Add NIOTS bootstrap configurators to config

Sources/GRPCNIOTransportHTTP2TransportServices/HTTP2ClientTransport+TransportServices.swift

@@ -175,6 +175,8 @@ extension HTTP2ClientTransport.TransportServices {
         }
       }
 
+      config.clientBootstrapNWParametersConfigurator?(bootstrap)
+
       let (channel, multiplexer) = try await bootstrap.connect(to: address) { channel in
         channel.eventLoop.makeCompletedFuture {
           try channel.pipeline.syncOperations.configureGRPCClientPipeline(
@@ -215,6 +217,11 @@ extension HTTP2ClientTransport.TransportServices {
     /// Channel callbacks for debugging.
     public var channelDebuggingCallbacks: HTTP2ClientTransport.Config.ChannelDebuggingCallbacks
 
+    /// Customise the NWParameters used in the NIO Transport Services bootstrap when creating the connection channel.
+    public var clientBootstrapNWParametersConfigurator: (
+      @Sendable (NIOTSConnectionBootstrap) -> Void
+    )?
+
     /// Creates a new connection configuration.
     ///
     /// - Parameters:
@@ -223,14 +230,17 @@ extension HTTP2ClientTransport.TransportServices {
     ///   - connection: Connection configuration.
     ///   - compression: Compression configuration.
     ///   - channelDebuggingCallbacks: Channel callbacks for debugging.
+    ///   - clientBootstrapNWParametersConfigurator: Customise the NWParameters used in the NIO Transport
+    ///   Services bootstrap when creating the connection channel.
     ///
     /// - SeeAlso: ``defaults(configure:)`` and ``defaults``.
     public init(
       http2: HTTP2ClientTransport.Config.HTTP2,
       backoff: HTTP2ClientTransport.Config.Backoff,
       connection: HTTP2ClientTransport.Config.Connection,
       compression: HTTP2ClientTransport.Config.Compression,
-      channelDebuggingCallbacks: HTTP2ClientTransport.Config.ChannelDebuggingCallbacks
+      channelDebuggingCallbacks: HTTP2ClientTransport.Config.ChannelDebuggingCallbacks,
+      clientBootstrapNWParametersConfigurator: (@Sendable (NIOTSConnectionBootstrap) -> Void)?
     ) {
       self.http2 = http2
       self.connection = connection
@@ -256,7 +266,8 @@ extension HTTP2ClientTransport.TransportServices {
         backoff: .defaults,
         connection: .defaults,
         compression: .defaults,
-        channelDebuggingCallbacks: .defaults
+        channelDebuggingCallbacks: .defaults,
+        clientBootstrapNWParametersConfigurator: nil
       )
       configure(&config)
       return config

Sources/GRPCNIOTransportHTTP2TransportServices/HTTP2ServerTransport+TransportServices.swift

@@ -57,6 +57,8 @@ extension HTTP2ServerTransport {
             .tlsOptions(try NWProtocolTLS.Options(tlsConfig))
         }
 
+        config.serverBootstrapNWParametersConfigurator?(bootstrap)
+
         let serverChannel =
           try await bootstrap
           .serverChannelOption(.socketOption(.so_reuseaddr), value: 1)
@@ -164,27 +166,36 @@ extension HTTP2ServerTransport.TransportServices {
     /// Channel callbacks for debugging.
     public var channelDebuggingCallbacks: HTTP2ServerTransport.Config.ChannelDebuggingCallbacks
 
+    /// Customise the NWParameters used in the NIO Transport Services bootstrap when creating the listening channel.
+    public var serverBootstrapNWParametersConfigurator: (
+      @Sendable (NIOTSListenerBootstrap) -> Void
+    )?
+
     /// Construct a new `Config`.
     /// - Parameters:
     ///   - compression: Compression configuration.
     ///   - connection: Connection configuration.
     ///   - http2: HTTP2 configuration.
     ///   - rpc: RPC configuration.
     ///   - channelDebuggingCallbacks: Channel callbacks for debugging.
+    ///   - serverBootstrapNWParametersConfigurator: Customise the NWParameters used in the NIO Transport
+    ///   Services bootstrap when creating the listening channel.
     ///
     /// - SeeAlso: ``defaults(configure:)`` and ``defaults``.
     public init(
       compression: HTTP2ServerTransport.Config.Compression,
       connection: HTTP2ServerTransport.Config.Connection,
       http2: HTTP2ServerTransport.Config.HTTP2,
       rpc: HTTP2ServerTransport.Config.RPC,
-      channelDebuggingCallbacks: HTTP2ServerTransport.Config.ChannelDebuggingCallbacks
+      channelDebuggingCallbacks: HTTP2ServerTransport.Config.ChannelDebuggingCallbacks,
+      serverBootstrapNWParametersConfigurator: (@Sendable (NIOTSListenerBootstrap) -> Void)?
     ) {
       self.compression = compression
       self.connection = connection
       self.http2 = http2
       self.rpc = rpc
       self.channelDebuggingCallbacks = channelDebuggingCallbacks
+      self.serverBootstrapNWParametersConfigurator = serverBootstrapNWParametersConfigurator
     }
 
     public static var defaults: Self {
@@ -203,7 +214,8 @@ extension HTTP2ServerTransport.TransportServices {
         connection: .defaults,
         http2: .defaults,
         rpc: .defaults,
-        channelDebuggingCallbacks: .defaults
+        channelDebuggingCallbacks: .defaults,
+        serverBootstrapNWParametersConfigurator: nil
       )
       configure(&config)
       return config

Tests/GRPCNIOTransportHTTP2Tests/HTTP2TransportNIOTransportServicesTests.swift

@@ -20,6 +20,7 @@ import GRPCNIOTransportCore
 import GRPCNIOTransportHTTP2TransportServices
 import XCTest
 import NIOSSL
+import NIOConcurrencyHelpers
 
 final class HTTP2TransportNIOTransportServicesTests: XCTestCase {
   func testGetListeningAddress_IPv4() async throws {
@@ -207,6 +208,65 @@ final class HTTP2TransportNIOTransportServicesTests: XCTestCase {
     XCTAssertEqual(grpcTLSConfig.serverCertificateVerification, .fullVerification)
     XCTAssertEqual(grpcTLSConfig.trustRoots, .systemDefault)
   }
+
+  func testServerNWParametersConfiguratorGetsCalled() async throws {
+    let configuratorCalledCount = NIOLockedValueBox(0)
+    let transport = GRPCNIOTransportCore.HTTP2ServerTransport.TransportServices(
+      address: .ipv4(host: "0.0.0.0", port: 0),
+      transportSecurity: .plaintext,
+      config: .defaults(configure: { config in
+        config.serverBootstrapNWParametersConfigurator = { _ in
+          configuratorCalledCount.withLockedValue { $0 += 1 }
+        }
+      })
+    )
+
+    try await withThrowingDiscardingTaskGroup { group in
+      group.addTask {
+        try await transport.listen { _, _ in }
+      }
+
+      group.addTask {
+        _ = try await transport.listeningAddress
+        XCTAssertEqual(1, configuratorCalledCount.withLockedValue({ $0 }))
+        transport.beginGracefulShutdown()
+      }
+    }
+  }
+
+  func testClientNWParametersConfiguratorGetsCalled() async throws {
+    let (stream, continuation) = AsyncStream.makeStream(of: Void.self)
+
+    let clientTransport = try GRPCNIOTransportCore.HTTP2ClientTransport.TransportServices(
+      target: .ipv4(host: "0.0.0.0", port: 0),
+      transportSecurity: .plaintext,
+      config: .defaults(configure: { config in
+        config.clientBootstrapNWParametersConfigurator = { _ in
+          continuation.finish()
+        }
+      })
+    )
+
+    await withThrowingTaskGroup(of: Void.self) { group in
+      group.addTask {
+        // It doesn't matter if the connection actually fails: the configurator will run before
+        // we attempt to connect anyways.
+        try? await clientTransport.connect()
+      }
+
+      group.addTask {
+        // Timeout after a second if we haven't called the configurator closure.
+        try await Task.sleep(for: .seconds(1))
+        XCTFail("clientBootstrapNWParametersConfigurator was not called.")
+        throw CancellationError()
+      }
+
+      for await _ in stream {
+        // If/when we exit this loop, it means we have called the configurator closure
+      }
+      group.cancelAll()
+    }
+  }
 }
 
 enum HTTP2TransportNIOTransportServicesTestsError: Error {