1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * arch/alpha/lib/checksum.c 4 * 5 * This file contains network checksum routines that are better done 6 * in an architecture-specific manner due to speed.. 7 * Comments in other versions indicate that the algorithms are from RFC1071 8 * 9 * accelerated versions (and 21264 assembly versions ) contributed by 10 * Rick Gorton <rick.gorton@alpha-processor.com> 11 */ 12 13 #include <linux/module.h> 14 #include <linux/string.h> 15 16 #include <asm/byteorder.h> 17 18 static inline unsigned short from64to16(unsigned long x) 19 { 20 /* Using extract instructions is a bit more efficient 21 than the original shift/bitmask version. */ 22 23 union { 24 unsigned long ul; 25 unsigned int ui[2]; 26 unsigned short us[4]; 27 } in_v, tmp_v, out_v; 28 29 in_v.ul = x; 30 tmp_v.ul = (unsigned long) in_v.ui[0] + (unsigned long) in_v.ui[1]; 31 32 /* Since the bits of tmp_v.sh[3] are going to always be zero, 33 we don't have to bother to add that in. */ 34 out_v.ul = (unsigned long) tmp_v.us[0] + (unsigned long) tmp_v.us[1] 35 + (unsigned long) tmp_v.us[2]; 36 37 /* Similarly, out_v.us[2] is always zero for the final add. */ 38 return out_v.us[0] + out_v.us[1]; 39 } 40 41 /* 42 * computes the checksum of the TCP/UDP pseudo-header 43 * returns a 16-bit checksum, already complemented. 44 */ 45 __sum16 csum_tcpudp_magic(__be32 saddr, __be32 daddr, 46 __u32 len, __u8 proto, __wsum sum) 47 { 48 return (__force __sum16)~from64to16( 49 (__force u64)saddr + (__force u64)daddr + 50 (__force u64)sum + ((len + proto) << 8)); 51 } 52 EXPORT_SYMBOL(csum_tcpudp_magic); 53 54 __wsum csum_tcpudp_nofold(__be32 saddr, __be32 daddr, 55 __u32 len, __u8 proto, __wsum sum) 56 { 57 unsigned long result; 58 59 result = (__force u64)saddr + (__force u64)daddr + 60 (__force u64)sum + ((len + proto) << 8); 61 62 /* Fold down to 32-bits so we don't lose in the typedef-less 63 network stack. */ 64 /* 64 to 33 */ 65 result = (result & 0xffffffff) + (result >> 32); 66 /* 33 to 32 */ 67 result = (result & 0xffffffff) + (result >> 32); 68 return (__force __wsum)result; 69 } 70 EXPORT_SYMBOL(csum_tcpudp_nofold); 71 72 /* 73 * Do a 64-bit checksum on an arbitrary memory area.. 74 * 75 * This isn't a great routine, but it's not _horrible_ either. The 76 * inner loop could be unrolled a bit further, and there are better 77 * ways to do the carry, but this is reasonable. 78 */ 79 static inline unsigned long do_csum(const unsigned char * buff, int len) 80 { 81 int odd, count; 82 unsigned long result = 0; 83 84 if (len <= 0) 85 goto out; 86 odd = 1 & (unsigned long) buff; 87 if (odd) { 88 result = *buff << 8; 89 len--; 90 buff++; 91 } 92 count = len >> 1; /* nr of 16-bit words.. */ 93 if (count) { 94 if (2 & (unsigned long) buff) { 95 result += *(unsigned short *) buff; 96 count--; 97 len -= 2; 98 buff += 2; 99 } 100 count >>= 1; /* nr of 32-bit words.. */ 101 if (count) { 102 if (4 & (unsigned long) buff) { 103 result += *(unsigned int *) buff; 104 count--; 105 len -= 4; 106 buff += 4; 107 } 108 count >>= 1; /* nr of 64-bit words.. */ 109 if (count) { 110 unsigned long carry = 0; 111 do { 112 unsigned long w = *(unsigned long *) buff; 113 count--; 114 buff += 8; 115 result += carry; 116 result += w; 117 carry = (w > result); 118 } while (count); 119 result += carry; 120 result = (result & 0xffffffff) + (result >> 32); 121 } 122 if (len & 4) { 123 result += *(unsigned int *) buff; 124 buff += 4; 125 } 126 } 127 if (len & 2) { 128 result += *(unsigned short *) buff; 129 buff += 2; 130 } 131 } 132 if (len & 1) 133 result += *buff; 134 result = from64to16(result); 135 if (odd) 136 result = ((result >> 8) & 0xff) | ((result & 0xff) << 8); 137 out: 138 return result; 139 } 140 141 /* 142 * This is a version of ip_compute_csum() optimized for IP headers, 143 * which always checksum on 4 octet boundaries. 144 */ 145 __sum16 ip_fast_csum(const void *iph, unsigned int ihl) 146 { 147 return (__force __sum16)~do_csum(iph,ihl*4); 148 } 149 EXPORT_SYMBOL(ip_fast_csum); 150 151 /* 152 * computes the checksum of a memory block at buff, length len, 153 * and adds in "sum" (32-bit) 154 * 155 * returns a 32-bit number suitable for feeding into itself 156 * or csum_tcpudp_magic 157 * 158 * this function must be called with even lengths, except 159 * for the last fragment, which may be odd 160 * 161 * it's best to have buff aligned on a 32-bit boundary 162 */ 163 __wsum csum_partial(const void *buff, int len, __wsum sum) 164 { 165 unsigned long result = do_csum(buff, len); 166 167 /* add in old sum, and carry.. */ 168 result += (__force u32)sum; 169 /* 32+c bits -> 32 bits */ 170 result = (result & 0xffffffff) + (result >> 32); 171 return (__force __wsum)result; 172 } 173 174 EXPORT_SYMBOL(csum_partial); 175 176 /* 177 * this routine is used for miscellaneous IP-like checksums, mainly 178 * in icmp.c 179 */ 180 __sum16 ip_compute_csum(const void *buff, int len) 181 { 182 return (__force __sum16)~from64to16(do_csum(buff,len)); 183 } 184 EXPORT_SYMBOL(ip_compute_csum); 185