[libvirt] [PATCH 2/8] virlog: Introduce virLog{Get, Set}DefaultOutput

[Erik Skultety]

The reason why we need something like this lies in the daemon's config where we
treat the @log_outputs variable (but not just this one) the very same way in
cases where the variable was explicitly set to an empty string or wasn't set at
all, using some default output in both. The selection of a default output
depends on whether the daemon runs daemonized or not. Before the runtime
logging APIs can be enabled, we need to make sure that the behaviour will be the
same in case someone tries to replace the set of logging outputs with an empty
string, hoping that it would turn the logging off.
In order to be able to reset the logging output to some default we either need
to store the daemon mode or we store a default logging output which we'll be
able to fallback to later. This patch goes for the latter by introducing new
methods to set and retrieve the default logging output.

Signed-off-by: Erik Skultety <eskultet at redhat.com>
---
 src/libvirt_private.syms |  2 ++
 src/util/virlog.c        | 94 ++++++++++++++++++++++++++++++++++++++++++++++++
 src/util/virlog.h        |  2 ++
 3 files changed, 98 insertions(+)

diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms
index 162fda5..5b0e07d 100644
--- a/src/libvirt_private.syms
+++ b/src/libvirt_private.syms
@@ -1877,6 +1877,7 @@ virLogFilterFree;
 virLogFilterListFree;
 virLogFilterNew;
 virLogFindOutput;
+virLogGetDefaultOutput;
 virLogGetDefaultPriority;
 virLogGetFilters;
 virLogGetNbFilters;
@@ -1895,6 +1896,7 @@ virLogParseOutputs;
 virLogPriorityFromSyslog;
 virLogProbablyLogMessage;
 virLogReset;
+virLogSetDefaultOutput;
 virLogSetDefaultPriority;
 virLogSetFilters;
 virLogSetFromEnv;
diff --git a/src/util/virlog.c b/src/util/virlog.c
index 8f831fc..4ac72dc 100644
--- a/src/util/virlog.c
+++ b/src/util/virlog.c
@@ -50,6 +50,7 @@
 #include "virtime.h"
 #include "intprops.h"
 #include "virstring.h"
+#include "configmake.h"
 
 /* Journald output is only supported on Linux new enough to expose
  * htole64.  */
@@ -105,6 +106,7 @@ struct _virLogOutput {
     char *name;
 };
 
+static char *virLogDefaultOutput;
 static virLogOutputPtr *virLogOutputs;
 static size_t virLogNbOutputs;
 
@@ -146,6 +148,98 @@ virLogUnlock(void)
     virMutexUnlock(&virLogMutex);
 }
 
+static int
+virLogSetDefaultOutputToStderr(void)
+{
+    char *tmp = NULL;
+    if (virAsprintf(&tmp, "%d:stderr", virLogGetDefaultPriority()) < 0)
+        return -1;
+
+    virLogDefaultOutput = tmp;
+    return 0;
+}
+
+static int
+virLogSetDefaultOutputToJournald(void)
+{
+    char *tmp = NULL;
+    virLogPriority priority = virLogDefaultPriority;
+
+    /* By default we don't want to log too much stuff into journald as
+     * it may employ rate limiting and thus block libvirt execution. */
+    if (priority == VIR_LOG_DEBUG)
+        priority = VIR_LOG_INFO;
+
+    if (virAsprintf(&tmp, "%d:journald", priority) < 0)
+        return -1;
+
+    virLogDefaultOutput = tmp;
+    return 0;
+}
+
+static int
+virLogSetDefaultOutputToFile(bool privileged)
+{
+    int ret = -1;
+    char *tmp = NULL;
+    char *logdir = NULL;
+
+    if (privileged) {
+        if (virAsprintf(&tmp, "%d:file:%s/log/libvirt/libvirtd.log",
+                        virLogGetDefaultPriority(),
+                        LOCALSTATEDIR) < 0)
+            goto cleanup;
+    } else {
+        if (!(logdir = virGetUserCacheDirectory()))
+            goto cleanup;
+
+        mode_t old_umask = umask(077);
+        if (virFileMakePath(logdir) < 0) {
+            umask(old_umask);
+            goto cleanup;
+        }
+        umask(old_umask);
+
+        if (virAsprintf(&tmp, "%d:file:%s/libvirtd.log",
+                        virLogGetDefaultPriority(), logdir) < 0)
+            goto cleanup;
+    }
+
+    virLogDefaultOutput = tmp;
+    tmp = NULL;
+    ret = 0;
+ cleanup:
+    VIR_FREE(tmp);
+    VIR_FREE(logdir);
+    return ret;
+}
+
+/* this should be run exactly once at daemon startup, so no locking is
+ * necessary
+ */
+int
+virLogSetDefaultOutput(virLogDestination dest, bool privileged)
+{
+    switch (dest) {
+    case VIR_LOG_TO_STDERR:
+        return virLogSetDefaultOutputToStderr();
+    case VIR_LOG_TO_JOURNALD:
+        return virLogSetDefaultOutputToJournald();
+    case VIR_LOG_TO_FILE:
+        return virLogSetDefaultOutputToFile(privileged);
+    case VIR_LOG_TO_SYSLOG:
+    case VIR_LOG_TO_OUTPUT_LAST:
+        break;
+    }
+
+    return 0;
+}
+
+char *
+virLogGetDefaultOutput(void)
+{
+    return virLogDefaultOutput;
+}
 
 static const char *
 virLogPriorityString(virLogPriority lvl)
diff --git a/src/util/virlog.h b/src/util/virlog.h
index 3f2d422..d6eb693 100644
--- a/src/util/virlog.h
+++ b/src/util/virlog.h
@@ -189,6 +189,8 @@ void virLogFilterFree(virLogFilterPtr filter);
 void virLogFilterListFree(virLogFilterPtr *list, int count);
 int virLogSetOutputs(const char *outputs) ATTRIBUTE_NONNULL(1);
 int virLogSetFilters(const char *filters);
+char *virLogGetDefaultOutput(void);
+int virLogSetDefaultOutput(virLogDestination dest, bool privileged);
 
 /*
  * Internal logging API
-- 
2.5.5