1 /* 2 * 3 * INET An implementation of the TCP/IP protocol suite for the LINUX 4 * operating system. INET is implemented using the BSD Socket 5 * interface as the means of communication with the user level. 6 * 7 * IP/TCP/UDP checksumming routines 8 * 9 * Authors: Jorge Cwik, <jorge@laser.satlink.net> 10 * Arnt Gulbrandsen, <agulbra@nvg.unit.no> 11 * Tom May, <ftom@netcom.com> 12 * Andreas Schwab, <schwab@issan.informatik.uni-dortmund.de> 13 * Lots of code moved from tcp.c and ip.c; see those files 14 * for more names. 15 * 16 * 03/02/96 Jes Sorensen, Andreas Schwab, Roman Hodek: 17 * Fixed some nasty bugs, causing some horrible crashes. 18 * A: At some points, the sum (%0) was used as 19 * length-counter instead of the length counter 20 * (%1). Thanks to Roman Hodek for pointing this out. 21 * B: GCC seems to mess up if one uses too many 22 * data-registers to hold input values and one tries to 23 * specify d0 and d1 as scratch registers. Letting gcc 24 * choose these registers itself solves the problem. 25 * 26 * This program is free software; you can redistribute it and/or 27 * modify it under the terms of the GNU General Public License 28 * as published by the Free Software Foundation; either version 29 * 2 of the License, or (at your option) any later version. 30 */ 31 32 /* Revised by Kenneth Albanowski for m68knommu. Basic problem: unaligned access 33 kills, so most of the assembly has to go. */ 34 35 #include <linux/export.h> 36 #include <net/checksum.h> 37 38 #include <asm/byteorder.h> 39 40 #ifndef do_csum 41 static inline unsigned short from32to16(unsigned int x) 42 { 43 /* add up 16-bit and 16-bit for 16+c bit */ 44 x = (x & 0xffff) + (x >> 16); 45 /* add up carry.. */ 46 x = (x & 0xffff) + (x >> 16); 47 return x; 48 } 49 50 static unsigned int do_csum(const unsigned char *buff, int len) 51 { 52 int odd; 53 unsigned int result = 0; 54 55 if (len <= 0) 56 goto out; 57 odd = 1 & (unsigned long) buff; 58 if (odd) { 59 #ifdef __LITTLE_ENDIAN 60 result += (*buff << 8); 61 #else 62 result = *buff; 63 #endif 64 len--; 65 buff++; 66 } 67 if (len >= 2) { 68 if (2 & (unsigned long) buff) { 69 result += *(unsigned short *) buff; 70 len -= 2; 71 buff += 2; 72 } 73 if (len >= 4) { 74 const unsigned char *end = buff + ((unsigned)len & ~3); 75 unsigned int carry = 0; 76 do { 77 unsigned int w = *(unsigned int *) buff; 78 buff += 4; 79 result += carry; 80 result += w; 81 carry = (w > result); 82 } while (buff < end); 83 result += carry; 84 result = (result & 0xffff) + (result >> 16); 85 } 86 if (len & 2) { 87 result += *(unsigned short *) buff; 88 buff += 2; 89 } 90 } 91 if (len & 1) 92 #ifdef __LITTLE_ENDIAN 93 result += *buff; 94 #else 95 result += (*buff << 8); 96 #endif 97 result = from32to16(result); 98 if (odd) 99 result = ((result >> 8) & 0xff) | ((result & 0xff) << 8); 100 out: 101 return result; 102 } 103 #endif 104 105 /* 106 * This is a version of ip_compute_csum() optimized for IP headers, 107 * which always checksum on 4 octet boundaries. 108 */ 109 __sum16 ip_fast_csum(const void *iph, unsigned int ihl) 110 { 111 return (__force __sum16)~do_csum(iph, ihl*4); 112 } 113 EXPORT_SYMBOL(ip_fast_csum); 114 115 /* 116 * computes the checksum of a memory block at buff, length len, 117 * and adds in "sum" (32-bit) 118 * 119 * returns a 32-bit number suitable for feeding into itself 120 * or csum_tcpudp_magic 121 * 122 * this function must be called with even lengths, except 123 * for the last fragment, which may be odd 124 * 125 * it's best to have buff aligned on a 32-bit boundary 126 */ 127 __wsum csum_partial(const void *buff, int len, __wsum wsum) 128 { 129 unsigned int sum = (__force unsigned int)wsum; 130 unsigned int result = do_csum(buff, len); 131 132 /* add in old sum, and carry.. */ 133 result += sum; 134 if (sum > result) 135 result += 1; 136 return (__force __wsum)result; 137 } 138 EXPORT_SYMBOL(csum_partial); 139 140 /* 141 * this routine is used for miscellaneous IP-like checksums, mainly 142 * in icmp.c 143 */ 144 __sum16 ip_compute_csum(const void *buff, int len) 145 { 146 return (__force __sum16)~do_csum(buff, len); 147 } 148 EXPORT_SYMBOL(ip_compute_csum); 149 150 /* 151 * copy from fs while checksumming, otherwise like csum_partial 152 */ 153 __wsum 154 csum_partial_copy_from_user(const void __user *src, void *dst, int len, 155 __wsum sum, int *csum_err) 156 { 157 int missing; 158 159 missing = __copy_from_user(dst, src, len); 160 if (missing) { 161 memset(dst + len - missing, 0, missing); 162 *csum_err = -EFAULT; 163 } else 164 *csum_err = 0; 165 166 return csum_partial(dst, len, sum); 167 } 168 EXPORT_SYMBOL(csum_partial_copy_from_user); 169 170 /* 171 * copy from ds while checksumming, otherwise like csum_partial 172 */ 173 __wsum 174 csum_partial_copy(const void *src, void *dst, int len, __wsum sum) 175 { 176 memcpy(dst, src, len); 177 return csum_partial(dst, len, sum); 178 } 179 EXPORT_SYMBOL(csum_partial_copy); 180 181 #ifndef csum_tcpudp_nofold 182 __wsum csum_tcpudp_nofold(__be32 saddr, __be32 daddr, 183 unsigned short len, 184 unsigned short proto, 185 __wsum sum) 186 { 187 unsigned long long s = (__force u32)sum; 188 189 s += (__force u32)saddr; 190 s += (__force u32)daddr; 191 #ifdef __BIG_ENDIAN 192 s += proto + len; 193 #else 194 s += (proto + len) << 8; 195 #endif 196 s += (s >> 32); 197 return (__force __wsum)s; 198 } 199 EXPORT_SYMBOL(csum_tcpudp_nofold); 200 #endif 201