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_mbuf2.c

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    1 /*      $KAME: uipc_mbuf2.c,v 1.31 2001/11/28 11:08:53 itojun Exp $     */
    2 /*      $NetBSD: uipc_mbuf.c,v 1.40 1999/04/01 00:23:25 thorpej Exp $   */
    3 
    4 /*-
    5  * Copyright (C) 1999 WIDE Project.
    6  * All rights reserved.
    7  * 
    8  * Redistribution and use in source and binary forms, with or without
    9  * modification, are permitted provided that the following conditions
   10  * are met:
   11  * 1. Redistributions of source code must retain the above copyright
   12  *    notice, this list of conditions and the following disclaimer.
   13  * 2. Redistributions in binary form must reproduce the above copyright
   14  *    notice, this list of conditions and the following disclaimer in the
   15  *    documentation and/or other materials provided with the distribution.
   16  * 3. Neither the name of the project nor the names of its contributors
   17  *    may be used to endorse or promote products derived from this software
   18  *    without specific prior written permission.
   19  * 
   20  * THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND
   21  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   22  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   23  * ARE DISCLAIMED.  IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE
   24  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   25  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   26  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   27  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   28  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   29  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   30  * SUCH DAMAGE.
   31  */
   32 /*-
   33  * Copyright (c) 1982, 1986, 1988, 1991, 1993
   34  *      The Regents of the University of California.  All rights reserved.
   35  *
   36  * Redistribution and use in source and binary forms, with or without
   37  * modification, are permitted provided that the following conditions
   38  * are met:
   39  * 1. Redistributions of source code must retain the above copyright
   40  *    notice, this list of conditions and the following disclaimer.
   41  * 2. Redistributions in binary form must reproduce the above copyright
   42  *    notice, this list of conditions and the following disclaimer in the
   43  *    documentation and/or other materials provided with the distribution.
   44  * 4. Neither the name of the University nor the names of its contributors
   45  *    may be used to endorse or promote products derived from this software
   46  *    without specific prior written permission.
   47  *
   48  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   49  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   50  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   51  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   52  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   53  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   54  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   55  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   56  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   57  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   58  * SUCH DAMAGE.
   59  *
   60  *      @(#)uipc_mbuf.c 8.4 (Berkeley) 2/14/95
   61  */
   62 
   63 #include <sys/cdefs.h>
   64 __FBSDID("$FreeBSD$");
   65 
   66 /*#define PULLDOWN_DEBUG*/
   67 
   68 #include "opt_mac.h"
   69 
   70 #include <sys/param.h>
   71 #include <sys/systm.h>
   72 #include <sys/kernel.h>
   73 #include <sys/lock.h>
   74 #include <sys/malloc.h>
   75 #include <sys/mbuf.h>
   76 #include <sys/mutex.h>
   77 
   78 #include <security/mac/mac_framework.h>
   79 
   80 static MALLOC_DEFINE(M_PACKET_TAGS, MBUF_TAG_MEM_NAME,
   81     "packet-attached information");
   82 
   83 /* can't call it m_dup(), as freebsd[34] uses m_dup() with different arg */
   84 static struct mbuf *m_dup1(struct mbuf *, int, int, int);
   85 
   86 /*
   87  * ensure that [off, off + len) is contiguous on the mbuf chain "m".
   88  * packet chain before "off" is kept untouched.
   89  * if offp == NULL, the target will start at <retval, 0> on resulting chain.
   90  * if offp != NULL, the target will start at <retval, *offp> on resulting chain.
   91  *
   92  * on error return (NULL return value), original "m" will be freed.
   93  *
   94  * XXX: M_TRAILINGSPACE/M_LEADINGSPACE only permitted on writable ext_buf.
   95  */
   96 struct mbuf *
   97 m_pulldown(struct mbuf *m, int off, int len, int *offp)
   98 {
   99         struct mbuf *n, *o;
  100         int hlen, tlen, olen;
  101         int writable;
  102 
  103         /* check invalid arguments. */
  104         if (m == NULL)
  105                 panic("m == NULL in m_pulldown()");
  106         if (len > MCLBYTES) {
  107                 m_freem(m);
  108                 return NULL;    /* impossible */
  109         }
  110 
  111 #ifdef PULLDOWN_DEBUG
  112     {
  113         struct mbuf *t;
  114         printf("before:");
  115         for (t = m; t; t = t->m_next)
  116                 printf(" %d", t->m_len);
  117         printf("\n");
  118     }
  119 #endif
  120         n = m;
  121         while (n != NULL && off > 0) {
  122                 if (n->m_len > off)
  123                         break;
  124                 off -= n->m_len;
  125                 n = n->m_next;
  126         }
  127         /* be sure to point non-empty mbuf */
  128         while (n != NULL && n->m_len == 0)
  129                 n = n->m_next;
  130         if (!n) {
  131                 m_freem(m);
  132                 return NULL;    /* mbuf chain too short */
  133         }
  134 
  135         /*
  136          * XXX: This code is flawed because it considers a "writable" mbuf
  137          *      data region to require all of the following:
  138          *        (i) mbuf _has_ to have M_EXT set; if it is just a regular
  139          *            mbuf, it is still not considered "writable."
  140          *        (ii) since mbuf has M_EXT, the ext_type _has_ to be
  141          *             EXT_CLUSTER. Anything else makes it non-writable.
  142          *        (iii) M_WRITABLE() must evaluate true.
  143          *      Ideally, the requirement should only be (iii).
  144          *
  145          * If we're writable, we're sure we're writable, because the ref. count
  146          * cannot increase from 1, as that would require posession of mbuf
  147          * n by someone else (which is impossible). However, if we're _not_
  148          * writable, we may eventually become writable )if the ref. count drops
  149          * to 1), but we'll fail to notice it unless we re-evaluate
  150          * M_WRITABLE(). For now, we only evaluate once at the beginning and
  151          * live with this.
  152          */
  153         /*
  154          * XXX: This is dumb. If we're just a regular mbuf with no M_EXT,
  155          *      then we're not "writable," according to this code.
  156          */
  157         writable = 0;
  158         if ((n->m_flags & M_EXT) == 0 ||
  159             (n->m_ext.ext_type == EXT_CLUSTER && M_WRITABLE(n)))
  160                 writable = 1;
  161 
  162         /*
  163          * the target data is on <n, off>.
  164          * if we got enough data on the mbuf "n", we're done.
  165          */
  166         if ((off == 0 || offp) && len <= n->m_len - off && writable)
  167                 goto ok;
  168 
  169         /*
  170          * when len <= n->m_len - off and off != 0, it is a special case.
  171          * len bytes from <n, off> sits in single mbuf, but the caller does
  172          * not like the starting position (off).
  173          * chop the current mbuf into two pieces, set off to 0.
  174          */
  175         if (len <= n->m_len - off) {
  176                 o = m_dup1(n, off, n->m_len - off, M_DONTWAIT);
  177                 if (o == NULL) {
  178                         m_freem(m);
  179                         return NULL;    /* ENOBUFS */
  180                 }
  181                 n->m_len = off;
  182                 o->m_next = n->m_next;
  183                 n->m_next = o;
  184                 n = n->m_next;
  185                 off = 0;
  186                 goto ok;
  187         }
  188 
  189         /*
  190          * we need to take hlen from <n, off> and tlen from <n->m_next, 0>,
  191          * and construct contiguous mbuf with m_len == len.
  192          * note that hlen + tlen == len, and tlen > 0.
  193          */
  194         hlen = n->m_len - off;
  195         tlen = len - hlen;
  196 
  197         /*
  198          * ensure that we have enough trailing data on mbuf chain.
  199          * if not, we can do nothing about the chain.
  200          */
  201         olen = 0;
  202         for (o = n->m_next; o != NULL; o = o->m_next)
  203                 olen += o->m_len;
  204         if (hlen + olen < len) {
  205                 m_freem(m);
  206                 return NULL;    /* mbuf chain too short */
  207         }
  208 
  209         /*
  210          * easy cases first.
  211          * we need to use m_copydata() to get data from <n->m_next, 0>.
  212          */
  213         if ((off == 0 || offp) && M_TRAILINGSPACE(n) >= tlen
  214          && writable) {
  215                 m_copydata(n->m_next, 0, tlen, mtod(n, caddr_t) + n->m_len);
  216                 n->m_len += tlen;
  217                 m_adj(n->m_next, tlen);
  218                 goto ok;
  219         }
  220         if ((off == 0 || offp) && M_LEADINGSPACE(n->m_next) >= hlen
  221          && writable) {
  222                 n->m_next->m_data -= hlen;
  223                 n->m_next->m_len += hlen;
  224                 bcopy(mtod(n, caddr_t) + off, mtod(n->m_next, caddr_t), hlen);
  225                 n->m_len -= hlen;
  226                 n = n->m_next;
  227                 off = 0;
  228                 goto ok;
  229         }
  230 
  231         /*
  232          * now, we need to do the hard way.  don't m_copy as there's no room
  233          * on both end.
  234          */
  235         if (len > MLEN)
  236                 o = m_getcl(M_DONTWAIT, m->m_type, 0);
  237         else
  238                 o = m_get(M_DONTWAIT, m->m_type);
  239         if (!o) {
  240                 m_freem(m);
  241                 return NULL;    /* ENOBUFS */
  242         }
  243         /* get hlen from <n, off> into <o, 0> */
  244         o->m_len = hlen;
  245         bcopy(mtod(n, caddr_t) + off, mtod(o, caddr_t), hlen);
  246         n->m_len -= hlen;
  247         /* get tlen from <n->m_next, 0> into <o, hlen> */
  248         m_copydata(n->m_next, 0, tlen, mtod(o, caddr_t) + o->m_len);
  249         o->m_len += tlen;
  250         m_adj(n->m_next, tlen);
  251         o->m_next = n->m_next;
  252         n->m_next = o;
  253         n = o;
  254         off = 0;
  255 
  256 ok:
  257 #ifdef PULLDOWN_DEBUG
  258     {
  259         struct mbuf *t;
  260         printf("after:");
  261         for (t = m; t; t = t->m_next)
  262                 printf("%c%d", t == n ? '*' : ' ', t->m_len);
  263         printf(" (off=%d)\n", off);
  264     }
  265 #endif
  266         if (offp)
  267                 *offp = off;
  268         return n;
  269 }
  270 
  271 static struct mbuf *
  272 m_dup1(struct mbuf *m, int off, int len, int wait)
  273 {
  274         struct mbuf *n;
  275         int copyhdr;
  276 
  277         if (len > MCLBYTES)
  278                 return NULL;
  279         if (off == 0 && (m->m_flags & M_PKTHDR) != 0)
  280                 copyhdr = 1;
  281         else
  282                 copyhdr = 0;
  283         if (len >= MINCLSIZE) {
  284                 if (copyhdr == 1)
  285                         n = m_getcl(wait, m->m_type, M_PKTHDR);
  286                 else
  287                         n = m_getcl(wait, m->m_type, 0);
  288         } else {
  289                 if (copyhdr == 1)
  290                         n = m_gethdr(wait, m->m_type);
  291                 else
  292                         n = m_get(wait, m->m_type);
  293         }
  294         if (!n)
  295                 return NULL; /* ENOBUFS */
  296 
  297         if (copyhdr && !m_dup_pkthdr(n, m, wait)) {
  298                 m_free(n);
  299                 return NULL;
  300         }
  301         m_copydata(m, off, len, mtod(n, caddr_t));
  302         n->m_len = len;
  303         return n;
  304 }
  305 
  306 /* Free a packet tag. */
  307 void
  308 m_tag_free_default(struct m_tag *t)
  309 {
  310 #ifdef MAC
  311         if (t->m_tag_id == PACKET_TAG_MACLABEL)
  312                 mac_destroy_mbuf_tag(t);
  313 #endif
  314         free(t, M_PACKET_TAGS);
  315 }
  316 
  317 /* Get a packet tag structure along with specified data following. */
  318 struct m_tag *
  319 m_tag_alloc(u_int32_t cookie, int type, int len, int wait)
  320 {
  321         struct m_tag *t;
  322 
  323         MBUF_CHECKSLEEP(wait);
  324         if (len < 0)
  325                 return NULL;
  326         t = malloc(len + sizeof(struct m_tag), M_PACKET_TAGS, wait);
  327         if (t == NULL)
  328                 return NULL;
  329         m_tag_setup(t, cookie, type, len);
  330         t->m_tag_free = m_tag_free_default;
  331         return t;
  332 }
  333 
  334 /* Unlink and free a packet tag. */
  335 void
  336 m_tag_delete(struct mbuf *m, struct m_tag *t)
  337 {
  338 
  339         KASSERT(m && t, ("m_tag_delete: null argument, m %p t %p", m, t));
  340         m_tag_unlink(m, t);
  341         m_tag_free(t);
  342 }
  343 
  344 /* Unlink and free a packet tag chain, starting from given tag. */
  345 void
  346 m_tag_delete_chain(struct mbuf *m, struct m_tag *t)
  347 {
  348         struct m_tag *p, *q;
  349 
  350         KASSERT(m, ("m_tag_delete_chain: null mbuf"));
  351         if (t != NULL)
  352                 p = t;
  353         else
  354                 p = SLIST_FIRST(&m->m_pkthdr.tags);
  355         if (p == NULL)
  356                 return;
  357         while ((q = SLIST_NEXT(p, m_tag_link)) != NULL)
  358                 m_tag_delete(m, q);
  359         m_tag_delete(m, p);
  360 }
  361 
  362 /*
  363  * Strip off all tags that would normally vanish when
  364  * passing through a network interface.  Only persistent
  365  * tags will exist after this; these are expected to remain
  366  * so long as the mbuf chain exists, regardless of the
  367  * path the mbufs take.
  368  */
  369 void
  370 m_tag_delete_nonpersistent(struct mbuf *m)
  371 {
  372         struct m_tag *p, *q;
  373 
  374         SLIST_FOREACH_SAFE(p, &m->m_pkthdr.tags, m_tag_link, q)
  375                 if ((p->m_tag_id & MTAG_PERSISTENT) == 0)
  376                         m_tag_delete(m, p);
  377 }
  378 
  379 /* Find a tag, starting from a given position. */
  380 struct m_tag *
  381 m_tag_locate(struct mbuf *m, u_int32_t cookie, int type, struct m_tag *t)
  382 {
  383         struct m_tag *p;
  384 
  385         KASSERT(m, ("m_tag_locate: null mbuf"));
  386         if (t == NULL)
  387                 p = SLIST_FIRST(&m->m_pkthdr.tags);
  388         else
  389                 p = SLIST_NEXT(t, m_tag_link);
  390         while (p != NULL) {
  391                 if (p->m_tag_cookie == cookie && p->m_tag_id == type)
  392                         return p;
  393                 p = SLIST_NEXT(p, m_tag_link);
  394         }
  395         return NULL;
  396 }
  397 
  398 /* Copy a single tag. */
  399 struct m_tag *
  400 m_tag_copy(struct m_tag *t, int how)
  401 {
  402         struct m_tag *p;
  403 
  404         MBUF_CHECKSLEEP(how);
  405         KASSERT(t, ("m_tag_copy: null tag"));
  406         p = m_tag_alloc(t->m_tag_cookie, t->m_tag_id, t->m_tag_len, how);
  407         if (p == NULL)
  408                 return (NULL);
  409 #ifdef MAC
  410         /*
  411          * XXXMAC: we should probably pass off the initialization, and
  412          * copying here?  can we hide that PACKET_TAG_MACLABEL is
  413          * special from the mbuf code?
  414          */
  415         if (t->m_tag_id == PACKET_TAG_MACLABEL) {
  416                 if (mac_init_mbuf_tag(p, how) != 0) {
  417                         m_tag_free(p);
  418                         return (NULL);
  419                 }
  420                 mac_copy_mbuf_tag(t, p);
  421         } else
  422 #endif
  423                 bcopy(t + 1, p + 1, t->m_tag_len); /* Copy the data */
  424         return p;
  425 }
  426 
  427 /*
  428  * Copy two tag chains. The destination mbuf (to) loses any attached
  429  * tags even if the operation fails. This should not be a problem, as
  430  * m_tag_copy_chain() is typically called with a newly-allocated
  431  * destination mbuf.
  432  */
  433 int
  434 m_tag_copy_chain(struct mbuf *to, struct mbuf *from, int how)
  435 {
  436         struct m_tag *p, *t, *tprev = NULL;
  437 
  438         MBUF_CHECKSLEEP(how);
  439         KASSERT(to && from,
  440                 ("m_tag_copy_chain: null argument, to %p from %p", to, from));
  441         m_tag_delete_chain(to, NULL);
  442         SLIST_FOREACH(p, &from->m_pkthdr.tags, m_tag_link) {
  443                 t = m_tag_copy(p, how);
  444                 if (t == NULL) {
  445                         m_tag_delete_chain(to, NULL);
  446                         return 0;
  447                 }
  448                 if (tprev == NULL)
  449                         SLIST_INSERT_HEAD(&to->m_pkthdr.tags, t, m_tag_link);
  450                 else
  451                         SLIST_INSERT_AFTER(tprev, t, m_tag_link);
  452                 tprev = t;
  453         }
  454         return 1;
  455 }

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