LibIPC: Add IPC::MultiServer convenience class

This encapsulates what our multi-client IPC servers typically do on
startup:

    1. Create a Core::LocalServer
    2. Take over a listening socket file descriptor from SystemServer
    3. Set up an accept handler for incoming connections

IPC::MultiServer does all this for you! All you have to do is provide
the relevant client connection type as a template argument.

11 files changed, 62 insertions, 81 deletions

diff --git a/Userland/Libraries/LibIPC/MultiServer.h b/Userland/Libraries/LibIPC/MultiServer.h
new file mode 100644
index 0000000000..3a3794fb28
--- /dev/null
+++ b/Userland/Libraries/LibIPC/MultiServer.h
@@ -0,0 +1,39 @@
+/*
+ * Copyright (c) 2021, Andreas Kling <kling@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/Error.h>
+#include <LibCore/LocalServer.h>
+#include <LibIPC/ClientConnection.h>
+
+namespace IPC {
+
+template<typename ClientConnectionType>
+class MultiServer {
+public:
+    static ErrorOr<NonnullOwnPtr<MultiServer>> try_create(Optional<String> socket_path = {})
+    {
+        auto server = TRY(Core::LocalServer::try_create());
+        TRY(server->take_over_from_system_server(socket_path.value_or({})));
+        return adopt_nonnull_own_or_enomem(new (nothrow) MultiServer(move(server)));
+    }
+
+private:
+    explicit MultiServer(NonnullRefPtr<Core::LocalServer> server)
+        : m_server(move(server))
+    {
+        m_server->on_accept = [&](auto client_socket) {
+            auto client_id = ++m_next_client_id;
+            (void)IPC::new_client_connection<ClientConnectionType>(move(client_socket), client_id);
+        };
+    }
+
+    int m_next_client_id { 0 };
+    RefPtr<Core::LocalServer> m_server;
+};
+
+}
diff --git a/Userland/Services/Clipboard/main.cpp b/Userland/Services/Clipboard/main.cpp
index ea4ddc4855..3e087fcfd7 100644
--- a/Userland/Services/Clipboard/main.cpp
+++ b/Userland/Services/Clipboard/main.cpp
@@ -7,9 +7,8 @@
 #include <Clipboard/ClientConnection.h>
 #include <Clipboard/Storage.h>
 #include <LibCore/EventLoop.h>
-#include <LibCore/LocalServer.h>
 #include <LibCore/System.h>
-#include <LibIPC/ClientConnection.h>
+#include <LibIPC/MultiServer.h>
 #include <LibMain/Main.h>
 
 ErrorOr<int> serenity_main(Main::Arguments)
@@ -18,14 +17,7 @@ ErrorOr<int> serenity_main(Main::Arguments)
     Core::EventLoop event_loop;
     TRY(Core::System::unveil(nullptr, nullptr));
 
-    auto server = TRY(Core::LocalServer::try_create());
-    TRY(server->take_over_from_system_server());
-
-    server->on_accept = [&](auto client_socket) {
-        static int s_next_client_id = 0;
-        int client_id = ++s_next_client_id;
-        (void)IPC::new_client_connection<Clipboard::ClientConnection>(move(client_socket), client_id);
-    };
+    auto server = TRY(IPC::MultiServer<Clipboard::ClientConnection>::try_create());
 
     Clipboard::Storage::the().on_content_change = [&] {
         Clipboard::ClientConnection::for_each_client([&](auto& client) {
diff --git a/Userland/Services/ConfigServer/main.cpp b/Userland/Services/ConfigServer/main.cpp
index cde261b8a7..344e940a94 100644
--- a/Userland/Services/ConfigServer/main.cpp
+++ b/Userland/Services/ConfigServer/main.cpp
@@ -5,9 +5,9 @@
  */
 
 #include "ClientConnection.h"
-#include <LibCore/LocalServer.h>
 #include <LibCore/StandardPaths.h>
 #include <LibCore/System.h>
+#include <LibIPC/MultiServer.h>
 #include <LibMain/Main.h>
 
 ErrorOr<int> serenity_main(Main::Arguments)
@@ -18,13 +18,6 @@ ErrorOr<int> serenity_main(Main::Arguments)
 
     Core::EventLoop event_loop;
 
-    auto server = TRY(Core::LocalServer::try_create());
-    TRY(server->take_over_from_system_server());
-    server->on_accept = [&](auto client_socket) {
-        static int s_next_client_id = 0;
-        int client_id = ++s_next_client_id;
-        (void)IPC::new_client_connection<ConfigServer::ClientConnection>(move(client_socket), client_id);
-    };
-
+    auto server = TRY(IPC::MultiServer<ConfigServer::ClientConnection>::try_create());
     return event_loop.exec();
 }
diff --git a/Userland/Services/InspectorServer/main.cpp b/Userland/Services/InspectorServer/main.cpp
index 5029ffdc90..d9770f32fa 100644
--- a/Userland/Services/InspectorServer/main.cpp
+++ b/Userland/Services/InspectorServer/main.cpp
@@ -10,21 +10,16 @@
 #include <LibCore/LocalServer.h>
 #include <LibCore/System.h>
 #include <LibIPC/ClientConnection.h>
+#include <LibIPC/MultiServer.h>
 #include <LibMain/Main.h>
 
 ErrorOr<int> serenity_main(Main::Arguments)
 {
     Core::EventLoop event_loop;
-    auto server = TRY(Core::LocalServer::try_create());
 
     TRY(Core::System::pledge("stdio unix accept"));
 
-    TRY(server->take_over_from_system_server("/tmp/portal/inspector"));
-    server->on_accept = [&](auto client_socket) {
-        static int s_next_client_id = 0;
-        int client_id = ++s_next_client_id;
-        (void)IPC::new_client_connection<InspectorServer::ClientConnection>(move(client_socket), client_id);
-    };
+    auto server = TRY(IPC::MultiServer<InspectorServer::ClientConnection>::try_create("/tmp/portal/inspector"));
 
     auto inspectables_server = TRY(Core::LocalServer::try_create());
     TRY(inspectables_server->take_over_from_system_server("/tmp/portal/inspectables"));
diff --git a/Userland/Services/LaunchServer/main.cpp b/Userland/Services/LaunchServer/main.cpp
index 00d6137fb2..befe4af84b 100644
--- a/Userland/Services/LaunchServer/main.cpp
+++ b/Userland/Services/LaunchServer/main.cpp
@@ -8,14 +8,14 @@
 #include "Launcher.h"
 #include <LibCore/ConfigFile.h>
 #include <LibCore/EventLoop.h>
-#include <LibCore/LocalServer.h>
 #include <LibCore/System.h>
+#include <LibIPC/MultiServer.h>
 #include <LibMain/Main.h>
 
 ErrorOr<int> serenity_main(Main::Arguments)
 {
     Core::EventLoop event_loop;
-    auto server = TRY(Core::LocalServer::try_create());
+    auto server = TRY(IPC::MultiServer<LaunchServer::ClientConnection>::try_create());
 
     auto launcher = LaunchServer::Launcher();
     launcher.load_handlers();
@@ -23,12 +23,5 @@ ErrorOr<int> serenity_main(Main::Arguments)
 
     TRY(Core::System::pledge("stdio accept rpath proc exec"));
 
-    TRY(server->take_over_from_system_server());
-    server->on_accept = [&](auto client_socket) {
-        static int s_next_client_id = 0;
-        int client_id = ++s_next_client_id;
-        (void)IPC::new_client_connection<LaunchServer::ClientConnection>(move(client_socket), client_id);
-    };
-
     return event_loop.exec();
 }
diff --git a/Userland/Services/LookupServer/LookupServer.cpp b/Userland/Services/LookupServer/LookupServer.cpp
index 9cc5115117..2018901088 100644
--- a/Userland/Services/LookupServer/LookupServer.cpp
+++ b/Userland/Services/LookupServer/LookupServer.cpp
@@ -72,13 +72,7 @@ LookupServer::LookupServer()
     }
     m_mdns = MulticastDNS::construct(this);
 
-    m_local_server = Core::LocalServer::construct(this);
-    m_local_server->on_accept = [](auto client_socket) {
-        static int s_next_client_id = 0;
-        int client_id = ++s_next_client_id;
-        (void)IPC::new_client_connection<ClientConnection>(move(client_socket), client_id);
-    };
-    MUST(m_local_server->take_over_from_system_server());
+    m_server = MUST(IPC::MultiServer<ClientConnection>::try_create());
 }
 
 void LookupServer::load_etc_hosts()
diff --git a/Userland/Services/LookupServer/LookupServer.h b/Userland/Services/LookupServer/LookupServer.h
index 2e42d5e290..f94b3ad10c 100644
--- a/Userland/Services/LookupServer/LookupServer.h
+++ b/Userland/Services/LookupServer/LookupServer.h
@@ -6,12 +6,14 @@
 
 #pragma once
 
+#include "ClientConnection.h"
 #include "DNSName.h"
 #include "DNSPacket.h"
 #include "DNSServer.h"
 #include "MulticastDNS.h"
 #include <LibCore/FileWatcher.h>
 #include <LibCore/Object.h>
+#include <LibIPC/MultiServer.h>
 
 namespace LookupServer {
 
@@ -32,7 +34,7 @@ private:
 
     Vector<DNSAnswer> lookup(const DNSName& hostname, const String& nameserver, bool& did_get_response, DNSRecordType record_type, ShouldRandomizeCase = ShouldRandomizeCase::Yes);
 
-    RefPtr<Core::LocalServer> m_local_server;
+    OwnPtr<IPC::MultiServer<ClientConnection>> m_server;
     RefPtr<DNSServer> m_dns_server;
     RefPtr<MulticastDNS> m_mdns;
     Vector<String> m_nameservers;
diff --git a/Userland/Services/NotificationServer/main.cpp b/Userland/Services/NotificationServer/main.cpp
index ef74de1a2e..d7e69122f5 100644
--- a/Userland/Services/NotificationServer/main.cpp
+++ b/Userland/Services/NotificationServer/main.cpp
@@ -5,10 +5,9 @@
  */
 
 #include "ClientConnection.h"
-#include <LibCore/LocalServer.h>
 #include <LibCore/System.h>
 #include <LibGUI/Application.h>
-#include <LibGUI/WindowServerConnection.h>
+#include <LibIPC/MultiServer.h>
 #include <LibMain/Main.h>
 
 ErrorOr<int> serenity_main(Main::Arguments arguments)
@@ -16,14 +15,7 @@ ErrorOr<int> serenity_main(Main::Arguments arguments)
     TRY(Core::System::pledge("stdio recvfd sendfd accept rpath unix"));
 
     auto app = TRY(GUI::Application::try_create(arguments));
-    auto server = TRY(Core::LocalServer::try_create());
-
-    TRY(server->take_over_from_system_server());
-    server->on_accept = [&](auto client_socket) {
-        static int s_next_client_id = 0;
-        int client_id = ++s_next_client_id;
-        (void)IPC::new_client_connection<NotificationServer::ClientConnection>(move(client_socket), client_id);
-    };
+    auto server = TRY(IPC::MultiServer<NotificationServer::ClientConnection>::try_create());
 
     TRY(Core::System::unveil("/res", "r"));
     TRY(Core::System::unveil(nullptr, nullptr));
diff --git a/Userland/Services/SQLServer/main.cpp b/Userland/Services/SQLServer/main.cpp
index 814d3e342c..98ccc1099b 100644
--- a/Userland/Services/SQLServer/main.cpp
+++ b/Userland/Services/SQLServer/main.cpp
@@ -5,8 +5,8 @@
  */
 
 #include <LibCore/EventLoop.h>
-#include <LibCore/LocalServer.h>
 #include <LibCore/System.h>
+#include <LibIPC/MultiServer.h>
 #include <LibMain/Main.h>
 #include <SQLServer/ClientConnection.h>
 #include <stdio.h>
@@ -26,13 +26,6 @@ ErrorOr<int> serenity_main(Main::Arguments)
 
     Core::EventLoop event_loop;
 
-    auto server = TRY(Core::LocalServer::try_create());
-    TRY(server->take_over_from_system_server());
-    server->on_accept = [&](auto client_socket) {
-        static int s_next_client_id = 0;
-        int client_id = ++s_next_client_id;
-        (void)IPC::new_client_connection<SQLServer::ClientConnection>(client_socket, client_id);
-    };
-
+    auto server = TRY(IPC::MultiServer<SQLServer::ClientConnection>::try_create());
     return event_loop.exec();
 }
diff --git a/Userland/Services/WindowServer/EventLoop.cpp b/Userland/Services/WindowServer/EventLoop.cpp
index 15a4f3d701..101740f550 100644
--- a/Userland/Services/WindowServer/EventLoop.cpp
+++ b/Userland/Services/WindowServer/EventLoop.cpp
@@ -19,26 +19,12 @@
 namespace WindowServer {
 
 EventLoop::EventLoop()
-    : m_window_server(Core::LocalServer::construct())
-    , m_wm_server(Core::LocalServer::construct())
 {
     m_keyboard_fd = open("/dev/keyboard0", O_RDONLY | O_NONBLOCK | O_CLOEXEC);
     m_mouse_fd = open("/dev/mouse0", O_RDONLY | O_NONBLOCK | O_CLOEXEC);
 
-    MUST(m_window_server->take_over_from_system_server("/tmp/portal/window"));
-    MUST(m_wm_server->take_over_from_system_server("/tmp/portal/wm"));
-
-    m_window_server->on_accept = [&](auto client_socket) {
-        static int s_next_client_id = 0;
-        int client_id = ++s_next_client_id;
-        (void)IPC::new_client_connection<ClientConnection>(move(client_socket), client_id);
-    };
-
-    m_wm_server->on_accept = [&](auto client_socket) {
-        static int s_next_wm_id = 0;
-        int wm_id = ++s_next_wm_id;
-        (void)IPC::new_client_connection<WMClientConnection>(move(client_socket), wm_id);
-    };
+    m_window_server = MUST(IPC::MultiServer<ClientConnection>::try_create("/tmp/portal/window"));
+    m_wm_server = MUST(IPC::MultiServer<WMClientConnection>::try_create("/tmp/portal/wm"));
 
     if (m_keyboard_fd >= 0) {
         m_keyboard_notifier = Core::Notifier::construct(m_keyboard_fd, Core::Notifier::Read);
diff --git a/Userland/Services/WindowServer/EventLoop.h b/Userland/Services/WindowServer/EventLoop.h
index 2964de8408..dfad84b887 100644
--- a/Userland/Services/WindowServer/EventLoop.h
+++ b/Userland/Services/WindowServer/EventLoop.h
@@ -6,10 +6,12 @@
 
 #pragma once
 
+#include "ClientConnection.h"
+#include "WMClientConnection.h"
 #include <AK/ByteBuffer.h>
 #include <LibCore/EventLoop.h>
-#include <LibCore/LocalServer.h>
 #include <LibCore/Notifier.h>
+#include <LibIPC/MultiServer.h>
 
 namespace WindowServer {
 
@@ -31,8 +33,8 @@ private:
     RefPtr<Core::Notifier> m_keyboard_notifier;
     int m_mouse_fd { -1 };
     RefPtr<Core::Notifier> m_mouse_notifier;
-    RefPtr<Core::LocalServer> m_window_server;
-    RefPtr<Core::LocalServer> m_wm_server;
+    OwnPtr<IPC::MultiServer<ClientConnection>> m_window_server;
+    OwnPtr<IPC::MultiServer<WMClientConnection>> m_wm_server;
 };
 
 }