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