1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* 3 * 4 * INET An implementation of the TCP/IP protocol suite for the LINUX 5 * operating system. INET is implemented using the BSD Socket 6 * interface as the means of communication with the user level. 7 * 8 * IP/TCP/UDP checksumming routines 9 * 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 files 15 * 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 as 20 * length-counter instead of the length counter 21 * (%1). Thanks to Roman Hodek for pointing this out. 22 * B: GCC seems to mess up if one uses too many 23 * data-registers to hold input values and one tries to 24 * specify d0 and d1 as scratch registers. Letting gcc 25 * choose these registers itself solves the problem. 26 */ 27 28 /* Revised by Kenneth Albanowski for m68knommu. Basic problem: unaligned access 29 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_csum 37 static 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 46 static 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_ENDIAN 56 result += (*buff << 8); 57 #else 58 result = *buff; 59 #endif 60 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_ENDIAN 89 result += *buff; 90 #else 91 result += (*buff << 8); 92 #endif 93 result = from32to16(result); 94 if (odd) 95 result = ((result >> 8) & 0xff) | ((result & 0xff) << 8); 96 out: 97 return result; 98 } 99 #endif 100 101 #ifndef ip_fast_csum 102 /* 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 } 110 EXPORT_SYMBOL(ip_fast_csum); 111 #endif 112 113 /* 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 itself 118 * or csum_tcpudp_magic 119 * 120 * this function must be called with even lengths, except 121 * for the last fragment, which may be odd 122 * 123 * it's best to have buff aligned on a 32-bit boundary 124 */ 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 } 136 EXPORT_SYMBOL(csum_partial); 137 138 /* 139 * this routine is used for miscellaneous IP-like checksums, mainly 140 * in icmp.c 141 */ 142 __sum16 ip_compute_csum(const void *buff, int len) 143 { 144 return (__force __sum16)~do_csum(buff, len); 145 } 146 EXPORT_SYMBOL(ip_compute_csum); 147 148 /* 149 * copy from ds while checksumming, otherwise like csum_partial 150 */ 151 __wsum 152 csum_partial_copy(const void *src, void *dst, int len, __wsum sum) 153 { 154 memcpy(dst, src, len); 155 return csum_partial(dst, len, sum); 156 } 157 EXPORT_SYMBOL(csum_partial_copy); 158 159 #ifndef csum_tcpudp_nofold 160 static inline u32 from64to32(u64 x) 161 { 162 /* add up 32-bit and 32-bit for 32+c bit */ 163 x = (x & 0xffffffff) + (x >> 32); 164 /* add up carry.. */ 165 x = (x & 0xffffffff) + (x >> 32); 166 return (u32)x; 167 } 168 169 __wsum csum_tcpudp_nofold(__be32 saddr, __be32 daddr, 170 __u32 len, __u8 proto, __wsum sum) 171 { 172 unsigned long long s = (__force u32)sum; 173 174 s += (__force u32)saddr; 175 s += (__force u32)daddr; 176 #ifdef __BIG_ENDIAN 177 s += proto + len; 178 #else 179 s += (proto + len) << 8; 180 #endif 181 return (__force __wsum)from64to32(s); 182 } 183 EXPORT_SYMBOL(csum_tcpudp_nofold); 184 #endif 185