/* * * 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_csumstatic 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 #ifndef ip_fast_csum/* *	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);#endif /* * 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 */__wsumcsum_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 */__wsumcsum_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