[Steam only] Fix locking issues

Related to the legacy poll group when destroying listen sockets.
(We don't need this legacy support in this library, since we don't
have to support old interfaces.)

P4:6571400

Author: zpostfacto

src/steamnetworkingsockets/clientlib/csteamnetworkingsockets.cpp

@@ -1298,8 +1298,10 @@ int CSteamNetworkingSockets::ReceiveMessagesOnListenSocketLegacyPollGroup( HStea
 	CSteamNetworkListenSocketBase *pSock = GetListenSocketByHandle( hSocket );
 	if ( !pSock )
 		return -1;
+	if ( !pSock->m_pLegacyPollGroup )
+		return 0;
 	g_lockAllRecvMessageQueues.lock();
-	int nMessagesReceived = pSock->m_legacyPollGroup.m_queueRecvMessages.RemoveMessages( ppOutMessages, nMaxMessages );
+	int nMessagesReceived = pSock->m_pLegacyPollGroup->m_queueRecvMessages.RemoveMessages( ppOutMessages, nMaxMessages );
 	g_lockAllRecvMessageQueues.unlock();
 	return nMessagesReceived;
 }

src/steamnetworkingsockets/clientlib/steamnetworkingsockets_connections.cpp

@@ -346,7 +346,6 @@ CSteamNetworkPollGroup::~CSteamNetworkPollGroup()
 	// Object deletion is rare; to keep things simple we require the global lock
 	SteamNetworkingGlobalLock::AssertHeldByCurrentThread();
 	m_lock.AssertHeldByCurrentThread();
-	g_tables_lock.AssertHeldByCurrentThread();
 
 	FOR_EACH_VEC_BACK( m_vecConnections, i )
 	{
@@ -385,6 +384,7 @@ CSteamNetworkPollGroup::~CSteamNetworkPollGroup()
 	// Remove us from global table, if we're in it
 	if ( m_hPollGroupSelf != k_HSteamNetPollGroup_Invalid )
 	{
+		g_tables_lock.AssertHeldByCurrentThread();
 		int idx = m_hPollGroupSelf & 0xffff;
 		if ( g_mapPollGroups.IsValidIndex( idx ) && g_mapPollGroups[ idx ] == this )
 		{
@@ -443,9 +443,6 @@ void CSteamNetworkPollGroup::AssignHandleAndAddToGlobalTable()
 CSteamNetworkListenSocketBase::CSteamNetworkListenSocketBase( CSteamNetworkingSockets *pSteamNetworkingSocketsInterface )
 : m_pSteamNetworkingSocketsInterface( pSteamNetworkingSocketsInterface )
 , m_hListenSocketSelf( k_HSteamListenSocket_Invalid )
-#ifdef STEAMNETWORKINGSOCKETS_STEAMCLIENT
-, m_legacyPollGroup( pSteamNetworkingSocketsInterface )
-#endif
 {
 	m_connectionConfig.Init( &pSteamNetworkingSocketsInterface->m_connectionConfig );
 }
@@ -473,6 +470,10 @@ CSteamNetworkListenSocketBase::~CSteamNetworkListenSocketBase()
 
 		m_hListenSocketSelf = k_HSteamListenSocket_Invalid;
 	}
+
+	#ifdef STEAMNETWORKINGSOCKETS_STEAMCLIENT
+		Assert( !m_pLegacyPollGroup ); // Should have been cleaned up by Destroy()
+	#endif
 }
 
 bool CSteamNetworkListenSocketBase::BInitListenSocketCommon( int nOptions, const SteamNetworkingConfigValue_t *pOptions, SteamDatagramErrMsg &errMsg )
@@ -556,6 +557,14 @@ void CSteamNetworkListenSocketBase::Destroy()
 		Assert( m_mapChildConnections.Count() == n-1 );
 	}
 
+	#ifdef STEAMNETWORKINGSOCKETS_STEAMCLIENT
+	if ( m_pLegacyPollGroup )
+	{
+		m_pLegacyPollGroup->m_lock.lock(); // Don't use scope object.  It will unlock when we destruct
+		m_pLegacyPollGroup.reset();
+	}
+	#endif
+
 	// Self destruct
 	delete this;
 }
@@ -615,7 +624,11 @@ bool CSteamNetworkListenSocketBase::BAddChildConnection( CSteamNetworkConnection
 	// Don't override it, if so.)
 	#ifdef STEAMNETWORKINGSOCKETS_STEAMCLIENT
 	if ( !pConn->m_pPollGroup )
-		pConn->SetPollGroup( &m_legacyPollGroup );
+	{
+		if ( !m_pLegacyPollGroup )
+			m_pLegacyPollGroup.reset( new CSteamNetworkPollGroup( m_pSteamNetworkingSocketsInterface ) );
+		pConn->SetPollGroup( m_pLegacyPollGroup.get() );
+	}
 	#endif
 
 	return true;

src/steamnetworkingsockets/clientlib/steamnetworkingsockets_connections.h

@@ -264,7 +264,7 @@ class CSteamNetworkListenSocketBase
 
 	/// For legacy interface.
 	#ifdef STEAMNETWORKINGSOCKETS_STEAMCLIENT
-	CSteamNetworkPollGroup m_legacyPollGroup;
+	std::unique_ptr<CSteamNetworkPollGroup> m_pLegacyPollGroup;
 	#endif
 
 protected: