More multicast related stuff.

>From Chris Maeda, cmaeda@cs.washington.edu
These patches are derived from the IP Multicast patches for BSDI.

sys/arch/i386/i386/random.s

@@ -0,0 +1,60 @@
+/*
+ * Copyright (c) 1990,1993 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: (1) source code distributions
+ * retain the above copyright notice and this paragraph in its entirety, (2)
+ * distributions including binary code include the above copyright notice and
+ * this paragraph in its entirety in the documentation or other materials
+ * provided with the distribution, and (3) all advertising materials mentioning
+ * features or use of this software display the following acknowledgement:
+ * ``This product includes software developed by the University of California,
+ * Lawrence Berkeley Laboratory and its contributors.'' 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 ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
+ * WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
+ *
+ * Here is a very good random number generator.  This implementation is
+ * based on ``Two Fast Implementations of the "Minimal Standard" Random
+ * Number Generator'', David G. Carta, Communications of the ACM, Jan 1990,
+ * Vol 33 No 1.  Do NOT modify this code unless you have a very thorough
+ * understanding of the algorithm.  It's trickier than you think.  If
+ * you do change it, make sure that its 10,000'th invocation returns
+ * 1043618065.
+ *
+ * Here is easier-to-decipher pseudocode:
+ *
+ * p = (16807*seed)<30:0>	# e.g., the low 31 bits of the product
+ * q = (16807*seed)<62:31>	# e.g., the high 31 bits starting at bit 32
+ * if (p + q < 2^31)
+ * 	seed = p + q
+ * else
+ *	seed = ((p + q) & (2^31 - 1)) + 1
+ * return (seed);
+ *
+ * The result is in (0,2^31), e.g., it's always positive.
+ */
+#include "machine/asm.h"
+
+	.data
+randseed:
+	.word	1
+	.text
+ENTRY(random)
+	movl	$16807,%eax
+	imull	randseed
+	shll	$1,%edx
+	movl	%eax,%ecx
+	and	$0x7fffffff,%eax
+	shrl	$31,%ecx
+	orl	%ecx,%edx
+	addl	%edx,%eax
+	jge	1f
+	incl	%eax
+1:
+	movl	%eax,randseed
+	ret