Proxy Automatic Configuration to WAN gateway?

Installing and Using OpenWrt
1

Short version:
How can I configure DNSMasq to send option 252 PAC (Proxy automatic configuration) as whatever the current default WAN gateway is?

Long version:
Internet connection is via Android device with ethernet tethering.
Android tethering subnet and IP changes every reboot.
Android device is running EveryProxy for HTTP/S, SOCKS, and PAC
OpenWRT router (r28556) running DNSMasq needs to send DHCP Option 252 (Proxy automatic configuration) to LAN clients as the current IP of the android device which is the WAN default Gateway issued to OpenWRT via DHCP by the android device.

It doesn't look like I can do this from LUCI, and am fine editing /etc/config/dhcp or /etc/dnsmasq.conf whichever is correct, but how do I deal with this dynamic upstream IP as an option setting?

Is there some %default_gateway% variable or something to point to the upstream WAN gateway?

Don't think 0.0.0.0 is going to work. Can't use DNS name because it doesn't appear the android device is announcing a name.

Any ideas, or other workarounds?

2

Install redsocks on the router ?

3

You should also add http://wpad.lan/proxy.pac script. In the 90% SSL world it will not be very efficient.

4

This would likely have the same issue, defining the upstream proxy dynamically???

5

Same challenge though. How do I dynamically change that script to point to the router's default gateway?

6

you can always script it ?

7

How would I do that? That is the basic question? How to dynamically change option 252 based on the router's default gateway that is subject to change due to subnet and gateway change of WAN link? DHCP updates subnet and gateway, but how to then change PAC to point to that new upstream IP?

8

https://openwrt.org/docs/guide-user/base-system/hotplug

https://openwrt.org/docs/guide-user/base-system/dhcp_configuration#dhcp_options

I would still use redsocks.