ConnectionManager: allow to provide RNG through configuration

Change-Id: Ic24123e329b221f5f1e24d3df6f3cc93649c4591

include/connectionmanager.h

@@ -321,6 +321,8 @@ struct ConnectionManager::Config
      */
     bool getUPnPActive() const;
 
+    /** Optional pseudo random generator to be used, allowing to control the seed. */
+    std::unique_ptr<std::mt19937_64> rng;
 };
 
 } // namespace dhtnet
\ No newline at end of file

src/connectionmanager.cpp

@@ -381,7 +381,7 @@ class ConnectionManager::Impl : public std::enable_shared_from_this<ConnectionMa
 public:
     explicit Impl(std::shared_ptr<ConnectionManager::Config> config_)
         : config_ {std::move(createConfig(config_))}
-        , rand_ {dht::crypto::getSeededRandomEngine<std::mt19937_64>()}
+        , rand_ {config_->rng ? *config_->rng : dht::crypto::getSeededRandomEngine<std::mt19937_64>()}
     {
         loadTreatedMessages();
         if(!config_->ioContext) {