240 lines
6.3 KiB
C
240 lines
6.3 KiB
C
/*-
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* Copyright (c) 1990 The Regents of the University of California.
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by the University of
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* California, Berkeley and its contributors.
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* 4. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* from tahoe: in_cksum.c 1.2 86/01/05
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* from: @(#)in_cksum.c 1.3 (Berkeley) 1/19/91
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* $Id$
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*/
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#include <sys/param.h>
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#include <sys/systm.h>
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#include <sys/mbuf.h>
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extern int in_cksum __P((struct mbuf *m, int len));
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/*
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* Checksum routine for Internet Protocol family headers.
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*
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* This routine is very heavily used in the network
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* code and should be modified for each CPU to be as fast as possible.
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*
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* This implementation is 386 version.
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*/
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#undef ADDCARRY
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#define ADDCARRY(x) if ((x) > 0xffff) (x) -= 0xffff
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#define REDUCE {sum = (sum & 0xffff) + (sum >> 16); ADDCARRY(sum);}
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/*
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* Thanks to gcc we don't have to guess
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* which registers contain sum & w.
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*/
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#define ADD(n) asm("addl " #n "(%2), %0" : "=r" (sum) : "0" (sum), "r" (w))
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#define ADDC(n) asm("adcl " #n "(%2), %0" : "=r" (sum) : "0" (sum), "r" (w))
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#define LOAD(n) asm volatile("movb " #n "(%1), %0" : "=r" (junk) : "r" (w))
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#define MOP asm("adcl $0, %0" : "=r" (sum) : "0" (sum))
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int
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in_cksum(m, len)
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register struct mbuf *m;
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register int len;
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{
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register u_short *w;
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register unsigned sum = 0;
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register int mlen = 0;
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int byte_swapped = 0;
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union { char c[2]; u_short s; } su;
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for (;m && len; m = m->m_next) {
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if (m->m_len == 0)
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continue;
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w = mtod(m, u_short *);
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if (mlen == -1) {
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/*
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* The first byte of this mbuf is the continuation
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* of a word spanning between this mbuf and the
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* last mbuf.
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*/
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/* su.c[0] is already saved when scanning previous
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* mbuf. sum was REDUCEd when we found mlen == -1
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*/
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su.c[1] = *(u_char *)w;
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sum += su.s;
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w = (u_short *)((char *)w + 1);
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mlen = m->m_len - 1;
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len--;
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} else
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mlen = m->m_len;
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if (len < mlen)
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mlen = len;
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len -= mlen;
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/*
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* Force to long boundary so we do longword aligned
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* memory operations
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*/
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if (3 & (int) w) {
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REDUCE;
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if ((1 & (int) w) && (mlen > 0)) {
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sum <<= 8;
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su.c[0] = *(char *)w;
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w = (u_short *)((char *)w + 1);
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mlen--;
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byte_swapped = 1;
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}
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if ((2 & (int) w) && (mlen >= 2)) {
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sum += *w++;
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mlen -= 2;
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}
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}
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/*
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* Advance to a 486 cache line boundary.
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*/
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if (4 & (int) w && mlen >= 4) {
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ADD(0);
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MOP;
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w += 2;
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mlen -= 4;
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}
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if (8 & (int) w && mlen >= 8) {
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ADD(0);
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ADDC(4);
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MOP;
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w += 4;
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mlen -= 8;
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}
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/*
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* Do as much of the checksum as possible 32 bits at at time.
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* In fact, this loop is unrolled to make overhead from
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* branches &c small.
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*/
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mlen -= 1;
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while ((mlen -= 32) >= 0) {
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u_char junk;
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/*
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* Add with carry 16 words and fold in the last
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* carry by adding a 0 with carry.
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*
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* The early ADD(16) and the LOAD(32) are to load
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* the next 2 cache lines in advance on 486's. The
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* 486 has a penalty of 2 clock cycles for loading
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* a cache line, plus whatever time the external
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* memory takes to load the first word(s) addressed.
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* These penalties are unavoidable. Subsequent
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* accesses to a cache line being loaded (and to
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* other external memory?) are delayed until the
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* whole load finishes. These penalties are mostly
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* avoided by not accessing external memory for
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* 8 cycles after the ADD(16) and 12 cycles after
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* the LOAD(32). The loop terminates when mlen
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* is initially 33 (not 32) to guaranteed that
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* the LOAD(32) is within bounds.
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*/
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ADD(16);
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ADDC(0);
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ADDC(4);
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ADDC(8);
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ADDC(12);
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LOAD(32);
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ADDC(20);
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ADDC(24);
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ADDC(28);
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MOP;
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w += 16;
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}
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mlen += 32 + 1;
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if (mlen >= 32) {
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ADD(16);
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ADDC(0);
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ADDC(4);
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ADDC(8);
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ADDC(12);
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ADDC(20);
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ADDC(24);
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ADDC(28);
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MOP;
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w += 16;
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mlen -= 32;
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}
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if (mlen >= 16) {
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ADD(0);
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ADDC(4);
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ADDC(8);
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ADDC(12);
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MOP;
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w += 8;
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mlen -= 16;
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}
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if (mlen >= 8) {
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ADD(0);
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ADDC(4);
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MOP;
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w += 4;
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mlen -= 8;
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}
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if (mlen == 0 && byte_swapped == 0)
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continue; /* worth 1% maybe ?? */
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REDUCE;
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while ((mlen -= 2) >= 0) {
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sum += *w++;
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}
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if (byte_swapped) {
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sum <<= 8;
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byte_swapped = 0;
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if (mlen == -1) {
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su.c[1] = *(char *)w;
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sum += su.s;
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mlen = 0;
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} else
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mlen = -1;
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} else if (mlen == -1)
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/*
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* This mbuf has odd number of bytes.
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* There could be a word split betwen
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* this mbuf and the next mbuf.
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* Save the last byte (to prepend to next mbuf).
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*/
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su.c[0] = *(char *)w;
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}
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if (len)
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printf("cksum: out of data\n");
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if (mlen == -1) {
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/* The last mbuf has odd # of bytes. Follow the
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standard (the odd byte is shifted left by 8 bits) */
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su.c[1] = 0;
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sum += su.s;
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}
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REDUCE;
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return (~sum & 0xffff);
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}
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