Make errno error log more useful for getrandom()

Making errno error log more useful for getrandom() call. Adding if statement to
make difference between ENOSYS and other errors.

Fixes #24500

Signed-off-by: Fernando Fernandez Mancera <ffernandezmancera@gmail.com>

changes/ticket24500

@@ -0,0 +1,3 @@
+  o Code simplification and refactoring: 
+    - Making more useful log messages for errno errors on getrandom() call.
+      Closes ticket 24500.

src/common/crypto.c

@@ -2875,8 +2875,17 @@ crypto_strongest_rand_syscall(uint8_t *out, size_t out_len)
       tor_assert(errno != EAGAIN);
       tor_assert(errno != EINTR);
 
-      /* Probably ENOSYS. */
+      /* Useful log message for errno. */
-      log_warn(LD_CRYPTO, "Can't get entropy from getrandom().");
+      if (errno == ENOSYS) {
+        log_warn(LD_CRYPTO, "This warning is caused by ENOSYS error."
+                 " You are running a version of Tor built to support"
+                 " getrandom(), but the kernel is too old and doesn't"
+                 " implement this function.");
+      } else {
+        log_warn(LD_CRYPTO, "Can't get entropy from getrandom(). %s error.",
+                 strerror(errno));
+      }
+
       getrandom_works = 0; /* Don't bother trying again. */
       return -1;
       /* LCOV_EXCL_STOP */