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/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: releng/5.1/sys/netipsec/ipsec_mbuf.c 113075 2003-04-04 12:15:20Z des $
   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 extern  struct mbuf *m_getptr(struct mbuf *, int, int *);
   46 
   47 /*
   48  * Create a writable copy of the mbuf chain.  While doing this
   49  * we compact the chain with a goal of producing a chain with
   50  * at most two mbufs.  The second mbuf in this chain is likely
   51  * to be a cluster.  The primary purpose of this work is to create
   52  * a writable packet for encryption, compression, etc.  The
   53  * secondary goal is to linearize the data so the data can be
   54  * passed to crypto hardware in the most efficient manner possible.
   55  */
   56 struct mbuf *
   57 m_clone(struct mbuf *m0)
   58 {
   59         struct mbuf *m, *mprev;
   60         struct mbuf *n, *mfirst, *mlast;
   61         int len, off;
   62 
   63         KASSERT(m0 != NULL, ("m_clone: null mbuf"));
   64 
   65         mprev = NULL;
   66         for (m = m0; m != NULL; m = mprev->m_next) {
   67                 /*
   68                  * Regular mbufs are ignored unless there's a cluster
   69                  * in front of it that we can use to coalesce.  We do
   70                  * the latter mainly so later clusters can be coalesced
   71                  * also w/o having to handle them specially (i.e. convert
   72                  * mbuf+cluster -> cluster).  This optimization is heavily
   73                  * influenced by the assumption that we're running over
   74                  * Ethernet where MCLBYTES is large enough that the max
   75                  * packet size will permit lots of coalescing into a
   76                  * single cluster.  This in turn permits efficient
   77                  * crypto operations, especially when using hardware.
   78                  */
   79                 if ((m->m_flags & M_EXT) == 0) {
   80                         if (mprev && (mprev->m_flags & M_EXT) &&
   81                             m->m_len <= M_TRAILINGSPACE(mprev)) {
   82                                 /* XXX: this ignores mbuf types */
   83                                 memcpy(mtod(mprev, caddr_t) + mprev->m_len,
   84                                        mtod(m, caddr_t), m->m_len);
   85                                 mprev->m_len += m->m_len;
   86                                 mprev->m_next = m->m_next;      /* unlink from chain */
   87                                 m_free(m);                      /* reclaim mbuf */
   88                                 newipsecstat.ips_mbcoalesced++;
   89                         } else {
   90                                 mprev = m;
   91                         }
   92                         continue;
   93                 }
   94                 /*
   95                  * Writable mbufs are left alone (for now).
   96                  */
   97                 if (!MEXT_IS_REF(m)) {
   98                         mprev = m;
   99                         continue;
  100                 }
  101 
  102                 /*
  103                  * Not writable, replace with a copy or coalesce with
  104                  * the previous mbuf if possible (since we have to copy
  105                  * it anyway, we try to reduce the number of mbufs and
  106                  * clusters so that future work is easier).
  107                  */
  108                 KASSERT(m->m_flags & M_EXT,
  109                         ("m_clone: m_flags 0x%x", m->m_flags));
  110                 /* NB: we only coalesce into a cluster or larger */
  111                 if (mprev != NULL && (mprev->m_flags & M_EXT) &&
  112                     m->m_len <= M_TRAILINGSPACE(mprev)) {
  113                         /* XXX: this ignores mbuf types */
  114                         memcpy(mtod(mprev, caddr_t) + mprev->m_len,
  115                                mtod(m, caddr_t), m->m_len);
  116                         mprev->m_len += m->m_len;
  117                         mprev->m_next = m->m_next;      /* unlink from chain */
  118                         m_free(m);                      /* reclaim mbuf */
  119                         newipsecstat.ips_clcoalesced++;
  120                         continue;
  121                 }
  122 
  123                 /*
  124                  * Allocate new space to hold the copy...
  125                  */
  126                 /* XXX why can M_PKTHDR be set past the first mbuf? */
  127                 if (mprev == NULL && (m->m_flags & M_PKTHDR)) {
  128                         /*
  129                          * NB: if a packet header is present we must
  130                          * allocate the mbuf separately from any cluster
  131                          * because M_MOVE_PKTHDR will smash the data
  132                          * pointer and drop the M_EXT marker.
  133                          */
  134                         MGETHDR(n, M_DONTWAIT, m->m_type);
  135                         if (n == NULL) {
  136                                 m_freem(m0);
  137                                 return (NULL);
  138                         }
  139                         M_MOVE_PKTHDR(n, m);
  140                         MCLGET(n, M_DONTWAIT);
  141                         if ((n->m_flags & M_EXT) == 0) {
  142                                 m_free(n);
  143                                 m_freem(m0);
  144                                 return (NULL);
  145                         }
  146                 } else {
  147                         n = m_getcl(M_DONTWAIT, m->m_type, m->m_flags);
  148                         if (n == NULL) {
  149                                 m_freem(m0);
  150                                 return (NULL);
  151                         }
  152                 }
  153                 /*
  154                  * ... and copy the data.  We deal with jumbo mbufs
  155                  * (i.e. m_len > MCLBYTES) by splitting them into
  156                  * clusters.  We could just malloc a buffer and make
  157                  * it external but too many device drivers don't know
  158                  * how to break up the non-contiguous memory when
  159                  * doing DMA.
  160                  */
  161                 len = m->m_len;
  162                 off = 0;
  163                 mfirst = n;
  164                 mlast = NULL;
  165                 for (;;) {
  166                         int cc = min(len, MCLBYTES);
  167                         memcpy(mtod(n, caddr_t), mtod(m, caddr_t) + off, cc);
  168                         n->m_len = cc;
  169                         if (mlast != NULL)
  170                                 mlast->m_next = n;
  171                         mlast = n;      
  172                         newipsecstat.ips_clcopied++;
  173 
  174                         len -= cc;
  175                         if (len <= 0)
  176                                 break;
  177                         off += cc;
  178 
  179                         n = m_getcl(M_DONTWAIT, m->m_type, m->m_flags);
  180                         if (n == NULL) {
  181                                 m_freem(mfirst);
  182                                 m_freem(m0);
  183                                 return (NULL);
  184                         }
  185                 }
  186                 n->m_next = m->m_next; 
  187                 if (mprev == NULL)
  188                         m0 = mfirst;            /* new head of chain */
  189                 else
  190                         mprev->m_next = mfirst; /* replace old mbuf */
  191                 m_free(m);                      /* release old mbuf */
  192                 mprev = mfirst;
  193         }
  194         return (m0);
  195 }
  196 
  197 /*
  198  * Make space for a new header of length hlen at skip bytes
  199  * into the packet.  When doing this we allocate new mbufs only
  200  * when absolutely necessary.  The mbuf where the new header
  201  * is to go is returned together with an offset into the mbuf.
  202  * If NULL is returned then the mbuf chain may have been modified;
  203  * the caller is assumed to always free the chain.
  204  */
  205 struct mbuf *
  206 m_makespace(struct mbuf *m0, int skip, int hlen, int *off)
  207 {
  208         struct mbuf *m;
  209         unsigned remain;
  210 
  211         KASSERT(m0 != NULL, ("m_dmakespace: null mbuf"));
  212         KASSERT(hlen < MHLEN, ("m_makespace: hlen too big: %u", hlen));
  213 
  214         for (m = m0; m && skip > m->m_len; m = m->m_next)
  215                 skip -= m->m_len;
  216         if (m == NULL)
  217                 return (NULL);
  218         /*
  219          * At this point skip is the offset into the mbuf m
  220          * where the new header should be placed.  Figure out
  221          * if there's space to insert the new header.  If so,
  222          * and copying the remainder makese sense then do so.
  223          * Otherwise insert a new mbuf in the chain, splitting
  224          * the contents of m as needed.
  225          */
  226         remain = m->m_len - skip;               /* data to move */
  227         if (hlen > M_TRAILINGSPACE(m)) {
  228                 struct mbuf *n;
  229 
  230                 /* XXX code doesn't handle clusters XXX */
  231                 KASSERT(remain < MLEN,
  232                         ("m_makespace: remainder too big: %u", remain));
  233                 /*
  234                  * Not enough space in m, split the contents
  235                  * of m, inserting new mbufs as required.
  236                  *
  237                  * NB: this ignores mbuf types.
  238                  */
  239                 MGET(n, M_DONTWAIT, MT_DATA);
  240                 if (n == NULL)
  241                         return (NULL);
  242                 n->m_next = m->m_next;          /* splice new mbuf */
  243                 m->m_next = n;
  244                 newipsecstat.ips_mbinserted++;
  245                 if (hlen <= M_TRAILINGSPACE(m) + remain) {
  246                         /*
  247                          * New header fits in the old mbuf if we copy
  248                          * the remainder; just do the copy to the new
  249                          * mbuf and we're good to go.
  250                          */
  251                         memcpy(mtod(n, caddr_t),
  252                                mtod(m, caddr_t) + skip, remain);
  253                         n->m_len = remain;
  254                         m->m_len = skip + hlen;
  255                         *off = skip;
  256                 } else {
  257                         /*
  258                          * No space in the old mbuf for the new header.
  259                          * Make space in the new mbuf and check the
  260                          * remainder'd data fits too.  If not then we
  261                          * must allocate an additional mbuf (yech).
  262                          */
  263                         n->m_len = 0;
  264                         if (remain + hlen > M_TRAILINGSPACE(n)) {
  265                                 struct mbuf *n2;
  266 
  267                                 MGET(n2, M_DONTWAIT, MT_DATA);
  268                                 /* NB: new mbuf is on chain, let caller free */
  269                                 if (n2 == NULL)
  270                                         return (NULL);
  271                                 n2->m_len = 0;
  272                                 memcpy(mtod(n2, caddr_t),
  273                                        mtod(m, caddr_t) + skip, remain);
  274                                 n2->m_len = remain;
  275                                 /* splice in second mbuf */
  276                                 n2->m_next = n->m_next;
  277                                 n->m_next = n2;
  278                                 newipsecstat.ips_mbinserted++;
  279                         } else {
  280                                 memcpy(mtod(n, caddr_t) + hlen,
  281                                        mtod(m, caddr_t) + skip, remain);
  282                                 n->m_len += remain;
  283                         }
  284                         m->m_len -= remain;
  285                         n->m_len += hlen;
  286                         m = n;                  /* header is at front ... */
  287                         *off = 0;               /* ... of new mbuf */
  288                 }
  289         } else {
  290                 /*
  291                  * Copy the remainder to the back of the mbuf
  292                  * so there's space to write the new header.
  293                  */
  294                 bcopy(mtod(m, caddr_t) + skip,
  295                       mtod(m, caddr_t) + skip + hlen, remain);
  296                 m->m_len += hlen;
  297                 *off = skip;
  298         }
  299         m0->m_pkthdr.len += hlen;               /* adjust packet length */
  300         return m;
  301 }
  302 
  303 /*
  304  * m_pad(m, n) pads <m> with <n> bytes at the end. The packet header
  305  * length is updated, and a pointer to the first byte of the padding
  306  * (which is guaranteed to be all in one mbuf) is returned.
  307  */
  308 caddr_t
  309 m_pad(struct mbuf *m, int n)
  310 {
  311         register struct mbuf *m0, *m1;
  312         register int len, pad;
  313         caddr_t retval;
  314 
  315         if (n <= 0) {  /* No stupid arguments. */
  316                 DPRINTF(("m_pad: pad length invalid (%d)\n", n));
  317                 m_freem(m);
  318                 return NULL;
  319         }
  320 
  321         len = m->m_pkthdr.len;
  322         pad = n;
  323         m0 = m;
  324 
  325         while (m0->m_len < len) {
  326 KASSERT(m0->m_next != NULL, ("m_pad: m0 null, len %u m_len %u", len, m0->m_len));/*XXX*/
  327                 len -= m0->m_len;
  328                 m0 = m0->m_next;
  329         }
  330 
  331         if (m0->m_len != len) {
  332                 DPRINTF(("m_pad: length mismatch (should be %d instead of %d)\n",
  333                     m->m_pkthdr.len, m->m_pkthdr.len + m0->m_len - len));
  334 
  335                 m_freem(m);
  336                 return NULL;
  337         }
  338 
  339         /* Check for zero-length trailing mbufs, and find the last one. */
  340         for (m1 = m0; m1->m_next; m1 = m1->m_next) {
  341                 if (m1->m_next->m_len != 0) {
  342                         DPRINTF(("m_pad: length mismatch (should be %d "
  343                             "instead of %d)\n",
  344                             m->m_pkthdr.len,
  345                             m->m_pkthdr.len + m1->m_next->m_len));
  346 
  347                         m_freem(m);
  348                         return NULL;
  349                 }
  350 
  351                 m0 = m1->m_next;
  352         }
  353 
  354         if (pad > M_TRAILINGSPACE(m0)) {
  355                 /* Add an mbuf to the chain. */
  356                 MGET(m1, M_DONTWAIT, MT_DATA);
  357                 if (m1 == 0) {
  358                         m_freem(m0);
  359                         DPRINTF(("m_pad: unable to get extra mbuf\n"));
  360                         return NULL;
  361                 }
  362 
  363                 m0->m_next = m1;
  364                 m0 = m1;
  365                 m0->m_len = 0;
  366         }
  367 
  368         retval = m0->m_data + m0->m_len;
  369         m0->m_len += pad;
  370         m->m_pkthdr.len += pad;
  371 
  372         return retval;
  373 }
  374 
  375 /*
  376  * Remove hlen data at offset skip in the packet.  This is used by
  377  * the protocols strip protocol headers and associated data (e.g. IV,
  378  * authenticator) on input.
  379  */
  380 int
  381 m_striphdr(struct mbuf *m, int skip, int hlen)
  382 {
  383         struct mbuf *m1;
  384         int roff;
  385 
  386         /* Find beginning of header */
  387         m1 = m_getptr(m, skip, &roff);
  388         if (m1 == NULL)
  389                 return (EINVAL);
  390 
  391         /* Remove the header and associated data from the mbuf. */
  392         if (roff == 0) {
  393                 /* The header was at the beginning of the mbuf */
  394                 newipsecstat.ips_input_front++;
  395                 m_adj(m1, hlen);
  396                 if ((m1->m_flags & M_PKTHDR) == 0)
  397                         m->m_pkthdr.len -= hlen;
  398         } else if (roff + hlen >= m1->m_len) {
  399                 struct mbuf *mo;
  400 
  401                 /*
  402                  * Part or all of the header is at the end of this mbuf,
  403                  * so first let's remove the remainder of the header from
  404                  * the beginning of the remainder of the mbuf chain, if any.
  405                  */
  406                 newipsecstat.ips_input_end++;
  407                 if (roff + hlen > m1->m_len) {
  408                         /* Adjust the next mbuf by the remainder */
  409                         m_adj(m1->m_next, roff + hlen - m1->m_len);
  410 
  411                         /* The second mbuf is guaranteed not to have a pkthdr... */
  412                         m->m_pkthdr.len -= (roff + hlen - m1->m_len);
  413                 }
  414 
  415                 /* Now, let's unlink the mbuf chain for a second...*/
  416                 mo = m1->m_next;
  417                 m1->m_next = NULL;
  418 
  419                 /* ...and trim the end of the first part of the chain...sick */
  420                 m_adj(m1, -(m1->m_len - roff));
  421                 if ((m1->m_flags & M_PKTHDR) == 0)
  422                         m->m_pkthdr.len -= (m1->m_len - roff);
  423 
  424                 /* Finally, let's relink */
  425                 m1->m_next = mo;
  426         } else {
  427                 /*
  428                  * The header lies in the "middle" of the mbuf; copy
  429                  * the remainder of the mbuf down over the header.
  430                  */
  431                 newipsecstat.ips_input_middle++;
  432                 bcopy(mtod(m1, u_char *) + roff + hlen,
  433                       mtod(m1, u_char *) + roff,
  434                       m1->m_len - (roff + hlen));
  435                 m1->m_len -= hlen;
  436                 m->m_pkthdr.len -= hlen;
  437         }
  438         return (0);
  439 }
  440 
  441 /*
  442  * Diagnostic routine to check mbuf alignment as required by the
  443  * crypto device drivers (that use DMA).
  444  */
  445 void
  446 m_checkalignment(const char* where, struct mbuf *m0, int off, int len)
  447 {
  448         int roff;
  449         struct mbuf *m = m_getptr(m0, off, &roff);
  450         caddr_t addr;
  451 
  452         if (m == NULL)
  453                 return;
  454         printf("%s (off %u len %u): ", where, off, len);
  455         addr = mtod(m, caddr_t) + roff;
  456         do {
  457                 int mlen;
  458 
  459                 if (((uintptr_t) addr) & 3) {
  460                         printf("addr misaligned %p,", addr);
  461                         break;
  462                 }
  463                 mlen = m->m_len;
  464                 if (mlen > len)
  465                         mlen = len;
  466                 len -= mlen;
  467                 if (len && (mlen & 3)) {
  468                         printf("len mismatch %u,", mlen);
  469                         break;
  470                 }
  471                 m = m->m_next;
  472                 addr = m ? mtod(m, caddr_t) : NULL;
  473         } while (m && len > 0);
  474         for (m = m0; m; m = m->m_next)
  475                 printf(" [%p:%u]", mtod(m, caddr_t), m->m_len);
  476         printf("\n");
  477 }

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