SystemServer+LibCore: Allow service to request multiple sockets

SystemServer only allowed a single socket to be created for a service
before this.  Now, SystemServer will allow any amount of sockets.  The
sockets can be defined like so:

[SomeService]
Socket=/tmp/portal/socket1,/tmp/portal/socket2,/tmp/portal/socket3
SocketPermissions=660,600

The last item in SocketPermissions is applied to the remainder of the
sockets in the Socket= line, so multiple sockets can have the same
permissions without having to repeat them.

Defining multiple sockets is not allowed for socket-activated services
at the moment, and wouldn't make much sense anyway.

This patch also makes socket takeovers more robust by removing the
assumption that the socket will always be passed in fd 3.  Now, the
SOCKET_TAKEOVER environment variable carries information about which
endpoint corresponds to which socket, like so:

SOCKET_TAKEOVER=/tmp/portal/socket1:3 /tmp/portal/socket2:4

and LocalServer/LocalService will parse this automatically and select
the correct one.  The old behavior of getting the default socket is
preserved so long as the service only requests a single socket in
SystemServer.ini.

Userland/Libraries/LibCore/LocalServer.cpp

@@ -50,28 +50,39 @@ LocalServer::~LocalServer()
         ::close(m_fd);
 }
 
-bool LocalServer::take_over_from_system_server()
+bool LocalServer::take_over_from_system_server(String const& socket_path)
 {
     if (m_listening)
         return false;
 
-    constexpr auto socket_takeover = "SOCKET_TAKEOVER";
+    if (!LocalSocket::s_overtaken_sockets_parsed)
+        LocalSocket::parse_sockets_from_system_server();
 
-    if (getenv(socket_takeover)) {
+    int fd = -1;
+    if (socket_path.is_null()) {
+        // We want the first (and only) socket.
+        if (LocalSocket::s_overtaken_sockets.size() == 1) {
+            fd = LocalSocket::s_overtaken_sockets.begin()->value;
+        }
+    } else {
+        auto it = LocalSocket::s_overtaken_sockets.find(socket_path);
+        if (it != LocalSocket::s_overtaken_sockets.end()) {
+            fd = it->value;
+        }
+    }
+
+    if (fd >= 0) {
         // Sanity check: it has to be a socket.
         struct stat stat;
-        int rc = fstat(3, &stat);
+        int rc = fstat(fd, &stat);
         if (rc == 0 && S_ISSOCK(stat.st_mode)) {
-            // The SystemServer has passed us the socket as fd 3,
-            // so use that instead of creating our own.
-            m_fd = 3;
+            // The SystemServer has passed us the socket, so use that instead of
+            // creating our own.
+            m_fd = fd;
             // It had to be !CLOEXEC for obvious reasons, but we
             // don't need it to be !CLOEXEC anymore, so set the
             // CLOEXEC flag now.
             fcntl(m_fd, F_SETFD, FD_CLOEXEC);
-            // We wouldn't want our children to think we're passing
-            // them a socket either, so unset the env variable.
-            unsetenv(socket_takeover);
 
             m_listening = true;
             setup_notifier();

Userland/Libraries/LibCore/LocalServer.h

@@ -36,7 +36,7 @@ class LocalServer : public Object {
 public:
     virtual ~LocalServer() override;
 
-    bool take_over_from_system_server();
+    bool take_over_from_system_server(String const& path = String());
     bool is_listening() const { return m_listening; }
     bool listen(const String& address);
 

Userland/Libraries/LibCore/LocalSocket.cpp

@@ -28,6 +28,7 @@
 #include <errno.h>
 #include <fcntl.h>
 #include <stdio.h>
+#include <stdlib.h>
 #include <sys/socket.h>
 #include <sys/stat.h>
 
@@ -73,15 +74,49 @@ LocalSocket::~LocalSocket()
 {
 }
 
-RefPtr<LocalSocket> LocalSocket::take_over_accepted_socket_from_system_server()
-{
-    constexpr auto socket_takeover = "SOCKET_TAKEOVER";
-    if (!getenv(socket_takeover))
-        return nullptr;
+HashMap<String, int> LocalSocket::s_overtaken_sockets {};
+bool LocalSocket::s_overtaken_sockets_parsed { false };
 
-    // The SystemServer has passed us the socket as fd 3,
-    // so use that instead of creating our own.
-    constexpr int fd = 3;
+void LocalSocket::parse_sockets_from_system_server()
+{
+    VERIFY(!s_overtaken_sockets_parsed);
+
+    constexpr auto socket_takeover = "SOCKET_TAKEOVER";
+    const char* sockets = getenv(socket_takeover);
+    if (!sockets) {
+        s_overtaken_sockets_parsed = true;
+        return;
+    }
+
+    for (auto& socket : StringView(sockets).split_view(' ')) {
+        auto params = socket.split_view(':');
+        s_overtaken_sockets.set(params[0].to_string(), strtol(params[1].to_string().characters(), nullptr, 10));
+    }
+
+    s_overtaken_sockets_parsed = true;
+    // We wouldn't want our children to think we're passing
+    // them a socket either, so unset the env variable.
+    unsetenv(socket_takeover);
+}
+
+RefPtr<LocalSocket> LocalSocket::take_over_accepted_socket_from_system_server(String const& socket_path)
+{
+    if (!s_overtaken_sockets_parsed)
+        parse_sockets_from_system_server();
+
+    int fd;
+    if (socket_path.is_null()) {
+        // We want the first (and only) socket.
+        VERIFY(s_overtaken_sockets.size() == 1);
+        fd = s_overtaken_sockets.begin()->value;
+    } else {
+        auto it = s_overtaken_sockets.find(socket_path);
+        if (it == s_overtaken_sockets.end()) {
+            dbgln("Non-existent socket requested");
+            return nullptr;
+        }
+        fd = it->value;
+    }
 
     // Sanity check: it has to be a socket.
     struct stat stat;
@@ -99,9 +134,6 @@ RefPtr<LocalSocket> LocalSocket::take_over_accepted_socket_from_system_server()
     // don't need it to be !CLOEXEC anymore, so set the
     // CLOEXEC flag now.
     fcntl(fd, F_SETFD, FD_CLOEXEC);
-    // We wouldn't want our children to think we're passing
-    // them a socket either, so unset the env variable.
-    unsetenv(socket_takeover);
     return socket;
 }
 

Userland/Libraries/LibCore/LocalSocket.h

@@ -35,11 +35,20 @@ class LocalSocket final : public Socket {
 public:
     virtual ~LocalSocket() override;
 
-    static RefPtr<LocalSocket> take_over_accepted_socket_from_system_server();
+    static RefPtr<LocalSocket> take_over_accepted_socket_from_system_server(String const& socket_path = String());
 
 private:
     explicit LocalSocket(Object* parent = nullptr);
     LocalSocket(int fd, Object* parent = nullptr);
+
+    // FIXME: better place to put this so both LocalSocket and LocalServer can
+    // enjoy it?
+    friend class LocalServer;
+
+    static void parse_sockets_from_system_server();
+
+    static HashMap<String, int> s_overtaken_sockets;
+    static bool s_overtaken_sockets_parsed;
 };
 
 }