Chrome Version: Google Chrome 63.0.3239.7 (Official build) dev (64bit)
Chrome OS Version: 10032.4.0 (Official Build) dev-channel candy
Chrome OS Platform: Dell Chromebook 11 (model 2015, candy)
Network info: WPA2-PSK IPv6-only with NAT64/DNS64

Please specify Cr-* of the system to which this bug/feature applies (add
the label below).

Steps To Reproduce:
(1) Connect the device to the IPv6-only Wi-Fi network with NAT64/DNS64 
(2) Trigger check for system update either using UI or using the shell command: update_engine_client --update

Expected Result:

The update process should be started if there's new build available.

Actual Result:

Using GUI, you'll get (often false) information that Chrome OS is up to date.

Using shell, the updater prints an error:

chronos@localhost / $ update_engine_client --update
[1019/223350:INFO:update_engine_client.cc(486)] Forcing an update by setting app_version to ForcedUpdate.
[1019/223350:INFO:update_engine_client.cc(488)] Initiating update check and install.
[1019/223350:INFO:update_engine_client.cc(517)] Waiting for update to complete.
[1019/223401:ERROR:update_engine_client.cc(232)] Update failed, current operation is UPDATE_STATUS_IDLE, last error code is ErrorCode::kOmahaErrorInHTTPResponse(37)


How frequently does this problem reproduce? (Always, sometimes, hard to
reproduce?)

Reproducible: Always


What is the impact to the user, and is there a workaround? If so, what is
it?

The OS doesn't get updates unless user connects to a network with native IPv4.