X-Git-Url: http://git.onelab.eu/?a=blobdiff_plain;f=lib%2Frandom.c;h=c0bc659d19392430afd3d85d9100c735d6b73941;hb=cfc50ae514f805dcd9c14589f21158185424daf6;hp=18bd44406bb5b7880ebc41efc186516179164b74;hpb=a14bc59fb8f27db193d74662dc9c5cb8237177ef;p=sliver-openvswitch.git

diff --git a/lib/random.c b/lib/random.c
index 18bd44406..c0bc659d1 100644
--- a/lib/random.c
+++ b/lib/random.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2008, 2009 Nicira Networks.
+ * Copyright (c) 2008, 2009, 2010, 2011, 2012, 2013 Nicira, Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -21,70 +21,99 @@
 #include <stdlib.h>
 #include <sys/time.h>
 
+#include "entropy.h"
+#include "hash.h"
+#include "ovs-thread.h"
+#include "timeval.h"
 #include "util.h"
 
+/* This is the 32-bit PRNG recommended in G. Marsaglia, "Xorshift RNGs",
+ * _Journal of Statistical Software_ 8:14 (July 2003).  According to the paper,
+ * it has a period of 2**32 - 1 and passes almost all tests of randomness.
+ *
+ * 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.
+ *
+ * This random number generator is intended for purposes that do not require
+ * cryptographic-quality randomness. */
+
+/* Current random state. */
+DEFINE_STATIC_PER_THREAD_DATA(uint32_t, seed, 0);
+
+static uint32_t random_next(void);
+
 void
 random_init(void)
 {
-    static bool inited = false;
-    if (!inited) {
+    uint32_t *seedp = seed_get();
+    while (!*seedp) {
         struct timeval tv;
-        inited = true;
-        if (gettimeofday(&tv, NULL) < 0) {
-            ovs_fatal(errno, "gettimeofday");
-        }
-        srand(tv.tv_sec ^ tv.tv_usec);
+        uint32_t entropy;
+        pthread_t self;
+
+        xgettimeofday(&tv);
+        get_entropy_or_die(&entropy, 4);
+        self = pthread_self();
+
+        *seedp = (tv.tv_sec ^ tv.tv_usec ^ entropy
+                  ^ hash_bytes(&self, sizeof self, 0));
     }
 }
 
+void
+random_set_seed(uint32_t seed_)
+{
+    ovs_assert(seed_);
+    *seed_get() = seed_;
+}
+
 void
 random_bytes(void *p_, size_t n)
 {
     uint8_t *p = p_;
+
     random_init();
-    while (n--) {
-        *p++ = rand();
+
+    for (; n > 4; p += 4, n -= 4) {
+        uint32_t x = random_next();
+        memcpy(p, &x, 4);
+    }
+
+    if (n) {
+        uint32_t x = random_next();
+        memcpy(p, &x, n);
     }
 }
 
-uint8_t
-random_uint8(void)
+
+uint32_t
+random_uint32(void)
 {
     random_init();
-    return rand();
+    return random_next();
 }
 
-uint16_t
-random_uint16(void)
+uint64_t
+random_uint64(void)
 {
-    if (RAND_MAX >= UINT16_MAX) {
-        random_init();
-        return rand();
-    } else {
-        uint16_t x;
-        random_bytes(&x, sizeof x);
-        return x;
-    }
-}
+    uint64_t x;
 
-uint32_t
-random_uint32(void)
-{
-    if (RAND_MAX >= UINT32_MAX) {
-        random_init();
-        return rand();
-    } else if (RAND_MAX == INT32_MAX) {
-        random_init();
-        return rand() | ((rand() & 1u) << 31);
-    } else {
-        uint32_t x;
-        random_bytes(&x, sizeof x);
-        return x;
-    }
+    random_init();
+
+    x = random_next();
+    x |= (uint64_t) random_next() << 32;
+    return x;
 }
 
-int
-random_range(int max) 
+static uint32_t
+random_next(void)
 {
-    return random_uint32() % max;
+    uint32_t *seedp = seed_get_unsafe();
+
+    *seedp ^= *seedp << 13;
+    *seedp ^= *seedp >> 17;
+    *seedp ^= *seedp << 5;
+
+    return *seedp;
 }