niko
88 lines
4.0 KiB
C#
88 lines
4.0 KiB
C#
using System.Net;
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using System.Net.Sockets;
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namespace Campus_live_rewrite.api.server
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{
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/// <summary>
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/// Which CDN base /ns hands the client: ConfigCampus.CdnBaseUrl (its own host - needed for
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/// avatar bundles to load, see the comment there) once that host is proven to work, else
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/// ConfigCampus.CdnFallbackUrl. A CDN URL the client cannot use stops the game at "Launch
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/// validation failed" (it fetches /cdn/config/... during boot), so the switch is never
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/// taken on trust: every 5 minutes the host must (1) resolve in DNS to one of the API
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/// host's addresses and (2) answer a /cdn request with 200 over https with a certificate
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/// that validates for that name. The https check is dialled to the local Caddy (127.0.0.1)
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/// with the real hostname as SNI/Host, so it does not depend on the VPS reaching its own
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/// public IP.
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/// </summary>
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public static class CdnHost
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{
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private static volatile string _current = ConfigCampus.CdnFallbackUrl;
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private static string? _lastState;
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public static string Current => _current;
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public static void Start()
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{
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_ = Task.Run(async () =>
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{
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while (true)
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{
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try { await Probe(); }
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catch (Exception ex) { Report($"probe error: {ex.Message}", ConfigCampus.CdnFallbackUrl); }
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await Task.Delay(TimeSpan.FromMinutes(5));
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}
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});
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}
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private static async Task Probe()
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{
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var cdn = new Uri(ConfigCampus.CdnBaseUrl);
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var api = new Uri(ConfigCampus.CdnFallbackUrl);
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if (cdn.Scheme != Uri.UriSchemeHttps) { Report("CdnBaseUrl is not https (the client rejects it)", api.ToString()); return; }
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if (string.Equals(cdn.Host, api.Host, StringComparison.OrdinalIgnoreCase)) { Report("CdnBaseUrl is on the API host", ConfigCampus.CdnBaseUrl); return; }
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IPAddress[] cdnIps, apiIps;
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try { cdnIps = await Dns.GetHostAddressesAsync(cdn.Host); }
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catch (Exception ex) { Report($"{cdn.Host} does not resolve ({ex.Message.Trim()})", ConfigCampus.CdnFallbackUrl); return; }
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apiIps = await Dns.GetHostAddressesAsync(api.Host);
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if (!cdnIps.Any(a => apiIps.Contains(a)))
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{
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Report($"{cdn.Host} resolves to {string.Join(",", cdnIps.Select(a => a.ToString()))}, not this server", ConfigCampus.CdnFallbackUrl);
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return;
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}
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var handler = new SocketsHttpHandler
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{
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ConnectCallback = async (ctx, ct) =>
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{
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var s = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp) { NoDelay = true };
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try { await s.ConnectAsync(IPAddress.Loopback, cdn.Port, ct); return new NetworkStream(s, ownsSocket: true); }
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catch { s.Dispose(); throw; }
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},
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};
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using var http = new HttpClient(handler) { Timeout = TimeSpan.FromSeconds(10) };
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var probe = new Uri(cdn, cdn.AbsolutePath.TrimEnd('/') + "/config/LoadingScreenTipData");
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try
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{
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using var resp = await http.GetAsync(probe, HttpCompletionOption.ResponseHeadersRead);
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if (resp.StatusCode != HttpStatusCode.OK) { Report($"{probe} answered {(int)resp.StatusCode}", ConfigCampus.CdnFallbackUrl); return; }
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}
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catch (Exception ex)
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{
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Report($"{probe} failed over https ({(ex.InnerException ?? ex).Message.Trim()})", ConfigCampus.CdnFallbackUrl);
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return;
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}
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Report($"{cdn.Host} is live", ConfigCampus.CdnBaseUrl);
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}
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private static void Report(string why, string url)
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{
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_current = url;
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string state = url + " | " + why;
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if (state == _lastState) return;
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_lastState = state;
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Console.WriteLine($"[cdn-host] advertising {url} - {why}");
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}
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}
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}
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