Mark missing host name separately from flags.

This simplifies the syslog() path a little, and allows us to express
"host name should be cached but no value is set.".

Because host name field is already emptied by default and in closelog (),
this also means uncached data is used before openlog () and after
closelog ().

Signed-off-by: Miloslav Trmač <mitr@redhat.com>

2 files changed, 15 insertions, 7 deletions

diff --git a/lib/umberlog.c b/lib/umberlog.c
index 877818a..fa5934f 100644
--- a/lib/umberlog.c
+++ b/lib/umberlog.c
@@ -73,7 +73,7 @@ static struct
   pid_t pid;			/* -1 = no value cached */
   uid_t uid;			/* (uid_t)-1 = no value cached */
   gid_t gid;			/* (gid_t)-1 = no value cached */
-  char hostname[_POSIX_HOST_NAME_MAX + 1];
+  char hostname[_POSIX_HOST_NAME_MAX + 1]; /* "" = no value cached */
 } ul_process_data =
   {
     PTHREAD_MUTEX_INITIALIZER, 0, LOG_USER, NULL,
@@ -122,7 +122,10 @@ ul_openlog (const char *ident, int option, int facility)
       ul_process_data.gid = getgid ();
       ul_process_data.uid = getuid ();
     }
-  gethostname (ul_process_data.hostname, _POSIX_HOST_NAME_MAX);
+  if ((ul_process_data.flags & LOG_UL_NOCACHE) != 0)
+    ul_process_data.hostname[0] = '\0';
+  else
+    gethostname (ul_process_data.hostname, _POSIX_HOST_NAME_MAX);
   pthread_mutex_unlock (&ul_process_data.lock);
 }
 
@@ -208,11 +211,13 @@ _get_gid (void)
 }
 
 static inline const char *
-_get_hostname (void)
+_get_hostname (char *hostname_buffer)
 {
-  if (ul_process_data.flags & LOG_UL_NOCACHE)
-    gethostname (ul_process_data.hostname, _POSIX_HOST_NAME_MAX);
-  return ul_process_data.hostname;
+  if (ul_process_data.hostname[0] != '\0')
+    return ul_process_data.hostname;
+
+  gethostname (hostname_buffer, _POSIX_HOST_NAME_MAX);
+  return hostname_buffer;
 }
 
 static inline const char *
@@ -520,6 +525,7 @@ _ul_json_append_timestamp (ul_buffer_t *buffer)
 static inline ul_buffer_t *
 _ul_discover (ul_buffer_t *buffer, int priority)
 {
+  char hostname_buffer[_POSIX_HOST_NAME_MAX + 1];
   const char *ident;
 
   if (ul_process_data.flags & LOG_UL_NODISCOVER)
@@ -531,7 +537,7 @@ _ul_discover (ul_buffer_t *buffer, int priority)
                             "priority", "%s", _find_prio (priority),
                             "uid", "%d", _get_uid (),
                             "gid", "%d", _get_gid (),
-                            "host", "%s", _get_hostname (),
+                            "host", "%s", _get_hostname (hostname_buffer),
                             NULL);
   if (buffer == NULL)
     return buffer;
diff --git a/t/test_umberlog.c b/t/test_umberlog.c
index 8a47ab1..cc437cf 100644
--- a/t/test_umberlog.c
+++ b/t/test_umberlog.c
@@ -295,6 +295,7 @@ START_TEST (test_closelog)
     verify_value_differs (jo, "uid", "0");
   if (getgid () != 0)
     verify_value_differs (jo, "gid", "0");
+  verify_value_differs (jo, "host", "");
 
   json_object_put (jo);
 }
@@ -354,6 +355,7 @@ START_TEST (test_openlog_defaults)
     verify_value_differs (jo, "uid", "0");
   if (getgid () != 0)
     verify_value_differs (jo, "gid", "0");
+  verify_value_differs (jo, "host", "");
   json_object_put (jo);
 
   closelog ();