There is a DHCP option for a captive portal URL. It isn't very well supported an...

gavinsyancey · 2024-10-23T06:29:37 1729664977

Apparently, there's a newer one that is supported by Android 11+, iOS 14+, and macOS Big Sur, at least

https://www.rfc-editor.org/rfc/rfc8910.html https://www.rfc-editor.org/rfc/rfc8908.html

https://developer.android.com/about/versions/11/features/cap... https://developer.apple.com/news/?id=q78sq5rv

0xbadcafebee · 2024-10-23T14:08:36 1729692516

If they got the top 5 wifi router vendors to support it, for sure you'd see other clients support it too, because the whole point of captive portal support in browsers is to react to what those routers are doing for captive portaling.

Since those vendors largely use open source tools, if you patched open source DHCP servers with that option, it would get adopted quicker by them.

- KEA DHCPD supports it as option 114: https://gitlab.isc.org/isc-projects/kea/-/blob/master/src/li...

- ISC DHCPD is officially ended (whoa!), but it looks like it supports option 114: https://gitlab.isc.org/isc-projects/dhcp/-/blob/master/commo...

- Dnsmasq author says they added the option (https://www.mail-archive.com/dnsmasq-discuss@lists.thekelley...) but I don't see it in their latest release

- Udhcpd doesn't seem to support it, so somebody could send them a patch, looks trivial to add