RequestServer+LibProtocol: Add an 'EnsureConnection' IPC endpoint

This will allow LibWeb (and other components) to request a connection to
be premade and cached, to make subsequent loads faster.

Userland/Libraries/LibProtocol/RequestClient.cpp

@@ -15,6 +15,11 @@ RequestClient::RequestClient()
 {
 }
 
+void RequestClient::ensure_connection(URL const& url, ::RequestServer::CacheLevel cache_level)
+{
+    async_ensure_connection(url, cache_level);
+}
+
 template<typename RequestHashMapTraits>
 RefPtr<Request> RequestClient::start_request(String const& method, URL const& url, HashMap<String, String, RequestHashMapTraits> const& request_headers, ReadonlyBytes request_body)
 {

Userland/Libraries/LibProtocol/RequestClient.h

@@ -24,6 +24,8 @@ public:
     template<typename RequestHashMapTraits = Traits<String>>
     RefPtr<Request> start_request(String const& method, URL const&, HashMap<String, String, RequestHashMapTraits> const& request_headers = {}, ReadonlyBytes request_body = {});
 
+    void ensure_connection(URL const&, ::RequestServer::CacheLevel);
+
     bool stop_request(Badge<Request>, Request&);
     bool set_certificate(Badge<Request>, Request&, String, String);
 

Userland/Services/RequestServer/ClientConnection.cpp

@@ -9,6 +9,7 @@
 #include <RequestServer/Protocol.h>
 #include <RequestServer/Request.h>
 #include <RequestServer/RequestClientEndpoint.h>
+#include <netdb.h>
 
 namespace RequestServer {
 
@@ -110,4 +111,37 @@ Messages::RequestServer::SetCertificateResponse ClientConnection::set_certificat
     return success;
 }
 
+void ClientConnection::ensure_connection(URL const& url, ::RequestServer::CacheLevel const& cache_level)
+{
+    if (!url.is_valid()) {
+        dbgln("EnsureConnection: Invalid URL requested: '{}'", url);
+        return;
+    }
+
+    if (cache_level == CacheLevel::ResolveOnly) {
+        return Core::deferred_invoke([host = url.host()] {
+            dbgln("EnsureConnection: DNS-preload for {}", host);
+            (void)gethostbyname(host.characters());
+        });
+    }
+
+    struct {
+        URL const& m_url;
+        void start(NonnullRefPtr<Core::Socket> socket) { socket->connect(m_url.host(), m_url.port_or_default()); }
+    } job { url };
+
+    dbgln("EnsureConnection: Pre-connect to {}", url);
+    auto do_preconnect = [&](auto& cache) {
+        auto& connection = ConnectionCache::get_or_create_connection(cache, url, job);
+        connection.removal_timer->start();
+    };
+
+    if (url.scheme() == "http"sv)
+        do_preconnect(ConnectionCache::g_tcp_connection_cache);
+    else if (url.scheme() == "https"sv)
+        do_preconnect(ConnectionCache::g_tls_connection_cache);
+    else
+        dbgln("EnsureConnection: Invalid URL scheme: '{}'", url.scheme());
+}
+
 }

Userland/Services/RequestServer/ClientConnection.h

@@ -34,6 +34,7 @@ private:
     virtual Messages::RequestServer::StartRequestResponse start_request(String const&, URL const&, IPC::Dictionary const&, ByteBuffer const&) override;
     virtual Messages::RequestServer::StopRequestResponse stop_request(i32) override;
     virtual Messages::RequestServer::SetCertificateResponse set_certificate(i32, String const&, String const&) override;
+    virtual void ensure_connection(URL const& url, ::RequestServer::CacheLevel const& cache_level) override;
 
     HashMap<i32, OwnPtr<Request>> m_requests;
 };

Userland/Services/RequestServer/ConnectionCache.h

@@ -13,6 +13,15 @@
 #include <LibCore/Timer.h>
 #include <LibTLS/TLSv12.h>
 
+namespace RequestServer {
+
+enum class CacheLevel {
+    ResolveOnly,
+    CreateConnection,
+};
+
+}
+
 namespace RequestServer::ConnectionCache {
 
 template<typename Socket>

Userland/Services/RequestServer/RequestServer.ipc

@@ -1,4 +1,5 @@
 #include <AK/URL.h>
+#include <RequestServer/ConnectionCache.h>
 
 endpoint RequestServer
 {
@@ -8,4 +9,6 @@ endpoint RequestServer
     start_request(String method, URL url, IPC::Dictionary request_headers, ByteBuffer request_body) => (i32 request_id, Optional<IPC::File> response_fd)
     stop_request(i32 request_id) => (bool success)
     set_certificate(i32 request_id, String certificate, String key) => (bool success)
+
+    ensure_connection(URL url, ::RequestServer::CacheLevel cache_level) =|
 }