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- /*
- Technitium DNS Server
- Copyright (C) 2024 Shreyas Zare (shreyas@technitium.com)
- This program is free software: you can redistribute it and/or modify
- it under the terms of the GNU General Public License as published by
- the Free Software Foundation, either version 3 of the License, or
- (at your option) any later version.
- This program is distributed in the hope that it will be useful,
- but WITHOUT ANY WARRANTY; without even the implied warranty of
- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
- GNU General Public License for more details.
- You should have received a copy of the GNU General Public License
- along with this program. If not, see <http://www.gnu.org/licenses/>.
- */
- using DnsServerCore.ApplicationCommon;
- using System;
- using System.Collections.Generic;
- using System.Net;
- using System.Security.Cryptography;
- using System.Text.Json;
- using System.Threading.Tasks;
- using TechnitiumLibrary.Net.Dns;
- using TechnitiumLibrary.Net.Dns.ResourceRecords;
- namespace WeightedRoundRobin
- {
- public sealed class Address : IDnsApplication, IDnsAppRecordRequestHandler
- {
- #region IDisposable
- public void Dispose()
- {
- //do nothing
- }
- #endregion
- #region public
- public Task InitializeAsync(IDnsServer dnsServer, string config)
- {
- return Task.CompletedTask;
- }
- public Task<DnsDatagram> ProcessRequestAsync(DnsDatagram request, IPEndPoint remoteEP, DnsTransportProtocol protocol, bool isRecursionAllowed, string zoneName, string appRecordName, uint appRecordTtl, string appRecordData)
- {
- DnsQuestionRecord question = request.Question[0];
- if (!question.Name.Equals(appRecordName, StringComparison.OrdinalIgnoreCase) && !appRecordName.StartsWith('*'))
- return Task.FromResult<DnsDatagram>(null);
- string jsonPropertyName;
- switch (question.Type)
- {
- case DnsResourceRecordType.A:
- jsonPropertyName = "ipv4Addresses";
- break;
- case DnsResourceRecordType.AAAA:
- jsonPropertyName = "ipv6Addresses";
- break;
- default:
- return Task.FromResult<DnsDatagram>(null);
- }
- List<WeightedAddress> addresses;
- int totalWeight = 0;
- using (JsonDocument jsonDocument = JsonDocument.Parse(appRecordData))
- {
- JsonElement jsonAppRecordData = jsonDocument.RootElement;
- if (!jsonAppRecordData.TryGetProperty(jsonPropertyName, out JsonElement jsonAddresses) || (jsonAddresses.ValueKind == JsonValueKind.Null))
- return Task.FromResult<DnsDatagram>(null);
- addresses = new List<WeightedAddress>(jsonAddresses.GetArrayLength());
- foreach (JsonElement jsonAddressEntry in jsonAddresses.EnumerateArray())
- {
- if (jsonAddressEntry.TryGetProperty("enabled", out JsonElement jsonEnabled) && (jsonEnabled.ValueKind != JsonValueKind.Null) && !jsonEnabled.GetBoolean())
- continue;
- if (!jsonAddressEntry.TryGetProperty("address", out JsonElement jsonAddress) || (jsonAddress.ValueKind == JsonValueKind.Null) || !IPAddress.TryParse(jsonAddress.GetString(), out IPAddress address))
- continue;
- if (!jsonAddressEntry.TryGetProperty("weight", out JsonElement jsonWeight) || (jsonWeight.ValueKind == JsonValueKind.Null))
- continue;
- int weight = jsonWeight.GetInt32();
- if (weight < 1)
- continue;
- addresses.Add(new WeightedAddress() { Address = address, Weight = weight });
- totalWeight += weight;
- }
- }
- if (addresses.Count == 0)
- return Task.FromResult<DnsDatagram>(null);
- int randomSelection = RandomNumberGenerator.GetInt32(1, 101);
- int rangeFrom;
- int rangeTo = 0;
- DnsResourceRecord answer = null;
- for (int i = 0; i < addresses.Count; i++)
- {
- rangeFrom = rangeTo + 1;
- if (i == addresses.Count - 1)
- rangeTo = 100;
- else
- rangeTo += addresses[i].Weight * 100 / totalWeight;
- if ((rangeFrom <= randomSelection) && (randomSelection <= rangeTo))
- {
- switch (question.Type)
- {
- case DnsResourceRecordType.A:
- answer = new DnsResourceRecord(question.Name, question.Type, DnsClass.IN, appRecordTtl, new DnsARecordData(addresses[i].Address));
- break;
- case DnsResourceRecordType.AAAA:
- answer = new DnsResourceRecord(question.Name, question.Type, DnsClass.IN, appRecordTtl, new DnsAAAARecordData(addresses[i].Address));
- break;
- default:
- throw new InvalidOperationException();
- }
- break;
- }
- }
- if (answer is null)
- throw new InvalidOperationException();
- return Task.FromResult(new DnsDatagram(request.Identifier, true, request.OPCODE, true, false, request.RecursionDesired, isRecursionAllowed, false, false, DnsResponseCode.NoError, request.Question, new DnsResourceRecord[] { answer }));
- }
- #endregion
- #region properties
- public string Description
- { get { return "Returns an A or AAAA record using weighted round-robin load balancing."; } }
- public string ApplicationRecordDataTemplate
- {
- get
- {
- return @"{
- ""ipv4Addresses"": [
- {
- ""address"": ""1.1.1.1"",
- ""weight"": 5,
- ""enabled"": true
- },
- {
- ""address"": ""2.2.2.2"",
- ""weight"": 3,
- ""enabled"": true
- }
- ],
- ""ipv6Addresses"": [
- {
- ""address"": ""::1"",
- ""weight"": 2,
- ""enabled"": true
- },
- {
- ""address"": ""::2"",
- ""weight"": 3,
- ""enabled"": true
- }
- ]
- }";
- }
- }
- #endregion
- struct WeightedAddress
- {
- public IPAddress Address;
- public int Weight;
- }
- }
- }
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