nic session: link-state change handling

A Nic::Session client can install a signal handler that is used to
propagate changes of the link-state by calling 'link_state_sigh()'.
The actual link state is queried via 'link_state()'.

The nic-driver interface now provides a Driver_notification callback,
which is used to forward link-state changes from the driver to the
Nic::Session_component.

The following drivers now provide real link state: dde_ipxe, nic_bridge,
and usb_drv. Currently, OpenVPN, Linux nic_drv, and lan9118 do not
support link state and always report link up.

Fixes #1327

repos/os/src/server/nic_bridge/component.cc

@@ -102,6 +102,10 @@ void Session_component::_free_ipv4_node()
 }
 
 
+bool Session_component::link_state() {
+	return Net::Env::nic()->link_state(); }
+
+
 void Session_component::set_ipv4_address(Ipv4_packet::Ipv4_address ip_addr)
 {
 	_free_ipv4_node();

repos/os/src/server/nic_bridge/component.h

@@ -105,6 +105,8 @@ namespace Net {
 			Mac_address_node   _mac_node;
 			Ipv4_address_node *_ipv4_node;
 
+			Genode::Signal_context_capability _link_state_sigh;
+
 			void _free_ipv4_node();
 
 		public:
@@ -137,8 +139,23 @@ namespace Net {
 				return m;
 			}
 
+			void link_state_changed()
+			{
+				if (_link_state_sigh.valid())
+					Genode::Signal_transmitter(_link_state_sigh).submit();
+			}
+
 			void set_ipv4_address(Ipv4_packet::Ipv4_address ip_addr);
 
+			/****************************************
+			 ** Nic::Driver notification interface **
+			 ****************************************/
+
+			bool link_state();
+
+			void link_state_sigh(Genode::Signal_context_capability sigh) {
+				_link_state_sigh = sigh; }
+
 			/******************************
 			 ** Packet_handler interface **
 			 ******************************/

repos/os/src/server/nic_bridge/nic.cc

@@ -134,4 +134,5 @@ Net::Nic::Nic()
 	_nic.rx_channel()->sigh_packet_avail(_sink_submit);
 	_nic.tx_channel()->sigh_ack_avail(_source_ack);
 	_nic.tx_channel()->sigh_ready_to_submit(_source_submit);
+	_nic.link_state_sigh(_client_link_state);
 }

repos/os/src/server/nic_bridge/nic.h

@@ -45,6 +45,7 @@ class Net::Nic : public Net::Packet_handler
 		::Nic::Connection          *nic() { return &_nic; }
 		Ethernet_frame::Mac_address mac() { return _mac; }
 
+		bool link_state() { return _nic.link_state(); }
 
 		/******************************
 		 ** Packet_handler interface **

repos/os/src/server/nic_bridge/packet_handler.cc

@@ -54,6 +54,16 @@ void Packet_handler::_ready_to_ack(unsigned)
 }
 
 
+void Packet_handler::_link_state(unsigned)
+{
+	Mac_address_node *node = Env::vlan()->mac_list()->first();
+	while (node) {
+		node->component()->link_state_changed();
+		node = node->next();
+	}
+}
+
+
 void Packet_handler::broadcast_to_clients(Ethernet_frame *eth, Genode::size_t size)
 {
 	/* check whether it's really a broadcast packet */
@@ -121,5 +131,6 @@ Packet_handler::Packet_handler()
 : _sink_ack(*Net::Env::receiver(), *this, &Packet_handler::_ack_avail),
   _sink_submit(*Net::Env::receiver(), *this, &Packet_handler::_ready_to_submit),
   _source_ack(*Net::Env::receiver(), *this, &Packet_handler::_ready_to_ack),
-  _source_submit(*Net::Env::receiver(), *this, &Packet_handler::_packet_avail)
+  _source_submit(*Net::Env::receiver(), *this, &Packet_handler::_packet_avail),
+  _client_link_state(*Net::Env::receiver(), *this, &Packet_handler::_link_state)
 { }

repos/os/src/server/nic_bridge/packet_handler.h

@@ -65,12 +65,18 @@ class Net::Packet_handler
 		 */
 		void _packet_avail(unsigned) { }
 
+		/**
+		 * the link-state of changed
+		 */
+		void _link_state(unsigned);
+
 	protected:
 
 		Genode::Signal_dispatcher<Packet_handler> _sink_ack;
 		Genode::Signal_dispatcher<Packet_handler> _sink_submit;
 		Genode::Signal_dispatcher<Packet_handler> _source_ack;
 		Genode::Signal_dispatcher<Packet_handler> _source_submit;
+		Genode::Signal_dispatcher<Packet_handler> _client_link_state;
 
 	public:
 

repos/os/src/server/nic_loopback/main.cc

@@ -142,6 +142,14 @@ namespace Nic {
 				Mac_address result = {{1,2,3,4,5,6}};
 				return result;
 			}
+
+			bool link_state()
+			{
+				/* XXX always return true, for now */
+				return true;
+			}
+
+			void link_state_sigh(Genode::Signal_context_capability sigh) { }
 	};
 
 	class Root : public Genode::Root_component<Session_component>