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 unsigned int do_csum(const unsigned char *buff, int len) 38 { 39 int odd; 40 unsigned int result = 0; 41 42 if (len <= 0) 43 goto out; 44 odd = 1 & (unsigned long) buff; 45 if (odd) { 46 #ifdef __LITTLE_ENDIAN 47 result += (*buff << 8); 48 #else 49 result = *buff; 50 #endif 51 len--; 52 buff++; 53 } 54 if (len >= 2) { 55 if (2 & (unsigned long) buff) { 56 result += *(unsigned short *) buff; 57 len -= 2; 58 buff += 2; 59 } 60 if (len >= 4) { 61 const unsigned char *end = buff + ((unsigned)len & ~3); 62 unsigned int carry = 0; 63 do { 64 unsigned int w = *(unsigned int *) buff; 65 buff += 4; 66 result += carry; 67 result += w; 68 carry = (w > result); 69 } while (buff < end); 70 result += carry; 71 result = (result & 0xffff) + (result >> 16); 72 } 73 if (len & 2) { 74 result += *(unsigned short *) buff; 75 buff += 2; 76 } 77 } 78 if (len & 1) 79 #ifdef __LITTLE_ENDIAN 80 result += *buff; 81 #else 82 result += (*buff << 8); 83 #endif 84 result = csum_from32to16(result); 85 if (odd) 86 result = ((result >> 8) & 0xff) | ((result & 0xff) << 8); 87 out: 88 return result; 89 } 90 #endif 91 92 #ifndef ip_fast_csum 93 /* 94 * This is a version of ip_compute_csum() optimized for IP headers, 95 * which always checksum on 4 octet boundaries. 96 */ 97 __sum16 ip_fast_csum(const void *iph, unsigned int ihl) 98 { 99 return (__force __sum16)~do_csum(iph, ihl*4); 100 } 101 EXPORT_SYMBOL(ip_fast_csum); 102 #endif 103 104 /* 105 * computes the checksum of a memory block at buff, length len, 106 * and adds in "sum" (32-bit) 107 * 108 * returns a 32-bit number suitable for feeding into itself 109 * or csum_tcpudp_magic 110 * 111 * this function must be called with even lengths, except 112 * for the last fragment, which may be odd 113 * 114 * it's best to have buff aligned on a 32-bit boundary 115 */ 116 __wsum csum_partial(const void *buff, int len, __wsum wsum) 117 { 118 unsigned int sum = (__force unsigned int)wsum; 119 unsigned int result = do_csum(buff, len); 120 121 /* add in old sum, and carry.. */ 122 result += sum; 123 if (sum > result) 124 result += 1; 125 return (__force __wsum)result; 126 } 127 EXPORT_SYMBOL(csum_partial); 128 129 /* 130 * this routine is used for miscellaneous IP-like checksums, mainly 131 * in icmp.c 132 */ 133 __sum16 ip_compute_csum(const void *buff, int len) 134 { 135 return (__force __sum16)~do_csum(buff, len); 136 } 137 EXPORT_SYMBOL(ip_compute_csum); 138 139 #ifndef csum_tcpudp_nofold 140 static inline u32 from64to32(u64 x) 141 { 142 /* add up 32-bit and 32-bit for 32+c bit */ 143 x = (x & 0xffffffff) + (x >> 32); 144 /* add up carry.. */ 145 x = (x & 0xffffffff) + (x >> 32); 146 return (u32)x; 147 } 148 149 __wsum csum_tcpudp_nofold(__be32 saddr, __be32 daddr, 150 __u32 len, __u8 proto, __wsum sum) 151 { 152 unsigned long long s = (__force u32)sum; 153 154 s += (__force u32)saddr; 155 s += (__force u32)daddr; 156 #ifdef __BIG_ENDIAN 157 s += proto + len; 158 #else 159 s += (proto + len) << 8; 160 #endif 161 return (__force __wsum)from64to32(s); 162 } 163 EXPORT_SYMBOL(csum_tcpudp_nofold); 164 #endif 165