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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-25 02:54:53 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-25 02:54:53 +0000
commit527e791c5346846e2bc7d32f7597d70f9a274499 (patch)
treed2bd96487387b049f0a99182d4cfd066adddd039 /man/notify-selfcontained-example.c
parentAdding debian version 255.4-1. (diff)
downloadsystemd-527e791c5346846e2bc7d32f7597d70f9a274499.tar.xz
systemd-527e791c5346846e2bc7d32f7597d70f9a274499.zip
Merging upstream version 255.5.
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to '')
-rw-r--r--man/notify-selfcontained-example.c173
1 files changed, 173 insertions, 0 deletions
diff --git a/man/notify-selfcontained-example.c b/man/notify-selfcontained-example.c
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+++ b/man/notify-selfcontained-example.c
@@ -0,0 +1,173 @@
+/* SPDX-License-Identifier: MIT-0 */
+
+/* Implement the systemd notify protocol without external dependencies.
+ * Supports both readiness notification on startup and on reloading,
+ * according to the protocol defined at:
+ * https://www.freedesktop.org/software/systemd/man/latest/sd_notify.html
+ * This protocol is guaranteed to be stable as per:
+ * https://systemd.io/PORTABILITY_AND_STABILITY/ */
+
+#include <errno.h>
+#include <inttypes.h>
+#include <signal.h>
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <sys/socket.h>
+#include <sys/un.h>
+#include <time.h>
+#include <unistd.h>
+
+#define _cleanup_(f) __attribute__((cleanup(f)))
+
+static void closep(int *fd) {
+ if (!fd || *fd < 0)
+ return;
+
+ close(*fd);
+ *fd = -1;
+}
+
+static int notify(const char *message) {
+ union sockaddr_union {
+ struct sockaddr sa;
+ struct sockaddr_un sun;
+ } socket_addr = {
+ .sun.sun_family = AF_UNIX,
+ };
+ size_t path_length, message_length;
+ _cleanup_(closep) int fd = -1;
+ const char *socket_path;
+
+ socket_path = getenv("NOTIFY_SOCKET");
+ if (!socket_path)
+ return 0; /* Not running under systemd? Nothing to do */
+
+ if (!message)
+ return -EINVAL;
+
+ message_length = strlen(message);
+ if (message_length == 0)
+ return -EINVAL;
+
+ /* Only AF_UNIX is supported, with path or abstract sockets */
+ if (socket_path[0] != '/' && socket_path[0] != '@')
+ return -EAFNOSUPPORT;
+
+ path_length = strlen(socket_path);
+ /* Ensure there is room for NUL byte */
+ if (path_length >= sizeof(socket_addr.sun.sun_path))
+ return -E2BIG;
+
+ memcpy(socket_addr.sun.sun_path, socket_path, path_length);
+
+ /* Support for abstract socket */
+ if (socket_addr.sun.sun_path[0] == '@')
+ socket_addr.sun.sun_path[0] = 0;
+
+ fd = socket(AF_UNIX, SOCK_DGRAM|SOCK_CLOEXEC, 0);
+ if (fd < 0)
+ return -errno;
+
+ if (connect(fd, &socket_addr.sa, offsetof(struct sockaddr_un, sun_path) + path_length) != 0)
+ return -errno;
+
+ ssize_t written = write(fd, message, message_length);
+ if (written != (ssize_t) message_length)
+ return written < 0 ? -errno : -EPROTO;
+
+ return 1; /* Notified! */
+}
+
+static int notify_ready(void) {
+ return notify("READY=1");
+}
+
+static int notify_reloading(void) {
+ /* A buffer with length sufficient to format the maximum UINT64 value. */
+ char reload_message[sizeof("RELOADING=1\nMONOTONIC_USEC=18446744073709551615")];
+ struct timespec ts;
+ uint64_t now;
+
+ /* Notify systemd that we are reloading, including a CLOCK_MONOTONIC timestamp in usec
+ * so that the program is compatible with a Type=notify-reload service. */
+
+ if (clock_gettime(CLOCK_MONOTONIC, &ts) < 0)
+ return -errno;
+
+ if (ts.tv_sec < 0 || ts.tv_nsec < 0 ||
+ (uint64_t) ts.tv_sec > (UINT64_MAX - (ts.tv_nsec / 1000ULL)) / 1000000ULL)
+ return -EINVAL;
+
+ now = (uint64_t) ts.tv_sec * 1000000ULL + (uint64_t) ts.tv_nsec / 1000ULL;
+
+ if (snprintf(reload_message, sizeof(reload_message), "RELOADING=1\nMONOTONIC_USEC=%" PRIu64, now) < 0)
+ return -EINVAL;
+
+ return notify(reload_message);
+}
+
+static volatile sig_atomic_t reloading = 0;
+static volatile sig_atomic_t terminating = 0;
+
+static void signal_handler(int sig) {
+ if (sig == SIGHUP)
+ reloading = 1;
+ else if (sig == SIGINT || sig == SIGTERM)
+ terminating = 1;
+}
+
+int main(int argc, char **argv) {
+ struct sigaction sa = {
+ .sa_handler = signal_handler,
+ .sa_flags = SA_RESTART,
+ };
+ int r;
+
+ /* Setup signal handlers */
+ sigemptyset(&sa.sa_mask);
+ sigaction(SIGHUP, &sa, NULL);
+ sigaction(SIGINT, &sa, NULL);
+ sigaction(SIGTERM, &sa, NULL);
+
+ /* Do more service initialization work here … */
+
+ /* Now that all the preparations steps are done, signal readiness */
+
+ r = notify_ready();
+ if (r < 0) {
+ fprintf(stderr, "Failed to notify readiness to $NOTIFY_SOCKET: %s\n", strerror(-r));
+ return EXIT_FAILURE;
+ }
+
+ while (!terminating) {
+ if (reloading) {
+ reloading = false;
+
+ /* As a separate but related feature, we can also notify the manager
+ * when reloading configuration. This allows accurate state-tracking,
+ * and also automated hook-in of 'systemctl reload' without having to
+ * specify manually an ExecReload= line in the unit file. */
+
+ r = notify_reloading();
+ if (r < 0) {
+ fprintf(stderr, "Failed to notify reloading to $NOTIFY_SOCKET: %s\n", strerror(-r));
+ return EXIT_FAILURE;
+ }
+
+ /* Do some reconfiguration work here … */
+
+ r = notify_ready();
+ if (r < 0) {
+ fprintf(stderr, "Failed to notify readiness to $NOTIFY_SOCKET: %s\n", strerror(-r));
+ return EXIT_FAILURE;
+ }
+ }
+
+ /* Do some daemon work here … */
+ sleep(5);
+ }
+
+ return EXIT_SUCCESS;
+}