include/net/sctp/checksum.h

   1 /* SCTP kernel reference Implementation
   2  * Copyright (c) 1999-2001 Motorola, Inc.
   3  * Copyright (c) 2001-2003 International Business Machines, Corp.
   4  *
   5  * This file is part of the SCTP kernel reference Implementation
   6  *
   7  * SCTP Checksum functions
   8  *
   9  * The SCTP reference implementation is free software;
  10  * you can redistribute it and/or modify it under the terms of
  11  * the GNU General Public License as published by
  12  * the Free Software Foundation; either version 2, or (at your option)
  13  * any later version.
  14  *
  15  * The SCTP reference implementation is distributed in the hope that it
  16  * will be useful, but WITHOUT ANY WARRANTY; without even the implied
  17  *                 ************************
  18  * warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
  19  * See the GNU General Public License for more details.
  20  *
  21  * You should have received a copy of the GNU General Public License
  22  * along with GNU CC; see the file COPYING.  If not, write to
  23  * the Free Software Foundation, 59 Temple Place - Suite 330,
  24  * Boston, MA 02111-1307, USA.
  25  *
  26  * Please send any bug reports or fixes you make to the
  27  * email address(es):
  28  *    lksctp developers <linux-sctp@vger.kernel.org>
  29  *
  30  * Written or modified by:
  31  *    Dinakaran Joseph
  32  *    Jon Grimm <jgrimm@us.ibm.com>
  33  *    Sridhar Samudrala <sri@us.ibm.com>
  34  *
  35  * Rewritten to use libcrc32c by:
  36  *    Vlad Yasevich <vladislav.yasevich@hp.com>
  37  */
  38
  39 #ifndef __sctp_checksum_h__
  40 #define __sctp_checksum_h__
  41
  42 #include <linux/types.h>
  43 #include <net/sctp/sctp.h>
  44 #include <linux/crc32c.h>
  45
  46 static inline __u32 sctp_crc32c(__u32 crc, u8 *buffer, u16 length)
  47 {
  48         return crc32c(crc, buffer, length);
  49 }
  50
  51 static inline __u32 sctp_start_cksum(__u8 *buffer, __u16 length)
  52 {
  53         __u32 crc = ~(__u32)0;
  54         __u8  zero[sizeof(__u32)] = {0};
  55
  56         /* Optimize this routine to be SCTP specific, knowing how
  57          * to skip the checksum field of the SCTP header.
  58          */
  59
  60         /* Calculate CRC up to the checksum. */
  61         crc = sctp_crc32c(crc, buffer, sizeof(struct sctphdr) - sizeof(__u32));
  62
  63         /* Skip checksum field of the header. */
  64         crc = sctp_crc32c(crc, zero, sizeof(__u32));
  65
  66         /* Calculate the rest of the CRC. */
  67         crc = sctp_crc32c(crc, &buffer[sizeof(struct sctphdr)],
  68                             length - sizeof(struct sctphdr));
  69         return crc;
  70 }
  71
  72 static inline __u32 sctp_update_cksum(__u8 *buffer, __u16 length, __u32 crc32)
  73 {
  74         return sctp_crc32c(crc32, buffer, length);
  75 }
  76
  77 static inline __le32 sctp_end_cksum(__u32 crc32)
  78 {
  79         return cpu_to_le32(~crc32);
  80 }
  81
  82 /* Calculate the CRC32C checksum of an SCTP packet.  */
  83 static inline __le32 sctp_compute_cksum(const struct sk_buff *skb,
  84                                         unsigned int offset)
  85 {
  86         const struct sk_buff *iter;
  87
  88         __u32 crc32 = sctp_start_cksum(skb->data + offset,
  89                                        skb_headlen(skb) - offset);
  90         skb_walk_frags(skb, iter)
  91                 crc32 = sctp_update_cksum((__u8 *) iter->data,
  92                                           skb_headlen(iter), crc32);
  93
  94         return sctp_end_cksum(crc32);
  95 }
  96
  97 #endif /* __sctp_checksum_h__ */