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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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/mac.h>
   75 #include <sys/malloc.h>
   76 #include <sys/mbuf.h>
   77 #include <sys/mutex.h>
   78 
   79 static MALLOC_DEFINE(M_PACKET_TAGS, MBUF_TAG_MEM_NAME,
   80     "packet-attached information");
   81 
   82 /* can't call it m_dup(), as freebsd[34] uses m_dup() with different arg */
   83 static struct mbuf *m_dup1(struct mbuf *, int, int, int);
   84 
   85 /*
   86  * ensure that [off, off + len) is contiguous on the mbuf chain "m".
   87  * packet chain before "off" is kept untouched.
   88  * if offp == NULL, the target will start at <retval, 0> on resulting chain.
   89  * if offp != NULL, the target will start at <retval, *offp> on resulting chain.
   90  *
   91  * on error return (NULL return value), original "m" will be freed.
   92  *
   93  * XXX: M_TRAILINGSPACE/M_LEADINGSPACE only permitted on writable ext_buf.
   94  */
   95 struct mbuf *
   96 m_pulldown(struct mbuf *m, int off, int len, int *offp)
   97 {
   98         struct mbuf *n, *o;
   99         int hlen, tlen, olen;
  100         int writable;
  101 
  102         /* check invalid arguments. */
  103         if (m == NULL)
  104                 panic("m == NULL in m_pulldown()");
  105         if (len > MCLBYTES) {
  106                 m_freem(m);
  107                 return NULL;    /* impossible */
  108         }
  109 
  110 #ifdef PULLDOWN_DEBUG
  111     {
  112         struct mbuf *t;
  113         printf("before:");
  114         for (t = m; t; t = t->m_next)
  115                 printf(" %d", t->m_len);
  116         printf("\n");
  117     }
  118 #endif
  119         n = m;
  120         while (n != NULL && off > 0) {
  121                 if (n->m_len > off)
  122                         break;
  123                 off -= n->m_len;
  124                 n = n->m_next;
  125         }
  126         /* be sure to point non-empty mbuf */
  127         while (n != NULL && n->m_len == 0)
  128                 n = n->m_next;
  129         if (!n) {
  130                 m_freem(m);
  131                 return NULL;    /* mbuf chain too short */
  132         }
  133 
  134         /*
  135          * XXX: This code is flawed because it considers a "writable" mbuf
  136          *      data region to require all of the following:
  137          *        (i) mbuf _has_ to have M_EXT set; if it is just a regular
  138          *            mbuf, it is still not considered "writable."
  139          *        (ii) since mbuf has M_EXT, the ext_type _has_ to be
  140          *             EXT_CLUSTER. Anything else makes it non-writable.
  141          *        (iii) M_WRITABLE() must evaluate true.
  142          *      Ideally, the requirement should only be (iii).
  143          *
  144          * If we're writable, we're sure we're writable, because the ref. count
  145          * cannot increase from 1, as that would require posession of mbuf
  146          * n by someone else (which is impossible). However, if we're _not_
  147          * writable, we may eventually become writable )if the ref. count drops
  148          * to 1), but we'll fail to notice it unless we re-evaluate
  149          * M_WRITABLE(). For now, we only evaluate once at the beginning and
  150          * live with this.
  151          */
  152         /*
  153          * XXX: This is dumb. If we're just a regular mbuf with no M_EXT,
  154          *      then we're not "writable," according to this code.
  155          */
  156         writable = 0;
  157         if ((n->m_flags & M_EXT) == 0 ||
  158             (n->m_ext.ext_type == EXT_CLUSTER && M_WRITABLE(n)))
  159                 writable = 1;
  160 
  161         /*
  162          * the target data is on <n, off>.
  163          * if we got enough data on the mbuf "n", we're done.
  164          */
  165         if ((off == 0 || offp) && len <= n->m_len - off && writable)
  166                 goto ok;
  167 
  168         /*
  169          * when len <= n->m_len - off and off != 0, it is a special case.
  170          * len bytes from <n, off> sits in single mbuf, but the caller does
  171          * not like the starting position (off).
  172          * chop the current mbuf into two pieces, set off to 0.
  173          */
  174         if (len <= n->m_len - off) {
  175                 o = m_dup1(n, off, n->m_len - off, M_DONTWAIT);
  176                 if (o == NULL) {
  177                         m_freem(m);
  178                         return NULL;    /* ENOBUFS */
  179                 }
  180                 n->m_len = off;
  181                 o->m_next = n->m_next;
  182                 n->m_next = o;
  183                 n = n->m_next;
  184                 off = 0;
  185                 goto ok;
  186         }
  187 
  188         /*
  189          * we need to take hlen from <n, off> and tlen from <n->m_next, 0>,
  190          * and construct contiguous mbuf with m_len == len.
  191          * note that hlen + tlen == len, and tlen > 0.
  192          */
  193         hlen = n->m_len - off;
  194         tlen = len - hlen;
  195 
  196         /*
  197          * ensure that we have enough trailing data on mbuf chain.
  198          * if not, we can do nothing about the chain.
  199          */
  200         olen = 0;
  201         for (o = n->m_next; o != NULL; o = o->m_next)
  202                 olen += o->m_len;
  203         if (hlen + olen < len) {
  204                 m_freem(m);
  205                 return NULL;    /* mbuf chain too short */
  206         }
  207 
  208         /*
  209          * easy cases first.
  210          * we need to use m_copydata() to get data from <n->m_next, 0>.
  211          */
  212         if ((off == 0 || offp) && M_TRAILINGSPACE(n) >= tlen
  213          && writable) {
  214                 m_copydata(n->m_next, 0, tlen, mtod(n, caddr_t) + n->m_len);
  215                 n->m_len += tlen;
  216                 m_adj(n->m_next, tlen);
  217                 goto ok;
  218         }
  219         if ((off == 0 || offp) && M_LEADINGSPACE(n->m_next) >= hlen
  220          && writable) {
  221                 n->m_next->m_data -= hlen;
  222                 n->m_next->m_len += hlen;
  223                 bcopy(mtod(n, caddr_t) + off, mtod(n->m_next, caddr_t), hlen);
  224                 n->m_len -= hlen;
  225                 n = n->m_next;
  226                 off = 0;
  227                 goto ok;
  228         }
  229 
  230         /*
  231          * now, we need to do the hard way.  don't m_copy as there's no room
  232          * on both end.
  233          */
  234         if (len > MLEN)
  235                 o = m_getcl(M_DONTWAIT, m->m_type, 0);
  236         else
  237                 o = m_get(M_DONTWAIT, m->m_type);
  238         if (!o) {
  239                 m_freem(m);
  240                 return NULL;    /* ENOBUFS */
  241         }
  242         /* get hlen from <n, off> into <o, 0> */
  243         o->m_len = hlen;
  244         bcopy(mtod(n, caddr_t) + off, mtod(o, caddr_t), hlen);
  245         n->m_len -= hlen;
  246         /* get tlen from <n->m_next, 0> into <o, hlen> */
  247         m_copydata(n->m_next, 0, tlen, mtod(o, caddr_t) + o->m_len);
  248         o->m_len += tlen;
  249         m_adj(n->m_next, tlen);
  250         o->m_next = n->m_next;
  251         n->m_next = o;
  252         n = o;
  253         off = 0;
  254 
  255 ok:
  256 #ifdef PULLDOWN_DEBUG
  257     {
  258         struct mbuf *t;
  259         printf("after:");
  260         for (t = m; t; t = t->m_next)
  261                 printf("%c%d", t == n ? '*' : ' ', t->m_len);
  262         printf(" (off=%d)\n", off);
  263     }
  264 #endif
  265         if (offp)
  266                 *offp = off;
  267         return n;
  268 }
  269 
  270 static struct mbuf *
  271 m_dup1(struct mbuf *m, int off, int len, int wait)
  272 {
  273         struct mbuf *n;
  274         int copyhdr;
  275 
  276         if (len > MCLBYTES)
  277                 return NULL;
  278         if (off == 0 && (m->m_flags & M_PKTHDR) != 0)
  279                 copyhdr = 1;
  280         else
  281                 copyhdr = 0;
  282         if (len >= MINCLSIZE) {
  283                 if (copyhdr == 1)
  284                         n = m_getcl(wait, m->m_type, M_PKTHDR);
  285                 else
  286                         n = m_getcl(wait, m->m_type, 0);
  287         } else {
  288                 if (copyhdr == 1)
  289                         n = m_gethdr(wait, m->m_type);
  290                 else
  291                         n = m_get(wait, m->m_type);
  292         }
  293         if (!n)
  294                 return NULL; /* ENOBUFS */
  295 
  296         if (copyhdr && !m_dup_pkthdr(n, m, wait)) {
  297                 m_free(n);
  298                 return NULL;
  299         }
  300         m_copydata(m, off, len, mtod(n, caddr_t));
  301         n->m_len = len;
  302         return n;
  303 }
  304 
  305 /* Free a packet tag. */
  306 void
  307 m_tag_free_default(struct m_tag *t)
  308 {
  309 #ifdef MAC
  310         if (t->m_tag_id == PACKET_TAG_MACLABEL)
  311                 mac_destroy_mbuf_tag(t);
  312 #endif
  313         free(t, M_PACKET_TAGS);
  314 }
  315 
  316 /* Get a packet tag structure along with specified data following. */
  317 struct m_tag *
  318 m_tag_alloc(u_int32_t cookie, int type, int len, int wait)
  319 {
  320         struct m_tag *t;
  321 
  322         MBUF_CHECKSLEEP(wait);
  323         if (len < 0)
  324                 return NULL;
  325         t = malloc(len + sizeof(struct m_tag), M_PACKET_TAGS, wait);
  326         if (t == NULL)
  327                 return NULL;
  328         m_tag_setup(t, cookie, type, len);
  329         t->m_tag_free = m_tag_free_default;
  330         return t;
  331 }
  332 
  333 /* Unlink and free a packet tag. */
  334 void
  335 m_tag_delete(struct mbuf *m, struct m_tag *t)
  336 {
  337 
  338         KASSERT(m && t, ("m_tag_delete: null argument, m %p t %p", m, t));
  339         m_tag_unlink(m, t);
  340         m_tag_free(t);
  341 }
  342 
  343 /* Unlink and free a packet tag chain, starting from given tag. */
  344 void
  345 m_tag_delete_chain(struct mbuf *m, struct m_tag *t)
  346 {
  347         struct m_tag *p, *q;
  348 
  349         KASSERT(m, ("m_tag_delete_chain: null mbuf"));
  350         if (t != NULL)
  351                 p = t;
  352         else
  353                 p = SLIST_FIRST(&m->m_pkthdr.tags);
  354         if (p == NULL)
  355                 return;
  356         while ((q = SLIST_NEXT(p, m_tag_link)) != NULL)
  357                 m_tag_delete(m, q);
  358         m_tag_delete(m, p);
  359 }
  360 
  361 /*
  362  * Strip off all tags that would normally vanish when
  363  * passing through a network interface.  Only persistent
  364  * tags will exist after this; these are expected to remain
  365  * so long as the mbuf chain exists, regardless of the
  366  * path the mbufs take.
  367  */
  368 void
  369 m_tag_delete_nonpersistent(struct mbuf *m)
  370 {
  371         struct m_tag *p, *q;
  372 
  373         SLIST_FOREACH_SAFE(p, &m->m_pkthdr.tags, m_tag_link, q)
  374                 if ((p->m_tag_id & MTAG_PERSISTENT) == 0)
  375                         m_tag_delete(m, p);
  376 }
  377 
  378 /* Find a tag, starting from a given position. */
  379 struct m_tag *
  380 m_tag_locate(struct mbuf *m, u_int32_t cookie, int type, struct m_tag *t)
  381 {
  382         struct m_tag *p;
  383 
  384         KASSERT(m, ("m_tag_locate: null mbuf"));
  385         if (t == NULL)
  386                 p = SLIST_FIRST(&m->m_pkthdr.tags);
  387         else
  388                 p = SLIST_NEXT(t, m_tag_link);
  389         while (p != NULL) {
  390                 if (p->m_tag_cookie == cookie && p->m_tag_id == type)
  391                         return p;
  392                 p = SLIST_NEXT(p, m_tag_link);
  393         }
  394         return NULL;
  395 }
  396 
  397 /* Copy a single tag. */
  398 struct m_tag *
  399 m_tag_copy(struct m_tag *t, int how)
  400 {
  401         struct m_tag *p;
  402 
  403         MBUF_CHECKSLEEP(how);
  404         KASSERT(t, ("m_tag_copy: null tag"));
  405         p = m_tag_alloc(t->m_tag_cookie, t->m_tag_id, t->m_tag_len, how);
  406         if (p == NULL)
  407                 return (NULL);
  408 #ifdef MAC
  409         /*
  410          * XXXMAC: we should probably pass off the initialization, and
  411          * copying here?  can we hide that PACKET_TAG_MACLABEL is
  412          * special from the mbuf code?
  413          */
  414         if (t->m_tag_id == PACKET_TAG_MACLABEL) {
  415                 if (mac_init_mbuf_tag(p, how) != 0) {
  416                         m_tag_free(p);
  417                         return (NULL);
  418                 }
  419                 mac_copy_mbuf_tag(t, p);
  420         } else
  421 #endif
  422                 bcopy(t + 1, p + 1, t->m_tag_len); /* Copy the data */
  423         return p;
  424 }
  425 
  426 /*
  427  * Copy two tag chains. The destination mbuf (to) loses any attached
  428  * tags even if the operation fails. This should not be a problem, as
  429  * m_tag_copy_chain() is typically called with a newly-allocated
  430  * destination mbuf.
  431  */
  432 int
  433 m_tag_copy_chain(struct mbuf *to, struct mbuf *from, int how)
  434 {
  435         struct m_tag *p, *t, *tprev = NULL;
  436 
  437         MBUF_CHECKSLEEP(how);
  438         KASSERT(to && from,
  439                 ("m_tag_copy_chain: null argument, to %p from %p", to, from));
  440         m_tag_delete_chain(to, NULL);
  441         SLIST_FOREACH(p, &from->m_pkthdr.tags, m_tag_link) {
  442                 t = m_tag_copy(p, how);
  443                 if (t == NULL) {
  444                         m_tag_delete_chain(to, NULL);
  445                         return 0;
  446                 }
  447                 if (tprev == NULL)
  448                         SLIST_INSERT_HEAD(&to->m_pkthdr.tags, t, m_tag_link);
  449                 else
  450                         SLIST_INSERT_AFTER(tprev, t, m_tag_link);
  451                 tprev = t;
  452         }
  453         return 1;
  454 }

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