diff options
Diffstat (limited to 'usr.sbin/timed/timed/cksum.c')
| -rw-r--r-- | usr.sbin/timed/timed/cksum.c | 87 |
1 files changed, 87 insertions, 0 deletions
diff --git a/usr.sbin/timed/timed/cksum.c b/usr.sbin/timed/timed/cksum.c new file mode 100644 index 0000000..3d15af3 --- /dev/null +++ b/usr.sbin/timed/timed/cksum.c @@ -0,0 +1,87 @@ +/*- + * Copyright (c) 1985, 1993 + * The Regents of the University of California. All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * 3. All advertising materials mentioning features or use of this software + * must display the following acknowledgement: + * This product includes software developed by the University of + * California, Berkeley and its contributors. + * 4. Neither the name of the University nor the names of its contributors + * may be used to endorse or promote products derived from this software + * without specific prior written permission. + * + * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND + * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE + * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE + * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE + * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL + * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS + * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) + * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT + * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY + * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF + * SUCH DAMAGE. + */ + +#ifndef lint +static char sccsid[] = "@(#)cksum.c 8.1 (Berkeley) 6/6/93"; +#endif /* not lint */ + +#ifdef sgi +#ident "$Revision: 1.3 $" +#endif + +#include <sys/types.h> + +/* + * I N _ C K S U M + * + * Checksum routine for Internet Protocol family headers (C Version) + * + * There is no profit in a specialized version of the checksum + * function for any machine where int's are 32 bits and shorts are 16. + * + * All timed packets are smaller than 32K shorts, so there is no need to + * worry about carries except at the end. + */ +int +in_cksum(addr, len) + u_short *addr; + int len; +{ + register int nleft = len; + register u_short *w = addr; + register u_short answer; + register int sum = 0; + + /* + * Our algorithm is simple, using a 32 bit accumulator (sum), + * we add sequential 16 bit words to it, and at the end, fold + * back all the carry bits from the top 16 bits into the lower + * 16 bits. + */ + while( nleft > 1 ) { + sum += *w++; + nleft -= 2; + } + + /* mop up an odd byte, if necessary */ + if( nleft == 1 ) + sum += (*(u_char *)w) << 8; + + /* + * add back carry outs from top 16 bits to low 16 bits + */ + sum = (sum >> 16) + (sum & 0xffff); /* add hi 16 to low 16 */ + sum += (sum >> 16); /* add carry */ + answer = ~sum; /* truncate to 16 bits */ + return (answer); +} |
