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  * Copyright (c) 2008-2012, by Randall Stewart. All rights reserved.
    4  * Copyright (c) 2008-2012, by Michael Tuexen. All rights reserved.
    5  *
    6  * Redistribution and use in source and binary forms, with or without
    7  * modification, are permitted provided that the following conditions are met:
    8  *
    9  * a) Redistributions of source code must retain the above copyright notice,
   10  *   this list of conditions and the following disclaimer.
   11  *
   12  * b) Redistributions in binary form must reproduce the above copyright
   13  *    notice, this list of conditions and the following disclaimer in
   14  *   the documentation and/or other materials provided with the distribution.
   15  *
   16  * c) Neither the name of Cisco Systems, Inc. nor the names of its
   17  *    contributors may be used to endorse or promote products derived
   18  *    from this software without specific prior written permission.
   19  *
   20  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   21  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
   22  * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   23  * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
   24  * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
   25  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
   26  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
   27  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
   28  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
   29  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
   30  * THE POSSIBILITY OF SUCH DAMAGE.
   31  */
   32 
   33 #include <sys/cdefs.h>
   34 __FBSDID("$FreeBSD: releng/10.3/sys/netinet/sctp_crc32.c 235828 2012-05-23 11:26:28Z tuexen $");
   35 
   36 #include <netinet/sctp_os.h>
   37 #include <netinet/sctp.h>
   38 #include <netinet/sctp_crc32.h>
   39 #include <netinet/sctp_pcb.h>
   40 
   41 
   42 #if !defined(SCTP_WITH_NO_CSUM)
   43 
   44 static uint32_t
   45 sctp_finalize_crc32c(uint32_t crc32c)
   46 {
   47         uint32_t result;
   48 
   49 #if BYTE_ORDER == BIG_ENDIAN
   50         uint8_t byte0, byte1, byte2, byte3;
   51 
   52 #endif
   53         /* Complement the result */
   54         result = ~crc32c;
   55 #if BYTE_ORDER == BIG_ENDIAN
   56         /*
   57          * For BIG-ENDIAN.. aka Motorola byte order the result is in
   58          * little-endian form. So we must manually swap the bytes. Then we
   59          * can call htonl() which does nothing...
   60          */
   61         byte0 = result & 0x000000ff;
   62         byte1 = (result >> 8) & 0x000000ff;
   63         byte2 = (result >> 16) & 0x000000ff;
   64         byte3 = (result >> 24) & 0x000000ff;
   65         crc32c = ((byte0 << 24) | (byte1 << 16) | (byte2 << 8) | byte3);
   66 #else
   67         /*
   68          * For INTEL platforms the result comes out in network order. No
   69          * htonl is required or the swap above. So we optimize out both the
   70          * htonl and the manual swap above.
   71          */
   72         crc32c = result;
   73 #endif
   74         return (crc32c);
   75 }
   76 
   77 uint32_t
   78 sctp_calculate_cksum(struct mbuf *m, uint32_t offset)
   79 {
   80         /*
   81          * given a mbuf chain with a packetheader offset by 'offset'
   82          * pointing at a sctphdr (with csum set to 0) go through the chain
   83          * of SCTP_BUF_NEXT()'s and calculate the SCTP checksum. This also
   84          * has a side bonus as it will calculate the total length of the
   85          * mbuf chain. Note: if offset is greater than the total mbuf
   86          * length, checksum=1, pktlen=0 is returned (ie. no real error code)
   87          */
   88         uint32_t base = 0xffffffff;
   89         struct mbuf *at;
   90 
   91         at = m;
   92         /* find the correct mbuf and offset into mbuf */
   93         while ((at != NULL) && (offset > (uint32_t) SCTP_BUF_LEN(at))) {
   94                 offset -= SCTP_BUF_LEN(at);     /* update remaining offset
   95                                                  * left */
   96                 at = SCTP_BUF_NEXT(at);
   97         }
   98         while (at != NULL) {
   99                 if ((SCTP_BUF_LEN(at) - offset) > 0) {
  100                         base = calculate_crc32c(base,
  101                             (unsigned char *)(SCTP_BUF_AT(at, offset)),
  102                             (unsigned int)(SCTP_BUF_LEN(at) - offset));
  103                 }
  104                 if (offset) {
  105                         /* we only offset once into the first mbuf */
  106                         if (offset < (uint32_t) SCTP_BUF_LEN(at))
  107                                 offset = 0;
  108                         else
  109                                 offset -= SCTP_BUF_LEN(at);
  110                 }
  111                 at = SCTP_BUF_NEXT(at);
  112         }
  113         base = sctp_finalize_crc32c(base);
  114         return (base);
  115 }
  116 
  117 #endif                          /* !defined(SCTP_WITH_NO_CSUM) */
  118 
  119 
  120 void
  121 sctp_delayed_cksum(struct mbuf *m, uint32_t offset)
  122 {
  123 #if defined(SCTP_WITH_NO_CSUM)
  124 #ifdef INVARIANTS
  125         panic("sctp_delayed_cksum() called when using no SCTP CRC.");
  126 #endif
  127 #else
  128         uint32_t checksum;
  129 
  130         checksum = sctp_calculate_cksum(m, offset);
  131         SCTP_STAT_DECR(sctps_sendhwcrc);
  132         SCTP_STAT_INCR(sctps_sendswcrc);
  133         offset += offsetof(struct sctphdr, checksum);
  134 
  135         if (offset + sizeof(uint32_t) > (uint32_t) (m->m_len)) {
  136                 SCTP_PRINTF("sctp_delayed_cksum(): m->len: %d,  off: %d.\n",
  137                     (uint32_t) m->m_len, offset);
  138                 /*
  139                  * XXX this shouldn't happen, but if it does, the correct
  140                  * behavior may be to insert the checksum in the appropriate
  141                  * next mbuf in the chain.
  142                  */
  143                 return;
  144         }
  145         *(uint32_t *) (m->m_data + offset) = checksum;
  146 #endif
  147 }

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