[Tests] Add some basic IPv6 tests

Tests/AsyncHTTPClientTests/HTTPClientTestUtils.swift

@@ -17,6 +17,7 @@ import Foundation
 import Logging
 import NIOConcurrencyHelpers
 import NIOCore
+import NIOEmbedded
 import NIOHPACK
 import NIOHTTP1
 import NIOHTTP2
@@ -46,6 +47,18 @@ func getDefaultEventLoopGroup(numberOfThreads: Int) -> EventLoopGroup {
     return MultiThreadedEventLoopGroup(numberOfThreads: numberOfThreads)
 }
 
+let canBindIPv6Loopback: Bool = {
+    let elg = MultiThreadedEventLoopGroup(numberOfThreads: 1)
+    defer { try! elg.syncShutdownGracefully() }
+    let serverChannel = try? ServerBootstrap(group: elg)
+        .serverChannelOption(ChannelOptions.socket(SocketOptionLevel(SOL_SOCKET), SO_REUSEADDR), value: 1)
+        .bind(host: "::1", port: 0)
+        .wait()
+    let didBind = (serverChannel != nil)
+    try! serverChannel?.close().wait()
+    return didBind
+}()
+
 class TestHTTPDelegate: HTTPClientResponseDelegate {
     typealias Response = Void
 
@@ -266,6 +279,7 @@ internal final class HTTPBin<RequestHandler: ChannelInboundHandler> where
     enum BindTarget {
         case unixDomainSocket(String)
         case localhostIPv4RandomPort
+        case localhostIPv6RandomPort
     }
 
     enum Mode {
@@ -331,6 +345,8 @@ internal final class HTTPBin<RequestHandler: ChannelInboundHandler> where
         switch bindTarget {
         case .localhostIPv4RandomPort:
             socketAddress = try! SocketAddress(ipAddress: "127.0.0.1", port: 0)
+        case .localhostIPv6RandomPort:
+            socketAddress = try! SocketAddress(ipAddress: "::1", port: 0)
         case .unixDomainSocket(let path):
             socketAddress = try! SocketAddress(unixDomainSocketPath: path)
         }

Tests/AsyncHTTPClientTests/HTTPClientTests+XCTest.swift

@@ -38,6 +38,8 @@ extension HTTPClientTests {
             ("testGetHttps", testGetHttps),
             ("testGetHttpsWithIP", testGetHttpsWithIP),
             ("testGetHTTPSWorksOnMTELGWithIP", testGetHTTPSWorksOnMTELGWithIP),
+            ("testGetHttpsWithIPv6", testGetHttpsWithIPv6),
+            ("testGetHTTPSWorksOnMTELGWithIPv6", testGetHTTPSWorksOnMTELGWithIPv6),
             ("testPostHttps", testPostHttps),
             ("testHttpRedirect", testHttpRedirect),
             ("testHttpHostRedirect", testHttpHostRedirect),

Tests/AsyncHTTPClientTests/HTTPClientTests.swift

@@ -333,6 +333,40 @@ class HTTPClientTests: XCTestCase {
         XCTAssertEqual(.ok, response.status)
     }
 
+    func testGetHttpsWithIPv6() throws {
+        try XCTSkipUnless(canBindIPv6Loopback, "Requires IPv6")
+        let localHTTPBin = HTTPBin(.http1_1(ssl: true), bindTarget: .localhostIPv6RandomPort)
+        let localClient = HTTPClient(eventLoopGroupProvider: .shared(self.clientGroup),
+                                     configuration: HTTPClient.Configuration(certificateVerification: .none))
+        defer {
+            XCTAssertNoThrow(try localClient.syncShutdown())
+            XCTAssertNoThrow(try localHTTPBin.shutdown())
+        }
+        var response: HTTPClient.Response?
+        XCTAssertNoThrow(response = try localClient.get(url: "https://[::1]:\(localHTTPBin.port)/get").wait())
+        XCTAssertEqual(.ok, response?.status)
+    }
+
+    func testGetHTTPSWorksOnMTELGWithIPv6() throws {
+        try XCTSkipUnless(canBindIPv6Loopback, "Requires IPv6")
+        // Same test as above but this one will use NIO on Sockets even on Apple platforms, just to make sure
+        // this works.
+        let group = MultiThreadedEventLoopGroup(numberOfThreads: 1)
+        defer {
+            XCTAssertNoThrow(try group.syncShutdownGracefully())
+        }
+        let localHTTPBin = HTTPBin(.http1_1(ssl: true), bindTarget: .localhostIPv6RandomPort)
+        let localClient = HTTPClient(eventLoopGroupProvider: .shared(group),
+                                     configuration: HTTPClient.Configuration(certificateVerification: .none))
+        defer {
+            XCTAssertNoThrow(try localClient.syncShutdown())
+            XCTAssertNoThrow(try localHTTPBin.shutdown())
+        }
+        var response: HTTPClient.Response?
+        XCTAssertNoThrow(response = try localClient.get(url: "https://[::1]:\(localHTTPBin.port)/get").wait())
+        XCTAssertEqual(.ok, response?.status)
+    }
+
     func testPostHttps() throws {
         let localHTTPBin = HTTPBin(.http1_1(ssl: true))
         let localClient = HTTPClient(eventLoopGroupProvider: .shared(self.clientGroup),