How do captive portals benefit Google?
> Well, on Android 6 or higher, every time you switch networks, your phone tries to access the following URL:
> http://connectivitycheck.gstatic.com/generate_204
> As we can see, gstatic.com – Google’s servers. We might not want Google to know our new IP address or when we switched between networks. So… Why don’t we just self-host it? It’s pretty easy.
I don't know why this is such a big issue, given that they have your more or less exact location at all times, but changing it is so easy that, why not.
No, it's Google wanting Android users to be notified when they sign in to a wifi network that uses a captive portal, rather than having all network requests silently fail because they're being redirected.
Fixing the (generally terrible) user experience of captive portals is the primary goal of this feature. Any data collection is secondary.
This doesn't give Google any new information either.
ZMap is a fast single-packet network scanner optimized for Internet-wide network surveys. On a computer with a gigabit connection, ZMap can scan the entire public IPv4 address space on a single port in under 45 minutes. With a 10gigE connection and PF_RING, ZMap can scan the IPv4 address space in 5 minutes.