88 lines
3.0 KiB
C#
88 lines
3.0 KiB
C#
using DNS.Client;
|
||
using Microsoft.Extensions.Caching.Memory;
|
||
using Microsoft.Extensions.Options;
|
||
using System;
|
||
using System.Linq;
|
||
using System.Net;
|
||
using System.Threading;
|
||
using System.Threading.Tasks;
|
||
|
||
namespace FastGithub.ReverseProxy
|
||
{
|
||
/// <summary>
|
||
/// 受信任的域名解析器
|
||
/// </summary>
|
||
sealed class DomainResolver
|
||
{
|
||
private readonly IMemoryCache memoryCache;
|
||
private readonly TimeSpan cacheTimeSpan = TimeSpan.FromSeconds(10d);
|
||
private readonly IOptionsMonitor<FastGithubOptions> options;
|
||
|
||
/// <summary>
|
||
/// 受信任的域名解析器
|
||
/// </summary>
|
||
/// <param name="options"></param>
|
||
public DomainResolver(
|
||
IMemoryCache memoryCache,
|
||
IOptionsMonitor<FastGithubOptions> options)
|
||
{
|
||
this.memoryCache = memoryCache;
|
||
this.options = options;
|
||
}
|
||
|
||
/// <summary>
|
||
/// 解析指定的域名
|
||
/// </summary>
|
||
/// <param name="domain"></param>
|
||
/// <returns></returns>
|
||
public async Task<IPAddress> ResolveAsync(string domain, CancellationToken cancellationToken)
|
||
{
|
||
// 缓存以避免做不必要的并发查询
|
||
var key = $"domain:{domain}";
|
||
var address = await this.memoryCache.GetOrCreateAsync(key, e =>
|
||
{
|
||
e.SetAbsoluteExpiration(this.cacheTimeSpan);
|
||
return this.LookupAsync(domain, cancellationToken);
|
||
});
|
||
return address;
|
||
}
|
||
|
||
/// <summary>
|
||
/// 查找ip
|
||
/// </summary>
|
||
/// <param name="domain"></param>
|
||
/// <param name="cancellationToken"></param>
|
||
/// <returns></returns>
|
||
private async Task<IPAddress> LookupAsync(string domain, CancellationToken cancellationToken)
|
||
{
|
||
var endpoint = this.options.CurrentValue.TrustedDns.ToIPEndPoint();
|
||
try
|
||
{
|
||
var dnsClient = new DnsClient(endpoint);
|
||
var addresses = await dnsClient.Lookup(domain, DNS.Protocol.RecordType.A, cancellationToken);
|
||
var address = addresses?.FirstOrDefault();
|
||
if (address == null)
|
||
{
|
||
throw new FastGithubException($"dns({endpoint})：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
|
||
// 如果解析到的ip为本机ip，会产生反向代理请求死循环
|
||
if (address.Equals(IPAddress.Loopback))
|
||
{
|
||
throw new FastGithubException($"dns({endpoint})：解析{domain}被干扰为{address}");
|
||
}
|
||
return address;
|
||
}
|
||
catch (FastGithubException)
|
||
{
|
||
throw;
|
||
}
|
||
catch (Exception ex)
|
||
{
|
||
throw new FastGithubException($"dns({endpoint})：{ex.Message}", ex);
|
||
}
|
||
}
|
||
}
|
||
}
|