Fix body-writer exception causes hang

A sufficiently complex body-writer may not be able to complete writing
the body, and the only practical approach is to throw an exception.

Exceptions are normally thrown from body-writers when the socket is
closed by the remote peer.

If a Raw response body-writer throws an exception before completing the
body the http session will be left out of sync and will hang
indefinitely waiting to read the next request. The fix results in the
socket being closed and not attempting to read the next request when an
error occurs. If a content-length is provided then the network error
can be detected by the remote peer, otherwise a truncated body is
returned to the client.

Author: Stuart Espey

XCode/Sources/HttpServerIO.swift

@@ -130,6 +130,16 @@ open class HttpServerIO {
                 }
             } catch {
                 print("Failed to send response: \(error)")
+                /*
+                    The bodyWriter threw an exception, this could be because the socket is closed, in
+                    which case we fail when we attempt to read from the socket again, or it could be
+                    because the bodyWriter was unable to finish writing the body, session will be out
+                    of sync. If we kept the connection alive, then the client will be waiting for the
+                    remainder of the body until it gives up, and we'll never get the next request.
+
+                    Ideal action is to possibly abruptly close the connection.
+                 */
+                break
             }
             if let session = response.socketSession() {
                 delegate?.socketConnectionReceived(socket)

XCode/Swifter.xcodeproj/project.pbxproj

@@ -110,6 +110,9 @@
 		7CDAB8131BE2A1D400C8A977 /* Main.storyboard in Resources */ = {isa = PBXBuildFile; fileRef = 7CDAB80D1BE2A1D400C8A977 /* Main.storyboard */; };
 		7CDAB8141BE2A1D400C8A977 /* Images.xcassets in Resources */ = {isa = PBXBuildFile; fileRef = 7CDAB80F1BE2A1D400C8A977 /* Images.xcassets */; };
 		7CDAB8161BE2A1D400C8A977 /* ViewController.swift in Sources */ = {isa = PBXBuildFile; fileRef = 7CDAB8111BE2A1D400C8A977 /* ViewController.swift */; };
+		AB83D32D2919F84500D4D434 /* ServerRawResponseTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = AB83D32C2919F84500D4D434 /* ServerRawResponseTests.swift */; };
+		AB83D32E2919F84500D4D434 /* ServerRawResponseTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = AB83D32C2919F84500D4D434 /* ServerRawResponseTests.swift */; };
+		AB83D32F2919F84500D4D434 /* ServerRawResponseTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = AB83D32C2919F84500D4D434 /* ServerRawResponseTests.swift */; };
 /* End PBXBuildFile section */
 
 /* Begin PBXContainerItemProxy section */
@@ -222,6 +225,7 @@
 		7CDAB80F1BE2A1D400C8A977 /* Images.xcassets */ = {isa = PBXFileReference; lastKnownFileType = folder.assetcatalog; path = Images.xcassets; sourceTree = "<group>"; };
 		7CDAB8101BE2A1D400C8A977 /* Info.plist */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = text.plist.xml; path = Info.plist; sourceTree = "<group>"; };
 		7CDAB8111BE2A1D400C8A977 /* ViewController.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = ViewController.swift; sourceTree = "<group>"; };
+		AB83D32C2919F84500D4D434 /* ServerRawResponseTests.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = ServerRawResponseTests.swift; sourceTree = "<group>"; };
 /* End PBXFileReference section */
 
 /* Begin PBXFrameworksBuildPhase section */
@@ -429,6 +433,7 @@
 				0858E7F31D68BB2600491CD1 /* IOSafetyTests.swift */,
 				6A0D4511204E9988000A0726 /* MimeTypesTests.swift */,
 				0C1F3CAC2265FC470076B6F5 /* SwifterTestsHttpResponseBody.swift */,
+				AB83D32C2919F84500D4D434 /* ServerRawResponseTests.swift */,
 				7B55EC94226E0E4F00042D23 /* ServerThreadingTests.swift */,
 			);
 			path = Tests;
@@ -781,6 +786,7 @@
 				043660CD21FED35200497989 /* SwifterTestsHttpRouter.swift in Sources */,
 				047F1F02226AB9AD00909B95 /* XCTestManifests.swift in Sources */,
 				043660CE21FED35500497989 /* SwifterTestsHttpParser.swift in Sources */,
+				AB83D32E2919F84500D4D434 /* ServerRawResponseTests.swift in Sources */,
 				043660D521FED36C00497989 /* MimeTypesTests.swift in Sources */,
 				0C1F3CAE2265FC470076B6F5 /* SwifterTestsHttpResponseBody.swift in Sources */,
 				7B55EC96226E0E4F00042D23 /* ServerThreadingTests.swift in Sources */,
@@ -793,6 +799,7 @@
 			files = (
 				043660E721FED51600497989 /* PingServer.swift in Sources */,
 				043660E921FED51B00497989 /* SwifterTestsWebSocketSession.swift in Sources */,
+				AB83D32F2919F84500D4D434 /* ServerRawResponseTests.swift in Sources */,
 				043660EA21FED51E00497989 /* IOSafetyTests.swift in Sources */,
 				043660E821FED51900497989 /* SwifterTestsStringExtensions.swift in Sources */,
 				043660E521FED51100497989 /* SwifterTestsHttpRouter.swift in Sources */,
@@ -912,6 +919,7 @@
 				7C4785E91C71D15600A9FE73 /* SwifterTestsWebSocketSession.swift in Sources */,
 				043660D421FED36900497989 /* IOSafetyTests.swift in Sources */,
 				7CCD87721C660B250068099B /* SwifterTestsStringExtensions.swift in Sources */,
+				AB83D32D2919F84500D4D434 /* ServerRawResponseTests.swift in Sources */,
 				7B11AD4B21C9A8A6002F8820 /* SwifterTestsHttpRouter.swift in Sources */,
 				0C1F3CAD2265FC470076B6F5 /* SwifterTestsHttpResponseBody.swift in Sources */,
 				7B55EC95226E0E4F00042D23 /* ServerThreadingTests.swift in Sources */,

XCode/Sources/HttpParser.swift renamed to Xcode/Sources/HttpParser.swift

@@ -0,0 +1,134 @@
+//
+//  ServerRawResponseTests.swift
+//  Swifter
+//
+//  Created by Stuart Espey on 11/08/22.
+
+import XCTest
+#if os(Linux)
+import FoundationNetworking
+#endif
+@testable import Swifter
+
+class ServerRawResponseTests: XCTestCase {
+
+    public enum TestError: Error {
+        case aborted
+    }
+
+    var server: HttpServer!
+
+    override func setUp() {
+        super.setUp()
+        server = HttpServer()
+    }
+
+    override func tearDown() {
+        if server.operating {
+            server.stop()
+        }
+        server = nil
+        super.tearDown()
+    }
+
+    /**
+        Adds the handler, at the teststring path, then expects that XXX-CustomHeader is equal to testString, and the
+        body. Test should pass instantly-ish.
+
+        If expectError is true, then an error is expected, and response and body should be nil
+     */
+    func doHandlerTest( handler: @escaping (HttpRequest) -> HttpResponse, testString: String, expectError: Bool = false) {
+        let path = "/\(testString)"
+        server.GET[path] = handler
+
+        var requestExpectation: XCTestExpectation? = expectation(description: "Should handle the request quickly")
+
+        do {
+            try server.start()
+
+            DispatchQueue.global().async {
+
+                let task = URLSession.shared.executeAsyncTask(path: path) { (body, response, error ) in
+
+                    if expectError {
+                        XCTAssertNil(body)
+                        XCTAssertNil(response)
+                        XCTAssertNotNil(error)
+                    } else {
+                        XCTAssertNil(error)
+                        let response = response as? HTTPURLResponse
+                        XCTAssertNotNil(response)
+
+                        let statusCode = response?.statusCode
+                        XCTAssertNotNil(statusCode)
+                        XCTAssertEqual(statusCode, 200)
+                    #if !os(Linux)
+                        if #available(iOS 13.0, macOS 10.15, tvOS 13.0, *) {
+                            let header = response?.value(forHTTPHeaderField: "XXX-Custom-Header") ?? ""
+                            XCTAssertEqual(header, testString)
+                        }
+                    #endif
+
+                        XCTAssertEqual(body, testString.data(using: .utf8))
+                    }
+
+                    requestExpectation?.fulfill()
+                    requestExpectation = nil
+                }
+
+                task.resume()
+            }
+
+        } catch let error {
+            XCTFail("\(error)")
+        }
+
+        waitForExpectations(timeout: 5, handler: nil)
+    }
+
+    func testRawResponseWithBodyWriter() {
+
+        let testString = "normal"
+
+        let handler: ((HttpRequest) -> HttpResponse)  = { _ in
+            return HttpResponse.raw(200, "OK", ["XXX-Custom-Header": testString], {
+                try $0.write([UInt8]((testString) .utf8))
+            })
+        }
+
+        doHandlerTest(handler: handler, testString: testString)
+    }
+
+    func testFailedUnboundedResponseShouldNotHang() {
+
+        let testString = "unbounded"
+        let handler: ((HttpRequest) -> HttpResponse)  = { _ in
+            return HttpResponse.raw(200, "OK", ["XXX-Custom-Header": testString], {
+                try $0.write([UInt8]((testString) .utf8))
+
+                // simulates the body writer not being able to finish the body.
+                throw TestError.aborted
+            })
+        }
+
+        doHandlerTest(handler: handler, testString: testString)
+    }
+
+    func testFailedBoundedResponseShouldNotHang() {
+
+        let testString = "bounded"   // content-length: 7
+        let handler: ((HttpRequest) -> HttpResponse)  = { _ in
+            return HttpResponse.raw(200, "OK", [
+                "XXX-Custom-Header": testString,
+                "Content-Length": "\(testString.utf8.count+1)"  // we'll be missing one byte
+            ], {
+                try $0.write([UInt8]((testString) .utf8))
+
+                throw TestError.aborted
+            })
+        }
+
+        // because the length is known, we should trigger a network failure
+        doHandlerTest(handler: handler, testString: testString, expectError: true)
+    }
+}