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 /*      uipc_mbuf.c,v 1.84 2004/07/21 12:06:46 yamt Exp */
    2 
    3 /*-
    4  * Copyright (c) 1999, 2001 The NetBSD Foundation, Inc.
    5  * All rights reserved.
    6  *
    7  * This code is derived from software contributed to The NetBSD Foundation
    8  * by Jason R. Thorpe of the Numerical Aerospace Simulation Facility,
    9  * NASA Ames Research Center.
   10  *
   11  * Redistribution and use in source and binary forms, with or without
   12  * modification, are permitted provided that the following conditions
   13  * are met:
   14  * 1. Redistributions of source code must retain the above copyright
   15  *    notice, this list of conditions and the following disclaimer.
   16  * 2. Redistributions in binary form must reproduce the above copyright
   17  *    notice, this list of conditions and the following disclaimer in the
   18  *    documentation and/or other materials provided with the distribution.
   19  * 3. All advertising materials mentioning features or use of this software
   20  *    must display the following acknowledgement:
   21  *      This product includes software developed by the NetBSD
   22  *      Foundation, Inc. and its contributors.
   23  * 4. Neither the name of The NetBSD Foundation nor the names of its
   24  *    contributors may be used to endorse or promote products derived
   25  *    from this software without specific prior written permission.
   26  *
   27  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
   28  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
   29  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
   30  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
   31  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
   32  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
   33  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
   34  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
   35  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
   36  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
   37  * POSSIBILITY OF SUCH DAMAGE.
   38  */
   39 
   40 /*
   41  * Copyright (c) 1982, 1986, 1988, 1991, 1993
   42  *      The Regents of the University of California.  All rights reserved.
   43  *
   44  * Redistribution and use in source and binary forms, with or without
   45  * modification, are permitted provided that the following conditions
   46  * are met:
   47  * 1. Redistributions of source code must retain the above copyright
   48  *    notice, this list of conditions and the following disclaimer.
   49  * 2. Redistributions in binary form must reproduce the above copyright
   50  *    notice, this list of conditions and the following disclaimer in the
   51  *    documentation and/or other materials provided with the distribution.
   52  * 3. Neither the name of the University nor the names of its contributors
   53  *    may be used to endorse or promote products derived from this software
   54  *    without specific prior written permission.
   55  *
   56  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   57  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   58  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   59  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   60  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   61  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   62  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   63  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   64  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   65  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   66  * SUCH DAMAGE.
   67  *
   68  *      @(#)uipc_mbuf.c 8.4 (Berkeley) 2/14/95
   69  */
   70 
   71 #include <sys/cdefs.h>
   72 __KERNEL_RCSID(0, "$NetBSD: uipc_mbuf.c,v 1.80.2.5 2004/10/08 03:05:26 jmc Exp $");
   73 
   74 #include "opt_mbuftrace.h"
   75 
   76 #include <sys/param.h>
   77 #include <sys/systm.h>
   78 #include <sys/proc.h>
   79 #include <sys/malloc.h>
   80 #define MBTYPES
   81 #include <sys/mbuf.h>
   82 #include <sys/kernel.h>
   83 #include <sys/syslog.h>
   84 #include <sys/domain.h>
   85 #include <sys/protosw.h>
   86 #include <sys/pool.h>
   87 #include <sys/socket.h>
   88 #include <sys/sysctl.h>
   89 
   90 #include <net/if.h>
   91 
   92 #include <uvm/uvm.h>
   93 
   94 
   95 struct  pool mbpool;            /* mbuf pool */
   96 struct  pool mclpool;           /* mbuf cluster pool */
   97 
   98 struct pool_cache mbpool_cache;
   99 struct pool_cache mclpool_cache;
  100 
  101 struct mbstat mbstat;
  102 int     max_linkhdr;
  103 int     max_protohdr;
  104 int     max_hdr;
  105 int     max_datalen;
  106 
  107 static int mb_ctor(void *, void *, int);
  108 
  109 void    *mclpool_alloc(struct pool *, int);
  110 void    mclpool_release(struct pool *, void *);
  111 
  112 struct pool_allocator mclpool_allocator = {
  113         mclpool_alloc, mclpool_release, 0,
  114 };
  115 
  116 static struct mbuf *m_copym0(struct mbuf *, int, int, int, int);
  117 static struct mbuf *m_split0(struct mbuf *, int, int, int);
  118 static int m_copyback0(struct mbuf **, int, int, caddr_t, int, int);
  119 
  120 /* flags for m_copyback0 */
  121 #define M_COPYBACK0_COPYBACK    0x0001  /* copyback from cp */
  122 #define M_COPYBACK0_PRESERVE    0x0002  /* preserve original data */
  123 #define M_COPYBACK0_COW         0x0004  /* do copy-on-write */
  124 #define M_COPYBACK0_EXTEND      0x0008  /* extend chain */
  125 
  126 const char mclpool_warnmsg[] =
  127     "WARNING: mclpool limit reached; increase NMBCLUSTERS";
  128 
  129 MALLOC_DEFINE(M_MBUF, "mbuf", "mbuf");
  130 
  131 #ifdef MBUFTRACE
  132 struct mownerhead mowners = LIST_HEAD_INITIALIZER(mowners);
  133 struct mowner unknown_mowners[] = {
  134         { "unknown", "free" },
  135         { "unknown", "data" },
  136         { "unknown", "header" },
  137         { "unknown", "soname" },
  138         { "unknown", "soopts" },
  139         { "unknown", "ftable" },
  140         { "unknown", "control" },
  141         { "unknown", "oobdata" },
  142 };
  143 struct mowner revoked_mowner = { "revoked", "" };
  144 #endif
  145 
  146 /*
  147  * Initialize the mbuf allocator.
  148  */
  149 void
  150 mbinit(void)
  151 {
  152 
  153         KASSERT(sizeof(struct _m_ext) <= MHLEN);
  154         KASSERT(sizeof(struct mbuf) == MSIZE);
  155 
  156         pool_init(&mbpool, msize, 0, 0, 0, "mbpl", NULL);
  157         pool_init(&mclpool, mclbytes, 0, 0, 0, "mclpl", &mclpool_allocator);
  158 
  159         pool_set_drain_hook(&mbpool, m_reclaim, NULL);
  160         pool_set_drain_hook(&mclpool, m_reclaim, NULL);
  161 
  162         pool_cache_init(&mbpool_cache, &mbpool, mb_ctor, NULL, NULL);
  163         pool_cache_init(&mclpool_cache, &mclpool, NULL, NULL, NULL);
  164 
  165         /*
  166          * Set the hard limit on the mclpool to the number of
  167          * mbuf clusters the kernel is to support.  Log the limit
  168          * reached message max once a minute.
  169          */
  170         pool_sethardlimit(&mclpool, nmbclusters, mclpool_warnmsg, 60);
  171 
  172         /*
  173          * Set a low water mark for both mbufs and clusters.  This should
  174          * help ensure that they can be allocated in a memory starvation
  175          * situation.  This is important for e.g. diskless systems which
  176          * must allocate mbufs in order for the pagedaemon to clean pages.
  177          */
  178         pool_setlowat(&mbpool, mblowat);
  179         pool_setlowat(&mclpool, mcllowat);
  180 
  181 #ifdef MBUFTRACE
  182         {
  183                 /*
  184                  * Attach the unknown mowners.
  185                  */
  186                 int i;
  187                 MOWNER_ATTACH(&revoked_mowner);
  188                 for (i = sizeof(unknown_mowners)/sizeof(unknown_mowners[0]);
  189                      i-- > 0; )
  190                         MOWNER_ATTACH(&unknown_mowners[i]);
  191         }
  192 #endif
  193 }
  194 
  195 /*
  196  * sysctl helper routine for the kern.mbuf subtree.  nmbclusters may
  197  * or may not be writable, and mblowat and mcllowat need range
  198  * checking and pool tweaking after being reset.
  199  */
  200 static int
  201 sysctl_kern_mbuf(SYSCTLFN_ARGS)
  202 {
  203         int error, newval;
  204         struct sysctlnode node;
  205 
  206         node = *rnode;
  207         node.sysctl_data = &newval;
  208         switch (rnode->sysctl_num) {
  209         case MBUF_NMBCLUSTERS:
  210                 if (mb_map != NULL) {
  211                         node.sysctl_flags &= ~CTLFLAG_READWRITE;
  212                         node.sysctl_flags |= CTLFLAG_READONLY;
  213                 }
  214                 /* FALLTHROUGH */
  215         case MBUF_MBLOWAT:
  216         case MBUF_MCLLOWAT:
  217                 newval = *(int*)rnode->sysctl_data;
  218                 break;
  219         default:
  220                 return (EOPNOTSUPP);
  221         }
  222 
  223         error = sysctl_lookup(SYSCTLFN_CALL(&node));
  224         if (error || newp == NULL)
  225                 return (error);
  226         if (newval < 0)
  227                 return (EINVAL);
  228 
  229         switch (node.sysctl_num) {
  230         case MBUF_NMBCLUSTERS:
  231                 if (newval < nmbclusters)
  232                         return (EINVAL);
  233                 nmbclusters = newval;
  234                 pool_sethardlimit(&mclpool, nmbclusters, mclpool_warnmsg, 60);
  235                 break;
  236         case MBUF_MBLOWAT:
  237                 mblowat = newval;
  238                 pool_setlowat(&mbpool, mblowat);
  239                 break;
  240         case MBUF_MCLLOWAT:
  241                 mcllowat = newval;
  242                 pool_setlowat(&mclpool, mcllowat);
  243                 break;
  244         }
  245 
  246         return (0);
  247 }
  248 
  249 #ifdef MBUFTRACE
  250 static int
  251 sysctl_kern_mbuf_mowners(SYSCTLFN_ARGS)
  252 {
  253         struct mowner *mo;
  254         size_t len = 0;
  255         int error = 0;
  256 
  257         if (namelen != 0)
  258                 return (EINVAL);
  259         if (newp != NULL)
  260                 return (EPERM);
  261 
  262         LIST_FOREACH(mo, &mowners, mo_link) {
  263                 if (oldp != NULL) {
  264                         if (*oldlenp - len < sizeof(*mo)) {
  265                                 error = ENOMEM;
  266                                 break;
  267                         }
  268                         error = copyout(mo, (caddr_t) oldp + len,
  269                                         sizeof(*mo));
  270                         if (error)
  271                                 break;
  272                 }
  273                 len += sizeof(*mo);
  274         }
  275 
  276         if (error == 0)
  277                 *oldlenp = len;
  278 
  279         return (error);
  280 }
  281 #endif /* MBUFTRACE */
  282 
  283 SYSCTL_SETUP(sysctl_kern_mbuf_setup, "sysctl kern.mbuf subtree setup")
  284 {
  285 
  286         sysctl_createv(clog, 0, NULL, NULL,
  287                        CTLFLAG_PERMANENT,
  288                        CTLTYPE_NODE, "kern", NULL,
  289                        NULL, 0, NULL, 0,
  290                        CTL_KERN, CTL_EOL);
  291         sysctl_createv(clog, 0, NULL, NULL,
  292                        CTLFLAG_PERMANENT,
  293                        CTLTYPE_NODE, "mbuf",
  294                        SYSCTL_DESCR("mbuf control variables"),
  295                        NULL, 0, NULL, 0,
  296                        CTL_KERN, KERN_MBUF, CTL_EOL);
  297 
  298         sysctl_createv(clog, 0, NULL, NULL,
  299                        CTLFLAG_PERMANENT|CTLFLAG_IMMEDIATE,
  300                        CTLTYPE_INT, "msize",
  301                        SYSCTL_DESCR("mbuf base size"),
  302                        NULL, msize, NULL, 0,
  303                        CTL_KERN, KERN_MBUF, MBUF_MSIZE, CTL_EOL);
  304         sysctl_createv(clog, 0, NULL, NULL,
  305                        CTLFLAG_PERMANENT|CTLFLAG_IMMEDIATE,
  306                        CTLTYPE_INT, "mclbytes",
  307                        SYSCTL_DESCR("mbuf cluster size"),
  308                        NULL, mclbytes, NULL, 0,
  309                        CTL_KERN, KERN_MBUF, MBUF_MCLBYTES, CTL_EOL);
  310         sysctl_createv(clog, 0, NULL, NULL,
  311                        CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
  312                        CTLTYPE_INT, "nmbclusters",
  313                        SYSCTL_DESCR("Limit on the number of mbuf clusters"),
  314                        sysctl_kern_mbuf, 0, &nmbclusters, 0,
  315                        CTL_KERN, KERN_MBUF, MBUF_NMBCLUSTERS, CTL_EOL);
  316         sysctl_createv(clog, 0, NULL, NULL,
  317                        CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
  318                        CTLTYPE_INT, "mblowat",
  319                        SYSCTL_DESCR("mbuf low water mark"),
  320                        sysctl_kern_mbuf, 0, &mblowat, 0,
  321                        CTL_KERN, KERN_MBUF, MBUF_MBLOWAT, CTL_EOL);
  322         sysctl_createv(clog, 0, NULL, NULL,
  323                        CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
  324                        CTLTYPE_INT, "mcllowat",
  325                        SYSCTL_DESCR("mbuf cluster low water mark"),
  326                        sysctl_kern_mbuf, 0, &mcllowat, 0,
  327                        CTL_KERN, KERN_MBUF, MBUF_MCLLOWAT, CTL_EOL);
  328         sysctl_createv(clog, 0, NULL, NULL,
  329                        CTLFLAG_PERMANENT,
  330                        CTLTYPE_STRUCT, "stats",
  331                        SYSCTL_DESCR("mbuf allocation statistics"),
  332                        NULL, 0, &mbstat, sizeof(mbstat),
  333                        CTL_KERN, KERN_MBUF, MBUF_STATS, CTL_EOL);
  334 #ifdef MBUFTRACE
  335         sysctl_createv(clog, 0, NULL, NULL,
  336                        CTLFLAG_PERMANENT,
  337                        CTLTYPE_STRUCT, "mowners",
  338                        SYSCTL_DESCR("Information about mbuf owners"),
  339                        sysctl_kern_mbuf_mowners, 0, NULL, 0,
  340                        CTL_KERN, KERN_MBUF, MBUF_MOWNERS, CTL_EOL);
  341 #endif /* MBUFTRACE */
  342 }
  343 
  344 void *
  345 mclpool_alloc(struct pool *pp, int flags)
  346 {
  347         boolean_t waitok = (flags & PR_WAITOK) ? TRUE : FALSE;
  348 
  349         return ((void *)uvm_km_alloc_poolpage1(mb_map, NULL, waitok));
  350 }
  351 
  352 void
  353 mclpool_release(struct pool *pp, void *v)
  354 {
  355 
  356         uvm_km_free_poolpage1(mb_map, (vaddr_t)v);
  357 }
  358 
  359 /*ARGSUSED*/
  360 static int
  361 mb_ctor(void *arg, void *object, int flags)
  362 {
  363         struct mbuf *m = object;
  364 
  365 #ifdef POOL_VTOPHYS
  366         m->m_paddr = POOL_VTOPHYS(m);
  367 #else
  368         m->m_paddr = M_PADDR_INVALID;
  369 #endif
  370         return (0);
  371 }
  372 
  373 void
  374 m_reclaim(void *arg, int flags)
  375 {
  376         struct domain *dp;
  377         struct protosw *pr;
  378         struct ifnet *ifp;
  379         int s = splvm();
  380 
  381         for (dp = domains; dp; dp = dp->dom_next)
  382                 for (pr = dp->dom_protosw;
  383                      pr < dp->dom_protoswNPROTOSW; pr++)
  384                         if (pr->pr_drain)
  385                                 (*pr->pr_drain)();
  386         for (ifp = TAILQ_FIRST(&ifnet); ifp; ifp = TAILQ_NEXT(ifp, if_list))
  387                 if (ifp->if_drain)
  388                         (*ifp->if_drain)(ifp);
  389         splx(s);
  390         mbstat.m_drain++;
  391 }
  392 
  393 /*
  394  * Space allocation routines.
  395  * These are also available as macros
  396  * for critical paths.
  397  */
  398 struct mbuf *
  399 m_get(int nowait, int type)
  400 {
  401         struct mbuf *m;
  402 
  403         MGET(m, nowait, type);
  404         return (m);
  405 }
  406 
  407 struct mbuf *
  408 m_gethdr(int nowait, int type)
  409 {
  410         struct mbuf *m;
  411 
  412         MGETHDR(m, nowait, type);
  413         return (m);
  414 }
  415 
  416 struct mbuf *
  417 m_getclr(int nowait, int type)
  418 {
  419         struct mbuf *m;
  420 
  421         MGET(m, nowait, type);
  422         if (m == 0)
  423                 return (NULL);
  424         memset(mtod(m, caddr_t), 0, MLEN);
  425         return (m);
  426 }
  427 
  428 void
  429 m_clget(struct mbuf *m, int nowait)
  430 {
  431 
  432         MCLGET(m, nowait);
  433 }
  434 
  435 struct mbuf *
  436 m_free(struct mbuf *m)
  437 {
  438         struct mbuf *n;
  439 
  440         MFREE(m, n);
  441         return (n);
  442 }
  443 
  444 void
  445 m_freem(struct mbuf *m)
  446 {
  447         struct mbuf *n;
  448 
  449         if (m == NULL)
  450                 return;
  451         do {
  452                 MFREE(m, n);
  453                 m = n;
  454         } while (m);
  455 }
  456 
  457 #ifdef MBUFTRACE
  458 /*
  459  * Walk a chain of mbufs, claiming ownership of each mbuf in the chain.
  460  */
  461 void
  462 m_claimm(struct mbuf *m, struct mowner *mo)
  463 {
  464 
  465         for (; m != NULL; m = m->m_next)
  466                 MCLAIM(m, mo);
  467 }
  468 #endif
  469 
  470 /*
  471  * Mbuffer utility routines.
  472  */
  473 
  474 /*
  475  * Lesser-used path for M_PREPEND:
  476  * allocate new mbuf to prepend to chain,
  477  * copy junk along.
  478  */
  479 struct mbuf *
  480 m_prepend(struct mbuf *m, int len, int how)
  481 {
  482         struct mbuf *mn;
  483 
  484         MGET(mn, how, m->m_type);
  485         if (mn == (struct mbuf *)NULL) {
  486                 m_freem(m);
  487                 return ((struct mbuf *)NULL);
  488         }
  489         if (m->m_flags & M_PKTHDR) {
  490                 M_COPY_PKTHDR(mn, m);
  491                 m_tag_delete_chain(m, NULL);
  492                 m->m_flags &= ~M_PKTHDR;
  493         } else {
  494                 MCLAIM(mn, m->m_owner);
  495         }
  496         mn->m_next = m;
  497         m = mn;
  498         if (len < MHLEN)
  499                 MH_ALIGN(m, len);
  500         m->m_len = len;
  501         return (m);
  502 }
  503 
  504 /*
  505  * Make a copy of an mbuf chain starting "off0" bytes from the beginning,
  506  * continuing for "len" bytes.  If len is M_COPYALL, copy to end of mbuf.
  507  * The wait parameter is a choice of M_WAIT/M_DONTWAIT from caller.
  508  */
  509 int MCFail;
  510 
  511 struct mbuf *
  512 m_copym(struct mbuf *m, int off0, int len, int wait)
  513 {
  514 
  515         return m_copym0(m, off0, len, wait, 0); /* shallow copy on M_EXT */
  516 }
  517 
  518 struct mbuf *
  519 m_dup(struct mbuf *m, int off0, int len, int wait)
  520 {
  521 
  522         return m_copym0(m, off0, len, wait, 1); /* deep copy */
  523 }
  524 
  525 static struct mbuf *
  526 m_copym0(struct mbuf *m, int off0, int len, int wait, int deep)
  527 {
  528         struct mbuf *n, **np;
  529         int off = off0;
  530         struct mbuf *top;
  531         int copyhdr = 0;
  532 
  533         if (off < 0 || len < 0)
  534                 panic("m_copym: off %d, len %d", off, len);
  535         if (off == 0 && m->m_flags & M_PKTHDR)
  536                 copyhdr = 1;
  537         while (off > 0) {
  538                 if (m == 0)
  539                         panic("m_copym: m == 0");
  540                 if (off < m->m_len)
  541                         break;
  542                 off -= m->m_len;
  543                 m = m->m_next;
  544         }
  545         np = &top;
  546         top = 0;
  547         while (len > 0) {
  548                 if (m == 0) {
  549                         if (len != M_COPYALL)
  550                                 panic("m_copym: m == 0 and not COPYALL");
  551                         break;
  552                 }
  553                 MGET(n, wait, m->m_type);
  554                 *np = n;
  555                 if (n == 0)
  556                         goto nospace;
  557                 MCLAIM(n, m->m_owner);
  558                 if (copyhdr) {
  559                         M_COPY_PKTHDR(n, m);
  560                         if (len == M_COPYALL)
  561                                 n->m_pkthdr.len -= off0;
  562                         else
  563                                 n->m_pkthdr.len = len;
  564                         copyhdr = 0;
  565                 }
  566                 n->m_len = min(len, m->m_len - off);
  567                 if (m->m_flags & M_EXT) {
  568                         if (!deep) {
  569                                 n->m_data = m->m_data + off;
  570                                 n->m_ext = m->m_ext;
  571                                 MCLADDREFERENCE(m, n);
  572                         } else {
  573                                 /*
  574                                  * we are unsure about the way m was allocated.
  575                                  * copy into multiple MCLBYTES cluster mbufs.
  576                                  */
  577                                 MCLGET(n, wait);
  578                                 n->m_len = 0;
  579                                 n->m_len = M_TRAILINGSPACE(n);
  580                                 n->m_len = min(n->m_len, len);
  581                                 n->m_len = min(n->m_len, m->m_len - off);
  582                                 memcpy(mtod(n, caddr_t), mtod(m, caddr_t) + off,
  583                                     (unsigned)n->m_len);
  584                         }
  585                 } else
  586                         memcpy(mtod(n, caddr_t), mtod(m, caddr_t)+off,
  587                             (unsigned)n->m_len);
  588                 if (len != M_COPYALL)
  589                         len -= n->m_len;
  590                 off += n->m_len;
  591 #ifdef DIAGNOSTIC
  592                 if (off > m->m_len)
  593                         panic("m_copym0 overrun");
  594 #endif
  595                 if (off == m->m_len) {
  596                         m = m->m_next;
  597                         off = 0;
  598                 }
  599                 np = &n->m_next;
  600         }
  601         if (top == 0)
  602                 MCFail++;
  603         return (top);
  604 nospace:
  605         m_freem(top);
  606         MCFail++;
  607         return (NULL);
  608 }
  609 
  610 /*
  611  * Copy an entire packet, including header (which must be present).
  612  * An optimization of the common case `m_copym(m, 0, M_COPYALL, how)'.
  613  */
  614 struct mbuf *
  615 m_copypacket(struct mbuf *m, int how)
  616 {
  617         struct mbuf *top, *n, *o;
  618 
  619         MGET(n, how, m->m_type);
  620         top = n;
  621         if (!n)
  622                 goto nospace;
  623 
  624         MCLAIM(n, m->m_owner);
  625         M_COPY_PKTHDR(n, m);
  626         n->m_len = m->m_len;
  627         if (m->m_flags & M_EXT) {
  628                 n->m_data = m->m_data;
  629                 n->m_ext = m->m_ext;
  630                 MCLADDREFERENCE(m, n);
  631         } else {
  632                 memcpy(mtod(n, char *), mtod(m, char *), n->m_len);
  633         }
  634 
  635         m = m->m_next;
  636         while (m) {
  637                 MGET(o, how, m->m_type);
  638                 if (!o)
  639                         goto nospace;
  640 
  641                 MCLAIM(o, m->m_owner);
  642                 n->m_next = o;
  643                 n = n->m_next;
  644 
  645                 n->m_len = m->m_len;
  646                 if (m->m_flags & M_EXT) {
  647                         n->m_data = m->m_data;
  648                         n->m_ext = m->m_ext;
  649                         MCLADDREFERENCE(m, n);
  650                 } else {
  651                         memcpy(mtod(n, char *), mtod(m, char *), n->m_len);
  652                 }
  653 
  654                 m = m->m_next;
  655         }
  656         return top;
  657 nospace:
  658         m_freem(top);
  659         MCFail++;
  660         return NULL;
  661 }
  662 
  663 /*
  664  * Copy data from an mbuf chain starting "off" bytes from the beginning,
  665  * continuing for "len" bytes, into the indicated buffer.
  666  */
  667 void
  668 m_copydata(struct mbuf *m, int off, int len, caddr_t cp)
  669 {
  670         unsigned count;
  671 
  672         if (off < 0 || len < 0)
  673                 panic("m_copydata");
  674         while (off > 0) {
  675                 if (m == 0)
  676                         panic("m_copydata");
  677                 if (off < m->m_len)
  678                         break;
  679                 off -= m->m_len;
  680                 m = m->m_next;
  681         }
  682         while (len > 0) {
  683                 if (m == 0)
  684                         panic("m_copydata");
  685                 count = min(m->m_len - off, len);
  686                 memcpy(cp, mtod(m, caddr_t) + off, count);
  687                 len -= count;
  688                 cp += count;
  689                 off = 0;
  690                 m = m->m_next;
  691         }
  692 }
  693 
  694 /*
  695  * Concatenate mbuf chain n to m.
  696  * n might be copied into m (when n->m_len is small), therefore data portion of
  697  * n could be copied into an mbuf of different mbuf type.
  698  * Any m_pkthdr is not updated.
  699  */
  700 void
  701 m_cat(struct mbuf *m, struct mbuf *n)
  702 {
  703 
  704         while (m->m_next)
  705                 m = m->m_next;
  706         while (n) {
  707                 if (M_READONLY(m) || n->m_len > M_TRAILINGSPACE(m)) {
  708                         /* just join the two chains */
  709                         m->m_next = n;
  710                         return;
  711                 }
  712                 /* splat the data from one into the other */
  713                 memcpy(mtod(m, caddr_t) + m->m_len, mtod(n, caddr_t),
  714                     (u_int)n->m_len);
  715                 m->m_len += n->m_len;
  716                 n = m_free(n);
  717         }
  718 }
  719 
  720 void
  721 m_adj(struct mbuf *mp, int req_len)
  722 {
  723         int len = req_len;
  724         struct mbuf *m;
  725         int count;
  726 
  727         if ((m = mp) == NULL)
  728                 return;
  729         if (len >= 0) {
  730                 /*
  731                  * Trim from head.
  732                  */
  733                 while (m != NULL && len > 0) {
  734                         if (m->m_len <= len) {
  735                                 len -= m->m_len;
  736                                 m->m_len = 0;
  737                                 m = m->m_next;
  738                         } else {
  739                                 m->m_len -= len;
  740                                 m->m_data += len;
  741                                 len = 0;
  742                         }
  743                 }
  744                 m = mp;
  745                 if (mp->m_flags & M_PKTHDR)
  746                         m->m_pkthdr.len -= (req_len - len);
  747         } else {
  748                 /*
  749                  * Trim from tail.  Scan the mbuf chain,
  750                  * calculating its length and finding the last mbuf.
  751                  * If the adjustment only affects this mbuf, then just
  752                  * adjust and return.  Otherwise, rescan and truncate
  753                  * after the remaining size.
  754                  */
  755                 len = -len;
  756                 count = 0;
  757                 for (;;) {
  758                         count += m->m_len;
  759                         if (m->m_next == (struct mbuf *)0)
  760                                 break;
  761                         m = m->m_next;
  762                 }
  763                 if (m->m_len >= len) {
  764                         m->m_len -= len;
  765                         if (mp->m_flags & M_PKTHDR)
  766                                 mp->m_pkthdr.len -= len;
  767                         return;
  768                 }
  769                 count -= len;
  770                 if (count < 0)
  771                         count = 0;
  772                 /*
  773                  * Correct length for chain is "count".
  774                  * Find the mbuf with last data, adjust its length,
  775                  * and toss data from remaining mbufs on chain.
  776                  */
  777                 m = mp;
  778                 if (m->m_flags & M_PKTHDR)
  779                         m->m_pkthdr.len = count;
  780                 for (; m; m = m->m_next) {
  781                         if (m->m_len >= count) {
  782                                 m->m_len = count;
  783                                 break;
  784                         }
  785                         count -= m->m_len;
  786                 }
  787                 while (m->m_next)
  788                         (m = m->m_next) ->m_len = 0;
  789         }
  790 }
  791 
  792 /*
  793  * Rearange an mbuf chain so that len bytes are contiguous
  794  * and in the data area of an mbuf (so that mtod and dtom
  795  * will work for a structure of size len).  Returns the resulting
  796  * mbuf chain on success, frees it and returns null on failure.
  797  * If there is room, it will add up to max_protohdr-len extra bytes to the
  798  * contiguous region in an attempt to avoid being called next time.
  799  */
  800 int MPFail;
  801 
  802 struct mbuf *
  803 m_pullup(struct mbuf *n, int len)
  804 {
  805         struct mbuf *m;
  806         int count;
  807         int space;
  808 
  809         /*
  810          * If first mbuf has no cluster, and has room for len bytes
  811          * without shifting current data, pullup into it,
  812          * otherwise allocate a new mbuf to prepend to the chain.
  813          */
  814         if ((n->m_flags & M_EXT) == 0 &&
  815             n->m_data + len < &n->m_dat[MLEN] && n->m_next) {
  816                 if (n->m_len >= len)
  817                         return (n);
  818                 m = n;
  819                 n = n->m_next;
  820                 len -= m->m_len;
  821         } else {
  822                 if (len > MHLEN)
  823                         goto bad;
  824                 MGET(m, M_DONTWAIT, n->m_type);
  825                 if (m == 0)
  826                         goto bad;
  827                 MCLAIM(m, n->m_owner);
  828                 m->m_len = 0;
  829                 if (n->m_flags & M_PKTHDR) {
  830                         M_COPY_PKTHDR(m, n);
  831                         m_tag_delete_chain(n, NULL);
  832                         n->m_flags &= ~M_PKTHDR;
  833                 }
  834         }
  835         space = &m->m_dat[MLEN] - (m->m_data + m->m_len);
  836         do {
  837                 count = min(min(max(len, max_protohdr), space), n->m_len);
  838                 memcpy(mtod(m, caddr_t) + m->m_len, mtod(n, caddr_t),
  839                   (unsigned)count);
  840                 len -= count;
  841                 m->m_len += count;
  842                 n->m_len -= count;
  843                 space -= count;
  844                 if (n->m_len)
  845                         n->m_data += count;
  846                 else
  847                         n = m_free(n);
  848         } while (len > 0 && n);
  849         if (len > 0) {
  850                 (void) m_free(m);
  851                 goto bad;
  852         }
  853         m->m_next = n;
  854         return (m);
  855 bad:
  856         m_freem(n);
  857         MPFail++;
  858         return (NULL);
  859 }
  860 
  861 /*
  862  * Like m_pullup(), except a new mbuf is always allocated, and we allow
  863  * the amount of empty space before the data in the new mbuf to be specified
  864  * (in the event that the caller expects to prepend later).
  865  */
  866 int MSFail;
  867 
  868 struct mbuf *
  869 m_copyup(struct mbuf *n, int len, int dstoff)
  870 {
  871         struct mbuf *m;
  872         int count, space;
  873 
  874         if (len > (MHLEN - dstoff))
  875                 goto bad;
  876         MGET(m, M_DONTWAIT, n->m_type);
  877         if (m == NULL)
  878                 goto bad;
  879         MCLAIM(m, n->m_owner);
  880         m->m_len = 0;
  881         if (n->m_flags & M_PKTHDR) {
  882                 M_COPY_PKTHDR(m, n);
  883                 m_tag_delete_chain(m, NULL);
  884                 n->m_flags &= ~M_PKTHDR;
  885         }
  886         m->m_data += dstoff;
  887         space = &m->m_dat[MLEN] - (m->m_data + m->m_len);
  888         do {
  889                 count = min(min(max(len, max_protohdr), space), n->m_len);
  890                 memcpy(mtod(m, caddr_t) + m->m_len, mtod(n, caddr_t),
  891                     (unsigned)count);
  892                 len -= count;
  893                 m->m_len += count;
  894                 n->m_len -= count;
  895                 space -= count;
  896                 if (n->m_len)
  897                         n->m_data += count;
  898                 else
  899                         n = m_free(n);
  900         } while (len > 0 && n);
  901         if (len > 0) {
  902                 (void) m_free(m);
  903                 goto bad;
  904         }
  905         m->m_next = n;
  906         return (m);
  907  bad:
  908         m_freem(n);
  909         MSFail++;
  910         return (NULL);
  911 }
  912 
  913 /*
  914  * Partition an mbuf chain in two pieces, returning the tail --
  915  * all but the first len0 bytes.  In case of failure, it returns NULL and
  916  * attempts to restore the chain to its original state.
  917  */
  918 struct mbuf *
  919 m_split(struct mbuf *m0, int len0, int wait)
  920 {
  921 
  922         return m_split0(m0, len0, wait, 1);
  923 }
  924 
  925 static struct mbuf *
  926 m_split0(struct mbuf *m0, int len0, int wait, int copyhdr)
  927 {
  928         struct mbuf *m, *n;
  929         unsigned len = len0, remain, len_save;
  930 
  931         for (m = m0; m && len > m->m_len; m = m->m_next)
  932                 len -= m->m_len;
  933         if (m == 0)
  934                 return (NULL);
  935         remain = m->m_len - len;
  936         if (copyhdr && (m0->m_flags & M_PKTHDR)) {
  937                 MGETHDR(n, wait, m0->m_type);
  938                 if (n == 0)
  939                         return (NULL);
  940                 MCLAIM(m, m0->m_owner);
  941                 n->m_pkthdr.rcvif = m0->m_pkthdr.rcvif;
  942                 n->m_pkthdr.len = m0->m_pkthdr.len - len0;
  943                 len_save = m0->m_pkthdr.len;
  944                 m0->m_pkthdr.len = len0;
  945                 if (m->m_flags & M_EXT)
  946                         goto extpacket;
  947                 if (remain > MHLEN) {
  948                         /* m can't be the lead packet */
  949                         MH_ALIGN(n, 0);
  950                         n->m_next = m_split(m, len, wait);
  951                         if (n->m_next == 0) {
  952                                 (void) m_free(n);
  953                                 m0->m_pkthdr.len = len_save;
  954                                 return (NULL);
  955                         } else
  956                                 return (n);
  957                 } else
  958                         MH_ALIGN(n, remain);
  959         } else if (remain == 0) {
  960                 n = m->m_next;
  961                 m->m_next = 0;
  962                 return (n);
  963         } else {
  964                 MGET(n, wait, m->m_type);
  965                 if (n == 0)
  966                         return (NULL);
  967                 MCLAIM(n, m->m_owner);
  968                 M_ALIGN(n, remain);
  969         }
  970 extpacket:
  971         if (m->m_flags & M_EXT) {
  972                 n->m_ext = m->m_ext;
  973                 MCLADDREFERENCE(m, n);
  974                 n->m_data = m->m_data + len;
  975         } else {
  976                 memcpy(mtod(n, caddr_t), mtod(m, caddr_t) + len, remain);
  977         }
  978         n->m_len = remain;
  979         m->m_len = len;
  980         n->m_next = m->m_next;
  981         m->m_next = 0;
  982         return (n);
  983 }
  984 /*
  985  * Routine to copy from device local memory into mbufs.
  986  */
  987 struct mbuf *
  988 m_devget(char *buf, int totlen, int off0, struct ifnet *ifp,
  989     void (*copy)(const void *from, void *to, size_t len))
  990 {
  991         struct mbuf *m;
  992         struct mbuf *top = 0, **mp = &top;
  993         int off = off0, len;
  994         char *cp;
  995         char *epkt;
  996 
  997         cp = buf;
  998         epkt = cp + totlen;
  999         if (off) {
 1000                 /*
 1001                  * If 'off' is non-zero, packet is trailer-encapsulated,
 1002                  * so we have to skip the type and length fields.
 1003                  */
 1004                 cp += off + 2 * sizeof(u_int16_t);
 1005                 totlen -= 2 * sizeof(u_int16_t);
 1006         }
 1007         MGETHDR(m, M_DONTWAIT, MT_DATA);
 1008         if (m == 0)
 1009                 return (NULL);
 1010         m->m_pkthdr.rcvif = ifp;
 1011         m->m_pkthdr.len = totlen;
 1012         m->m_len = MHLEN;
 1013 
 1014         while (totlen > 0) {
 1015                 if (top) {
 1016                         MGET(m, M_DONTWAIT, MT_DATA);
 1017                         if (m == 0) {
 1018                                 m_freem(top);
 1019                                 return (NULL);
 1020                         }
 1021                         m->m_len = MLEN;
 1022                 }
 1023                 len = min(totlen, epkt - cp);
 1024                 if (len >= MINCLSIZE) {
 1025                         MCLGET(m, M_DONTWAIT);
 1026                         if ((m->m_flags & M_EXT) == 0) {
 1027                                 m_free(m);
 1028                                 m_freem(top);
 1029                                 return (NULL);
 1030                         }
 1031                         m->m_len = len = min(len, MCLBYTES);
 1032                 } else {
 1033                         /*
 1034                          * Place initial small packet/header at end of mbuf.
 1035                          */
 1036                         if (len < m->m_len) {
 1037                                 if (top == 0 && len + max_linkhdr <= m->m_len)
 1038                                         m->m_data += max_linkhdr;
 1039                                 m->m_len = len;
 1040                         } else
 1041                                 len = m->m_len;
 1042                 }
 1043                 if (copy)
 1044                         copy(cp, mtod(m, caddr_t), (size_t)len);
 1045                 else
 1046                         memcpy(mtod(m, caddr_t), cp, (size_t)len);
 1047                 cp += len;
 1048                 *mp = m;
 1049                 mp = &m->m_next;
 1050                 totlen -= len;
 1051                 if (cp == epkt)
 1052                         cp = buf;
 1053         }
 1054         return (top);
 1055 }
 1056 
 1057 /*
 1058  * Copy data from a buffer back into the indicated mbuf chain,
 1059  * starting "off" bytes from the beginning, extending the mbuf
 1060  * chain if necessary.
 1061  */
 1062 void
 1063 m_copyback(struct mbuf *m0, int off, int len, caddr_t cp)
 1064 {
 1065 #if defined(DEBUG)
 1066         struct mbuf *origm = m0;
 1067         int error;
 1068 #endif /* defined(DEBUG) */
 1069 
 1070         if (m0 == NULL)
 1071                 return;
 1072 
 1073 #if defined(DEBUG)
 1074         error =
 1075 #endif /* defined(DEBUG) */
 1076         m_copyback0(&m0, off, len, cp,
 1077             M_COPYBACK0_COPYBACK|M_COPYBACK0_EXTEND, M_DONTWAIT);
 1078 
 1079 #if defined(DEBUG)
 1080         if (error != 0 || (m0 != NULL && origm != m0))
 1081                 panic("m_copyback");
 1082 #endif /* defined(DEBUG) */
 1083 }
 1084 
 1085 struct mbuf *
 1086 m_copyback_cow(struct mbuf *m0, int off, int len, caddr_t cp, int how)
 1087 {
 1088         int error;
 1089 
 1090         /* don't support chain expansion */
 1091         KDASSERT(off + len <= m_length(m0));
 1092 
 1093         error = m_copyback0(&m0, off, len, cp,
 1094             M_COPYBACK0_COPYBACK|M_COPYBACK0_COW, how);
 1095         if (error) {
 1096                 /*
 1097                  * no way to recover from partial success.
 1098                  * just free the chain.
 1099                  */
 1100                 m_freem(m0);
 1101                 return NULL;
 1102         }
 1103         return m0;
 1104 }
 1105 
 1106 /*
 1107  * m_makewritable: ensure the specified range writable.
 1108  */
 1109 int
 1110 m_makewritable(struct mbuf **mp, int off, int len, int how)
 1111 {
 1112         int error;
 1113 #if defined(DEBUG)
 1114         struct mbuf *n;
 1115         int origlen, reslen;
 1116 
 1117         origlen = m_length(*mp);
 1118 #endif /* defined(DEBUG) */
 1119 
 1120 #if 0 /* M_COPYALL is large enough */
 1121         if (len == M_COPYALL)
 1122                 len = m_length(*mp) - off; /* XXX */
 1123 #endif
 1124 
 1125         error = m_copyback0(mp, off, len, NULL,
 1126             M_COPYBACK0_PRESERVE|M_COPYBACK0_COW, how);
 1127 
 1128 #if defined(DEBUG)
 1129         reslen = 0;
 1130         for (n = *mp; n; n = n->m_next)
 1131                 reslen += n->m_len;
 1132         if (origlen != reslen)
 1133                 panic("m_makewritable: length changed");
 1134         if (((*mp)->m_flags & M_PKTHDR) != 0 && reslen != (*mp)->m_pkthdr.len)
 1135                 panic("m_makewritable: inconsist");
 1136 #endif /* defined(DEBUG) */
 1137 
 1138         return error;
 1139 }
 1140 
 1141 int
 1142 m_copyback0(struct mbuf **mp0, int off, int len, caddr_t cp, int flags, int how)
 1143 {
 1144         int mlen;
 1145         struct mbuf *m, *n;
 1146         struct mbuf **mp;
 1147         int totlen = 0;
 1148 
 1149         KASSERT(mp0 != NULL);
 1150         KASSERT(*mp0 != NULL);
 1151         KASSERT((flags & M_COPYBACK0_PRESERVE) == 0 || cp == NULL);
 1152         KASSERT((flags & M_COPYBACK0_COPYBACK) == 0 || cp != NULL);
 1153 
 1154         mp = mp0;
 1155         m = *mp;
 1156         while (off > (mlen = m->m_len)) {
 1157                 off -= mlen;
 1158                 totlen += mlen;
 1159                 if (m->m_next == 0) {
 1160                         if ((flags & M_COPYBACK0_EXTEND) == 0)
 1161                                 goto out;
 1162                         n = m_getclr(how, m->m_type);
 1163                         if (n == 0)
 1164                                 goto out;
 1165                         n->m_len = min(MLEN, len + off);
 1166                         m->m_next = n;
 1167                 }
 1168                 mp = &m->m_next;
 1169                 m = m->m_next;
 1170         }
 1171         while (len > 0) {
 1172                 mlen = m->m_len - off;
 1173                 if (mlen != 0 && M_READONLY(m)) {
 1174                         char *datap;
 1175                         int eatlen;
 1176 
 1177                         /*
 1178                          * this mbuf is read-only.
 1179                          * allocate a new writable mbuf and try again.
 1180                          */
 1181 
 1182 #if defined(DIAGNOSTIC)
 1183                         if ((flags & M_COPYBACK0_COW) == 0)
 1184                                 panic("m_copyback0: read-only");
 1185 #endif /* defined(DIAGNOSTIC) */
 1186 
 1187                         /*
 1188                          * if we're going to write into the middle of
 1189                          * a mbuf, split it first.
 1190                          */
 1191                         if (off > 0 && len < mlen) {
 1192                                 n = m_split0(m, off, how, 0);
 1193                                 if (n == NULL)
 1194                                         goto enobufs;
 1195                                 m->m_next = n;
 1196                                 mp = &m->m_next;
 1197                                 m = n;
 1198                                 off = 0;
 1199                                 continue;
 1200                         }
 1201 
 1202                         /*
 1203                          * XXX TODO coalesce into the trailingspace of
 1204                          * the previous mbuf when possible.
 1205                          */
 1206 
 1207                         /*
 1208                          * allocate a new mbuf.  copy packet header if needed.
 1209                          */
 1210                         MGET(n, how, m->m_type);
 1211                         if (n == NULL)
 1212                                 goto enobufs;
 1213                         MCLAIM(n, m->m_owner);
 1214                         if (off == 0 && (m->m_flags & M_PKTHDR) != 0) {
 1215                                 /* XXX M_MOVE_PKTHDR */
 1216                                 M_COPY_PKTHDR(n, m);
 1217                                 n->m_len = MHLEN;
 1218                         } else {
 1219                                 if (len >= MINCLSIZE)
 1220                                         MCLGET(n, M_DONTWAIT);
 1221                                 n->m_len =
 1222                                     (n->m_flags & M_EXT) ? MCLBYTES : MLEN;
 1223                         }
 1224                         if (n->m_len > len)
 1225                                 n->m_len = len;
 1226 
 1227                         /*
 1228                          * free the region which has been overwritten.
 1229                          * copying data from old mbufs if requested.
 1230                          */
 1231                         if (flags & M_COPYBACK0_PRESERVE)
 1232                                 datap = mtod(n, char *);
 1233                         else
 1234                                 datap = NULL;
 1235                         eatlen = n->m_len;
 1236                         KDASSERT(off == 0 || eatlen >= mlen);
 1237                         if (off > 0) {
 1238                                 KDASSERT(len >= mlen);
 1239                                 m->m_len = off;
 1240                                 m->m_next = n;
 1241                                 if (datap) {
 1242                                         m_copydata(m, off, mlen, datap);
 1243                                         datap += mlen;
 1244                                 }
 1245                                 eatlen -= mlen;
 1246                                 mp = &m->m_next;
 1247                                 m = m->m_next;
 1248                         }
 1249                         while (m != NULL && M_READONLY(m) &&
 1250                             n->m_type == m->m_type && eatlen > 0) {
 1251                                 mlen = min(eatlen, m->m_len);
 1252                                 if (datap) {
 1253                                         m_copydata(m, 0, mlen, datap);
 1254                                         datap += mlen;
 1255                                 }
 1256                                 m->m_data += mlen;
 1257                                 m->m_len -= mlen;
 1258                                 eatlen -= mlen;
 1259                                 if (m->m_len == 0)
 1260                                         *mp = m = m_free(m);
 1261                         }
 1262                         if (eatlen > 0)
 1263                                 n->m_len -= eatlen;
 1264                         n->m_next = m;
 1265                         *mp = m = n;
 1266                         continue;
 1267                 }
 1268                 mlen = min(mlen, len);
 1269                 if (flags & M_COPYBACK0_COPYBACK) {
 1270                         memcpy(mtod(m, caddr_t) + off, cp, (unsigned)mlen);
 1271                         cp += mlen;
 1272                 }
 1273                 len -= mlen;
 1274                 mlen += off;
 1275                 off = 0;
 1276                 totlen += mlen;
 1277                 if (len == 0)
 1278                         break;
 1279                 if (m->m_next == 0) {
 1280                         if ((flags & M_COPYBACK0_EXTEND) == 0)
 1281                                 goto out;
 1282                         n = m_get(how, m->m_type);
 1283                         if (n == 0)
 1284                                 break;
 1285                         n->m_len = min(MLEN, len);
 1286                         m->m_next = n;
 1287                 }
 1288                 mp = &m->m_next;
 1289                 m = m->m_next;
 1290         }
 1291 out:    if (((m = *mp0)->m_flags & M_PKTHDR) && (m->m_pkthdr.len < totlen))
 1292                 m->m_pkthdr.len = totlen;
 1293 
 1294         return 0;
 1295 
 1296 enobufs:
 1297         return ENOBUFS;
 1298 }
 1299 
 1300 /*
 1301  * Apply function f to the data in an mbuf chain starting "off" bytes from the
 1302  * beginning, continuing for "len" bytes.
 1303  */
 1304 int
 1305 m_apply(struct mbuf *m, int off, int len,
 1306     int (*f)(void *, caddr_t, unsigned int), void *arg)
 1307 {
 1308         unsigned int count;
 1309         int rval;
 1310 
 1311         KASSERT(len >= 0);
 1312         KASSERT(off >= 0);
 1313 
 1314         while (off > 0) {
 1315                 KASSERT(m != NULL);
 1316                 if (off < m->m_len)
 1317                         break;
 1318                 off -= m->m_len;
 1319                 m = m->m_next;
 1320         }
 1321         while (len > 0) {
 1322                 KASSERT(m != NULL);
 1323                 count = min(m->m_len - off, len);
 1324 
 1325                 rval = (*f)(arg, mtod(m, caddr_t) + off, count);
 1326                 if (rval)
 1327                         return (rval);
 1328 
 1329                 len -= count;
 1330                 off = 0;
 1331                 m = m->m_next;
 1332         }
 1333 
 1334         return (0);
 1335 }
 1336 
 1337 /*
 1338  * Return a pointer to mbuf/offset of location in mbuf chain.
 1339  */
 1340 struct mbuf *
 1341 m_getptr(struct mbuf *m, int loc, int *off)
 1342 {
 1343 
 1344         while (loc >= 0) {
 1345                 /* Normal end of search */
 1346                 if (m->m_len > loc) {
 1347                         *off = loc;
 1348                         return (m);
 1349                 } else {
 1350                         loc -= m->m_len;
 1351 
 1352                         if (m->m_next == NULL) {
 1353                                 if (loc == 0) {
 1354                                         /* Point at the end of valid data */
 1355                                         *off = m->m_len;
 1356                                         return (m);
 1357                                 } else
 1358                                         return (NULL);
 1359                         } else
 1360                                 m = m->m_next;
 1361                 }
 1362         }
 1363 
 1364         return (NULL);
 1365 }

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