| /* |
| * |
| * 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/module.h> |
| #include <net/checksum.h> |
| |
| #include <asm/byteorder.h> |
| |
| 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; |
| } |
| 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; |
| } |
| |
| /* |
| * 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); |