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>

5 files changed, 69 insertions, 26 deletions

diff --git a/nx-X11/programs/Xserver/dix/globals.c b/nx-X11/programs/Xserver/dix/globals.c
index a0af50fa8..5a3e22c26 100644
--- a/nx-X11/programs/Xserver/dix/globals.c
+++ b/nx-X11/programs/Xserver/dix/globals.c
@@ -149,6 +149,7 @@ int defaultColorVisualClass = -1;
 int monitorResolution = 0;
 
 char *display;
+int displayfd;
 
 CARD32 TimeOutValue = DEFAULT_TIMEOUT * MILLI_PER_SECOND;
 int	argcGlobal;
diff --git a/nx-X11/programs/Xserver/hw/nxagent/man/nxagent.1 b/nx-X11/programs/Xserver/hw/nxagent/man/nxagent.1
index af5fc88f8..66f25b438 100644
--- a/nx-X11/programs/Xserver/hw/nxagent/man/nxagent.1
+++ b/nx-X11/programs/Xserver/hw/nxagent/man/nxagent.1
@@ -178,6 +178,13 @@ different from the user's real uid.
 .B \-core
 causes the server to generate a core dump on fatal errors.
 .TP 8
+.B \-displayfd \fIfd\fP
+specifies a file descriptor in the launching process.  Rather than specify
+a display number, the X server will attempt to listen on successively higher
+display numbers, and upon finding a free one, will write the port number back
+on this file descriptor as a newline-terminated string.  The \-pn option is
+ignored when using \-displayfd.
+.TP 8
 .B \-deferglyphs \fIwhichfonts\fP
 specifies the types of fonts for which the server should attempt to use
 deferred glyph loading.  \fIwhichfonts\fP can be all (all fonts),
diff --git a/nx-X11/programs/Xserver/include/opaque.h b/nx-X11/programs/Xserver/include/opaque.h
index bd286ba12..8f98bf1be 100644
--- a/nx-X11/programs/Xserver/include/opaque.h
+++ b/nx-X11/programs/Xserver/include/opaque.h
@@ -52,6 +52,7 @@ extern int defaultScreenSaverAllowExposures;
 extern int argcGlobal;
 extern char **argvGlobal;
 extern char *display;
+extern int displayfd;
 
 extern int defaultBackingStore;
 extern Bool disableBackingStore;
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;