Implement systemd-style readiness notification via NOTIFY_SOCKET

The service may specify this with ready-notification=socket:path.
This will result in dinit creating an abstract datagram socket
and perform reads on it. As soon as the READY=1 datagram arrives,
the readiness notification is signaled.

Author: q66

src/baseproc-service.cc

@@ -30,7 +30,8 @@ void base_process_service::do_smooth_recovery() noexcept
 
 bool base_process_service::bring_up() noexcept
 {
-    if (!open_socket()) {
+    if (!open_socket() || !open_ready_socket()) {
+        becoming_inactive();
         return false;
     }
 
@@ -152,7 +153,7 @@ bool base_process_service::start_ps_process(const std::vector<const char *> &cmd
 
         int control_socket[2] = {-1, -1};
         int notify_pipe[2] = {-1, -1};
-        bool have_notify = !notification_var.empty() || force_notification_fd != -1;
+        bool have_notify = !notification_var.empty() || ready_socket_fd >= 0 || force_notification_fd != -1;
         ready_notify_watcher * rwatcher = have_notify ? get_ready_watcher() : nullptr;
         bool ready_watcher_registered = false;
 
@@ -175,7 +176,7 @@ bool base_process_service::start_ps_process(const std::vector<const char *> &cmd
             }
         }
 
-        if (have_notify) {
+        if (have_notify && ready_socket_fd < 0) {
             // Create a notification pipe:
             if (bp_sys::pipe2(notify_pipe, 0) != 0) {
                 log(loglevel_t::ERROR, get_name(), ": can't create notification pipe: ", strerror(errno));
@@ -185,10 +186,14 @@ bool base_process_service::start_ps_process(const std::vector<const char *> &cmd
             // Set the read side as close-on-exec:
             int fdflags = bp_sys::fcntl(notify_pipe[0], F_GETFD);
             bp_sys::fcntl(notify_pipe[0], F_SETFD, fdflags | FD_CLOEXEC);
+        } else if (have_notify) {
+            notification_var = "NOTIFY_SOCKET=" + ready_socket_path;
+        }
 
+        if (have_notify) {
             // add, but don't yet enable, readiness watcher:
             try {
-                rwatcher->add_watch(event_loop, notify_pipe[0], dasynq::IN_EVENTS, false);
+                rwatcher->add_watch(event_loop, ready_socket_fd >= 0 ? ready_socket_fd : notify_pipe[0], dasynq::IN_EVENTS, false);
                 ready_watcher_registered = true;
             }
             catch (std::exception &exc) {
@@ -251,7 +256,7 @@ bool base_process_service::start_ps_process(const std::vector<const char *> &cmd
             run_params.unmask_sigint = onstart_flags.unmask_intr;
             run_params.csfd = control_socket[1];
             run_params.socket_fd = socket_fd;
-            run_params.notify_fd = notify_pipe[1];
+            run_params.notify_fd = ready_socket_fd >= 0 ? ready_socket_fd : notify_pipe[1];
             run_params.force_notify_fd = force_notification_fd;
             run_params.notify_var = notification_var.c_str();
             run_params.env_file = env_file.c_str();
@@ -469,86 +474,116 @@ void base_process_service::becoming_inactive() noexcept
         close(socket_fd);
         socket_fd = -1;
     }
-}
-
-bool base_process_service::open_socket() noexcept
-{
-    if (socket_path.empty() || socket_fd != -1) {
-        // No socket, or already open
-        return true;
+    if (ready_socket_fd != -1) {
+        close(ready_socket_fd);
+        ready_socket_fd = -1;
     }
+    free(ready_socket_name);
+    ready_socket_name = nullptr;
+}
 
-    const char * saddrname = socket_path.c_str();
-
+static int open_sock(const char *path, const std::string &svcname, int type,
+        uid_t uid, gid_t gid, int perms, struct sockaddr_un *&name) noexcept {
     // Check the specified socket path
     struct stat stat_buf;
-    if (stat(saddrname, &stat_buf) == 0) {
+    if (stat(path, &stat_buf) == 0) {
         if ((stat_buf.st_mode & S_IFSOCK) == 0) {
             // Not a socket
-            log(loglevel_t::ERROR, get_name(), ": activation socket file exists (and is not a socket)");
-            return false;
+            log(loglevel_t::ERROR, svcname, ": socket file exists (and is not a socket)");
+            return -1;
         }
     }
     else if (errno != ENOENT) {
         // Other error
-        log(loglevel_t::ERROR, get_name(), ": error checking activation socket: ", strerror(errno));
-        return false;
+        log(loglevel_t::ERROR, svcname, ": error checking socket: ", strerror(errno));
+        return -1;
     }
 
     // Remove stale socket file (if it exists).
     // We won't test the return from unlink - if it fails other than due to ENOENT, we should get an
     // error when we try to create the socket anyway.
-    unlink(saddrname);
+    unlink(path);
 
-    uint sockaddr_size = offsetof(struct sockaddr_un, sun_path) + socket_path.length() + 1;
-    struct sockaddr_un * name = static_cast<sockaddr_un *>(malloc(sockaddr_size));
+    uint sockaddr_size = offsetof(struct sockaddr_un, sun_path) + strlen(path) + 1;
+    name = static_cast<sockaddr_un *>(malloc(sockaddr_size));
     if (name == nullptr) {
-        log(loglevel_t::ERROR, get_name(), ": opening activation socket: out of memory");
-        return false;
+        log(loglevel_t::ERROR, svcname, ": opening socket: out of memory");
+        return -1;
     }
 
     name->sun_family = AF_UNIX;
-    strcpy(name->sun_path, saddrname);
+    strcpy(name->sun_path, path);
 
-    int sockfd = dinit_socket(AF_UNIX, SOCK_STREAM, 0, SOCK_NONBLOCK | SOCK_CLOEXEC);
+    int sockfd = dinit_socket(AF_UNIX, type, 0, SOCK_NONBLOCK | SOCK_CLOEXEC);
     if (sockfd == -1) {
-        log(loglevel_t::ERROR, get_name(), ": error creating activation socket: ", strerror(errno));
+        log(loglevel_t::ERROR, svcname, ": error creating socket: ", strerror(errno));
         free(name);
-        return false;
+        return -1;
     }
 
     if (bind(sockfd, (struct sockaddr *) name, sockaddr_size) == -1) {
-        log(loglevel_t::ERROR, get_name(), ": error binding activation socket: ", strerror(errno));
+        log(loglevel_t::ERROR, svcname, ": error binding socket: ", strerror(errno));
         close(sockfd);
         free(name);
-        return false;
+        return -1;
     }
 
-    free(name);
-
     // POSIX (1003.1, 2013) says that fchown and fchmod don't necessarily work on sockets. We have to
     // use chown and chmod instead.
-    if (chown(saddrname, socket_uid, socket_gid)) {
-        log(loglevel_t::ERROR, get_name(), ": error setting activation socket owner/group: ",
+    if (chown(path, uid, gid)) {
+        log(loglevel_t::ERROR, svcname, ": error setting socket owner/group: ",
                 strerror(errno));
         close(sockfd);
-        return false;
+        return -1;
     }
 
-    if (chmod(saddrname, socket_perms) == -1) {
-        log(loglevel_t::ERROR, get_name(), ": Error setting activation socket permissions: ",
+    if (chmod(path, perms) == -1) {
+        log(loglevel_t::ERROR, svcname, ": Error setting socket permissions: ",
                 strerror(errno));
         close(sockfd);
-        return false;
+        return -1;
     }
 
-    if (listen(sockfd, 128) == -1) { // 128 "seems reasonable".
-        log(loglevel_t::ERROR, ": error listening on activation socket: ", strerror(errno));
+    if (type != SOCK_DGRAM && listen(sockfd, 128) == -1) { // 128 "seems reasonable".
+        log(loglevel_t::ERROR, ": error listening on socket: ", strerror(errno));
         close(sockfd);
+        return -1;
+    }
+
+    return sockfd;
+}
+
+bool base_process_service::open_socket() noexcept
+{
+    if (socket_path.empty() || socket_fd != -1) {
+        // No socket, or already open
+        return true;
+    }
+
+    struct sockaddr_un *name = nullptr;
+    socket_fd = open_sock(socket_path.c_str(), get_name(), SOCK_STREAM, socket_uid,
+            socket_gid, socket_perms, name);
+    free(name);
+
+    return socket_fd >= 0;
+}
+
+bool base_process_service::open_ready_socket() noexcept
+{
+    if (ready_socket_path.empty() || ready_socket_fd != -1) {
+        // No socket, or already open
+        return true;
+    }
+
+    ready_socket_fd = open_sock(ready_socket_path.c_str(), get_name(), SOCK_DGRAM,
+            ready_socket_uid, ready_socket_gid, ready_socket_perms, ready_socket_name);
+
+    if (ready_socket_fd < 0) {
+        free(ready_socket_name);
+        ready_socket_name = nullptr;
         return false;
     }
 
-    socket_fd = sockfd;
     return true;
 }
 

src/includes/load-service.h

@@ -225,7 +225,7 @@ enum class setting_id_t {
     LOGFILE_GID, LOG_TYPE, LOG_BUFFER_SIZE, CONSUMER_OF, RESTART, SMOOTH_RECOVERY, OPTIONS,
     LOAD_OPTIONS, TERM_SIGNAL, TERMSIGNAL /* deprecated */, RESTART_LIMIT_INTERVAL, RESTART_DELAY,
     RESTART_LIMIT_COUNT, STOP_TIMEOUT, START_TIMEOUT, RUN_AS, CHAIN_TO, READY_NOTIFICATION,
-    INITTAB_ID, INITTAB_LINE,
+    READY_SOCKET_PERMISSIONS, READY_SOCKET_UID, READY_SOCKET_GID, INITTAB_ID, INITTAB_LINE,
     // Prefixed with SETTING_ to avoid name collision with system macros:
     SETTING_RLIMIT_NOFILE, SETTING_RLIMIT_CORE, SETTING_RLIMIT_DATA, SETTING_RLIMIT_ADDRSPACE,
     // Possibly unsupported depending on platform/build options:
@@ -1282,12 +1282,17 @@ class service_settings_wrapper
     auto_restart_mode auto_restart = auto_restart_mode::DEFAULT_AUTO_RESTART;
     bool smooth_recovery = false;
     string socket_path;
+    string ready_socket_path;
     int socket_perms = 0666;
     // Note: Posix allows that uid_t and gid_t may be unsigned types, but eg chown uses -1 as an
     // invalid value, so it's safe to assume that we can do the same:
     uid_t socket_uid = -1;
     gid_t socket_uid_gid = -1;  // primary group of socket user if known
     gid_t socket_gid = -1;
+    int ready_socket_perms = 0600;
+    uid_t ready_socket_uid = -1;
+    gid_t ready_socket_uid_gid = -1;
+    gid_t ready_socket_gid = -1;
     // Restart limit interval / count; default is 10 seconds, 3 restarts:
     timespec restart_interval = { .tv_sec = 10, .tv_nsec = 0 };
     int max_restarts = 3;
@@ -1362,6 +1367,9 @@ class service_settings_wrapper
             if (!socket_path.empty()) {
                 report_lint("'socket-listen' specified, but ignored for the specified (or default) service type'.");
             }
+            if (!ready_socket_path.empty()) {
+                report_lint("'ready-notification' specified, but ignored for the specified (or default) service type'.");
+            }
             #if USE_UTMPX
             if (inittab_id[0] != 0 || inittab_line[0] != 0) {
                 report_lint("'inittab_line' or 'inittab_id' specified, but ignored for the specified (or default) service type.");
@@ -1395,7 +1403,7 @@ class service_settings_wrapper
                 report_error("process ID file ('pid-file') not specified for bgprocess service.");
             }
 
-            if (readiness_fd != -1 || !readiness_var.empty()) {
+            if (readiness_fd != -1 || !ready_socket_path.empty() || !readiness_var.empty()) {
                 report_error("readiness notification ('ready-notification') is not supported "
                         "for bgprocess services.");
             }
@@ -1421,6 +1429,7 @@ class service_settings_wrapper
             };
 
             do_resolve("socket-listen", socket_path);
+            do_resolve("ready-notification", ready_socket_path);
             do_resolve("logfile", logfile);
             do_resolve("working-dir", working_dir);
             do_resolve("pid-file", pid_file);
@@ -1429,6 +1438,7 @@ class service_settings_wrapper
         // If socket_gid hasn't been explicitly set, but the socket_uid was specified as a name (and
         // we therefore recovered the primary group), use the primary group of the specified user.
         if (socket_gid == (gid_t)-1) socket_gid = socket_uid_gid;
+        if (ready_socket_gid == (gid_t)-1) ready_socket_gid = ready_socket_uid_gid;
         // Also for logfile_uid/gid, we reset logfile ownership to dinit process uid/gid if uid/gid
         // wasn't specified by service
         if (logfile_uid == (uid_t) -1) logfile_uid = getuid();
@@ -1872,12 +1882,38 @@ void process_service_line(settings_wrapper &settings, const char *name, const ch
                             "ready-notification", input_pos);
                 }
             }
+            else if (starts_with(notify_setting, "socket:")) {
+                settings.ready_socket_path = notify_setting.substr(7 /* len 'socket:' */);
+                if (settings.ready_socket_path.empty()) {
+                    throw service_description_exc(name, "invalid readiness socket path",
+                            "ready-notification", input_pos);
+                }
+            }
             else {
                 throw service_description_exc(name, "unrecognised setting: " + notify_setting,
                         "ready-notification", input_pos);
             }
             break;
         }
+        case setting_id_t::READY_SOCKET_PERMISSIONS:
+        {
+            string sock_perm_str = read_setting_value(input_pos, i, end, nullptr);
+            settings.ready_socket_perms = parse_perms(input_pos, sock_perm_str, name, "ready-socket-permissions");
+            break;
+        }
+        case setting_id_t::READY_SOCKET_UID:
+        {
+            string sock_uid_s = read_setting_value(input_pos, i, end, nullptr);
+            settings.ready_socket_uid = parse_uid_param(input_pos, sock_uid_s, name, "ready-socket-uid",
+                    &settings.ready_socket_uid_gid);
+            break;
+        }
+        case setting_id_t::READY_SOCKET_GID:
+        {
+            string sock_gid_s = read_setting_value(input_pos, i, end, nullptr);
+            settings.ready_socket_gid = parse_gid_param(input_pos, sock_gid_s, "ready-socket-gid", name);
+            break;
+        }
         case setting_id_t::INITTAB_ID:
         {
             string inittab_setting = read_setting_value(input_pos, i, end, nullptr);

src/includes/proc-service.h

@@ -227,6 +227,8 @@ class base_process_service : public service_record
     int notification_fd = -1;  // If readiness notification is via fd
     int log_output_fd = -1; // If logging via buffer/pipe, write end of the pipe
     int log_input_fd = -1; // If logging via buffer/pipe, read end of the pipe
+    int ready_socket_fd = -1; // For socket ready notification, this is the file descriptor for the socket.
+    struct sockaddr_un *ready_socket_name = nullptr; // Since ready socket is UDP, we need this for recvfrom().
 
     // Only one of waiting_restart_timer and waiting_stopstart_timer should be set at any time.
     // They indicate that the process timer is armed (and why).
@@ -298,6 +300,9 @@ class base_process_service : public service_record
     // Open the activation socket, return false on failure
     bool open_socket() noexcept;
 
+    // Open the readiness socket, return false on failure
+    bool open_ready_socket() noexcept;
+
     // Get the readiness notification watcher for this service, if it has one; may return nullptr.
     virtual ready_notify_watcher *get_ready_watcher() noexcept
     {

src/includes/service.h

@@ -327,6 +327,11 @@ class service_record
     uid_t socket_uid = -1;  // socket user id or -1
     gid_t socket_gid = -1;  // socket group id or -1
 
+    string ready_socket_path; // path to the socket for ready-notification
+    int ready_socket_perms = 0;
+    uid_t ready_socket_uid = -1;
+    gid_t ready_socket_gid = -1;
+
     stopped_reason_t stop_reason = stopped_reason_t::NORMAL;  // reason why stopped
 
     string start_on_completion;  // service to start when this one completes
@@ -601,6 +606,15 @@ class service_record
         this->socket_gid = socket_gid;
     }
 
+    void set_ready_socket_details(string &&socket_path, int socket_perms, uid_t socket_uid, uid_t socket_gid)
+            noexcept
+    {
+        this->ready_socket_path = std::move(socket_path);
+        this->ready_socket_perms = socket_perms;
+        this->ready_socket_uid = socket_uid;
+        this->ready_socket_gid = socket_gid;
+    }
+
     // Set the service that this one "chains" to. When this service completes, the named service is started.
     void set_chain_to(string &&chain_to) noexcept
     {

src/load-service.cc

@@ -851,6 +851,8 @@ service_record * dirload_service_set::load_reload_service(const char *fullname,
         rval->set_flags(settings.onstart_flags);
         rval->set_socket_details(std::move(settings.socket_path), settings.socket_perms,
                 settings.socket_uid, settings.socket_gid);
+        rval->set_ready_socket_details(std::move(settings.ready_socket_path),
+                settings.ready_socket_perms, settings.ready_socket_uid, settings.ready_socket_gid);
         rval->set_chain_to(std::move(settings.chain_to_name));
         rval->set_environment(std::move(srv_env));