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Handle exceptions during receive and dispose timer #24

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Handle exceptions during receive and dispose timer #24

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3c36025
Handle exceptions during receive and dispose timer
Nuklon Feb 28, 2024
365ff39
Update DHCPServer.cs
Nuklon Feb 28, 2024
5e47792
Update DHCPServer.cs
Nuklon Feb 28, 2024
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118 changes: 74 additions & 44 deletions DHCPServer/Library/DHCPServer.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -14,6 +14,7 @@ public class DHCPServer : IDHCPServer
{
private const int ClientInformationWriteRetries = 10;

private readonly SemaphoreSlim _taskSemaphoreSlim = new(1, 1);
private IPEndPoint _endPoint = new(IPAddress.Loopback, 67);
private IUDPSocket _socket = default!;
private IPAddress _subnetMask = IPAddress.Any;
Expand All @@ -34,7 +35,8 @@ public class DHCPServer : IDHCPServer
private readonly AutoPumpQueue<int> _updateClientInfoQueue;
private readonly Random _random = new();
private CancellationTokenSource _cancellationTokenSource = new();
private Task? _mainTask;
private Task? _receiveTask;
private Task? _timerTask;

#region IDHCPServer Members

Expand Down Expand Up @@ -235,7 +237,7 @@ public DHCPServer(ILogger logger, string? clientInfoPath, IUDPSocketFactory udpS
_logger = logger;
_clientInfoPath = clientInfoPath;
_udpSocketFactory = udpSocketFactory;
_hostName = System.Environment.MachineName;
_hostName = Environment.MachineName;
}

public void Start()
Expand All @@ -262,7 +264,8 @@ public void Start()
Trace($"Starting DHCP server '{_endPoint}'");
_active = true;
_socket = _udpSocketFactory.Create(_endPoint, 2048, true, 10);
_mainTask = Task.Run(async () => { await MainTask(_cancellationTokenSource.Token); });
_receiveTask = Task.Run(async () => await ReceiveTask(_cancellationTokenSource.Token));
_timerTask = Task.Run(async () => await TimerTask(_cancellationTokenSource.Token));
Trace("DHCP Server start succeeded");
}
catch(Exception e)
Expand Down Expand Up @@ -339,21 +342,29 @@ private void Stop(Exception? reason)
notify = true;
_cancellationTokenSource.Cancel();

if(_mainTask!= null)
AwaitTask(_receiveTask);
AwaitTask(_timerTask);

_receiveTask = null;
_timerTask = null;

_socket.Dispose();
Trace("Stopped");

void AwaitTask(Task task)
{
try
if(task != null)
{
_mainTask.GetAwaiter().GetResult();
}
catch(Exception ex)
{
_logger?.LogError(ex, $"Exception during {nameof(Stop)}");
try
{
task.GetAwaiter().GetResult();
}
catch(Exception ex)
{
_logger?.LogError(ex, $"Exception during {nameof(Stop)}");
}
}
_mainTask = null;
}

_socket.Dispose();
Trace("Stopped");
}

if(notify)
Expand Down Expand Up @@ -825,57 +836,76 @@ private async Task OfferClient(DHCPMessage dhcpMessage, DHCPClient client)
await SendOFFER(dhcpMessage, client.IPAddress, _leaseTime);
}

private async Task MainTask(CancellationToken cancellationToken)
private async Task ReceiveTask(CancellationToken cancellationToken)
{
var timer = new PeriodicTimer(TimeSpan.FromSeconds(1));
Task<(IPEndPoint,ReadOnlyMemory<byte>)>? receiveTask = default;
Task? timerTask = default;

while(!cancellationToken.IsCancellationRequested)
{
receiveTask ??= _socket.Receive(cancellationToken);
timerTask ??= timer.WaitForNextTickAsync(cancellationToken).AsTask();

var completedTask = await Task.WhenAny(receiveTask, timerTask);
bool enteredSemaphore = false;

if(completedTask == receiveTask)
try
{
try
{
(var ipEndPoint, var data) = await receiveTask;
await OnReceive(ipEndPoint, data);
}
catch(UDPSocketException ex)
{
if(ex.IsFatal)
{
_logger?.LogError(ex, $"fatal exception in {nameof(MainTask)}");
throw;
}
}
finally
(IPEndPoint ipEndPoint, ReadOnlyMemory<byte> data) = await _socket.Receive(cancellationToken);
await _taskSemaphoreSlim.WaitAsync(cancellationToken);
enteredSemaphore = true;
await OnReceive(ipEndPoint, data);
}
catch(UDPSocketException ex)
{
if(ex.IsFatal)
{
receiveTask = null;
_logger?.LogError(ex, $"fatal exception in {nameof(ReceiveTask)}");
return;
}
}
else if(completedTask == timerTask)
catch
{
// Ignored.
}
finally
{
if(enteredSemaphore)
_taskSemaphoreSlim.Release();
}
}
}

private async Task TimerTask(CancellationToken cancellationToken)
{
PeriodicTimer timer = new(TimeSpan.FromSeconds(1));

try
{
while(!cancellationToken.IsCancellationRequested)
{
bool enteredSemaphore = false;

try
{
await timerTask;
await timer.WaitForNextTickAsync(cancellationToken);
await _taskSemaphoreSlim.WaitAsync(cancellationToken);
enteredSemaphore = true;
CheckLeaseExpiration();
}
finally
{
timerTask = null;
if(enteredSemaphore)
_taskSemaphoreSlim.Release();
}
}
}
catch
{
// Ignored.
}
finally
{
timer.Dispose();
}
}

private DHCPClient? GetKnownClient(DHCPClient client)
{
return _clients.TryGetValue(client, out var value) ? value : null;
return _clients.GetValueOrDefault(client);
}

private async Task OnReceive(IPEndPoint endPoint, ReadOnlyMemory<byte> data)
Expand Down Expand Up @@ -1050,7 +1080,7 @@ private async Task OnReceive(IPEndPoint endPoint, ReadOnlyMemory<byte> data)
client.State = DHCPClient.TState.Assigned;
client.LeaseStartTime = DateTime.Now;
client.LeaseDuration = _leaseTime;
_=_clients.TryAdd(client, client);
_ = _clients.TryAdd(client, client);
await SendACK(dhcpMessage, dhcpMessage.ClientIPAddress, client.LeaseDuration);
}
else
Expand Down