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 <sys/param.h>
   69 #include <sys/systm.h>
   70 #include <sys/kernel.h>
   71 #include <sys/lock.h>
   72 #include <sys/malloc.h>
   73 #include <sys/mbuf.h>
   74 #include <sys/mutex.h>
   75 
   76 #include <security/mac/mac_framework.h>
   77 
   78 static MALLOC_DEFINE(M_PACKET_TAGS, MBUF_TAG_MEM_NAME,
   79     "packet-attached information");
   80 
   81 /* can't call it m_dup(), as freebsd[34] uses m_dup() with different arg */
   82 static struct mbuf *m_dup1(struct mbuf *, int, int, int);
   83 
   84 /*
   85  * ensure that [off, off + len) is contiguous on the mbuf chain "m".
   86  * packet chain before "off" is kept untouched.
   87  * if offp == NULL, the target will start at <retval, 0> on resulting chain.
   88  * if offp != NULL, the target will start at <retval, *offp> on resulting chain.
   89  *
   90  * on error return (NULL return value), original "m" will be freed.
   91  *
   92  * XXX: M_TRAILINGSPACE/M_LEADINGSPACE only permitted on writable ext_buf.
   93  */
   94 struct mbuf *
   95 m_pulldown(struct mbuf *m, int off, int len, int *offp)
   96 {
   97         struct mbuf *n, *o;
   98         int hlen, tlen, olen;
   99         int writable;
  100 
  101         /* check invalid arguments. */
  102         KASSERT(m != NULL, ("%s: fix caller: m is NULL off %d len %d offp %p\n",
  103             __func__, off, len, offp));
  104         if (len > MCLBYTES) {
  105                 m_freem(m);
  106                 return NULL;    /* impossible */
  107         }
  108 
  109 #ifdef PULLDOWN_DEBUG
  110     {
  111         struct mbuf *t;
  112         printf("before:");
  113         for (t = m; t; t = t->m_next)
  114                 printf(" %d", t->m_len);
  115         printf("\n");
  116     }
  117 #endif
  118         n = m;
  119         while (n != NULL && off > 0) {
  120                 if (n->m_len > off)
  121                         break;
  122                 off -= n->m_len;
  123                 n = n->m_next;
  124         }
  125         /* be sure to point non-empty mbuf */
  126         while (n != NULL && n->m_len == 0)
  127                 n = n->m_next;
  128         if (!n) {
  129                 m_freem(m);
  130                 return NULL;    /* mbuf chain too short */
  131         }
  132 
  133         /*
  134          * The following comment is dated but still partially applies:
  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 possession 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         writable = 0;
  154         if ((n->m_flags & M_EXT) == 0 ||
  155             (n->m_ext.ext_type == EXT_CLUSTER && M_WRITABLE(n)))
  156                 writable = 1;
  157 
  158         /*
  159          * the target data is on <n, off>.
  160          * if we got enough data on the mbuf "n", we're done.
  161          */
  162         if ((off == 0 || offp) && len <= n->m_len - off)
  163                 goto ok;
  164 
  165         /*
  166          * when len <= n->m_len - off and off != 0, it is a special case.
  167          * len bytes from <n, off> sits in single mbuf, but the caller does
  168          * not like the starting position (off).
  169          * chop the current mbuf into two pieces, set off to 0.
  170          */
  171         if (len <= n->m_len - off) {
  172                 o = m_dup1(n, off, n->m_len - off, M_NOWAIT);
  173                 if (o == NULL) {
  174                         m_freem(m);
  175                         return NULL;    /* ENOBUFS */
  176                 }
  177                 n->m_len = off;
  178                 o->m_next = n->m_next;
  179                 n->m_next = o;
  180                 n = n->m_next;
  181                 off = 0;
  182                 goto ok;
  183         }
  184 
  185         /*
  186          * we need to take hlen from <n, off> and tlen from <n->m_next, 0>,
  187          * and construct contiguous mbuf with m_len == len.
  188          * note that hlen + tlen == len, and tlen > 0.
  189          */
  190         hlen = n->m_len - off;
  191         tlen = len - hlen;
  192 
  193         /*
  194          * ensure that we have enough trailing data on mbuf chain.
  195          * if not, we can do nothing about the chain.
  196          */
  197         olen = 0;
  198         for (o = n->m_next; o != NULL; o = o->m_next)
  199                 olen += o->m_len;
  200         if (hlen + olen < len) {
  201                 m_freem(m);
  202                 return NULL;    /* mbuf chain too short */
  203         }
  204 
  205         /*
  206          * easy cases first.
  207          * we need to use m_copydata() to get data from <n->m_next, 0>.
  208          */
  209         if ((off == 0 || offp) && M_TRAILINGSPACE(n) >= tlen
  210          && writable) {
  211                 m_copydata(n->m_next, 0, tlen, mtod(n, caddr_t) + n->m_len);
  212                 n->m_len += tlen;
  213                 m_adj(n->m_next, tlen);
  214                 goto ok;
  215         }
  216         if ((off == 0 || offp) && M_LEADINGSPACE(n->m_next) >= hlen
  217          && writable && n->m_next->m_len >= tlen) {
  218                 n->m_next->m_data -= hlen;
  219                 n->m_next->m_len += hlen;
  220                 bcopy(mtod(n, caddr_t) + off, mtod(n->m_next, caddr_t), hlen);
  221                 n->m_len -= hlen;
  222                 n = n->m_next;
  223                 off = 0;
  224                 goto ok;
  225         }
  226 
  227         /*
  228          * now, we need to do the hard way.  don't m_copy as there's no room
  229          * on both end.
  230          */
  231         if (len > MLEN)
  232                 o = m_getcl(M_NOWAIT, m->m_type, 0);
  233         else
  234                 o = m_get(M_NOWAIT, m->m_type);
  235         if (!o) {
  236                 m_freem(m);
  237                 return NULL;    /* ENOBUFS */
  238         }
  239         /* get hlen from <n, off> into <o, 0> */
  240         o->m_len = hlen;
  241         bcopy(mtod(n, caddr_t) + off, mtod(o, caddr_t), hlen);
  242         n->m_len -= hlen;
  243         /* get tlen from <n->m_next, 0> into <o, hlen> */
  244         m_copydata(n->m_next, 0, tlen, mtod(o, caddr_t) + o->m_len);
  245         o->m_len += tlen;
  246         m_adj(n->m_next, tlen);
  247         o->m_next = n->m_next;
  248         n->m_next = o;
  249         n = o;
  250         off = 0;
  251 
  252 ok:
  253 #ifdef PULLDOWN_DEBUG
  254     {
  255         struct mbuf *t;
  256         printf("after:");
  257         for (t = m; t; t = t->m_next)
  258                 printf("%c%d", t == n ? '*' : ' ', t->m_len);
  259         printf(" (off=%d)\n", off);
  260     }
  261 #endif
  262         if (offp)
  263                 *offp = off;
  264         return n;
  265 }
  266 
  267 static struct mbuf *
  268 m_dup1(struct mbuf *m, int off, int len, int wait)
  269 {
  270         struct mbuf *n;
  271         int copyhdr;
  272 
  273         if (len > MCLBYTES)
  274                 return NULL;
  275         if (off == 0 && (m->m_flags & M_PKTHDR) != 0)
  276                 copyhdr = 1;
  277         else
  278                 copyhdr = 0;
  279         if (len >= MINCLSIZE) {
  280                 if (copyhdr == 1)
  281                         n = m_getcl(wait, m->m_type, M_PKTHDR);
  282                 else
  283                         n = m_getcl(wait, m->m_type, 0);
  284         } else {
  285                 if (copyhdr == 1)
  286                         n = m_gethdr(wait, m->m_type);
  287                 else
  288                         n = m_get(wait, m->m_type);
  289         }
  290         if (!n)
  291                 return NULL; /* ENOBUFS */
  292 
  293         if (copyhdr && !m_dup_pkthdr(n, m, wait)) {
  294                 m_free(n);
  295                 return NULL;
  296         }
  297         m_copydata(m, off, len, mtod(n, caddr_t));
  298         n->m_len = len;
  299         return n;
  300 }
  301 
  302 /* Free a packet tag. */
  303 void
  304 m_tag_free_default(struct m_tag *t)
  305 {
  306 #ifdef MAC
  307         if (t->m_tag_id == PACKET_TAG_MACLABEL)
  308                 mac_mbuf_tag_destroy(t);
  309 #endif
  310         free(t, M_PACKET_TAGS);
  311 }
  312 
  313 /* Get a packet tag structure along with specified data following. */
  314 struct m_tag *
  315 m_tag_alloc(uint32_t cookie, int type, int len, int wait)
  316 {
  317         struct m_tag *t;
  318 
  319         MBUF_CHECKSLEEP(wait);
  320         if (len < 0)
  321                 return NULL;
  322         t = malloc(len + sizeof(struct m_tag), M_PACKET_TAGS, wait);
  323         if (t == NULL)
  324                 return NULL;
  325         m_tag_setup(t, cookie, type, len);
  326         t->m_tag_free = m_tag_free_default;
  327         return t;
  328 }
  329 
  330 /* Unlink and free a packet tag. */
  331 void
  332 m_tag_delete(struct mbuf *m, struct m_tag *t)
  333 {
  334 
  335         KASSERT(m && t, ("m_tag_delete: null argument, m %p t %p", m, t));
  336         m_tag_unlink(m, t);
  337         m_tag_free(t);
  338 }
  339 
  340 /* Unlink and free a packet tag chain, starting from given tag. */
  341 void
  342 m_tag_delete_chain(struct mbuf *m, struct m_tag *t)
  343 {
  344         struct m_tag *p, *q;
  345 
  346         KASSERT(m, ("m_tag_delete_chain: null mbuf"));
  347         if (t != NULL)
  348                 p = t;
  349         else
  350                 p = SLIST_FIRST(&m->m_pkthdr.tags);
  351         if (p == NULL)
  352                 return;
  353         while ((q = SLIST_NEXT(p, m_tag_link)) != NULL)
  354                 m_tag_delete(m, q);
  355         m_tag_delete(m, p);
  356 }
  357 
  358 /*
  359  * Strip off all tags that would normally vanish when
  360  * passing through a network interface.  Only persistent
  361  * tags will exist after this; these are expected to remain
  362  * so long as the mbuf chain exists, regardless of the
  363  * path the mbufs take.
  364  */
  365 void
  366 m_tag_delete_nonpersistent(struct mbuf *m)
  367 {
  368         struct m_tag *p, *q;
  369 
  370         SLIST_FOREACH_SAFE(p, &m->m_pkthdr.tags, m_tag_link, q)
  371                 if ((p->m_tag_id & MTAG_PERSISTENT) == 0)
  372                         m_tag_delete(m, p);
  373 }
  374 
  375 /* Find a tag, starting from a given position. */
  376 struct m_tag *
  377 m_tag_locate(struct mbuf *m, uint32_t cookie, int type, struct m_tag *t)
  378 {
  379         struct m_tag *p;
  380 
  381         KASSERT(m, ("m_tag_locate: null mbuf"));
  382         if (t == NULL)
  383                 p = SLIST_FIRST(&m->m_pkthdr.tags);
  384         else
  385                 p = SLIST_NEXT(t, m_tag_link);
  386         while (p != NULL) {
  387                 if (p->m_tag_cookie == cookie && p->m_tag_id == type)
  388                         return p;
  389                 p = SLIST_NEXT(p, m_tag_link);
  390         }
  391         return NULL;
  392 }
  393 
  394 /* Copy a single tag. */
  395 struct m_tag *
  396 m_tag_copy(struct m_tag *t, int how)
  397 {
  398         struct m_tag *p;
  399 
  400         MBUF_CHECKSLEEP(how);
  401         KASSERT(t, ("m_tag_copy: null tag"));
  402         p = m_tag_alloc(t->m_tag_cookie, t->m_tag_id, t->m_tag_len, how);
  403         if (p == NULL)
  404                 return (NULL);
  405 #ifdef MAC
  406         /*
  407          * XXXMAC: we should probably pass off the initialization, and
  408          * copying here?  can we hide that PACKET_TAG_MACLABEL is
  409          * special from the mbuf code?
  410          */
  411         if (t->m_tag_id == PACKET_TAG_MACLABEL) {
  412                 if (mac_mbuf_tag_init(p, how) != 0) {
  413                         m_tag_free(p);
  414                         return (NULL);
  415                 }
  416                 mac_mbuf_tag_copy(t, p);
  417         } else
  418 #endif
  419                 bcopy(t + 1, p + 1, t->m_tag_len); /* Copy the data */
  420         return p;
  421 }
  422 
  423 /*
  424  * Copy two tag chains. The destination mbuf (to) loses any attached
  425  * tags even if the operation fails. This should not be a problem, as
  426  * m_tag_copy_chain() is typically called with a newly-allocated
  427  * destination mbuf.
  428  */
  429 int
  430 m_tag_copy_chain(struct mbuf *to, const struct mbuf *from, int how)
  431 {
  432         struct m_tag *p, *t, *tprev = NULL;
  433 
  434         MBUF_CHECKSLEEP(how);
  435         KASSERT(to && from,
  436                 ("m_tag_copy_chain: null argument, to %p from %p", to, from));
  437         m_tag_delete_chain(to, NULL);
  438         SLIST_FOREACH(p, &from->m_pkthdr.tags, m_tag_link) {
  439                 t = m_tag_copy(p, how);
  440                 if (t == NULL) {
  441                         m_tag_delete_chain(to, NULL);
  442                         return 0;
  443                 }
  444                 if (tprev == NULL)
  445                         SLIST_INSERT_HEAD(&to->m_pkthdr.tags, t, m_tag_link);
  446                 else
  447                         SLIST_INSERT_AFTER(tprev, t, m_tag_link);
  448                 tprev = t;
  449         }
  450         return 1;
  451 }

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