1 files changed, 64 insertions, 0 deletions
diff --git a/include/sd-notify.h b/include/sd-notify.h
new file mode 100644
index 0000000..be284f6
--- /dev/null
+++ b/include/sd-notify.h
@@ -0,0 +1,64 @@
+/* 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 <stdlib.h>
+#include <stdio.h>
+#include <sys/socket.h>
+#include <sys/un.h>
+#include <unistd.h>
+
+static int sd_notify(int ignore, 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;
+    const char *socket_path;
+    int fd = -1;
+    int rc = 1;
+
+    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;
+
+    ssize_t written = sendto(fd, message, message_length, 0,
+			     &socket_addr.sa, offsetof(struct sockaddr_un, sun_path) + path_length);
+    if (written != (ssize_t) message_length)
+	rc = written < 0 ? -errno : -EPROTO;
+
+    close(fd);
+    return rc;
+}