os: Add -displayfd option

 commit 88bacc49f06da5927f716869f5a32672a8297ed0
 Author: Chase Douglas <chase.douglas@canonical.com>
 Date:   Wed Apr 4 15:29:42 2012 -0700

    os: Add -displayfd option

    This option specifies a file descriptor in the launching process.  X
    will scan for an available display number and write that number back to
    the launching process, at the same time as SIGUSR1 generation.  This
    means display managers don't need to guess at available display numbers.
    As a consequence, if X fails to start when using -displayfd, it's not
    because the display was in use, so there's no point in retrying the X
    launch on a higher display number.

    Signed-off-by: Adam Jackson <ajax@redhat.com>
    Signed-off-by: Chase Douglas <chase.douglas@canonical.com>
    Reviewed-by: Julien Cristau <jcristau@debian.org>
    Tested-by: Julien Cristau <jcristau@debian.org>
    Reviewed-by: Alan Coopersmith <alan.coopersmith@oracle.com>
    Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>

 Backported-to-NX-by: Mike Gabriel <mike.gabriel@das-netzwerkteam.de>

2 files changed, 60 insertions, 26 deletions

diff --git a/nx-X11/programs/Xserver/os/connection.c b/nx-X11/programs/Xserver/os/connection.c
index 2fa8ad12d..6dc0ff64d 100644
--- a/nx-X11/programs/Xserver/os/connection.c
+++ b/nx-X11/programs/Xserver/os/connection.c
@@ -138,6 +138,7 @@ int NumNotifyWriteFd;           /* Number of NotifyFd members with write set */
 Bool NewOutputPending;		/* not yet attempted to write some new output */
 Bool AnyWritesPending;          /* true if some client blocked on write or NotifyFd with write */
 Bool RunFromSmartParent;	/* send SIGUSR1 to parent process */
+static char dynamic_display[7]; /* display name */
 Bool PartialNetwork;		/* continue even if unable to bind all addrs */
 static Pid_t ParentProcess;
 
@@ -359,6 +360,10 @@ void
 NotifyParentProcess(void)
 {
 #if !defined(WIN32)
+    if (dynamic_display[0]) {
+        write(displayfd, dynamic_display, strlen(dynamic_display));
+        close(displayfd);
+    }
     if (RunFromSmartParent) {
        if (ParentProcess > 1) {
            kill (ParentProcess, SIGUSR1);
@@ -367,6 +372,18 @@ NotifyParentProcess(void)
 #endif
 }
 
+static Bool
+TryCreateSocket(int num, int *partial)
+{
+    char port[20];
+
+    snprintf(port, sizeof(port), "%d", num);
+
+    return (_XSERVTransMakeAllCOTSServerListeners(port, partial,
+                                                  &ListenTransCount,
+                                                  &ListenTransConns) >= 0);
+}
+
 /*****************
  * CreateWellKnownSockets
  *    At initialization, create the sockets to listen on for new clients.
@@ -377,7 +394,6 @@ CreateWellKnownSockets(void)
 {
     int		i;
     int		partial;
-    char 	port[20];
 
     FD_ZERO(&AllSockets);
     FD_ZERO(&AllClients);
@@ -392,33 +408,41 @@ CreateWellKnownSockets(void)
 
     FD_ZERO (&WellKnownConnections);
 
-    sprintf (port, "%d", atoi (display));
-
-    if ((_XSERVTransMakeAllCOTSServerListeners (port, &partial,
-	&ListenTransCount, &ListenTransConns) >= 0) &&
-	(ListenTransCount >= 1))
-    {
-	if (!PartialNetwork && partial)
-	{
-	    FatalError ("Failed to establish all listening sockets");
-	}
-	else
-	{
-	    ListenTransFds = (int *) malloc (ListenTransCount * sizeof (int));
-
-	    for (i = 0; i < ListenTransCount; i++)
-	    {
-		int fd = _XSERVTransGetConnectionNumber (ListenTransConns[i]);
-		
-		ListenTransFds[i] = fd;
-		FD_SET (fd, &WellKnownConnections);
-
-		if (!_XSERVTransIsLocal (ListenTransConns[i]))
-		{
-		    DefineSelf (fd);
-		}
+    /* display is initialized to "0" by main(). It is then set to the display
+     * number if specified on the command line, or to NULL when the -displayfd
+     * option is used. */
+    if (display) {
+        if (TryCreateSocket(atoi(display), &partial) &&
+            ListenTransCount >= 1)
+            if (!PartialNetwork && partial)
+                FatalError ("Failed to establish all listening sockets");
+    }
+    else { /* -displayfd */
+	Bool found = 0;
+	for (i = 0; i < 65535 - X_TCP_PORT; i++) {
+	    if (TryCreateSocket(i, &partial) && !partial) {
+		found = 1;
+		break;
 	    }
+	    else
+		CloseWellKnownConnections();
 	}
+	if (!found)
+	    FatalError("Failed to find a socket to listen on");
+	snprintf(dynamic_display, sizeof(dynamic_display), "%d", i);
+	display = dynamic_display;
+    }
+
+    ListenTransFds = malloc(ListenTransCount * sizeof (int));
+
+    for (i = 0; i < ListenTransCount; i++) {
+        int fd = _XSERVTransGetConnectionNumber(ListenTransConns[i]);
+
+        ListenTransFds[i] = fd;
+        FD_SET(fd, &WellKnownConnections);
+
+        if (!_XSERVTransIsLocal(ListenTransConns[i]))
+            DefineSelf (fd);
     }
 
     if (!XFD_ANYSET (&WellKnownConnections))
diff --git a/nx-X11/programs/Xserver/os/utils.c b/nx-X11/programs/Xserver/os/utils.c
index 25cbb1e87..929549168 100644
--- a/nx-X11/programs/Xserver/os/utils.c
+++ b/nx-X11/programs/Xserver/os/utils.c
@@ -780,6 +780,16 @@ ProcessCommandLine(int argc, char *argv[])
 	    else
 		UseMsg();
 	}
+	else if (strcmp(argv[i], "-displayfd") == 0) {
+	    if (++i < argc) {
+		displayfd = atoi(argv[i]);
+		display = NULL;
+		nolock = TRUE;
+	    }
+	    else
+		UseMsg();
+	}
+
 #ifdef DPMSExtension
 	else if ( strcmp( argv[i], "dpms") == 0)
 	    DPMSEnabledSwitch = TRUE;