1 files changed, 16 insertions, 13 deletions
diff --git a/src/random.cpp b/src/random.cpp
index 174f4cef31..b862510524 100644
--- a/src/random.cpp
+++ b/src/random.cpp
@@ -1,5 +1,5 @@
 // Copyright (c) 2009-2010 Satoshi Nakamoto
-// Copyright (c) 2009-2020 The Bitcoin Core developers
+// Copyright (c) 2009-2021 The Bitcoin Core developers
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
@@ -19,6 +19,7 @@
 #include <sync.h>     // for Mutex
 #include <util/time.h> // for GetTimeMicros()
 
+#include <cmath>
 #include <stdlib.h>
 #include <thread>
 
@@ -31,10 +32,8 @@
 #include <sys/syscall.h>
 #include <linux/random.h>
 #endif
-#if defined(HAVE_GETENTROPY) || (defined(HAVE_GETENTROPY_RAND) && defined(MAC_OSX))
-#include <unistd.h>
-#endif
 #if defined(HAVE_GETENTROPY_RAND) && defined(MAC_OSX)
+#include <unistd.h>
 #include <sys/random.h>
 #endif
 #ifdef HAVE_SYSCTL_ARND
@@ -304,16 +303,14 @@ void GetOSRand(unsigned char *ent32)
             RandFailure();
         }
     }
-#elif defined(HAVE_GETENTROPY) && defined(__OpenBSD__)
-    /* On OpenBSD this can return up to 256 bytes of entropy, will return an
-     * error if more are requested.
-     * The call cannot return less than the requested number of bytes.
-       getentropy is explicitly limited to openbsd here, as a similar (but not
-       the same) function may exist on other platforms via glibc.
+#elif defined(__OpenBSD__)
+    /* OpenBSD. From the arc4random(3) man page:
+       "Use of these functions is encouraged for almost all random number
+        consumption because the other interfaces are deficient in either
+        quality, portability, standardization, or availability."
+       The function call is always successful.
      */
-    if (getentropy(ent32, NUM_OS_RANDOM_BYTES) != 0) {
-        RandFailure();
-    }
+    arc4random_buf(ent32, NUM_OS_RANDOM_BYTES);
     // Silence a compiler warning about unused function.
     (void)GetDevURandom;
 #elif defined(HAVE_GETENTROPY_RAND) && defined(MAC_OSX)
@@ -714,3 +711,9 @@ void RandomInit()
 
     ReportHardwareRand();
 }
+
+std::chrono::microseconds GetExponentialRand(std::chrono::microseconds now, std::chrono::seconds average_interval)
+{
+    double unscaled = -std::log1p(GetRand(uint64_t{1} << 48) * -0.0000000000000035527136788 /* -1/2^48 */);
+    return now + std::chrono::duration_cast<std::chrono::microseconds>(unscaled * average_interval + 0.5us);
+}