net_node: add a --offline argument

It will not try to connect to the monero network, nor listen

src/p2p/net_node.h

@@ -88,6 +88,7 @@ namespace nodetool
 		m_allow_local_ip(false),
 		m_hide_my_port(false),
     m_no_igd(false),
+    m_offline(false),
     m_save_graph(false),
     is_closing(false),
 		m_net_server( epee::net_utils::e_connection_type_P2P ) // this is a P2P connection of the main p2p node server, because this is class node_server<>
@@ -266,6 +267,7 @@ namespace nodetool
     bool m_allow_local_ip;
     bool m_hide_my_port;
     bool m_no_igd;
+    bool m_offline;
     std::atomic<bool> m_save_graph;
     std::atomic<bool> is_closing;
 	std::unique_ptr<std::thread> mPeersLoggerThread;

src/p2p/net_node.inl

@@ -92,6 +92,7 @@ namespace nodetool
     const command_line::arg_descriptor<bool> arg_p2p_hide_my_port   =    {"hide-my-port", "Do not announce yourself as peerlist candidate", false, true};
     
     const command_line::arg_descriptor<bool>        arg_no_igd				= {"no-igd", "Disable UPnP port mapping"};
+    const command_line::arg_descriptor<bool>        arg_offline				= {"offline", "Do not listen for peers, nor connect to any"};
     const command_line::arg_descriptor<int64_t>     arg_out_peers 			= {"out-peers", "set max limit of out peers", -1};
     const command_line::arg_descriptor<int>    		arg_tos_flag      		= {"tos-flag", "set TOS flag", -1};
     
@@ -116,6 +117,7 @@ namespace nodetool
     command_line::add_arg(desc, arg_p2p_seed_node);    
     command_line::add_arg(desc, arg_p2p_hide_my_port);
     command_line::add_arg(desc, arg_no_igd);
+    command_line::add_arg(desc, arg_offline);
     command_line::add_arg(desc, arg_out_peers);
     command_line::add_arg(desc, arg_tos_flag);
     command_line::add_arg(desc, arg_limit_rate_up);
@@ -241,6 +243,7 @@ namespace nodetool
     m_external_port = command_line::get_arg(vm, arg_p2p_external_port);
     m_allow_local_ip = command_line::get_arg(vm, arg_p2p_allow_local_ip);
     m_no_igd = command_line::get_arg(vm, arg_no_igd);
+    m_offline = command_line::get_arg(vm, arg_offline);
 
     if (command_line::has_arg(vm, arg_p2p_add_peer))
     {       
@@ -485,6 +488,10 @@ namespace nodetool
     m_net_server.get_config_object().m_invoke_timeout = P2P_DEFAULT_INVOKE_TIMEOUT;
     m_net_server.set_connection_filter(this);
 
+    // from here onwards, it's online stuff
+    if (m_offline)
+      return res;
+
     //try to bind
     LOG_PRINT_L0("Binding on " << m_bind_ip << ":" << m_port);
     res = m_net_server.init_server(m_port, m_bind_ip);
@@ -1019,6 +1026,9 @@ namespace nodetool
   template<class t_payload_net_handler>
   bool node_server<t_payload_net_handler>::make_expected_connections_count(bool white_list, size_t expected_connections)
   {
+    if (m_offline)
+      return true;
+
     size_t conn_count = get_outgoing_connections_count();
     //add new connections from white peers
     while(conn_count < expected_connections)