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