/* $Id$ */ /* * Copyright (c) 2001-2010 Aaron Turner * Copyright (c) 2013-2015 Fred Klassen - AppNeta * * The Tcpreplay Suite of tools 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 3 of the * License, or with the authors permission any later version. * * The Tcpreplay Suite is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with the Tcpreplay Suite. If not, see . */ /* * This code is heavily based on (some might even say stolen from) Mike Shiffman's * checksumming code from Libnet 1.1.3 */ #include "incremental_checksum.h" #include "config.h" #include "tcpedit.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 WORDS_BIGENDIAN result = *buff; #else result += (*buff << 8); #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 WORDS_BIGENDIAN result += (*buff << 8); #else result += *buff; #endif 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 */ __wsum csum_partial(const void *buff, int len, __wsum wsum) { unsigned int sum = (unsigned int)wsum; unsigned int result = do_csum(buff, len); /* add in old sum, and carry.. */ result += sum; if (sum > result) result += 1; return (__wsum)result; }