FreeBSD/Linux Kernel Cross Reference
sys/netinet/sctp_crc32.c

     /*-
      * Copyright (c) 2001-2007, by Cisco Systems, Inc. All rights reserved.
      * Copyright (c) 2008-2012, by Randall Stewart. All rights reserved.
      * Copyright (c) 2008-2012, by Michael Tuexen. All rights reserved.
      *
      * Redistribution and use in source and binary forms, with or without
      * modification, are permitted provided that the following conditions are met:
      *
      * a) Redistributions of source code must retain the above copyright notice,
     *   this list of conditions and the following disclaimer.
     *
     * b) Redistributions in binary form must reproduce the above copyright
     *    notice, this list of conditions and the following disclaimer in
     *   the documentation and/or other materials provided with the distribution.
     *
     * c) Neither the name of Cisco Systems, Inc. nor the names of its
     *    contributors may be used to endorse or promote products derived
     *    from this software without specific prior written permission.
     *
     * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
     * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
     * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
     * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
     * THE POSSIBILITY OF SUCH DAMAGE.
     */
    
    #include <sys/cdefs.h>
    __FBSDID("$FreeBSD: releng/11.2/sys/netinet/sctp_crc32.c 332229 2018-04-07 20:27:11Z tuexen $");
    
    #include "opt_sctp.h"
    
    #ifdef SCTP
    #include <netinet/sctp_os.h>
    #include <netinet/sctp.h>
    #include <netinet/sctp_crc32.h>
    #include <netinet/sctp_pcb.h>
    #else
    #include <sys/param.h>
    #include <sys/systm.h>
    #include <sys/mbuf.h>
    
    #include <netinet/sctp_crc32.h>
    #endif
    
    static uint32_t
    sctp_finalize_crc32c(uint32_t crc32c)
    {
            uint32_t result;
    #if BYTE_ORDER == BIG_ENDIAN
            uint8_t byte0, byte1, byte2, byte3;
    #endif
    
            /* Complement the result */
            result = ~crc32c;
    #if BYTE_ORDER == BIG_ENDIAN
            /*
             * For BIG-ENDIAN platforms the result is in little-endian form. So
             * we must swap the bytes to return the result in network byte
             * order.
             */
            byte0 = result & 0x000000ff;
            byte1 = (result >> 8) & 0x000000ff;
            byte2 = (result >> 16) & 0x000000ff;
            byte3 = (result >> 24) & 0x000000ff;
            crc32c = ((byte0 << 24) | (byte1 << 16) | (byte2 << 8) | byte3);
    #else
            /*
             * For LITTLE ENDIAN platforms the result is in already in network
             * byte order.
             */
            crc32c = result;
    #endif
            return (crc32c);
    }
    
    /*
     * Compute the SCTP checksum in network byte order for a given mbuf chain m
     * which contains an SCTP packet starting at offset.
     * Since this function is also called by ipfw, don't assume that
     * it is compiled on a kernel with SCTP support.
     */
    uint32_t
    sctp_calculate_cksum(struct mbuf *m, uint32_t offset)
    {
            uint32_t base = 0xffffffff;
    
            while (offset > 0) {
                    KASSERT(m != NULL, ("sctp_calculate_cksum, offset > length of mbuf chain"));
                    if (offset < (uint32_t)m->m_len) {
                            break;
                    }
                    offset -= m->m_len;
                    m = m->m_next;
           }
           if (offset > 0) {
                   base = calculate_crc32c(base,
                       (unsigned char *)(m->m_data + offset),
                       (unsigned int)(m->m_len - offset));
                   m = m->m_next;
           }
           while (m != NULL) {
                   base = calculate_crc32c(base,
                       (unsigned char *)m->m_data,
                       (unsigned int)m->m_len);
                   m = m->m_next;
           }
           base = sctp_finalize_crc32c(base);
           return (base);
   }
   
   #ifdef SCTP
   /*
    * Compute and insert the SCTP checksum in network byte order for a given
    * mbuf chain m which contains an SCTP packet starting at offset.
    */
   void
   sctp_delayed_cksum(struct mbuf *m, uint32_t offset)
   {
           uint32_t checksum;
   
           checksum = sctp_calculate_cksum(m, offset);
           SCTP_STAT_DECR(sctps_sendhwcrc);
           SCTP_STAT_INCR(sctps_sendswcrc);
           offset += offsetof(struct sctphdr, checksum);
   
           if (offset + sizeof(uint32_t) > (uint32_t)(m->m_len)) {
   #ifdef INVARIANTS
                   panic("sctp_delayed_cksum(): m->m_len: %d, offset: %u.",
                       m->m_len, offset);
   #else
                   SCTP_PRINTF("sctp_delayed_cksum(): m->m_len: %d, offset: %u.\n",
                       m->m_len, offset);
   #endif
                   return;
           }
           *(uint32_t *)(m->m_data + offset) = checksum;
   }
   #endif

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