110 lines
3.9 KiB
C#
110 lines
3.9 KiB
C#
using DNS.Client;
|
||
using DNS.Protocol;
|
||
using Microsoft.Extensions.Caching.Memory;
|
||
using Microsoft.Extensions.Logging;
|
||
using System;
|
||
using System.Linq;
|
||
using System.Net;
|
||
using System.Threading;
|
||
using System.Threading.Tasks;
|
||
|
||
namespace FastGithub.DomainResolve
|
||
{
|
||
/// <summary>
|
||
/// 域名解析器
|
||
/// </summary>
|
||
sealed class DomainResolver : IDomainResolver
|
||
{
|
||
private readonly IMemoryCache memoryCache;
|
||
private readonly FastGithubConfig fastGithubConfig;
|
||
private readonly ILogger<DomainResolver> logger;
|
||
private readonly TimeSpan cacheTimeSpan = TimeSpan.FromMinutes(1d);
|
||
|
||
/// <summary>
|
||
/// 域名解析器
|
||
/// </summary>
|
||
/// <param name="memoryCache"></param>
|
||
/// <param name="fastGithubConfig"></param>
|
||
/// <param name="logger"></param>
|
||
public DomainResolver(
|
||
IMemoryCache memoryCache,
|
||
FastGithubConfig fastGithubConfig,
|
||
ILogger<DomainResolver> logger)
|
||
{
|
||
this.memoryCache = memoryCache;
|
||
this.fastGithubConfig = fastGithubConfig;
|
||
this.logger = logger;
|
||
}
|
||
|
||
/// <summary>
|
||
/// 解析指定的域名
|
||
/// </summary>
|
||
/// <param name="domain"></param>
|
||
/// <returns></returns>
|
||
/// <exception cref="FastGithubException"></exception>
|
||
public Task<IPAddress> ResolveAsync(string domain, CancellationToken cancellationToken)
|
||
{
|
||
// 缓存以避免做不必要的并发查询
|
||
var key = $"{nameof(DomainResolver)}:{domain}";
|
||
return this.memoryCache.GetOrCreateAsync(key, e =>
|
||
{
|
||
e.SetAbsoluteExpiration(this.cacheTimeSpan);
|
||
return this.LookupAsync(domain, cancellationToken);
|
||
});
|
||
}
|
||
|
||
/// <summary>
|
||
/// 查找ip
|
||
/// </summary>
|
||
/// <param name="domain"></param>
|
||
/// <param name="cancellationToken"></param>
|
||
/// <returns></returns>
|
||
/// <exception cref="FastGithubException">
|
||
private async Task<IPAddress> LookupAsync(string domain, CancellationToken cancellationToken)
|
||
{
|
||
var pureDns = this.fastGithubConfig.PureDns;
|
||
var fastDns = this.fastGithubConfig.FastDns;
|
||
|
||
try
|
||
{
|
||
return await LookupCoreAsync(pureDns, domain, cancellationToken);
|
||
}
|
||
catch (Exception)
|
||
{
|
||
this.logger.LogTrace($"由于{pureDns}解析{domain}失败，本次使用{fastDns}");
|
||
return await LookupCoreAsync(fastDns, domain, cancellationToken);
|
||
}
|
||
}
|
||
|
||
/// <summary>
|
||
/// 查找ip
|
||
/// </summary>
|
||
/// <param name="dns"></param>
|
||
/// <param name="domain"></param>
|
||
/// <param name="cancellationToken"></param>
|
||
/// <returns></returns>
|
||
private async Task<IPAddress> LookupCoreAsync(IPEndPoint dns, string domain, CancellationToken cancellationToken)
|
||
{
|
||
var dnsClient = new DnsClient(dns);
|
||
using var timeoutTokenSource = new CancellationTokenSource(TimeSpan.FromSeconds(1d));
|
||
using var linkedTokenSource = CancellationTokenSource.CreateLinkedTokenSource(cancellationToken, timeoutTokenSource.Token);
|
||
|
||
var addresses = await dnsClient.Lookup(domain, RecordType.A, linkedTokenSource.Token);
|
||
var address = addresses?.FirstOrDefault();
|
||
if (address == null)
|
||
{
|
||
throw new FastGithubException($"dns{dns}解析不到{domain}的ip");
|
||
}
|
||
|
||
// 受干扰的dns，常常返回127.0.0.1来阻断请求
|
||
if (address.Equals(IPAddress.Loopback))
|
||
{
|
||
throw new FastGithubException($"dns{dns}被污染，解析{domain}为{address}");
|
||
}
|
||
|
||
this.logger.LogInformation($"[{domain}->{address}]");
|
||
return address;
|
||
}
|
||
}
|
||
}
|