Return early when remote DISPLAY variable set

When DISPLAY is set to a remote display, the remote display server
is down/unreachable and you su from user to root (or some other user),
this can take ~30 seconds+ to complete.

ps reveals ck-get-x11-server-pid is waiting on network connection to
the xserver that will eventually timeout.

Since it is impossible to get the process ID of the other end of a
TCP connection (manpages say Xlib uses TCP connections when
DISPLAY has a hostname: part) this patch skips getting the PID for
remote DISPLAYs.

References:
If the DISPLAY variable has a hostname component, e.g.
"remotehost:0.0", XOpenDisplay will use a TCP connection to it,
and the fd it returns later will be a TCP socket.
(http://tronche.com/gui/x/xlib/display/opening.html)

It is only possible to get the peer socket's PID for UNIX domain
sockets. (E.g. On linux, SO_PEERCRED is only usable for UNIX domain
sockets (i.e. PF_UNIX) )( http://linux.die.net/man/7/socket)

Bug report and patch provided by Joe Mullally.
https://bugs.launchpad.net/ubuntu/+source/consolekit/+bug/517323

1 files changed, 5 insertions, 0 deletions

diff --git a/tools/ck-get-x11-server-pid.c b/tools/ck-get-x11-server-pid.c
index 3324164..036a12a 100644
--- a/tools/ck-get-x11-server-pid.c
+++ b/tools/ck-get-x11-server-pid.c
@@ -47,6 +47,11 @@ display_init (int *argc, char ***argv)
                 exit (1);
         }
 
+        if (display_name[0] != ':' && g_strrstr(display_name, ":") != NULL) {
+                g_warning ("DISPLAY is not a UNIX domain socket, can't get PID");
+                exit (1);
+        }
+
         xdisplay = XOpenDisplay (display_name);
         if (xdisplay == NULL) {
                 g_warning ("cannot open display: %s", display_name ? display_name : "");