packages/NetworkStack/res/values/config.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <!--
    OEMs that wish to change the below settings must do so via a runtime resource overlay package
    and *NOT* by changing this file. This file is part of the NetworkStack mainline module.
    The overlays must apply to the config_* values, not the default_* values. The default_*
    values are meant to be the default when no other configuration is specified.
    -->

    <!-- HTTP URL for network validation, to use for detecting captive portals. -->
    <string name="default_captive_portal_http_url" translatable="false">http://connectivitycheck.gstatic.com/generate_204</string>

    <!-- HTTPS URL for network validation, to use for confirming internet connectivity. -->
    <string name="default_captive_portal_https_url" translatable="false">https://www.google.com/generate_204</string>

    <!-- List of fallback URLs to use for detecting captive portals. -->
    <string-array name="default_captive_portal_fallback_urls" translatable="false">
        <item>http://www.google.com/gen_204</item>
        <item>http://play.googleapis.com/generate_204</item>
    </string-array>

    <!-- List of fallback probe specs to use for detecting captive portals.
         This is an alternative to fallback URLs that provides more flexibility on detection rules.
         Empty, so unused by default. -->
    <string-array name="default_captive_portal_fallback_probe_specs" translatable="false">
    </string-array>

    <!-- Configuration hooks for the above settings.
         Empty by default but may be overridden by RROs. -->
    <!--suppress CheckTagEmptyBody: overlayable resource to use as configuration hook -->
    <string name="config_captive_portal_http_url" translatable="false"></string>
    <!--suppress CheckTagEmptyBody: overlayable resource to use as configuration hook -->
    <string name="config_captive_portal_https_url" translatable="false"></string>
    <string-array name="config_captive_portal_fallback_urls" translatable="false">
    </string-array>
    <string-array name="config_captive_portal_fallback_probe_specs" translatable="false">
    </string-array>
</resources>