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// Copyright 2024 Michael Conrad.
// Licensed under the Apache License, Version 2.0.
// See LICENSE file for details.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Threading;
using DnsClient.Protocol;
namespace DnsClient
{
/// <summary>
/// The options used to override the defaults of <see cref="LookupClient"/> per query.
/// </summary>
public class DnsQueryOptions
{
/// <summary>
/// The minimum payload size. Anything equal or less than that will default back to this value and might disable EDNS.
/// </summary>
public const int MinimumBufferSize = 512;
/// <summary>
/// The maximum reasonable payload size.
/// </summary>
public const int MaximumBufferSize = 4096;
private static readonly TimeSpan s_defaultTimeout = TimeSpan.FromSeconds(5);
private static readonly TimeSpan s_infiniteTimeout = System.Threading.Timeout.InfiniteTimeSpan;
private static readonly TimeSpan s_maxTimeout = TimeSpan.FromMilliseconds(int.MaxValue);
private TimeSpan _timeout = s_defaultTimeout;
private int _ednsBufferSize = MaximumBufferSize;
private TimeSpan _failedResultsCacheDuration = s_defaultTimeout;
/// <summary>
/// Gets or sets a flag indicating whether each <see cref="IDnsQueryResponse"/> will contain a full documentation of the response(s).
/// Default is <c>False</c>.
/// </summary>
/// <seealso cref="IDnsQueryResponse.AuditTrail"/>
public bool EnableAuditTrail { get; set; }
/// <summary>
/// Gets or sets a flag indicating whether DNS queries should use response caching or not.
/// The cache duration is calculated by the resource record of the response. Usually, the lowest TTL is used.
/// Default is <c>True</c>.
/// </summary>
/// <remarks>
/// In case the DNS Server returns records with a TTL of zero. The response cannot be cached.
/// </remarks>
public bool UseCache { get; set; } = true;
/// <summary>
/// Gets or sets a flag indicating whether DNS queries should instruct the DNS server to do recursive lookups, or not.
/// Default is <c>True</c>.
/// </summary>
/// <value>The flag indicating if recursion should be used or not.</value>
public bool Recursion { get; set; } = true;
/// <summary>
/// Gets or sets the number of tries to get a response from one name server before trying the next one.
/// Only transient errors, like network or connection errors will be retried.
/// Default is <c>2</c> which will be three tries total.
/// <para>
/// If all configured <see cref="DnsQueryAndServerOptions.NameServers"/> error out after retries, an exception will be thrown at the end.
/// </para>
/// </summary>
/// <value>The number of retries.</value>
public int Retries { get; set; } = 2;
/// <summary>
/// Gets or sets a flag indicating whether the <see cref="ILookupClient"/> should throw a <see cref="DnsResponseException"/>
/// in case the query result has a <see cref="DnsResponseCode"/> other than <see cref="DnsResponseCode.NoError"/>.
/// Default is <c>False</c>.
/// </summary>
/// <remarks>
/// <para>
/// If set to <c>False</c>, the query will return a result with an <see cref="IDnsQueryResponse.ErrorMessage"/>
/// which contains more information.
/// </para>
/// <para>
/// If set to <c>True</c>, any query method of <see cref="IDnsQuery"/> will throw an <see cref="DnsResponseException"/> if
/// the response header indicates an error.
/// </para>
/// <para>
/// If both, <see cref="ContinueOnDnsError"/> and <see cref="ThrowDnsErrors"/> are set to <c>True</c>,
/// <see cref="ILookupClient"/> will continue to query all configured <see cref="DnsQueryAndServerOptions.NameServers"/>.
/// If none of the servers yield a valid response, a <see cref="DnsResponseException"/> will be thrown
/// with the error of the last response.
/// </para>
/// </remarks>
/// <seealso cref="DnsResponseCode"/>
/// <seealso cref="ContinueOnDnsError"/>
public bool ThrowDnsErrors { get; set; }
/// <summary>
/// Gets or sets a flag indicating whether the <see cref="ILookupClient"/> can cycle through all
/// configured <see cref="DnsQueryAndServerOptions.NameServers"/> on each consecutive request, basically using a random server, or not.
/// Default is <c>True</c>.
/// If only one <see cref="NameServer"/> is configured, this setting is not used.
/// </summary>
/// <remarks>
/// <para>
/// If <c>False</c>, configured endpoint will be used in random order.
/// If <c>True</c>, the order will be preserved.
/// </para>
/// <para>
/// Even if <see cref="UseRandomNameServer"/> is set to <c>True</c>, the endpoint might still get
/// disabled and might not being used for some time if it errors out, e.g. no connection can be established.
/// </para>
/// </remarks>
public bool UseRandomNameServer { get; set; } = true;
/// <summary>
/// Gets or sets a flag indicating whether to query the next configured <see cref="DnsQueryAndServerOptions.NameServers"/> in case the response of the last query
/// returned a <see cref="DnsResponseCode"/> other than <see cref="DnsResponseCode.NoError"/>.
/// Default is <c>True</c>.
/// </summary>
/// <remarks>
/// If <c>True</c>, lookup client will continue until a server returns a valid result, or,
/// if no <see cref="DnsQueryAndServerOptions.NameServers"/> yield a valid result, the last response with the error will be returned.
/// In case no server yields a valid result and <see cref="ThrowDnsErrors"/> is also enabled, an exception
/// will be thrown containing the error of the last response.
/// <para>
/// If <c>True</c> and <see cref="ThrowDnsErrors"/> is enabled, the exception will be thrown on first encounter without trying any other servers.
/// </para>
/// </remarks>
/// <seealso cref="ThrowDnsErrors"/>
public bool ContinueOnDnsError { get; set; } = true;
/// <summary>
/// Gets or sets a flag indicating whether to query the next configured <see cref="DnsQueryAndServerOptions.NameServers"/>
/// if the response does not have an error <see cref="DnsResponseCode"/> but the query was not answered by the response.
/// Default is <c>True</c>.
/// </summary>
/// <remarks>
/// The query is answered if there is at least one <see cref="DnsResourceRecord"/> in the answers section
/// matching the <see cref="DnsQuestion"/>'s <see cref="QueryType"/>.
/// <para>
/// If there are zero answers in the response, the query is not answered, independent of the <see cref="QueryType"/>.
/// If there are answers in the response, the <see cref="QueryType"/> is used to find a matching record,
/// query types <see cref="QueryType.ANY"/> and <see cref="QueryType.AXFR"/> will be ignored by this check.
/// </para>
/// </remarks>
public bool ContinueOnEmptyResponse { get; set; } = true;
/// <summary>
/// Gets or sets the request timeout in milliseconds. <see cref="Timeout"/> is used for limiting the connection and request time for one operation.
/// Timeout must be greater than zero and less than <see cref="int.MaxValue"/>.
/// If <see cref="Timeout.InfiniteTimeSpan"/> (or -1) is used, no timeout will be applied.
/// Default is 5 seconds.
/// </summary>
/// <remarks>
/// If a very short timeout is configured, queries will more likely result in <see cref="TimeoutException"/>s.
/// <para>
/// Important to note, <see cref="TimeoutException"/>s will be retried, if <see cref="Retries"/> are not disabled (set to <c>0</c>).
/// This should help in case one or more configured DNS servers are not reachable or under load for example.
/// </para>
/// </remarks>
public TimeSpan Timeout
{
get { return _timeout; }
set
{
if ((value <= TimeSpan.Zero || value > s_maxTimeout) && value != s_infiniteTimeout)
{
throw new ArgumentOutOfRangeException(nameof(value));
}
_timeout = value;
}
}
/// <summary>
/// Gets or sets a flag indicating whether TCP should be used in case a UDP response is truncated.
/// Default is <c>True</c>.
/// <para>
/// If <c>False</c>, truncated results will potentially yield no or incomplete answers.
/// </para>
/// </summary>
public bool UseTcpFallback { get; set; } = true;
/// <summary>
/// Gets or sets a flag indicating whether UDP should not be used at all.
/// Default is <c>False</c>.
/// <para>
/// Enable this only if UDP cannot be used because of your firewall rules for example.
/// Also, zone transfers (see <see cref="QueryType.AXFR"/>) must use TCP only.
/// </para>
/// </summary>
public bool UseTcpOnly { get; set; }
/// <summary>
/// Gets or sets the maximum buffer used for UDP requests.
/// Defaults to <c>4096</c>.
/// <para>
/// If this value is less or equal to <c>512</c> bytes, EDNS might be disabled.
/// </para>
/// </summary>
public int ExtendedDnsBufferSize
{
get
{
return _ednsBufferSize;
}
set
{
_ednsBufferSize =
value < MinimumBufferSize ? MinimumBufferSize :
value > MaximumBufferSize ? MaximumBufferSize : value;
}
}
/// <summary>
/// Gets or sets a flag indicating whether EDNS should be enabled and the <c>DO</c> flag should be set.
/// Defaults to <c>False</c>.
/// </summary>
public bool RequestDnsSecRecords { get; set; }
/// <summary>
/// Gets or sets a flag indicating whether the DNS failures are being cached. The purpose of caching
/// failures is to reduce repeated lookup attempts within a short space of time.
/// Defaults to <c>False</c>.
/// </summary>
public bool CacheFailedResults { get; set; }
/// <summary>
/// Gets or sets the duration to cache failed lookups. Does not apply if failed lookups are not being cached.
/// Defaults to <c>5 seconds</c>.
/// </summary>
public TimeSpan FailedResultsCacheDuration
{
get { return _failedResultsCacheDuration; }
set
{
if ((value <= TimeSpan.Zero || value > s_maxTimeout) && value != s_infiniteTimeout)
{
throw new ArgumentOutOfRangeException(nameof(value));
}
_failedResultsCacheDuration = value;
}
}
/// <summary>
/// Converts the query options into readonly settings.
/// </summary>
/// <param name="fromOptions">The options.</param>
public static implicit operator DnsQuerySettings(DnsQueryOptions fromOptions)
{
if (fromOptions == null)
{
return null;
}
return new DnsQuerySettings(fromOptions);
}
}
/// <summary>
/// The options used to override the defaults of <see cref="LookupClient"/> per query.
/// </summary>
public class DnsQueryAndServerOptions : DnsQueryOptions
{
/// <summary>
/// Creates a new instance of <see cref="DnsQueryAndServerOptions"/> without name servers.
/// If no nameservers are configured, a query will fallback to the nameservers already configured on the <see cref="LookupClient"/> instance.
/// </summary>
public DnsQueryAndServerOptions()
{
}
/// <summary>
/// Creates a new instance of <see cref="DnsQueryAndServerOptions"/>.
/// </summary>
/// <param name="nameServers">A collection of name servers.</param>
/// <exception cref="ArgumentNullException">If <paramref name="nameServers"/> is null.</exception>
public DnsQueryAndServerOptions(params NameServer[] nameServers)
: base()
{
if (nameServers != null && nameServers.Length > 0)
{
NameServers = nameServers.ToList();
}
else
{
throw new ArgumentNullException(nameof(nameServers));
}
}
// TODO: remove overloads in favor of implicit conversion to NameServer?
/// <summary>
/// Creates a new instance of <see cref="DnsQueryAndServerOptions"/>.
/// </summary>
/// <param name="nameServers">A collection of name servers.</param>
/// <exception cref="ArgumentNullException">If <paramref name="nameServers"/> is null.</exception>
public DnsQueryAndServerOptions(params IPEndPoint[] nameServers)
: this(nameServers?.Select(p => (NameServer)p).ToArray())
{
}
/// <summary>
/// Creates a new instance of <see cref="DnsQueryAndServerOptions"/>.
/// </summary>
/// <param name="nameServers">A collection of name servers.</param>
/// <exception cref="ArgumentNullException">If <paramref name="nameServers"/> is null.</exception>
public DnsQueryAndServerOptions(params IPAddress[] nameServers)
: this(nameServers?.Select(p => (NameServer)p).ToArray())
{
}
/// <summary>
/// Gets a list of name servers which should be used to query.
/// </summary>
public IReadOnlyList<NameServer> NameServers { get; } = new NameServer[0];
/// <summary>
/// Converts the query options into readonly settings.
/// </summary>
/// <param name="fromOptions">The options.</param>
public static implicit operator DnsQueryAndServerSettings(DnsQueryAndServerOptions fromOptions)
{
if (fromOptions == null)
{
return null;
}
return new DnsQueryAndServerSettings(fromOptions);
}
}
/// <summary>
/// The options used to configure defaults in <see cref="LookupClient"/> and to optionally use specific settings per query.
/// </summary>
public class LookupClientOptions : DnsQueryAndServerOptions
{
private static readonly TimeSpan s_infiniteTimeout = System.Threading.Timeout.InfiniteTimeSpan;
// max is 24 days
private static readonly TimeSpan s_maxTimeout = TimeSpan.FromMilliseconds(int.MaxValue);
private TimeSpan? _minimumCacheTimeout;
private TimeSpan? _maximumCacheTimeout;
/// <summary>
/// Creates a new instance of <see cref="LookupClientOptions"/> with default settings.
/// </summary>
public LookupClientOptions()
: base()
{
}
/// <summary>
/// Creates a new instance of <see cref="LookupClientOptions"/>.
/// </summary>
/// <param name="nameServers">A collection of name servers.</param>
/// <exception cref="ArgumentNullException">If <paramref name="nameServers"/> is null.</exception>
public LookupClientOptions(params NameServer[] nameServers)
: base(nameServers)
{
AutoResolveNameServers = false;
}
/// <summary>
/// Creates a new instance of <see cref="LookupClientOptions"/>.
/// </summary>
/// <param name="nameServers">A collection of name servers.</param>
/// <exception cref="ArgumentNullException">If <paramref name="nameServers"/> is null.</exception>
public LookupClientOptions(params IPEndPoint[] nameServers)
: base(nameServers)
{
AutoResolveNameServers = false;
}
/// <summary>
/// Creates a new instance of <see cref="LookupClientOptions"/>.
/// </summary>
/// <param name="nameServers">A collection of name servers.</param>
/// <exception cref="ArgumentNullException">If <paramref name="nameServers"/> is null.</exception>
public LookupClientOptions(params IPAddress[] nameServers)
: base(nameServers)
{
AutoResolveNameServers = false;
}
/// <summary>
/// Gets or sets a flag indicating whether the name server collection should be automatically resolved.
/// Default is <c>True</c>.
/// </summary>
/// <remarks>
/// If name servers are configured manually via the constructor, this flag is set to false.
/// If you want both, your manually configured servers and auto resolved name servers,
/// you can use both (ctor or) <see cref="DnsQueryAndServerOptions.NameServers"/> and <see cref="AutoResolveNameServers"/> set to <c>True</c>.
/// </remarks>
public bool AutoResolveNameServers { get; set; } = true;
/// <summary>
/// Gets or sets a <see cref="TimeSpan"/> which can override the TTL of a resource record in case the
/// TTL of the record is lower than this minimum value.
/// Default is <c>Null</c>.
/// <para>
/// This is useful in case the server returns records with zero TTL.
/// </para>
/// </summary>
/// <remarks>
/// This setting gets ignored in case <see cref="DnsQueryOptions.UseCache"/> is set to <c>False</c>,
/// or the value is set to <c>Null</c> or <see cref="TimeSpan.Zero"/>.
/// The maximum value is 24 days or <see cref="Timeout.Infinite"/> (choose a wise setting).
/// </remarks>
public TimeSpan? MinimumCacheTimeout
{
get { return _minimumCacheTimeout; }
set
{
if (value.HasValue &&
(value < TimeSpan.Zero || value > s_maxTimeout) && value != s_infiniteTimeout)
{
throw new ArgumentOutOfRangeException(nameof(value));
}
if (value == TimeSpan.Zero)
{
_minimumCacheTimeout = null;
}
else
{
_minimumCacheTimeout = value;
}
}
}
/// <summary>
/// Gets a <see cref="TimeSpan"/> which can override the TTL of a resource record in case the
/// TTL of the record is higher than this maximum value.
/// Default is <c>Null</c>.
/// </summary>
/// <remarks>
/// This setting gets ignored in case <see cref="DnsQueryOptions.UseCache"/> is set to <c>False</c>,
/// or the value is set to <c>Null</c>, <see cref="Timeout.Infinite"/> or <see cref="TimeSpan.Zero"/>.
/// The maximum value is 24 days (which shouldn't be used).
/// </remarks>
public TimeSpan? MaximumCacheTimeout
{
get { return _maximumCacheTimeout; }
set
{
if (value.HasValue &&
(value < TimeSpan.Zero || value > s_maxTimeout) && value != s_infiniteTimeout)
{
throw new ArgumentOutOfRangeException(nameof(value));
}
if (value == TimeSpan.Zero)
{
_maximumCacheTimeout = null;
}
else
{
_maximumCacheTimeout = value;
}
}
}
}
#pragma warning disable CS0659 // Type overrides Object.Equals(object o) but does not override Object.GetHashCode() - intentionally, Equals is only used by unit tests
/// <summary>
/// The options used to override the defaults of <see cref="LookupClient"/> per query.
/// </summary>
public class DnsQuerySettings : IEquatable<DnsQuerySettings>
{
/// <summary>
/// Gets a flag indicating whether each <see cref="IDnsQueryResponse"/> will contain a full documentation of the response(s).
/// Default is <c>False</c>.
/// </summary>
/// <seealso cref="IDnsQueryResponse.AuditTrail"/>
public bool EnableAuditTrail { get; }
/// <summary>
/// Gets a flag indicating whether DNS queries should use response caching or not.
/// The cache duration is calculated by the resource record of the response. Usually, the lowest TTL is used.
/// Default is <c>True</c>.
/// </summary>
/// <remarks>
/// In case the DNS Server returns records with a TTL of zero. The response cannot be cached.
/// </remarks>
public bool UseCache { get; }
/// <summary>
/// Gets a flag indicating whether DNS queries should instruct the DNS server to do recursive lookups, or not.
/// Default is <c>True</c>.
/// </summary>
/// <value>The flag indicating if recursion should be used or not.</value>
public bool Recursion { get; }
/// <summary>
/// Gets the number of tries to get a response from one name server before trying the next one.
/// Only transient errors, like network or connection errors will be retried.
/// Default is <c>5</c>.
/// <para>
/// If all configured <see cref="DnsQueryAndServerSettings.NameServers"/> error out after retries, an exception will be thrown at the end.
/// </para>
/// </summary>
/// <value>The number of retries.</value>
public int Retries { get; }
/// <summary>
/// Gets a flag indicating whether the <see cref="ILookupClient"/> should throw a <see cref="DnsResponseException"/>
/// in case the query result has a <see cref="DnsResponseCode"/> other than <see cref="DnsResponseCode.NoError"/>.
/// Default is <c>False</c>.
/// </summary>
/// <remarks>
/// <para>
/// If set to <c>False</c>, the query will return a result with an <see cref="IDnsQueryResponse.ErrorMessage"/>
/// which contains more information.
/// </para>
/// <para>
/// If set to <c>True</c>, any query method of <see cref="IDnsQuery"/> will throw an <see cref="DnsResponseException"/> if
/// the response header indicates an error.
/// </para>
/// <para>
/// If both, <see cref="ContinueOnDnsError"/> and <see cref="ThrowDnsErrors"/> are set to <c>True</c>,
/// <see cref="ILookupClient"/> will continue to query all configured <see cref="DnsQueryAndServerSettings.NameServers"/>.
/// If none of the servers yield a valid response, a <see cref="DnsResponseException"/> will be thrown
/// with the error of the last response.
/// </para>
/// </remarks>
/// <seealso cref="DnsResponseCode"/>
/// <seealso cref="ContinueOnDnsError"/>
public bool ThrowDnsErrors { get; }
/// <summary>
/// Gets a flag indicating whether the <see cref="ILookupClient"/> can cycle through all
/// configured <see cref="DnsQueryAndServerSettings.NameServers"/> on each consecutive request, basically using a random server, or not.
/// Default is <c>True</c>.
/// If only one <see cref="NameServer"/> is configured, this setting is not used.
/// </summary>
/// <remarks>
/// <para>
/// If <c>False</c>, configured endpoint will be used in random order.
/// If <c>True</c>, the order will be preserved.
/// </para>
/// <para>
/// Even if <see cref="UseRandomNameServer"/> is set to <c>True</c>, the endpoint might still get
/// disabled and might not being used for some time if it errors out, e.g. no connection can be established.
/// </para>
/// </remarks>
public bool UseRandomNameServer { get; }
/// <summary>
/// Gets a flag indicating whether to query the next configured <see cref="DnsQueryAndServerSettings.NameServers"/> in case the response of the last query
/// returned a <see cref="DnsResponseCode"/> other than <see cref="DnsResponseCode.NoError"/>.
/// Default is <c>True</c>.
/// </summary>
/// <remarks>
/// If <c>True</c>, lookup client will continue until a server returns a valid result, or,
/// if no <see cref="DnsQueryAndServerSettings.NameServers"/> yield a valid result, the last response with the error will be returned.
/// In case no server yields a valid result and <see cref="ThrowDnsErrors"/> is also enabled, an exception
/// will be thrown containing the error of the last response.
/// <para>
/// If <c>True</c> and <see cref="ThrowDnsErrors"/> is enabled, the exception will be thrown on first encounter without trying any other servers.
/// </para>
/// </remarks>
/// <seealso cref="ThrowDnsErrors"/>
public bool ContinueOnDnsError { get; }
/// <summary>
/// Gets or sets a flag indicating whether to query the next configured <see cref="DnsQueryAndServerOptions.NameServers"/>
/// if the response does not have an error <see cref="DnsResponseCode"/> but the query was not answered by the response.
/// Default is <c>True</c>.
/// </summary>
/// <remarks>
/// The query is answered if there is at least one <see cref="DnsResourceRecord"/> in the answers section
/// matching the <see cref="DnsQuestion"/>'s <see cref="QueryType"/>.
/// <para>
/// If there are zero answers in the response, the query is not answered, independent of the <see cref="QueryType"/>.
/// If there are answers in the response, the <see cref="QueryType"/> is used to find a matching record,
/// query types <see cref="QueryType.ANY"/> and <see cref="QueryType.AXFR"/> will be ignored by this check.
/// </para>
/// </remarks>
public bool ContinueOnEmptyResponse { get; }
/// <summary>
/// Gets the request timeout in milliseconds. <see cref="Timeout"/> is used for limiting the connection and request time for one operation.
/// Timeout must be greater than zero and less than <see cref="int.MaxValue"/>.
/// If <see cref="Timeout.InfiniteTimeSpan"/> (or -1) is used, no timeout will be applied.
/// Default is 5 seconds.
/// </summary>
/// <remarks>
/// If a very short timeout is configured, queries will more likely result in <see cref="TimeoutException"/>s.
/// <para>
/// Important to note, <see cref="TimeoutException"/>s will be retried, if <see cref="Retries"/> are not disabled (set to <c>0</c>).
/// This should help in case one or more configured DNS servers are not reachable or under load for example.
/// </para>
/// </remarks>
public TimeSpan Timeout { get; }
/// <summary>
/// Gets a flag indicating whether TCP should be used in case a UDP response is truncated.
/// Default is <c>True</c>.
/// <para>
/// If <c>False</c>, truncated results will potentially yield no or incomplete answers.
/// </para>
/// </summary>
public bool UseTcpFallback { get; }
/// <summary>
/// Gets a flag indicating whether UDP should not be used at all.
/// Default is <c>False</c>.
/// <para>
/// Enable this only if UDP cannot be used because of your firewall rules for example.
/// Also, zone transfers (see <see cref="QueryType.AXFR"/>) must use TCP only.
/// </para>
/// </summary>
public bool UseTcpOnly { get; }
/// <summary>
/// Gets a flag indicating whether EDNS is enabled based on the values
/// of <see cref="ExtendedDnsBufferSize"/> and <see cref="RequestDnsSecRecords"/>.
/// </summary>
public bool UseExtendedDns => ExtendedDnsBufferSize > DnsQueryOptions.MinimumBufferSize || RequestDnsSecRecords;
/// <summary>
/// Gets the maximum buffer used for UDP requests.
/// Defaults to <c>4096</c>.
/// <para>
/// If this value is less or equal to <c>512</c> bytes, EDNS might be disabled.
/// </para>
/// </summary>
public int ExtendedDnsBufferSize { get; }
/// <summary>
/// Gets a flag indicating whether EDNS should be enabled and the <c>DO</c> flag should be set.
/// Defaults to <c>False</c>.
/// </summary>
public bool RequestDnsSecRecords { get; }
/// <summary>
/// Gets a flag indicating whether the DNS failures are being cached. The purpose of caching
/// failures is to reduce repeated lookup attempts within a short space of time.
/// Defaults to <c>False</c>.
/// </summary>
public bool CacheFailedResults { get; }
/// <summary>
/// If failures are being cached this value indicates how long they will be held in the cache for.
/// Defaults to <c>5 seconds</c>.
/// </summary>
public TimeSpan FailedResultsCacheDuration { get; }
/// <summary>
/// Creates a new instance of <see cref="DnsQueryAndServerSettings"/>.
/// </summary>
public DnsQuerySettings(DnsQueryOptions options)
{
if (options == null)
{
throw new ArgumentNullException(nameof(options));
}
ContinueOnDnsError = options.ContinueOnDnsError;
ContinueOnEmptyResponse = options.ContinueOnEmptyResponse;
EnableAuditTrail = options.EnableAuditTrail;
Recursion = options.Recursion;
Retries = options.Retries;
ThrowDnsErrors = options.ThrowDnsErrors;
Timeout = options.Timeout;
UseCache = options.UseCache;
UseRandomNameServer = options.UseRandomNameServer;
UseTcpFallback = options.UseTcpFallback;
UseTcpOnly = options.UseTcpOnly;
ExtendedDnsBufferSize = options.ExtendedDnsBufferSize;
RequestDnsSecRecords = options.RequestDnsSecRecords;
CacheFailedResults = options.CacheFailedResults;
FailedResultsCacheDuration = options.FailedResultsCacheDuration;
}
/// <inheritdocs />
public override bool Equals(object obj)
{
if (obj is null)
{
return false;
}
if (ReferenceEquals(this, obj))
{
return true;
}
return Equals(obj as DnsQuerySettings);
}
/// <inheritdocs />
public bool Equals(DnsQuerySettings other)
{
if (other == null)
{
return false;
}
if (ReferenceEquals(this, other))
{
return true;
}
return EnableAuditTrail == other.EnableAuditTrail &&
UseCache == other.UseCache &&
Recursion == other.Recursion &&
Retries == other.Retries &&
ThrowDnsErrors == other.ThrowDnsErrors &&
UseRandomNameServer == other.UseRandomNameServer &&
ContinueOnDnsError == other.ContinueOnDnsError &&
ContinueOnEmptyResponse == other.ContinueOnEmptyResponse &&
Timeout.Equals(other.Timeout) &&
UseTcpFallback == other.UseTcpFallback &&
UseTcpOnly == other.UseTcpOnly &&
ExtendedDnsBufferSize == other.ExtendedDnsBufferSize &&
RequestDnsSecRecords == other.RequestDnsSecRecords &&
CacheFailedResults == other.CacheFailedResults &&
FailedResultsCacheDuration.Equals(other.FailedResultsCacheDuration);
}
}
/// <summary>
/// The readonly version of <see cref="DnsQueryOptions"/> used to customize settings per query.
/// </summary>
public class DnsQueryAndServerSettings : DnsQuerySettings, IEquatable<DnsQueryAndServerSettings>
{
private readonly NameServer[] _endpoints;
private readonly Random _rnd = new();
/// <summary>
/// Gets a collection of name servers which should be used to query.
/// </summary>
public IReadOnlyList<NameServer> NameServers => _endpoints;
/// <summary>
/// Creates a new instance of <see cref="DnsQueryAndServerSettings"/>.
/// </summary>
public DnsQueryAndServerSettings(DnsQueryAndServerOptions options)
: base(options)
{
_endpoints = options.NameServers?.ToArray() ?? new NameServer[0];
}
/// <summary>
/// Creates a new instance of <see cref="DnsQueryAndServerSettings"/>.
/// </summary>
public DnsQueryAndServerSettings(DnsQueryAndServerOptions options, IReadOnlyCollection<NameServer> overrideServers)
: this(options)
{
_endpoints = overrideServers?.ToArray() ?? throw new ArgumentNullException(nameof(overrideServers));
}
/// <inheritdocs />
public override bool Equals(object obj)
{
if (obj is null)
{
return false;
}
if (ReferenceEquals(this, obj))
{
return true;
}
return Equals(obj as DnsQueryAndServerSettings);
}
/// <inheritdocs />
public bool Equals(DnsQueryAndServerSettings other)
{
if (other == null)
{
return false;
}
if (ReferenceEquals(this, other))
{
return true;
}
return NameServers.SequenceEqual(other.NameServers)
&& base.Equals(other);
}
internal IReadOnlyList<NameServer> ShuffleNameServers()
{
if (_endpoints.Length > 1 && UseRandomNameServer)
{
var servers = _endpoints.ToArray();
for (var i = servers.Length; i > 0; i--)
{
#pragma warning disable CA5394 // Do not use insecure randomness
var j = _rnd.Next(0, i);
#pragma warning restore CA5394 // Do not use insecure randomness
var temp = servers[j];
servers[j] = servers[i - 1];
servers[i - 1] = temp;
}
return servers;
}
return NameServers;
}
}
/// <summary>
/// The readonly version of <see cref="LookupClientOptions"/> used as default settings in <see cref="LookupClient"/>.
/// </summary>
public class LookupClientSettings : DnsQueryAndServerSettings, IEquatable<LookupClientSettings>
{
/// <summary>
/// Creates a new instance of <see cref="LookupClientSettings"/>.
/// </summary>
public LookupClientSettings(LookupClientOptions options)
: base(options)
{
if (options is null)
{
throw new ArgumentNullException(nameof(options));
}
MinimumCacheTimeout = options.MinimumCacheTimeout;
MaximumCacheTimeout = options.MaximumCacheTimeout;
}
internal LookupClientSettings(LookupClientOptions options, IReadOnlyCollection<NameServer> overrideServers)
: base(options, overrideServers)
{
MinimumCacheTimeout = options.MinimumCacheTimeout;
MaximumCacheTimeout = options.MaximumCacheTimeout;
}
/// <summary>
/// Gets a <see cref="TimeSpan"/> which can override the TTL of a resource record in case the
/// TTL of the record is lower than this minimum value.
/// Default is <c>Null</c>.
/// <para>
/// This is useful in cases where the server returns records with zero TTL.
/// </para>
/// </summary>
/// <remarks>
/// This setting gets ignored in case <see cref="DnsQueryOptions.UseCache"/> is set to <c>False</c>.
/// The maximum value is 24 days or <see cref="Timeout.Infinite"/>.
/// </remarks>
public TimeSpan? MinimumCacheTimeout { get; }
/// <summary>
/// Gets a <see cref="TimeSpan"/> which can override the TTL of a resource record in case the
/// TTL of the record is higher than this maximum value.
/// Default is <c>Null</c>.
/// </summary>
/// <remarks>
/// This setting gets ignored in case <see cref="DnsQueryOptions.UseCache"/> is set to <c>False</c>.
/// The maximum value is 24 days.
/// Setting it to <see cref="Timeout.Infinite"/> would be equal to not providing a value.
/// </remarks>
public TimeSpan? MaximumCacheTimeout { get; }
/// <inheritdocs />
public override bool Equals(object obj)
{
if (obj is null)
{
return false;
}
if (ReferenceEquals(this, obj))
{
return true;
}
return Equals(obj as LookupClientSettings);
}
/// <inheritdocs />
public bool Equals(LookupClientSettings other)
{
if (other == null)
{
return false;
}
if (ReferenceEquals(this, other))
{
return true;
}
return Equals(MinimumCacheTimeout, other.MinimumCacheTimeout)
&& Equals(MaximumCacheTimeout, other.MaximumCacheTimeout)
&& base.Equals(other);
}
}
#pragma warning restore CS0659 // Type overrides Object.Equals(object o) but does not override Object.GetHashCode()
}