The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: 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  * Copyright (c) 1982, 1986, 1988, 1991, 1993
    3  *      The Regents of the University of California.  All rights reserved.
    4  *
    5  * Redistribution and use in source and binary forms, with or without
    6  * modification, are permitted provided that the following conditions
    7  * are met:
    8  * 1. Redistributions of source code must retain the above copyright
    9  *    notice, this list of conditions and the following disclaimer.
   10  * 2. Redistributions in binary form must reproduce the above copyright
   11  *    notice, this list of conditions and the following disclaimer in the
   12  *    documentation and/or other materials provided with the distribution.
   13  * 4. Neither the name of the University nor the names of its contributors
   14  *    may be used to endorse or promote products derived from this software
   15  *    without specific prior written permission.
   16  *
   17  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   27  * SUCH DAMAGE.
   28  *
   29  *      @(#)uipc_mbuf.c 8.2 (Berkeley) 1/4/94
   30  */
   31 
   32 #include <sys/cdefs.h>
   33 __FBSDID("$FreeBSD: releng/6.4/sys/kern/uipc_mbuf.c 157061 2006-03-23 23:24:33Z sam $");
   34 
   35 #include "opt_mac.h"
   36 #include "opt_param.h"
   37 #include "opt_mbuf_stress_test.h"
   38 
   39 #include <sys/param.h>
   40 #include <sys/systm.h>
   41 #include <sys/kernel.h>
   42 #include <sys/limits.h>
   43 #include <sys/lock.h>
   44 #include <sys/mac.h>
   45 #include <sys/malloc.h>
   46 #include <sys/mbuf.h>
   47 #include <sys/sysctl.h>
   48 #include <sys/domain.h>
   49 #include <sys/protosw.h>
   50 #include <sys/uio.h>
   51 
   52 int     max_linkhdr;
   53 int     max_protohdr;
   54 int     max_hdr;
   55 int     max_datalen;
   56 #ifdef MBUF_STRESS_TEST
   57 int     m_defragpackets;
   58 int     m_defragbytes;
   59 int     m_defraguseless;
   60 int     m_defragfailure;
   61 int     m_defragrandomfailures;
   62 #endif
   63 
   64 /*
   65  * sysctl(8) exported objects
   66  */
   67 SYSCTL_DECL(_kern_ipc);
   68 SYSCTL_INT(_kern_ipc, KIPC_MAX_LINKHDR, max_linkhdr, CTLFLAG_RD,
   69            &max_linkhdr, 0, "Size of largest link layer header");
   70 SYSCTL_INT(_kern_ipc, KIPC_MAX_PROTOHDR, max_protohdr, CTLFLAG_RD,
   71            &max_protohdr, 0, "Size of largest protocol layer header");
   72 SYSCTL_INT(_kern_ipc, KIPC_MAX_HDR, max_hdr, CTLFLAG_RD,
   73            &max_hdr, 0, "Size of largest link plus protocol header");
   74 SYSCTL_INT(_kern_ipc, KIPC_MAX_DATALEN, max_datalen, CTLFLAG_RD,
   75            &max_datalen, 0, "Minimum space left in mbuf after max_hdr");
   76 #ifdef MBUF_STRESS_TEST
   77 SYSCTL_INT(_kern_ipc, OID_AUTO, m_defragpackets, CTLFLAG_RD,
   78            &m_defragpackets, 0, "");
   79 SYSCTL_INT(_kern_ipc, OID_AUTO, m_defragbytes, CTLFLAG_RD,
   80            &m_defragbytes, 0, "");
   81 SYSCTL_INT(_kern_ipc, OID_AUTO, m_defraguseless, CTLFLAG_RD,
   82            &m_defraguseless, 0, "");
   83 SYSCTL_INT(_kern_ipc, OID_AUTO, m_defragfailure, CTLFLAG_RD,
   84            &m_defragfailure, 0, "");
   85 SYSCTL_INT(_kern_ipc, OID_AUTO, m_defragrandomfailures, CTLFLAG_RW,
   86            &m_defragrandomfailures, 0, "");
   87 #endif
   88 
   89 /*
   90  * Malloc-type for external ext_buf ref counts.
   91  */
   92 static MALLOC_DEFINE(M_MBUF, "mbextcnt", "mbuf external ref counts");
   93 
   94 /*
   95  * Allocate a given length worth of mbufs and/or clusters (whatever fits
   96  * best) and return a pointer to the top of the allocated chain.  If an
   97  * existing mbuf chain is provided, then we will append the new chain
   98  * to the existing one but still return the top of the newly allocated
   99  * chain.
  100  */
  101 struct mbuf *
  102 m_getm(struct mbuf *m, int len, int how, short type)
  103 {
  104         struct mbuf *mb, *top, *cur, *mtail;
  105         int num, rem;
  106         int i;
  107 
  108         KASSERT(len >= 0, ("m_getm(): len is < 0"));
  109 
  110         /* If m != NULL, we will append to the end of that chain. */
  111         if (m != NULL)
  112                 for (mtail = m; mtail->m_next != NULL; mtail = mtail->m_next);
  113         else
  114                 mtail = NULL;
  115 
  116         /*
  117          * Calculate how many mbufs+clusters ("packets") we need and how much
  118          * leftover there is after that and allocate the first mbuf+cluster
  119          * if required.
  120          */
  121         num = len / MCLBYTES;
  122         rem = len % MCLBYTES;
  123         top = cur = NULL;
  124         if (num > 0) {
  125                 if ((top = cur = m_getcl(how, type, 0)) == NULL)
  126                         goto failed;
  127                 top->m_len = 0;
  128         }
  129         num--;
  130 
  131         for (i = 0; i < num; i++) {
  132                 mb = m_getcl(how, type, 0);
  133                 if (mb == NULL)
  134                         goto failed;
  135                 mb->m_len = 0;
  136                 cur = (cur->m_next = mb);
  137         }
  138         if (rem > 0) {
  139                 mb = (rem > MINCLSIZE) ?
  140                     m_getcl(how, type, 0) : m_get(how, type);
  141                 if (mb == NULL)
  142                         goto failed;
  143                 mb->m_len = 0;
  144                 if (cur == NULL)
  145                         top = mb;
  146                 else
  147                         cur->m_next = mb;
  148         }
  149 
  150         if (mtail != NULL)
  151                 mtail->m_next = top;
  152         return top;
  153 failed:
  154         if (top != NULL)
  155                 m_freem(top);
  156         return NULL;
  157 }
  158 
  159 /*
  160  * Free an entire chain of mbufs and associated external buffers, if
  161  * applicable.
  162  */
  163 void
  164 m_freem(struct mbuf *mb)
  165 {
  166 
  167         while (mb != NULL)
  168                 mb = m_free(mb);
  169 }
  170 
  171 /*-
  172  * Configure a provided mbuf to refer to the provided external storage
  173  * buffer and setup a reference count for said buffer.  If the setting
  174  * up of the reference count fails, the M_EXT bit will not be set.  If
  175  * successfull, the M_EXT bit is set in the mbuf's flags.
  176  *
  177  * Arguments:
  178  *    mb     The existing mbuf to which to attach the provided buffer.
  179  *    buf    The address of the provided external storage buffer.
  180  *    size   The size of the provided buffer.
  181  *    freef  A pointer to a routine that is responsible for freeing the
  182  *           provided external storage buffer.
  183  *    args   A pointer to an argument structure (of any type) to be passed
  184  *           to the provided freef routine (may be NULL).
  185  *    flags  Any other flags to be passed to the provided mbuf.
  186  *    type   The type that the external storage buffer should be
  187  *           labeled with.
  188  *
  189  * Returns:
  190  *    Nothing.
  191  */
  192 void
  193 m_extadd(struct mbuf *mb, caddr_t buf, u_int size,
  194     void (*freef)(void *, void *), void *args, int flags, int type)
  195 {
  196         u_int *ref_cnt = NULL;
  197 
  198         /* XXX Shouldn't be adding EXT_CLUSTER with this API */
  199         if (type == EXT_CLUSTER)
  200                 ref_cnt = (u_int *)uma_find_refcnt(zone_clust,
  201                     mb->m_ext.ext_buf);
  202         else if (type == EXT_EXTREF)
  203                 ref_cnt = __DEVOLATILE(u_int *, mb->m_ext.ref_cnt);
  204         mb->m_ext.ref_cnt = (ref_cnt == NULL) ?
  205             malloc(sizeof(u_int), M_MBUF, M_NOWAIT) : (u_int *)ref_cnt;
  206         if (mb->m_ext.ref_cnt != NULL) {
  207                 *(mb->m_ext.ref_cnt) = 1;
  208                 mb->m_flags |= (M_EXT | flags);
  209                 mb->m_ext.ext_buf = buf;
  210                 mb->m_data = mb->m_ext.ext_buf;
  211                 mb->m_ext.ext_size = size;
  212                 mb->m_ext.ext_free = freef;
  213                 mb->m_ext.ext_args = args;
  214                 mb->m_ext.ext_type = type;
  215         }
  216 }
  217 
  218 /*
  219  * Non-directly-exported function to clean up after mbufs with M_EXT
  220  * storage attached to them if the reference count hits 0.
  221  */
  222 void
  223 mb_free_ext(struct mbuf *m)
  224 {
  225         u_int cnt;
  226         int dofree;
  227 
  228         /* Account for lazy ref count assign. */
  229         if (m->m_ext.ref_cnt == NULL)
  230                 dofree = 1;
  231         else
  232                 dofree = 0;
  233 
  234         /*
  235          * This is tricky.  We need to make sure to decrement the
  236          * refcount in a safe way but to also clean up if we're the
  237          * last reference.  This method seems to do it without race.
  238          */
  239         while (dofree == 0) {
  240                 cnt = *(m->m_ext.ref_cnt);
  241                 if (atomic_cmpset_int(m->m_ext.ref_cnt, cnt, cnt - 1)) {
  242                         if (cnt == 1)
  243                                 dofree = 1;
  244                         break;
  245                 }
  246         }
  247 
  248         if (dofree) {
  249                 /*
  250                  * Do the free, should be safe.
  251                  */
  252                 switch (m->m_ext.ext_type) {
  253                 case EXT_PACKET:
  254                         uma_zfree(zone_pack, m);
  255                         return;
  256                 case EXT_CLUSTER:
  257                         uma_zfree(zone_clust, m->m_ext.ext_buf);
  258                         m->m_ext.ext_buf = NULL;
  259                         break;
  260                 case EXT_JUMBOP:
  261                         uma_zfree(zone_jumbop, m->m_ext.ext_buf);
  262                         break;
  263                 case EXT_JUMBO9:
  264                         uma_zfree(zone_jumbo9, m->m_ext.ext_buf);
  265                         break;
  266                 case EXT_JUMBO16:
  267                         uma_zfree(zone_jumbo16, m->m_ext.ext_buf);
  268                         break;
  269                 default:
  270                         KASSERT(m->m_ext.ext_free != NULL,
  271                             ("%s: external free pointer not set", __func__));
  272                         (*(m->m_ext.ext_free))(m->m_ext.ext_buf,
  273                             m->m_ext.ext_args);
  274                         if (m->m_ext.ext_type != EXT_EXTREF) {
  275                                 if (m->m_ext.ref_cnt != NULL)
  276                                         free(__DEVOLATILE(u_int *,
  277                                             m->m_ext.ref_cnt), M_MBUF);
  278                                 m->m_ext.ref_cnt = NULL;
  279                         }
  280                         m->m_ext.ext_buf = NULL;
  281                 }
  282         }
  283         uma_zfree(zone_mbuf, m);
  284 }
  285 
  286 /*
  287  * "Move" mbuf pkthdr from "from" to "to".
  288  * "from" must have M_PKTHDR set, and "to" must be empty.
  289  */
  290 void
  291 m_move_pkthdr(struct mbuf *to, struct mbuf *from)
  292 {
  293 
  294 #if 0
  295         /* see below for why these are not enabled */
  296         M_ASSERTPKTHDR(to);
  297         /* Note: with MAC, this may not be a good assertion. */
  298         KASSERT(SLIST_EMPTY(&to->m_pkthdr.tags),
  299             ("m_move_pkthdr: to has tags"));
  300 #endif
  301 #ifdef MAC
  302         /*
  303          * XXXMAC: It could be this should also occur for non-MAC?
  304          */
  305         if (to->m_flags & M_PKTHDR)
  306                 m_tag_delete_chain(to, NULL);
  307 #endif
  308         to->m_flags = (from->m_flags & M_COPYFLAGS) | (to->m_flags & M_EXT);
  309         if ((to->m_flags & M_EXT) == 0)
  310                 to->m_data = to->m_pktdat;
  311         to->m_pkthdr = from->m_pkthdr;          /* especially tags */
  312         SLIST_INIT(&from->m_pkthdr.tags);       /* purge tags from src */
  313         from->m_flags &= ~M_PKTHDR;
  314 }
  315 
  316 /*
  317  * Duplicate "from"'s mbuf pkthdr in "to".
  318  * "from" must have M_PKTHDR set, and "to" must be empty.
  319  * In particular, this does a deep copy of the packet tags.
  320  */
  321 int
  322 m_dup_pkthdr(struct mbuf *to, struct mbuf *from, int how)
  323 {
  324 
  325 #if 0
  326         /*
  327          * The mbuf allocator only initializes the pkthdr
  328          * when the mbuf is allocated with MGETHDR. Many users
  329          * (e.g. m_copy*, m_prepend) use MGET and then
  330          * smash the pkthdr as needed causing these
  331          * assertions to trip.  For now just disable them.
  332          */
  333         M_ASSERTPKTHDR(to);
  334         /* Note: with MAC, this may not be a good assertion. */
  335         KASSERT(SLIST_EMPTY(&to->m_pkthdr.tags), ("m_dup_pkthdr: to has tags"));
  336 #endif
  337         MBUF_CHECKSLEEP(how);
  338 #ifdef MAC
  339         if (to->m_flags & M_PKTHDR)
  340                 m_tag_delete_chain(to, NULL);
  341 #endif
  342         to->m_flags = (from->m_flags & M_COPYFLAGS) | (to->m_flags & M_EXT);
  343         if ((to->m_flags & M_EXT) == 0)
  344                 to->m_data = to->m_pktdat;
  345         to->m_pkthdr = from->m_pkthdr;
  346         SLIST_INIT(&to->m_pkthdr.tags);
  347         return (m_tag_copy_chain(to, from, MBTOM(how)));
  348 }
  349 
  350 /*
  351  * Lesser-used path for M_PREPEND:
  352  * allocate new mbuf to prepend to chain,
  353  * copy junk along.
  354  */
  355 struct mbuf *
  356 m_prepend(struct mbuf *m, int len, int how)
  357 {
  358         struct mbuf *mn;
  359 
  360         if (m->m_flags & M_PKTHDR)
  361                 MGETHDR(mn, how, m->m_type);
  362         else
  363                 MGET(mn, how, m->m_type);
  364         if (mn == NULL) {
  365                 m_freem(m);
  366                 return (NULL);
  367         }
  368         if (m->m_flags & M_PKTHDR)
  369                 M_MOVE_PKTHDR(mn, m);
  370         mn->m_next = m;
  371         m = mn;
  372         if (len < MHLEN)
  373                 MH_ALIGN(m, len);
  374         m->m_len = len;
  375         return (m);
  376 }
  377 
  378 /*
  379  * Make a copy of an mbuf chain starting "off0" bytes from the beginning,
  380  * continuing for "len" bytes.  If len is M_COPYALL, copy to end of mbuf.
  381  * The wait parameter is a choice of M_TRYWAIT/M_DONTWAIT from caller.
  382  * Note that the copy is read-only, because clusters are not copied,
  383  * only their reference counts are incremented.
  384  */
  385 struct mbuf *
  386 m_copym(struct mbuf *m, int off0, int len, int wait)
  387 {
  388         struct mbuf *n, **np;
  389         int off = off0;
  390         struct mbuf *top;
  391         int copyhdr = 0;
  392 
  393         KASSERT(off >= 0, ("m_copym, negative off %d", off));
  394         KASSERT(len >= 0, ("m_copym, negative len %d", len));
  395         MBUF_CHECKSLEEP(wait);
  396         if (off == 0 && m->m_flags & M_PKTHDR)
  397                 copyhdr = 1;
  398         while (off > 0) {
  399                 KASSERT(m != NULL, ("m_copym, offset > size of mbuf chain"));
  400                 if (off < m->m_len)
  401                         break;
  402                 off -= m->m_len;
  403                 m = m->m_next;
  404         }
  405         np = &top;
  406         top = 0;
  407         while (len > 0) {
  408                 if (m == NULL) {
  409                         KASSERT(len == M_COPYALL, 
  410                             ("m_copym, length > size of mbuf chain"));
  411                         break;
  412                 }
  413                 if (copyhdr)
  414                         MGETHDR(n, wait, m->m_type);
  415                 else
  416                         MGET(n, wait, m->m_type);
  417                 *np = n;
  418                 if (n == NULL)
  419                         goto nospace;
  420                 if (copyhdr) {
  421                         if (!m_dup_pkthdr(n, m, wait))
  422                                 goto nospace;
  423                         if (len == M_COPYALL)
  424                                 n->m_pkthdr.len -= off0;
  425                         else
  426                                 n->m_pkthdr.len = len;
  427                         copyhdr = 0;
  428                 }
  429                 n->m_len = min(len, m->m_len - off);
  430                 if (m->m_flags & M_EXT) {
  431                         n->m_data = m->m_data + off;
  432                         n->m_ext = m->m_ext;
  433                         n->m_flags |= M_EXT;
  434                         MEXT_ADD_REF(m);
  435                         n->m_ext.ref_cnt = m->m_ext.ref_cnt;
  436                 } else
  437                         bcopy(mtod(m, caddr_t)+off, mtod(n, caddr_t),
  438                             (u_int)n->m_len);
  439                 if (len != M_COPYALL)
  440                         len -= n->m_len;
  441                 off = 0;
  442                 m = m->m_next;
  443                 np = &n->m_next;
  444         }
  445         if (top == NULL)
  446                 mbstat.m_mcfail++;      /* XXX: No consistency. */
  447 
  448         return (top);
  449 nospace:
  450         m_freem(top);
  451         mbstat.m_mcfail++;      /* XXX: No consistency. */
  452         return (NULL);
  453 }
  454 
  455 /*
  456  * Copy an entire packet, including header (which must be present).
  457  * An optimization of the common case `m_copym(m, 0, M_COPYALL, how)'.
  458  * Note that the copy is read-only, because clusters are not copied,
  459  * only their reference counts are incremented.
  460  * Preserve alignment of the first mbuf so if the creator has left
  461  * some room at the beginning (e.g. for inserting protocol headers)
  462  * the copies still have the room available.
  463  */
  464 struct mbuf *
  465 m_copypacket(struct mbuf *m, int how)
  466 {
  467         struct mbuf *top, *n, *o;
  468 
  469         MBUF_CHECKSLEEP(how);
  470         MGET(n, how, m->m_type);
  471         top = n;
  472         if (n == NULL)
  473                 goto nospace;
  474 
  475         if (!m_dup_pkthdr(n, m, how))
  476                 goto nospace;
  477         n->m_len = m->m_len;
  478         if (m->m_flags & M_EXT) {
  479                 n->m_data = m->m_data;
  480                 n->m_ext = m->m_ext;
  481                 n->m_flags |= M_EXT;
  482                 MEXT_ADD_REF(m);
  483                 n->m_ext.ref_cnt = m->m_ext.ref_cnt;
  484         } else {
  485                 n->m_data = n->m_pktdat + (m->m_data - m->m_pktdat );
  486                 bcopy(mtod(m, char *), mtod(n, char *), n->m_len);
  487         }
  488 
  489         m = m->m_next;
  490         while (m) {
  491                 MGET(o, how, m->m_type);
  492                 if (o == NULL)
  493                         goto nospace;
  494 
  495                 n->m_next = o;
  496                 n = n->m_next;
  497 
  498                 n->m_len = m->m_len;
  499                 if (m->m_flags & M_EXT) {
  500                         n->m_data = m->m_data;
  501                         n->m_ext = m->m_ext;
  502                         n->m_flags |= M_EXT;
  503                         MEXT_ADD_REF(m);
  504                         n->m_ext.ref_cnt = m->m_ext.ref_cnt;
  505                 } else {
  506                         bcopy(mtod(m, char *), mtod(n, char *), n->m_len);
  507                 }
  508 
  509                 m = m->m_next;
  510         }
  511         return top;
  512 nospace:
  513         m_freem(top);
  514         mbstat.m_mcfail++;      /* XXX: No consistency. */ 
  515         return (NULL);
  516 }
  517 
  518 /*
  519  * Copy data from an mbuf chain starting "off" bytes from the beginning,
  520  * continuing for "len" bytes, into the indicated buffer.
  521  */
  522 void
  523 m_copydata(const struct mbuf *m, int off, int len, caddr_t cp)
  524 {
  525         u_int count;
  526 
  527         KASSERT(off >= 0, ("m_copydata, negative off %d", off));
  528         KASSERT(len >= 0, ("m_copydata, negative len %d", len));
  529         while (off > 0) {
  530                 KASSERT(m != NULL, ("m_copydata, offset > size of mbuf chain"));
  531                 if (off < m->m_len)
  532                         break;
  533                 off -= m->m_len;
  534                 m = m->m_next;
  535         }
  536         while (len > 0) {
  537                 KASSERT(m != NULL, ("m_copydata, length > size of mbuf chain"));
  538                 count = min(m->m_len - off, len);
  539                 bcopy(mtod(m, caddr_t) + off, cp, count);
  540                 len -= count;
  541                 cp += count;
  542                 off = 0;
  543                 m = m->m_next;
  544         }
  545 }
  546 
  547 /*
  548  * Copy a packet header mbuf chain into a completely new chain, including
  549  * copying any mbuf clusters.  Use this instead of m_copypacket() when
  550  * you need a writable copy of an mbuf chain.
  551  */
  552 struct mbuf *
  553 m_dup(struct mbuf *m, int how)
  554 {
  555         struct mbuf **p, *top = NULL;
  556         int remain, moff, nsize;
  557 
  558         MBUF_CHECKSLEEP(how);
  559         /* Sanity check */
  560         if (m == NULL)
  561                 return (NULL);
  562         M_ASSERTPKTHDR(m);
  563 
  564         /* While there's more data, get a new mbuf, tack it on, and fill it */
  565         remain = m->m_pkthdr.len;
  566         moff = 0;
  567         p = &top;
  568         while (remain > 0 || top == NULL) {     /* allow m->m_pkthdr.len == 0 */
  569                 struct mbuf *n;
  570 
  571                 /* Get the next new mbuf */
  572                 if (remain >= MINCLSIZE) {
  573                         n = m_getcl(how, m->m_type, 0);
  574                         nsize = MCLBYTES;
  575                 } else {
  576                         n = m_get(how, m->m_type);
  577                         nsize = MLEN;
  578                 }
  579                 if (n == NULL)
  580                         goto nospace;
  581 
  582                 if (top == NULL) {              /* First one, must be PKTHDR */
  583                         if (!m_dup_pkthdr(n, m, how)) {
  584                                 m_free(n);
  585                                 goto nospace;
  586                         }
  587                         if ((n->m_flags & M_EXT) == 0)
  588                                 nsize = MHLEN;
  589                 }
  590                 n->m_len = 0;
  591 
  592                 /* Link it into the new chain */
  593                 *p = n;
  594                 p = &n->m_next;
  595 
  596                 /* Copy data from original mbuf(s) into new mbuf */
  597                 while (n->m_len < nsize && m != NULL) {
  598                         int chunk = min(nsize - n->m_len, m->m_len - moff);
  599 
  600                         bcopy(m->m_data + moff, n->m_data + n->m_len, chunk);
  601                         moff += chunk;
  602                         n->m_len += chunk;
  603                         remain -= chunk;
  604                         if (moff == m->m_len) {
  605                                 m = m->m_next;
  606                                 moff = 0;
  607                         }
  608                 }
  609 
  610                 /* Check correct total mbuf length */
  611                 KASSERT((remain > 0 && m != NULL) || (remain == 0 && m == NULL),
  612                         ("%s: bogus m_pkthdr.len", __func__));
  613         }
  614         return (top);
  615 
  616 nospace:
  617         m_freem(top);
  618         mbstat.m_mcfail++;      /* XXX: No consistency. */
  619         return (NULL);
  620 }
  621 
  622 /*
  623  * Concatenate mbuf chain n to m.
  624  * Both chains must be of the same type (e.g. MT_DATA).
  625  * Any m_pkthdr is not updated.
  626  */
  627 void
  628 m_cat(struct mbuf *m, struct mbuf *n)
  629 {
  630         while (m->m_next)
  631                 m = m->m_next;
  632         while (n) {
  633                 if (m->m_flags & M_EXT ||
  634                     m->m_data + m->m_len + n->m_len >= &m->m_dat[MLEN]) {
  635                         /* just join the two chains */
  636                         m->m_next = n;
  637                         return;
  638                 }
  639                 /* splat the data from one into the other */
  640                 bcopy(mtod(n, caddr_t), mtod(m, caddr_t) + m->m_len,
  641                     (u_int)n->m_len);
  642                 m->m_len += n->m_len;
  643                 n = m_free(n);
  644         }
  645 }
  646 
  647 void
  648 m_adj(struct mbuf *mp, int req_len)
  649 {
  650         int len = req_len;
  651         struct mbuf *m;
  652         int count;
  653 
  654         if ((m = mp) == NULL)
  655                 return;
  656         if (len >= 0) {
  657                 /*
  658                  * Trim from head.
  659                  */
  660                 while (m != NULL && len > 0) {
  661                         if (m->m_len <= len) {
  662                                 len -= m->m_len;
  663                                 m->m_len = 0;
  664                                 m = m->m_next;
  665                         } else {
  666                                 m->m_len -= len;
  667                                 m->m_data += len;
  668                                 len = 0;
  669                         }
  670                 }
  671                 m = mp;
  672                 if (mp->m_flags & M_PKTHDR)
  673                         m->m_pkthdr.len -= (req_len - len);
  674         } else {
  675                 /*
  676                  * Trim from tail.  Scan the mbuf chain,
  677                  * calculating its length and finding the last mbuf.
  678                  * If the adjustment only affects this mbuf, then just
  679                  * adjust and return.  Otherwise, rescan and truncate
  680                  * after the remaining size.
  681                  */
  682                 len = -len;
  683                 count = 0;
  684                 for (;;) {
  685                         count += m->m_len;
  686                         if (m->m_next == (struct mbuf *)0)
  687                                 break;
  688                         m = m->m_next;
  689                 }
  690                 if (m->m_len >= len) {
  691                         m->m_len -= len;
  692                         if (mp->m_flags & M_PKTHDR)
  693                                 mp->m_pkthdr.len -= len;
  694                         return;
  695                 }
  696                 count -= len;
  697                 if (count < 0)
  698                         count = 0;
  699                 /*
  700                  * Correct length for chain is "count".
  701                  * Find the mbuf with last data, adjust its length,
  702                  * and toss data from remaining mbufs on chain.
  703                  */
  704                 m = mp;
  705                 if (m->m_flags & M_PKTHDR)
  706                         m->m_pkthdr.len = count;
  707                 for (; m; m = m->m_next) {
  708                         if (m->m_len >= count) {
  709                                 m->m_len = count;
  710                                 if (m->m_next != NULL) {
  711                                         m_freem(m->m_next);
  712                                         m->m_next = NULL;
  713                                 }
  714                                 break;
  715                         }
  716                         count -= m->m_len;
  717                 }
  718         }
  719 }
  720 
  721 /*
  722  * Rearange an mbuf chain so that len bytes are contiguous
  723  * and in the data area of an mbuf (so that mtod and dtom
  724  * will work for a structure of size len).  Returns the resulting
  725  * mbuf chain on success, frees it and returns null on failure.
  726  * If there is room, it will add up to max_protohdr-len extra bytes to the
  727  * contiguous region in an attempt to avoid being called next time.
  728  */
  729 struct mbuf *
  730 m_pullup(struct mbuf *n, int len)
  731 {
  732         struct mbuf *m;
  733         int count;
  734         int space;
  735 
  736         /*
  737          * If first mbuf has no cluster, and has room for len bytes
  738          * without shifting current data, pullup into it,
  739          * otherwise allocate a new mbuf to prepend to the chain.
  740          */
  741         if ((n->m_flags & M_EXT) == 0 &&
  742             n->m_data + len < &n->m_dat[MLEN] && n->m_next) {
  743                 if (n->m_len >= len)
  744                         return (n);
  745                 m = n;
  746                 n = n->m_next;
  747                 len -= m->m_len;
  748         } else {
  749                 if (len > MHLEN)
  750                         goto bad;
  751                 MGET(m, M_DONTWAIT, n->m_type);
  752                 if (m == NULL)
  753                         goto bad;
  754                 m->m_len = 0;
  755                 if (n->m_flags & M_PKTHDR)
  756                         M_MOVE_PKTHDR(m, n);
  757         }
  758         space = &m->m_dat[MLEN] - (m->m_data + m->m_len);
  759         do {
  760                 count = min(min(max(len, max_protohdr), space), n->m_len);
  761                 bcopy(mtod(n, caddr_t), mtod(m, caddr_t) + m->m_len,
  762                   (u_int)count);
  763                 len -= count;
  764                 m->m_len += count;
  765                 n->m_len -= count;
  766                 space -= count;
  767                 if (n->m_len)
  768                         n->m_data += count;
  769                 else
  770                         n = m_free(n);
  771         } while (len > 0 && n);
  772         if (len > 0) {
  773                 (void) m_free(m);
  774                 goto bad;
  775         }
  776         m->m_next = n;
  777         return (m);
  778 bad:
  779         m_freem(n);
  780         mbstat.m_mpfail++;      /* XXX: No consistency. */
  781         return (NULL);
  782 }
  783 
  784 /*
  785  * Like m_pullup(), except a new mbuf is always allocated, and we allow
  786  * the amount of empty space before the data in the new mbuf to be specified
  787  * (in the event that the caller expects to prepend later).
  788  */
  789 int MSFail;
  790 
  791 struct mbuf *
  792 m_copyup(struct mbuf *n, int len, int dstoff)
  793 {
  794         struct mbuf *m;
  795         int count, space;
  796 
  797         if (len > (MHLEN - dstoff))
  798                 goto bad;
  799         MGET(m, M_DONTWAIT, n->m_type);
  800         if (m == NULL)
  801                 goto bad;
  802         m->m_len = 0;
  803         if (n->m_flags & M_PKTHDR)
  804                 M_MOVE_PKTHDR(m, n);
  805         m->m_data += dstoff;
  806         space = &m->m_dat[MLEN] - (m->m_data + m->m_len);
  807         do {
  808                 count = min(min(max(len, max_protohdr), space), n->m_len);
  809                 memcpy(mtod(m, caddr_t) + m->m_len, mtod(n, caddr_t),
  810                     (unsigned)count);
  811                 len -= count;
  812                 m->m_len += count;
  813                 n->m_len -= count;
  814                 space -= count;
  815                 if (n->m_len)
  816                         n->m_data += count;
  817                 else
  818                         n = m_free(n);
  819         } while (len > 0 && n);
  820         if (len > 0) {
  821                 (void) m_free(m);
  822                 goto bad;
  823         }
  824         m->m_next = n;
  825         return (m);
  826  bad:
  827         m_freem(n);
  828         MSFail++;
  829         return (NULL);
  830 }
  831 
  832 /*
  833  * Partition an mbuf chain in two pieces, returning the tail --
  834  * all but the first len0 bytes.  In case of failure, it returns NULL and
  835  * attempts to restore the chain to its original state.
  836  *
  837  * Note that the resulting mbufs might be read-only, because the new
  838  * mbuf can end up sharing an mbuf cluster with the original mbuf if
  839  * the "breaking point" happens to lie within a cluster mbuf. Use the
  840  * M_WRITABLE() macro to check for this case.
  841  */
  842 struct mbuf *
  843 m_split(struct mbuf *m0, int len0, int wait)
  844 {
  845         struct mbuf *m, *n;
  846         u_int len = len0, remain;
  847 
  848         MBUF_CHECKSLEEP(wait);
  849         for (m = m0; m && len > m->m_len; m = m->m_next)
  850                 len -= m->m_len;
  851         if (m == NULL)
  852                 return (NULL);
  853         remain = m->m_len - len;
  854         if (m0->m_flags & M_PKTHDR) {
  855                 MGETHDR(n, wait, m0->m_type);
  856                 if (n == NULL)
  857                         return (NULL);
  858                 n->m_pkthdr.rcvif = m0->m_pkthdr.rcvif;
  859                 n->m_pkthdr.len = m0->m_pkthdr.len - len0;
  860                 m0->m_pkthdr.len = len0;
  861                 if (m->m_flags & M_EXT)
  862                         goto extpacket;
  863                 if (remain > MHLEN) {
  864                         /* m can't be the lead packet */
  865                         MH_ALIGN(n, 0);
  866                         n->m_next = m_split(m, len, wait);
  867                         if (n->m_next == NULL) {
  868                                 (void) m_free(n);
  869                                 return (NULL);
  870                         } else {
  871                                 n->m_len = 0;
  872                                 return (n);
  873                         }
  874                 } else
  875                         MH_ALIGN(n, remain);
  876         } else if (remain == 0) {
  877                 n = m->m_next;
  878                 m->m_next = NULL;
  879                 return (n);
  880         } else {
  881                 MGET(n, wait, m->m_type);
  882                 if (n == NULL)
  883                         return (NULL);
  884                 M_ALIGN(n, remain);
  885         }
  886 extpacket:
  887         if (m->m_flags & M_EXT) {
  888                 n->m_flags |= M_EXT;
  889                 n->m_ext = m->m_ext;
  890                 MEXT_ADD_REF(m);
  891                 n->m_ext.ref_cnt = m->m_ext.ref_cnt;
  892                 n->m_data = m->m_data + len;
  893         } else {
  894                 bcopy(mtod(m, caddr_t) + len, mtod(n, caddr_t), remain);
  895         }
  896         n->m_len = remain;
  897         m->m_len = len;
  898         n->m_next = m->m_next;
  899         m->m_next = NULL;
  900         return (n);
  901 }
  902 /*
  903  * Routine to copy from device local memory into mbufs.
  904  * Note that `off' argument is offset into first mbuf of target chain from
  905  * which to begin copying the data to.
  906  */
  907 struct mbuf *
  908 m_devget(char *buf, int totlen, int off, struct ifnet *ifp,
  909          void (*copy)(char *from, caddr_t to, u_int len))
  910 {
  911         struct mbuf *m;
  912         struct mbuf *top = NULL, **mp = &top;
  913         int len;
  914 
  915         if (off < 0 || off > MHLEN)
  916                 return (NULL);
  917 
  918         while (totlen > 0) {
  919                 if (top == NULL) {      /* First one, must be PKTHDR */
  920                         if (totlen + off >= MINCLSIZE) {
  921                                 m = m_getcl(M_DONTWAIT, MT_DATA, M_PKTHDR);
  922                                 len = MCLBYTES;
  923                         } else {
  924                                 m = m_gethdr(M_DONTWAIT, MT_DATA);
  925                                 len = MHLEN;
  926 
  927                                 /* Place initial small packet/header at end of mbuf */
  928                                 if (m && totlen + off + max_linkhdr <= MLEN) {
  929                                         m->m_data += max_linkhdr;
  930                                         len -= max_linkhdr;
  931                                 }
  932                         }
  933                         if (m == NULL)
  934                                 return NULL;
  935                         m->m_pkthdr.rcvif = ifp;
  936                         m->m_pkthdr.len = totlen;
  937                 } else {
  938                         if (totlen + off >= MINCLSIZE) {
  939                                 m = m_getcl(M_DONTWAIT, MT_DATA, 0);
  940                                 len = MCLBYTES;
  941                         } else {
  942                                 m = m_get(M_DONTWAIT, MT_DATA);
  943                                 len = MLEN;
  944                         }
  945                         if (m == NULL) {
  946                                 m_freem(top);
  947                                 return NULL;
  948                         }
  949                 }
  950                 if (off) {
  951                         m->m_data += off;
  952                         len -= off;
  953                         off = 0;
  954                 }
  955                 m->m_len = len = min(totlen, len);
  956                 if (copy)
  957                         copy(buf, mtod(m, caddr_t), (u_int)len);
  958                 else
  959                         bcopy(buf, mtod(m, caddr_t), (u_int)len);
  960                 buf += len;
  961                 *mp = m;
  962                 mp = &m->m_next;
  963                 totlen -= len;
  964         }
  965         return (top);
  966 }
  967 
  968 /*
  969  * Copy data from a buffer back into the indicated mbuf chain,
  970  * starting "off" bytes from the beginning, extending the mbuf
  971  * chain if necessary.
  972  */
  973 void
  974 m_copyback(struct mbuf *m0, int off, int len, c_caddr_t cp)
  975 {
  976         int mlen;
  977         struct mbuf *m = m0, *n;
  978         int totlen = 0;
  979 
  980         if (m0 == NULL)
  981                 return;
  982         while (off > (mlen = m->m_len)) {
  983                 off -= mlen;
  984                 totlen += mlen;
  985                 if (m->m_next == NULL) {
  986                         n = m_get(M_DONTWAIT, m->m_type);
  987                         if (n == NULL)
  988                                 goto out;
  989                         bzero(mtod(n, caddr_t), MLEN);
  990                         n->m_len = min(MLEN, len + off);
  991                         m->m_next = n;
  992                 }
  993                 m = m->m_next;
  994         }
  995         while (len > 0) {
  996                 mlen = min (m->m_len - off, len);
  997                 bcopy(cp, off + mtod(m, caddr_t), (u_int)mlen);
  998                 cp += mlen;
  999                 len -= mlen;
 1000                 mlen += off;
 1001                 off = 0;
 1002                 totlen += mlen;
 1003                 if (len == 0)
 1004                         break;
 1005                 if (m->m_next == NULL) {
 1006                         n = m_get(M_DONTWAIT, m->m_type);
 1007                         if (n == NULL)
 1008                                 break;
 1009                         n->m_len = min(MLEN, len);
 1010                         m->m_next = n;
 1011                 }
 1012                 m = m->m_next;
 1013         }
 1014 out:    if (((m = m0)->m_flags & M_PKTHDR) && (m->m_pkthdr.len < totlen))
 1015                 m->m_pkthdr.len = totlen;
 1016 }
 1017 
 1018 /*
 1019  * Append the specified data to the indicated mbuf chain,
 1020  * Extend the mbuf chain if the new data does not fit in
 1021  * existing space.
 1022  *
 1023  * Return 1 if able to complete the job; otherwise 0.
 1024  */
 1025 int
 1026 m_append(struct mbuf *m0, int len, c_caddr_t cp)
 1027 {
 1028         struct mbuf *m, *n;
 1029         int remainder, space;
 1030 
 1031         for (m = m0; m->m_next != NULL; m = m->m_next)
 1032                 ;
 1033         remainder = len;
 1034         space = M_TRAILINGSPACE(m);
 1035         if (space > 0) {
 1036                 /*
 1037                  * Copy into available space.
 1038                  */
 1039                 if (space > remainder)
 1040                         space = remainder;
 1041                 bcopy(cp, mtod(m, caddr_t) + m->m_len, space);
 1042                 m->m_len += space;
 1043                 cp += space, remainder -= space;
 1044         }
 1045         while (remainder > 0) {
 1046                 /*
 1047                  * Allocate a new mbuf; could check space
 1048                  * and allocate a cluster instead.
 1049                  */
 1050                 n = m_get(M_DONTWAIT, m->m_type);
 1051                 if (n == NULL)
 1052                         break;
 1053                 n->m_len = min(MLEN, remainder);
 1054                 bcopy(cp, mtod(n, caddr_t), n->m_len);
 1055                 cp += n->m_len, remainder -= n->m_len;
 1056                 m->m_next = n;
 1057                 m = n;
 1058         }
 1059         if (m0->m_flags & M_PKTHDR)
 1060                 m0->m_pkthdr.len += len - remainder;
 1061         return (remainder == 0);
 1062 }
 1063 
 1064 /*
 1065  * Apply function f to the data in an mbuf chain starting "off" bytes from
 1066  * the beginning, continuing for "len" bytes.
 1067  */
 1068 int
 1069 m_apply(struct mbuf *m, int off, int len,
 1070     int (*f)(void *, void *, u_int), void *arg)
 1071 {
 1072         u_int count;
 1073         int rval;
 1074 
 1075         KASSERT(off >= 0, ("m_apply, negative off %d", off));
 1076         KASSERT(len >= 0, ("m_apply, negative len %d", len));
 1077         while (off > 0) {
 1078                 KASSERT(m != NULL, ("m_apply, offset > size of mbuf chain"));
 1079                 if (off < m->m_len)
 1080                         break;
 1081                 off -= m->m_len;
 1082                 m = m->m_next;
 1083         }
 1084         while (len > 0) {
 1085                 KASSERT(m != NULL, ("m_apply, offset > size of mbuf chain"));
 1086                 count = min(m->m_len - off, len);
 1087                 rval = (*f)(arg, mtod(m, caddr_t) + off, count);
 1088                 if (rval)
 1089                         return (rval);
 1090                 len -= count;
 1091                 off = 0;
 1092                 m = m->m_next;
 1093         }
 1094         return (0);
 1095 }
 1096 
 1097 /*
 1098  * Return a pointer to mbuf/offset of location in mbuf chain.
 1099  */
 1100 struct mbuf *
 1101 m_getptr(struct mbuf *m, int loc, int *off)
 1102 {
 1103 
 1104         while (loc >= 0) {
 1105                 /* Normal end of search. */
 1106                 if (m->m_len > loc) {
 1107                         *off = loc;
 1108                         return (m);
 1109                 } else {
 1110                         loc -= m->m_len;
 1111                         if (m->m_next == NULL) {
 1112                                 if (loc == 0) {
 1113                                         /* Point at the end of valid data. */
 1114                                         *off = m->m_len;
 1115                                         return (m);
 1116                                 }
 1117                                 return (NULL);
 1118                         }
 1119                         m = m->m_next;
 1120                 }
 1121         }
 1122         return (NULL);
 1123 }
 1124 
 1125 void
 1126 m_print(const struct mbuf *m, int maxlen)
 1127 {
 1128         int len;
 1129         int pdata;
 1130         const struct mbuf *m2;
 1131 
 1132         if (m->m_flags & M_PKTHDR)
 1133                 len = m->m_pkthdr.len;
 1134         else
 1135                 len = -1;
 1136         m2 = m;
 1137         while (m2 != NULL && (len == -1 || len)) {
 1138                 pdata = m2->m_len;
 1139                 if (maxlen != -1 && pdata > maxlen)
 1140                         pdata = maxlen;
 1141                 printf("mbuf: %p len: %d, next: %p, %b%s", m2, m2->m_len,
 1142                     m2->m_next, m2->m_flags, "\2\20freelist\17skipfw"
 1143                     "\11proto5\10proto4\7proto3\6proto2\5proto1\4rdonly"
 1144                     "\3eor\2pkthdr\1ext", pdata ? "" : "\n");
 1145                 if (pdata)
 1146                         printf(", %*D\n", m2->m_len, (u_char *)m2->m_data, "-");
 1147                 if (len != -1)
 1148                         len -= m2->m_len;
 1149                 m2 = m2->m_next;
 1150         }
 1151         if (len > 0)
 1152                 printf("%d bytes unaccounted for.\n", len);
 1153         return;
 1154 }
 1155 
 1156 u_int
 1157 m_fixhdr(struct mbuf *m0)
 1158 {
 1159         u_int len;
 1160 
 1161         len = m_length(m0, NULL);
 1162         m0->m_pkthdr.len = len;
 1163         return (len);
 1164 }
 1165 
 1166 u_int
 1167 m_length(struct mbuf *m0, struct mbuf **last)
 1168 {
 1169         struct mbuf *m;
 1170         u_int len;
 1171 
 1172         len = 0;
 1173         for (m = m0; m != NULL; m = m->m_next) {
 1174                 len += m->m_len;
 1175                 if (m->m_next == NULL)
 1176                         break;
 1177         }
 1178         if (last != NULL)
 1179                 *last = m;
 1180         return (len);
 1181 }
 1182 
 1183 /*
 1184  * Defragment a mbuf chain, returning the shortest possible
 1185  * chain of mbufs and clusters.  If allocation fails and
 1186  * this cannot be completed, NULL will be returned, but
 1187  * the passed in chain will be unchanged.  Upon success,
 1188  * the original chain will be freed, and the new chain
 1189  * will be returned.
 1190  *
 1191  * If a non-packet header is passed in, the original
 1192  * mbuf (chain?) will be returned unharmed.
 1193  */
 1194 struct mbuf *
 1195 m_defrag(struct mbuf *m0, int how)
 1196 {
 1197         struct mbuf *m_new = NULL, *m_final = NULL;
 1198         int progress = 0, length;
 1199 
 1200         MBUF_CHECKSLEEP(how);
 1201         if (!(m0->m_flags & M_PKTHDR))
 1202                 return (m0);
 1203 
 1204         m_fixhdr(m0); /* Needed sanity check */
 1205 
 1206 #ifdef MBUF_STRESS_TEST
 1207         if (m_defragrandomfailures) {
 1208                 int temp = arc4random() & 0xff;
 1209                 if (temp == 0xba)
 1210                         goto nospace;
 1211         }
 1212 #endif
 1213         
 1214         if (m0->m_pkthdr.len > MHLEN)
 1215                 m_final = m_getcl(how, MT_DATA, M_PKTHDR);
 1216         else
 1217                 m_final = m_gethdr(how, MT_DATA);
 1218 
 1219         if (m_final == NULL)
 1220                 goto nospace;
 1221 
 1222         if (m_dup_pkthdr(m_final, m0, how) == 0)
 1223                 goto nospace;
 1224 
 1225         m_new = m_final;
 1226 
 1227         while (progress < m0->m_pkthdr.len) {
 1228                 length = m0->m_pkthdr.len - progress;
 1229                 if (length > MCLBYTES)
 1230                         length = MCLBYTES;
 1231 
 1232                 if (m_new == NULL) {
 1233                         if (length > MLEN)
 1234                                 m_new = m_getcl(how, MT_DATA, 0);
 1235                         else
 1236                                 m_new = m_get(how, MT_DATA);
 1237                         if (m_new == NULL)
 1238                                 goto nospace;
 1239                 }
 1240 
 1241                 m_copydata(m0, progress, length, mtod(m_new, caddr_t));
 1242                 progress += length;
 1243                 m_new->m_len = length;
 1244                 if (m_new != m_final)
 1245                         m_cat(m_final, m_new);
 1246                 m_new = NULL;
 1247         }
 1248 #ifdef MBUF_STRESS_TEST
 1249         if (m0->m_next == NULL)
 1250                 m_defraguseless++;
 1251 #endif
 1252         m_freem(m0);
 1253         m0 = m_final;
 1254 #ifdef MBUF_STRESS_TEST
 1255         m_defragpackets++;
 1256         m_defragbytes += m0->m_pkthdr.len;
 1257 #endif
 1258         return (m0);
 1259 nospace:
 1260 #ifdef MBUF_STRESS_TEST
 1261         m_defragfailure++;
 1262 #endif
 1263         if (m_final)
 1264                 m_freem(m_final);
 1265         return (NULL);
 1266 }
 1267 
 1268 #ifdef MBUF_STRESS_TEST
 1269 
 1270 /*
 1271  * Fragment an mbuf chain.  There's no reason you'd ever want to do
 1272  * this in normal usage, but it's great for stress testing various
 1273  * mbuf consumers.
 1274  *
 1275  * If fragmentation is not possible, the original chain will be
 1276  * returned.
 1277  *
 1278  * Possible length values:
 1279  * 0     no fragmentation will occur
 1280  * > 0  each fragment will be of the specified length
 1281  * -1   each fragment will be the same random value in length
 1282  * -2   each fragment's length will be entirely random
 1283  * (Random values range from 1 to 256)
 1284  */
 1285 struct mbuf *
 1286 m_fragment(struct mbuf *m0, int how, int length)
 1287 {
 1288         struct mbuf *m_new = NULL, *m_final = NULL;
 1289         int progress = 0;
 1290 
 1291         if (!(m0->m_flags & M_PKTHDR))
 1292                 return (m0);
 1293         
 1294         if ((length == 0) || (length < -2))
 1295                 return (m0);
 1296 
 1297         m_fixhdr(m0); /* Needed sanity check */
 1298 
 1299         m_final = m_getcl(how, MT_DATA, M_PKTHDR);
 1300 
 1301         if (m_final == NULL)
 1302                 goto nospace;
 1303 
 1304         if (m_dup_pkthdr(m_final, m0, how) == 0)
 1305                 goto nospace;
 1306 
 1307         m_new = m_final;
 1308 
 1309         if (length == -1)
 1310                 length = 1 + (arc4random() & 255);
 1311 
 1312         while (progress < m0->m_pkthdr.len) {
 1313                 int fraglen;
 1314 
 1315                 if (length > 0)
 1316                         fraglen = length;
 1317                 else
 1318                         fraglen = 1 + (arc4random() & 255);
 1319                 if (fraglen > m0->m_pkthdr.len - progress)
 1320                         fraglen = m0->m_pkthdr.len - progress;
 1321 
 1322                 if (fraglen > MCLBYTES)
 1323                         fraglen = MCLBYTES;
 1324 
 1325                 if (m_new == NULL) {
 1326                         m_new = m_getcl(how, MT_DATA, 0);
 1327                         if (m_new == NULL)
 1328                                 goto nospace;
 1329                 }
 1330 
 1331                 m_copydata(m0, progress, fraglen, mtod(m_new, caddr_t));
 1332                 progress += fraglen;
 1333                 m_new->m_len = fraglen;
 1334                 if (m_new != m_final)
 1335                         m_cat(m_final, m_new);
 1336                 m_new = NULL;
 1337         }
 1338         m_freem(m0);
 1339         m0 = m_final;
 1340         return (m0);
 1341 nospace:
 1342         if (m_final)
 1343                 m_freem(m_final);
 1344         /* Return the original chain on failure */
 1345         return (m0);
 1346 }
 1347 
 1348 #endif
 1349 
 1350 struct mbuf *
 1351 m_uiotombuf(struct uio *uio, int how, int len, int align)
 1352 {
 1353         struct mbuf *m_new = NULL, *m_final = NULL;
 1354         int progress = 0, error = 0, length, total;
 1355 
 1356         if (len > 0)
 1357                 total = min(uio->uio_resid, len);
 1358         else
 1359                 total = uio->uio_resid;
 1360         if (align >= MHLEN)
 1361                 goto nospace;
 1362         if (total + align > MHLEN)
 1363                 m_final = m_getcl(how, MT_DATA, M_PKTHDR);
 1364         else
 1365                 m_final = m_gethdr(how, MT_DATA);
 1366         if (m_final == NULL)
 1367                 goto nospace;
 1368         m_final->m_data += align;
 1369         m_new = m_final;
 1370         while (progress < total) {
 1371                 length = total - progress;
 1372                 if (length > MCLBYTES)
 1373                         length = MCLBYTES;
 1374                 if (m_new == NULL) {
 1375                         if (length > MLEN)
 1376                                 m_new = m_getcl(how, MT_DATA, 0);
 1377                         else
 1378                                 m_new = m_get(how, MT_DATA);
 1379                         if (m_new == NULL)
 1380                                 goto nospace;
 1381                 }
 1382                 error = uiomove(mtod(m_new, void *), length, uio);
 1383                 if (error)
 1384                         goto nospace;
 1385                 progress += length;
 1386                 m_new->m_len = length;
 1387                 if (m_new != m_final)
 1388                         m_cat(m_final, m_new);
 1389                 m_new = NULL;
 1390         }
 1391         m_fixhdr(m_final);
 1392         return (m_final);
 1393 nospace:
 1394         if (m_new)
 1395                 m_free(m_new);
 1396         if (m_final)
 1397                 m_freem(m_final);
 1398         return (NULL);
 1399 }
 1400 
 1401 /*
 1402  * Set the m_data pointer of a newly-allocated mbuf
 1403  * to place an object of the specified size at the
 1404  * end of the mbuf, longword aligned.
 1405  */
 1406 void
 1407 m_align(struct mbuf *m, int len)
 1408 {
 1409         int adjust;
 1410 
 1411         if (m->m_flags & M_EXT)
 1412                 adjust = m->m_ext.ext_size - len;
 1413         else if (m->m_flags & M_PKTHDR)
 1414                 adjust = MHLEN - len;
 1415         else
 1416                 adjust = MLEN - len;
 1417         m->m_data += adjust &~ (sizeof(long)-1);
 1418 }
 1419 
 1420 /*
 1421  * Create a writable copy of the mbuf chain.  While doing this
 1422  * we compact the chain with a goal of producing a chain with
 1423  * at most two mbufs.  The second mbuf in this chain is likely
 1424  * to be a cluster.  The primary purpose of this work is to create
 1425  * a writable packet for encryption, compression, etc.  The
 1426  * secondary goal is to linearize the data so the data can be
 1427  * passed to crypto hardware in the most efficient manner possible.
 1428  */
 1429 struct mbuf *
 1430 m_unshare(struct mbuf *m0, int how)
 1431 {
 1432         struct mbuf *m, *mprev;
 1433         struct mbuf *n, *mfirst, *mlast;
 1434         int len, off;
 1435 
 1436         mprev = NULL;
 1437         for (m = m0; m != NULL; m = mprev->m_next) {
 1438                 /*
 1439                  * Regular mbufs are ignored unless there's a cluster
 1440                  * in front of it that we can use to coalesce.  We do
 1441                  * the latter mainly so later clusters can be coalesced
 1442                  * also w/o having to handle them specially (i.e. convert
 1443                  * mbuf+cluster -> cluster).  This optimization is heavily
 1444                  * influenced by the assumption that we're running over
 1445                  * Ethernet where MCLBYTES is large enough that the max
 1446                  * packet size will permit lots of coalescing into a
 1447                  * single cluster.  This in turn permits efficient
 1448                  * crypto operations, especially when using hardware.
 1449                  */
 1450                 if ((m->m_flags & M_EXT) == 0) {
 1451                         if (mprev && (mprev->m_flags & M_EXT) &&
 1452                             m->m_len <= M_TRAILINGSPACE(mprev)) {
 1453                                 /* XXX: this ignores mbuf types */
 1454                                 memcpy(mtod(mprev, caddr_t) + mprev->m_len,
 1455                                        mtod(m, caddr_t), m->m_len);
 1456                                 mprev->m_len += m->m_len;
 1457                                 mprev->m_next = m->m_next;      /* unlink from chain */
 1458                                 m_free(m);                      /* reclaim mbuf */
 1459 #if 0
 1460                                 newipsecstat.ips_mbcoalesced++;
 1461 #endif
 1462                         } else {
 1463                                 mprev = m;
 1464                         }
 1465                         continue;
 1466                 }
 1467                 /*
 1468                  * Writable mbufs are left alone (for now).
 1469                  */
 1470                 if (M_WRITABLE(m)) {
 1471                         mprev = m;
 1472                         continue;
 1473                 }
 1474 
 1475                 /*
 1476                  * Not writable, replace with a copy or coalesce with
 1477                  * the previous mbuf if possible (since we have to copy
 1478                  * it anyway, we try to reduce the number of mbufs and
 1479                  * clusters so that future work is easier).
 1480                  */
 1481                 KASSERT(m->m_flags & M_EXT, ("m_flags 0x%x", m->m_flags));
 1482                 /* NB: we only coalesce into a cluster or larger */
 1483                 if (mprev != NULL && (mprev->m_flags & M_EXT) &&
 1484                     m->m_len <= M_TRAILINGSPACE(mprev)) {
 1485                         /* XXX: this ignores mbuf types */
 1486                         memcpy(mtod(mprev, caddr_t) + mprev->m_len,
 1487                                mtod(m, caddr_t), m->m_len);
 1488                         mprev->m_len += m->m_len;
 1489                         mprev->m_next = m->m_next;      /* unlink from chain */
 1490                         m_free(m);                      /* reclaim mbuf */
 1491 #if 0
 1492                         newipsecstat.ips_clcoalesced++;
 1493 #endif
 1494                         continue;
 1495                 }
 1496 
 1497                 /*
 1498                  * Allocate new space to hold the copy...
 1499                  */
 1500                 /* XXX why can M_PKTHDR be set past the first mbuf? */
 1501                 if (mprev == NULL && (m->m_flags & M_PKTHDR)) {
 1502                         /*
 1503                          * NB: if a packet header is present we must
 1504                          * allocate the mbuf separately from any cluster
 1505                          * because M_MOVE_PKTHDR will smash the data
 1506                          * pointer and drop the M_EXT marker.
 1507                          */
 1508                         MGETHDR(n, how, m->m_type);
 1509                         if (n == NULL) {
 1510                                 m_freem(m0);
 1511                                 return (NULL);
 1512                         }
 1513                         M_MOVE_PKTHDR(n, m);
 1514                         MCLGET(n, how);
 1515                         if ((n->m_flags & M_EXT) == 0) {
 1516                                 m_free(n);
 1517                                 m_freem(m0);
 1518                                 return (NULL);
 1519                         }
 1520                 } else {
 1521                         n = m_getcl(how, m->m_type, m->m_flags);
 1522                         if (n == NULL) {
 1523                                 m_freem(m0);
 1524                                 return (NULL);
 1525                         }
 1526                 }
 1527                 /*
 1528                  * ... and copy the data.  We deal with jumbo mbufs
 1529                  * (i.e. m_len > MCLBYTES) by splitting them into
 1530                  * clusters.  We could just malloc a buffer and make
 1531                  * it external but too many device drivers don't know
 1532                  * how to break up the non-contiguous memory when
 1533                  * doing DMA.
 1534                  */
 1535                 len = m->m_len;
 1536                 off = 0;
 1537                 mfirst = n;
 1538                 mlast = NULL;
 1539                 for (;;) {
 1540                         int cc = min(len, MCLBYTES);
 1541                         memcpy(mtod(n, caddr_t), mtod(m, caddr_t) + off, cc);
 1542                         n->m_len = cc;
 1543                         if (mlast != NULL)
 1544                                 mlast->m_next = n;
 1545                         mlast = n;      
 1546 #if 0
 1547                         newipsecstat.ips_clcopied++;
 1548 #endif
 1549 
 1550                         len -= cc;
 1551                         if (len <= 0)
 1552                                 break;
 1553                         off += cc;
 1554 
 1555                         n = m_getcl(how, m->m_type, m->m_flags);
 1556                         if (n == NULL) {
 1557                                 m_freem(mfirst);
 1558                                 m_freem(m0);
 1559                                 return (NULL);
 1560                         }
 1561                 }
 1562                 n->m_next = m->m_next; 
 1563                 if (mprev == NULL)
 1564                         m0 = mfirst;            /* new head of chain */
 1565                 else
 1566                         mprev->m_next = mfirst; /* replace old mbuf */
 1567                 m_free(m);                      /* release old mbuf */
 1568                 mprev = mfirst;
 1569         }
 1570         return (m0);
 1571 }

Cache object: 8b937b0e3b18f8370d248cb43e51eeba


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