[PATCH 3/6] os: Add a mechanism to prevent creating any listen sockets

[Kristian Høgsberg]

A socket-activated server will receive its listening sockets from the
parent process and should not create its own sockets.  This patch
introduces a NoListen flag that can be set by a DDX to prevent
the server from creating the sockets.

Signed-off-by: Kristian Høgsberg <krh at bitplanet.net>
Reviewed-by: Daniel Stone <daniel at fooishbar.org>
---
 include/opaque.h | 1 +
 os/connection.c  | 9 +++++++--
 os/utils.c       | 4 ++--
 3 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/include/opaque.h b/include/opaque.h
index 73d40c3..7ec1d85 100644
--- a/include/opaque.h
+++ b/include/opaque.h
@@ -74,5 +74,6 @@ extern _X_EXPORT Bool whiteRoot;
 extern _X_EXPORT Bool bgNoneRoot;
 
 extern _X_EXPORT Bool CoreDump;
+extern _X_EXPORT Bool NoListenAll;
 
 #endif                          /* OPAQUE_H */
diff --git a/os/connection.c b/os/connection.c
index 400c542..b50f9e9 100644
--- a/os/connection.c
+++ b/os/connection.c
@@ -138,6 +138,7 @@ fd_set OutputPending;           /* clients with reply/event data ready to go */
 int MaxClients = 0;
 Bool NewOutputPending;          /* not yet attempted to write some new output */
 Bool AnyClientsWriteBlocked;    /* true if some client blocked on write */
+Bool NoListenAll;               /* Don't establish any listening sockets */
 
 static Bool RunFromSmartParent; /* send SIGUSR1 to parent process */
 Bool RunFromSigStopParent;      /* send SIGSTOP to our own process; Upstart (or
@@ -406,7 +407,10 @@ CreateWellKnownSockets(void)
     /* 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 (NoListenAll) {
+        ListenTransCount = 0;
+    }
+    else if (display) {
         if (TryCreateSocket(atoi(display), &partial) &&
             ListenTransCount >= 1)
             if (!PartialNetwork && partial)
@@ -440,9 +444,10 @@ CreateWellKnownSockets(void)
             DefineSelf (fd);
     }
 
-    if (!XFD_ANYSET(&WellKnownConnections))
+    if (!XFD_ANYSET(&WellKnownConnections) && !NoListenAll)
         FatalError
             ("Cannot establish any listening sockets - Make sure an X server isn't already running");
+
 #if !defined(WIN32)
     OsSignal(SIGPIPE, SIG_IGN);
     OsSignal(SIGHUP, AutoResetServer);
diff --git a/os/utils.c b/os/utils.c
index 497779b..c513968 100644
--- a/os/utils.c
+++ b/os/utils.c
@@ -270,7 +270,7 @@ LockServer(void)
     int len;
     char port[20];
 
-    if (nolock)
+    if (nolock || NoListenAll)
         return;
     /*
      * Path names
@@ -390,7 +390,7 @@ LockServer(void)
 void
 UnlockServer(void)
 {
-    if (nolock)
+    if (nolock || NoListenAll)
         return;
 
     if (!StillLocking) {
-- 
1.9.0