#1752 - Moved dns_server ip address from the NIC to the Node. Updated the arcd_uc2_network so that clients and servers have a dns server. Added sys_log entries for DNSServer and DNSClient. MAde the DNSServer always rend a reply, but for the resolved IP address to be empty if it cannot be resolved.

docs/source/simulation_components/system/dns_client_server.rst

@@ -3,10 +3,10 @@
     © Crown-owned copyright 2023, Defence Science and Technology Laboratory UK
 
 DNS Client Server
-======================
+=================
 
 DNS Server
-----------------
+----------
 Also known as a DNS Resolver, the ``DNSServer`` provides a DNS Server simulation by extending the base Service class.
 
 Key capabilities
@@ -29,7 +29,7 @@ Implementation
 - Extends Service class for integration with ``SoftwareManager``.
 
 DNS Client
----------------
+----------
 
 The DNSClient provides a client interface for connecting to the ``DNSServer``.
 
@@ -45,7 +45,7 @@ Usage
 
 - Install on a Node via the ``SoftwareManager`` to start the database service.
 - Service runs on TCP port 53 by default. (TODO: TCP for now, should be UDP in future)
-- Execute domain name checks with ``check_domain_exists``, providing a ``DNSServer`` ``IPv4Address``.
+- Execute domain name checks with ``check_domain_exists``.
 - ``DNSClient`` will automatically add the IP Address of the domain into its cache
 
 Implementation

src/primaite/simulator/network/hardware/base.py

@@ -5,7 +5,7 @@ import secrets
 from enum import Enum
 from ipaddress import IPv4Address, IPv4Network
 from pathlib import Path
-from typing import Any, Dict, List, Literal, Optional, Tuple, Union
+from typing import Any, Dict, Literal, Optional, Tuple, Union
 
 from prettytable import MARKDOWN, PrettyTable
 
@@ -89,8 +89,6 @@ class NIC(SimComponent):
     "The Maximum Transmission Unit (MTU) of the NIC in Bytes. Default is 1500 B"
     wake_on_lan: bool = False
     "Indicates if the NIC supports Wake-on-LAN functionality."
-    dns_servers: List[IPv4Address] = []
-    "List of IP addresses of DNS servers used for name resolution."
     connected_node: Optional[Node] = None
     "The Node to which the NIC is connected."
     connected_link: Optional[Link] = None
@@ -882,6 +880,8 @@ class Node(SimComponent):
     "The NICs on the node."
     ethernet_port: Dict[int, NIC] = {}
     "The NICs on the node by port id."
+    dns_server: Optional[IPv4Address] = None
+    "List of IP addresses of DNS servers used for name resolution."
 
     accounts: Dict[str, Account] = {}
     "All accounts on the node."
@@ -931,6 +931,7 @@ class Node(SimComponent):
                 sys_log=kwargs.get("sys_log"),
                 session_manager=kwargs.get("session_manager"),
                 file_system=kwargs.get("file_system"),
+                dns_server=kwargs.get("dns_server"),
             )
         super().__init__(**kwargs)
         self.arp.nics = self.nics

src/primaite/simulator/network/networks.py

@@ -128,7 +128,11 @@ def arcd_uc2_network() -> Network:
 
     # Client 1
     client_1 = Computer(
-        hostname="client_1", ip_address="192.168.10.21", subnet_mask="255.255.255.0", default_gateway="192.168.10.1"
+        hostname="client_1",
+        ip_address="192.168.10.21",
+        subnet_mask="255.255.255.0",
+        default_gateway="192.168.10.1",
+        dns_server=IPv4Address("192.168.1.10"),
     )
     client_1.power_on()
     client_1.software_manager.install(DNSClient)
@@ -141,7 +145,11 @@ def arcd_uc2_network() -> Network:
 
     # Client 2
     client_2 = Computer(
-        hostname="client_2", ip_address="192.168.10.22", subnet_mask="255.255.255.0", default_gateway="192.168.10.1"
+        hostname="client_2",
+        ip_address="192.168.10.22",
+        subnet_mask="255.255.255.0",
+        default_gateway="192.168.10.1",
+        dns_server=IPv4Address("192.168.1.10"),
     )
     client_2.power_on()
     client_2.software_manager.install(DNSClient)
@@ -167,6 +175,7 @@ def arcd_uc2_network() -> Network:
         ip_address="192.168.1.14",
         subnet_mask="255.255.255.0",
         default_gateway="192.168.1.1",
+        dns_server=IPv4Address("192.168.1.10"),
     )
     database_server.power_on()
     network.connect(endpoint_b=database_server.ethernet_port[1], endpoint_a=switch_1.switch_ports[3])
@@ -206,7 +215,11 @@ def arcd_uc2_network() -> Network:
 
     # Web Server
     web_server = Server(
-        hostname="web_server", ip_address="192.168.1.12", subnet_mask="255.255.255.0", default_gateway="192.168.1.1"
+        hostname="web_server",
+        ip_address="192.168.1.12",
+        subnet_mask="255.255.255.0",
+        default_gateway="192.168.1.1",
+        dns_server=IPv4Address("192.168.1.10"),
     )
     web_server.power_on()
     web_server.software_manager.install(DatabaseClient)
@@ -224,7 +237,11 @@ def arcd_uc2_network() -> Network:
 
     # Backup Server
     backup_server = Server(
-        hostname="backup_server", ip_address="192.168.1.16", subnet_mask="255.255.255.0", default_gateway="192.168.1.1"
+        hostname="backup_server",
+        ip_address="192.168.1.16",
+        subnet_mask="255.255.255.0",
+        default_gateway="192.168.1.1",
+        dns_server=IPv4Address("192.168.1.10"),
     )
     backup_server.power_on()
     network.connect(endpoint_b=backup_server.ethernet_port[1], endpoint_a=switch_1.switch_ports[4])
@@ -235,6 +252,7 @@ def arcd_uc2_network() -> Network:
         ip_address="192.168.1.110",
         subnet_mask="255.255.255.0",
         default_gateway="192.168.1.1",
+        dns_server=IPv4Address("192.168.1.10"),
     )
     security_suite.power_on()
     network.connect(endpoint_b=security_suite.ethernet_port[1], endpoint_a=switch_1.switch_ports[7])

src/primaite/simulator/network/protocols/dns.py

@@ -22,7 +22,7 @@ class DNSReply(BaseModel):
     :param domain_name_ip_address: IP Address of the Domain Name requested.
     """
 
-    domain_name_ip_address: IPv4Address
+    domain_name_ip_address: Optional[IPv4Address] = None
     "IP Address of the Domain Name requested."
 
 
@@ -56,7 +56,6 @@ class DNSPacket(BaseModel):
         :param domain_ip_address: The IP address that was being sought after from the original target domain name.
         :return: A new instance of DNSPacket.
         """
-        if domain_ip_address is not None:
+        self.dns_reply = DNSReply(domain_name_ip_address=domain_ip_address)
-            self.dns_reply = DNSReply(domain_name_ip_address=IPv4Address(domain_ip_address))
 
         return self

src/primaite/simulator/system/core/software_manager.py

@@ -23,7 +23,13 @@ IOSoftwareClass = TypeVar("IOSoftwareClass", bound=IOSoftware)
 class SoftwareManager:
     """A class that manages all running Services and Applications on a Node and facilitates their communication."""
 
-    def __init__(self, session_manager: "SessionManager", sys_log: SysLog, file_system: FileSystem):
+    def __init__(
+        self,
+        session_manager: "SessionManager",
+        sys_log: SysLog,
+        file_system: FileSystem,
+        dns_server: Optional[IPv4Address],
+    ):
         """
         Initialize a new instance of SoftwareManager.
 
@@ -35,6 +41,7 @@ class SoftwareManager:
         self.port_protocol_mapping: Dict[Tuple[Port, IPProtocol], Union[Service, Application]] = {}
         self.sys_log: SysLog = sys_log
         self.file_system: FileSystem = file_system
+        self.dns_server: Optional[IPv4Address] = dns_server
 
     def get_open_ports(self) -> List[Port]:
         """
@@ -58,7 +65,9 @@ class SoftwareManager:
         if software_class in self._software_class_to_name_map:
             self.sys_log.info(f"Cannot install {software_class} as it is already installed")
             return
-        software = software_class(software_manager=self, sys_log=self.sys_log, file_system=self.file_system)
+        software = software_class(
+            software_manager=self, sys_log=self.sys_log, file_system=self.file_system, dns_server=self.dns_server
+        )
         if isinstance(software, Application):
             software.install()
         software.software_manager = self

src/primaite/simulator/system/services/dns_client.py

@@ -16,6 +16,8 @@ class DNSClient(Service):
 
     dns_cache: Dict[str, IPv4Address] = {}
     "A dict of known mappings between domain/URLs names and IPv4 addresses."
+    dns_server: Optional[IPv4Address] = None
+    "The DNS Server the client sends requests to."
 
     def __init__(self, **kwargs):
         kwargs["name"] = "DNSClient"
@@ -60,16 +62,12 @@ class DNSClient(Service):
     def check_domain_exists(
         self,
         target_domain: str,
-        dest_ip_address: Optional[IPv4Address] = None,
-        dest_port: Optional[Port] = Port.DNS,
         session_id: Optional[str] = None,
         is_reattempt: bool = False,
     ) -> bool:
         """Function to check if domain name exists.
 
         :param: target_domain: The domain requested for an IP address.
-        :param: dest_ip_address: The ip address of the DNS Server used for domain lookup.
-        :param: dest_port: The port on the DNS Server which accepts domain lookup requests. Default is Port.DNS.
         :param: session_id: The Session ID the payload is to originate from. Optional.
         :param: is_reattempt: Checks if the request has been reattempted. Default is False.
         """
@@ -78,30 +76,28 @@ class DNSClient(Service):
 
         # check if the domain is already in the DNS cache
         if target_domain in self.dns_cache:
+            self.sys_log.info(
+                f"DNS Client: Domain lookup for {target_domain} successful, resolves to {self.dns_cache[target_domain]}"
+            )
             return True
         else:
             # return False if already reattempted
             if is_reattempt:
+                self.sys_log.info(f"DNS Client: Domain lookup for {target_domain} failed")
                 return False
             else:
                 # send a request to check if domain name exists in the DNS Server
                 software_manager: SoftwareManager = self.software_manager
                 software_manager.send_payload_to_session_manager(
-                    payload=payload,
+                    payload=payload, dest_ip_address=self.dns_server, dest_port=Port.DNS
-                    dest_ip_address=dest_ip_address,
-                    dest_port=dest_port,
                 )
 
-                # check if the domain has been added to cache
+                # recursively re-call the function passing is_reattempt=True
-                if self.dns_cache.get(target_domain, None) is None:
+                return self.check_domain_exists(
-                    # call function again
+                    target_domain=target_domain,
-                    return self.check_domain_exists(
+                    session_id=session_id,
-                        target_domain=target_domain,
+                    is_reattempt=True,
-                        dest_ip_address=dest_ip_address,
+                )
-                        dest_port=dest_port,
-                        session_id=session_id,
-                        is_reattempt=True,
-                    )
 
     def send(
         self,
@@ -125,6 +121,7 @@ class DNSClient(Service):
         # create DNS request packet
         software_manager: SoftwareManager = self.software_manager
         software_manager.send_payload_to_session_manager(payload=payload, session_id=session_id)
+        return True
 
     def receive(
         self,
@@ -150,7 +147,8 @@ class DNSClient(Service):
         payload: DNSPacket = payload
         if payload.dns_reply is not None:
             # add the IP address to the client cache
-            self.dns_cache[payload.dns_request.domain_name_request] = payload.dns_reply.domain_name_ip_address
+            if payload.dns_reply.domain_name_ip_address:
-            return True
+                self.dns_cache[payload.dns_request.domain_name_request] = payload.dns_reply.domain_name_ip_address
+                return True
 
         return False

src/primaite/simulator/system/services/dns_server.py

@@ -47,10 +47,7 @@ class DNSServer(Service):
         :param target_domain: The single domain name requested by a DNS client.
         :return ip_address: The IP address of that domain name or None.
         """
-        if target_domain in self.dns_table:
+        return self.dns_table.get(target_domain)
-            return self.dns_table[target_domain]
-        else:
-            return None
 
     def dns_register(self, domain_name: str, domain_ip_address: IPv4Address):
         """
@@ -97,11 +94,19 @@ class DNSServer(Service):
         # cast payload into a DNS packet
         payload: DNSPacket = payload
         if payload.dns_request is not None:
+            self.sys_log.info(
+                f"DNS Server: Received domain lookup request for {payload.dns_request.domain_name_request} "
+                f"from session {session_id}"
+            )
             # generate a reply with the correct DNS IP address
             payload = payload.generate_reply(self.dns_lookup(payload.dns_request.domain_name_request))
+            self.sys_log.info(
+                f"DNS Server: Responding to domain lookup request for {payload.dns_request.domain_name_request} "
+                f"with ip address: {payload.dns_reply.domain_name_ip_address}"
+            )
             # send reply
             self.send(payload, session_id)
-            return payload.dns_reply is not None
+            return payload.dns_reply.domain_name_ip_address is not None
 
         return False
 

tests/integration_tests/system/test_dns_client_server.py

@@ -20,11 +20,9 @@ def test_dns_client_server(uc2_network):
     dns_server.show()
 
     # fake domain should not be added to dns cache
-    dns_client.check_domain_exists(
+    assert not dns_client.check_domain_exists(target_domain="fake-domain.com")
-        target_domain="fake-domain.com", dest_ip_address=IPv4Address(domain_controller.ip_address)
-    )
     assert dns_client.dns_cache.get("fake-domain.com", None) is None
 
     # arcd.com is registered in dns server and should be saved to cache
-    dns_client.check_domain_exists(target_domain="arcd.com", dest_ip_address=IPv4Address(domain_controller.ip_address))
+    assert dns_client.check_domain_exists(target_domain="arcd.com")
     assert dns_client.dns_cache.get("arcd.com", None) is not None