nic_router: propagate dns domain name via dhcp

With this commit, the NIC router DHCP client reads out the first DNS domain
name (DHCP option 15) if any from a DHCP reply that generates an IPv4 config
for a domain and stores the name together with the IPv4 config for that domain.
DNS domain names are reported via the new report tag '<dns-domain>' if the
'config' attribute in the config tag '<report>' is set.

Furthermore, the NIC router DHCP server becomes able to obtain a DNS domain
name from another domain that has a DHCP client dynamically (given the config
attribute 'dns_config_from' is set and no static DNS config is given) or
statically from its configuration (new config tag '<dns-domain>') and propagate
this name with DHCP replies (DHCP option 15).

The 'nic_router_dhcp_*' tests are adapted to test the new feautures.

The commit also gets rid of some mirrored files in
'test/nic_router_dhcp/manager'.

Fixes #4246

repos/os/include/net/dhcp.h

@@ -127,6 +127,7 @@ class Net::Dhcp_packet
 					SUBNET_MASK    = 1,
 					ROUTER         = 3,
 					DNS_SERVER     = 6,
+					DOMAIN_NAME    = 15,
 					BROADCAST_ADDR = 28,
 					REQ_IP_ADDR    = 50,
 					IP_LEASE_TIME  = 51,
@@ -227,6 +228,28 @@ class Net::Dhcp_packet
 				}
 		};
 
+		/**
+		 * Domain name option
+		 */
+		class Domain_name : public Option
+		{
+			private:
+
+				char _name[0];
+
+			public:
+
+				static constexpr Code CODE = Code::DOMAIN_NAME;
+
+				Domain_name (Genode::size_t len) : Option(CODE, len) { }
+
+				template <typename FUNC>
+				void with_string(FUNC && func) const
+				{
+					func(_name, Option::len());
+				}
+		};
+
 		enum class Message_type : Genode::uint8_t {
 			DISCOVER  = 1,
 			OFFER     = 2,
@@ -442,6 +465,16 @@ class Net::Dhcp_packet
 
 					_base += header_size + data.size();
 				}
+
+				void append_domain_name(char     const *data_src,
+				                        Genode::size_t  data_size)
+				{
+					Genode::size_t const header_size { sizeof(Domain_name) };
+					_size_guard.consume_head(header_size + data_size);
+					Genode::memcpy((char *)(_base + header_size), data_src, data_size);
+					Genode::construct_at<Domain_name>((void *)_base, data_size);
+					_base += header_size + data_size;
+				}
 		};
 
 

repos/os/run/nic_router_dhcp.inc

@@ -63,6 +63,7 @@ append config {
 								<dns-server ip="1.2.3.4"/>
 								<dns-server ip="2.3.4.5"/>
 								<dns-server ip="3.4.5.6"/>
+								<dns-domain name="genode.org"/>
 
 							</dhcp-server>
 
@@ -96,7 +97,7 @@ append config {
 				<sleep milliseconds="2000"/>
 				<inline>
 
-					<config>
+					<config verbose="yes">
 
 						<policy label="nic_router_2 -> " domain="downlink"/>
 
@@ -106,6 +107,7 @@ append config {
 							             ip_last="10.2.4.2">
 
 								<dns-server ip="6.7.8.9"/>
+								<dns-domain name="this_is_a_way_to_long_dns_domain_name_that_should_be_rejected_by_the_router_and_cause_the_corresponding_dhcp_option_to_disappear_but_you_never_know_and_so_we_better_test_it"/>
 
 							</dhcp-server>
 
@@ -126,6 +128,8 @@ append config {
 							<dhcp-server ip_first="10.2.4.200"
 							             ip_last="10.2.4.200">
 
+								<dns-domain name="genodians.org"/>
+
 							</dhcp-server>
 
 						</domain>
@@ -145,6 +149,8 @@ append config {
 							<dhcp-server ip_first="10.2.3.2"
 							             ip_last="10.2.3.2">
 
+								<dns-domain name="genodians.org"/>
+
 							</dhcp-server>
 
 						</domain>
@@ -281,6 +287,7 @@ append done_string ".*  Router: 10.0.3.1.*\n"
 append done_string ".*  DNS server #1: 1.2.3.4.*\n"
 append done_string ".*  DNS server #2: 2.3.4.5.*\n"
 append done_string ".*  DNS server #3: 3.4.5.6.*\n"
+append done_string ".*  DNS domain name: genode.org.*\n"
 append done_string ".*DHCP request completed:.*\n"
 append done_string ".*  IP lease time: 3600 seconds.*\n"
 append done_string ".*  Interface: 10.0.3.2/24.*\n"
@@ -296,10 +303,12 @@ append done_string ".*DHCP request completed:.*\n"
 append done_string ".*  IP lease time: 3600 seconds.*\n"
 append done_string ".*  Interface: 10.0.3.2/24.*\n"
 append done_string ".*  Router: 10.0.3.1.*\n"
+append done_string ".*  DNS domain name: genodians.org.*\n"
 append done_string ".*DHCP request completed:.*\n"
 append done_string ".*  IP lease time: 3600 seconds.*\n"
 append done_string ".*  Interface: 10.0.3.2/24.*\n"
 append done_string ".*  Router: 10.0.3.1.*\n"
+append done_string ".*  DNS domain name: genodians.org.*\n"
 append done_string ".*DHCP request completed:.*\n"
 append done_string ".*  IP lease time: 3600 seconds.*\n"
 append done_string ".*  Interface: 10.0.3.2/24.*\n"
@@ -307,5 +316,6 @@ append done_string ".*  Router: 10.0.3.1.*\n"
 append done_string ".*  DNS server #1: 1.2.3.4.*\n"
 append done_string ".*  DNS server #2: 2.3.4.5.*\n"
 append done_string ".*  DNS server #3: 3.4.5.6.*\n"
+append done_string ".*  DNS domain name: genode.org.*\n"
 
 run_genode_until $done_string 30

repos/os/src/server/nic_router/README

@@ -441,6 +441,7 @@ this:
 !                  ip_last="10.0.1.100"
 !                  ip_lease_time_sec="3600">
 !
+!         <dns-domain name="genodians.org" />
 !         <dns-server ip="8.8.8.8" />
 !         <dns-server ip="1.1.1.1" />
 !         ...
@@ -468,6 +469,10 @@ lifetime of an IPv4 address 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 given by this attribute.
 
+The <dns-domain> sub-tag from the first example statically provides a DNS
+domain name that shall be propagated by the DHCP server through a DHCP option
+15 entry to its clients.
+
 The <dns-server> sub-tags from the first example statically provide a list of
 DNS server addresses that shall be propagated by the DHCP server through a DHCP
 option 6 entry to its clients. These addresses might be of any IP subnet. The
@@ -475,14 +480,15 @@ addresses in the DHCP option 6 entry in the DHCP replies will have the same
 order as the <dns-server> tags in the configuration.
 
 The 'dns_config_from' attribute from the second example takes effect only when
-the <dhcp-server> tag does not contain any <dns-server> sub-tags. The attribute
+the <dhcp-server> tag does not contain any <dns-domain> or <dns-server>
-states the domain from whose IP config to take the list of propagated DNS
+sub-tags. The attribute states the domain from whose IP config to take the DNS
-server addresses. Note that the order of DNS server adresses is not altered
+domain name and the list of DNS server addresses that shall be propagated. Note
-thereby. This is useful in scenarios where these addresses must be obtained
+that the order of DNS server adresses is not altered thereby. This is useful in
-dynamically through the DHCP client of another domain. An implication of the
+scenarios where these addresses must be obtained dynamically through the DHCP
-'dns_config_from' attribute is that the link state of all interfaces at the
+client of another domain. An implication of the 'dns_config_from' attribute is
-domain with the DHCP server becomes bound to the validity of the IP config of
+that the link state of all interfaces at the domain with the DHCP server
-the domain that is stated in the attribute.
+becomes bound to the validity of the IP config of the domain that is stated in
+the attribute.
 
 The lifetime of an IP address assignment that was yet only offered to the
 client can be configured for all domains in the <config> tag of the router:
@@ -548,6 +554,7 @@ A complete state report of the NIC router is structured the following way
 !   <domain name="domain_1" rx_bytes="17597" tx_bytes="7788"
 !           ipv4="100.200.0.10/24" gw="100.200.0.1">
 !
+!     <dns-domain name="genodians.org"/>
 !     <dns ip="100.200.0.8"/>
 !     <dns ip="1.1.1.1"/>
 !     <dns ip="8.8.8.8"/>
@@ -687,14 +694,15 @@ simply the 'limit' value minus the 'used' value.
 'config'
 
 A boolean value that controls whether the attributes 'ipv4' and 'gw' of the
-<domain> tag and the subtag <dns> in the <domain> tag are generated. The
+<domain> tag and the subtags <dns> and <dns-domain> in the <domain> tag are
-attribute 'ipv4' contains the current IPv4 address of the router in this domain
+generated. The attribute 'ipv4' contains the current IPv4 address of the router
-suffixed by the length of the subnet prefix in bits. The 'gw' attribute
+in this domain suffixed by the length of the subnet prefix in bits. The 'gw'
-contains the IPv4 address of the gateway in this domain. Each <dns> subtag of a
+attribute contains the IPv4 address of the gateway in this domain. Each <dns>
-<domain> tag shows the IPv4 address of a DNS server known to this domain. The
+subtag of a <domain> tag shows the IPv4 address of a DNS server known to this
-<dns> subtags have the same order that the addresses had in the DHCP option 6
+domain. The <dns> subtags have the same order that the addresses had in the
-entry of the DHCP reply that the router received and that led to the current
+DHCP option 6 entry of the DHCP reply that the router received and that led to
-IPv4 configuration of the domain.
+the current IPv4 configuration of the domain. The <dns-domain> subtag of the
+<domain> tag states the DNS domain name of this domain if any.
 
 'config_triggers'
 

repos/os/src/server/nic_router/config.xsd

@@ -12,6 +12,12 @@
 		</xs:restriction>
 	</xs:simpleType><!-- Domain_name -->
 
+	<xs:simpleType name="Dns_domain_name">
+		<xs:restriction base="xs:string">
+			<xs:minLength value="1"/>
+		</xs:restriction>
+	</xs:simpleType><!-- Dns_domain_name -->
+
 	<xs:simpleType name="Icmp_type_3_code_attribute">
 		<xs:restriction base="xs:string">
 			<xs:enumeration value="no" />
@@ -140,6 +146,12 @@
 											</xs:complexType>
 										</xs:element><!-- dns-server -->
 
+										<xs:element name="dns-domain">
+											<xs:complexType>
+												<xs:attribute name="name" type="Dns_domain_name" />
+											</xs:complexType>
+										</xs:element><!-- dns-domain -->
+
 									</xs:choice>
 									<xs:attribute name="ip_first"          type="Ipv4_address" />
 									<xs:attribute name="ip_last"           type="Ipv4_address" />

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

@@ -16,6 +16,7 @@
 #include <interface.h>
 #include <domain.h>
 #include <configuration.h>
+#include <xml_node.h>
 
 using namespace Net;
 using namespace Genode;
@@ -42,6 +43,18 @@ Dhcp_server_base::Dhcp_server_base(Xml_node const &node,
 			_invalid(domain, "invalid DNS server entry");
 		}
 	});
+	node.with_sub_node("dns-domain", [&] (Xml_node const &sub_node) {
+		xml_node_with_attribute(sub_node, "name", [&] (Xml_attribute const &attr) {
+			_dns_domain_name.set_to(attr);
+
+			if (domain.config().verbose() &&
+			    !_dns_domain_name.valid()) {
+
+				log("[", domain, "] rejecting oversized DNS "
+				    "domain name from DHCP server configuration");
+			}
+		});
+	});
 }
 
 
@@ -108,6 +121,9 @@ void Dhcp_server::print(Output &output) const
 	_dns_servers.for_each([&] (Dns_server const &dns_server) {
 		Genode::print(output, "DNS server ", dns_server.ip(), ", ");
 	});
+	_dns_domain_name.with_string([&] (Dns_domain_name::String const &str) {
+		Genode::print(output, "DNS domain name ", str, ", ");
+	});
 	try { Genode::print(output, "DNS config from ", _dns_config_from(), ", "); }
 	catch (Pointer<Domain>::Invalid) { }
 
@@ -118,9 +134,11 @@ void Dhcp_server::print(Output &output) const
 }
 
 
-bool Dhcp_server::dns_servers_equal_to_those_of(Dhcp_server const &dhcp_server) const
+bool Dhcp_server::config_equal_to_that_of(Dhcp_server const &other) const
 {
-	return _dns_servers.equal_to(dhcp_server._dns_servers);
+	return _ip_lease_time.value == other._ip_lease_time.value &&
+	       _dns_servers.equal_to(other._dns_servers)          &&
+	       _dns_domain_name.equal_to(other._dns_domain_name);
 }
 
 
@@ -177,7 +195,9 @@ void Dhcp_server::free_ip(Domain       const &domain,
 Pointer<Domain> Dhcp_server::_init_dns_config_from(Genode::Xml_node const  node,
                                                    Domain_tree            &domains)
 {
-	if (!_dns_servers.empty()) {
+	if (!_dns_servers.empty() ||
+	    _dns_domain_name.valid()) {
+
 		return Pointer<Domain>();
 	}
 	Domain_name dns_config_from =

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

@@ -18,7 +18,7 @@
 #include <bit_allocator_dynamic.h>
 #include <list.h>
 #include <pointer.h>
-#include <dns_server.h>
+#include <dns.h>
 #include <ipv4_config.h>
 
 /* Genode includes */
@@ -47,8 +47,9 @@ class Net::Dhcp_server_base
 {
 	protected:
 
-		Genode::Allocator     &_alloc;
+		Genode::Allocator &_alloc;
-		Net::List<Dns_server>  _dns_servers { };
+		Dns_server_list    _dns_servers     { };
+		Dns_domain_name    _dns_domain_name { _alloc };
 
 		void _invalid(Domain const &domain,
 		              char   const *reason);
@@ -123,8 +124,15 @@ class Net::Dhcp_server : private Genode::Noncopyable,
 			}
 		}
 
-		bool
+		Dns_domain_name const &dns_domain_name() const
-		dns_servers_equal_to_those_of(Dhcp_server const &dhcp_server) const;
+		{
+			if (_dns_config_from.valid()) {
+				return _resolve_dns_config_from().dns_domain_name();
+			}
+			return _dns_domain_name;
+		}
+
+		bool config_equal_to_that_of(Dhcp_server const &dhcp_server) const;
 
 
 		/*********

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

@@ -0,0 +1,128 @@
+/*
+ * \brief  Utilities for handling DNS configurations
+ * \author Martin Stein
+ * \date   2020-11-17
+ */
+
+/*
+ * Copyright (C) 2020 Genode Labs GmbH
+ *
+ * This file is part of the Genode OS framework, which is distributed
+ * under the terms of the GNU Affero General Public License version 3.
+ */
+
+/* local includes */
+#include <dns.h>
+#include <domain.h>
+#include <configuration.h>
+
+/* Genode includes */
+#include <util/xml_node.h>
+
+using namespace Net;
+using namespace Genode;
+
+
+/****************
+ ** Dns_server **
+ ****************/
+
+Dns_server::Dns_server(Ipv4_address const &ip)
+:
+	_ip { ip }
+{
+	if (!_ip.valid()) {
+		throw Invalid { };
+	}
+}
+
+
+bool Dns_server::equal_to(Dns_server const &server) const
+{
+	return _ip == server._ip;
+}
+
+
+/*********************
+ ** Dns_domain_name **
+ *********************/
+
+void Dns_domain_name::set_to(Dns_domain_name const &name)
+{
+	if (name.valid()) {
+		name.with_string([&] (String const &string) {
+			if (_string.valid()) {
+				_string() = string;
+			} else {
+				_string = *new (_alloc) String { string };
+			}
+		});
+	} else {
+		set_invalid();
+	}
+}
+
+
+void Dns_domain_name::set_to(Xml_attribute const &name_attr)
+{
+	name_attr.with_raw_value([&] (char const *base, size_t size) {
+		if (size < STRING_CAPACITY) {
+			if (_string.valid()) {
+				_string() = Cstring { base, size };
+			} else {
+				_string = *new (_alloc) String { Cstring { base, size } };
+			}
+		} else {
+			set_invalid();
+		}
+	});
+}
+
+
+void Dns_domain_name::set_to(Dhcp_packet::Domain_name const &name_option)
+{
+	name_option.with_string([&] (char const *base, size_t size) {
+		if (size < STRING_CAPACITY) {
+			if (_string.valid()) {
+				_string() = Cstring { base, size };
+			} else {
+				_string = *new (_alloc) String { Cstring { base, size } };
+			}
+		} else {
+			set_invalid();
+		}
+	});
+}
+
+
+void Dns_domain_name::set_invalid()
+{
+	if (_string.valid()) {
+		_alloc.free(&_string(), sizeof(String));
+		_string = { };
+	}
+}
+
+
+bool Dns_domain_name::equal_to(Dns_domain_name const &other) const
+{
+	if (_string.valid()) {
+		if (other._string.valid()) {
+			return _string() == other._string();
+		}
+		return false;
+	}
+	return !other._string.valid();
+}
+
+
+Dns_domain_name::Dns_domain_name(Genode::Allocator &alloc)
+:
+	_alloc { alloc }
+{ }
+
+
+Dns_domain_name::~Dns_domain_name()
+{
+	set_invalid();
+}

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

@@ -0,0 +1,104 @@
+/*
+ * \brief  Utilities for handling DNS configurations
+ * \author Martin Stein
+ * \date   2020-11-17
+ */
+
+/*
+ * Copyright (C) 2020 Genode Labs GmbH
+ *
+ * This file is part of the Genode OS framework, which is distributed
+ * under the terms of the GNU Affero General Public License version 3.
+ */
+
+#ifndef _DNS_H_
+#define _DNS_H_
+
+/* local includes */
+#include <list.h>
+#include <pointer.h>
+
+/* Genode includes */
+#include <util/reconstructible.h>
+#include <net/ipv4.h>
+#include <net/dhcp.h>
+
+namespace Genode {
+
+	class Xml_attribute;
+}
+
+namespace Net {
+
+	class Dns_server;
+	class Dns_domain_name;
+
+	using Dns_server_list = Net::List<Dns_server>;
+}
+
+class Net::Dns_server : private Genode::Noncopyable,
+                        public  Net::List<Dns_server>::Element
+{
+	private:
+
+		Net::Ipv4_address const _ip;
+
+	public:
+
+		struct Invalid : Genode::Exception { };
+
+		Dns_server(Net::Ipv4_address const &ip);
+
+		bool equal_to(Dns_server const &server) const;
+
+
+		/***************
+		 ** Accessors **
+		 ***************/
+
+		Net::Ipv4_address const &ip() const { return _ip; }
+};
+
+class Net::Dns_domain_name : private Genode::Noncopyable
+{
+	private:
+
+		enum { STRING_CAPACITY = 160 };
+
+	public:
+
+		using String = Genode::String<STRING_CAPACITY>;
+
+	private:
+
+		Genode::Allocator &_alloc;
+		Pointer<String>    _string { };
+
+	public:
+
+		Dns_domain_name(Genode::Allocator &alloc);
+
+		~Dns_domain_name();
+
+		void set_to(Dns_domain_name const &name);
+
+		void set_to(Genode::Xml_attribute const &name_attr);
+
+		void set_to(Dhcp_packet::Domain_name const &name_option);
+
+		void set_invalid();
+
+		bool valid() const { return _string.valid(); }
+
+		template <typename FUNC>
+		void with_string(FUNC && func) const
+		{
+			if (_string.valid()) {
+				func(_string());
+			}
+		}
+
+		bool equal_to(Dns_domain_name const &other) const;
+};
+
+#endif /* _DNS_H_ */

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

@@ -1,34 +0,0 @@
-/*
- * \brief  DNS server entry of a DHCP server or IPv4 config
- * \author Martin Stein
- * \date   2020-11-17
- */
-
-/*
- * Copyright (C) 2020 Genode Labs GmbH
- *
- * This file is part of the Genode OS framework, which is distributed
- * under the terms of the GNU Affero General Public License version 3.
- */
-
-/* local includes */
-#include <dns_server.h>
-
-using namespace Net;
-using namespace Genode;
-
-
-Net::Dns_server::Dns_server(Ipv4_address const &ip)
-:
-	_ip { ip }
-{
-	if (!_ip.valid()) {
-		throw Invalid { };
-	}
-}
-
-
-bool Net::Dns_server::equal_to(Dns_server const &server) const
-{
-	return _ip == server._ip;
-}

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

@@ -1,50 +0,0 @@
-/*
- * \brief  DNS server entry of a DHCP server or IPv4 config
- * \author Martin Stein
- * \date   2020-11-17
- */
-
-/*
- * Copyright (C) 2020 Genode Labs GmbH
- *
- * This file is part of the Genode OS framework, which is distributed
- * under the terms of the GNU Affero General Public License version 3.
- */
-
-#ifndef _DNS_SERVER_H_
-#define _DNS_SERVER_H_
-
-/* local includes */
-#include <list.h>
-
-/* Genode includes */
-#include <net/ipv4.h>
-
-namespace Net { class Dns_server; }
-
-class Net::Dns_server : private Genode::Noncopyable,
-                        public  Net::List<Dns_server>::Element
-{
-	private:
-
-		Net::Ipv4_address const _ip;
-
-	public:
-
-		struct Invalid : Genode::Exception { };
-
-		Dns_server(Net::Ipv4_address const &ip);
-
-		bool equal_to(Dns_server const &server) const;
-
-
-		/***************
-		 ** Accessors **
-		 ***************/
-
-		Net::Ipv4_address const &ip() const { return _ip; }
-};
-
-
-
-#endif /* _DHCP_SERVER_H_ */

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

@@ -113,7 +113,7 @@ void Domain::discard_ip_config()
 void Domain::ip_config_from_dhcp_ack(Dhcp_packet &dhcp_ack)
 {
 	_reconstruct_ip_config([&] (Reconstructible<Ipv4_config> &ip_config) {
-		ip_config.construct(dhcp_ack, _alloc); });
+		ip_config.construct(dhcp_ack, _alloc, *this); });
 }
 
 
@@ -397,6 +397,13 @@ void Domain::report(Xml_generator &xml)
 					xml.attribute("ip", String<16>(dns_server.ip()));
 				});
 			});
+			ip_config().dns_domain_name().with_string(
+				[&] (Dns_domain_name::String const &str)
+			{
+				xml.node("dns-domain", [&] () {
+					xml.attribute("name", str);
+				});
+			});
 			empty = false;
 		}
 		if (_config.report().stats()) {

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

@@ -678,6 +678,11 @@ void Interface::_send_dhcp_reply(Dhcp_server               const &dhcp_srv,
 				data.append_address(addr);
 			});
 		});
+		dhcp_srv.dns_domain_name().with_string(
+			[&] (Dns_domain_name::String const &str)
+		{
+			dhcp_opts.append_domain_name(str.string(), str.length());
+		});
 		dhcp_opts.append_option<Dhcp_packet::Broadcast_addr>(local_intf.broadcast_address());
 		dhcp_opts.append_option<Dhcp_packet::Options_end>();
 
@@ -1908,12 +1913,7 @@ void Interface::_update_dhcp_allocations(Domain &old_domain,
 	try {
 		Dhcp_server &old_dhcp_srv = old_domain.dhcp_server();
 		Dhcp_server &new_dhcp_srv = new_domain.dhcp_server();
-		if (!old_dhcp_srv.dns_servers_equal_to_those_of(new_dhcp_srv)) {
+		if (!old_dhcp_srv.config_equal_to_that_of(new_dhcp_srv)) {
-			throw Pointer<Dhcp_server>::Invalid();
-		}
-		if (old_dhcp_srv.ip_lease_time().value !=
-		    new_dhcp_srv.ip_lease_time().value)
-		{
 			throw Pointer<Dhcp_server>::Invalid();
 		}
 		_dhcp_allocations.for_each([&] (Dhcp_allocation &allocation) {

repos/os/src/server/nic_router/ipv4_config.cc

@@ -16,6 +16,8 @@
 
 /* local includes */
 #include <ipv4_config.h>
+#include <domain.h>
+#include <configuration.h>
 
 using namespace Genode;
 using namespace Net;
@@ -45,22 +47,23 @@ Ipv4_config::Ipv4_config(Ipv4_config const &ip_config,
 	_interface  { ip_config._interface },
 	_gateway    { ip_config._gateway }
 {
-	ip_config._dns_servers.for_each([&] (Dns_server const &dns_server) {
+	ip_config.for_each_dns_server([&] (Dns_server const &dns_server) {
 		_dns_servers.insert_as_tail(
 			*new (alloc) Dns_server(dns_server.ip()));
 	});
+	_dns_domain_name.set_to(ip_config.dns_domain_name());
 }
 
 
-Ipv4_config::Ipv4_config(Dhcp_packet &dhcp_ack,
+Ipv4_config::Ipv4_config(Dhcp_packet  &dhcp_ack,
-                         Allocator   &alloc)
+                         Allocator    &alloc,
+                         Domain const &domain)
 :
 	_alloc      { alloc },
 	_interface  { dhcp_ack.yiaddr(),
 	              dhcp_ipv4_option<Dhcp_packet::Subnet_mask>(dhcp_ack) },
 	_gateway    { dhcp_ipv4_option<Dhcp_packet::Router_ipv4>(dhcp_ack) }
 {
-
 	try {
 		Dhcp_packet::Dns_server const &dns_server {
 			dhcp_ack.option<Dhcp_packet::Dns_server>() };
@@ -70,6 +73,17 @@ Ipv4_config::Ipv4_config(Dhcp_packet &dhcp_ack,
 		});
 	}
 	catch (Dhcp_packet::Option_not_found) { }
+	try {
+		_dns_domain_name.set_to(dhcp_ack.option<Dhcp_packet::Domain_name>());
+
+		if (domain.config().verbose() &&
+		    !_dns_domain_name.valid()) {
+
+			log("[", domain, "] rejecting oversized DNS "
+			    "domain name from DHCP reply");
+		}
+	}
+	catch (Dhcp_packet::Option_not_found) { }
 }
 
 

repos/os/src/server/nic_router/ipv4_config.h

@@ -17,12 +17,16 @@
 /* local includes */
 #include <ipv4_address_prefix.h>
 #include <dhcp.h>
-#include <dns_server.h>
+#include <dns.h>
 
 /* Genode includes */
 #include <util/xml_node.h>
 
-namespace Net { class Ipv4_config; }
+namespace Net {
+
+	class Domain;
+	class Ipv4_config;
+}
 
 class Net::Ipv4_config
 {
@@ -36,7 +40,8 @@ class Net::Ipv4_config
 		bool                  const  _point_to_point  { _gateway_valid &&
 		                                               _interface_valid &&
 		                                               _interface.prefix == 32 };
-		Net::List<Dns_server>        _dns_servers     { };
+		Dns_server_list              _dns_servers     { };
+		Dns_domain_name              _dns_domain_name { _alloc };
 		bool                  const  _valid           { _point_to_point ||
 		                                               (_interface_valid &&
 		                                                (!_gateway_valid ||
@@ -45,7 +50,8 @@ class Net::Ipv4_config
 	public:
 
 		Ipv4_config(Net::Dhcp_packet  &dhcp_ack,
-		            Genode::Allocator &alloc);
+		            Genode::Allocator &alloc,
+		            Domain      const &domain);
 
 		Ipv4_config(Genode::Xml_node const &domain_node,
 		            Genode::Allocator      &alloc);
@@ -59,16 +65,17 @@ class Net::Ipv4_config
 
 		bool operator != (Ipv4_config const &other) const
 		{
-			return _interface  != other._interface ||
+			return _interface != other._interface             ||
-			       _gateway    != other._gateway ||
+			       _gateway   != other._gateway               ||
-			       !_dns_servers.equal_to(other._dns_servers);
+			       !_dns_servers.equal_to(other._dns_servers) ||
+			       !_dns_domain_name.equal_to(other._dns_domain_name);
 		}
 
 		template <typename FUNC>
-		void for_each_dns_server(FUNC && functor) const
+		void for_each_dns_server(FUNC && func) const
 		{
 			_dns_servers.for_each([&] (Dns_server const &dns_server) {
-				functor(dns_server);
+				func(dns_server);
 			});
 		}
 
@@ -84,10 +91,11 @@ class Net::Ipv4_config
 		 ** Accessors **
 		 ***************/
 
-		bool                       valid()         const { return _valid; }
+		bool                       valid()           const { return _valid; }
-		Ipv4_address_prefix const &interface()     const { return _interface; }
+		Ipv4_address_prefix const &interface()       const { return _interface; }
-		Ipv4_address        const &gateway()       const { return _gateway; }
+		Ipv4_address        const &gateway()         const { return _gateway; }
-		bool                       gateway_valid() const { return _gateway_valid; }
+		bool                       gateway_valid()   const { return _gateway_valid; }
+		Dns_domain_name     const &dns_domain_name() const { return _dns_domain_name; }
 };
 
 #endif /* _IPV4_CONFIG_H_ */

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

@@ -73,6 +73,8 @@ class Net::Const_pointer
 
 			return *_obj;
 		}
+
+		bool valid() const { return _obj != nullptr; }
 };
 
 #endif /* _POINTER_H_ */

repos/os/src/server/nic_router/target.mk

@@ -22,7 +22,7 @@ SRC_CC += \
 	link.cc \
 	transport_rule.cc \
 	permit_rule.cc \
-	dns_server.cc \
+	dns.cc \
 	dhcp_client.cc \
 	dhcp_server.cc \
 	report.cc \
@@ -30,7 +30,6 @@ SRC_CC += \
 	uplink_session_root.cc \
 	communication_buffer.cc \
 
-
 INC_DIR += $(PRG_DIR)
 
 CONFIG_XSD = config.xsd

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

@@ -24,6 +24,16 @@ namespace Genode {
 	Microseconds read_sec_attr(Xml_node const  node,
 	                           char     const *name,
 	                           uint64_t const  default_sec);
+
+	template <typename FUNC>
+	void xml_node_with_attribute(Xml_node const  node,
+	                             char     const *name,
+	                             FUNC        &&  func)
+	{
+		if (node.has_attribute(name)) {
+			func(node.attribute(name));
+		}
+	}
 }
 
 #endif /* _XML_NODE_H_ */

repos/os/src/test/nic_router_dhcp/client/dhcp_client.cc

@@ -185,6 +185,15 @@ void Dhcp_client::_handle_dhcp_reply(Dhcp_packet &dhcp)
 				});
 			}
 			catch (Dhcp_packet::Option_not_found) { }
+			try {
+				Dhcp_packet::Domain_name const &domain_name {
+					dhcp.option<Dhcp_packet::Domain_name>() };
+
+				domain_name.with_string([&] (char const *base, size_t size) {
+					log("  DNS domain name: ", Cstring { base, size });
+				});
+			}
+			catch (Dhcp_packet::Option_not_found) { }
 
 			Ipv4_config ip_config(
 				Ipv4_address_prefix(

repos/os/src/test/nic_router_dhcp/manager/dns_server.cc

@@ -1,34 +0,0 @@
-/*
- * \brief  DNS server entry of a DHCP server or IPv4 config
- * \author Martin Stein
- * \date   2020-11-17
- */
-
-/*
- * Copyright (C) 2020 Genode Labs GmbH
- *
- * This file is part of the Genode OS framework, which is distributed
- * under the terms of the GNU Affero General Public License version 3.
- */
-
-/* local includes */
-#include <dns_server.h>
-
-using namespace Net;
-using namespace Genode;
-
-
-Local::Dns_server::Dns_server(Ipv4_address const &ip)
-:
-	_ip { ip }
-{
-	if (!_ip.valid()) {
-		throw Invalid { };
-	}
-}
-
-
-bool Local::Dns_server::equal_to(Dns_server const &server) const
-{
-	return _ip == server._ip;
-}

repos/os/src/test/nic_router_dhcp/manager/dns_server.h

@@ -1,50 +0,0 @@
-/*
- * \brief  DNS server entry of a DHCP server or IPv4 config
- * \author Martin Stein
- * \date   2020-11-17
- */
-
-/*
- * Copyright (C) 2020 Genode Labs GmbH
- *
- * This file is part of the Genode OS framework, which is distributed
- * under the terms of the GNU Affero General Public License version 3.
- */
-
-#ifndef _DNS_SERVER_H_
-#define _DNS_SERVER_H_
-
-/* local includes */
-#include <list.h>
-
-/* Genode includes */
-#include <net/ipv4.h>
-
-namespace Local { class Dns_server; }
-
-class Local::Dns_server : private Genode::Noncopyable,
-                          public  Local::List<Dns_server>::Element
-{
-	private:
-
-		Net::Ipv4_address const _ip;
-
-	public:
-
-		struct Invalid : Genode::Exception { };
-
-		Dns_server(Net::Ipv4_address const &ip);
-
-		bool equal_to(Dns_server const &server) const;
-
-
-		/***************
-		 ** Accessors **
-		 ***************/
-
-		Net::Ipv4_address const &ip() const { return _ip; }
-};
-
-
-
-#endif /* _DHCP_SERVER_H_ */

repos/os/src/test/nic_router_dhcp/manager/list.h

@@ -1,102 +0,0 @@
-/*
- * \brief  Genode list with additional functions needed by NIC router
- * \author Martin Stein
- * \date   2016-08-19
- */
-
-/*
- * Copyright (C) 2016-2017 Genode Labs GmbH
- *
- * This file is part of the Genode OS framework, which is distributed
- * under the terms of the GNU Affero General Public License version 3.
- */
-
-#ifndef _LIST_H_
-#define _LIST_H_
-
-/* Genode includes */
-#include <util/list.h>
-#include <base/allocator.h>
-
-namespace Local { template <typename> class List; }
-
-
-template <typename LT>
-struct Local::List : Genode::List<LT>
-{
-	using Base = Genode::List<LT>;
-
-	template <typename FUNC>
-	void for_each(FUNC && functor)
-	{
-		for (LT *elem = Base::first(); elem; )
-		{
-			LT *const next = elem->Base::Element::next();
-			functor(*elem);
-			elem = next;
-		}
-	}
-
-	template <typename FUNC>
-	void for_each(FUNC && functor) const
-	{
-		for (LT const *elem = Base::first(); elem; )
-		{
-			LT const *const next = elem->Base::Element::next();
-			functor(*elem);
-			elem = next;
-		}
-	}
-
-	void destroy_each(Genode::Deallocator &dealloc)
-	{
-		while (LT *elem = Base::first()) {
-			Base::remove(elem);
-			destroy(dealloc, elem);
-		}
-	}
-
-	bool empty() const
-	{
-		return Base::first() == nullptr;
-	}
-
-	void insert_as_tail(LT const &le)
-	{
-		LT *elem { Base::first() };
-		if (elem) {
-			while (elem->Base::Element::next()) {
-				elem = elem->Base::Element::next();
-			}
-		}
-		Base::insert(&le, elem);
-	}
-
-	bool equal_to(List<LT> const &list) const
-	{
-		LT const *curr_elem_1 { Base::first() };
-		LT const *curr_elem_2 { list.Base::first() };
-		while (true) {
-
-			if (curr_elem_1 == nullptr) {
-				return curr_elem_2 == nullptr;
-			}
-			if (curr_elem_2 == nullptr) {
-				return false;
-			}
-			LT const *const next_elem_1 {
-				curr_elem_1->List<LT>::Element::next() };
-
-			LT const *const next_elem_2 {
-				curr_elem_2->List<LT>::Element::next() };
-
-			if (!curr_elem_1->equal_to(*curr_elem_2)) {
-				return false;
-			}
-			curr_elem_1 = next_elem_1;
-			curr_elem_2 = next_elem_2;
-		}
-	}
-};
-
-#endif /* _LIST_H_ */

repos/os/src/test/nic_router_dhcp/manager/main.cc

@@ -20,7 +20,10 @@
 
 /* local includes */
 #include <ipv4_address_prefix.h>
-#include <dns_server.h>
+
+/* NIC router includes */
+#include <dns.h>
+#include <xml_node.h>
 
 using namespace Net;
 using namespace Genode;
@@ -39,7 +42,8 @@ class Local::Main
 		Signal_handler<Main>    _router_state_handler   { _env.ep(), *this, &Main::_handle_router_state };
 		Expanding_reporter      _router_config_reporter { _env, "config",  "router_config" };
 		bool                    _router_config_outdated { true };
-		Local::List<Dns_server> _dns_servers            { };
+		Dns_server_list         _dns_servers            { };
+		Dns_domain_name         _dns_domain_name        { _heap };
 
 		void _handle_router_state();
 
@@ -99,7 +103,7 @@ void Local::Main::_handle_router_state()
 			 * Read out all DNS servers from the new uplink state
 			 * and memorize them in a function-local list.
 			 */
-			Local::List<Dns_server> dns_servers { };
+			Dns_server_list dns_servers { };
 			domain_node.for_each_sub_node(
 				"dns",
 				[&] (Xml_node const &dns_node)
@@ -110,8 +114,8 @@ void Local::Main::_handle_router_state()
 			});
 
 			/*
-			 * If the new list of DNS servers differs our member list,
+			 * If the new list of DNS servers differs from the stored list,
-			 * update the member list, and remember to write out a new router
+			 * update the stored list, and remember to write out a new router
 			 * configuration.
 			 */
 			if (!_dns_servers.equal_to(dns_servers)) {
@@ -124,6 +128,19 @@ void Local::Main::_handle_router_state()
 				_router_config_outdated = true;
 			}
 			dns_servers.destroy_each(_heap);
+
+			/* read out new DNS domain name */
+			Dns_domain_name dns_domain_name { _heap };
+			domain_node.with_sub_node("dns-domain", [&] (Xml_node const &sub_node) {
+				xml_node_with_attribute(sub_node, "name", [&] (Xml_attribute const &attr) {
+					dns_domain_name.set_to(attr);
+				});
+			});
+			/* update stored DNS domain name if necessary */
+			if (!_dns_domain_name.equal_to(dns_domain_name)) {
+				_dns_domain_name.set_to(dns_domain_name);
+				_router_config_outdated = true;
+			}
 		}
 	});
 
@@ -164,6 +181,13 @@ void Local::Main::_handle_router_state()
 							xml.attribute("ip", String<16>(dns_server.ip()));
 						});
 					});
+					_dns_domain_name.with_string(
+						[&] (Dns_domain_name::String const &str)
+					{
+						xml.node("dns-domain", [&] () {
+							xml.attribute("name", str);
+						});
+					});
 				});
 			});
 		});

repos/os/src/test/nic_router_dhcp/manager/target.mk

@@ -2,6 +2,9 @@ TARGET = test-nic_router_dhcp-manager
 
 LIBS += base
 
-SRC_CC += main.cc ipv4_address_prefix.cc dns_server.cc
+SRC_CC += main.cc ipv4_address_prefix.cc dns.cc xml_node.cc
 
-INC_DIR += $(PRG_DIR)
+INC_DIR += $(PRG_DIR) $(REP_DIR)/src/server/nic_router
+
+vpath dns.cc      $(REP_DIR)/src/server/nic_router
+vpath xml_node.cc $(REP_DIR)/src/server/nic_router