/* SPDX-License-Identifier: LGPL-2.1-or-later */
/* Copied and adapted from systemd source code. */

#define _GNU_SOURCE 1

#include <assert.h>
#include <errno.h>
#include <signal.h>
#include <stddef.h>
#include <stdlib.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/un.h>

#include "sd-socket.h"
#define _cleanup_(f) __attribute__((cleanup(f)))

int sd_is_socket(int fd, int type, int listening) {
        struct stat st_fd;

        assert(fd >= 0);
        assert(type >= 0);

        if (fstat(fd, &st_fd) < 0)
                return -errno;

        if (!S_ISSOCK(st_fd.st_mode))
                return 0;

        if (type != 0) {
                int other_type = 0;
                socklen_t l = sizeof(other_type);

                if (getsockopt(fd, SOL_SOCKET, SO_TYPE, &other_type, &l) < 0)
                        return -errno;

                if (l != sizeof(other_type))
                        return -EINVAL;

                if (other_type != type)
                        return 0;
        }

        if (listening >= 0) {
                int accepting = 0;
                socklen_t l = sizeof(accepting);

                if (getsockopt(fd, SOL_SOCKET, SO_ACCEPTCONN, &accepting, &l) < 0)
                        return -errno;

                if (l != sizeof(accepting))
                        return -EINVAL;

                if (!accepting != !listening)
                        return 0;
        }

        return 1;
}

/* 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/ */

static void closep(int *fd) {
  if (!fd || *fd < 0)
    return;

  close(*fd);
  *fd = -1;
}

static int sd_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;

  /* Verify the argument first */
  if (!message)
    return -EINVAL;

  message_length = strlen(message);
  if (message_length == 0)
    return -EINVAL;

  /* If the variable is not set, the protocol is a noop */
  socket_path = getenv("NOTIFY_SOCKET");
  if (!socket_path)
    return 0; /* Not set? Nothing to do */

  /* 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! */
}

int sd_notify_ready(void) {
  return sd_notify("READY=1");
}

int sd_notify_stopping(void) {
  return sd_notify("STOPPING=1");
}