning, extending the mbuf
 2134  * chain if necessary.
 2135  */
 2136 void
 2137 m_copyback(struct mbuf *m0, int off, int len, caddr_t cp)
 2138 {
 2139         int mlen;
 2140         struct mbuf *m = m0, *n;
 2141         int totlen = 0;
 2142 
 2143         if (m0 == NULL)
 2144                 return;
 2145         while (off > (mlen = m->m_len)) {
 2146                 off -= mlen;
 2147                 totlen += mlen;
 2148                 if (m->m_next == NULL) {
 2149                         n = m_getclr(MB_DONTWAIT, m->m_type);
 2150                         if (n == NULL)
 2151                                 goto out;
 2152                         n->m_len = min(MLEN, len + off);
 2153                         m->m_next = n;
 2154                 }
 2155                 m = m->m_next;
 2156         }
 2157         while (len > 0) {
 2158                 mlen = min (m->m_len - off, len);
 2159                 bcopy(cp, off + mtod(m, caddr_t), (unsigned)mlen);
 2160                 cp += mlen;
 2161                 len -= mlen;
 2162                 mlen += off;
 2163                 off = 0;
 2164                 totlen += mlen;
 2165                 if (len == 0)
 2166                         break;
 2167                 if (m->m_next == NULL) {
 2168                         n = m_get(MB_DONTWAIT, m->m_type);
 2169                         if (n == NULL)
 2170                                 break;
 2171                         n->m_len = min(MLEN, len);
 2172                         m->m_next = n;
 2173                 }
 2174                 m = m->m_next;
 2175         }
 2176 out:    if (((m = m0)->m_flags & M_PKTHDR) && (m->m_pkthdr.len < totlen))
 2177                 m->m_pkthdr.len = totlen;
 2178 }
 2179 
 2180 /*
 2181  * Append the specified data to the indicated mbuf chain,
 2182  * Extend the mbuf chain if the new data does not fit in
 2183  * existing space.
 2184  *
 2185  * Return 1 if able to complete the job; otherwise 0.
 2186  */
 2187 int
 2188 m_append(struct mbuf *m0, int len, c_caddr_t cp)
 2189 {
 2190         struct mbuf *m, *n;
 2191         int remainder, space;
 2192 
 2193         for (m = m0; m->m_next != NULL; m = m->m_next)
 2194                 ;
 2195         remainder = len;
 2196         space = M_TRAILINGSPACE(m);
 2197         if (space > 0) {
 2198                 /*
 2199                  * Copy into available space.
 2200                  */
 2201                 if (space > remainder)
 2202                         space = remainder;
 2203                 bcopy(cp, mtod(m, caddr_t) + m->m_len, space);
 2204                 m->m_len += space;
 2205                 cp += space, remainder -= space;
 2206         }
 2207         while (remainder > 0) {
 2208                 /*
 2209                  * Allocate a new mbuf; could check space
 2210                  * and allocate a cluster instead.
 2211                  */
 2212                 n = m_get(MB_DONTWAIT, m->m_type);
 2213                 if (n == NULL)
 2214                         break;
 2215                 n->m_len = min(MLEN, remainder);
 2216                 bcopy(cp, mtod(n, caddr_t), n->m_len);
 2217                 cp += n->m_len, remainder -= n->m_len;
 2218                 m->m_next = n;
 2219                 m = n;
 2220         }
 2221         if (m0->m_flags & M_PKTHDR)
 2222                 m0->m_pkthdr.len += len - remainder;
 2223         return (remainder == 0);
 2224 }
 2225 
 2226 /*
 2227  * Apply function f to the data in an mbuf chain starting "off" bytes from
 2228  * the beginning, continuing for "len" bytes.
 2229  */
 2230 int
 2231 m_apply(struct mbuf *m, int off, int len,
 2232     int (*f)(void *, void *, u_int), void *arg)
 2233 {
 2234         u_int count;
 2235         int rval;
 2236 
 2237         KASSERT(off >= 0, ("m_apply, negative off %d", off));
 2238         KASSERT(len >= 0, ("m_apply, negative len %d", len));
 2239         while (off > 0) {
 2240                 KASSERT(m != NULL, ("m_apply, offset > size of mbuf chain"));
 2241                 if (off < m->m_len)
 2242                         break;
 2243                 off -= m->m_len;
 2244                 m = m->m_next;
 2245         }
 2246         while (len > 0) {
 2247                 KASSERT(m != NULL, ("m_apply, offset > size of mbuf chain"));
 2248                 count = min(m->m_len - off, len);
 2249                 rval = (*f)(arg, mtod(m, caddr_t) + off, count);
 2250                 if (rval)
 2251                         return (rval);
 2252                 len -= count;
 2253                 off = 0;
 2254                 m = m->m_next;
 2255         }
 2256         return (0);
 2257 }
 2258 
 2259 /*
 2260  * Return a pointer to mbuf/offset of location in mbuf chain.
 2261  */
 2262 struct mbuf *
 2263 m_getptr(struct mbuf *m, int loc, int *off)
 2264 {
 2265 
 2266         while (loc >= 0) {
 2267                 /* Normal end of search. */
 2268                 if (m->m_len > loc) {
 2269                         *off = loc;
 2270                         return (m);
 2271                 } else {
 2272                         loc -= m->m_len;
 2273                         if (m->m_next == NULL) {
 2274                                 if (loc == 0) {
 2275                                         /* Point at the end of valid data. */
 2276                                         *off = m->m_len;
 2277                                         return (m);
 2278                                 }
 2279                                 return (NULL);
 2280                         }
 2281                         m = m->m_next;
 2282                 }
 2283         }
 2284         return (NULL);
 2285 }
 2286 
 2287 void
 2288 m_print(const struct mbuf *m)
 2289 {
 2290         int len;
 2291         const struct mbuf *m2;
 2292         char *hexstr;
 2293 
 2294         len = m->m_pkthdr.len;
 2295         m2 = m;
 2296         hexstr = kmalloc(HEX_NCPYLEN(len), M_TEMP, M_ZERO | M_WAITOK);
 2297         while (len) {
 2298                 kprintf("%p %s\n", m2, hexncpy(m2->m_data, m2->m_len, hexstr,
 2299                         HEX_NCPYLEN(m2->m_len), "-"));
 2300                 len -= m2->m_len;
 2301                 m2 = m2->m_next;
 2302         }
 2303         kfree(hexstr, M_TEMP);
 2304         return;
 2305 }
 2306 
 2307 /*
 2308  * "Move" mbuf pkthdr from "from" to "to".
 2309  * "from" must have M_PKTHDR set, and "to" must be empty.
 2310  */
 2311 void
 2312 m_move_pkthdr(struct mbuf *to, struct mbuf *from)
 2313 {
 2314         KASSERT((to->m_flags & M_PKTHDR), ("m_move_pkthdr: not packet header"));
 2315 
 2316         to->m_flags |= from->m_flags & M_COPYFLAGS;
 2317         to->m_pkthdr = from->m_pkthdr;          /* especially tags */
 2318         SLIST_INIT(&from->m_pkthdr.tags);       /* purge tags from src */
 2319 }
 2320 
 2321 /*
 2322  * Duplicate "from"'s mbuf pkthdr in "to".
 2323  * "from" must have M_PKTHDR set, and "to" must be empty.
 2324  * In particular, this does a deep copy of the packet tags.
 2325  */
 2326 int
 2327 m_dup_pkthdr(struct mbuf *to, const struct mbuf *from, int how)
 2328 {
 2329         KASSERT((to->m_flags & M_PKTHDR), ("m_dup_pkthdr: not packet header"));
 2330 
 2331         to->m_flags = (from->m_flags & M_COPYFLAGS) |
 2332                       (to->m_flags & ~M_COPYFLAGS);
 2333         to->m_pkthdr = from->m_pkthdr;
 2334         SLIST_INIT(&to->m_pkthdr.tags);
 2335         return (m_tag_copy_chain(to, from, how));
 2336 }
 2337 
 2338 /*
 2339  * Defragment a mbuf chain, returning the shortest possible
 2340  * chain of mbufs and clusters.  If allocation fails and
 2341  * this cannot be completed, NULL will be returned, but
 2342  * the passed in chain will be unchanged.  Upon success,
 2343  * the original chain will be freed, and the new chain
 2344  * will be returned.
 2345  *
 2346  * If a non-packet header is passed in, the original
 2347  * mbuf (chain?) will be returned unharmed.
 2348  *
 2349  * m_defrag_nofree doesn't free the passed in mbuf.
 2350  */
 2351 struct mbuf *
 2352 m_defrag(struct mbuf *m0, int how)
 2353 {
 2354         struct mbuf *m_new;
 2355 
 2356         if ((m_new = m_defrag_nofree(m0, how)) == NULL)
 2357                 return (NULL);
 2358         if (m_new != m0)
 2359                 m_freem(m0);
 2360         return (m_new);
 2361 }
 2362 
 2363 struct mbuf *
 2364 m_defrag_nofree(struct mbuf *m0, int how)
 2365 {
 2366         struct mbuf     *m_new = NULL, *m_final = NULL;
 2367         int             progress = 0, length, nsize;
 2368 
 2369         if (!(m0->m_flags & M_PKTHDR))
 2370                 return (m0);
 2371 
 2372 #ifdef MBUF_STRESS_TEST
 2373         if (m_defragrandomfailures) {
 2374                 int temp = karc4random() & 0xff;
 2375                 if (temp == 0xba)
 2376                         goto nospace;
 2377         }
 2378 #endif
 2379         
 2380         m_final = m_getl(m0->m_pkthdr.len, how, MT_DATA, M_PKTHDR, &nsize);
 2381         if (m_final == NULL)
 2382                 goto nospace;
 2383         m_final->m_len = 0;     /* in case m0->m_pkthdr.len is zero */
 2384 
 2385         if (m_dup_pkthdr(m_final, m0, how) == 0)
 2386                 goto nospace;
 2387 
 2388         m_new = m_final;
 2389 
 2390         while (progress < m0->m_pkthdr.len) {
 2391                 length = m0->m_pkthdr.len - progress;
 2392                 if (length > MCLBYTES)
 2393                         length = MCLBYTES;
 2394 
 2395                 if (m_new == NULL) {
 2396                         m_new = m_getl(length, how, MT_DATA, 0, &nsize);
 2397                         if (m_new == NULL)
 2398                                 goto nospace;
 2399                 }
 2400 
 2401                 m_copydata(m0, progress, length, mtod(m_new, caddr_t));
 2402                 progress += length;
 2403                 m_new->m_len = length;
 2404                 if (m_new != m_final)
 2405                         m_cat(m_final, m_new);
 2406                 m_new = NULL;
 2407         }
 2408         if (m0->m_next == NULL)
 2409                 m_defraguseless++;
 2410         m_defragpackets++;
 2411         m_defragbytes += m_final->m_pkthdr.len;
 2412         return (m_final);
 2413 nospace:
 2414         m_defragfailure++;
 2415         if (m_new)
 2416                 m_free(m_new);
 2417         m_freem(m_final);
 2418         return (NULL);
 2419 }
 2420 
 2421 /*
 2422  * Move data from uio into mbufs.
 2423  */
 2424 struct mbuf *
 2425 m_uiomove(struct uio *uio)
 2426 {
 2427         struct mbuf *m;                 /* current working mbuf */
 2428         struct mbuf *head = NULL;       /* result mbuf chain */
 2429         struct mbuf **mp = &head;
 2430         int flags = M_PKTHDR;
 2431         int nsize;
 2432         int error;
 2433         int resid;
 2434 
 2435         do {
 2436                 if (uio->uio_resid > INT_MAX)
 2437                         resid = INT_MAX;
 2438                 else
 2439                         resid = (int)uio->uio_resid;
 2440                 m = m_getl(resid, MB_WAIT, MT_DATA, flags, &nsize);
 2441                 if (flags) {
 2442                         m->m_pkthdr.len = 0;
 2443                         /* Leave room for protocol headers. */
 2444                         if (resid < MHLEN)
 2445                                 MH_ALIGN(m, resid);
 2446                         flags = 0;
 2447                 }
 2448                 m->m_len = imin(nsize, resid);
 2449                 error = uiomove(mtod(m, caddr_t), m->m_len, uio);
 2450                 if (error) {
 2451                         m_free(m);
 2452                         goto failed;
 2453                 }
 2454                 *mp = m;
 2455                 mp = &m->m_next;
 2456                 head->m_pkthdr.len += m->m_len;
 2457         } while (uio->uio_resid > 0);
 2458 
 2459         return (head);
 2460 
 2461 failed:
 2462         m_freem(head);
 2463         return (NULL);
 2464 }
 2465 
 2466 struct mbuf *
 2467 m_last(struct mbuf *m)
 2468 {
 2469         while (m->m_next)
 2470                 m = m->m_next;
 2471         return (m);
 2472 }
 2473 
 2474 /*
 2475  * Return the number of bytes in an mbuf chain.
 2476  * If lastm is not NULL, also return the last mbuf.
 2477  */
 2478 u_int
 2479 m_lengthm(struct mbuf *m, struct mbuf **lastm)
 2480 {
 2481         u_int len = 0;
 2482         struct mbuf *prev = m;
 2483 
 2484         while (m) {
 2485                 len += m->m_len;
 2486                 prev = m;
 2487                 m = m->m_next;
 2488         }
 2489         if (lastm != NULL)
 2490                 *lastm = prev;
 2491         return (len);
 2492 }
 2493 
 2494 /*
 2495  * Like m_lengthm(), except also keep track of mbuf usage.
 2496  */
 2497 u_int
 2498 m_countm(struct mbuf *m, struct mbuf **lastm, u_int *pmbcnt)
 2499 {
 2500         u_int len = 0, mbcnt = 0;
 2501         struct mbuf *prev = m;
 2502 
 2503         while (m) {
 2504                 len += m->m_len;
 2505                 mbcnt += MSIZE;
 2506                 if (m->m_flags & M_EXT)
 2507                         mbcnt += m->m_ext.ext_size;
 2508                 prev = m;
 2509                 m = m->m_next;
 2510         }
 2511         if (lastm != NULL)
 2512                 *lastm = prev;
 2513         *pmbcnt = mbcnt;
 2514         return (len);
 2515 }

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