Improve error handling for plugin_launch.

Improve messages and docstrings.
Set warning log level instead of debug log level for plugin_launch error messages.

src/attack.c

@@ -56,7 +56,6 @@
 #include <unistd.h>   /* for close() */
 
 #define ERR_HOST_DEAD -1
-#define ERR_CANT_FORK -2
 
 #define MAX_FORK_RETRIES 10
 /**
@@ -346,13 +345,14 @@ check_new_vhosts (void)
  * Does not launch a plugin twice if !save_kb_replay.
  *
  * @return ERR_HOST_DEAD if host died, ERR_CANT_FORK if forking failed,
- *         0 otherwise.
+ *         ERR_NO_FREE_SLOT if the process table is full, 0 otherwise.
  */
 static int
 launch_plugin (struct scan_globals *globals, struct scheduler_plugin *plugin,
                struct in6_addr *ip, GSList *vhosts, kb_t kb, kb_t main_kb)
 {
-  int optimize = prefs_get_bool ("optimize_test"), pid, ret = 0;
+  int optimize = prefs_get_bool ("optimize_test");
+  int launch_error, pid, ret = 0;
   char *oid, *name, *error = NULL, ip_str[INET6_ADDRSTRLEN];
   nvti_t *nvti;
 
@@ -428,14 +428,13 @@ launch_plugin (struct scan_globals *globals, struct scheduler_plugin *plugin,
 
   /* Update vhosts list and start the plugin */
   check_new_vhosts ();
-  pid = plugin_launch (globals, plugin, ip, vhosts, kb, main_kb, nvti);
-  if (pid < 0)
+  launch_error = 0;
+  pid = plugin_launch (globals, plugin, ip, vhosts, kb, main_kb, nvti,
+                       &launch_error);
+  if (launch_error == ERR_NO_FREE_SLOT || launch_error == ERR_CANT_FORK)
     {
       plugin->running_state = PLUGIN_STATUS_UNRUN;
-      if (pid == ERR_NO_FREE_SLOT)
-        ret = ERR_NO_FREE_SLOT;
-      else
-        ret = ERR_CANT_FORK;
+      ret = launch_error;
       goto finish_launch_plugin;
     }
 
@@ -524,25 +523,31 @@ attack_host (struct scan_globals *globals, struct in6_addr *ip, GSList *vhosts,
                 }
               else if (e == ERR_NO_FREE_SLOT)
                 {
-                  g_debug (
-                    "fork() failed for %s. No free slot to run a plugin.",
-                    plugin->oid);
-                  goto again;
+                  if (forks_retry < MAX_FORK_RETRIES)
+                    {
+                      forks_retry++;
+                      g_warning ("Launch failed for %s. No free slot available "
+                                 "in the internal process table for starting a "
+                                 "plugin.",
+                                 plugin->oid);
+                      fork_sleep (forks_retry);
+                      goto again;
+                    }
                 }
               else if (e == ERR_CANT_FORK)
                 {
                   if (forks_retry < MAX_FORK_RETRIES)
                     {
                       forks_retry++;
-                      g_debug (
+                      g_warning (
                         "fork() failed for %s - sleeping %d seconds (%s)",
                         plugin->oid, forks_retry, strerror (errno));
                       fork_sleep (forks_retry);
                       goto again;
                     }
                   else
                     {
-                      g_debug ("fork() failed too many times - aborting");
+                      g_warning ("fork() failed too many times - aborting");
                       goto host_died;
                     }
                 }

src/pluginlaunch.c

@@ -388,13 +388,20 @@ check_sysload ()
 }
 
 /**
+ * @brief Start a plugin.
+ *
+ * Check for free slots available in the process table. Set error with
+ * ERR_NO_FREE_SLOT if the process table is full. Set error with ERR_CANT_FORK
+ * if was not possible to fork() a new child.
+ *
  * @return PID of process that is connected to the plugin as returned by plugin
- *         classes pl_launch function (<=0 means there was a problem).
+ *         classes pl_launch function. Less than 0 means there was a problem,
+ *         but error param should be checked.
  */
 int
 plugin_launch (struct scan_globals *globals, struct scheduler_plugin *plugin,
                struct in6_addr *ip, GSList *vhosts, kb_t kb, kb_t main_kb,
-               nvti_t *nvti)
+               nvti_t *nvti, int *error)
 {
   int p;
 
@@ -403,12 +410,11 @@ plugin_launch (struct scan_globals *globals, struct scheduler_plugin *plugin,
   p = next_free_process (main_kb, plugin);
   if (p < 0)
     {
-      g_debug ("There is currently no free slot available for starting a new "
-               "plugin, probably because the parallel check is temporarily "
-               "disabled. Current parallel checks: %d. Old parallel checks: %d",
-               max_running_processes, old_max_running_processes);
-      usleep (250000);
-      return ERR_NO_FREE_SLOT;
+      g_warning ("%s. There is currently no free slot available for starting a "
+                 "new plugin.",
+                 __func__);
+      *error = ERR_NO_FREE_SLOT;
+      return -1;
     }
 
   processes[p].plugin = plugin;
@@ -420,8 +426,10 @@ plugin_launch (struct scan_globals *globals, struct scheduler_plugin *plugin,
   if (processes[p].pid > 0)
     num_running_processes++;
   else
-    processes[p].plugin->running_state = PLUGIN_STATUS_UNRUN;
-
+    {
+      processes[p].plugin->running_state = PLUGIN_STATUS_UNRUN;
+      *error = ERR_CANT_FORK;
+    }
   return processes[p].pid;
 }
 

src/pluginlaunch.h

@@ -30,7 +30,11 @@
 #include "pluginscheduler.h" /* for struct plugins_scheduler_t */
 
 /**
- * @brief Error for max. number of concurrent plugins per host reached.
+ * @brief Error for when it is not possible to fork a new plugin process.
+ */
+#define ERR_CANT_FORK -2
+/**
+ * @brief Error for when the process table is full
  */
 #define ERR_NO_FREE_SLOT -99
 
@@ -44,7 +48,7 @@ pluginlaunch_stop (void);
 
 int
 plugin_launch (struct scan_globals *, struct scheduler_plugin *,
-               struct in6_addr *, GSList *, kb_t, kb_t, nvti_t *);
+               struct in6_addr *, GSList *, kb_t, kb_t, nvti_t *, int *);
 
 void
 pluginlaunch_disable_parallel_checks (void);