src/common/random.hpp

   1 /*
   2  * Copyright (C) 2023 Jérémie Galarneau <jeremie.galarneau@efficios.com>
   3  *
   4  * SPDX-License-Identifier: LGPL-2.1-only
   5  *
   6  */
   7
   8 #ifndef LTTNG_RANDOM_H
   9 #define LTTNG_RANDOM_H
  10
  11 #include "exception.hpp"
  12
  13 #include <cstddef>
  14 #include <string>
  15
  16 namespace lttng {
  17 namespace random {
  18
  19 using seed_t = unsigned int;
  20
  21 class production_error : public ::lttng::runtime_error {
  22 public:
  23         explicit production_error(const std::string& msg,
  24                                   const lttng::source_location& source_location);
  25 };
  26
  27 /*
  28  * Get a seed from a reliable source of randomness without blocking, raising
  29  * an exception on failure.
  30  */
  31 seed_t produce_true_random_seed();
  32
  33 /*
  34  * Get a random seed making a best-effort to use a true randomness source,
  35  * but falling back to a pseudo-random seed based on the time and various system
  36  * configuration values on failure.
  37  *
  38  * Note that this function attempts to use the urandom device, which will block
  39  * in the unlikely event that its pool is uninitialized, on platforms that don't
  40  * provide getrandom().
  41  */
  42 seed_t produce_best_effort_random_seed();
  43
  44 } /* namespace random */
  45 } /* namespace lttng */
  46
  47 #endif /* LTTNG_RANDOM_H */