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dbus-launch: If no X11, look for existing bus before failing

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What we are aiming for here is that `dbus-launch --autolaunch` will
exit with an error if it would have been unable to advertise the bus
in a way that will be picked up by other instances of itself, so that
we don't get a proliferation of autolaunched dbus-launch instances,
each with its own dbus-daemon, and none of them talking to the others.

However, we don't need to do that *immediately*: we can try to look for
an existing instance first. If we find one, then we can assume that
it's suitable for use, even if X11 autolaunching was disabled at
compile-time or if connecting to the X server failed at runtime. We
only need to bail out if we get to the point where we are ready to start
forking child processes.

This lets systemd users run `dbus-launch --autolaunch` to find a
systemd-managed dbus-daemon, even if X11 autolaunching is disabled.
When combined with the previous commit, it also lets macOS users run
`dbus-launch --autolaunch` to find a launchd-managed dbus-daemon.

Resolves: dbus/dbus#385
Signed-off-by: Simon McVittie <smcv@collabora.com>
This commit is contained in:
Simon McVittie 2022-03-16 13:30:33 +00:00
parent d847b5f6ae
commit 363919696a
1 changed files with 48 additions and 32 deletions
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80
tools/dbus-launch.c
View file

@ -1009,19 +1009,6 @@ main (int argc, char **argv)
if (autolaunch)
{
#ifndef DBUS_BUILD_X11
fprintf (stderr, "Autolaunch requested, but X11 support not compiled in.\n"
"Cannot continue.\n");
exit (1);
#else /* DBUS_BUILD_X11 */
#ifndef DBUS_ENABLE_X11_AUTOLAUNCH
fprintf (stderr, "X11 autolaunch support disabled at compile time.\n");
exit (1);
#else /* DBUS_ENABLE_X11_AUTOLAUNCH */
char *address;
pid_t pid;
long wid;
if (get_machine_uuid () == NULL)
{
fprintf (stderr, "Machine UUID not provided as arg to --autolaunch\n");
@ -1062,6 +1049,7 @@ main (int argc, char **argv)
_dbus_string_free (&existing_bus);
}
#if defined(DBUS_BUILD_X11) && defined(DBUS_ENABLE_X11_AUTOLAUNCH)
verbose ("Autolaunch enabled (using X11).\n");
if (!exit_with_x11)
{
@ -1069,27 +1057,38 @@ main (int argc, char **argv)
exit_with_x11 = TRUE;
}
if (!x11_init ())
{
fprintf (stderr, "Autolaunch error: X11 initialization failed.\n");
exit (1);
}
if (x11_init ())
{
char *address;
pid_t pid;
long wid;
if (!x11_get_address (&address, &pid, &wid))
{
fprintf (stderr, "Autolaunch error: X11 communication error.\n");
exit (1);
}
_dbus_assert (xdisplay != NULL);
verbose ("Connected to X11 display\n");
if (address != NULL)
{
verbose ("dbus-daemon is already running. Returning existing parameters.\n");
pass_info (runprog, address, pid, wid, c_shell_syntax,
bourne_shell_syntax, binary_syntax, argc, argv, remaining_args);
exit (0);
}
#endif /* DBUS_ENABLE_X11_AUTOLAUNCH */
#endif /* DBUS_BUILD_X11 */
if (!x11_get_address (&address, &pid, &wid))
{
fprintf (stderr, "dbus-launch: Autolaunch error: X11 communication error.\n");
exit (1);
}
if (address != NULL)
{
verbose ("dbus-daemon is already running. Returning existing parameters.\n");
pass_info (runprog, address, pid, wid, c_shell_syntax,
bourne_shell_syntax, binary_syntax, argc, argv,
remaining_args);
exit (0);
}
}
else
{
verbose ("Failed to connect to X11 display\n");
_dbus_assert (xdisplay == NULL);
}
#else
verbose ("X11 autolaunch disabled at compile time, skipping that.\n");
#endif /* DBUS_BUILD_X11 && DBUS_ENABLE_X11_AUTOLAUNCH */
}
else if (exit_with_x11)
{
@ -1124,6 +1123,23 @@ main (int argc, char **argv)
}
#endif /* DBUS_BUILD_X11 */
if (autolaunch && !existing_bus_supported)
{
#if defined(DBUS_BUILD_X11) && defined(DBUS_ENABLE_X11_AUTOLAUNCH)
if (xdisplay == NULL)
{
fprintf (stderr,
"dbus-launch: No existing session bus was found, and "
"failed to connect to X11 display.\n");
exit (1);
}
#else
fprintf (stderr,
"dbus-launch: No existing session bus was found, and X11 "
"autolaunch support was disabled at compile time.\n");
exit (1);
#endif
}
if (pipe (bus_pid_to_launcher_pipe) < 0 ||
pipe (bus_address_to_launcher_pipe) < 0 ||