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 * accellerated 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 17 static 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 } 72 73 /* 74 * Do a 64-bit checksum on an arbitrary memory area.. 75 * 76 * This isn't a great routine, but it's not _horrible_ either. The 77 * inner loop could be unrolled a bit further, and there are better 78 * ways to do the carry, but this is reasonable. 79 */ 80 static inline unsigned long do_csum(const unsigned char * buff, int len) 81 { 82 int odd, count; 83 unsigned long result = 0; 84 85 if (len <= 0) 86 goto out; 87 odd = 1 & (unsigned long) buff; 88 if (odd) { 89 result = *buff << 8; 90 len--; 91 buff++; 92 } 93 count = len >> 1; /* nr of 16-bit words.. */ 94 if (count) { 95 if (2 & (unsigned long) buff) { 96 result += *(unsigned short *) buff; 97 count--; 98 len -= 2; 99 buff += 2; 100 } 101 count >>= 1; /* nr of 32-bit words.. */ 102 if (count) { 103 if (4 & (unsigned long) buff) { 104 result += *(unsigned int *) buff; 105 count--; 106 len -= 4; 107 buff += 4; 108 } 109 count >>= 1; /* nr of 64-bit words.. */ 110 if (count) { 111 unsigned long carry = 0; 112 do { 113 unsigned long w = *(unsigned long *) buff; 114 count--; 115 buff += 8; 116 result += carry; 117 result += w; 118 carry = (w > result); 119 } while (count); 120 result += carry; 121 result = (result & 0xffffffff) + (result >> 32); 122 } 123 if (len & 4) { 124 result += *(unsigned int *) buff; 125 buff += 4; 126 } 127 } 128 if (len & 2) { 129 result += *(unsigned short *) buff; 130 buff += 2; 131 } 132 } 133 if (len & 1) 134 result += *buff; 135 result = from64to16(result); 136 if (odd) 137 result = ((result >> 8) & 0xff) | ((result & 0xff) << 8); 138 out: 139 return result; 140 } 141 142 /* 143 * This is a version of ip_compute_csum() optimized for IP headers, 144 * which always checksum on 4 octet boundaries. 145 */ 146 __sum16 ip_fast_csum(const void *iph, unsigned int ihl) 147 { 148 return (__force __sum16)~do_csum(iph,ihl*4); 149 } 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