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/module.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, count; 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 count = len >> 1; /* nr of 16-bit words.. */ 68 if (count) { 69 if (2 & (unsigned long) buff) { 70 result += *(unsigned short *) buff; 71 count--; 72 len -= 2; 73 buff += 2; 74 } 75 count >>= 1; /* nr of 32-bit words.. */ 76 if (count) { 77 unsigned int carry = 0; 78 do { 79 unsigned int w = *(unsigned int *) buff; 80 count--; 81 buff += 4; 82 result += carry; 83 result += w; 84 carry = (w > result); 85 } while (count); 86 result += carry; 87 result = (result & 0xffff) + (result >> 16); 88 } 89 if (len & 2) { 90 result += *(unsigned short *) buff; 91 buff += 2; 92 } 93 } 94 if (len & 1) 95 #ifdef __LITTLE_ENDIAN 96 result += *buff; 97 #else 98 result += (*buff << 8); 99 #endif 100 result = from32to16(result); 101 if (odd) 102 result = ((result >> 8) & 0xff) | ((result & 0xff) << 8); 103 out: 104 return result; 105 } 106 #endif 107 108 /* 109 * This is a version of ip_compute_csum() optimized for IP headers, 110 * which always checksum on 4 octet boundaries. 111 */ 112 __sum16 ip_fast_csum(const void *iph, unsigned int ihl) 113 { 114 return (__force __sum16)~do_csum(iph, ihl*4); 115 } 116 EXPORT_SYMBOL(ip_fast_csum); 117 118 /* 119 * computes the checksum of a memory block at buff, length len, 120 * and adds in "sum" (32-bit) 121 * 122 * returns a 32-bit number suitable for feeding into itself 123 * or csum_tcpudp_magic 124 * 125 * this function must be called with even lengths, except 126 * for the last fragment, which may be odd 127 * 128 * it's best to have buff aligned on a 32-bit boundary 129 */ 130 __wsum csum_partial(const void *buff, int len, __wsum wsum) 131 { 132 unsigned int sum = (__force unsigned int)wsum; 133 unsigned int result = do_csum(buff, len); 134 135 /* add in old sum, and carry.. */ 136 result += sum; 137 if (sum > result) 138 result += 1; 139 return (__force __wsum)result; 140 } 141 EXPORT_SYMBOL(csum_partial); 142 143 /* 144 * this routine is used for miscellaneous IP-like checksums, mainly 145 * in icmp.c 146 */ 147 __sum16 ip_compute_csum(const void *buff, int len) 148 { 149 return (__force __sum16)~do_csum(buff, len); 150 } 151 EXPORT_SYMBOL(ip_compute_csum); 152 153 /* 154 * copy from fs while checksumming, otherwise like csum_partial 155 */ 156 __wsum 157 csum_partial_copy_from_user(const void __user *src, void *dst, int len, 158 __wsum sum, int *csum_err) 159 { 160 int missing; 161 162 missing = __copy_from_user(dst, src, len); 163 if (missing) { 164 memset(dst + len - missing, 0, missing); 165 *csum_err = -EFAULT; 166 } else 167 *csum_err = 0; 168 169 return csum_partial(dst, len, sum); 170 } 171 EXPORT_SYMBOL(csum_partial_copy_from_user); 172 173 /* 174 * copy from ds while checksumming, otherwise like csum_partial 175 */ 176 __wsum 177 csum_partial_copy(const void *src, void *dst, int len, __wsum sum) 178 { 179 memcpy(dst, src, len); 180 return csum_partial(dst, len, sum); 181 } 182 EXPORT_SYMBOL(csum_partial_copy); 183 184 #ifndef csum_tcpudp_nofold 185 __wsum csum_tcpudp_nofold(__be32 saddr, __be32 daddr, 186 unsigned short len, 187 unsigned short proto, 188 __wsum sum) 189 { 190 unsigned long long s = (__force u32)sum; 191 192 s += (__force u32)saddr; 193 s += (__force u32)daddr; 194 #ifdef __BIG_ENDIAN 195 s += proto + len; 196 #else 197 s += (proto + len) << 8; 198 #endif 199 s += (s >> 32); 200 return (__force __wsum)s; 201 } 202 EXPORT_SYMBOL(csum_tcpudp_nofold); 203 #endif 204