Add support for forwarding headers

src/FrameProcessor/Program.cs

@@ -1,3 +1,4 @@
+using System.Net;
 using FrameProcessor.Concurrency;
 using FrameProcessor.Configuration;
 using FrameProcessor.ImagePipeline;
@@ -5,10 +6,13 @@ using FrameProcessor.Middleware;
 using FrameProcessor.Mqtt;
 using FrameProcessor.Storage;
 using FrameProcessor.UrlFetch;
+using Microsoft.AspNetCore.HttpOverrides;
 using Microsoft.AspNetCore.Mvc.ModelBinding;
 using Microsoft.Extensions.Options;
 using Microsoft.OpenApi;
 using Serilog;
+using AspForwardedHeadersOptions = Microsoft.AspNetCore.Builder.ForwardedHeadersOptions;
+using ForwardedHeadersOptions = FrameProcessor.Configuration.ForwardedHeadersOptions;
 
 var builder = WebApplication.CreateBuilder(args);
 
@@ -135,6 +139,9 @@ builder.Services.AddOptions<ApiKeyOptions>()
     .ValidateDataAnnotations()
     .ValidateOnStart();
 
+builder.Services.AddOptions<ForwardedHeadersOptions>()
+    .Bind(builder.Configuration.GetSection(ForwardedHeadersOptions.SectionName));
+
 // FramesOptions is bound but not validated via the options pipeline so that
 // IOptionsMonitor<FramesOptions> can fire OnChange with invalid content during
 // hot-reload without throwing. FramesRegistry takes responsibility for both
@@ -169,6 +176,25 @@ var app = builder.Build();
 // Eagerly resolve FramesRegistry so an invalid frames.json fails startup fast.
 _ = app.Services.GetRequiredService<FramesRegistry>();
 
+// Honor X-Forwarded-Proto/Host from the reverse proxy so generated URLs
+// (OpenAPI, Swagger UI) use the externally-visible scheme and host.
+var proxyConfig = app.Services.GetRequiredService<IOptions<ForwardedHeadersOptions>>().Value;
+var forwardedHeadersOptions = new AspForwardedHeadersOptions
+{
+    ForwardedHeaders = ForwardedHeaders.XForwardedProto | ForwardedHeaders.XForwardedHost,
+};
+forwardedHeadersOptions.KnownIPNetworks.Clear();
+forwardedHeadersOptions.KnownProxies.Clear();
+foreach (var network in proxyConfig.KnownNetworks)
+{
+    forwardedHeadersOptions.KnownIPNetworks.Add(System.Net.IPNetwork.Parse(network));
+}
+foreach (var proxy in proxyConfig.KnownProxies)
+{
+    forwardedHeadersOptions.KnownProxies.Add(IPAddress.Parse(proxy));
+}
+app.UseForwardedHeaders(forwardedHeadersOptions);
+
 app.MapOpenApi();
 app.UseSwaggerUI(options =>
 {