Setup rudimentary configuration validation

src/Tgstation.Server.Host/Configuration/Validators/GeneralConfigValidator.cs

@@ -0,0 +1,24 @@
+using System;
+
+using Microsoft.Extensions.Options;
+
+namespace Tgstation.Server.Host.Configuration.Validators
+{
+	/// <summary>
+	/// Configuration validator for <see cref="GeneralConfiguration"/>.
+	/// </summary>
+	sealed class GeneralConfigValidator : IValidateOptions<GeneralConfiguration>
+	{
+		/// <inheritdoc />
+		public ValidateOptionsResult Validate(string? name, GeneralConfiguration options)
+		{
+			ArgumentNullException.ThrowIfNull(options);
+
+			var metricsValidation = HostingSpecificationConfigValidator.ValidateHostingSpecifications(options.MetricsEndPoints, nameof(options.MetricsEndPoints), false);
+			if (metricsValidation.Failed)
+				return metricsValidation;
+
+			return HostingSpecificationConfigValidator.ValidateHostingSpecifications(options.ApiEndPoints, nameof(GeneralConfiguration.ApiEndPoints), true);
+		}
+	}
+}

src/Tgstation.Server.Host/Configuration/Validators/HostingSpecificationConfigValidator.cs

@@ -0,0 +1,51 @@
+using System;
+using System.Collections.Generic;
+using System.Net;
+
+using Microsoft.Extensions.Options;
+
+using Tgstation.Server.Host.Configuration;
+
+namespace Tgstation.Server.Host
+{
+	/// <summary>
+	/// Configuration validation for <see cref="HostingSpecification"/>s.
+	/// </summary>
+	static class HostingSpecificationConfigValidator
+	{
+		/// <summary>
+		/// Validate given a set of <paramref name="endPoints"/>.
+		/// </summary>
+		/// <param name="endPoints">The <see cref="HostingSpecification"/>s to validate.</param>
+		/// <param name="name">The name of the config subsection.</param>
+		/// <param name="required">If these endpoints are required.</param>
+		/// <returns>The <see cref="ValidateOptionsResult"/> for the <paramref name="endPoints"/>.</returns>
+		public static ValidateOptionsResult ValidateHostingSpecifications(IReadOnlyList<HostingSpecification> endPoints, string name, bool required)
+		{
+			ArgumentNullException.ThrowIfNull(endPoints);
+			ArgumentNullException.ThrowIfNull(name);
+
+			if (endPoints == null || endPoints.Count == 0)
+			{
+				if (!required)
+					return ValidateOptionsResult.Success;
+
+				return ValidateOptionsResult.Fail($"At least one hosting specification for {name} must be specified");
+			}
+
+			foreach (var endPoint in endPoints)
+			{
+				if (endPoint == null)
+					return ValidateOptionsResult.Fail("A hosting specification cannot be null!");
+
+				if (endPoint.Port == 0)
+					return ValidateOptionsResult.Fail($"Hosting specification port in {name} cannot be 0!");
+
+				if (endPoint.IPAddress != null && !IPAddress.TryParse(endPoint.IPAddress, out _))
+					return ValidateOptionsResult.Fail($"Could not part hosting IP address in {name}: {endPoint.IPAddress}");
+			}
+
+			return ValidateOptionsResult.Success;
+		}
+	}
+}

src/Tgstation.Server.Host/Configuration/Validators/SessionConfigValidator.cs

@@ -0,0 +1,23 @@
+using System;
+
+using Microsoft.Extensions.Options;
+
+namespace Tgstation.Server.Host.Configuration.Validators
+{
+	/// <summary>
+	/// Configuration validator for <see cref="SessionConfiguration"/>.
+	/// </summary>
+	sealed class SessionConfigValidator : IValidateOptions<SessionConfiguration>
+	{
+		/// <inheritdoc />
+		public ValidateOptionsResult Validate(string? name, SessionConfiguration options)
+		{
+			ArgumentNullException.ThrowIfNull(options);
+
+			if (options.BridgePort == 0)
+				return ValidateOptionsResult.Fail($"{nameof(SessionConfiguration.BridgePort)} cannot be zero!");
+
+			return ValidateOptionsResult.Success;
+		}
+	}
+}

src/Tgstation.Server.Host/Configuration/Validators/SwarmConfigValidator.cs

@@ -0,0 +1,29 @@
+using System;
+
+using Microsoft.Extensions.Options;
+
+namespace Tgstation.Server.Host.Configuration.Validators
+{
+	/// <summary>
+	/// Configuration validator for <see cref="SwarmConfiguration"/>.
+	/// </summary>
+	sealed class SwarmConfigValidator : IValidateOptions<SwarmConfiguration>
+	{
+		/// <inheritdoc />
+		public ValidateOptionsResult Validate(string? name, SwarmConfiguration options)
+		{
+			ArgumentNullException.ThrowIfNull(options);
+
+			if (options.PrivateKey == null)
+				return ValidateOptionsResult.Success;
+
+			if (options.UpdateRequiredNodeCount == 0)
+				return ValidateOptionsResult.Fail($"{nameof(SwarmConfiguration.UpdateRequiredNodeCount)} must be greater than 0!");
+
+			if (options.Address == null)
+				return ValidateOptionsResult.Fail($"{nameof(SwarmConfiguration.Address)} must be set to an http endpoint of this swarm service accessible from other servers in the swarm!");
+
+			return HostingSpecificationConfigValidator.ValidateHostingSpecifications(options.EndPoints, nameof(SwarmConfiguration.EndPoints), true);
+		}
+	}
+}

src/Tgstation.Server.Host/Core/Application.cs

@@ -822,6 +822,10 @@ namespace Tgstation.Server.Host.Core
 		protected override void ConfigureHostedService(IServiceCollection services)
 			=> services.AddSingleton<IHostedService>(x => x.GetRequiredService<InstanceManager>());
 
+		/// <inheritdoc />
+		protected override void UseValidatedConfig<TConfig, TValidator>(IServiceCollection services)
+			=> services.UseValidatedConfig<TConfig, TValidator>(Configuration);
+
 		/// <summary>
 		/// Configure the <paramref name="services"/> for the authentication pipeline.
 		/// </summary>

src/Tgstation.Server.Host/Extensions/ServiceCollectionExtensions.cs

@@ -165,6 +165,22 @@ namespace Tgstation.Server.Host.Extensions
 				.BindConfiguration(sectionName);
 		}
 
+		/// <summary>
+		/// Add a standard <typeparamref name="TConfig"/> binding.
+		/// </summary>
+		/// <typeparam name="TConfig">The <see langword="class"/> to bind. Must have a <see langword="public"/> const/static <see cref="string"/> field named "Section".</typeparam>
+		/// <typeparam name="TValidator">The <see cref="IValidateOptions{TOptions}"/> <see cref="Type"/> for <typeparamref name="TConfig"/>s.</typeparam>
+		/// <param name="serviceCollection">The <see cref="IServiceCollection"/> to configure.</param>
+		/// <param name="configuration">The <see cref="IConfiguration"/> containing the <typeparamref name="TConfig"/>.</param>
+		/// <returns><paramref name="serviceCollection"/>.</returns>
+		public static OptionsBuilder<TConfig> UseValidatedConfig<TConfig, TValidator>(this IServiceCollection serviceCollection, IConfiguration configuration)
+			where TConfig : class
+			where TValidator : class, IValidateOptions<TConfig>
+		{
+			serviceCollection.AddSingleton<IValidateOptions<TConfig>, TValidator>();
+			return UseStandardConfig<TConfig>(serviceCollection, configuration);
+		}
+
 		/// <summary>
 		/// Clear previous providers and configure logging.
 		/// </summary>

src/Tgstation.Server.Host/Setup/SetupApplication.cs

@@ -3,9 +3,12 @@
 using Microsoft.Extensions.Configuration;
 using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.Hosting;
+using Microsoft.Extensions.Options;
+
 using Serilog.Events;
 
 using Tgstation.Server.Host.Configuration;
+using Tgstation.Server.Host.Configuration.Validators;
 using Tgstation.Server.Host.Database;
 using Tgstation.Server.Host.Extensions;
 using Tgstation.Server.Host.IO;
@@ -56,14 +59,14 @@ namespace Tgstation.Server.Host.Setup
 			services.AddSingleton<IAsyncDelayer, AsyncDelayer>();
 
 			// these configs are what's injected into PostSetupServices
-			services.UseStandardConfig<GeneralConfiguration>(Configuration);
+			UseValidatedConfig<GeneralConfiguration, GeneralConfigValidator>(services);
 			services.UseStandardConfig<DatabaseConfiguration>(Configuration);
 			services.UseStandardConfig<SecurityConfiguration>(Configuration);
 			services.UseStandardConfig<FileLoggingConfiguration>(Configuration);
 			services.UseStandardConfig<ElasticsearchConfiguration>(Configuration);
 			services.UseStandardConfig<InternalConfiguration>(Configuration);
-			services.UseStandardConfig<SwarmConfiguration>(Configuration);
-			services.UseStandardConfig<SessionConfiguration>(Configuration);
+			UseValidatedConfig<SwarmConfiguration, SwarmConfigValidator>(services);
+			UseValidatedConfig<SessionConfiguration, SessionConfigValidator>(services);
 
 			ConfigureHostedService(services);
 		}
@@ -77,5 +80,16 @@ namespace Tgstation.Server.Host.Setup
 			services.AddSingleton<IPostSetupServices, PostSetupServices>();
 			services.AddSingleton<IHostedService, SetupWizard>();
 		}
+
+		/// <summary>
+		/// Configures the <see cref="IHostedService"/>.
+		/// </summary>
+		/// <typeparam name="TConfig">The <see langword="class"/> to bind. Must have a <see langword="public"/> const/static <see cref="string"/> field named "Section".</typeparam>
+		/// <typeparam name="TValidator">The <see cref="IValidateOptions{TOptions}"/> <see cref="Type"/> for <typeparamref name="TConfig"/>s.</typeparam>
+		/// <param name="services">The <see cref="IServiceCollection"/> to configure.</param>
+		protected virtual void UseValidatedConfig<TConfig, TValidator>(IServiceCollection services)
+			where TConfig : class
+			where TValidator : class, IValidateOptions<TConfig>
+			=> services.UseStandardConfig<TConfig>(Configuration); // don't enable config validation during setup
 	}
 }