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1// SPDX-License-Identifier: GPL-2.0-or-later2/*3 *4 * INET An implementation of the TCP/IP protocol suite for the LINUX5 * operating system. INET is implemented using the BSD Socket6 * interface as the means of communication with the user level.7 *8 * IP/TCP/UDP checksumming routines9 *10 * Authors: Jorge Cwik, <jorge@laser.satlink.net>11 * Arnt Gulbrandsen, <agulbra@nvg.unit.no>12 * Tom May, <ftom@netcom.com>13 * Andreas Schwab, <schwab@issan.informatik.uni-dortmund.de>14 * Lots of code moved from tcp.c and ip.c; see those files15 * for more names.16 *17 * 03/02/96 Jes Sorensen, Andreas Schwab, Roman Hodek:18 * Fixed some nasty bugs, causing some horrible crashes.19 * A: At some points, the sum (%0) was used as20 * length-counter instead of the length counter21 * (%1). Thanks to Roman Hodek for pointing this out.22 * B: GCC seems to mess up if one uses too many23 * data-registers to hold input values and one tries to24 * specify d0 and d1 as scratch registers. Letting gcc25 * choose these registers itself solves the problem.26 */27 28/* Revised by Kenneth Albanowski for m68knommu. Basic problem: unaligned access29 kills, so most of the assembly has to go. */30 31#include <linux/export.h>32#include <net/checksum.h>33 34#include <asm/byteorder.h>35 36#ifndef do_csum37static inline unsigned short from32to16(unsigned int x)38{39 /* add up 16-bit and 16-bit for 16+c bit */40 x = (x & 0xffff) + (x >> 16);41 /* add up carry.. */42 x = (x & 0xffff) + (x >> 16);43 return x;44}45 46static unsigned int do_csum(const unsigned char *buff, int len)47{48 int odd;49 unsigned int result = 0;50 51 if (len <= 0)52 goto out;53 odd = 1 & (unsigned long) buff;54 if (odd) {55#ifdef __LITTLE_ENDIAN56 result += (*buff << 8);57#else58 result = *buff;59#endif60 len--;61 buff++;62 }63 if (len >= 2) {64 if (2 & (unsigned long) buff) {65 result += *(unsigned short *) buff;66 len -= 2;67 buff += 2;68 }69 if (len >= 4) {70 const unsigned char *end = buff + ((unsigned)len & ~3);71 unsigned int carry = 0;72 do {73 unsigned int w = *(unsigned int *) buff;74 buff += 4;75 result += carry;76 result += w;77 carry = (w > result);78 } while (buff < end);79 result += carry;80 result = (result & 0xffff) + (result >> 16);81 }82 if (len & 2) {83 result += *(unsigned short *) buff;84 buff += 2;85 }86 }87 if (len & 1)88#ifdef __LITTLE_ENDIAN89 result += *buff;90#else91 result += (*buff << 8);92#endif93 result = from32to16(result);94 if (odd)95 result = ((result >> 8) & 0xff) | ((result & 0xff) << 8);96out:97 return result;98}99#endif100 101#ifndef ip_fast_csum102/*103 * This is a version of ip_compute_csum() optimized for IP headers,104 * which always checksum on 4 octet boundaries.105 */106__sum16 ip_fast_csum(const void *iph, unsigned int ihl)107{108 return (__force __sum16)~do_csum(iph, ihl*4);109}110EXPORT_SYMBOL(ip_fast_csum);111#endif112 113/*114 * computes the checksum of a memory block at buff, length len,115 * and adds in "sum" (32-bit)116 *117 * returns a 32-bit number suitable for feeding into itself118 * or csum_tcpudp_magic119 *120 * this function must be called with even lengths, except121 * for the last fragment, which may be odd122 *123 * it's best to have buff aligned on a 32-bit boundary124 */125__wsum csum_partial(const void *buff, int len, __wsum wsum)126{127 unsigned int sum = (__force unsigned int)wsum;128 unsigned int result = do_csum(buff, len);129 130 /* add in old sum, and carry.. */131 result += sum;132 if (sum > result)133 result += 1;134 return (__force __wsum)result;135}136EXPORT_SYMBOL(csum_partial);137 138/*139 * this routine is used for miscellaneous IP-like checksums, mainly140 * in icmp.c141 */142__sum16 ip_compute_csum(const void *buff, int len)143{144 return (__force __sum16)~do_csum(buff, len);145}146EXPORT_SYMBOL(ip_compute_csum);147 148#ifndef csum_tcpudp_nofold149static inline u32 from64to32(u64 x)150{151 /* add up 32-bit and 32-bit for 32+c bit */152 x = (x & 0xffffffff) + (x >> 32);153 /* add up carry.. */154 x = (x & 0xffffffff) + (x >> 32);155 return (u32)x;156}157 158__wsum csum_tcpudp_nofold(__be32 saddr, __be32 daddr,159 __u32 len, __u8 proto, __wsum sum)160{161 unsigned long long s = (__force u32)sum;162 163 s += (__force u32)saddr;164 s += (__force u32)daddr;165#ifdef __BIG_ENDIAN166 s += proto + len;167#else168 s += (proto + len) << 8;169#endif170 return (__force __wsum)from64to32(s);171}172EXPORT_SYMBOL(csum_tcpudp_nofold);173#endif174