uipc_mbuf2.c

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    1 /*      $FreeBSD: releng/5.0/sys/kern/uipc_mbuf2.c 107283 2002-11-26 17:59:16Z sam $    */
    2 /*      $KAME: uipc_mbuf2.c,v 1.31 2001/11/28 11:08:53 itojun Exp $     */
    3 /*      $NetBSD: uipc_mbuf.c,v 1.40 1999/04/01 00:23:25 thorpej Exp $   */
    4 
    5 /*
    6  * Copyright (C) 1999 WIDE Project.
    7  * All rights reserved.
    8  * 
    9  * Redistribution and use in source and binary forms, with or without
   10  * modification, are permitted provided that the following conditions
   11  * are met:
   12  * 1. Redistributions of source code must retain the above copyright
   13  *    notice, this list of conditions and the following disclaimer.
   14  * 2. Redistributions in binary form must reproduce the above copyright
   15  *    notice, this list of conditions and the following disclaimer in the
   16  *    documentation and/or other materials provided with the distribution.
   17  * 3. Neither the name of the project nor the names of its contributors
   18  *    may be used to endorse or promote products derived from this software
   19  *    without specific prior written permission.
   20  * 
   21  * THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND
   22  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   24  * ARE DISCLAIMED.  IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE
   25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   31  * SUCH DAMAGE.
   32  */
   33 
   34 /*
   35  * Copyright (c) 1982, 1986, 1988, 1991, 1993
   36  *      The Regents of the University of California.  All rights reserved.
   37  *
   38  * Redistribution and use in source and binary forms, with or without
   39  * modification, are permitted provided that the following conditions
   40  * are met:
   41  * 1. Redistributions of source code must retain the above copyright
   42  *    notice, this list of conditions and the following disclaimer.
   43  * 2. Redistributions in binary form must reproduce the above copyright
   44  *    notice, this list of conditions and the following disclaimer in the
   45  *    documentation and/or other materials provided with the distribution.
   46  * 3. All advertising materials mentioning features or use of this software
   47  *    must display the following acknowledgement:
   48  *      This product includes software developed by the University of
   49  *      California, Berkeley and its contributors.
   50  * 4. Neither the name of the University nor the names of its contributors
   51  *    may be used to endorse or promote products derived from this software
   52  *    without specific prior written permission.
   53  *
   54  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   55  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   56  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   57  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   58  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   59  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   60  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   61  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   62  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   63  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   64  * SUCH DAMAGE.
   65  *
   66  *      @(#)uipc_mbuf.c 8.4 (Berkeley) 2/14/95
   67  */
   68 
   69 /*#define PULLDOWN_DEBUG*/
   70 
   71 #include <sys/param.h>
   72 #include <sys/systm.h>
   73 #include <sys/kernel.h>
   74 #include <sys/lock.h>
   75 #include <sys/malloc.h>
   76 #include <sys/mbuf.h>
   77 #include <sys/mutex.h>
   78 
   79 MALLOC_DEFINE(M_PACKET_TAGS, "tag", "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         if (m == NULL)
  103                 panic("m == NULL in m_pulldown()");
  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          * XXX: This code is flawed because it considers a "writable" mbuf
  135          *      data region to require all of the following:
  136          *        (i) mbuf _has_ to have M_EXT set; if it is just a regular
  137          *            mbuf, it is still not considered "writable."
  138          *        (ii) since mbuf has M_EXT, the ext_type _has_ to be
  139          *             EXT_CLUSTER. Anything else makes it non-writable.
  140          *        (iii) M_WRITABLE() must evaluate true.
  141          *      Ideally, the requirement should only be (iii).
  142          *
  143          * If we're writable, we're sure we're writable, because the ref. count
  144          * cannot increase from 1, as that would require posession of mbuf
  145          * n by someone else (which is impossible). However, if we're _not_
  146          * writable, we may eventually become writable )if the ref. count drops
  147          * to 1), but we'll fail to notice it unless we re-evaluate
  148          * M_WRITABLE(). For now, we only evaluate once at the beginning and
  149          * live with this.
  150          */
  151         /*
  152          * XXX: This is dumb. If we're just a regular mbuf with no M_EXT,
  153          *      then we're not "writable," according to this code.
  154          */
  155         writable = 0;
  156         if ((n->m_flags & M_EXT) == 0 ||
  157             (n->m_ext.ext_type == EXT_CLUSTER && M_WRITABLE(n)))
  158                 writable = 1;
  159 
  160         /*
  161          * the target data is on <n, off>.
  162          * if we got enough data on the mbuf "n", we're done.
  163          */
  164         if ((off == 0 || offp) && len <= n->m_len - off && writable)
  165                 goto ok;
  166 
  167         /*
  168          * when len <= n->m_len - off and off != 0, it is a special case.
  169          * len bytes from <n, off> sits in single mbuf, but the caller does
  170          * not like the starting position (off).
  171          * chop the current mbuf into two pieces, set off to 0.
  172          */
  173         if (len <= n->m_len - off) {
  174                 o = m_dup1(n, off, n->m_len - off, M_DONTWAIT);
  175                 if (o == NULL) {
  176                         m_freem(m);
  177                         return NULL;    /* ENOBUFS */
  178                 }
  179                 n->m_len = off;
  180                 o->m_next = n->m_next;
  181                 n->m_next = o;
  182                 n = n->m_next;
  183                 off = 0;
  184                 goto ok;
  185         }
  186 
  187         /*
  188          * we need to take hlen from <n, off> and tlen from <n->m_next, 0>,
  189          * and construct contiguous mbuf with m_len == len.
  190          * note that hlen + tlen == len, and tlen > 0.
  191          */
  192         hlen = n->m_len - off;
  193         tlen = len - hlen;
  194 
  195         /*
  196          * ensure that we have enough trailing data on mbuf chain.
  197          * if not, we can do nothing about the chain.
  198          */
  199         olen = 0;
  200         for (o = n->m_next; o != NULL; o = o->m_next)
  201                 olen += o->m_len;
  202         if (hlen + olen < len) {
  203                 m_freem(m);
  204                 return NULL;    /* mbuf chain too short */
  205         }
  206 
  207         /*
  208          * easy cases first.
  209          * we need to use m_copydata() to get data from <n->m_next, 0>.
  210          */
  211         if ((off == 0 || offp) && M_TRAILINGSPACE(n) >= tlen
  212          && writable) {
  213                 m_copydata(n->m_next, 0, tlen, mtod(n, caddr_t) + n->m_len);
  214                 n->m_len += tlen;
  215                 m_adj(n->m_next, tlen);
  216                 goto ok;
  217         }
  218         if ((off == 0 || offp) && M_LEADINGSPACE(n->m_next) >= hlen
  219          && writable) {
  220                 n->m_next->m_data -= hlen;
  221                 n->m_next->m_len += hlen;
  222                 bcopy(mtod(n, caddr_t) + off, mtod(n->m_next, caddr_t), hlen);
  223                 n->m_len -= hlen;
  224                 n = n->m_next;
  225                 off = 0;
  226                 goto ok;
  227         }
  228 
  229         /*
  230          * now, we need to do the hard way.  don't m_copy as there's no room
  231          * on both end.
  232          */
  233         MGET(o, M_DONTWAIT, m->m_type);
  234         if (o && len > MLEN) {
  235                 MCLGET(o, M_DONTWAIT);
  236                 if ((o->m_flags & M_EXT) == 0) {
  237                         m_free(o);
  238                         o = NULL;
  239                 }
  240         }
  241         if (!o) {
  242                 m_freem(m);
  243                 return NULL;    /* ENOBUFS */
  244         }
  245         /* get hlen from <n, off> into <o, 0> */
  246         o->m_len = hlen;
  247         bcopy(mtod(n, caddr_t) + off, mtod(o, caddr_t), hlen);
  248         n->m_len -= hlen;
  249         /* get tlen from <n->m_next, 0> into <o, hlen> */
  250         m_copydata(n->m_next, 0, tlen, mtod(o, caddr_t) + o->m_len);
  251         o->m_len += tlen;
  252         m_adj(n->m_next, tlen);
  253         o->m_next = n->m_next;
  254         n->m_next = o;
  255         n = o;
  256         off = 0;
  257 
  258 ok:
  259 #ifdef PULLDOWN_DEBUG
  260     {
  261         struct mbuf *t;
  262         printf("after:");
  263         for (t = m; t; t = t->m_next)
  264                 printf("%c%d", t == n ? '*' : ' ', t->m_len);
  265         printf(" (off=%d)\n", off);
  266     }
  267 #endif
  268         if (offp)
  269                 *offp = off;
  270         return n;
  271 }
  272 
  273 static struct mbuf *
  274 m_dup1(struct mbuf *m, int off, int len, int wait)
  275 {
  276         struct mbuf *n;
  277         int l;
  278         int copyhdr;
  279 
  280         if (len > MCLBYTES)
  281                 return NULL;
  282         if (off == 0 && (m->m_flags & M_PKTHDR) != 0) {
  283                 copyhdr = 1;
  284                 MGETHDR(n, wait, m->m_type);
  285                 l = MHLEN;
  286         } else {
  287                 copyhdr = 0;
  288                 MGET(n, wait, m->m_type);
  289                 l = MLEN;
  290         }
  291         if (n && len > l) {
  292                 MCLGET(n, wait);
  293                 if ((n->m_flags & M_EXT) == 0) {
  294                         m_free(n);
  295                         n = NULL;
  296                 }
  297         }
  298         if (!n)
  299                 return NULL;
  300 
  301         if (copyhdr)
  302                 M_COPY_PKTHDR(n, m);
  303         m_copydata(m, off, len, mtod(n, caddr_t));
  304         return n;
  305 }
  306 
  307 /* Get a packet tag structure along with specified data following. */
  308 struct m_tag *
  309 m_tag_alloc(u_int32_t cookie, int type, int len, int wait)
  310 {
  311         struct m_tag *t;
  312 
  313         if (len < 0)
  314                 return NULL;
  315         t = malloc(len + sizeof(struct m_tag), M_PACKET_TAGS, wait);
  316         if (t == NULL)
  317                 return NULL;
  318         t->m_tag_id = type;
  319         t->m_tag_len = len;
  320         t->m_tag_cookie = cookie;
  321         return t;
  322 }
  323 
  324 /* Free a packet tag. */
  325 void
  326 m_tag_free(struct m_tag *t)
  327 {
  328         free(t, M_PACKET_TAGS);
  329 }
  330 
  331 /* Prepend a packet tag. */
  332 void
  333 m_tag_prepend(struct mbuf *m, struct m_tag *t)
  334 {
  335         KASSERT(m && t, ("m_tag_prepend: null argument, m %p t %p", m, t));
  336         SLIST_INSERT_HEAD(&m->m_pkthdr.tags, t, m_tag_link);
  337 }
  338 
  339 /* Unlink a packet tag. */
  340 void
  341 m_tag_unlink(struct mbuf *m, struct m_tag *t)
  342 {
  343         KASSERT(m && t, ("m_tag_unlink: null argument, m %p t %p", m, t));
  344         SLIST_REMOVE(&m->m_pkthdr.tags, t, m_tag, m_tag_link);
  345 }
  346 
  347 /* Unlink and free a packet tag. */
  348 void
  349 m_tag_delete(struct mbuf *m, struct m_tag *t)
  350 {
  351         KASSERT(m && t, ("m_tag_delete: null argument, m %p t %p", m, t));
  352         m_tag_unlink(m, t);
  353         m_tag_free(t);
  354 }
  355 
  356 /* Unlink and free a packet tag chain, starting from given tag. */
  357 void
  358 m_tag_delete_chain(struct mbuf *m, struct m_tag *t)
  359 {
  360         struct m_tag *p, *q;
  361 
  362         KASSERT(m, ("m_tag_delete_chain: null mbuf"));
  363         if (t != NULL)
  364                 p = t;
  365         else
  366                 p = SLIST_FIRST(&m->m_pkthdr.tags);
  367         if (p == NULL)
  368                 return;
  369         while ((q = SLIST_NEXT(p, m_tag_link)) != NULL)
  370                 m_tag_delete(m, q);
  371         m_tag_delete(m, p);
  372 }
  373 
  374 /* Find a tag, starting from a given position. */
  375 struct m_tag *
  376 m_tag_locate(struct mbuf *m, u_int32_t cookie, int type, struct m_tag *t)
  377 {
  378         struct m_tag *p;
  379 
  380         KASSERT(m, ("m_tag_locate: null mbuf"));
  381         if (t == NULL)
  382                 p = SLIST_FIRST(&m->m_pkthdr.tags);
  383         else
  384                 p = SLIST_NEXT(t, m_tag_link);
  385         while (p != NULL) {
  386                 if (p->m_tag_cookie == cookie && p->m_tag_id == type)
  387                         return p;
  388                 p = SLIST_NEXT(p, m_tag_link);
  389         }
  390         return NULL;
  391 }
  392 
  393 /* Copy a single tag. */
  394 struct m_tag *
  395 m_tag_copy(struct m_tag *t)
  396 {
  397         struct m_tag *p;
  398 
  399         KASSERT(t, ("m_tag_copy: null tag"));
  400         p = m_tag_alloc(t->m_tag_cookie, t->m_tag_id, t->m_tag_len, M_NOWAIT);
  401         if (p == NULL)
  402                 return (NULL);
  403         bcopy(t + 1, p + 1, t->m_tag_len); /* Copy the data */
  404         return p;
  405 }
  406 
  407 /*
  408  * Copy two tag chains. The destination mbuf (to) loses any attached
  409  * tags even if the operation fails. This should not be a problem, as
  410  * m_tag_copy_chain() is typically called with a newly-allocated
  411  * destination mbuf.
  412  */
  413 int
  414 m_tag_copy_chain(struct mbuf *to, struct mbuf *from)
  415 {
  416         struct m_tag *p, *t, *tprev = NULL;
  417 
  418         KASSERT(to && from,
  419                 ("m_tag_copy_chain: null argument, to %p from %p", to, from));
  420         m_tag_delete_chain(to, NULL);
  421         SLIST_FOREACH(p, &from->m_pkthdr.tags, m_tag_link) {
  422                 t = m_tag_copy(p);
  423                 if (t == NULL) {
  424                         m_tag_delete_chain(to, NULL);
  425                         return 0;
  426                 }
  427                 if (tprev == NULL)
  428                         SLIST_INSERT_HEAD(&to->m_pkthdr.tags, t, m_tag_link);
  429                 else {
  430                         SLIST_INSERT_AFTER(tprev, t, m_tag_link);
  431                         tprev = t;
  432                 }
  433         }
  434         return 1;
  435 }
  436 
  437 /* Initialize tags on an mbuf. */
  438 void
  439 m_tag_init(struct mbuf *m)
  440 {
  441         SLIST_INIT(&m->m_pkthdr.tags);
  442 }
  443 
  444 /* Get first tag in chain. */
  445 struct m_tag *
  446 m_tag_first(struct mbuf *m)
  447 {
  448         return SLIST_FIRST(&m->m_pkthdr.tags);
  449 }
  450 
  451 /* Get next tag in chain. */
  452 struct m_tag *
  453 m_tag_next(struct mbuf *m, struct m_tag *t)
  454 {
  455         return SLIST_NEXT(t, m_tag_link);
  456 }
Cache object: e100d53b15aa079b0aa697665e6105d4
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FreeBSD/Linux Kernel Cross Reference sys/kern/uipc_mbuf2.c

FreeBSD/Linux Kernel Cross Reference
sys/kern/uipc_mbuf2.c
