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152 lines
5.7 KiB
152 lines
5.7 KiB
// Copyright (c) 2019, 2020, Oracle and/or its affiliates. All rights reserved.
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//
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// This program is free software; you can redistribute it and/or modify
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// it under the terms of the GNU General Public License, version 2.0, as
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// published by the Free Software Foundation.
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//
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// This program is also distributed with certain software (including
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// but not limited to OpenSSL) that is licensed under separate terms,
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// as designated in a particular file or component or in included license
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// documentation. The authors of MySQL hereby grant you an
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// additional permission to link the program and your derivative works
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// with the separately licensed software that they have included with
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// MySQL.
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//
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// Without limiting anything contained in the foregoing, this file,
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// which is part of MySQL Connector/NET, is also subject to the
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// Universal FOSS Exception, version 1.0, a copy of which can be found at
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// http://oss.oracle.com/licenses/universal-foss-exception.
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//
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// This program is distributed in the hope that it will be useful, but
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// WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
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// See the GNU General Public License, version 2.0, for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with this program; if not, write to the Free Software Foundation, Inc.,
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// 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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using Ubiety.Dns.Core;
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using System;
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using System.Collections.Generic;
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using System.Linq;
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using Ubiety.Dns.Core.Common;
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using MySql.Data.MySqlClient;
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using Sog.Properties;
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namespace MySql.Data.Common
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{
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/// <summary>
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/// DNS resolver that runs queries against a server.
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/// </summary>
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internal static class DnsResolver
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{
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// Resolver object that looks up for DNS SRV records.
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private static Resolver _resolver;
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// DNS domain.
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internal static string ServiceName { get; private set; }
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/// <summary>
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/// Initializes a new instance of the <see cref="Ubiety.Dns.Core.Resolver"/> class.
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/// </summary>
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internal static void CreateResolver(string serviceName)
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{
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_resolver = new Resolver
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{
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Recursion = true,
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UseCache = true,
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Retries = 3,
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TransportType = TransportType.Udp
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};
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ServiceName = serviceName;
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}
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/// <summary>
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/// Gets the DNS SVR records of the service name that is provided.
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/// </summary>
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/// <returns>A list of <see cref="DnsSrvRecord"/>s sorted as described in RFC2782.</returns>
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internal static List<DnsSrvRecord> GetDnsSrvRecords(string serviceName)
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{
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if (_resolver == null)
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{
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CreateResolver(serviceName);
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}
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List<DnsSrvRecord> records = new List<DnsSrvRecord>();
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const QuestionType qType = QuestionType.SRV;
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const QuestionClass qClass = QuestionClass.IN;
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Response response = _resolver.Query(ServiceName, qType, qClass);
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#pragma warning disable CS0618 // “Response.RecordSrv”已过时:“Use GetRecords<T> instead.”
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foreach (var record in response.RecordSrv)
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#pragma warning restore CS0618 // “Response.RecordSrv”已过时:“Use GetRecords<T> instead.”
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{
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records.Add(record);
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}
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if (records.Count > 0)
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{
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Reset();
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return SortSrvRecords(records);
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}
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else
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{
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throw new MySqlException(string.Format(Resources.DnsSrvNoHostsAvailable, ServiceName));
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}
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}
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/// <summary>
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/// Sorts a list of DNS SRV records according to the sorting rules described in RFC2782.
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/// </summary>
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/// <param name="srvRecords">List of <see cref="DnsSrvRecord"/>s to sort.</param>
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/// <returns>A new list of sorted <see cref="DnsSrvRecord"/>s.</returns>
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internal static List<DnsSrvRecord> SortSrvRecords(List<DnsSrvRecord> srvRecords)
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{
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srvRecords.Sort(new DnsSrvRecord());
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Random random = new Random();
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List<DnsSrvRecord> srvRecordsSortedRfc2782 = new List<DnsSrvRecord>();
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List<int> priorities = srvRecords.Select(s => s.Priority).Distinct().ToList();
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foreach (int priority in priorities)
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{
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List<DnsSrvRecord> srvRecordsSamePriority = srvRecords.Where(r => r.Priority == priority).ToList();
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while (srvRecordsSamePriority.Count > 1)
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{
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int recCount = srvRecordsSamePriority.Count;
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int sumOfWeights = 0;
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int[] weights = new int[recCount];
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for (int i = 0; i < recCount; i++)
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{
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sumOfWeights += srvRecordsSamePriority[i].Weight;
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weights[i] = sumOfWeights;
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}
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int selection = random.Next(sumOfWeights + 1);
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int pos = 0;
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for (; pos < recCount && weights[pos] < selection; pos++) { }
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srvRecordsSortedRfc2782.Add(srvRecordsSamePriority[pos]);
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srvRecordsSamePriority.RemoveAt(pos);
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}
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srvRecordsSortedRfc2782.Add(srvRecordsSamePriority[0]);
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}
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return srvRecordsSortedRfc2782;
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}
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/// <summary>
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/// Resets the DnsSrvResolver
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/// </summary>
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private static void Reset()
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{
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if (_resolver != null)
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{
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_resolver = null;
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}
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}
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}
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}
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