[libvirt] [PATCH v2 08/20] virlog: Take a special care of syslog when setting new set of log outputs

[Erik Skultety]

Now that we're in the critical section, syslog connection can be re-opened
by issuing openlog, which is something that cannot be done beforehand, since
syslog keeps its file descriptor private and changing the tag earlier might
introduce a log inconsistency if something went wrong with preparing a new set
of logging outputs in order to replace the existing one.

Signed-off-by: Erik Skultety <eskultet at redhat.com>
---
 src/util/virlog.c | 23 +++++++++++++++++++++--
 1 file changed, 21 insertions(+), 2 deletions(-)

diff --git a/src/util/virlog.c b/src/util/virlog.c
index c0b8b9a..61e71a3 100644
--- a/src/util/virlog.c
+++ b/src/util/virlog.c
@@ -1794,16 +1794,35 @@ virLogFindOutput(virLogOutputPtr *outputs, size_t noutputs,
 int
 virLogDefineOutputs(virLogOutputPtr *outputs, size_t noutputs)
 {
+    int ret = -1;
+    size_t i;
+    char *tmp = NULL;
+
     if (virLogInitialize() < 0)
         return -1;
 
     virLogLock();
     virLogResetOutputs();
+
+    /* nothing can go wrong now (except for malloc) and we're also holding the
+     * lock so it's safe to call openlog and change the message tag */
+    for (i = 0; i < noutputs; i++) {
+        if (outputs[i]->dest == VIR_LOG_TO_SYSLOG) {
+            if (VIR_STRDUP_QUIET(tmp, outputs[i]->name) < 0)
+                goto cleanup;
+            VIR_FREE(current_ident);
+            current_ident = tmp;
+            openlog(current_ident, 0, 0);
+        }
+    }
+
     virLogOutputs = outputs;
     virLogNbOutputs = noutputs;
-    virLogUnlock();
 
-    return virLogNbOutputs;
+    ret = virLogNbOutputs;
+ cleanup:
+    virLogUnlock();
+    return ret;
 }
 
 
-- 
2.5.5