* Copyright (c) 1988 Regents of the University of California.
* Redistribution and use in source and binary forms are permitted
* provided that the above copyright notice and this paragraph are
* duplicated in all such forms and that any documentation,
* advertising materials, and other materials related to such
* distribution and use acknowledge that the software was developed
* by the University of California, Berkeley. The name of the
* University may not be used to endorse or promote products derived
* from this software without specific prior written permission.
* THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
* WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
* @(#)in_cksum.c 7.2 (Berkeley) %G%
* Checksum routine for Internet Protocol family headers (Portable Version).
* This routine is very heavily used in the network
* code and should be modified for each CPU to be as fast as possible.
#define ADDCARRY(x) (x > 65535 ? x -= 65535 : x)
#define REDUCE {l_util.l = sum; sum = l_util.s[0] + l_util.s[1]; ADDCARRY(sum);}
for (;m
&& len
; m
= m
->m_next
) {
* The first byte of this mbuf is the continuation
* of a word spanning between this mbuf and the
* s_util.c[0] is already saved when scanning previous
s_util
.c
[1] = *(char *)w
;
w
= (u_short
*)((char *)w
+ 1);
* Force to even boundary.
if ((1 & (int) w
) && (mlen
> 0)) {
s_util
.c
[0] = *(u_char
*)w
;
w
= (u_short
*)((char *)w
+ 1);
* Unroll the loop to make overhead from
while ((mlen
-= 32) >= 0) {
sum
+= w
[0]; sum
+= w
[1]; sum
+= w
[2]; sum
+= w
[3];
sum
+= w
[4]; sum
+= w
[5]; sum
+= w
[6]; sum
+= w
[7];
sum
+= w
[8]; sum
+= w
[9]; sum
+= w
[10]; sum
+= w
[11];
sum
+= w
[12]; sum
+= w
[13]; sum
+= w
[14]; sum
+= w
[15];
while ((mlen
-= 8) >= 0) {
sum
+= w
[0]; sum
+= w
[1]; sum
+= w
[2]; sum
+= w
[3];
if (mlen
== 0 && byte_swapped
== 0)
while ((mlen
-= 2) >= 0) {
s_util
.c
[1] = *(char *)w
;
s_util
.c
[0] = *(char *)w
;
printf("cksum: out of data\n");
/* The last mbuf has odd # of bytes. Follow the
standard (the odd byte may be shifted left by 8 bits
or not as determined by endian-ness of the machine) */