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: stable/4/sys/netipsec/ipsec_mbuf.c 125661 2004-02-10 17:37:11Z bms $
   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         KASSERT(m0 != NULL, ("m_clone: 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).  Note
   94                  * that for 4.x systems it's not possible to identify
   95                  * whether or not mbufs with external buffers are
   96                  * writable unless they use clusters.
   97                  */
   98                 if (M_EXT_WRITABLE(m)) {
   99                         mprev = m;
  100                         continue;
  101                 }
  102 
  103                 /*
  104                  * Not writable, replace with a copy or coalesce with
  105                  * the previous mbuf if possible (since we have to copy
  106                  * it anyway, we try to reduce the number of mbufs and
  107                  * clusters so that future work is easier).
  108                  */
  109                 KASSERT(m->m_flags & M_EXT,
  110                         ("m_clone: m_flags 0x%x", m->m_flags));
  111                 /* NB: we only coalesce into a cluster or larger */
  112                 if (mprev != NULL && (mprev->m_flags & M_EXT) &&
  113                     m->m_len <= M_TRAILINGSPACE(mprev)) {
  114                         /* XXX: this ignores mbuf types */
  115                         memcpy(mtod(mprev, caddr_t) + mprev->m_len,
  116                                mtod(m, caddr_t), m->m_len);
  117                         mprev->m_len += m->m_len;
  118                         mprev->m_next = m->m_next;      /* unlink from chain */
  119                         m_free(m);                      /* reclaim mbuf */
  120                         newipsecstat.ips_clcoalesced++;
  121                         continue;
  122                 }
  123 
  124                 /*
  125                  * Allocate new space to hold the copy...
  126                  */
  127                 /* XXX why can M_PKTHDR be set past the first mbuf? */
  128                 if (mprev == NULL && (m->m_flags & M_PKTHDR)) {
  129                         /*
  130                          * NB: if a packet header is present we must
  131                          * allocate the mbuf separately from any cluster
  132                          * because M_MOVE_PKTHDR will smash the data
  133                          * pointer and drop the M_EXT marker.
  134                          */
  135                         MGETHDR(n, M_DONTWAIT, m->m_type);
  136                         if (n == NULL) {
  137                                 m_freem(m0);
  138                                 return (NULL);
  139                         }
  140                         M_MOVE_PKTHDR(n, m);
  141                         MCLGET(n, M_DONTWAIT);
  142                         if ((n->m_flags & M_EXT) == 0) {
  143                                 m_free(n);
  144                                 m_freem(m0);
  145                                 return (NULL);
  146                         }
  147                 } else {
  148                         n = m_getcl(M_DONTWAIT, m->m_type, m->m_flags);
  149                         if (n == NULL) {
  150                                 m_freem(m0);
  151                                 return (NULL);
  152                         }
  153                 }
  154                 /*
  155                  * ... and copy the data.  We deal with jumbo mbufs
  156                  * (i.e. m_len > MCLBYTES) by splitting them into
  157                  * clusters.  We could just malloc a buffer and make
  158                  * it external but too many device drivers don't know
  159                  * how to break up the non-contiguous memory when
  160                  * doing DMA.
  161                  */
  162                 len = m->m_len;
  163                 off = 0;
  164                 mfirst = n;
  165                 mlast = NULL;
  166                 for (;;) {
  167                         int cc = min(len, MCLBYTES);
  168                         memcpy(mtod(n, caddr_t), mtod(m, caddr_t) + off, cc);
  169                         n->m_len = cc;
  170                         if (mlast != NULL)
  171                                 mlast->m_next = n;
  172                         mlast = n;      
  173                         newipsecstat.ips_clcopied++;
  174 
  175                         len -= cc;
  176                         if (len <= 0)
  177                                 break;
  178                         off += cc;
  179 
  180                         n = m_getcl(M_DONTWAIT, m->m_type, m->m_flags);
  181                         if (n == NULL) {
  182                                 m_freem(mfirst);
  183                                 m_freem(m0);
  184                                 return (NULL);
  185                         }
  186                 }
  187                 n->m_next = m->m_next; 
  188                 if (mprev == NULL)
  189                         m0 = mfirst;            /* new head of chain */
  190                 else
  191                         mprev->m_next = mfirst; /* replace old mbuf */
  192                 m_free(m);                      /* release old mbuf */
  193                 mprev = mfirst;
  194         }
  195         return (m0);
  196 }
  197 
  198 /*
  199  * Make space for a new header of length hlen at skip bytes
  200  * into the packet.  When doing this we allocate new mbufs only
  201  * when absolutely necessary.  The mbuf where the new header
  202  * is to go is returned together with an offset into the mbuf.
  203  * If NULL is returned then the mbuf chain may have been modified;
  204  * the caller is assumed to always free the chain.
  205  */
  206 struct mbuf *
  207 m_makespace(struct mbuf *m0, int skip, int hlen, int *off)
  208 {
  209         struct mbuf *m;
  210         unsigned remain;
  211 
  212         KASSERT(m0 != NULL, ("m_dmakespace: null mbuf"));
  213         KASSERT(hlen < MHLEN, ("m_makespace: hlen too big: %u", hlen));
  214 
  215         for (m = m0; m && skip > m->m_len; m = m->m_next)
  216                 skip -= m->m_len;
  217         if (m == NULL)
  218                 return (NULL);
  219         /*
  220          * At this point skip is the offset into the mbuf m
  221          * where the new header should be placed.  Figure out
  222          * if there's space to insert the new header.  If so,
  223          * and copying the remainder makese sense then do so.
  224          * Otherwise insert a new mbuf in the chain, splitting
  225          * the contents of m as needed.
  226          */
  227         remain = m->m_len - skip;               /* data to move */
  228         if (hlen > M_TRAILINGSPACE(m)) {
  229                 struct mbuf *n;
  230 
  231                 /* XXX code doesn't handle clusters XXX */
  232                 KASSERT(remain < MLEN,
  233                         ("m_makespace: remainder too big: %u", remain));
  234                 /*
  235                  * Not enough space in m, split the contents
  236                  * of m, inserting new mbufs as required.
  237                  *
  238                  * NB: this ignores mbuf types.
  239                  */
  240                 MGET(n, M_DONTWAIT, MT_DATA);
  241                 if (n == NULL)
  242                         return (NULL);
  243                 n->m_next = m->m_next;          /* splice new mbuf */
  244                 m->m_next = n;
  245                 newipsecstat.ips_mbinserted++;
  246                 if (hlen <= M_TRAILINGSPACE(m) + remain) {
  247                         /*
  248                          * New header fits in the old mbuf if we copy
  249                          * the remainder; just do the copy to the new
  250                          * mbuf and we're good to go.
  251                          */
  252                         memcpy(mtod(n, caddr_t),
  253                                mtod(m, caddr_t) + skip, remain);
  254                         n->m_len = remain;
  255                         m->m_len = skip + hlen;
  256                         *off = skip;
  257                 } else {
  258                         /*
  259                          * No space in the old mbuf for the new header.
  260                          * Make space in the new mbuf and check the
  261                          * remainder'd data fits too.  If not then we
  262                          * must allocate an additional mbuf (yech).
  263                          */
  264                         n->m_len = 0;
  265                         if (remain + hlen > M_TRAILINGSPACE(n)) {
  266                                 struct mbuf *n2;
  267 
  268                                 MGET(n2, M_DONTWAIT, MT_DATA);
  269                                 /* NB: new mbuf is on chain, let caller free */
  270                                 if (n2 == NULL)
  271                                         return (NULL);
  272                                 n2->m_len = 0;
  273                                 memcpy(mtod(n2, caddr_t),
  274                                        mtod(m, caddr_t) + skip, remain);
  275                                 n2->m_len = remain;
  276                                 /* splice in second mbuf */
  277                                 n2->m_next = n->m_next;
  278                                 n->m_next = n2;
  279                                 newipsecstat.ips_mbinserted++;
  280                         } else {
  281                                 memcpy(mtod(n, caddr_t) + hlen,
  282                                        mtod(m, caddr_t) + skip, remain);
  283                                 n->m_len += remain;
  284                         }
  285                         m->m_len -= remain;
  286                         n->m_len += hlen;
  287                         m = n;                  /* header is at front ... */
  288                         *off = 0;               /* ... of new mbuf */
  289                 }
  290         } else {
  291                 /*
  292                  * Copy the remainder to the back of the mbuf
  293                  * so there's space to write the new header.
  294                  */
  295                 /* XXX can this be memcpy? does it handle overlap? */
  296                 ovbcopy(mtod(m, caddr_t) + skip,
  297                         mtod(m, caddr_t) + skip + hlen, remain);
  298                 m->m_len += hlen;
  299                 *off = skip;
  300         }
  301         m0->m_pkthdr.len += hlen;               /* adjust packet length */
  302         return m;
  303 }
  304 
  305 /*
  306  * m_pad(m, n) pads <m> with <n> bytes at the end. The packet header
  307  * length is updated, and a pointer to the first byte of the padding
  308  * (which is guaranteed to be all in one mbuf) is returned.
  309  */
  310 caddr_t
  311 m_pad(struct mbuf *m, int n)
  312 {
  313         register struct mbuf *m0, *m1;
  314         register int len, pad;
  315         caddr_t retval;
  316 
  317         if (n <= 0) {  /* No stupid arguments. */
  318                 DPRINTF(("m_pad: pad length invalid (%d)\n", n));
  319                 m_freem(m);
  320                 return NULL;
  321         }
  322 
  323         len = m->m_pkthdr.len;
  324         pad = n;
  325         m0 = m;
  326 
  327         while (m0->m_len < len) {
  328 KASSERT(m0->m_next != NULL, ("m_pad: m0 null, len %u m_len %u", len, m0->m_len));/*XXX*/
  329                 len -= m0->m_len;
  330                 m0 = m0->m_next;
  331         }
  332 
  333         if (m0->m_len != len) {
  334                 DPRINTF(("m_pad: length mismatch (should be %d instead of %d)\n",
  335                     m->m_pkthdr.len, m->m_pkthdr.len + m0->m_len - len));
  336 
  337                 m_freem(m);
  338                 return NULL;
  339         }
  340 
  341         /* Check for zero-length trailing mbufs, and find the last one. */
  342         for (m1 = m0; m1->m_next; m1 = m1->m_next) {
  343                 if (m1->m_next->m_len != 0) {
  344                         DPRINTF(("m_pad: length mismatch (should be %d "
  345                             "instead of %d)\n",
  346                             m->m_pkthdr.len,
  347                             m->m_pkthdr.len + m1->m_next->m_len));
  348 
  349                         m_freem(m);
  350                         return NULL;
  351                 }
  352 
  353                 m0 = m1->m_next;
  354         }
  355 
  356         if (pad > M_TRAILINGSPACE(m0)) {
  357                 /* Add an mbuf to the chain. */
  358                 MGET(m1, M_DONTWAIT, MT_DATA);
  359                 if (m1 == 0) {
  360                         m_freem(m0);
  361                         DPRINTF(("m_pad: unable to get extra mbuf\n"));
  362                         return NULL;
  363                 }
  364 
  365                 m0->m_next = m1;
  366                 m0 = m1;
  367                 m0->m_len = 0;
  368         }
  369 
  370         retval = m0->m_data + m0->m_len;
  371         m0->m_len += pad;
  372         m->m_pkthdr.len += pad;
  373 
  374         return retval;
  375 }
  376 
  377 /*
  378  * Remove hlen data at offset skip in the packet.  This is used by
  379  * the protocols strip protocol headers and associated data (e.g. IV,
  380  * authenticator) on input.
  381  */
  382 int
  383 m_striphdr(struct mbuf *m, int skip, int hlen)
  384 {
  385         struct mbuf *m1;
  386         int roff;
  387 
  388         /* Find beginning of header */
  389         m1 = m_getptr(m, skip, &roff);
  390         if (m1 == NULL)
  391                 return (EINVAL);
  392 
  393         /* Remove the header and associated data from the mbuf. */
  394         if (roff == 0) {
  395                 /* The header was at the beginning of the mbuf */
  396                 newipsecstat.ips_input_front++;
  397                 m_adj(m1, hlen);
  398                 if ((m1->m_flags & M_PKTHDR) == 0)
  399                         m->m_pkthdr.len -= hlen;
  400         } else if (roff + hlen >= m1->m_len) {
  401                 struct mbuf *mo;
  402 
  403                 /*
  404                  * Part or all of the header is at the end of this mbuf,
  405                  * so first let's remove the remainder of the header from
  406                  * the beginning of the remainder of the mbuf chain, if any.
  407                  */
  408                 newipsecstat.ips_input_end++;
  409                 if (roff + hlen > m1->m_len) {
  410                         /* Adjust the next mbuf by the remainder */
  411                         m_adj(m1->m_next, roff + hlen - m1->m_len);
  412 
  413                         /* The second mbuf is guaranteed not to have a pkthdr... */
  414                         m->m_pkthdr.len -= (roff + hlen - m1->m_len);
  415                 }
  416 
  417                 /* Now, let's unlink the mbuf chain for a second...*/
  418                 mo = m1->m_next;
  419                 m1->m_next = NULL;
  420 
  421                 /* ...and trim the end of the first part of the chain...sick */
  422                 m_adj(m1, -(m1->m_len - roff));
  423                 if ((m1->m_flags & M_PKTHDR) == 0)
  424                         m->m_pkthdr.len -= (m1->m_len - roff);
  425 
  426                 /* Finally, let's relink */
  427                 m1->m_next = mo;
  428         } else {
  429                 /*
  430                  * The header lies in the "middle" of the mbuf; copy
  431                  * the remainder of the mbuf down over the header.
  432                  */
  433                 newipsecstat.ips_input_middle++;
  434                 bcopy(mtod(m1, u_char *) + roff + hlen,
  435                       mtod(m1, u_char *) + roff,
  436                       m1->m_len - (roff + hlen));
  437                 m1->m_len -= hlen;
  438                 m->m_pkthdr.len -= hlen;
  439         }
  440         return (0);
  441 }
  442 
  443 /*
  444  * Diagnostic routine to check mbuf alignment as required by the
  445  * crypto device drivers (that use DMA).
  446  */
  447 void
  448 m_checkalignment(const char* where, struct mbuf *m0, int off, int len)
  449 {
  450         int roff;
  451         struct mbuf *m = m_getptr(m0, off, &roff);
  452         caddr_t addr;
  453 
  454         if (m == NULL)
  455                 return;
  456         printf("%s (off %u len %u): ", where, off, len);
  457         addr = mtod(m, caddr_t) + roff;
  458         do {
  459                 int mlen;
  460 
  461                 if (((uintptr_t) addr) & 3) {
  462                         printf("addr misaligned %p,", addr);
  463                         break;
  464                 }
  465                 mlen = m->m_len;
  466                 if (mlen > len)
  467                         mlen = len;
  468                 len -= mlen;
  469                 if (len && (mlen & 3)) {
  470                         printf("len mismatch %u,", mlen);
  471                         break;
  472                 }
  473                 m = m->m_next;
  474                 addr = m ? mtod(m, caddr_t) : NULL;
  475         } while (m && len > 0);
  476         for (m = m0; m; m = m->m_next)
  477                 printf(" [%p:%u]", mtod(m, caddr_t), m->m_len);
  478         printf("\n");
  479 }

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