Code to manage publish/subscribe setup via subsystem interface.

This commit has the necessary logic to run the publish/subscribe
system from the mainloop, and to initialize it on startup and tear
it down later.

3 files changed, 174 insertions, 0 deletions

diff --git a/src/core/include.am b/src/core/include.am
index ae47c75e09..3a0e907edb 100644
--- a/src/core/include.am
+++ b/src/core/include.am
@@ -22,6 +22,7 @@ LIBTOR_APP_A_SOURCES = 				\
 	src/core/mainloop/connection.c		\
 	src/core/mainloop/cpuworker.c		\
 	src/core/mainloop/mainloop.c		\
+	src/core/mainloop/mainloop_pubsub.c	\
 	src/core/mainloop/netstatus.c		\
 	src/core/mainloop/periodic.c		\
 	src/core/or/address_set.c		\
@@ -213,6 +214,7 @@ noinst_HEADERS +=					\
 	src/core/mainloop/connection.h			\
 	src/core/mainloop/cpuworker.h			\
 	src/core/mainloop/mainloop.h			\
+	src/core/mainloop/mainloop_pubsub.h		\
 	src/core/mainloop/netstatus.h			\
 	src/core/mainloop/periodic.h			\
 	src/core/or/addr_policy_st.h			\
diff --git a/src/core/mainloop/mainloop_pubsub.c b/src/core/mainloop/mainloop_pubsub.c
new file mode 100644
index 0000000000..ab3614ae00
--- /dev/null
+++ b/src/core/mainloop/mainloop_pubsub.c
@@ -0,0 +1,149 @@
+/* Copyright (c) 2001, Matej Pfajfar.
+ * Copyright (c) 2001-2004, Roger Dingledine.
+ * Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.
+ * Copyright (c) 2007-2018, The Tor Project, Inc. */
+/* See LICENSE for licensing information */
+
+#include "orconfig.h"
+
+#include "src/core/or/or.h"
+#include "src/core/mainloop/mainloop.h"
+#include "src/core/mainloop/mainloop_pubsub.h"
+
+#include "lib/container/smartlist.h"
+#include "lib/dispatch/dispatch.h"
+#include "lib/dispatch/dispatch_naming.h"
+#include "lib/evloop/compat_libevent.h"
+#include "lib/pubsub/pubsub.h"
+#include "lib/pubsub/pubsub_build.h"
+
+/**
+ * Dispatcher to use for delivering messages.
+ **/
+static dispatch_t *the_dispatcher = NULL;
+static pubsub_items_t *the_pubsub_items = NULL;
+/**
+ * A list of mainloop_event_t, indexed by channel ID, to flush the messages
+ * on a channel.
+ **/
+static smartlist_t *alert_events = NULL;
+
+/**
+ * Mainloop event callback: flush all the messages in a channel.
+ *
+ * The channel is encoded as a pointer, and passed via arg.
+ **/
+static void
+flush_channel_event(mainloop_event_t *ev, void *arg)
+{
+  (void)ev;
+  if (!the_dispatcher)
+    return;
+
+  channel_id_t chan = (channel_id_t)(uintptr_t)(arg);
+  dispatch_flush(the_dispatcher, chan, INT_MAX);
+}
+
+int
+tor_mainloop_connect_pubsub(struct pubsub_builder_t *builder)
+{
+  int rv = -1;
+  tor_mainloop_disconnect_pubsub();
+
+  the_dispatcher = pubsub_builder_finalize(builder, &the_pubsub_items);
+  if (! the_dispatcher)
+    goto err;
+
+  const size_t num_channels = get_num_channel_ids();
+  alert_events = smartlist_new();
+  for (size_t i = 0; i < num_channels; ++i) {
+    smartlist_add(alert_events,
+                  mainloop_event_postloop_new(flush_channel_event,
+                                              (void*)(uintptr_t)(i)));
+  }
+
+  rv = 0;
+ err:
+  tor_mainloop_disconnect_pubsub();
+  return rv;
+}
+
+/**
+ * Dispatch alertfn callback: do nothing. Implements DELIV_NEVER.
+ **/
+static void
+alertfn_never(dispatch_t *d, channel_id_t chan, void *arg)
+{
+  (void)d;
+  (void)chan;
+  (void)arg;
+}
+
+/**
+ * Dispatch alertfn callback: activate a mainloop event. Implements
+ * DELIV_PROMPT.
+ **/
+static void
+alertfn_prompt(dispatch_t *d, channel_id_t chan, void *arg)
+{
+  (void)d;
+  (void)chan;
+  mainloop_event_t *event = arg;
+  mainloop_event_activate(event);
+}
+
+/**
+ * Dispatch alertfn callback: flush all messages right now. Implements
+ * DELIV_IMMEDIATE.
+ **/
+static void
+alertfn_immediate(dispatch_t *d, channel_id_t chan, void *arg)
+{
+  (void) arg;
+  dispatch_flush(d, chan, INT_MAX);
+}
+
+/**
+ * Set the strategy to be used for delivering messages on the named channel.
+ **/
+int
+tor_mainloop_set_delivery_strategy(const char *msg_channel_name,
+                                   deliv_strategy_t strategy)
+{
+  channel_id_t chan = get_channel_id(msg_channel_name);
+  if (BUG(chan == ERROR_ID) ||
+      BUG(chan >= smartlist_len(alert_events)))
+    return -1;
+
+  switch (strategy) {
+    case DELIV_NEVER:
+      dispatch_set_alert_fn(the_dispatcher, chan, alertfn_never, NULL);
+      break;
+    case DELIV_PROMPT:
+      dispatch_set_alert_fn(the_dispatcher, chan, alertfn_prompt,
+                            smartlist_get(alert_events, chan));
+      break;
+    case DELIV_IMMEDIATE:
+      dispatch_set_alert_fn(the_dispatcher, chan, alertfn_immediate, NULL);
+      break;
+  }
+  return 0;
+}
+
+/**
+ * Remove all pubsub dispatchers and events from the mainloop.
+ **/
+void
+tor_mainloop_disconnect_pubsub(void)
+{
+  if (the_pubsub_items) {
+    pubsub_items_clear_bindings(the_pubsub_items);
+    pubsub_items_free(the_pubsub_items);
+  }
+  if (alert_events) {
+    SMARTLIST_FOREACH(alert_events, mainloop_event_t *, ev,
+                      mainloop_event_free(ev));
+    smartlist_free(alert_events);
+  }
+  dispatch_free(the_dispatcher);
+}
diff --git a/src/core/mainloop/mainloop_pubsub.h b/src/core/mainloop/mainloop_pubsub.h
new file mode 100644
index 0000000000..6eff778420
--- /dev/null
+++ b/src/core/mainloop/mainloop_pubsub.h
@@ -0,0 +1,23 @@
+/* Copyright (c) 2001, Matej Pfajfar.
+ * Copyright (c) 2001-2004, Roger Dingledine.
+ * Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.
+ * Copyright (c) 2007-2018, The Tor Project, Inc. */
+/* See LICENSE for licensing information */
+
+#ifndef TOR_MAINLOOP_PUBSUB_H
+#define TOR_MAINLOOP_PUBSUB_H
+
+struct pubsub_builder_t;
+
+typedef enum {
+   DELIV_NEVER=0,
+   DELIV_PROMPT,
+   DELIV_IMMEDIATE,
+} deliv_strategy_t;
+
+int tor_mainloop_connect_pubsub(struct pubsub_builder_t *builder);
+int tor_mainloop_set_delivery_strategy(const char *msg_channel_name,
+                                        deliv_strategy_t strategy);
+void tor_mainloop_disconnect_pubsub(void);
+
+#endif