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 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 __u32 len, __u8 proto, __wsum sum) 46 { 47 return (__force __sum16)~from64to16( 48 (__force u64)saddr + (__force u64)daddr + 49 (__force u64)sum + ((len + proto) << 8)); 50 } 51 52 __wsum csum_tcpudp_nofold(__be32 saddr, __be32 daddr, 53 __u32 len, __u8 proto, __wsum sum) 54 { 55 unsigned long result; 56 57 result = (__force u64)saddr + (__force u64)daddr + 58 (__force u64)sum + ((len + proto) << 8); 59 60 /* Fold down to 32-bits so we don't lose in the typedef-less 61 network stack. */ 62 /* 64 to 33 */ 63 result = (result & 0xffffffff) + (result >> 32); 64 /* 33 to 32 */ 65 result = (result & 0xffffffff) + (result >> 32); 66 return (__force __wsum)result; 67 } 68 EXPORT_SYMBOL(csum_tcpudp_nofold); 69 70 /* 71 * Do a 64-bit checksum on an arbitrary memory area.. 72 * 73 * This isn't a great routine, but it's not _horrible_ either. The 74 * inner loop could be unrolled a bit further, and there are better 75 * ways to do the carry, but this is reasonable. 76 */ 77 static inline unsigned long do_csum(const unsigned char * buff, int len) 78 { 79 int odd, count; 80 unsigned long result = 0; 81 82 if (len <= 0) 83 goto out; 84 odd = 1 & (unsigned long) buff; 85 if (odd) { 86 result = *buff << 8; 87 len--; 88 buff++; 89 } 90 count = len >> 1; /* nr of 16-bit words.. */ 91 if (count) { 92 if (2 & (unsigned long) buff) { 93 result += *(unsigned short *) buff; 94 count--; 95 len -= 2; 96 buff += 2; 97 } 98 count >>= 1; /* nr of 32-bit words.. */ 99 if (count) { 100 if (4 & (unsigned long) buff) { 101 result += *(unsigned int *) buff; 102 count--; 103 len -= 4; 104 buff += 4; 105 } 106 count >>= 1; /* nr of 64-bit words.. */ 107 if (count) { 108 unsigned long carry = 0; 109 do { 110 unsigned long w = *(unsigned long *) buff; 111 count--; 112 buff += 8; 113 result += carry; 114 result += w; 115 carry = (w > result); 116 } while (count); 117 result += carry; 118 result = (result & 0xffffffff) + (result >> 32); 119 } 120 if (len & 4) { 121 result += *(unsigned int *) buff; 122 buff += 4; 123 } 124 } 125 if (len & 2) { 126 result += *(unsigned short *) buff; 127 buff += 2; 128 } 129 } 130 if (len & 1) 131 result += *buff; 132 result = from64to16(result); 133 if (odd) 134 result = ((result >> 8) & 0xff) | ((result & 0xff) << 8); 135 out: 136 return result; 137 } 138 139 /* 140 * This is a version of ip_compute_csum() optimized for IP headers, 141 * which always checksum on 4 octet boundaries. 142 */ 143 __sum16 ip_fast_csum(const void *iph, unsigned int ihl) 144 { 145 return (__force __sum16)~do_csum(iph,ihl*4); 146 } 147 148 /* 149 * computes the checksum of a memory block at buff, length len, 150 * and adds in "sum" (32-bit) 151 * 152 * returns a 32-bit number suitable for feeding into itself 153 * or csum_tcpudp_magic 154 * 155 * this function must be called with even lengths, except 156 * for the last fragment, which may be odd 157 * 158 * it's best to have buff aligned on a 32-bit boundary 159 */ 160 __wsum csum_partial(const void *buff, int len, __wsum sum) 161 { 162 unsigned long result = do_csum(buff, len); 163 164 /* add in old sum, and carry.. */ 165 result += (__force u32)sum; 166 /* 32+c bits -> 32 bits */ 167 result = (result & 0xffffffff) + (result >> 32); 168 return (__force __wsum)result; 169 } 170 171 EXPORT_SYMBOL(csum_partial); 172 173 /* 174 * this routine is used for miscellaneous IP-like checksums, mainly 175 * in icmp.c 176 */ 177 __sum16 ip_compute_csum(const void *buff, int len) 178 { 179 return (__force __sum16)~from64to16(do_csum(buff,len)); 180 } 181