AU: Don't request data ranges beyond the end of the payload.

update_attempter.cc

 // Copyright (c) 2010 The Chromium OS Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "update_engine/update_attempter.h"
 
 // From 'man clock_gettime': feature test macro: _POSIX_C_SOURCE >= 199309L
 #ifndef _POSIX_C_SOURCE
 #define _POSIX_C_SOURCE 199309L
 #endif  // _POSIX_C_SOURCE
@@ skipping 517 matching lines @@
   }
   prefs_->SetInt64(kPrefsDeltaUpdateFailures, ++delta_failures);
 }
 
 void UpdateAttempter::SetupDownload() {
   MultiHttpFetcher<LibcurlHttpFetcher>* fetcher =
       dynamic_cast<MultiHttpFetcher<LibcurlHttpFetcher>*>(
           download_action_->http_fetcher());
   MultiHttpFetcher<LibcurlHttpFetcher>::RangesVect ranges;
   if (response_handler_action_->install_plan().is_resume) {
+    // Resuming an update so fetch the update manifest metadata first.
     int64_t manifest_metadata_size = 0;
     prefs_->GetInt64(kPrefsManifestMetadataSize, &manifest_metadata_size);
+    ranges.push_back(make_pair(0, manifest_metadata_size));
+    // If there're remaining unprocessed data blobs, fetch them. Be careful not
+    // to request data beyond the end of the payload to avoid 416 HTTP response
+    // error codes.
     int64_t next_data_offset = 0;
     prefs_->GetInt64(kPrefsUpdateStateNextDataOffset, &next_data_offset);
-    ranges.push_back(make_pair(0, manifest_metadata_size));
-    ranges.push_back(make_pair(manifest_metadata_size + next_data_offset, -1));
+    uint64_t resume_offset = manifest_metadata_size + next_data_offset;
+    if (resume_offset < response_handler_action_->install_plan().size) {
+      ranges.push_back(make_pair(resume_offset, -1));
+    }
   } else {
     ranges.push_back(make_pair(0, -1));
   }
   fetcher->set_ranges(ranges);
 }
 
 }  // namespace chromeos_update_engine