nic_router: advanced timeout configuration

Replace former rtt_sec attribute of the <config> tag by more specific
(and still optional) attributes for timeouts used in the NIC router
(these are also the default values):

<config dhcp_discover_timeout_sec="10"
        dhcp_request_timeout_sec="10"
        dhcp_offer_timeout_sec="10"
        udp_idle_timeout_sec="30"
        tcp_idle_timeout_sec="600"
        tcp_max_segm_lifetime_sec="30">

Details about the new attributes can be found in the README of the router.

Issue #2590

repos/libports/run/nic_dump.run

@@ -66,7 +66,7 @@ append config {
 	<start name="nic_router" caps="200" priority="-1">
 		<resource name="RAM" quantum="10M"/>
 		<provides><service name="Nic"/></provides>
-		<config rtt_sec="6" verbose="no">
+		<config verbose="no">
 
 			<policy label_prefix="udp_client_1"  domain="udp_client_1"  />
 			<policy label_prefix="http_client_3" domain="http_client_3" />

repos/libports/run/nic_router.run

@@ -83,7 +83,13 @@ append config {
 	<start name="nic_router" caps="200" priority="-1">
 		<resource name="RAM" quantum="10M"/>
 		<provides><service name="Nic"/></provides>
-		<config rtt_sec="12" verbose="no">
+		<config verbose="no"
+		        dhcp_discover_timeout_sec="3"
+		        dhcp_request_timeout_sec="3"
+		        dhcp_offer_timeout_sec="3"
+		        udp_idle_timeout_sec="30"
+		        tcp_idle_timeout_sec="30"
+		        tcp_max_segm_lifetime_sec="15">
 
 			<policy label_prefix="udp_client_1"  domain="udp_client_1"  />
 			<policy label_prefix="http_client_3" domain="http_client_3" />

repos/os/src/server/nic_router/README

@@ -211,31 +211,36 @@ the case if the transfer includes NAT no matter of what kind or for which
 side.
 
 It is desirable to discard a link state as soon as it is not needed anymore.
-The more precise the algorithm for that, the more efficient can NIC sessions
+The more precise this is done, the more efficient can NIC sessions use their
-use their resources (ports, RAM), and the less is the risk for DoS attacks.
+resources (ports, RAM), and the less is the risk for DoS attacks. Therefore,
-In order to meet this requirement, the router needs to know the round-trip
+the NIC router keeps track of the idle time of a link. Idle time means the
-time of the exchange behind a link state. This value is given through the
+time passed since the last packet was routed using that link regardless of
-attribute 'rtt_sec' in the router's configuration:
+the direction or content of that packet. The amount of idle time at which
+the NIC router shall discard a link state can be configured in the <config>
+tag of the router for each link type separately:
 
-! <config rtt_sec="3"> ... </config>
+! <config udp_idle_timeout_sec="30"
+!         tcp_idle_timeout_sec="50">
 
-This would set the round-trip time to three seconds. The value is used for all
+This would set the maximum UDP idle time to 30 and the maximum TCP idle time
-link states so you should choose it with care. If it is too low, replies that
+to 50 seconds. You should choose these values with care. If they are too low,
-normally need no routing rule may get lost. If it is too high, link states are
+replies that normally need no routing rule may get lost. If it is too high,
-held longer than necessary.
+link states are held longer than necessary.
 
-In general, each link state is discarded after a duration of the round-trip
+For UDP link states, this timeout is the only condition that leads to a
-time without a matching packet. For UDP link states, this is the only rule and
+discard. This is better known as hole punching. It allows peers to keep alive
-better known as hole punching. It allows peers to keep alive a UDP
+a UDP pseudo-connection through the router by frequently sending empty packets.
-pseudo-connection through the router by frequently sending empty packets.  The
+The need for such a pseudo-connection arises from the router's demand to
-need for such a pseudo-connection arises from the router's demand to support
+support NAT for UDP transfers and the consequence of keeping the corresponding
-NAT for UDP transfers and the consequence of keeping the corresponding mapping
+mapping information.
-information.
 
 The lifetime management of TCP link states, in contrast, is more complex. In
-addition to the common timeout, they may be discarded even if they still
+addition to the common timeout, they may be discarded also after the router
-receive packets. This is the case when the router observed the four-way
+observed the four-way termination handshake of TCP plus a duration of two
-termination handshake of TCP and the round-trip time has passed.
+times the maximum segment lifetime. The maximum segment lifetime can be be set
+in the <config> tag too:
+
+! <config tcp_max_segm_lifetime_sec="20">
 
 
 Configuring NAT
@@ -297,9 +302,13 @@ assignment in seconds. The IPv4 address range must be in the subnet
 defined by the interface attribute of the domain tag and must not cover
 the IPv4 address in this attribute. The dns_server attribute gives the
 IPv4 address of the DNS server that might also be in another subnet.
-The lifetime of an offered assignment is the configured round-trip time of
+The lifetime of an assignment that was yet only offered to the client
-the router while ip_lease_time_sec is applied only when the offer is
+can be configured for all domains in the <config> tag of the router:
-acknowledged by the client in time.
+
+! <config dhcp_offer_timeout_sec="6">
+
+The timeout ip_lease_time_sec is applied only when the offer is acknowledged
+by the client in time.
 
 
 Configuring DHCP client functionality
@@ -319,6 +328,13 @@ and all other router functionality is disabled for the domain. A domain cannot
 act as DHCP client and DHCP server at once. So, a 'domain' tag must either
 have an 'interface' attribute or must not contain a 'dhcp-server' tag.
 
+The timeouts when waiting for the reply of DHCP discover messages and for DHCP
+request messages can be configured for all domains in the <config> tag of the
+router:
+
+! <config dhcp_discover_timeout_sec="10"
+!         dhcp_request_timeout_sec="6">
+
 
 Examples
 ########

repos/os/src/server/nic_router/configuration.cc

@@ -49,7 +49,12 @@ Configuration::Configuration(Xml_node const  node,
                              Allocator      &alloc)
 :
 	_alloc(alloc), _verbose(node.attribute_value("verbose", false)),
-	_rtt(read_sec_attr(node, "rtt_sec", DEFAULT_RTT_SEC)),
+	_dhcp_discover_timeout(read_sec_attr(node, "dhcp_discover_timeout_sec", DEFAULT_DHCP_DISCOVER_TIMEOUT_SEC)),
+	_dhcp_request_timeout (read_sec_attr(node, "dhcp_request_timeout_sec",  DEFAULT_DHCP_REQUEST_TIMEOUT_SEC )),
+	_dhcp_offer_timeout   (read_sec_attr(node, "dhcp_offer_timeout_sec",    DEFAULT_DHCP_OFFER_TIMEOUT_SEC   )),
+	_udp_idle_timeout     (read_sec_attr(node, "udp_idle_timeout_sec",      DEFAULT_UDP_IDLE_TIMEOUT_SEC     )),
+	_tcp_idle_timeout     (read_sec_attr(node, "tcp_idle_timeout_sec",      DEFAULT_TCP_IDLE_TIMEOUT_SEC     )),
+	_tcp_max_segm_lifetime(read_sec_attr(node, "tcp_max_segm_lifetime_sec", DEFAULT_TCP_MAX_SEGM_LIFETIME_SEC)),
 	_node(node)
 {
 	/* read domains */

repos/os/src/server/nic_router/configuration.h

@@ -31,13 +31,23 @@ class Net::Configuration
 
 		Genode::Allocator          &_alloc;
 		bool                 const  _verbose;
-		Genode::Microseconds const  _rtt;
+		Genode::Microseconds const  _dhcp_discover_timeout;
+		Genode::Microseconds const  _dhcp_request_timeout;
+		Genode::Microseconds const  _dhcp_offer_timeout;
+		Genode::Microseconds const  _udp_idle_timeout;
+		Genode::Microseconds const  _tcp_idle_timeout;
+		Genode::Microseconds const  _tcp_max_segm_lifetime;
 		Domain_tree                 _domains;
 		Genode::Xml_node     const  _node;
 
 	public:
 
-		enum { DEFAULT_RTT_SEC = 6 };
+		enum { DEFAULT_DHCP_DISCOVER_TIMEOUT_SEC =  10 };
+		enum { DEFAULT_DHCP_REQUEST_TIMEOUT_SEC  =  10 };
+		enum { DEFAULT_DHCP_OFFER_TIMEOUT_SEC    =  10 };
+		enum { DEFAULT_UDP_IDLE_TIMEOUT_SEC      =  30 };
+		enum { DEFAULT_TCP_IDLE_TIMEOUT_SEC      = 600 };
+		enum { DEFAULT_TCP_MAX_SEGM_LIFETIME_SEC =  30 };
 
 		Configuration(Genode::Xml_node const node, Genode::Allocator &alloc);
 
@@ -47,7 +57,12 @@ class Net::Configuration
 		 ***************/
 
 		bool                  verbose()               const { return _verbose; }
-		Genode::Microseconds  rtt()     const { return _rtt; }
+		Genode::Microseconds  dhcp_discover_timeout() const { return _dhcp_discover_timeout; }
+		Genode::Microseconds  dhcp_request_timeout()  const { return _dhcp_request_timeout; }
+		Genode::Microseconds  dhcp_offer_timeout()    const { return _dhcp_offer_timeout; }
+		Genode::Microseconds  udp_idle_timeout()      const { return _udp_idle_timeout; }
+		Genode::Microseconds  tcp_idle_timeout()      const { return _tcp_idle_timeout; }
+		Genode::Microseconds  tcp_max_segm_lifetime() const { return _tcp_max_segm_lifetime; }
 		Domain_tree          &domains()                     { return _domains; }
 		Genode::Xml_node      node()                  const { return _node; }
 };

repos/os/src/server/nic_router/dhcp_client.cc

@@ -41,7 +41,7 @@ Dhcp_client::Dhcp_client(Genode::Allocator &alloc,
 
 void Dhcp_client::discover()
 {
-	_set_state(State::SELECT, _config().rtt());
+	_set_state(State::SELECT, _config().dhcp_discover_timeout());
 	_send(Message_type::DISCOVER, Ipv4_address(), Ipv4_address());
 }
 
@@ -132,7 +132,7 @@ void Dhcp_client::_handle_dhcp_reply(Dhcp_packet &dhcp)
 		if (msg_type != Message_type::OFFER) {
 			throw Packet_ignored("DHCP client expects an offer");
 		}
-		_set_state(State::REQUEST, _config().rtt());
+		_set_state(State::REQUEST, _config().dhcp_request_timeout());
 		_send(Message_type::REQUEST, dhcp.yiaddr(),
 		      dhcp.option<Dhcp_packet::Server_ipv4>().value());
 		break;

repos/os/src/server/nic_router/interface.cc

@@ -430,7 +430,7 @@ void Interface::_handle_dhcp_request(Ethernet_frame &eth,
 					throw Bad_dhcp_request();
 
 				} else {
-					allocation.lifetime(_config().rtt());
+					allocation.lifetime(_config().dhcp_offer_timeout());
 					_send_dhcp_reply(dhcp_srv, eth.src(),
 					                 allocation.ip(),
 					                 Dhcp_packet::Message_type::OFFER,
@@ -501,7 +501,7 @@ void Interface::_handle_dhcp_request(Ethernet_frame &eth,
 					Dhcp_allocation &allocation = *new (_alloc)
 						Dhcp_allocation(*this, dhcp_srv.alloc_ip(),
 						                dhcp.client_mac(), _timer,
-						                _config().rtt());
+						                _config().dhcp_offer_timeout());
 
 					_dhcp_allocations.insert(&allocation);
 					if (_config().verbose()) {

repos/os/src/server/nic_router/link.cc

@@ -117,14 +117,15 @@ Link::Link(Interface                           &cln_interface,
            Link_side_id                  const &srv_id,
            Timer::Connection                   &timer,
            Configuration                       &config,
-           L3_protocol                   const  protocol)
+           L3_protocol                   const  protocol,
+           Microseconds                  const  close_timeout)
 :
 	_config(config),
 	_client(cln_interface, cln_id, *this),
 	_server_port_alloc(srv_port_alloc),
 	_server(srv_interface, srv_id, *this),
 	_close_timeout(timer, *this, &Link::_handle_close_timeout),
-	_close_timeout_us(_config.rtt()),
+	_close_timeout_us(close_timeout),
 	_protocol(protocol)
 {
 	_close_timeout.schedule(_close_timeout_us);
@@ -172,14 +173,14 @@ Tcp_link::Tcp_link(Interface                           &cln_interface,
                    L3_protocol                   const  protocol)
 :
 	Link(cln_interface, cln_id, srv_port_alloc, srv_interface, srv_id, timer,
-	     config, protocol)
+	     config, protocol, config.tcp_idle_timeout())
 { }
 
 
 void Tcp_link::_fin_acked()
 {
 	if (_server_fin_acked && _client_fin_acked) {
-		_close_timeout.schedule(_close_timeout_us);
+		_close_timeout.schedule(Microseconds(config().tcp_max_segm_lifetime().value << 1));
 		_closed = true;
 	}
 }
@@ -233,5 +234,5 @@ Udp_link::Udp_link(Interface                           &cln_interface,
                    L3_protocol                   const  protocol)
 :
 	Link(cln_interface, cln_id, srv_port_alloc, srv_interface, srv_id, timer,
-	     config, protocol)
+	     config, protocol, config.udp_idle_timeout())
 { }

repos/os/src/server/nic_router/link.h

@@ -147,7 +147,8 @@ class Net::Link : public Link_list::Element
 		     Link_side_id                  const &srv_id,
 		     Timer::Connection                   &timer,
 		     Configuration                       &config,
-		     L3_protocol                   const  protocol);
+		     L3_protocol                   const  protocol,
+		     Genode::Microseconds          const  close_timeout);
 
 		void dissolve();
 
@@ -165,6 +166,7 @@ class Net::Link : public Link_list::Element
 
 		Link_side     &client() { return _client; }
 		Link_side     &server() { return _server; }
+		Configuration &config() { return _config; }
 };
 
 

repos/ports/run/virtualbox_nic_router.run

@@ -98,7 +98,7 @@ append_if [expr $use_net] config {
 		<binary name="nic_router"/>
 		<resource name="RAM" quantum="10M"/>
 		<provides><service name="Nic"/></provides>
-		<config rtt_sec="6" verbose="yes">
+		<config verbose="yes">
 
 			<policy label_prefix="router2" domain="router2"/>
 
@@ -126,7 +126,7 @@ append_if [expr $use_net] config {
 		<binary name="nic_router"/>
 		<resource name="RAM" quantum="10M"/>
 		<provides><service name="Nic"/></provides>
-		<config rtt_sec="6" verbose="yes">
+		<config verbose="yes">
 
 			<policy label_prefix="vbox1" domain="vbox"/>