FreeBSD, NetBSD, OpenBSD, Solaris: Use /dev/urandom.

Cargo.toml

@@ -307,7 +307,7 @@ libc = { version = "0.2.48", default-features = false }
 [target.'cfg(all(any(target_arch = "aarch64", target_arch = "arm", target_arch = "x86", target_arch = "x86_64"), not(target_os = "ios")))'.dependencies]
 spin = { version = "0.5.0", default-features = false }
 
-[target.'cfg(any(target_os = "android", target_os = "linux"))'.dependencies]
+[target.'cfg(any(target_os = "android", target_os = "freebsd", target_os = "linux", target_os = "netbsd", target_os = "openbsd", target_os = "solaris"))'.dependencies]
 lazy_static = { version = "1.3", default-features = false, optional = true }
 
 [target.'cfg(all(target_arch = "wasm32", target_vendor = "unknown", target_os = "unknown", target_env = ""))'.dependencies]

src/rand.rs

@@ -178,6 +178,14 @@ use self::sysrand::fill as fill_impl;
 ))]
 use self::sysrand_or_urandom::fill as fill_impl;
 
+#[cfg(any(
+    target_os = "freebsd",
+    target_os = "netbsd",
+    target_os = "openbsd",
+    target_os = "solaris"
+))]
+use self::urandom::fill as fill_impl;
+
 #[cfg(any(target_os = "macos", target_os = "ios"))]
 use self::darwin::fill as fill_impl;
 
@@ -333,13 +341,26 @@ mod sysrand_or_urandom {
 
         match *MECHANISM {
             Mechanism::Sysrand => super::sysrand::fill(dest),
-            Mechanism::DevURandom => urandom_fallback(dest),
+            Mechanism::DevURandom => super::urandom::fill(dest),
         }
     }
+}
+
+#[cfg(any(
+    all(
+        any(target_os = "android", target_os = "linux"),
+        feature = "dev_urandom_fallback"
+    ),
+    target_os = "freebsd",
+    target_os = "netbsd",
+    target_os = "openbsd",
+    target_os = "solaris"
+))]
+mod urandom {
+    use crate::error;
 
-    #[cold]
-    #[inline(never)]
-    fn urandom_fallback(dest: &mut [u8]) -> Result<(), error::Unspecified> {
+    #[cfg_attr(any(target_os = "android", target_os = "linux"), cold, inline(never))]
+    pub fn fill(dest: &mut [u8]) -> Result<(), error::Unspecified> {
         use lazy_static::lazy_static;
 
         lazy_static! {