/// <summary>
/// Sends the specified <see cref="AK.Net.Dns.DnsQuery"/> to the specified
/// end point and return the <see cref="AK.Net.Dns.DnsReply"/>.
/// </summary>
/// <param name="query">The query to send.</param>
/// <param name="endpoint">The transport end point.</param>
/// <returns>
/// The <see cref="AK.Net.Dns.DnsReply"/> to the <see cref="AK.Net.Dns.DnsQuery"/>.
/// </returns>
/// <exception cref="System.ArgumentNullException">
/// Thrown when <paramref name="endpoint"/> is <see langword="null"/>.
/// </exception>
/// <exception cref="AK.Net.Dns.DnsTransportException">
/// Thrown when a transport error occurs.
/// </exception>
public override DnsReply Send(DnsQuery query, IPEndPoint endpoint)
{
Guard.NotNull(endpoint, "endpoint");
DnsReply reply = null;
IDnsTransport transport = SelectTransport(query);
try {
reply = transport.Send(query, endpoint);
} catch (DnsTransportException exc) {
// If the selected transport was TCP, we cannot fail over.
// NOTE this comparison is not thread safe, but at worst it would mean
// the query being sent again.
if (transport == this.TcpTransport)
{
throw;
}
this.Log.Warn("UDP transport failure, failing over to TCP:", exc);
}
if (reply != null)
{
if (!reply.Header.IsTruncated)
{
return(reply);
}
this.Log.InfoFormat("message truncated, failing over to TCP, question={0}", query.Question);
}
return(this.TcpTransport.Send(query, endpoint));
}
public Resolver(IDnsTransport transport, IQueryCache cache = null, IWhoisTransport wtransport = null, ITLDHandler tldHandler = null, ISpfChecker checker = null, int retrys = 3, int timeout = 60)
{
Transport = transport;
SpfChecker = (checker ?? new SpfChecker());
Retries = retrys;
TimeOut = timeout;
UseRecursion = useRecursion;
Cache = (cache ?? new QueryCache());
WhoisTransport = (wtransport ?? new WhoisTcpTransport());
TldHandler = (tldHandler ?? new TldHandler());
}
/// <summary>
/// Selects the best transport for the specified <paramref name="query"/>.
/// </summary>
/// <param name="query">The query.</param>
/// <returns>The best <see cref="AK.Net.Dns.IDnsTransport"/> for the specified
/// <paramref name="query"/>.</returns>
/// <exception cref="System.ArgumentNullException">
/// Thrown when <paramref name="query"/> is <see langword="null"/>.
/// </exception>
protected virtual IDnsTransport SelectTransport(DnsQuery query)
{
Guard.NotNull(query, "query");
IDnsTransport transport = this.UdpTransport;
if (query.Questions.Count > 0)
{
// TODO does this code belong here?
switch (query.Questions[0].Type)
{
case DnsQueryType.Axfr:
transport = this.TcpTransport;
break;
default:
break;
}
}
return(transport);
}
