The Design and Implementation of the FreeBSD Operating System, Second Edition
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FreeBSD/Linux Kernel Cross Reference
sys/netipsec/ipsec_mbuf.c

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    1 /*-
    2  * Copyright (c) 2002, 2003 Sam Leffler, Errno Consulting
    3  * 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  *
   14  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
   15  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   16  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   17  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
   18  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   19  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   20  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   21  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   22  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   23  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   24  * SUCH DAMAGE.
   25  *
   26  * $FreeBSD: src/sys/netipsec/ipsec_mbuf.c,v 1.10 2003/12/15 21:49:41 bms Exp $
   27  */
   28 
   29 /*
   30  * IPsec-specific mbuf routines.
   31  */
   32 
   33 #include "opt_param.h"
   34 
   35 #include <sys/param.h>
   36 #include <sys/systm.h>
   37 #include <sys/mbuf.h>
   38 #include <sys/socket.h>
   39 
   40 #include <net/route.h>
   41 #include <netinet/in.h>
   42 
   43 #include <netipsec/ipsec.h>
   44 
   45 /*
   46  * Create a writable copy of the mbuf chain.  While doing this
   47  * we compact the chain with a goal of producing a chain with
   48  * at most two mbufs.  The second mbuf in this chain is likely
   49  * to be a cluster.  The primary purpose of this work is to create
   50  * a writable packet for encryption, compression, etc.  The
   51  * secondary goal is to linearize the data so the data can be
   52  * passed to crypto hardware in the most efficient manner possible.
   53  */
   54 struct mbuf *
   55 m_clone(struct mbuf *m0)
   56 {
   57         struct mbuf *m, *mprev;
   58         struct mbuf *n, *mfirst, *mlast;
   59         int len, off;
   60 
   61         IPSEC_ASSERT(m0 != NULL, ("null mbuf"));
   62 
   63         mprev = NULL;
   64         for (m = m0; m != NULL; m = mprev->m_next) {
   65                 /*
   66                  * Regular mbufs are ignored unless there's a cluster
   67                  * in front of it that we can use to coalesce.  We do
   68                  * the latter mainly so later clusters can be coalesced
   69                  * also w/o having to handle them specially (i.e. convert
   70                  * mbuf+cluster -> cluster).  This optimization is heavily
   71                  * influenced by the assumption that we're running over
   72                  * Ethernet where MCLBYTES is large enough that the max
   73                  * packet size will permit lots of coalescing into a
   74                  * single cluster.  This in turn permits efficient
   75                  * crypto operations, especially when using hardware.
   76                  */
   77                 if ((m->m_flags & M_EXT) == 0) {
   78                         if (mprev && (mprev->m_flags & M_EXT) &&
   79                             m->m_len <= M_TRAILINGSPACE(mprev)) {
   80                                 /* XXX: this ignores mbuf types */
   81                                 memcpy(mtod(mprev, caddr_t) + mprev->m_len,
   82                                        mtod(m, caddr_t), m->m_len);
   83                                 mprev->m_len += m->m_len;
   84                                 mprev->m_next = m->m_next;      /* unlink from chain */
   85                                 m_free(m);                      /* reclaim mbuf */
   86                                 newipsecstat.ips_mbcoalesced++;
   87                         } else {
   88                                 mprev = m;
   89                         }
   90                         continue;
   91                 }
   92                 /*
   93                  * Writable mbufs are left alone (for now).
   94                  */
   95                 if (!MEXT_IS_REF(m)) {
   96                         mprev = m;
   97                         continue;
   98                 }
   99 
  100                 /*
  101                  * Not writable, replace with a copy or coalesce with
  102                  * the previous mbuf if possible (since we have to copy
  103                  * it anyway, we try to reduce the number of mbufs and
  104                  * clusters so that future work is easier).
  105                  */
  106                 IPSEC_ASSERT(m->m_flags & M_EXT, ("m_flags 0x%x", m->m_flags));
  107                 /* NB: we only coalesce into a cluster or larger */
  108                 if (mprev != NULL && (mprev->m_flags & M_EXT) &&
  109                     m->m_len <= M_TRAILINGSPACE(mprev)) {
  110                         /* XXX: this ignores mbuf types */
  111                         memcpy(mtod(mprev, caddr_t) + mprev->m_len,
  112                                mtod(m, caddr_t), m->m_len);
  113                         mprev->m_len += m->m_len;
  114                         mprev->m_next = m->m_next;      /* unlink from chain */
  115                         m_free(m);                      /* reclaim mbuf */
  116                         newipsecstat.ips_clcoalesced++;
  117                         continue;
  118                 }
  119 
  120                 /*
  121                  * Allocate new space to hold the copy...
  122                  */
  123                 /* XXX why can M_PKTHDR be set past the first mbuf? */
  124                 if (mprev == NULL && (m->m_flags & M_PKTHDR)) {
  125                         /*
  126                          * NB: if a packet header is present we must
  127                          * allocate the mbuf separately from any cluster
  128                          * because M_MOVE_PKTHDR will smash the data
  129                          * pointer and drop the M_EXT marker.
  130                          */
  131                         MGETHDR(n, M_DONTWAIT, m->m_type);
  132                         if (n == NULL) {
  133                                 m_freem(m0);
  134                                 return (NULL);
  135                         }
  136                         M_MOVE_PKTHDR(n, m);
  137                         MCLGET(n, M_DONTWAIT);
  138                         if ((n->m_flags & M_EXT) == 0) {
  139                                 m_free(n);
  140                                 m_freem(m0);
  141                                 return (NULL);
  142                         }
  143                 } else {
  144                         n = m_getcl(M_DONTWAIT, m->m_type, m->m_flags);
  145                         if (n == NULL) {
  146                                 m_freem(m0);
  147                                 return (NULL);
  148                         }
  149                 }
  150                 /*
  151                  * ... and copy the data.  We deal with jumbo mbufs
  152                  * (i.e. m_len > MCLBYTES) by splitting them into
  153                  * clusters.  We could just malloc a buffer and make
  154                  * it external but too many device drivers don't know
  155                  * how to break up the non-contiguous memory when
  156                  * doing DMA.
  157                  */
  158                 len = m->m_len;
  159                 off = 0;
  160                 mfirst = n;
  161                 mlast = NULL;
  162                 for (;;) {
  163                         int cc = min(len, MCLBYTES);
  164                         memcpy(mtod(n, caddr_t), mtod(m, caddr_t) + off, cc);
  165                         n->m_len = cc;
  166                         if (mlast != NULL)
  167                                 mlast->m_next = n;
  168                         mlast = n;      
  169                         newipsecstat.ips_clcopied++;
  170 
  171                         len -= cc;
  172                         if (len <= 0)
  173                                 break;
  174                         off += cc;
  175 
  176                         n = m_getcl(M_DONTWAIT, m->m_type, m->m_flags);
  177                         if (n == NULL) {
  178                                 m_freem(mfirst);
  179                                 m_freem(m0);
  180                                 return (NULL);
  181                         }
  182                 }
  183                 n->m_next = m->m_next; 
  184                 if (mprev == NULL)
  185                         m0 = mfirst;            /* new head of chain */
  186                 else
  187                         mprev->m_next = mfirst; /* replace old mbuf */
  188                 m_free(m);                      /* release old mbuf */
  189                 mprev = mfirst;
  190         }
  191         return (m0);
  192 }
  193 
  194 /*
  195  * Make space for a new header of length hlen at skip bytes
  196  * into the packet.  When doing this we allocate new mbufs only
  197  * when absolutely necessary.  The mbuf where the new header
  198  * is to go is returned together with an offset into the mbuf.
  199  * If NULL is returned then the mbuf chain may have been modified;
  200  * the caller is assumed to always free the chain.
  201  */
  202 struct mbuf *
  203 m_makespace(struct mbuf *m0, int skip, int hlen, int *off)
  204 {
  205         struct mbuf *m;
  206         unsigned remain;
  207 
  208         IPSEC_ASSERT(m0 != NULL, ("null mbuf"));
  209         IPSEC_ASSERT(hlen < MHLEN, ("hlen too big: %u", hlen));
  210 
  211         for (m = m0; m && skip > m->m_len; m = m->m_next)
  212                 skip -= m->m_len;
  213         if (m == NULL)
  214                 return (NULL);
  215         /*
  216          * At this point skip is the offset into the mbuf m
  217          * where the new header should be placed.  Figure out
  218          * if there's space to insert the new header.  If so,
  219          * and copying the remainder makese sense then do so.
  220          * Otherwise insert a new mbuf in the chain, splitting
  221          * the contents of m as needed.
  222          */
  223         remain = m->m_len - skip;               /* data to move */
  224         if (hlen > M_TRAILINGSPACE(m)) {
  225                 struct mbuf *n;
  226 
  227                 /* XXX code doesn't handle clusters XXX */
  228                 IPSEC_ASSERT(remain < MLEN, ("remainder too big: %u", remain));
  229                 /*
  230                  * Not enough space in m, split the contents
  231                  * of m, inserting new mbufs as required.
  232                  *
  233                  * NB: this ignores mbuf types.
  234                  */
  235                 MGET(n, M_DONTWAIT, MT_DATA);
  236                 if (n == NULL)
  237                         return (NULL);
  238                 n->m_next = m->m_next;          /* splice new mbuf */
  239                 m->m_next = n;
  240                 newipsecstat.ips_mbinserted++;
  241                 if (hlen <= M_TRAILINGSPACE(m) + remain) {
  242                         /*
  243                          * New header fits in the old mbuf if we copy
  244                          * the remainder; just do the copy to the new
  245                          * mbuf and we're good to go.
  246                          */
  247                         memcpy(mtod(n, caddr_t),
  248                                mtod(m, caddr_t) + skip, remain);
  249                         n->m_len = remain;
  250                         m->m_len = skip + hlen;
  251                         *off = skip;
  252                 } else {
  253                         /*
  254                          * No space in the old mbuf for the new header.
  255                          * Make space in the new mbuf and check the
  256                          * remainder'd data fits too.  If not then we
  257                          * must allocate an additional mbuf (yech).
  258                          */
  259                         n->m_len = 0;
  260                         if (remain + hlen > M_TRAILINGSPACE(n)) {
  261                                 struct mbuf *n2;
  262 
  263                                 MGET(n2, M_DONTWAIT, MT_DATA);
  264                                 /* NB: new mbuf is on chain, let caller free */
  265                                 if (n2 == NULL)
  266                                         return (NULL);
  267                                 n2->m_len = 0;
  268                                 memcpy(mtod(n2, caddr_t),
  269                                        mtod(m, caddr_t) + skip, remain);
  270                                 n2->m_len = remain;
  271                                 /* splice in second mbuf */
  272                                 n2->m_next = n->m_next;
  273                                 n->m_next = n2;
  274                                 newipsecstat.ips_mbinserted++;
  275                         } else {
  276                                 memcpy(mtod(n, caddr_t) + hlen,
  277                                        mtod(m, caddr_t) + skip, remain);
  278                                 n->m_len += remain;
  279                         }
  280                         m->m_len -= remain;
  281                         n->m_len += hlen;
  282                         m = n;                  /* header is at front ... */
  283                         *off = 0;               /* ... of new mbuf */
  284                 }
  285         } else {
  286                 /*
  287                  * Copy the remainder to the back of the mbuf
  288                  * so there's space to write the new header.
  289                  */
  290                 bcopy(mtod(m, caddr_t) + skip,
  291                       mtod(m, caddr_t) + skip + hlen, remain);
  292                 m->m_len += hlen;
  293                 *off = skip;
  294         }
  295         m0->m_pkthdr.len += hlen;               /* adjust packet length */
  296         return m;
  297 }
  298 
  299 /*
  300  * m_pad(m, n) pads <m> with <n> bytes at the end. The packet header
  301  * length is updated, and a pointer to the first byte of the padding
  302  * (which is guaranteed to be all in one mbuf) is returned.
  303  */
  304 caddr_t
  305 m_pad(struct mbuf *m, int n)
  306 {
  307         register struct mbuf *m0, *m1;
  308         register int len, pad;
  309         caddr_t retval;
  310 
  311         if (n <= 0) {  /* No stupid arguments. */
  312                 DPRINTF(("%s: pad length invalid (%d)\n", __func__, n));
  313                 m_freem(m);
  314                 return NULL;
  315         }
  316 
  317         len = m->m_pkthdr.len;
  318         pad = n;
  319         m0 = m;
  320 
  321         while (m0->m_len < len) {
  322                 len -= m0->m_len;
  323                 m0 = m0->m_next;
  324         }
  325 
  326         if (m0->m_len != len) {
  327                 DPRINTF(("%s: length mismatch (should be %d instead of %d)\n",
  328                         __func__, m->m_pkthdr.len,
  329                         m->m_pkthdr.len + m0->m_len - len));
  330 
  331                 m_freem(m);
  332                 return NULL;
  333         }
  334 
  335         /* Check for zero-length trailing mbufs, and find the last one. */
  336         for (m1 = m0; m1->m_next; m1 = m1->m_next) {
  337                 if (m1->m_next->m_len != 0) {
  338                         DPRINTF(("%s: length mismatch (should be %d instead "
  339                                 "of %d)\n", __func__,
  340                                 m->m_pkthdr.len,
  341                                 m->m_pkthdr.len + m1->m_next->m_len));
  342 
  343                         m_freem(m);
  344                         return NULL;
  345                 }
  346 
  347                 m0 = m1->m_next;
  348         }
  349 
  350         if (pad > M_TRAILINGSPACE(m0)) {
  351                 /* Add an mbuf to the chain. */
  352                 MGET(m1, M_DONTWAIT, MT_DATA);
  353                 if (m1 == 0) {
  354                         m_freem(m0);
  355                         DPRINTF(("%s: unable to get extra mbuf\n", __func__));
  356                         return NULL;
  357                 }
  358 
  359                 m0->m_next = m1;
  360                 m0 = m1;
  361                 m0->m_len = 0;
  362         }
  363 
  364         retval = m0->m_data + m0->m_len;
  365         m0->m_len += pad;
  366         m->m_pkthdr.len += pad;
  367 
  368         return retval;
  369 }
  370 
  371 /*
  372  * Remove hlen data at offset skip in the packet.  This is used by
  373  * the protocols strip protocol headers and associated data (e.g. IV,
  374  * authenticator) on input.
  375  */
  376 int
  377 m_striphdr(struct mbuf *m, int skip, int hlen)
  378 {
  379         struct mbuf *m1;
  380         int roff;
  381 
  382         /* Find beginning of header */
  383         m1 = m_getptr(m, skip, &roff);
  384         if (m1 == NULL)
  385                 return (EINVAL);
  386 
  387         /* Remove the header and associated data from the mbuf. */
  388         if (roff == 0) {
  389                 /* The header was at the beginning of the mbuf */
  390                 newipsecstat.ips_input_front++;
  391                 m_adj(m1, hlen);
  392                 if ((m1->m_flags & M_PKTHDR) == 0)
  393                         m->m_pkthdr.len -= hlen;
  394         } else if (roff + hlen >= m1->m_len) {
  395                 struct mbuf *mo;
  396 
  397                 /*
  398                  * Part or all of the header is at the end of this mbuf,
  399                  * so first let's remove the remainder of the header from
  400                  * the beginning of the remainder of the mbuf chain, if any.
  401                  */
  402                 newipsecstat.ips_input_end++;
  403                 if (roff + hlen > m1->m_len) {
  404                         /* Adjust the next mbuf by the remainder */
  405                         m_adj(m1->m_next, roff + hlen - m1->m_len);
  406 
  407                         /* The second mbuf is guaranteed not to have a pkthdr... */
  408                         m->m_pkthdr.len -= (roff + hlen - m1->m_len);
  409                 }
  410 
  411                 /* Now, let's unlink the mbuf chain for a second...*/
  412                 mo = m1->m_next;
  413                 m1->m_next = NULL;
  414 
  415                 /* ...and trim the end of the first part of the chain...sick */
  416                 m_adj(m1, -(m1->m_len - roff));
  417                 if ((m1->m_flags & M_PKTHDR) == 0)
  418                         m->m_pkthdr.len -= (m1->m_len - roff);
  419 
  420                 /* Finally, let's relink */
  421                 m1->m_next = mo;
  422         } else {
  423                 /*
  424                  * The header lies in the "middle" of the mbuf; copy
  425                  * the remainder of the mbuf down over the header.
  426                  */
  427                 newipsecstat.ips_input_middle++;
  428                 bcopy(mtod(m1, u_char *) + roff + hlen,
  429                       mtod(m1, u_char *) + roff,
  430                       m1->m_len - (roff + hlen));
  431                 m1->m_len -= hlen;
  432                 m->m_pkthdr.len -= hlen;
  433         }
  434         return (0);
  435 }
  436 
  437 /*
  438  * Diagnostic routine to check mbuf alignment as required by the
  439  * crypto device drivers (that use DMA).
  440  */
  441 void
  442 m_checkalignment(const char* where, struct mbuf *m0, int off, int len)
  443 {
  444         int roff;
  445         struct mbuf *m = m_getptr(m0, off, &roff);
  446         caddr_t addr;
  447 
  448         if (m == NULL)
  449                 return;
  450         printf("%s (off %u len %u): ", where, off, len);
  451         addr = mtod(m, caddr_t) + roff;
  452         do {
  453                 int mlen;
  454 
  455                 if (((uintptr_t) addr) & 3) {
  456                         printf("addr misaligned %p,", addr);
  457                         break;
  458                 }
  459                 mlen = m->m_len;
  460                 if (mlen > len)
  461                         mlen = len;
  462                 len -= mlen;
  463                 if (len && (mlen & 3)) {
  464                         printf("len mismatch %u,", mlen);
  465                         break;
  466                 }
  467                 m = m->m_next;
  468                 addr = m ? mtod(m, caddr_t) : NULL;
  469         } while (m && len > 0);
  470         for (m = m0; m; m = m->m_next)
  471                 printf(" [%p:%u]", mtod(m, caddr_t), m->m_len);
  472         printf("\n");
  473 }

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