/* * INET An implementation of the TCP/IP protocol suite for the LINUX * operating system. INET is implemented using the BSD Socket * interface as the means of communication with the user level. * * IP/TCP/UDP checksumming routines * * Authors: Jorge Cwik, <jorge@laser.satlink.net> * Arnt Gulbrandsen, <agulbra@nvg.unit.no> * Tom May, <ftom@netcom.com> * Andreas Schwab, <schwab@issan.informatik.uni-dortmund.de> * Lots of code moved from tcp.c and ip.c; see those files * for more names. * * 03/02/96 Jes Sorensen, Andreas Schwab, Roman Hodek: * Fixed some nasty bugs, causing some horrible crashes. * A: At some points, the sum (%0) was used as * length-counter instead of the length counter * (%1). Thanks to Roman Hodek for pointing this out. * B: GCC seems to mess up if one uses too many * data-registers to hold input values and one tries to * specify d0 and d1 as scratch registers. Letting gcc choose these * registers itself solves the problem. * * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public License * as published by the Free Software Foundation; either version * 2 of the License, or (at your option) any later version. */ /* Revised by Kenneth Albanowski for m68knommu. Basic problem: unaligned access kills, so most of the assembly has to go. */ #include <net/checksum.h> #include <asm/checksum.h> static inline unsigned short from32to16(unsigned long x) { /* add up 16-bit and 16-bit for 16+c bit */ x = (x & 0xffff) + (x >> 16); /* add up carry.. */ x = (x & 0xffff) + (x >> 16); return x; } static 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; 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) { unsigned long carry = 0; do { unsigned long w = *(unsigned long *) buff; count--; buff += 4; result += carry; result += w; carry = (w > result); } while (count); result += carry; result = (result & 0xffff) + (result >> 16); } if (len & 2) { result += *(unsigned short *) buff; buff += 2; } } if (len & 1) result += (*buff << 8); result = from32to16(result); if (odd) result = ((result >> 8) & 0xff) | ((result & 0xff) << 8); out: return result; } /* * 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 int result = do_csum(buff, len); /* add in old sum, and carry.. */ result += sum; if (sum > result) result += 1; return result; } /* * this routine is used for miscellaneous IP-like checksums, mainly * in icmp.c */ unsigned short ip_compute_csum(const unsigned char * buff, int len) { return ~do_csum(buff,len); } /* * copy from fs while checksumming, otherwise like csum_partial */ unsigned int csum_partial_copy_from_user(const char *src, char *dst, int len, int sum, int *csum_err) { if (csum_err) *csum_err = 0; memcpy(dst, src, len); return csum_partial(dst, len, sum); } /* * copy from ds while checksumming, otherwise like csum_partial */ unsigned int csum_partial_copy(const char *src, char *dst, int len, int sum) { memcpy(dst, src, len); return csum_partial(dst, len, sum); }