From f32048712880d3951404656c10bdb1c86fd55a47 Mon Sep 17 00:00:00 2001
From: Nick Todd <nick.todd@t-s.qinetiq.com>
Date: Tue, 14 Nov 2023 15:13:05 +0000
Subject: [PATCH] #2041: Implement NTP protocol for server

---
 .../simulator/network/protocols/ntp.py        | 18 +++++++---
 .../system/services/ntp/ntp_server.py         | 36 ++++++++++++++++---
 2 files changed, 44 insertions(+), 10 deletions(-)

diff --git a/src/primaite/simulator/network/protocols/ntp.py b/src/primaite/simulator/network/protocols/ntp.py
index f14dab73..89a26961 100644
--- a/src/primaite/simulator/network/protocols/ntp.py
+++ b/src/primaite/simulator/network/protocols/ntp.py
@@ -2,22 +2,22 @@ from __future__ import annotations
 
 from ipaddress import IPv4Address
 from typing import Optional
-
 from pydantic import BaseModel
-
 from primaite.simulator.network.protocols.packet import DataPacket
+from datetime import datetime
 
 
 class NTPRequest(BaseModel):
     """Represents a NTP Request packet."""
 
-    pass
+    ntp_client: IPv4Address = None
 
 
 class NTPReply(BaseModel):
     """Represents a NTP Reply packet."""
 
-    pass
+    ntp_datetime: datetime
+    "NTP datetime object set by NTP Server."
 
 
 class NTPPacket(DataPacket):
@@ -31,4 +31,12 @@ class NTPPacket(DataPacket):
     ntp_request: NTPRequest
     "NTP Request packet sent by NTP Client."
     ntp_reply: Optional[NTPReply] = None
-    "NTP Reply packet generated by NTP Server."
+
+    def generate_reply(self, time: datetime) -> NTPPacket:
+        """ Generate a NTPPacket containing the time in a NTPReply object
+
+        :param time: datetime object representing the time from the NTP server.
+        :return: A new NTPPacket object.
+        """
+        self.ntp_reply = NTPReply(time)
+        return self
diff --git a/src/primaite/simulator/system/services/ntp/ntp_server.py b/src/primaite/simulator/system/services/ntp/ntp_server.py
index 914dd1c3..50a582a4 100644
--- a/src/primaite/simulator/system/services/ntp/ntp_server.py
+++ b/src/primaite/simulator/system/services/ntp/ntp_server.py
@@ -2,12 +2,15 @@ from ipaddress import IPv4Address
 from typing import Any, Dict, Optional
 
 from primaite import getLogger
+from primaite.simulator.network.protocols.ntp import NTPPacket
 from primaite.simulator.network.transmission.network_layer import IPProtocol
 from primaite.simulator.network.transmission.transport_layer import Port
 from primaite.simulator.system.services.service import Service
+from datetime import datetime
 
 _LOGGER = getLogger(__name__)
 
+
 class NTPServer(Service):
     """Represents a NTP server as a service"""
 
@@ -48,9 +51,32 @@ class NTPServer(Service):
             session_id: Optional[str] = None,
             **kwargs,
     ) -> bool:
-        """Receives a request from NTPClient"""
-        pass
+        """Receives a request from NTPClient.
 
-    def send(self):
-        """Sends time data to NTPClient"""
-        pass
+        Check that request has a valid IP address.
+
+        :param payload: The payload to send.
+        :param session_id: Id of the session (Optional).
+
+        :return: True if valid NTP request else False.
+        """
+        if not (isinstance(payload, NTPPacket) and
+                payload.ntp_request.ntp_client):
+            _LOGGER.debug(f"{payload} is not a NTPPacket")
+            return False
+        payload: NTPPacket = payload
+        if payload.ntp_request.ntp_client:
+            self.sys_log.info(
+                f"{self.name}: Received request for {payload.ntp_request.ntp_client} "
+                f"from session {session_id}"
+            )
+            # generate a reply with the current time
+            time = datetime.now()
+            payload = payload.generate_reply(time)
+            self.sys_log.info(
+                f"{self.name}: Responding to NTP request for {payload.ntp_request.ntp_client} "
+                f"with current time: {time}"
+            )
+            # send reply
+            self.send(payload, session_id)
+            return True