Fix #3603: Unable to view images on Hijiribe/Sonohara when Danbooru domain is blocked.

app/controllers/application_controller.rb

@@ -172,6 +172,7 @@ class ApplicationController < ActionController::Base
   def reset_current_user
     CurrentUser.user = nil
     CurrentUser.ip_addr = nil
+    CurrentUser.root_url = root_url
   end
 
   def set_started_at_session

app/logical/current_user.rb

@@ -48,6 +48,14 @@ class CurrentUser
     Thread.current[:current_ip_addr]
   end
 
+  def self.root_url
+    Thread.current[:current_root_url] || "http://#{Danbooru.config.hostname}/"
+  end
+
+  def self.root_url=(root_url)
+    Thread.current[:current_root_url] = root_url
+  end
+
   def self.id
     if user.nil?
       nil

app/logical/storage_manager.rb

@@ -14,7 +14,7 @@ class StorageManager
   end
 
   def default_base_url
-    Rails.application.routes.url_helpers.root_url + "data"
+    CurrentUser.root_url + "data"
   end
 
   # Store the given file at the given path. If a file already exists at that