[libvirt] [PATCH 3/3] Don't ignore all dbus connection errors

[Daniel P. Berrange]

From: "Daniel P. Berrange" <berrange at redhat.com>

Previous commit

  commit 7ada155cdf2bbfac16ce08f64abb455a940e2cf7
  Author: Gao feng <gaofeng at cn.fujitsu.com>
  Date:   Wed Sep 11 11:15:02 2013 +0800

    DBus: introduce virDBusIsServiceEnabled

Made the cgroups code fallback to non-systemd based setup
when dbus is not running. It was too big a hammer though,
as it did not check what error code was received when the
dbus connection failed. Thus it silently ignored serious
errors from dbus such as "too many client connections",
which should always be treated as fatal.

We only want to ignore errors if the dbus unix socket does
not exist, or if nothing is listening on it.

Signed-off-by: Daniel P. Berrange <berrange at redhat.com>
---
 src/nwfilter/nwfilter_driver.c |  5 +++--
 src/util/virdbus.c             | 22 +++++++++++++++++++---
 src/util/virsystemd.c          |  6 ++++--
 3 files changed, 26 insertions(+), 7 deletions(-)

diff --git a/src/nwfilter/nwfilter_driver.c b/src/nwfilter/nwfilter_driver.c
index d25c6f2..6602d73 100644
--- a/src/nwfilter/nwfilter_driver.c
+++ b/src/nwfilter/nwfilter_driver.c
@@ -175,8 +175,9 @@ nwfilterStateInitialize(bool privileged,
     DBusConnection *sysbus = NULL;
 
 #if WITH_DBUS
-    if (virDBusHasSystemBus())
-        sysbus = virDBusGetSystemBus();
+    if (virDBusHasSystemBus() &&
+        !(sysbus = virDBusGetSystemBus()))
+        return -1;
 #endif /* WITH_DBUS */
 
     if (VIR_ALLOC(driverState) < 0)
diff --git a/src/util/virdbus.c b/src/util/virdbus.c
index dc4ace0..4e4c267 100644
--- a/src/util/virdbus.c
+++ b/src/util/virdbus.c
@@ -111,14 +111,29 @@ virDBusGetSystemBus(void)
 }
 
 
+/**
+ * virDBusHasSystemBus:
+ *
+ * Check if dbus system bus is running. This does not
+ * imply that we have a connection. DBus might be running
+ * and refusing connections due to its client limit. The
+ * latter must be treated as a fatal error.
+ *
+ * Return false if dbus is not available, true if probably available.
+ */
 bool
 virDBusHasSystemBus(void)
 {
     if (virDBusGetSystemBusInternal())
         return true;
 
-    VIR_DEBUG("System DBus not available: %s", NULLSTR(systemdbuserr.message));
-    return false;
+    if (systemdbuserr.name &&
+        (STREQ(systemdbuserr.name, "org.freedesktop.DBus.Error.FileNotFound") ||
+         STREQ(systemdbuserr.name, "org.freedesktop.DBus.Error.NoServer"))) {
+        VIR_DEBUG("System DBus not available: %s", NULLSTR(systemdbuserr.message));
+        return false;
+    }
+    return true;
 }
 
 
@@ -1257,7 +1272,8 @@ int virDBusIsServiceEnabled(const char *name)
     if (!virDBusHasSystemBus())
         return -2;
 
-    conn = virDBusGetSystemBus();
+    if (!(conn = virDBusGetSystemBus()))
+        return -1;
 
     if (virDBusCallMethod(conn,
                           &reply,
diff --git a/src/util/virsystemd.c b/src/util/virsystemd.c
index 1ba37cc..503fff7 100644
--- a/src/util/virsystemd.c
+++ b/src/util/virsystemd.c
@@ -169,7 +169,8 @@ int virSystemdCreateMachine(const char *name,
     if (ret < 0)
         return ret;
 
-    conn = virDBusGetSystemBus();
+    if (!(conn = virDBusGetSystemBus()))
+        return -1;
 
     ret = -1;
     if (!(machinename = virSystemdMakeMachineName(name, drivername, privileged)))
@@ -267,7 +268,8 @@ int virSystemdTerminateMachine(const char *name,
     if (ret < 0)
         return ret;
 
-    conn = virDBusGetSystemBus();
+    if (!(conn = virDBusGetSystemBus()))
+        return -1;
 
     ret = -1;
     if (!(machinename = virSystemdMakeMachineName(name, drivername, privileged)))
-- 
1.8.3.1