dirmngr: Add a background task framework.

* dirmngr/workqueue.c: New.
* dirmngr/Makefile.am (dirmngr_SOURCES): Add new file.
* dirmngr/server.c (server_local_s): New field session_id.
(cmd_wkd_get): Add a task.
(task_check_wkd_support): New stub function.
(cmd_getinfo): New sub-commands "session_id" and "workqueue".
(start_command_handler): Add arg session_id and store it in
SERVER_LOCAL.
(dirmngr_status_helpf): New.
* dirmngr/dirmngr.h (wqtask_t): New type.
* dirmngr/dirmngr.c (main): Pass 0 as session_id to
start_command_handler.
(start_connection_thread): Introduce a session_id and pass it to
start_command_handler.  Run post session tasks.
(housekeeping_thread): Run global workqueue tasks.
--

Signed-off-by: Werner Koch <wk@gnupg.org>
(cherry picked from commit 96a4fbecd1acf946dcde20bef4752c539dae196b)

1 files changed, 214 insertions, 0 deletions

diff --git a/dirmngr/workqueue.c b/dirmngr/workqueue.c
new file mode 100644
index 000000000..2cb8573e8
--- /dev/null
+++ b/dirmngr/workqueue.c
@@ -0,0 +1,214 @@
+/* workqueue.c - Maintain a queue of background tasks
+ * Copyright (C) 2017 Werner Koch
+ *
+ * This file is part of GnuPG.
+ *
+ * GnuPG is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * GnuPG is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses/>.
+ *
+ * SPDX-License-Identifier: GPL-3.0+
+ */
+
+#include <config.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "dirmngr.h"
+
+
+/* An object for one item in the workqueue.  */
+struct wqitem_s
+{
+  struct wqitem_s *next;
+
+  /* This flag is set if the task requires network access.  */
+  unsigned int need_network:1;
+
+  /* The id of the session which created this task.  If this is 0 the
+   * task is not associated with a specific session.  */
+  unsigned int session_id;
+
+  /* The function to perform the backgrount task.  */
+  wqtask_t func;
+
+  /* A string with the string argument for that task.  */
+  char args[1];
+};
+typedef struct wqitem_s *wqitem_t;
+
+
+/* The workque is a simple linked list.  */
+static wqitem_t workqueue;
+
+
+/* Dump the queue using Assuan status comments.  */
+void
+workqueue_dump_queue (ctrl_t ctrl)
+{
+  wqitem_t saved_workqueue;
+  wqitem_t item;
+  unsigned int count;
+
+  /* Temporay detach the entiere workqueue so that other threads don't
+   * get into our way.  */
+  saved_workqueue = workqueue;
+  workqueue = NULL;
+
+  for (count=0, item = saved_workqueue; item; item = item->next)
+    count++;
+
+  dirmngr_status_helpf (ctrl, "wq: number of entries: %u", count);
+  for (item = saved_workqueue; item; item = item->next)
+    dirmngr_status_helpf (ctrl, "wq: sess=%u net=%d %s(\"%.100s%s\")",
+                          item->session_id, item->need_network,
+                          item->func? item->func (NULL, NULL): "nop",
+                          item->args, strlen (item->args) > 100? "[...]":"");
+
+  /* Restore then workqueue.  Actually we append the saved queue do a
+   * possibly updated workqueue.  */
+  if (!(item=workqueue))
+    workqueue = saved_workqueue;
+  else
+    {
+      while (item->next)
+        item = item->next;
+      item->next = saved_workqueue;
+    }
+}
+
+
+/* Append the task (FUNC,ARGS) to the work queue.  FUNC shall return
+ * its name when called with (NULL, NULL).  */
+gpg_error_t
+workqueue_add_task (wqtask_t func, const char *args, unsigned int session_id,
+                    int need_network)
+{
+  wqitem_t item, wi;
+
+  item = xtrycalloc (1, sizeof *item + strlen (args));
+  if (!item)
+    return gpg_error_from_syserror ();
+  strcpy (item->args, args);
+  item->func = func;
+  item->session_id = session_id;
+  item->need_network = !!need_network;
+
+  if (!(wi=workqueue))
+    workqueue = item;
+  else
+    {
+      while (wi->next)
+        wi = wi->next;
+      wi->next = item;
+    }
+  return 0;
+}
+
+
+/* Run the task described by ITEM.  ITEM must have been detached from
+ * the workqueue; its ownership is transferred to this fucntion.  */
+static void
+run_a_task (ctrl_t ctrl, wqitem_t item)
+{
+  log_assert (!item->next);
+
+  if (opt.verbose)
+    log_info ("session %u: running %s(\"%s%s\")\n",
+              item->session_id,
+              item->func? item->func (NULL, NULL): "nop",
+              item->args, strlen (item->args) > 100? "[...]":"");
+  if (item->func)
+    item->func (ctrl, item->args);
+
+  xfree (item);
+}
+
+
+/* Run tasks not associated with a session.  This is called from the
+ * ticker every few minutes.  If WITH_NETWORK is not set tasks which
+ * require the network are not run.  */
+void
+workqueue_run_global_tasks (ctrl_t ctrl, int with_network)
+{
+  wqitem_t item, prev;
+
+  with_network = !!with_network;
+
+  if (opt.verbose)
+    log_info ("running scheduled tasks%s\n", with_network?" (with network)":"");
+
+  for (;;)
+    {
+      prev = NULL;
+      for (item = workqueue; item; prev = item, item = item->next)
+        if (!item->session_id
+            && (!item->need_network || (item->need_network && with_network)))
+          break;
+      if (!item)
+        break;  /* No more tasks to run.  */
+
+      /* Detach that item from the workqueue.  */
+      if (!prev)
+        workqueue = item->next;
+      else
+        prev->next = item->next;
+      item->next = NULL;
+
+      /* Run the task.  */
+      run_a_task (ctrl, item);
+    }
+}
+
+
+/* Run tasks scheduled for running after a session.  Those tasks are
+ * identified by the SESSION_ID.  */
+void
+workqueue_run_post_session_tasks (unsigned int session_id)
+{
+  struct server_control_s ctrlbuf;
+  ctrl_t ctrl = NULL;
+  wqitem_t item, prev;
+
+  if (!session_id)
+    return;
+
+  for (;;)
+    {
+      prev = NULL;
+      for (item = workqueue; item; prev = item, item = item->next)
+        if (item->session_id == session_id)
+          break;
+      if (!item)
+        break;  /* No more tasks for this session.  */
+
+      /* Detach that item from the workqueue.  */
+      if (!prev)
+        workqueue = item->next;
+      else
+        prev->next = item->next;
+      item->next = NULL;
+
+      /* Create a CTRL object the first time we need it.  */
+      if (!ctrl)
+        {
+          memset (&ctrlbuf, 0, sizeof ctrlbuf);
+          ctrl = &ctrlbuf;
+          dirmngr_init_default_ctrl (ctrl);
+        }
+
+      /* Run the task.  */
+      run_a_task (ctrl, item);
+    }
+
+  dirmngr_deinit_default_ctrl (ctrl);
+}