fix NetProto thread safety

the heartbeat thread could update serverConn at the
same time a loading client wanted to send some data,
e.g. a PE progress packet

rts/Net/Protocol/NetProtocol.cpp

@@ -112,8 +112,10 @@ float CNetProtocol::GetPacketTime(int frameNum) const
 	return (gu->startTime + frameNum / (1.0f * GAME_SPEED));
 }
 
+
 std::shared_ptr<const netcode::RawPacket> CNetProtocol::GetData(int frameNum)
 {
+	std::lock_guard<spring::spinlock> lock(serverConnMutex);
 	std::shared_ptr<const netcode::RawPacket> ret = serverConn->GetData();
 
 	if (ret == nullptr)
@@ -127,15 +129,14 @@ std::shared_ptr<const netcode::RawPacket> CNetProtocol::GetData(int frameNum)
 	return ret;
 }
 
+
+void CNetProtocol::Send(const netcode::RawPacket* pkt) { Send(std::shared_ptr<const netcode::RawPacket>(pkt)); }
 void CNetProtocol::Send(std::shared_ptr<const netcode::RawPacket> pkt)
 {
+	std::lock_guard<spring::spinlock> lock(serverConnMutex);
 	serverConn->SendData(pkt);
 }
 
-void CNetProtocol::Send(const netcode::RawPacket* pkt)
-{
-	Send(std::shared_ptr<const netcode::RawPacket>(pkt));
-}
 
 __FORCE_ALIGN_STACK__
 void CNetProtocol::UpdateLoop()
@@ -150,11 +151,16 @@ void CNetProtocol::UpdateLoop()
 
 void CNetProtocol::Update()
 {
+	// any call to clientNet->Send is unsafe while heartbeat thread exists, i.e. during loading
+	std::lock_guard<spring::spinlock> lock(serverConnMutex);
+
 	serverConn->Update();
 }
 
 void CNetProtocol::Close(bool flush)
 {
+	std::lock_guard<spring::spinlock> lock(serverConnMutex);
+
 	serverConn->Close(flush);
 }
 

rts/Net/Protocol/NetProtocol.h

@@ -8,6 +8,7 @@
 #include <memory>
 
 #include "BaseNetProtocol.h" // not used in here, but in all files including this one
+#include "System/Threading/SpringThreading.h"
 
 class ClientSetup;
 class CDemoRecorder;
@@ -111,6 +112,8 @@ class CNetProtocol
 private:
 	std::atomic<bool> keepUpdating;
 
+	spring::spinlock serverConnMutex;
+
 	std::unique_ptr<netcode::CConnection> serverConn;
 	std::unique_ptr<CDemoRecorder> demoRecorder;