autoupdater: add download.d and abort.d directories

All executables in download.d are executed before after the update manifest
has been verified, but before the image is downloaded. This can be used to
stop non-essential services to free RAM.

abort.d is run when the download has failed and should revert the actions
of download.d.

admin/autoupdater/files/usr/lib/autoupdater/abort.d/README

@@ -0,0 +1,6 @@
+Executable files in abort.d will be executed if downloading the upgrade
+image has failed and should revert the actions from download.d.
+
+We can't really do anything when the download has succeeded, but the
+flashing has failed, as the autoupdater process will have been replaced by
+sysupgrade by then.

admin/autoupdater/files/usr/lib/autoupdater/download.d/95drop_caches

@@ -0,0 +1,4 @@
+#!/bin/sh
+
+sync
+sysctl -w vm.drop_caches=3

admin/autoupdater/files/usr/lib/autoupdater/download.d/README

@@ -0,0 +1,2 @@
+Executable files in download.d will be executed after the update manifest
+has been verified, but before the actual image is downloaded.

admin/autoupdater/files/usr/lib/lua/autoupdater/util.lua

@@ -1,9 +1,9 @@
-local io = io
-local math = math
 local nixio = require 'nixio'
+local fs = require 'nixio.fs'
+local util = require 'nixio.util'
 
 
-module 'autoupdater.util'
+module('autoupdater.util', package.seeall)
 
 
 -- Executes a command in the background, without parsing the command through a shell (in contrast to os.execute)
@@ -42,6 +42,39 @@ function popen(...)
 end
 
 
+-- Executes all executable files in a directory
+function run_dir(dir)
+  local function is_ok(entry)
+    if entry:sub(1, 1) == '.' then
+      return false
+    end
+
+    local file = dir .. '/' .. entry
+    if fs.stat(file, 'type') ~= 'reg' then
+      return false
+    end
+    if not fs.access(file, 'x') then
+      return false
+    end
+
+    return true
+  end
+
+  local files = util.consume(fs.dir(dir))
+  if not files then
+    return
+  end
+
+  table.sort(files)
+
+  for _, entry in ipairs(files) do
+    if is_ok(entry) then
+      exec(dir .. '/' .. entry)
+    end
+  end
+end
+
+
 -- Seeds Lua's random generator from /dev/urandom
 function randomseed()
   local f = io.open('/dev/urandom', 'r')

admin/autoupdater/files/usr/sbin/autoupdater

@@ -241,6 +241,10 @@ end
 
 -- Tries to perform an update from a given mirror
 local function autoupdate(mirror)
+  local download_d_dir = '/usr/lib/autoupdater/download.d'
+  local abort_d_dir = '/usr/lib/autoupdater/abort.d'
+
+
   local manifest = read_manifest(mirror)
   if not manifest then
     return false
@@ -259,13 +263,12 @@ local function autoupdate(mirror)
     return true
   end
 
-
-  autoupdater_util.exec('sync')
-  autoupdater_util.exec('sysctl', '-w', 'vm.drop_caches=3')
+  autoupdater_util.run_dir(download_d_dir)
   collectgarbage()
 
   local image = os.tmpname()
   if not fetch_firmware(mirror, manifest.filename, image) then
+    autoupdater_util.run_dir(abort_d_dir)
     return false
   end
 
@@ -275,6 +278,7 @@ local function autoupdate(mirror)
   if checksum ~= manifest.checksum then
     io.stderr:write('Invalid image checksum!\n')
     os.remove(image)
+    autoupdater_util.run_dir(abort_d_dir)
     return false
   end
 
@@ -294,6 +298,7 @@ local function autoupdate(mirror)
   -- We output the error message through stdout as stderr isn't available anymore
   io.write('Failed to call sysupgrade?\n')
   os.remove(image)
+  autoupdater_util.run_dir(abort_d_dir)
   os.exit(1)
 end