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

     /*-
      * Copyright (c) 2001-2007, by Cisco Systems, Inc. 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.
     */
    
    /* $KAME: sctp_crc32.c,v 1.12 2005/03/06 16:04:17 itojun Exp $   */
    
    
    #include <sys/cdefs.h>
    __FBSDID("$FreeBSD: releng/8.0/sys/netinet/sctp_crc32.c 191891 2009-05-07 16:43:49Z rrs $");
    
    #include <netinet/sctp_os.h>
    #include <netinet/sctp.h>
    #include <netinet/sctp_crc32.h>
    #include <netinet/sctp_pcb.h>
    
    
    #if !defined(SCTP_WITH_NO_CSUM)
    
    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.. aka Motorola byte order the result is in
             * little-endian form. So we must manually swap the bytes. Then we
             * can call htonl() which does nothing...
             */
            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 INTEL platforms the result comes out in network order. No
             * htonl is required or the swap above. So we optimize out both the
             * htonl and the manual swap above.
             */
            crc32c = result;
    #endif
            return (crc32c);
    }
    
    uint32_t
    sctp_calculate_cksum(struct mbuf *m, uint32_t offset)
    {
            /*
             * given a mbuf chain with a packetheader offset by 'offset'
             * pointing at a sctphdr (with csum set to 0) go through the chain
             * of SCTP_BUF_NEXT()'s and calculate the SCTP checksum. This also
             * has a side bonus as it will calculate the total length of the
             * mbuf chain. Note: if offset is greater than the total mbuf
             * length, checksum=1, pktlen=0 is returned (ie. no real error code)
             */
            uint32_t base = 0xffffffff;
            struct mbuf *at;
    
            at = m;
            /* find the correct mbuf and offset into mbuf */
            while ((at != NULL) && (offset > (uint32_t) SCTP_BUF_LEN(at))) {
                    offset -= SCTP_BUF_LEN(at);     /* update remaining offset
                                                     * left */
                    at = SCTP_BUF_NEXT(at);
            }
            while (at != NULL) {
                   if ((SCTP_BUF_LEN(at) - offset) > 0) {
                           base = calculate_crc32c(base,
                               (unsigned char *)(SCTP_BUF_AT(at, offset)),
                               (unsigned int)(SCTP_BUF_LEN(at) - offset));
                   }
                   if (offset) {
                           /* we only offset once into the first mbuf */
                           if (offset < (uint32_t) SCTP_BUF_LEN(at))
                                   offset = 0;
                           else
                                   offset -= SCTP_BUF_LEN(at);
                   }
                   at = SCTP_BUF_NEXT(at);
           }
           base = sctp_finalize_crc32c(base);
           return (base);
   }
   
   #else
   
   uint32_t
   sctp_calculate_cksum(struct mbuf *m, uint32_t offset)
   {
           return (0);
   }
   
   #endif                          /* !defined(SCTP_WITH_NO_CSUM) */
   
   
   void
   sctp_delayed_cksum(struct mbuf *m)
   {
           struct ip *ip;
           uint32_t checksum;
           uint32_t offset;
   
           ip = mtod(m, struct ip *);
           offset = ip->ip_hl << 2;
           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)) {
                   printf("delayed m_pullup, m->len: %d  off: %d  p: %d\n",
                       (uint32_t) m->m_len, offset, ip->ip_p);
                   /*
                    * XXX this shouldn't happen, but if it does, the correct
                    * behavior may be to insert the checksum in the appropriate
                    * next mbuf in the chain.
                    */
                   return;
           }
           *(uint32_t *) (m->m_data + offset) = checksum;
   }

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