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 char *file_name,
  25                                   const char *function_name,
  26                                   unsigned int line_number);
  27 };
  28
  29 /*
  30  * Get a seed from a reliable source of randomness without blocking, raising
  31  * an exception on failure.
  32  */
  33 seed_t produce_true_random_seed();
  34
  35 /*
  36  * Get a random seed making a best-effort to use a true randomness source,
  37  * but falling back to a pseudo-random seed based on the time and various system
  38  * configuration values on failure.
  39  *
  40  * Note that this function attempts to use the urandom device, which will block
  41  * in the unlikely event that its pool is uninitialized, on platforms that don't
  42  * provide getrandom().
  43  */
  44 seed_t produce_best_effort_random_seed();
  45
  46 } /* namespace random */
  47 } /* namespace lttng */
  48
  49 #endif /* LTTNG_RANDOM_H */