Added new backend plugin: ca_pre-demon called if backend is daemonized just prior to forking.

CHANGELOG.md

@@ -29,6 +29,7 @@
 
 ### Minor changes
 
+* Added new backend plugin: ca_pre-demon called if backend is daemonized just prior to forking.
 * Added XPATH functions `position`
 
 ### Corrected Bugs

apps/backend/backend_main.c

@@ -912,15 +912,19 @@ main(int    argc,
        demonized errors OK. Before this stage, errors are logged on stderr 
        also */
     if (foreground==0){
+	/* Call plugin callbacks just before fork/daemonization */
+	if (clixon_plugin_pre_daemon_all(h) < 0)
+            goto done;
   	clicon_log_init(__PROGRAM__, dbg?LOG_DEBUG:LOG_INFO,
 			logdst==CLICON_LOG_FILE?CLICON_LOG_FILE:CLICON_LOG_SYSLOG);
 	if (daemon(0, 0) < 0){
 	    fprintf(stderr, "config: daemon");
 	    exit(-1);
 	}
-	    
     }
-    /* Call plugin callbacks when in background and before dropped privileges */
+    /* Call plugin callbacks when in background and before dropped privileges
+     * Possibly this should be within the foreground==0 clause after daemon?
+     */
     if (clixon_plugin_daemon_all(h) < 0)
 	goto done;
 

apps/backend/backend_plugin.c

@@ -118,13 +118,65 @@ clixon_plugin_reset_all(clicon_handle h,
     return retval;
 }
 
+/*! Call single plugin "pre-" daemonize callback
+ * @param[in]  cp      Plugin handle
+ * @param[in]  h       Clixon handle
+ * @retval     0       OK
+ * @retval    -1       Error
+ */
+static int
+clixon_plugin_pre_daemon_one(clixon_plugin *cp,
+                             clicon_handle  h)
+{
+    int          retval = -1;
+    plgdaemon_t *fn;          /* Daemonize plugin callback function */
+
+    if ((fn = cp->cp_api.ca_pre_daemon) != NULL){
+        if (fn(h) < 0) {
+            if (clicon_errno < 0)
+                clicon_log(LOG_WARNING, "%s: Internal error: Pre-daemon callback in plugin:\
+ %s returned -1 but did not make a clicon_err call",
+                           __FUNCTION__, cp->cp_name);
+            goto done;
+        }
+    }
+    retval = 0;
+ done:
+    return retval;
+}
+
+/*! Call all plugins "pre-" daemonize callbacks
+ *
+ * This point in time is after "start" and before
+ * before daemonization/fork,
+ * It is not called if backend is started in daemon mode.
+ * @param[in]  h       Clicon handle
+ * @retval     0       OK
+ * @retval    -1       Error
+ */
+int
+clixon_plugin_pre_daemon_all(clicon_handle h)
+{
+    int            retval = -1;
+    clixon_plugin *cp = NULL;
+
+    /* Loop through all plugins, call callbacks in each */
+    while ((cp = clixon_plugin_each(h, cp)) != NULL) {
+        if (clixon_plugin_pre_daemon_one(cp, h) < 0)
+            goto done;
+    }
+    retval = 0;
+ done:
+    return retval;
+}
+
 /*! Call single plugin "post-" daemonize callback
  * @param[in]  cp      Plugin handle
  * @param[in]  h       Clixon handle
  * @retval     0       OK
  * @retval    -1       Error
  */
-int
+static int
 clixon_plugin_daemon_one(clixon_plugin *cp,
 			 clicon_handle  h)
 {
@@ -145,9 +197,15 @@ clixon_plugin_daemon_one(clixon_plugin *cp,
 }
     
 /*! Call all plugins "post-" daemonize callbacks
+ *                           
+ * This point in time is after "start" and after "pre-daemon" and
+ * after daemonization/fork, ie when
+ * daemon is in the background but before dropped privileges.
+ * In case of foreground mode (-F) it is still called but no fork has occured.
  * @param[in]  h       Clicon handle
  * @retval     0       OK
  * @retval    -1       Error
+ * @note Also called for non-background mode
  */
 int
 clixon_plugin_daemon_all(clicon_handle h)

apps/backend/backend_plugin.h

@@ -72,7 +72,7 @@ typedef struct {
 int clixon_plugin_reset_one(clixon_plugin *cp, clicon_handle h, char *db);
 int clixon_plugin_reset_all(clicon_handle h, char *db);
 
-int clixon_plugin_daemon_one(clixon_plugin *cp, clicon_handle h);
+int clixon_plugin_pre_daemon_all(clicon_handle h);
 int clixon_plugin_daemon_all(clicon_handle h);
 
 int clixon_plugin_statedata_all(clicon_handle h, yang_stmt *yspec, cvec *nsc, char *xpath, cxobj **xtop);

lib/clixon/clixon_plugin.h

@@ -107,11 +107,12 @@ typedef int (*clicon_upgrade_cb)(
  */
 typedef int (plgstart_t)(clicon_handle); /* Plugin start */
 
-/* Called just after a server has "daemonized", ie put in background.
+/* Called just before or after a server has "daemonized", ie put in background.             
  * Backend: If daemon privileges are dropped this callback is called *before* privileges are dropped.
- * If daemon is started in foreground (-F) it is still called.
+ * If daemon is started in foreground (-F): pre-daemon is not called, but post-daemon called
  */
-typedef int (plgdaemon_t)(clicon_handle);              /* Plugin daemonized */
+typedef int (plgdaemon_t)(clicon_handle);              /* Plugin pre/post daemonized */
+
 
 /* Called just before plugin unloaded. 
  */
@@ -219,6 +220,7 @@ struct clixon_plugin_api{
 	struct { /* netconf-specific */
 	} cau_netconf;
 	struct { /* backend-specific */
+            plgdaemon_t      *cb_pre_daemon;     /* Plugin just before daemonization */
             plgdaemon_t      *cb_daemon;         /* Plugin daemonized */
 	    plgreset_t       *cb_reset;          /* Reset system status */
 	    plgstatedata_t   *cb_statedata;      /* Get state data from plugin (backend only) */
@@ -239,6 +241,7 @@ struct clixon_plugin_api{
 #define ca_suspend        u.cau_cli.ci_suspend
 #define ca_interrupt      u.cau_cli.ci_interrupt
 #define ca_auth           u.cau_restconf.cr_auth
+#define ca_pre_daemon     u.cau_backend.cb_daemon
 #define ca_daemon         u.cau_backend.cb_daemon
 #define ca_reset          u.cau_backend.cb_reset
 #define ca_statedata      u.cau_backend.cb_statedata