LibHTTP: Respect the 'Connection: close' header on keep-alive jobs

If the server responds with this header, we _must_ close the connection,
as the server is allowed to ignore the socket and not respond to
anything past that response.
Fixes some RequestServer spins.

Userland/Libraries/LibHTTP/HttpJob.cpp

@@ -43,13 +43,17 @@ void HttpJob::start(NonnullRefPtr<Core::Socket> socket)
     };
 }
 
-void HttpJob::shutdown()
+void HttpJob::shutdown(ShutdownMode mode)
 {
     if (!m_socket)
         return;
-    m_socket->on_ready_to_read = nullptr;
-    m_socket->on_connected = nullptr;
-    m_socket = nullptr;
+    if (mode == ShutdownMode::CloseSocket) {
+        m_socket->close();
+    } else {
+        m_socket->on_ready_to_read = nullptr;
+        m_socket->on_connected = nullptr;
+        m_socket = nullptr;
+    }
 }
 
 void HttpJob::register_on_ready_to_read(Function<void()> callback)

Userland/Libraries/LibHTTP/HttpJob.h

@@ -28,7 +28,7 @@ public:
     }
 
     virtual void start(NonnullRefPtr<Core::Socket>) override;
-    virtual void shutdown() override;
+    virtual void shutdown(ShutdownMode) override;
 
     Core::Socket const* socket() const { return m_socket; }
     URL url() const { return m_request.url(); }

Userland/Libraries/LibHTTP/HttpsJob.cpp

@@ -62,14 +62,18 @@ void HttpsJob::start(NonnullRefPtr<Core::Socket> socket)
     }
 }
 
-void HttpsJob::shutdown()
+void HttpsJob::shutdown(ShutdownMode mode)
 {
     if (!m_socket)
         return;
-    m_socket->on_tls_ready_to_read = nullptr;
-    m_socket->on_tls_connected = nullptr;
-    m_socket->set_on_tls_ready_to_write(nullptr);
-    m_socket = nullptr;
+    if (mode == ShutdownMode::CloseSocket) {
+        m_socket->close();
+    } else {
+        m_socket->on_tls_ready_to_read = nullptr;
+        m_socket->on_tls_connected = nullptr;
+        m_socket->set_on_tls_ready_to_write(nullptr);
+        m_socket = nullptr;
+    }
 }
 
 void HttpsJob::set_certificate(String certificate, String private_key)

Userland/Libraries/LibHTTP/HttpsJob.h

@@ -29,7 +29,7 @@ public:
     }
 
     virtual void start(NonnullRefPtr<Core::Socket>) override;
-    virtual void shutdown() override;
+    virtual void shutdown(ShutdownMode) override;
     void set_certificate(String certificate, String key);
 
     Core::Socket const* socket() const { return m_socket; }

Userland/Libraries/LibHTTP/Job.cpp

@@ -412,6 +412,10 @@ void Job::finish_up()
     m_has_scheduled_finish = true;
     auto response = HttpResponse::create(m_code, move(m_headers));
     deferred_invoke([this, response = move(response)] {
+        // If the server responded with "Connection: close", close the connection
+        // as the server may or may not want to close the socket.
+        if (auto result = response->headers().get("Connection"sv); result.has_value() && result.value().equals_ignoring_case("close"sv))
+            shutdown(ShutdownMode::CloseSocket);
         did_finish(response);
     });
 }

Userland/Libraries/LibHTTP/Job.h

@@ -22,7 +22,7 @@ public:
     virtual ~Job() override;
 
     virtual void start(NonnullRefPtr<Core::Socket>) override = 0;
-    virtual void shutdown() override = 0;
+    virtual void shutdown(ShutdownMode) override = 0;
 
     HttpResponse* response() { return static_cast<HttpResponse*>(Core::NetworkJob::response()); }
     const HttpResponse* response() const { return static_cast<const HttpResponse*>(Core::NetworkJob::response()); }