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/netinet/sctp_crc32.c

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    1 /*-
    2  * Copyright (c) 2001-2007, by Cisco Systems, Inc. All rights reserved.
    3  *
    4  * Redistribution and use in source and binary forms, with or without
    5  * modification, are permitted provided that the following conditions are met:
    6  *
    7  * a) Redistributions of source code must retain the above copyright notice,
    8  *   this list of conditions and the following disclaimer.
    9  *
   10  * b) Redistributions in binary form must reproduce the above copyright
   11  *    notice, this list of conditions and the following disclaimer in
   12  *   the documentation and/or other materials provided with the distribution.
   13  *
   14  * c) Neither the name of Cisco Systems, Inc. nor the names of its
   15  *    contributors may be used to endorse or promote products derived
   16  *    from this software without specific prior written permission.
   17  *
   18  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   19  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
   20  * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   21  * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
   22  * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
   23  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
   24  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
   25  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
   26  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
   27  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
   28  * THE POSSIBILITY OF SUCH DAMAGE.
   29  */
   30 
   31 /* $KAME: sctp_crc32.c,v 1.12 2005/03/06 16:04:17 itojun Exp $   */
   32 
   33 
   34 #include <sys/cdefs.h>
   35 __FBSDID("$FreeBSD: releng/8.2/sys/netinet/sctp_crc32.c 215594 2010-11-20 21:39:08Z tuexen $");
   36 
   37 #include <netinet/sctp_os.h>
   38 #include <netinet/sctp.h>
   39 #include <netinet/sctp_crc32.h>
   40 #include <netinet/sctp_pcb.h>
   41 
   42 
   43 #if !defined(SCTP_WITH_NO_CSUM)
   44 
   45 static uint32_t
   46 sctp_finalize_crc32c(uint32_t crc32c)
   47 {
   48         uint32_t result;
   49 
   50 #if BYTE_ORDER == BIG_ENDIAN
   51         uint8_t byte0, byte1, byte2, byte3;
   52 
   53 #endif
   54         /* Complement the result */
   55         result = ~crc32c;
   56 #if BYTE_ORDER == BIG_ENDIAN
   57         /*
   58          * For BIG-ENDIAN.. aka Motorola byte order the result is in
   59          * little-endian form. So we must manually swap the bytes. Then we
   60          * can call htonl() which does nothing...
   61          */
   62         byte0 = result & 0x000000ff;
   63         byte1 = (result >> 8) & 0x000000ff;
   64         byte2 = (result >> 16) & 0x000000ff;
   65         byte3 = (result >> 24) & 0x000000ff;
   66         crc32c = ((byte0 << 24) | (byte1 << 16) | (byte2 << 8) | byte3);
   67 #else
   68         /*
   69          * For INTEL platforms the result comes out in network order. No
   70          * htonl is required or the swap above. So we optimize out both the
   71          * htonl and the manual swap above.
   72          */
   73         crc32c = result;
   74 #endif
   75         return (crc32c);
   76 }
   77 
   78 uint32_t
   79 sctp_calculate_cksum(struct mbuf *m, uint32_t offset)
   80 {
   81         /*
   82          * given a mbuf chain with a packetheader offset by 'offset'
   83          * pointing at a sctphdr (with csum set to 0) go through the chain
   84          * of SCTP_BUF_NEXT()'s and calculate the SCTP checksum. This also
   85          * has a side bonus as it will calculate the total length of the
   86          * mbuf chain. Note: if offset is greater than the total mbuf
   87          * length, checksum=1, pktlen=0 is returned (ie. no real error code)
   88          */
   89         uint32_t base = 0xffffffff;
   90         struct mbuf *at;
   91 
   92         at = m;
   93         /* find the correct mbuf and offset into mbuf */
   94         while ((at != NULL) && (offset > (uint32_t) SCTP_BUF_LEN(at))) {
   95                 offset -= SCTP_BUF_LEN(at);     /* update remaining offset
   96                                                  * left */
   97                 at = SCTP_BUF_NEXT(at);
   98         }
   99         while (at != NULL) {
  100                 if ((SCTP_BUF_LEN(at) - offset) > 0) {
  101                         base = calculate_crc32c(base,
  102                             (unsigned char *)(SCTP_BUF_AT(at, offset)),
  103                             (unsigned int)(SCTP_BUF_LEN(at) - offset));
  104                 }
  105                 if (offset) {
  106                         /* we only offset once into the first mbuf */
  107                         if (offset < (uint32_t) SCTP_BUF_LEN(at))
  108                                 offset = 0;
  109                         else
  110                                 offset -= SCTP_BUF_LEN(at);
  111                 }
  112                 at = SCTP_BUF_NEXT(at);
  113         }
  114         base = sctp_finalize_crc32c(base);
  115         return (base);
  116 }
  117 
  118 #endif                          /* !defined(SCTP_WITH_NO_CSUM) */
  119 
  120 
  121 void
  122 sctp_delayed_cksum(struct mbuf *m, uint32_t offset)
  123 {
  124 #if defined(SCTP_WITH_NO_CSUM)
  125         panic("sctp_delayed_cksum() called when using no SCTP CRC.");
  126 #else
  127         uint32_t checksum;
  128 
  129         checksum = sctp_calculate_cksum(m, offset);
  130         SCTP_STAT_DECR(sctps_sendhwcrc);
  131         SCTP_STAT_INCR(sctps_sendswcrc);
  132         offset += offsetof(struct sctphdr, checksum);
  133 
  134         if (offset + sizeof(uint32_t) > (uint32_t) (m->m_len)) {
  135                 printf("sctp_delayed_cksum(): m->len: %d,  off: %d.\n",
  136                     (uint32_t) m->m_len, offset);
  137                 /*
  138                  * XXX this shouldn't happen, but if it does, the correct
  139                  * behavior may be to insert the checksum in the appropriate
  140                  * next mbuf in the chain.
  141                  */
  142                 return;
  143         }
  144         *(uint32_t *) (m->m_data + offset) = checksum;
  145 #endif
  146 }

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