/* * arch/alpha/lib/checksum.c * * This file contains network checksum routines that are better done * in an architecture-specific manner due to speed.. * Comments in other versions indicate that the algorithms are from RFC1071 * * accellerated versions (and 21264 assembly versions ) contributed by * Rick Gorton <rick.gorton@alpha-processor.com> */ #include <linux/module.h> #include <linux/string.h> #include <asm/byteorder.h> static inline unsigned short from64to16(unsigned long x) { /* Using extract instructions is a bit more efficient than the original shift/bitmask version. */ union { unsigned long ul; unsigned int ui[2]; unsigned short us[4]; } in_v, tmp_v, out_v; in_v.ul = x; tmp_v.ul = (unsigned long) in_v.ui[0] + (unsigned long) in_v.ui[1]; /* Since the bits of tmp_v.sh[3] are going to always be zero, we don't have to bother to add that in. */ out_v.ul = (unsigned long) tmp_v.us[0] + (unsigned long) tmp_v.us[1] + (unsigned long) tmp_v.us[2]; /* Similarly, out_v.us[2] is always zero for the final add. */ return out_v.us[0] + out_v.us[1]; } /* * computes the checksum of the TCP/UDP pseudo-header * returns a 16-bit checksum, already complemented. */ unsigned short int csum_tcpudp_magic(unsigned long saddr, unsigned long daddr, unsigned short len, unsigned short proto, unsigned int sum) { return ~from64to16(saddr + daddr + sum + ((unsigned long) ntohs(len) << 16) + ((unsigned long) proto << 8)); } unsigned int csum_tcpudp_nofold(unsigned long saddr, unsigned long daddr, unsigned short len, unsigned short proto, unsigned int sum) { unsigned long result; result = (saddr + daddr + sum + ((unsigned long) ntohs(len) << 16) + ((unsigned long) proto << 8)); /* Fold down to 32-bits so we don't lose in the typedef-less network stack. */ /* 64 to 33 */ result = (result & 0xffffffff) + (result >> 32); /* 33 to 32 */ result = (result & 0xffffffff) + (result >> 32); return result; } /* * Do a 64-bit checksum on an arbitrary memory area.. * * This isn't a great routine, but it's not _horrible_ either. The * inner loop could be unrolled a bit further, and there are better * ways to do the carry, but this is reasonable. */ static inline unsigned long do_csum(const unsigned char * buff, int len) { int odd, count; unsigned long result = 0; if (len <= 0) goto out; odd = 1 & (unsigned long) buff; if (odd) { result = *buff << 8; len--; buff++; } count = len >> 1; /* nr of 16-bit words.. */ if (count) { if (2 & (unsigned long) buff) { result += *(unsigned short *) buff; count--; len -= 2; buff += 2; } count >>= 1; /* nr of 32-bit words.. */ if (count) { if (4 & (unsigned long) buff) { result += *(unsigned int *) buff; count--; len -= 4; buff += 4; } count >>= 1; /* nr of 64-bit words.. */ if (count) { unsigned long carry = 0; do { unsigned long w = *(unsigned long *) buff; count--; buff += 8; result += carry; result += w; carry = (w > result); } while (count); result += carry; result = (result & 0xffffffff) + (result >> 32); } if (len & 4) { result += *(unsigned int *) buff; buff += 4; } } if (len & 2) { result += *(unsigned short *) buff; buff += 2; } } if (len & 1) result += *buff; result = from64to16(result); if (odd) result = ((result >> 8) & 0xff) | ((result & 0xff) << 8); out: return result; } /* * This is a version of ip_compute_csum() optimized for IP headers, * which always checksum on 4 octet boundaries. */ unsigned short ip_fast_csum(unsigned char * iph, unsigned int ihl) { return ~do_csum(iph,ihl*4); } /* * computes the checksum of a memory block at buff, length len, * and adds in "sum" (32-bit) * * returns a 32-bit number suitable for feeding into itself * or csum_tcpudp_magic * * this function must be called with even lengths, except * for the last fragment, which may be odd * * it's best to have buff aligned on a 32-bit boundary */ unsigned int csum_partial(const unsigned char * buff, int len, unsigned int sum) { unsigned long result = do_csum(buff, len); /* add in old sum, and carry.. */ result += sum; /* 32+c bits -> 32 bits */ result = (result & 0xffffffff) + (result >> 32); return result; } EXPORT_SYMBOL(csum_partial); /* * this routine is used for miscellaneous IP-like checksums, mainly * in icmp.c */ unsigned short ip_compute_csum(unsigned char * buff, int len) { return ~from64to16(do_csum(buff,len)); }

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