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-rw-r--r--src/shared/util.c85
1 files changed, 85 insertions, 0 deletions
diff --git a/src/shared/util.c b/src/shared/util.c
index 73e0a290b8..7f41fc4f5e 100644
--- a/src/shared/util.c
+++ b/src/shared/util.c
@@ -6035,3 +6035,88 @@ int fd_inc_rcvbuf(int fd, size_t n) {
return 1;
}
+
+int fork_agent(pid_t *pid, const char *path, ...) {
+ pid_t parent_pid, agent_pid;
+ int fd;
+ bool stdout_is_tty, stderr_is_tty;
+ unsigned n, i;
+ va_list ap;
+ char **l;
+
+ assert(pid);
+ assert(path);
+
+ parent_pid = getpid();
+
+ /* Spawns a temporary TTY agent, making sure it goes away when
+ * we go away */
+
+ agent_pid = fork();
+ if (agent_pid < 0)
+ return -errno;
+
+ if (agent_pid != 0) {
+ *pid = agent_pid;
+ return 0;
+ }
+
+ /* In the child:
+ *
+ * Make sure the agent goes away when the parent dies */
+ if (prctl(PR_SET_PDEATHSIG, SIGTERM) < 0)
+ _exit(EXIT_FAILURE);
+
+ /* Check whether our parent died before we were able
+ * to set the death signal */
+ if (getppid() != parent_pid)
+ _exit(EXIT_SUCCESS);
+
+ /* Don't leak fds to the agent */
+ close_all_fds(NULL, 0);
+
+ stdout_is_tty = isatty(STDOUT_FILENO);
+ stderr_is_tty = isatty(STDERR_FILENO);
+
+ if (!stdout_is_tty || !stderr_is_tty) {
+ /* Detach from stdout/stderr. and reopen
+ * /dev/tty for them. This is important to
+ * ensure that when systemctl is started via
+ * popen() or a similar call that expects to
+ * read EOF we actually do generate EOF and
+ * not delay this indefinitely by because we
+ * keep an unused copy of stdin around. */
+ fd = open("/dev/tty", O_WRONLY);
+ if (fd < 0) {
+ log_error("Failed to open /dev/tty: %m");
+ _exit(EXIT_FAILURE);
+ }
+
+ if (!stdout_is_tty)
+ dup2(fd, STDOUT_FILENO);
+
+ if (!stderr_is_tty)
+ dup2(fd, STDERR_FILENO);
+
+ if (fd > 2)
+ close(fd);
+ }
+
+ /* Count arguments */
+ va_start(ap, path);
+ for (n = 0; va_arg(ap, char*); n++)
+ ;
+ va_end(ap);
+
+ /* Allocate strv */
+ l = alloca(sizeof(char *) * (n + 1));
+
+ /* Fill in arguments */
+ va_start(ap, path);
+ for (i = 0; i <= n; i++)
+ l[i] = va_arg(ap, char*);
+ va_end(ap);
+
+ execv(path, l);
+ _exit(EXIT_FAILURE);
+}