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 unsigned short int csum_tcpudp_magic(unsigned long saddr, 45 unsigned long daddr, 46 unsigned short len, 47 unsigned short proto, 48 unsigned int sum) 49 { 50 return ~from64to16(saddr + daddr + sum + 51 ((unsigned long) ntohs(len) << 16) + 52 ((unsigned long) proto << 8)); 53 } 54 55 unsigned int csum_tcpudp_nofold(unsigned long saddr, 56 unsigned long daddr, 57 unsigned short len, 58 unsigned short proto, 59 unsigned int sum) 60 { 61 unsigned long result; 62 63 result = (saddr + daddr + sum + 64 ((unsigned long) ntohs(len) << 16) + 65 ((unsigned long) proto << 8)); 66 67 /* Fold down to 32-bits so we don't lose in the typedef-less 68 network stack. */ 69 /* 64 to 33 */ 70 result = (result & 0xffffffff) + (result >> 32); 71 /* 33 to 32 */ 72 result = (result & 0xffffffff) + (result >> 32); 73 return result; 74 } 75 76 /* 77 * Do a 64-bit checksum on an arbitrary memory area.. 78 * 79 * This isn't a great routine, but it's not _horrible_ either. The 80 * inner loop could be unrolled a bit further, and there are better 81 * ways to do the carry, but this is reasonable. 82 */ 83 static inline unsigned long do_csum(const unsigned char * buff, int len) 84 { 85 int odd, count; 86 unsigned long result = 0; 87 88 if (len <= 0) 89 goto out; 90 odd = 1 & (unsigned long) buff; 91 if (odd) { 92 result = *buff << 8; 93 len--; 94 buff++; 95 } 96 count = len >> 1; /* nr of 16-bit words.. */ 97 if (count) { 98 if (2 & (unsigned long) buff) { 99 result += *(unsigned short *) buff; 100 count--; 101 len -= 2; 102 buff += 2; 103 } 104 count >>= 1; /* nr of 32-bit words.. */ 105 if (count) { 106 if (4 & (unsigned long) buff) { 107 result += *(unsigned int *) buff; 108 count--; 109 len -= 4; 110 buff += 4; 111 } 112 count >>= 1; /* nr of 64-bit words.. */ 113 if (count) { 114 unsigned long carry = 0; 115 do { 116 unsigned long w = *(unsigned long *) buff; 117 count--; 118 buff += 8; 119 result += carry; 120 result += w; 121 carry = (w > result); 122 } while (count); 123 result += carry; 124 result = (result & 0xffffffff) + (result >> 32); 125 } 126 if (len & 4) { 127 result += *(unsigned int *) buff; 128 buff += 4; 129 } 130 } 131 if (len & 2) { 132 result += *(unsigned short *) buff; 133 buff += 2; 134 } 135 } 136 if (len & 1) 137 result += *buff; 138 result = from64to16(result); 139 if (odd) 140 result = ((result >> 8) & 0xff) | ((result & 0xff) << 8); 141 out: 142 return result; 143 } 144 145 /* 146 * This is a version of ip_compute_csum() optimized for IP headers, 147 * which always checksum on 4 octet boundaries. 148 */ 149 unsigned short ip_fast_csum(unsigned char * iph, unsigned int ihl) 150 { 151 return ~do_csum(iph,ihl*4); 152 } 153 154 /* 155 * computes the checksum of a memory block at buff, length len, 156 * and adds in "sum" (32-bit) 157 * 158 * returns a 32-bit number suitable for feeding into itself 159 * or csum_tcpudp_magic 160 * 161 * this function must be called with even lengths, except 162 * for the last fragment, which may be odd 163 * 164 * it's best to have buff aligned on a 32-bit boundary 165 */ 166 unsigned int csum_partial(const unsigned char * buff, int len, unsigned int sum) 167 { 168 unsigned long result = do_csum(buff, len); 169 170 /* add in old sum, and carry.. */ 171 result += sum; 172 /* 32+c bits -> 32 bits */ 173 result = (result & 0xffffffff) + (result >> 32); 174 return result; 175 } 176 177 EXPORT_SYMBOL(csum_partial); 178 179 /* 180 * this routine is used for miscellaneous IP-like checksums, mainly 181 * in icmp.c 182 */ 183 unsigned short ip_compute_csum(unsigned char * buff, int len) 184 { 185 return ~from64to16(do_csum(buff,len)); 186 } 187