[PATCH v2 2/3] 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.  When NoListen is enabled, we
also disable the server lock checking, since the parent process is
responsible for checking the lock before picking the display name and
creating the sockets.

Signed-off-by: Kristian Høgsberg <krh at bitplanet.net>
---

The three patches in this series were split out from one big patch and I
lost the nolock detail when I split it.  This v2 of the patch adds it back.

Kristian

 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