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 EXPORT_SYMBOL(csum_tcpudp_magic); 52 53 __wsum csum_tcpudp_nofold(__be32 saddr, __be32 daddr, 54 __u32 len, __u8 proto, __wsum sum) 55 { 56 unsigned long result; 57 58 result = (__force u64)saddr + (__force u64)daddr + 59 (__force u64)sum + ((len + proto) << 8); 60 61 /* Fold down to 32-bits so we don't lose in the typedef-less 62 network stack. */ 63 /* 64 to 33 */ 64 result = (result & 0xffffffff) + (result >> 32); 65 /* 33 to 32 */ 66 result = (result & 0xffffffff) + (result >> 32); 67 return (__force __wsum)result; 68 } 69 EXPORT_SYMBOL(csum_tcpudp_nofold); 70 71 /* 72 * Do a 64-bit checksum on an arbitrary memory area.. 73 * 74 * This isn't a great routine, but it's not _horrible_ either. The 75 * inner loop could be unrolled a bit further, and there are better 76 * ways to do the carry, but this is reasonable. 77 */ 78 static inline unsigned long do_csum(const unsigned char * buff, int len) 79 { 80 int odd, count; 81 unsigned long result = 0; 82 83 if (len <= 0) 84 goto out; 85 odd = 1 & (unsigned long) buff; 86 if (odd) { 87 result = *buff << 8; 88 len--; 89 buff++; 90 } 91 count = len >> 1; /* nr of 16-bit words.. */ 92 if (count) { 93 if (2 & (unsigned long) buff) { 94 result += *(unsigned short *) buff; 95 count--; 96 len -= 2; 97 buff += 2; 98 } 99 count >>= 1; /* nr of 32-bit words.. */ 100 if (count) { 101 if (4 & (unsigned long) buff) { 102 result += *(unsigned int *) buff; 103 count--; 104 len -= 4; 105 buff += 4; 106 } 107 count >>= 1; /* nr of 64-bit words.. */ 108 if (count) { 109 unsigned long carry = 0; 110 do { 111 unsigned long w = *(unsigned long *) buff; 112 count--; 113 buff += 8; 114 result += carry; 115 result += w; 116 carry = (w > result); 117 } while (count); 118 result += carry; 119 result = (result & 0xffffffff) + (result >> 32); 120 } 121 if (len & 4) { 122 result += *(unsigned int *) buff; 123 buff += 4; 124 } 125 } 126 if (len & 2) { 127 result += *(unsigned short *) buff; 128 buff += 2; 129 } 130 } 131 if (len & 1) 132 result += *buff; 133 result = from64to16(result); 134 if (odd) 135 result = ((result >> 8) & 0xff) | ((result & 0xff) << 8); 136 out: 137 return result; 138 } 139 140 /* 141 * This is a version of ip_compute_csum() optimized for IP headers, 142 * which always checksum on 4 octet boundaries. 143 */ 144 __sum16 ip_fast_csum(const void *iph, unsigned int ihl) 145 { 146 return (__force __sum16)~do_csum(iph,ihl*4); 147 } 148 EXPORT_SYMBOL(ip_fast_csum); 149 150 /* 151 * computes the checksum of a memory block at buff, length len, 152 * and adds in "sum" (32-bit) 153 * 154 * returns a 32-bit number suitable for feeding into itself 155 * or csum_tcpudp_magic 156 * 157 * this function must be called with even lengths, except 158 * for the last fragment, which may be odd 159 * 160 * it's best to have buff aligned on a 32-bit boundary 161 */ 162 __wsum csum_partial(const void *buff, int len, __wsum sum) 163 { 164 unsigned long result = do_csum(buff, len); 165 166 /* add in old sum, and carry.. */ 167 result += (__force u32)sum; 168 /* 32+c bits -> 32 bits */ 169 result = (result & 0xffffffff) + (result >> 32); 170 return (__force __wsum)result; 171 } 172 173 EXPORT_SYMBOL(csum_partial); 174 175 /* 176 * this routine is used for miscellaneous IP-like checksums, mainly 177 * in icmp.c 178 */ 179 __sum16 ip_compute_csum(const void *buff, int len) 180 { 181 return (__force __sum16)~from64to16(do_csum(buff,len)); 182 } 183 EXPORT_SYMBOL(ip_compute_csum); 184