104 lines
3.7 KiB
C#
104 lines
3.7 KiB
C#
using DNS.Client;
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using DNS.Client.RequestResolver;
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using DNS.Protocol;
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using DNS.Protocol.ResourceRecords;
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using Microsoft.Extensions.Caching.Memory;
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using Microsoft.Extensions.Logging;
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using Microsoft.Extensions.Options;
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using System;
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using System.Collections.Concurrent;
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using System.Linq;
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using System.Net;
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using System.Threading;
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using System.Threading.Tasks;
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namespace FastGithub.DomainResolve
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{
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/// <summary>
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/// DNS客户端
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/// </summary>
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sealed class DnsClient
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{
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private readonly ILogger<DnsClient> logger;
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private readonly ConcurrentDictionary<string, SemaphoreSlim> semaphoreSlims = new();
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private readonly IMemoryCache dnsCache = new MemoryCache(Options.Create(new MemoryCacheOptions()));
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private readonly TimeSpan dnsExpiration = TimeSpan.FromMinutes(2d);
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private readonly int resolveTimeout = (int)TimeSpan.FromSeconds(2d).TotalMilliseconds;
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/// <summary>
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/// DNS客户端
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/// </summary>
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/// <param name="logger"></param>
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public DnsClient(ILogger<DnsClient> logger)
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{
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this.logger = logger;
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}
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/// <summary>
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/// 解析域名
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/// </summary>
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/// <param name="dns"></param>
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/// <param name="domain"></param>
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/// <param name="cancellationToken"></param>
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/// <returns></returns>
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public async Task<IPAddress[]> LookupAsync(IPEndPoint dns, string domain, CancellationToken cancellationToken = default)
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{
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var key = $"{dns}:{domain}";
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var semaphore = this.semaphoreSlims.GetOrAdd(key, _ => new SemaphoreSlim(1, 1));
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await semaphore.WaitAsync(CancellationToken.None);
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try
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{
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if (this.dnsCache.TryGetValue<IPAddress[]>(key, out var value) == false)
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{
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value = await this.LookupCoreAsync(dns, domain, cancellationToken);
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this.dnsCache.Set(key, value, this.dnsExpiration);
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var items = string.Join(", ", value.Select(item => item.ToString()));
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this.logger.LogInformation($"{dns}：{domain}->[{items}]");
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}
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return value;
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}
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catch (Exception ex)
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{
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this.logger.LogWarning($"{dns}无法解析{domain}：{ex.Message}");
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return Array.Empty<IPAddress>();
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}
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finally
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{
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semaphore.Release();
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}
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}
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/// <summary>
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/// 解析域名
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/// </summary>
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/// <param name="dns"></param>
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/// <param name="domain"></param>
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/// <param name="cancellationToken"></param>
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/// <returns></returns>
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private async Task<IPAddress[]> LookupCoreAsync(IPEndPoint dns, string domain, CancellationToken cancellationToken = default)
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{
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if (domain == "localhost")
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{
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return new[] { IPAddress.Loopback };
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}
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var resolver = dns.Port == 53
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? (IRequestResolver)new TcpRequestResolver(dns)
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: new UdpRequestResolver(dns, new TcpRequestResolver(dns), this.resolveTimeout);
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var request = new Request
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{
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RecursionDesired = true,
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OperationCode = OperationCode.Query
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};
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request.Questions.Add(new Question(new Domain(domain), RecordType.A));
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var clientRequest = new ClientRequest(resolver, request);
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var response = await clientRequest.Resolve(cancellationToken);
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return response.AnswerRecords.OfType<IPAddressResourceRecord>().Select(item => item.IPAddress).ToArray();
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}
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}
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}
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