/* * * 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 <linux/export.h> #include <net/checksum.h> #include <asm/byteorder.h> #ifndef do_csum static inline unsigned short from32to16(unsigned int 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 int do_csum(const unsigned char *buff, int len) { int odd; unsigned int result = 0; if (len <= 0) goto out; odd = 1 & (unsigned long) buff; if (odd) { #ifdef __LITTLE_ENDIAN result += (*buff << 8); #else result = *buff; #endif len--; buff++; } if (len >= 2) { if (2 & (unsigned long) buff) { result += *(unsigned short *) buff; len -= 2; buff += 2; } if (len >= 4) { const unsigned char *end = buff + ((unsigned)len & ~3); unsigned int carry = 0; do { unsigned int w = *(unsigned int *) buff; buff += 4; result += carry; result += w; carry = (w > result); } while (buff < end); result += carry; result = (result & 0xffff) + (result >> 16); } if (len & 2) { result += *(unsigned short *) buff; buff += 2; } } if (len & 1) #ifdef __LITTLE_ENDIAN result += *buff; #else result += (*buff << 8); #endif result = from32to16(result); if (odd) result = ((result >> 8) & 0xff) | ((result & 0xff) << 8); out: return result; } #endif /* * This is a version of ip_compute_csum() optimized for IP headers, * which always checksum on 4 octet boundaries. */ __sum16 ip_fast_csum(const void *iph, unsigned int ihl) { return (__force __sum16)~do_csum(iph, ihl*4); } EXPORT_SYMBOL(ip_fast_csum); /* * 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 */ __wsum csum_partial(const void *buff, int len, __wsum wsum) { unsigned int sum = (__force unsigned int)wsum; unsigned int result = do_csum(buff, len); /* add in old sum, and carry.. */ result += sum; if (sum > result) result += 1; return (__force __wsum)result; } EXPORT_SYMBOL(csum_partial); /* * this routine is used for miscellaneous IP-like checksums, mainly * in icmp.c */ __sum16 ip_compute_csum(const void *buff, int len) { return (__force __sum16)~do_csum(buff, len); } EXPORT_SYMBOL(ip_compute_csum); /* * copy from fs while checksumming, otherwise like csum_partial */ __wsum csum_partial_copy_from_user(const void __user *src, void *dst, int len, __wsum sum, int *csum_err) { int missing; missing = __copy_from_user(dst, src, len); if (missing) { memset(dst + len - missing, 0, missing); *csum_err = -EFAULT; } else *csum_err = 0; return csum_partial(dst, len, sum); } EXPORT_SYMBOL(csum_partial_copy_from_user); /* * copy from ds while checksumming, otherwise like csum_partial */ __wsum csum_partial_copy(const void *src, void *dst, int len, __wsum sum) { memcpy(dst, src, len); return csum_partial(dst, len, sum); } EXPORT_SYMBOL(csum_partial_copy); #ifndef csum_tcpudp_nofold __wsum csum_tcpudp_nofold(__be32 saddr, __be32 daddr, unsigned short len, unsigned short proto, __wsum sum) { unsigned long long s = (__force u32)sum; s += (__force u32)saddr; s += (__force u32)daddr; #ifdef __BIG_ENDIAN s += proto + len; #else s += (proto + len) << 8; #endif s += (s >> 32); return (__force __wsum)s; } EXPORT_SYMBOL(csum_tcpudp_nofold); #endif