[epiphany/wip/google-safe-browsing: 17/22] gsb-service: Handle back-off mode

[Gabriel Ivașcu <gabrielivascu src gnome org>]

commit a3c229d74ad91cbd8e5728f6bdacd8c598fec29d
Author: Gabriel Ivascu <gabrielivascu gnome org>
Date:   Tue Sep 19 15:31:02 2017 +0300

    gsb-service: Handle back-off mode

 lib/safe-browsing/ephy-gsb-service.c |   58 +++++++++++++++++++++++++++++++--
 1 files changed, 54 insertions(+), 4 deletions(-)
---
diff --git a/lib/safe-browsing/ephy-gsb-service.c b/lib/safe-browsing/ephy-gsb-service.c
index 6525fe4..4d951cd 100644
--- a/lib/safe-browsing/ephy-gsb-service.c
+++ b/lib/safe-browsing/ephy-gsb-service.c
@@ -44,6 +44,8 @@ struct _EphyGSBService {
   guint           source_id;
 
   gint64          next_full_hashes_request_time;
+  gint64          back_off_mode_exit_time;
+  gint64          num_fails;
 
   SoupSession    *session;
 };
@@ -137,6 +139,38 @@ json_object_has_non_null_array_member (JsonObject *object,
          json_object_get_array_member (object, member) != NULL;
 }
 
+/*
+ * https://developers.google.com/safe-browsing/v4/request-frequency#back-off-mode
+ */
+static inline void
+ephy_gsb_service_update_back_off_mode (EphyGSBService *self)
+{
+  gint64 duration;
+
+  g_assert (EPHY_IS_GSB_SERVICE (self));
+
+  duration = (1 << self->num_fails++) * 15 * 60 * (g_random_double () + 1);
+  self->back_off_mode_exit_time = CURRENT_TIME + MIN (duration, 24 * 60 * 60);
+
+  LOG ("Set back-off mode for %ld seconds", duration);
+}
+
+static inline void
+ephy_gsb_service_reset_back_off_mode (EphyGSBService *self)
+{
+  g_assert (EPHY_IS_GSB_SERVICE (self));
+
+  self->num_fails = self->back_off_mode_exit_time = 0;
+}
+
+static inline gboolean
+ephy_gsb_service_is_back_off_mode (EphyGSBService *self)
+{
+  g_assert (EPHY_IS_GSB_SERVICE (self));
+
+  return self->num_fails > 0 && CURRENT_TIME < self->back_off_mode_exit_time;
+}
+
 static void
 ephy_gsb_service_schedule_update (EphyGSBService *self,
                                   gint64          interval)
@@ -189,12 +223,17 @@ ephy_gsb_service_update_thread (GTask          *task,
   json_object_unref (body_obj);
   json_node_unref (body_node);
 
+  /* Handle unsuccessful responses. */
   if (msg->status_code != 200) {
-    LOG ("Cannot update GSB threat lists. Server responded: %u, %s",
-         msg->status_code, msg->response_body->data);
+    LOG ("Cannot update threat lists, got: %u, %s", msg->status_code, msg->response_body->data);
+    ephy_gsb_service_update_back_off_mode (self);
+    next_update_time = self->back_off_mode_exit_time;
     goto out;
   }
 
+  /* Successful response, reset back-off mode. */
+  ephy_gsb_service_reset_back_off_mode (self);
+
   body_node = json_from_string (msg->response_body->data, NULL);
   body_obj = json_node_get_object (body_node);
   responses = json_object_get_array_member (body_obj, "listUpdateResponses");
@@ -465,12 +504,16 @@ ephy_gsb_service_find_full_hashes_cb (SoupSession *session,
   const char *duration_str;
   double duration;
 
+  /* Handle unsuccessful responses. */
   if (msg->status_code != 200) {
-    LOG ("Cannot update full hashes. Server responded: %u, %s",
-         msg->status_code, msg->response_body->data);
+    LOG ("Cannot update full hashes, got: %u, %s", msg->status_code, msg->response_body->data);
+    ephy_gsb_service_update_back_off_mode (self);
     goto out;
   }
 
+  /* Successful response, reset back-off mode. */
+  ephy_gsb_service_reset_back_off_mode (self);
+
   body_node = json_from_string (msg->response_body->data, NULL);
   body_obj = json_node_get_object (body_node);
   matches = json_object_get_array_member (body_obj, "matches");
@@ -573,6 +616,13 @@ ephy_gsb_service_find_full_hashes (EphyGSBService                  *self,
     return;
   }
 
+   if (ephy_gsb_service_is_back_off_mode (self)) {
+    LOG ("Cannot send fullHashes:find request. Back-off mode is enabled for %ld seconds",
+         self->back_off_mode_exit_time - CURRENT_TIME);
+    callback (threats, user_data);
+    return;
+   }
+
   threat_lists = ephy_gsb_storage_get_threat_lists (self->storage);
   if (!threat_lists) {
     callback (threats, user_data);