Add ability to set controller for specific bridges

Some applications would prefer that the controller only be enabled for
a subset of bridges.  This commit introduces an alternative syntax for
the XAPI vSwitchController key to enable the specification of such a
configuration.

The implementation of the configuration is currently a hack.  The
problem is that some bridges (especially internal bridges) are only
created when a VIF is added to them.  This means that attempting to
set the controller on boot as we used to do won't work.  Ideally we
would should hook the creation of the bridge and set the controller at
that time.  However, in XenServer 5.5 I can't find an appropriate
place to hook to do so.

To meet immediate requirements, this commit hacks the startup-based
approach by spawning background processes that watch for the creation
of the bridge and set the controller when it becomes available.  We'll
have to replace it with a better and more robust solution ASAP.

diff --git a/xenserver/etc_xapi.d_plugins_vswitch-cfg-update b/xenserver/etc_xapi.d_plugins_vswitch-cfg-update
index 1ae767f..7f49e33 100755 (executable)
--- a/xenserver/etc_xapi.d_plugins_vswitch-cfg-update
+++ b/xenserver/etc_xapi.d_plugins_vswitch-cfg-update
@@ -49,6 +49,23 @@ def update(session, args):
         controller = pool["other_config"]["vSwitchController"]
     except KeyError, e:
         controller = ""
+    if controller == "do-not-update":
+        return "XAPI key set to do-not-update"
+    if controller.startswith("for-bridges|"):
+        l = controller.split("|")[1:]
+        for netctrl in l:
+            xapiNet = session.xenapi.network
+            n, t = netctrl.split("=")
+            blist = xapiNet.get_by_name_label(n)
+            if len(blist) == 0:
+                # If there is no bridge for the network, just keep
+                # going so we bring up as much as possible.
+                continue
+            elif len(blist) > 1:
+                raise XenAPIPlugin.Failure("TOO_MANY_MATCHING_NETWORKS", [n,blist])
+            b = xapiNet.get_bridge(blist[0])
+            setBrControllerCfg(b, t)
+        return "Completed setting controllers on specific bridges"
     currentController = vswitchCurrentController()
     if controller == "" and currentController != "":
         delete_cacert()
@@ -60,7 +77,7 @@ def update(session, args):
         return "Successfully set controller to " + controller
     else:
         return "No change to configuration"
-        
+
 def vswitchCurrentController():
     controller = vswitchCfgQuery("get-controller")
     if controller == "":
@@ -73,7 +90,70 @@ def vswitchCurrentController():
 def removeControllerCfg():
     vswitchCfgMod(["--", "del-controller",
                    "--", "del-ssl"])
-                                       
+
+def setBrControllerCfg(br, target):
+    # Terrible hack... When this is run at boot the required bridges
+    # may not be present.  So, we fork a process for each bridge that
+    # needs to be set which sits around in the background and updates
+    # it when it becomes available, finally timing out after a long
+    # interval if it never becomes available.
+    #
+    # The right way to do this is to hook the bridge creation somehow
+    # but I don't believe this is possible in XenServer 5.5 without
+    # either listening to XAPI events or writing it in C code in
+    # brcompatd.
+    import time
+    import syslog
+    import resource
+
+    p = os.fork()
+    if p != 0:
+        return
+
+    os.setsid()
+    p = os.fork()
+    if p != 0:
+        sys.exit(0)
+
+    os.chdir("/")
+    os.umask(0)
+    maxfd = resource.getrlimit(resource.RLIMIT_NOFILE)[1]
+    if maxfd == resource.RLIM_INFINITY:
+        maxfd = 1024
+    for fd in range(0, maxfd):
+        try:
+            os.close(fd)
+        except OSError:
+            pass
+    os.open("/dev/null", os.O_RDWR)
+    os.dup2(0, 1)
+    os.dup2(0, 2)
+
+    syslog.openlog("vswitch-cfg-update", syslog.LOG_PID)
+    syslog.syslog(syslog.LOG_INFO,
+                  "Started background process waiting on bridge %s" % (br,))
+
+    count = 0
+    error = None
+    sleep_time = 10
+    while count < 60:
+        count += 1
+        try:
+            vswitchCfgMod(["--", "del-controller", br,
+                           "--", "set-controller", br, target,
+                           "--", "set-fail-mode", br, "secure"])
+        except XenAPIPlugin.Failure, e:
+            error = e
+            syslog.syslog(syslog.LOG_INFO,
+                          "Attempt to set br %s controller failed" % (br,))
+            time.sleep(sleep_time)
+            continue
+        syslog.syslog(syslog.LOG_INFO,
+                      "Successfully set br %s controller to %s" % (br, repr(target)))
+        return
+    syslog.syslog(syslog.LOG_ERR,
+                  "Giving up on setting br %s controller" % (br,))
+
 def setControllerCfg(controller):
     vswitchCfgMod(["--", "del-controller",
                    "--", "del-ssl",