public override async Task <DnsDatagram> QueryAsync(DnsDatagram request, int timeout, int retries, CancellationToken cancellationToken)
{
_lastQueried = DateTime.UtcNow;
async Task <HttpRequestMessage> GetHttpRequest()
{
Uri queryUri;
if (_proxy == null)
{
if (_server.IsIPEndPointStale)
{
await _server.RecursiveResolveIPAddressAsync();
}
queryUri = new Uri(_server.DnsOverHttpEndPoint.Scheme + "://" + _server.IPEndPoint.ToString() + _server.DnsOverHttpEndPoint.PathAndQuery);
}
else
{
if (_server.IPEndPoint == null)
{
queryUri = _server.DnsOverHttpEndPoint;
}
else
{
queryUri = new Uri(_server.DnsOverHttpEndPoint.Scheme + "://" + _server.IPEndPoint.ToString() + _server.DnsOverHttpEndPoint.PathAndQuery);
}
}
return(new HttpRequestMessage(HttpMethod.Get, queryUri.AbsoluteUri + "?name=" + request.Question[0].Name + "&type=" + Convert.ToString((int)request.Question[0].Type)));
}
//DoH JSON format request
Stopwatch stopwatch = new Stopwatch();
int retry = 0;
while (retry < retries) //retry loop
{
retry++;
if (cancellationToken.IsCancellationRequested)
{
return(await Task.FromCanceled <DnsDatagram>(cancellationToken)); //task cancelled
}
stopwatch.Start();
Task <HttpResponseMessage> task = _httpClient.SendAsync(await GetHttpRequest(), cancellationToken);
using (CancellationTokenSource timeoutCancellationTokenSource = new CancellationTokenSource())
{
using (CancellationTokenRegistration ctr = cancellationToken.Register(delegate() { timeoutCancellationTokenSource.Cancel(); }))
{
if (await Task.WhenAny(task, Task.Delay(timeout, timeoutCancellationTokenSource.Token)) != task)
{
continue; //request timed out; retry
}
}
timeoutCancellationTokenSource.Cancel(); //to stop delay task
}
HttpResponseMessage httpResponse = await task;
stopwatch.Stop();
httpResponse.EnsureSuccessStatusCode();
string responseJson = await httpResponse.Content.ReadAsStringAsync(cancellationToken);
//parse response
DnsDatagram response = DnsDatagram.ReadFromJson(JsonConvert.DeserializeObject(responseJson), responseJson.Length);
response.SetIdentifier(request.Identifier);
response.SetMetadata(_server, _protocol, stopwatch.Elapsed.TotalMilliseconds);
if (response.Question.Count != request.Question.Count)
{
throw new DnsClientResponseValidationException("Invalid response was received: question count mismatch.");
}
for (int i = 0; i < response.Question.Count; i++)
{
if (request.Question[i].ZoneCut == null)
{
if (!response.Question[i].Name.Equals(request.Question[i].Name, StringComparison.Ordinal))
{
throw new DnsClientResponseValidationException("Invalid response was received: QNAME mismatch.");
}
if (response.Question[i].Type != request.Question[i].Type)
{
throw new DnsClientResponseValidationException("Invalid response was received: QTYPE mismatch.");
}
}
else
{
if (!response.Question[i].Name.Equals(request.Question[i].MinimizedName, StringComparison.Ordinal))
{
throw new DnsClientResponseValidationException("Invalid response was received: QNAME mismatch.");
}
if (response.Question[i].Type != request.Question[i].MinimizedType)
{
throw new DnsClientResponseValidationException("Invalid response was received: QTYPE mismatch.");
}
}
if (response.Question[i].Class != request.Question[i].Class)
{
throw new DnsClientResponseValidationException("Invalid response was received: QCLASS mismatch.");
}
}
return(response);
}
throw new DnsClientException("DnsClient failed to resolve the request: request timed out.");
}
