1 files changed, 58 insertions, 0 deletions
diff --git a/usr.sbin/ospfd/iso_cksum.c b/usr.sbin/ospfd/iso_cksum.c
new file mode 100644
index 00000000000..f3a050b37fe
--- /dev/null
+++ b/usr.sbin/ospfd/iso_cksum.c
@@ -0,0 +1,58 @@
+/*	$OpenBSD: iso_cksum.c,v 1.1 2005/01/28 14:05:40 claudio Exp $ */
+
+/*
+ * Copyright (c) 2005 Claudio Jeker <claudio@openbsd.org>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include <sys/types.h>
+
+#include "ospfd.h"
+#include "log.h"
+
+/* pos needs to be 0 for verify and 2 <= pos < len for calculation */
+u_int16_t
+iso_cksum(void *buf, u_int16_t len, u_int16_t pos)
+{
+	u_int8_t	*p = buf;
+	int		 c0 = 0, c1 = 0;	/* counters */
+	int		 r0, r1;		/* results */
+	u_int16_t	 sop;
+
+	sop = len - pos - 1;	/* pos is an offset (pos 2 is at len 3) */
+	p += 2;
+	len -= 2;
+	while (len--) {
+		c0 += *p++;
+		c1 += c0;
+		if ((len & 0xfff) == 0) {
+			/* overflow protection */
+			c0 %= 255;
+			c1 %= 255;
+		}
+	}
+	r0 = c0 = c0 % 255;
+	r1 = c1 % 255;
+
+	if (pos) {
+		r0 = ((sop * r0 - r1)) % 255;
+		if (r0 <= 0)
+			r0 += 255;
+		r1 = 510 - r0 - c0;
+		if (r1 > 255)
+			r1 -= 255;
+	}
+
+	return (r0 << 8 | r1);
+}