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__ */ 98