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 static inline unsigned short from32to16(unsigned long x) 41 { 42 /* add up 16-bit and 16-bit for 16+c bit */ 43 x = (x & 0xffff) + (x >> 16); 44 /* add up carry.. */ 45 x = (x & 0xffff) + (x >> 16); 46 return x; 47 } 48 49 static unsigned int do_csum(const unsigned char *buff, int len) 50 { 51 int odd, count; 52 unsigned long result = 0; 53 54 if (len <= 0) 55 goto out; 56 odd = 1 & (unsigned long) buff; 57 if (odd) { 58 #ifdef __LITTLE_ENDIAN 59 result = *buff; 60 #else 61 result += (*buff << 8); 62 #endif 63 len--; 64 buff++; 65 } 66 count = len >> 1; /* nr of 16-bit words.. */ 67 if (count) { 68 if (2 & (unsigned long) buff) { 69 result += *(unsigned short *) buff; 70 count--; 71 len -= 2; 72 buff += 2; 73 } 74 count >>= 1; /* nr of 32-bit words.. */ 75 if (count) { 76 unsigned long carry = 0; 77 do { 78 unsigned long w = *(unsigned int *) buff; 79 count--; 80 buff += 4; 81 result += carry; 82 result += w; 83 carry = (w > result); 84 } while (count); 85 result += carry; 86 result = (result & 0xffff) + (result >> 16); 87 } 88 if (len & 2) { 89 result += *(unsigned short *) buff; 90 buff += 2; 91 } 92 } 93 if (len & 1) 94 #ifdef __LITTLE_ENDIAN 95 result += *buff; 96 #else 97 result += (*buff << 8); 98 #endif 99 result = from32to16(result); 100 if (odd) 101 result = ((result >> 8) & 0xff) | ((result & 0xff) << 8); 102 out: 103 return result; 104 } 105 106 /* 107 * This is a version of ip_compute_csum() optimized for IP headers, 108 * which always checksum on 4 octet boundaries. 109 */ 110 __sum16 ip_fast_csum(const void *iph, unsigned int ihl) 111 { 112 return (__force __sum16)~do_csum(iph, ihl*4); 113 } 114 EXPORT_SYMBOL(ip_fast_csum); 115 116 /* 117 * computes the checksum of a memory block at buff, length len, 118 * and adds in "sum" (32-bit) 119 * 120 * returns a 32-bit number suitable for feeding into itself 121 * or csum_tcpudp_magic 122 * 123 * this function must be called with even lengths, except 124 * for the last fragment, which may be odd 125 * 126 * it's best to have buff aligned on a 32-bit boundary 127 */ 128 __wsum csum_partial(const void *buff, int len, __wsum wsum) 129 { 130 unsigned int sum = (__force unsigned int)wsum; 131 unsigned int result = do_csum(buff, len); 132 133 /* add in old sum, and carry.. */ 134 result += sum; 135 if (sum > result) 136 result += 1; 137 return (__force __wsum)result; 138 } 139 EXPORT_SYMBOL(csum_partial); 140 141 /* 142 * this routine is used for miscellaneous IP-like checksums, mainly 143 * in icmp.c 144 */ 145 __sum16 ip_compute_csum(const void *buff, int len) 146 { 147 return (__force __sum16)~do_csum(buff, len); 148 } 149 EXPORT_SYMBOL(ip_compute_csum); 150 151 /* 152 * copy from fs while checksumming, otherwise like csum_partial 153 */ 154 __wsum 155 csum_partial_copy_from_user(const void __user *src, void *dst, int len, 156 __wsum sum, int *csum_err) 157 { 158 int missing; 159 160 missing = __copy_from_user(dst, src, len); 161 if (missing) { 162 memset(dst + len - missing, 0, missing); 163 *csum_err = -EFAULT; 164 } else 165 *csum_err = 0; 166 167 return csum_partial(dst, len, sum); 168 } 169 EXPORT_SYMBOL(csum_partial_copy_from_user); 170 171 /* 172 * copy from ds while checksumming, otherwise like csum_partial 173 */ 174 __wsum 175 csum_partial_copy(const void *src, void *dst, int len, __wsum sum) 176 { 177 memcpy(dst, src, len); 178 return csum_partial(dst, len, sum); 179 } 180 EXPORT_SYMBOL(csum_partial_copy); 181 182 #ifndef csum_tcpudp_nofold 183 __wsum csum_tcpudp_nofold(__be32 saddr, __be32 daddr, 184 unsigned short len, 185 unsigned short proto, 186 __wsum sum) 187 { 188 unsigned long long s = (__force u32)sum; 189 190 s += (__force u32)saddr; 191 s += (__force u32)daddr; 192 #ifdef __BIG_ENDIAN 193 s += proto + len; 194 #else 195 s += (proto + len) << 8; 196 #endif 197 s += (s >> 32); 198 return (__force __wsum)s; 199 } 200 EXPORT_SYMBOL(csum_tcpudp_nofold); 201 #endif 202