Minor improvements.

td/mtproto/Handshake.cpp

@@ -346,26 +346,33 @@ Status AuthKeyHandshake::on_message(Slice message, Callback *connection, AuthKey
   return status;
 }
 
+GlobalFloodControl::GlobalFloodControl(uint64 limit) : limit_(limit) {
+}
+
 void GlobalFloodControl::finish() {
-  // TODO: instead of decrementing count, we may wake up some pending request
-  active_count_--;
-}
-GlobalFloodControl::GlobalFloodControl(uint64_t limit) : limit_(limit) {
+  // TODO: instead of decrementing count, we can wake up some pending request
+  auto old_value = active_count_.fetch_sub(1, std::memory_order_relaxed);
+  CHECK(old_value > 0);
 }
+
 Result<GlobalFloodControl::Guard> GlobalFloodControl::try_start() {
-  if (++active_count_ > limit_) {
-    active_count_--;
-    return td::Status::Error("Handshake limit reached");
+  auto old_value = active_count_.fetch_add(1, std::memory_order_relaxed);
+  if (old_value >= limit_) {
+    finish();
+    return Status::Error("Handshake limit reached");
   }
   return Guard(this);
 }
+
 GlobalFloodControl *GlobalFloodControl::get_handshake_flood() {
-  constexpr uint64_t MAX_CONCURRENT_HANDSHAKES = 50;
+  constexpr uint64 MAX_CONCURRENT_HANDSHAKES = 250;
   static GlobalFloodControl flood{MAX_CONCURRENT_HANDSHAKES};
   return &flood;
 }
+
 void GlobalFloodControl::Finish::operator()(GlobalFloodControl *ctrl) const {
   ctrl->finish();
 }
+
 }  // namespace mtproto
 }  // namespace td

td/mtproto/Handshake.h

@@ -10,11 +10,15 @@
 #include "td/mtproto/RSA.h"
 
 #include "td/utils/buffer.h"
+#include "td/utils/common.h"
 #include "td/utils/Slice.h"
 #include "td/utils/Status.h"
 #include "td/utils/StorerBase.h"
 #include "td/utils/UInt.h"
 
+#include <atomic>
+#include <memory>
+
 namespace td {
 
 namespace mtproto_api {
@@ -27,17 +31,19 @@ class DhCallback;
 
 class GlobalFloodControl {
  public:
-  explicit GlobalFloodControl(uint64_t limit);
+  explicit GlobalFloodControl(uint64 limit);
+
   struct Finish {
     void operator()(GlobalFloodControl *ctrl) const;
   };
   using Guard = std::unique_ptr<GlobalFloodControl, Finish>;
-  td::Result<Guard> try_start();
+  Result<Guard> try_start();
+
   static GlobalFloodControl *get_handshake_flood();
 
  private:
-  std::atomic<uint64_t> active_count_{0};
-  uint64_t limit_{0};
+  std::atomic<uint64> active_count_{0};
+  uint64 limit_{0};
 
   void finish();
 };
@@ -47,7 +53,7 @@ class AuthKeyHandshakeContext {
   virtual ~AuthKeyHandshakeContext() = default;
   virtual DhCallback *get_dh_callback() = 0;
   virtual PublicRsaKeyInterface *get_public_rsa_key_interface() = 0;
-  virtual td::Status try_start() = 0;
+  virtual Status try_start() = 0;
 };
 
 class AuthKeyHandshake {

td/telegram/Td.cpp

@@ -500,8 +500,8 @@ class TestProxyRequest final : public RequestOnceActor {
       mtproto::PublicRsaKeyInterface *get_public_rsa_key_interface() final {
         return &public_rsa_key;
       }
-      td::Status try_start() final {
-        return td::Status::OK();
+      Status try_start() final {
+        return Status::OK();
       }
 
      private:

td/telegram/net/Session.cpp

@@ -79,13 +79,13 @@ class GenAuthKeyActor final : public Actor {
   CancellationTokenSource cancellation_token_source_;
 
   ActorOwn<mtproto::HandshakeActor> child_;
-  td::Status alarm_error_;
+  Status alarm_error_;
 
   void start_up() final {
     // Bug in Android clang and MSVC
     // std::tuple<Result<int>> b(std::forward_as_tuple(Result<int>()));
 
-    // Will sleep a little it there are too much active handshakes now
+    // Will sleep a little if there are too many active handshakes now
     //
     // TODO: we may want to use a blocking wait - semaphore but for actors.
     // (problem is - multiple schedulers may want to uses this semaphore)
@@ -1372,9 +1372,9 @@ void Session::create_gen_auth_key_actor(HandshakeId handshake_id) {
       return public_rsa_key_.get();
     }
 
-    td::Status try_start() {
+    Status try_start() final {
       TRY_RESULT_ASSIGN(guard_, mtproto::GlobalFloodControl::get_handshake_flood()->try_start());
-      return td::Status::OK();
+      return Status::OK();
     }
 
    private:

test/mtproto.cpp

@@ -305,6 +305,9 @@ class HandshakeContext final : public td::mtproto::AuthKeyHandshakeContext {
   td::mtproto::PublicRsaKeyInterface *get_public_rsa_key_interface() final {
     return &public_rsa_key;
   }
+  td::Status try_start() final {
+    return td::Status::OK();
+  }
 
  private:
   td::PublicRsaKeyShared public_rsa_key{td::DcId::empty(), true};