meta-flow: Correctly set destination MAC in mf_set_flow_value().

[sliver-openvswitch.git] / lib / random.c

diff --git a/lib/random.c b/lib/random.c
index 78a5916..a802bc7 100644 (file)
--- a/lib/random.c
+++ b/lib/random.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2008, 2009, 2010 Nicira Networks.
+ * Copyright (c) 2008, 2009, 2010, 2011 Nicira Networks.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -17,10 +17,13 @@
 #include <config.h>
 #include "random.h"
 
+#include <assert.h>
 #include <errno.h>
 #include <stdlib.h>
 #include <sys/time.h>
 
+#include "entropy.h"
+#include "timeval.h"
 #include "util.h"
 
 /* This is the 32-bit PRNG recommended in G. Marsaglia, "Xorshift RNGs",
@@ -29,7 +32,10 @@
  *
  * We use this PRNG instead of libc's rand() because rand() varies in quality
  * and because its maximum value also varies between 32767 and INT_MAX, whereas
- * we often want random numbers in the full range of uint32_t.  */
+ * we often want random numbers in the full range of uint32_t.
+ *
+ * This random number generator is intended for purposes that do not require
+ * cryptographic-quality randomness. */
 
 /* Current random state. */
 static uint32_t seed;
@@ -39,22 +45,24 @@ static uint32_t random_next(void);
 void
 random_init(void)
 {
-    if (!seed) {
+    while (!seed) {
         struct timeval tv;
+        uint32_t entropy;
 
-        if (gettimeofday(&tv, NULL) < 0) {
-            ovs_fatal(errno, "gettimeofday");
-        }
+        xgettimeofday(&tv);
+        get_entropy_or_die(&entropy, 4);
 
-        seed = tv.tv_sec ^ tv.tv_usec;
-        if (!seed) {
-            /* A 'seed' of 0 is fatal to randomness--the random value will
-             * always be 0--so use the initial seed mentioned by Marsaglia. */
-            seed = UINT32_C(2463534242);
-        }
+        seed = tv.tv_sec ^ tv.tv_usec ^ entropy;
     }
 }
 
+void
+random_set_seed(uint32_t seed_)
+{
+    assert(seed_);
+    seed = seed_;
+}
+
 void
 random_bytes(void *p_, size_t n)
 {
@@ -102,7 +110,7 @@ static uint32_t
 random_next(void)
 {
     seed ^= seed << 13;
-    seed >>= 17;
+    seed ^= seed >> 17;
     seed ^= seed << 5;
 
     return seed;